Virtual experiments: a new approach for improving process conceptualization in hillslope hydrology

NASA Astrophysics Data System (ADS)

Weiler, Markus; McDonnell, Jeff

2004-01-01

We present an approach for process conceptualization in hillslope hydrology. We develop and implement a series of virtual experiments, whereby the interaction between water flow pathways, source and mixing at the hillslope scale is examined within a virtual experiment framework. We define these virtual experiments as 'numerical experiments with a model driven by collective field intelligence'. The virtual experiments explore the first-order controls in hillslope hydrology, where the experimentalist and modeler work together to cooperatively develop and analyze the results. Our hillslope model for the virtual experiments (HillVi) in this paper is based on conceptualizing the water balance within the saturated and unsaturated zone in relation to soil physical properties in a spatially explicit manner at the hillslope scale. We argue that a virtual experiment model needs to be able to capture all major controls on subsurface flow processes that the experimentalist might deem important, while at the same time being simple with few 'tunable parameters'. This combination makes the approach, and the dialog between experimentalist and modeler, a useful hypothesis testing tool. HillVi simulates mass flux for different initial conditions under the same flow conditions. We analyze our results in terms of an artificial line source and isotopic hydrograph separation of water and subsurface flow. Our results for this first set of virtual experiments showed how drainable porosity and soil depth variability exert a first order control on flow and transport at the hillslope scale. We found that high drainable porosity soils resulted in a restricted water table rise, resulting in more pronounced channeling of lateral subsurface flow along the soil-bedrock interface. This in turn resulted in a more anastomosing network of tracer movement across the slope. The virtual isotope hydrograph separation showed higher proportions of event water with increasing drainable porosity. When combined with previous experimental findings and conceptualizations, virtual experiments can be an effective way to isolate certain controls and examine their influence over a range of rainfall and antecedent wetness conditions.

Controlled laboratory experiments and modeling of vegetative filter strips with shallow water tables

NASA Astrophysics Data System (ADS)

Fox, Garey A.; Muñoz-Carpena, Rafael; Purvis, Rebecca A.

2018-01-01

Natural or planted vegetation at the edge of fields or adjacent to streams, also known as vegetative filter strips (VFS), are commonly used as an environmental mitigation practice for runoff pollution and agrochemical spray drift. The VFS position in lowlands near water bodies often implies the presence of a seasonal shallow water table (WT). In spite of its potential importance, there is limited experimental work that systematically studies the effect of shallow WTs on VFS efficacy. Previous research recently coupled a new physically based algorithm describing infiltration into soils bounded by a water table into the VFS numerical overland flow and transport model, VFSMOD, to simulate VFS dynamics under shallow WT conditions. In this study, we tested the performance of the model against laboratory mesoscale data under controlled conditions. A laboratory soil box (1.0 m wide, 2.0 m long, and 0.7 m deep) was used to simulate a VFS and quantify the influence of shallow WTs on runoff. Experiments included planted Bermuda grass on repacked silt loam and sandy loam soils. A series of experiments were performed including a free drainage case (no WT) and a static shallow water table (0.3-0.4 m below ground surface). For each soil type, this research first calibrated VFSMOD to the observed outflow hydrograph for the free drainage experiments to parameterize the soil hydraulic and vegetation parameters, and then evaluated the model based on outflow hydrographs for the shallow WT experiments. This research used several statistical metrics and a new approach based on hypothesis testing of the Nash-Sutcliffe model efficiency coefficient (NSE) to evaluate model performance. The new VFSMOD routines successfully simulated the outflow hydrographs under both free drainage and shallow WT conditions. Statistical metrics considered the model performance valid with greater than 99.5% probability across all scenarios. This research also simulated the shallow water table experiments with both free drainage and various water table depths to quantify the effect of assuming the former boundary condition. For these two soil types, shallow WTs within 1.0-1.2 m below the soil surface influenced infiltration. Existing models will suggest a more protective vegetative filter strip than what actually exists if shallow water table conditions are not considered.

Combining Experiments and Simulation of Gas Absorption for Teaching Mass Transfer Fundamentals: Removing CO2 from Air Using Water and NaOH

ERIC Educational Resources Information Center

Clark, William M.; Jackson, Yaminah Z.; Morin, Michael T.; Ferraro, Giacomo P.

2011-01-01

Laboratory experiments and computer models for studying the mass transfer process of removing CO2 from air using water or dilute NaOH solution as absorbent are presented. Models tie experiment to theory and give a visual representation of concentration profiles and also illustrate the two-film theory and the relative importance of various…

The landscape model: A model for exploring trade-offs between agricultural production and the environment.

PubMed

Coleman, Kevin; Muhammed, Shibu E; Milne, Alice E; Todman, Lindsay C; Dailey, A Gordon; Glendining, Margaret J; Whitmore, Andrew P

2017-12-31

We describe a model framework that simulates spatial and temporal interactions in agricultural landscapes and that can be used to explore trade-offs between production and environment so helping to determine solutions to the problems of sustainable food production. Here we focus on models of agricultural production, water movement and nutrient flow in a landscape. We validate these models against data from two long-term experiments, (the first a continuous wheat experiment and the other a permanent grass-land experiment) and an experiment where water and nutrient flow are measured from isolated catchments. The model simulated wheat yield (RMSE 20.3-28.6%), grain N (RMSE 21.3-42.5%) and P (RMSE 20.2-29% excluding the nil N plots), and total soil organic carbon particularly well (RMSE3.1-13.8%), the simulations of water flow were also reasonable (RMSE 180.36 and 226.02%). We illustrate the use of our model framework to explore trade-offs between production and nutrient losses. Copyright © 2017 Rothamsted Research. Published by Elsevier B.V. All rights reserved.

Free energy models for ice VII and liquid water derived from pressure, entropy, and heat capacity relations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Myint, Philip C.; Benedict, Lorin X.; Belof, Jonathan L.

Here, we present equations of state relevant to conditions encountered in ramp and multiple-shock compression experiments of water. These experiments compress water from ambient conditions to pressures as high as about 14 GPa and temperatures of up to several hundreds of Kelvin. Water may freeze into ice VII during this process. Although there are several studies on the thermodynamic properties of ice VII, an accurate and analytic free energy model from which all other properties may be derived in a thermodynamically consistent manner has not been previously determined. We have developed such a free energy model for ice VII thatmore » is calibrated with pressure-volume-temperature measurements and melt curve data. Furthermore, we show that liquid water in the pressure and temperature range of interest is well-represented by a simple Mie-Grüneisen equation of state. Our liquid water and ice VII equations of state are validated by comparing to sound speed and Hugoniot data. Although they are targeted towards ramp and multiple-shock compression experiments, we demonstrate that our equations of state also behave reasonably well at pressures and temperatures that lie somewhat beyond those found in the experiments.« less

Free energy models for ice VII and liquid water derived from pressure, entropy, and heat capacity relations

DOE PAGES

Myint, Philip C.; Benedict, Lorin X.; Belof, Jonathan L.

2017-08-28

Here, we present equations of state relevant to conditions encountered in ramp and multiple-shock compression experiments of water. These experiments compress water from ambient conditions to pressures as high as about 14 GPa and temperatures of up to several hundreds of Kelvin. Water may freeze into ice VII during this process. Although there are several studies on the thermodynamic properties of ice VII, an accurate and analytic free energy model from which all other properties may be derived in a thermodynamically consistent manner has not been previously determined. We have developed such a free energy model for ice VII thatmore » is calibrated with pressure-volume-temperature measurements and melt curve data. Furthermore, we show that liquid water in the pressure and temperature range of interest is well-represented by a simple Mie-Grüneisen equation of state. Our liquid water and ice VII equations of state are validated by comparing to sound speed and Hugoniot data. Although they are targeted towards ramp and multiple-shock compression experiments, we demonstrate that our equations of state also behave reasonably well at pressures and temperatures that lie somewhat beyond those found in the experiments.« less

Marine Radioactivity Studies in the Suez Canal, Part II: Field Experiments and a Modelling Study of Dispersion

NASA Astrophysics Data System (ADS)

Abril, J. M.; Abdel-Aal, M. M.; Al-Gamal, S. A.; Abdel-Hay, F. A.; Zahar, H. M.

2000-04-01

In this paper we take advantage of the two field tracing experiments carried out under the IAEA project EGY/07/002, to develop a modelling study on the dispersion of radioactive pollution in the Suez Canal. The experiments were accomplished by using rhodamine B as a tracer, and water samples were measured by luminescence spectrometry. The presence of natural luminescent particles in the canal waters limited the use of some field data. During experiments, water levels, velocities, wind and other physical parameters were recorded to supply appropriate information for the modelling work. From this data set, the hydrodynamics of the studied area has been reasonably described. We apply a 1-D-Gaussian and 2-D modelling approaches to predict the position and the spatial shape of the plume. The use of different formulations for dispersion coefficients is studied. These dispersion coefficients are then applied in a 2-D-hydrodynamic and dispersion model for the Bitter Lake to investigate different scenarios of accidental discharges.

Experiment and mathematical model for the heat transfer in water around 4 °C

NASA Astrophysics Data System (ADS)

Ogawa, Naohisa; Kaneko, Fumitoshi

2017-03-01

Water, which is the habitat for a variety of living creatures, has a maximum density at 4.0 °C. This crucial property is considered to play a very important role in the biology of a lake and also has a close relationship with the areas of environmentology and geoscience. It would be desirable for students to confirm this important property of water themselves by carrying out simple experiments. However, it is not easy to detect the maximum density at 4.0 °C because the temperature dependence of the water density is very small close to its freezing point. For example, the density of water is 0.999 975 g cm-3 at 4.0 °C and 0.999 850 g cm-3 at 0.1 °C. The aim in this manuscript is to demonstrate a simple experiment to detect 4.0 °C as the temperature of maximum density, in which the time dependence of the water temperature is measured at several different depths by chilling the water surface. This is a simple experiment that can also be performed by high school students. We also present a mathematical model that can explain the results of this experiment.

Characteristics of the Nordic Seas overflows in a set of Norwegian Earth System Model experiments

NASA Astrophysics Data System (ADS)

Guo, Chuncheng; Ilicak, Mehmet; Bentsen, Mats; Fer, Ilker

2016-08-01

Global ocean models with an isopycnic vertical coordinate are advantageous in representing overflows, as they do not suffer from topography-induced spurious numerical mixing commonly seen in geopotential coordinate models. In this paper, we present a quantitative diagnosis of the Nordic Seas overflows in four configurations of the Norwegian Earth System Model (NorESM) family that features an isopycnic ocean model. For intercomparison, two coupled ocean-sea ice and two fully coupled (atmosphere-land-ocean-sea ice) experiments are considered. Each pair consists of a (non-eddying) 1° and a (eddy-permitting) 1/4° horizontal resolution ocean model. In all experiments, overflow waters remain dense and descend to the deep basins, entraining ambient water en route. Results from the 1/4° pair show similar behavior in the overflows, whereas the 1° pair show distinct differences, including temperature/salinity properties, volume transport (Q), and large scale features such as the strength of the Atlantic Meridional Overturning Circulation (AMOC). The volume transport of the overflows and degree of entrainment are underestimated in the 1° experiments, whereas in the 1/4° experiments, there is a two-fold downstream increase in Q, which matches observations well. In contrast to the 1/4° experiments, the coarse 1° experiments do not capture the inclined isopycnals of the overflows or the western boundary current off the Flemish Cap. In all experiments, the pathway of the Iceland-Scotland Overflow Water is misrepresented: a major fraction of the overflow proceeds southward into the West European Basin, instead of turning westward into the Irminger Sea. This discrepancy is attributed to excessive production of Labrador Sea Water in the model. The mean state and variability of the Nordic Seas overflows have significant consequences on the response of the AMOC, hence their correct representations are of vital importance in global ocean and climate modelling.

Do initial conditions matter? A comparison of model climatologies generated from different initial states

NASA Technical Reports Server (NTRS)

Spar, J.; Cohen, C.; Wu, P.

1981-01-01

A coarse mesh (8 by 10) 7 layer global climate model was used to compute 15 months of meteorological history in two perpetual January experiments on a water planet (without continents) with a zonally symmetric climatological January sea surface temperature field. In the first of the two water planet experiments the initial atmospheric state was a set of zonal mean values of specific humidity, temperature, and wind at each latitude. In the second experiment the model was initialized with globally uniform mean values of specific humidity and temperature on each sigma level surface, constant surface pressure (1010 mb), and zero wind everywhere. A comparison was made of the mean January climatic states generated by the two water planet experiments. The first two months of each 15 January run were discarded, and 13 month averages were computed from months 3 through 15.

Electrostatic and induction effects in the solubility of water in alkanes

NASA Astrophysics Data System (ADS)

Asthagiri, D.; Valiya Parambathu, Arjun; Ballal, Deepti; Chapman, Walter G.

2017-08-01

Experiments show that at 298 K and 1 atm pressure, the transfer free energy, μex, of water from its vapor to liquid normal alkanes CnH2n+2 (n =5 …12 ) is negative. Earlier it was found that with the united-atom TraPPE model for alkanes and the SPC/E model for water, one had to artificially enhance the attractive alkane-water cross interaction to capture this behavior. Here we revisit the calculation of μex using the polarizable AMOEBA and the non-polarizable Charmm General (CGenFF) forcefields. We test both the AMOEBA03 and AMOEBA14 water models; the former has been validated with the AMOEBA alkane model while the latter is a revision of AMOEBA03 to better describe liquid water. We calculate μex using the test particle method. With CGenFF, μex is positive and the error relative to experiments is about 1.5 kBT. With AMOEBA, μex is negative and deviations relative to experiments are between 0.25 kBT (AMOEBA14) and 0.5 kBT (AMOEBA03). Quantum chemical calculations in a continuum solvent suggest that zero point effects may account for some of the deviation. Forcefield limitations notwithstanding, electrostatic and induction effects, commonly ignored in consideration of water-alkane interactions, appear to be decisive in the solubility of water in alkanes.

Decay of intestinal enterococci concentrations in high-energy estuarine and coastal waters: towards real-time T90 values for modelling faecal indicators in recreational waters.

PubMed

Kay, D; Stapleton, C M; Wyer, M D; McDonald, A T; Crowther, J; Paul, N; Jones, K; Francis, C; Watkins, J; Wilkinson, J; Humphrey, N; Lin, B; Yang, L; Falconer, R A; Gardner, S

2005-02-01

Intestinal enterococci are the principal 'health-evidence-based' parameter recommended by WHO for the assessment of marine recreational water compliance. Understanding the survival characteristics of these organisms in nearshore waters is central to public health protection using robust modelling to effect real-time prediction of water quality at recreation sites as recently suggested by WHO and the Commission of the European Communities Previous models have more often focused on the coliform parameters and assumed two static day-time and night-time T90 values to characterise the decay process. The principal driver for enterococci survival is the received dose of irradiance from sunlight. In the water column, transmission of irradiance is determined by turbidity produced by suspended material. This paper reports the results of irradiated microcosm experiments using simulated sunlight to investigate the decay of intestinal enterococci in relatively turbid estuarine and coastal waters collected from the Severn Estuary and Bristol Channel, UK. High-turbidity estuarine waters produced a T90 value of 39.5 h. Low-turbidity coastal waters produced a much shorter T90 value of 6.6 h. In experiments receiving no irradiation, high-turbidity estuarine waters also produced a longer T90 of 65.1 h compared with corresponding low-turbidity coastal waters, T90 24.8 h. Irradiated T90 values were correlated with salinity, turbidity and suspended solids (r>0.8, p<0.001). The results suggest that enterococci decay in irradiated experiments with turbidity >200 NTU is similar to decay observed under dark conditions. Most significantly, these results suggest that modelling turbidity and or suspended solids offers a potential means of predicting T90 values in 'real-time' for discrete cells of a hydrodynamic model.

Flow dynamics and salt transport in a coastal aquifer driven by a stratified saltwater body: Lab experiment and numerical modeling

NASA Astrophysics Data System (ADS)

Oz, Imri; Shalev, Eyal; Yechieli, Yoseph; Gavrieli, Ittai; Gvirtzman, Haim

2014-04-01

This paper examines the transient development and the steady-state configuration of groundwater within a coastal aquifer adjacent to a stratified saltwater body. Such systems consist of three different water types: the regional fresh groundwater, and low and high salinity brines forming the upper and lower water layers of the stratified water body, respectively. The dynamics, location and the geometry of the interfaces and the density-driven circulation flows that develop in the aquifer are examined using laboratory experiments and numerical modeling at the same scale. The results show that the transient intrusion of the different water bodies into the aquifer takes place at different rates, and that the locations of the interfaces between them change with time, before reaching steady-state. Under steady-state conditions both the model and the experiments show the existence of three interfaces between the three water types. The numerical model, which is calibrated against the salinity distribution and groundwater discharge rate in the laboratory experiments, allows the quantification of the flow rates and flow patterns within the aquifer. These flow patterns, which cannot be derived from laboratory experiments, show the transient development of three circulation cells which are confined between the three interfaces. These results confirm the hypothesis that has been previously suggested based solely on a steady-state numerical modeling defined by a conceptual understanding. Parametric analysis shows that the creation of three circulation cells and three interfaces is limited to certain conditions and defines the ranges for the creation of this unique system.

Multiresponse modeling of variably saturated flow and isotope tracer transport for a hillslope experiment at the Landscape Evolution Observatory

NASA Astrophysics Data System (ADS)

Scudeler, Carlotta; Pangle, Luke; Pasetto, Damiano; Niu, Guo-Yue; Volkmann, Till; Paniconi, Claudio; Putti, Mario; Troch, Peter

2016-10-01

This paper explores the challenges of model parameterization and process representation when simulating multiple hydrologic responses from a highly controlled unsaturated flow and transport experiment with a physically based model. The experiment, conducted at the Landscape Evolution Observatory (LEO), involved alternate injections of water and deuterium-enriched water into an initially very dry hillslope. The multivariate observations included point measures of water content and tracer concentration in the soil, total storage within the hillslope, and integrated fluxes of water and tracer through the seepage face. The simulations were performed with a three-dimensional finite element model that solves the Richards and advection-dispersion equations. Integrated flow, integrated transport, distributed flow, and distributed transport responses were successively analyzed, with parameterization choices at each step supported by standard model performance metrics. In the first steps of our analysis, where seepage face flow, water storage, and average concentration at the seepage face were the target responses, an adequate match between measured and simulated variables was obtained using a simple parameterization consistent with that from a prior flow-only experiment at LEO. When passing to the distributed responses, it was necessary to introduce complexity to additional soil hydraulic parameters to obtain an adequate match for the point-scale flow response. This also improved the match against point measures of tracer concentration, although model performance here was considerably poorer. This suggests that still greater complexity is needed in the model parameterization, or that there may be gaps in process representation for simulating solute transport phenomena in very dry soils.

Effects of pH2O, pH2 and fO2 on the Diffusion of H-Bearing Species in Lunar Basalt and an Iron-Free Basaltic Analog at 1 atm

NASA Astrophysics Data System (ADS)

Newcombe, M. E.; Beckett, J. R.; Baker, M. B.; Newman, S.; Guan, Y.; Eiler, J. M.; Stolper, E. M.

2016-12-01

We have conducted water diffusion experiments in synthetic Apollo 15 "yellow glass" (LG) and an iron-free basaltic analog melt (AD) at 1 atm and 1350 °C over a range of fO2 conditions from IW-2.2 to IW+6.7 and over a range of pH2/pH2O from nominally zero to 10. The water concentrations measured in our quenched experimental glasses by SIMS and FTIR vary from a few ppm to 430 ppm. Many studies of water diffusion at higher water concentrations indicate that the apparent diffusivity of total water (D*water; see [1]) in silicate melts is highly concentration dependent at water contents >0.1 wt% (e.g., [1]). However, water concentration gradients in each of our AD and LG experiments are well described by models in which D*water is assumed to be constant. Best-fit values of D*water obtained for our AD and LG experiments are consistent with a modified speciation model [2] in which both molecular water and hydroxyl are allowed to diffuse, and in which hydroxyl is the dominant diffusing species at the low total water concentrations of our experiments. Water concentration gradients generated during hydration and dehydration experiments conducted simultaneously propagate approximately equal distances into the melt and have the same concentration of water dissolved in the melt at the melt-vapor interface, suggesting that hydration and dehydration are symmetric under the conditions of our experiments. Best-fit values of D*water for our LG experiments vary within a factor of 2 over a range of pH2/pH2O from 0.007 to 9.7 (a range of ƒO2 from IW-2.2 to IW+4.9) and a water concentration range from 80 ppm to 280 ppm. The relative insensitivity of D*water to variations in pH2 suggests that loss of H during the degassing of the lunar melts described by [3] was not primarily by loss of dissolved H2. The value of D*water chosen by [3] for modeling diffusive degassing of lunar volcanic glasses is within a factor of three of our measured value in LG melt at 1350 °C. [1] Zhang et al. (1991) GCA 55, 441-456; [2] Ni et al. (2013) GCA 103, 36-48; [3] Saal et al. (2008) Nature 454, 192-195.

Comparison of MRI techniques and modelling with R-SWMS for determining solute distribution patterns and root water uptake of a white lupine plant (Lupinus Albus L.).

NASA Astrophysics Data System (ADS)

Koch, Axelle; Schröder, Natalie; Pohlmeier, Andreas; Garré, Sarah; Vanderborght, Jan; Javaux, Mathieu

2017-04-01

Measuring water extraction by plant would allow us to better understand root water uptake processes and how soil and plant properties affect them. Yet, direct measurement of root water uptake is still challenging and determining its distribution requires coupling experimentation and modelling. In this study, we investigated how the 3D monitoring of a tracer movement in a sand container with a lupine plant could inform us about root water uptake process. A sand column (10 cm height, 5 cm inner diameter) planted with an 18-day-old white lupine was subject to a tracer experiment with a chemically inert tracer (1 mmol/L Gd-DTPA2-) applied for 6 days. Then the tracer and water fluxes were stopped. The plume was monitored in 3-D for 7 days by Magnetic Resonance Imaging (Haber-Pohlmeier et al, unp). In addition the breakthrough curve at the outlet was also measured. We used a biophysical 3-D soil-plant model: R-SWMS (Javaux et al, 2008) to extract information from this experiment. First, we ran a virtual experiment to check the assumption that Gd concentration increase around roots is proportional to the extracted soil water during the same period. We also investigated whether this type of experiment helps discriminate different root hydraulic properties with a sensitivity analysis. Then, we compared the experimental and simulated Gd concentration patterns. A preliminary (qualitative) assessment showed that measured Gd distribution patterns were better represented by the model at day 7, where the main driver of the concentration distribution was root and not soil heterogeneity (which is not taken into account in the model). The main spatial and temporal features of the transport where adequately reproduced by the model in particular during the last day. The distribution of the tracer was shown to be sensitive to the root hydraulic properties. To conclude, information about root water uptake distributions and so about root hydraulic properties could be deduced from Gd concentration maps. Keywords: R-SWMS; Modelling; MRI; Root Water Uptake; Gadolinium

Suppression of ENSO in a coupled model without water vapor feedback

NASA Astrophysics Data System (ADS)

Hall, A.; Manabe, S.

We examine 800-year time series of internally generated variability in both a coupled ocean-atmosphere model where water vapor anomalies are not allowed to interact with longwave radiation and one where they are. The ENSO-like phenomenon in the experiment without water vapor feedback is drastically suppressed both in amplitude and geographic extent relative to the experiment with water vapor feedback. Surprisingly, the reduced amplitude of ENSO-related sea surface temperature anomalies in the model without water vapor feedback cannot be attributed to greater longwave damping of sea surface temperature. (Differences between the two experiments in radiative feedback due to clouds counterbalance almost perfectly the differences in radiative feedback due to water vapor.) Rather, the interaction between water vapor anomalies and longwave radiation affects the ENSO-like phenomenon through its influence on the vertical structure of radiative heating: Because of the changes in water vapor associated with it, a given warm equatorial Pacific sea surface temperature anomaly is associated with a radiative heating profile that is much more gravitationally unstable when water vapor feedback is present. The warm sea surface temperature anomaly therefore results in more convection in the experiment with water vapor feedback. The increased convection, in turn, is related to a larger westerly wind-stress anomaly, which creates a larger decrease in upwelling of cold water, thereby enhancing the magnitude of the original warm sea surface temperature anomaly. In this manner, the interaction between water vapor anomalies and longwave radiation magnifies the air-sea interactions at the heart of the ENSO phenomenon; without this interaction, the coupling between sea surface temperature and wind stress is effectively reduced, resulting in smaller amplitude ENSO episodes with a more limited geographical extent.

Water Leak Detection by Using Ground Penetrating Radar, Synthetic Simulation and Four-Dimensional Visualization

NASA Astrophysics Data System (ADS)

Al-Shukri, H.; Eyuboglu, S.; Mahdi, H.

2005-12-01

Many geophysical techniques have been suggested as candidates for detecting water leakage in water distribution system, including ground penetrating radar (GPR), acoustic devices, and gas sampling devices. A series of laboratory experiments were conducted to determine the validity and effectiveness of GPR in detecting water leakage in metal and plastic PVC pipes. The goal was to derive a practical and robust procedure for detecting such leakage. Initially, prototype laboratory experiments were designed to simulate leaks in both PVC and metal pipe. The experiments were very well controlled and results obtained indicate that GPR is effective in detecting subsurface water leaks. This was followed by an outdoor life size experiments. 50 feet by 30 feet by 5 feet test bed was constructed using local soil and commercial water distribution pipes. A 400 MHz antenna was used to collect three-dimensional GPR data as a function of time for a number of experiments using different type of pipes. Advanced imaging and visualization technology was used to further analyze the data. The UALR Virtual Reality Center CAVE facilities were utilized to accomplish this test. Results obtained indicate that GPR is effective in detecting subsurface water leaks in both pipes. Synthetic models of the GPR signals based on Finite Difference Time Domain Method (FDTD) were built to help select an appropriate equipment configuration (frequency band, type of antenna, and real-time imaging software) prior to data acquisition. The simulation software was used to determine the near-field radiation characteristics of the GPR antenna. Different experimental models were adapted for which observational GPR data was previously collected. Matlab regression analysis was used to generate the incident waves for each model to ensure highly accurate and controlled experiments.

Investigation and mitigation of condensation induced water hammer by stratified flow experiments

NASA Astrophysics Data System (ADS)

Kadakia, Hiral J.

This research primarily focuses on the possibility of using stratified flow in preventing an occurrence of condensation induced water hammer (CIWH) in horizontal pipe involving steam and subcooled water. A two-phase flow loop simulating the passive safety systems of an advanced light water reactor was constructed and a series of stratified flow experiments were carried out involving a system of subcooled water, saturated water, and steam. Special instruments were designed to measure steam flow rate and subcooled liquid velocity. These experiments showed that when flow field conditions meet certain criteria CIWH does occur. Flow conditions used in experiments were typically observed in passive safety systems of an advanced light water cooled reactor. This research summarizes a) literature research and other experimental data that signify an occurrence of CIWH, b) experiments in an effort to show an occurrence of CIWH and the ability to prevent CIWH, c) qualitative and quantitative results to underline the mechanism of CIWH, d) experiments that show CIWH can be prevented under certain conditions, and e) guidelines for the safe operating conditions. Based on initial experiment results it was observed that Bernoulli's effect can play an important role in wave formation and instability. A separate effect table top experiment was constructed with plexi-glass. A series of entrance effect tests and stratified experiments were carried out with different fluids to study wave formation and wave bridging. Special test series experiments were carried out to investigate the presence of a saturated layer. The effect of subcooled water and steam flow on wedge length and depth were recorded. These experiments helped create a model which calculates wedge and depth of wedge for a given condition of steam and subcooled water. A very good comparison between the experiment results and the model was obtained. These experiments also showed that the presence of saturated layer can mitigate the CIWH. Flow conditions require to mitigate the CIWH must be such that subcooled water is laminar and steam flow rate is less than critical. Finally, a data bank of containing large number of experiments was created and guidelines for safe filling and draining of the system involving steam and subcooled water were created. Also several suggestions are provided to stop CIWH in case it does occur.

Isotopic composition of water vapor near the air-water interface

NASA Astrophysics Data System (ADS)

Zannoni, Daniele; Bergamasco, Andrea; Peschiutta, Mirco; Rampazzo, Giancarlo; Stenni, Barbara

2017-04-01

Evaporation is a key process in water cycle that links liquid water to the atmosphere. In the last fifty years stable isotopes of hydrogen and oxygen have been intensively used to describe climate processes related to evaporation and precipitation, ranging in different spatial and temporal scales. Evaporation introduces large isotopic effects in the phases involved. The well known Craig-Gordon model (Craig & Gordon, 1965) describes those isotopic effects involving several steps and different processes, moving from the air-water interface to the free atmosphere. However, very few works in literature have tested the vertical behavior of the Craig-Gordon model in natural conditions on both fresh and marine waters. In this work we present the results from four field experiments aimed to describe the vertical variability of δ18O and δD in the first few meters over a large water body (the coastal lagoon of Venice, northern Italy) and to test the Craig-Gordon model in such conditions. Each experiment involved cryotrapping of water vapor at different height over the water surface (0.1m, 2m and 4m) and the sampling of the liquid water at two depth (surface and 0.5m). During the experiments, water vapor was also sampled in the nearest mainland (˜2.5 km from gradient measurements) to determine the isotopic composition of background water vapor. Liquid samples were then analyzed with a Picarro L1102-i and Thermo-Fisher Delta Plus Advantage for water vapor and lagoon water, respectively. The last two experiments have also involved simultaneous measurements of relative humidity using commercially-available humidity probes at each height. This approach was used to determine a reference scale in order to compare observations to modeled estimates. Despite the coarse time resolution due to cryotrapping method (measurements are averaged over 1.5 hours), preliminary results show measurable differences in the isotopic composition of water vapor along the vertical gradient and good agreement between observations and predicted values from the model. Even if this work is an exploratory phase it shows an interesting potential to grow our understanding of the processes involved as well as a useful implementation for future studies focused on fractionation of water isotopes due to evaporation in natural conditions. References Craig, H., & Gordon, L. I. (1965). Deuterium and oxygen 18 variations in the ocean and the marine atmosphere.

Land use, water and Mediterranean landscapes: modelling long-term dynamics of complex socio-ecological systems.

PubMed

Barton, C Michael; Ullah, Isaac I; Bergin, Sean

2010-11-28

The evolution of Mediterranean landscapes during the Holocene has been increasingly governed by the complex interactions of water and human land use. Different land-use practices change the amount of water flowing across the surface and infiltrating the soil, and change water's ability to move surface sediments. Conversely, water amplifies the impacts of human land use and extends the ecological footprint of human activities far beyond the borders of towns and fields. Advances in computational modelling offer new tools to study the complex feedbacks between land use, land cover, topography and surface water. The Mediterranean Landscape Dynamics project (MedLand) is building a modelling laboratory where experiments can be carried out on the long-term impacts of agropastoral land use, and whose results can be tested against the archaeological record. These computational experiments are providing new insights into the socio-ecological consequences of human decisions at varying temporal and spatial scales.

Geochemical simulation of fluid rock interactions to predict flowback water compostions during hydraulic fracturing

NASA Astrophysics Data System (ADS)

Kühn, Michael; Vieth-Hillebrand, Andrea; Wilke, Franziska D. H.

2017-04-01

Black shales are a heterogeneous mixture of minerals, organic matter and formation water and little is actually known about the fluid-rock interactions during hydraulic fracturing and their effects on composition of flowback and produced water. Geochemical simulations have been performed based on the analyses of "real" flowback water samples and artificial stimulation fluids from lab experiments with the aim to set up a chemical process model for shale gas reservoirs. Prediction of flowback water compositions for potential or already chosen sites requires validated and parameterized geochemical models. For the software "Geochemist's Workbench" (GWB) data bases are adapted and amended based on a literature review. Evaluation of the system has been performed in comparison with the results from laboratory experiments. Parameterization was done in regard to field data provided. Finally, reaction path models are applied for quantitative information about the mobility of compounds in specific settings. Our work leads to quantitative estimates of reservoir compounds in the flowback based on calibrations by laboratory experiments. Such information is crucial for the assessment of environmental impacts as well as to estimate human- and ecotoxicological effects of the flowback waters from a variety of natural gas shales. With a comprehensive knowledge about potential composition and mobility of flowback water, selection of water treatment techniques will become easier.

Three-dimensional modeling of flow through fractured tuff at Fran Ridge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eaton, R.R.; Ho, C.K.; Glass, RJ.

1996-09-01

Numerical studies have been made of an infiltration experiment at Fran Ridge using the TOUGH2 code to aid in the selection of computational models for performance assessment. The exercise investigates the capabilities of TOUGH2 to model transient flows through highly fractured tuff and provides a possible means of calibration. Two distinctly different conceptual models were used in the TOUGH2 code, the dual permeability model and the equivalent continuum model. The infiltration test modeled involved the infiltration of dyed ponded water for 36 minutes. The 205 gallon infiltration of water observed in the experiment was subsequently modeled using measured Fran Ridgemore » fracture frequencies, and a specified fracture aperture of 285 {micro}m. The dual permeability formulation predicted considerable infiltration along the fracture network, which was in agreement with the experimental observations. As expected, al fracture penetration of the infiltrating water was calculated using the equivalent continuum model, thus demonstrating that this model is not appropriate for modeling the highly transient experiment. It is therefore recommended that the dual permeability model be given priority when computing high-flux infiltration for use in performance assessment studies.« less

Three-dimensional modeling of flow through fractured tuff at Fran Ridge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eaton, R.R.; Ho, C.K.; Glass, R.J.

1996-01-01

Numerical studies have been made of an infiltration experiment at Fran Ridge using the TOUGH2 code to aid in the selection of computational models for performance assessment. The exercise investigates the capabilities of TOUGH2 to model transient flows through highly fractured tuff and provides a possible means of calibration. Two distinctly different conceptual models were used in the TOUGH2 code, the dual permeability model and the equivalent continuum model. The infiltration test modeled involved the infiltration of dyed ponded water for 36 minutes. The 205 gallon filtration of water observed in the experiment was subsequently modeled using measured Fran Ridgemore » fracture frequencies, and a specified fracture aperture of 285 {mu}m. The dual permeability formulation predicted considerable infiltration along the fracture network, which was in agreement with the experimental observations. As expected, minimal fracture penetration of the infiltrating water was calculated using the equivalent continuum model, thus demonstrating that this model is not appropriate for modeling the highly transient experiment. It is therefore recommended that the dual permeability model be given priority when computing high-flux infiltration for use in performance assessment studies.« less

High Speed Trimaran (HST) Seatrain Experiments, Model 5714

DTIC Science & Technology

2013-12-01

Marine Highway 1 Historical Seatrains 1 Objectives 2 Hull &: Model Description 4 Data Acquisition and Instrumentation 7 Carriage II - Deep ...Operational Demonstration Measurement System 10 Experimental Procedures 10 Carriage II - Deep Water Basin Test 10 Calm Water Resistance 11... Deep Water Basin Analysis 17 Calm Water Resistance 17 Longitudinal Flow Through The Propeller Plane 18 Body Forces & Moments 18

The Widom line and dynamical crossover in supercritical water: Popular water models versus experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Corradini, D.; Rovere, M.; Gallo, P., E-mail: gallop@fis.uniroma3.it

2015-09-21

In a previous study [Gallo et al., Nat. Commun. 5, 5806 (2014)], we have shown an important connection between thermodynamic and dynamical properties of water in the supercritical region. In particular, by analyzing the experimental viscosity and the diffusion coefficient obtained in simulations performed using the TIP4P/2005 model, we have found that the line of response function maxima in the one phase region, the Widom line, is connected to a crossover from a liquid-like to a gas-like behavior of the transport coefficients. This is in agreement with recent experiments concerning the dynamics of supercritical simple fluids. We here show howmore » different popular water models (TIP4P/2005, TIP4P, SPC/E, TIP5P, and TIP3P) perform in reproducing thermodynamic and dynamic experimental properties in the supercritical region. In particular, the comparison with experiments shows that all the analyzed models are able to qualitatively predict the dynamical crossover from a liquid-like to a gas-like behavior upon crossing the Widom line. Some of the models perform better in reproducing the pressure-temperature slope of the Widom line of supercritical water once a rigid shift of the phase diagram is applied to bring the critical points to coincide with the experimental ones.« less

A second generation distributed point polarizable water model.

PubMed

Kumar, Revati; Wang, Fang-Fang; Jenness, Glen R; Jordan, Kenneth D

2010-01-07

A distributed point polarizable model (DPP2) for water, with explicit terms for charge penetration, induction, and charge transfer, is introduced. The DPP2 model accurately describes the interaction energies in small and large water clusters and also gives an average internal energy per molecule and radial distribution functions of liquid water in good agreement with experiment. A key to the success of the model is its accurate description of the individual terms in the n-body expansion of the interaction energies.

Swelling equilibrium of dentin adhesive polymers formed on the water-adhesive phase boundary: Experiments and micromechanical model

PubMed Central

Misra, Anil; Parthasarathy, Ranganathan; Ye, Qiang; Singh, Viraj; Spencer, Paulette

2013-01-01

During their application to the wet, oral environment, dentin adhesives can experience phase separation and composition change which can compromise the quality of the hybrid layer formed at the dentin-adhesive interface. The chemical composition of polymer phases formed in the hybrid layer can be represented using a ternary water-adhesive phase diagram. In this paper, these polymer phases have been characterized using a suite of mechanical tests and swelling experiments. The experimental results were evaluated using granular micromechanics based model that incorporates poro-mechanical effects and polymer-solvent thermodynamics. The variation of the model parameters and model-predicted polymer properties has been studied as a function of composition along the phase boundary. The resulting structure-property correlations provide insight into interactions occurring at the molecular level in the saturated polymer system. These correlations can be used for modeling the mechanical behavior of hybrid layer, and are expected to aid in the design and improvement of water-compatible dentin adhesive polymers. PMID:24076070

Tracer water transport and subgrid precipitation variation within atmospheric general circulation models

NASA Astrophysics Data System (ADS)

Koster, Randal D.; Eagleson, Peter S.; Broecker, Wallace S.

1988-03-01

A capability is developed for monitoring tracer water movement in the three-dimensional Goddard Institute for Space Science Atmospheric General Circulation Model (GCM). A typical experiment with the tracer water model follows water evaporating from selected grid squares and determines where this water first returns to the Earth's surface as precipitation or condensate, thereby providing information on the lateral scales of hydrological transport in the GCM. Through a comparison of model results with observations in nature, inferences can be drawn concerning real world water transport. Tests of the tracer water model include a comparison of simulated and observed vertically-integrated vapor flux fields and simulations of atomic tritium transport from the stratosphere to the oceans. The inter-annual variability of the tracer water model results is also examined.

Tracer water transport and subgrid precipitation variation within atmospheric general circulation models

NASA Technical Reports Server (NTRS)

Koster, Randal D.; Eagleson, Peter S.; Broecker, Wallace S.

1988-01-01

A capability is developed for monitoring tracer water movement in the three-dimensional Goddard Institute for Space Science Atmospheric General Circulation Model (GCM). A typical experiment with the tracer water model follows water evaporating from selected grid squares and determines where this water first returns to the Earth's surface as precipitation or condensate, thereby providing information on the lateral scales of hydrological transport in the GCM. Through a comparison of model results with observations in nature, inferences can be drawn concerning real world water transport. Tests of the tracer water model include a comparison of simulated and observed vertically-integrated vapor flux fields and simulations of atomic tritium transport from the stratosphere to the oceans. The inter-annual variability of the tracer water model results is also examined.

A Model for Hydraulic Properties Based on Angular Pores with Lognormal Size Distribution

NASA Astrophysics Data System (ADS)

Durner, W.; Diamantopoulos, E.

2014-12-01

Soil water retention and unsaturated hydraulic conductivity curves are mandatory for modeling water flow in soils. It is a common approach to measure few points of the water retention curve and to calculate the hydraulic conductivity curve by assuming that the soil can be represented as a bundle of capillary tubes. Both curves are then used to predict water flow at larger spatial scales. However, the predictive power of these curves is often very limited. This can be very easily illustrated if we measure the soil hydraulic properties (SHPs) for a drainage experiment and then use these properties to predict the water flow in the case of imbibition. Further complications arise from the incomplete wetting of water at the solid matrix which results in finite values of the contact angles between the solid-water-air interfaces. To address these problems we present a physically-based model for hysteretic SHPs. This model is based on bundles of angular pores. Hysteresis for individual pores is caused by (i) different snap-off pressures during filling and emptying of single angular pores and (ii) by different advancing and receding contact angles for fluids that are not perfectly wettable. We derive a model of hydraulic conductivity as a function of contact angle by assuming flow perpendicular to pore cross sections and present closed-form expressions for both the sample scale water retention and hydraulic conductivity function by assuming a log-normal statistical distribution of pore size. We tested the new model against drainage and imbibition experiments for various sandy materials which were conducted with various liquids of differing wettability. The model described both imbibition and drainage experiments very well by assuming a unique pore size distribution of the sample and a zero contact angle for the perfectly wetting liquid. Eventually, we see the possibility to relate the particle size distribution with a model which describes the SHPs.

Numerical simulation of the geographical sources of water for Continental Scale Experiments (CSEs) Precipitation

NASA Technical Reports Server (NTRS)

Bosilovich, Michael G.; Sud, Yogesh; Schubert, Siegfried D.; Walker, Gregory K.

2003-01-01

There are several important research questions that the Global Energy and Water Cycle Experiment (GEWEX) is actively pursuing, namely: What is the intensity of the water cycle and how does it change? And what is the sustainability of water resources? Much of the research to address these questions is directed at understanding the atmospheric water cycle. In this paper, we have used a new diagnostic tool, called Water Vapor Tracers (WVTs), to quantify the how much precipitation originated as continental or oceanic evaporation. This shows how long water can remain in the atmosphere and how far it can travel. The model-simulated data are analyzed over regions of interest to the GEWEX community, specifically, their Continental Scale Experiments (CSEs) that are in place in the United States, Europe, Asia, Brazil, Africa and Canada. The paper presents quantitative data on how much each continent and ocean on Earth supplies water for each CSE. Furthermore, the analysis also shows the seasonal variation of the water sources. For example, in the United States, summertime precipitation is dominated by continental (land surface) sources of water, while wintertime precipitation is dominated by the Pacific Ocean sources of water. We also analyze the residence time of water in the atmosphere. The new diagnostic shows a longer residence time for water (9.2 days) than more traditional estimates (7.5 days). We emphasize that the results are based on model simulations and they depend on the model s veracity. However, there are many potential uses for the new diagnostic tool in understanding weather processes and large and small scales.

Preliminary Experimental Examination Of Controls On Methane Expulsion During Melting Of Natural Gas Hydrate Systems

NASA Astrophysics Data System (ADS)

Kneafsey, T. J.; Flemings, P. B.; Bryant, S. L.; You, K.; Polito, P. J.

2013-12-01

Global climate change will cause warming of the oceans and land. This will affect the occurrence, behavior, and location of subseafloor and subterranean methane hydrate deposits. We suggest that in many natural systems local salinity, elevated by hydrate formation or freshened by hydrate dissociation, may control gas transport through the hydrate stability zone. We are performing experiments and modeling the experiments to explore this behavior for different warming scenarios. Initially, we are exploring hydrate association/dissociation in saline systems with constant water mass. We compare experiments run with saline (3.5 wt. %) water vs. distilled water in a sand mixture at an initial water saturation of ~0.5. We increase the pore fluid (methane) pressure to 1050 psig. We then stepwise cool the sample into the hydrate stability field (~3 degrees C), allowing methane gas to enter as hydrate forms. We measure resistivity and the mass of methane consumed. We are currently running these experiments and we predict our results from equilibrium thermodynamics. In the fresh water case, the modeled final hydrate saturation is 63% and all water is consumed. In the saline case, the modeled final hydrate saturation is 47%, the salinity is 12.4 wt. %, and final water saturation is 13%. The fresh water system is water-limited: all the water is converted to hydrate. In the saline system, pore water salinity is elevated and salt is excluded from the hydrate structure during hydrate formation until the salinity drives the system to three phase equilibrium (liquid, gas, hydrate) and no further hydrate forms. In our laboratory we can impose temperature gradients within the column, and we will use this to investigate equilibrium conditions in large samples subjected to temperature gradients and changing temperature. In these tests, we will quantify the hydrate saturation and salinity over our meter-long sample using spatially distributed temperature sensors, spatially distributed resistivity probes, compressional wave velocities, and X-ray computed tomography scanning. Modeling of hydrate formation and dissociation for these conditions indicates that the transport of bulk fluid phases (gas and water) plays a crucial role in the overall behavior, and we will explore open-system boundary conditions in the experiments to test this prediction.

Advances in modelling of condensation phenomena

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, W.S.; Zaltsgendler, E.; Hanna, B.

1997-07-01

The physical parameters in the modelling of condensation phenomena in the CANDU reactor system codes are discussed. The experimental programs used for thermal-hydraulic code validation in the Canadian nuclear industry are briefly described. The modelling of vapour generation and in particular condensation plays a key role in modelling of postulated reactor transients. The condensation models adopted in the current state-of-the-art two-fluid CANDU reactor thermal-hydraulic system codes (CATHENA and TUF) are described. As examples of the modelling challenges faced, the simulation of a cold water injection experiment by CATHENA and the simulation of a condensation induced water hammer experiment by TUFmore » are described.« less

Using laboratory flow experiments and reactive chemical transport modeling for designing waterflooding of the Agua Fria Reservoir, Poza Rica-Altamira Field, Mexico

DOE Office of Scientific and Technical Information (OSTI.GOV)

Birkle, P.; Pruess, K.; Xu, T.

Waterflooding for enhanced oil recovery requires that injected waters must be chemically compatible with connate reservoir waters, in order to avoid mineral dissolution-and-precipitation cycles that could seriously degrade formation permeability and injectivity. Formation plugging is a concern especially in reservoirs with a large content of carbonates, such as calcite and dolomite, as such minerals typically react rapidly with an aqueous phase, and have strongly temperature-dependent solubility. Clay swelling can also pose problems. During a preliminary waterflooding pilot project, the Poza Rica-Altamira oil field, bordering the Gulf coast in the eastern part of Mexico, experienced injectivity loss after five months ofmore » reinjection of formation waters into well AF-847 in 1999. Acidizing with HCl restored injectivity. We report on laboratory experiments and reactive chemistry modeling studies that were undertaken in preparation for long-term waterflooding at Agua Frma. Using analogous core plugs obtained from the same reservoir interval, laboratory coreflood experiments were conducted to examine sensitivity of mineral dissolution and precipitation effects to water composition. Native reservoir water, chemically altered waters, and distilled water were used, and temporal changes in core permeability, mineral abundances and aqueous concentrations of solutes were monitored. The experiments were simulated with the multi-phase, nonisothermal reactive transport code TOUGHREACT, and reasonable to good agreement was obtained for changes in solute concentrations. Clay swelling caused an additional impact on permeability behavior during coreflood experiments, whereas the modeled permeability depends exclusively on chemical processes. TOUGHREACT was then used for reservoir-scale simulation of injecting ambient-temperature water (30 C, 86 F) into a reservoir with initial temperature of 80 C (176 F). Untreated native reservoir water was found to cause serious porosity and permeability reduction due to calcite precipitation, which is promoted by the retrograde solubility of this mineral. Using treated water that performed well in the laboratory flow experiments was found to avoid excessive precipitation, and allowed injection to proceed.« less

Physicochemical Quality and Chemical Safety of Chlorine as a Reconditioning Agent and Wash Water Disinfectant for Fresh-Cut Lettuce Washing

PubMed Central

Van Haute, Sam; Holvoet, Kevin; Uyttendaele, Mieke

2013-01-01

Chlorine was assessed as a reconditioning agent and wash water disinfectant in the fresh-cut produce industry. Artificial fresh-cut lettuce wash water, made from butterhead lettuce, was used for the experiments. In the reconditioning experiments, chlorine was added to artificial wash water inoculated with Escherichia coli O157 (6 log CFU/ml). Regression models were constructed based on the inactivation data and validated in actual wash water from leafy vegetable processing companies. The model that incorporated chlorine dose and chemical oxygen demand (COD) of the wash water accurately predicted inactivation. Listeria monocytogenes was more resistant to chlorine reconditioning in artificial wash water than Salmonella spp. and Escherichia coli O157. During the washing process with inoculated lettuce (4 log CFU/g), in the absence of chlorine, there was a rapid microbial buildup in the water that accumulated to 5.4 ± 0.4 log CFU/100 ml after 1 h. When maintaining a residual concentration of 1 mg/liter free chlorine, wash water contamination was maintained below 2.7, 2.5, and 2.5 log CFU/100 ml for tap water and artificial process water with COD values of 500 and 1,000 mg O2/liter, respectively. A model was developed to predict water contamination during the dynamic washing process. Only minor amounts of total trihalomethanes were formed in the water during reconditioning. Total trihalomethanes accumulated to larger amounts in the water during the wash water disinfection experiments and reached 124.5 ± 13.4 μg/liter after 1 h of execution of the washing process in water with a COD of 1,000 mg O2/liter. However, no total trihalomethanes were found on the fresh-cut lettuce after rinsing. PMID:23396332

Physicochemical quality and chemical safety of chlorine as a reconditioning agent and wash water disinfectant for fresh-cut lettuce washing.

PubMed

Van Haute, Sam; Sampers, Imca; Holvoet, Kevin; Uyttendaele, Mieke

2013-05-01

Chlorine was assessed as a reconditioning agent and wash water disinfectant in the fresh-cut produce industry. Artificial fresh-cut lettuce wash water, made from butterhead lettuce, was used for the experiments. In the reconditioning experiments, chlorine was added to artificial wash water inoculated with Escherichia coli O157 (6 log CFU/ml). Regression models were constructed based on the inactivation data and validated in actual wash water from leafy vegetable processing companies. The model that incorporated chlorine dose and chemical oxygen demand (COD) of the wash water accurately predicted inactivation. Listeria monocytogenes was more resistant to chlorine reconditioning in artificial wash water than Salmonella spp. and Escherichia coli O157. During the washing process with inoculated lettuce (4 log CFU/g), in the absence of chlorine, there was a rapid microbial buildup in the water that accumulated to 5.4 ± 0.4 log CFU/100 ml after 1 h. When maintaining a residual concentration of 1 mg/liter free chlorine, wash water contamination was maintained below 2.7, 2.5, and 2.5 log CFU/100 ml for tap water and artificial process water with COD values of 500 and 1,000 mg O2/liter, respectively. A model was developed to predict water contamination during the dynamic washing process. Only minor amounts of total trihalomethanes were formed in the water during reconditioning. Total trihalomethanes accumulated to larger amounts in the water during the wash water disinfection experiments and reached 124.5 ± 13.4 μg/liter after 1 h of execution of the washing process in water with a COD of 1,000 mg O2/liter. However, no total trihalomethanes were found on the fresh-cut lettuce after rinsing.

Development of a multicomponent force and moment balance for water tunnel applications, volume 2

NASA Technical Reports Server (NTRS)

Suarez, Carlos J.; Malcolm, Gerald N.; Kramer, Brian R.; Smith, Brooke C.; Ayers, Bert F.

1994-01-01

The principal objective of this research effort was to develop a multicomponent strain gauge balance to measure forces and moments on models tested in flow visualization water tunnels. Static experiments (which are discussed in Volume 1 of this report) were conducted, and the results showed good agreement with wind tunnel data on similar configurations. Dynamic experiments, which are the main topic of this Volume, were also performed using the balance. Delta wing models and two F/A-18 models were utilized in a variety of dynamic tests. This investigation showed that, as expected, the values of the inertial tares are very small due to the low rotating rates required in a low-speed water tunnel and can, therefore, be ignored. Oscillations in pitch, yaw and roll showed hysteresis loops that compared favorably to data from dynamic wind tunnel experiments. Pitch-up and hold maneuvers revealed the long persistence, or time-lags, of some of the force components in response to the motion. Rotary-balance experiments were also successfully performed. The good results obtained in these dynamic experiments bring a whole new dimension to water tunnel testing and emphasize the importance of having the capability to perform simultaneous flow visualization and force/moment measurements during dynamic situations.

Experiments on water/melt explosions, nature of products, and models of dispersal

NASA Technical Reports Server (NTRS)

Sheridan, M. F.; Wohletz, K. H.

1984-01-01

Experiments were carried out in a steel pressure device using controlled amounts of water and thermite melt to examine the mechanical energy released on explosive mixing following the initial contact of the two materials. An experimental design was used to allow the direct calculation of the mechanical energy by the dynamic lift of the device as recorded both optically and physically. A large number of experiments were run to accurately determine the optimum mixture of water and melt for the conversion of thermal to mechanical energy. The maximum efficiency observed was about 12% at a water/thermite mass ratio of 0.50. These experiments are the basis for the development of models of hydroexplosions and melt fragmentation. Particles collected from the experimental products are similar in size and shape to pyroclasts produced by much larger hydrovolcanic explosions. Melt rupture at optimum ratios produces very fine particles whereas rupture at high or low water/melt ratios produces large melt fragments. Grain surface textures in the experimental products are also related to the water/melt ratio and the mechanism of explosive mixing. It is thus possible to have qualitative information about the nature of the explosion from the sizes and shapes of the fragments produced.

Physically-based model of soil hydraulic properties accounting for variable contact angle and its effect on hysteresis

NASA Astrophysics Data System (ADS)

Diamantopoulos, Efstathios; Durner, Wolfgang

2013-09-01

The description of soil water movement in the unsaturated zone requires the knowledge of the soil hydraulic properties, i.e. the water retention and the hydraulic conductivity function. A great amount of parameterizations for this can be found in the literature, the majority of which represent the complex pore space of soils as a bundle of cylindrical capillary tubes of various sizes. The assumption of zero contact angles between water and surface of the grains is also made. However, these assumptions limit the predictive capabilities of these models, leading often to errors in the prediction of water dynamics in soils. We present a pore-scale analysis for equilibrium liquid configuration in angular pores taking pore-scale hysteresis and the effect of contact angle into account. Furthermore, we propose a derivation of the hydraulic conductivity function, again as a function of the contact angle. An additional parameter was added to the conductivity function in order take into account effects which are not included in the analysis. Finally, we upscale our model from the pore to the sample scale by assuming a gamma statistical distribution of the pore sizes. Closed-form expressions are derived for both water retention and conductivity functions. The new model was tested against experimental data from multistep inflow/outflow (MSI/MSO) experiments for a sandy material. They were conducted using ethanol and water as the wetting liquid. Ethanol was assumed to form a zero contact angle with the soil grains. By keeping constant the parameters fitted from the ethanol MSO experiment we could predict the ethanol MSI dynamics based on our theory. Furthermore, by keeping constant the pore size distribution parameters from the ethanol experiments we could also predict very well the water dynamics for the MSO experiment. Lastly, we could predict the imbibition dynamics for the water MSI experiment by introducing a finite value of the contact angle. Most importantly, the predictions for both ethanol and water MSI/MSO dynamics were made by assuming a unique pore-size distribution.

Soil moisture dynamics modeling considering multi-layer root zone.

PubMed

Kumar, R; Shankar, V; Jat, M K

2013-01-01

The moisture uptake by plant from soil is a key process for plant growth and movement of water in the soil-plant system. A non-linear root water uptake (RWU) model was developed for a multi-layer crop root zone. The model comprised two parts: (1) model formulation and (2) moisture flow prediction. The developed model was tested for its efficiency in predicting moisture depletion in a non-uniform root zone. A field experiment on wheat (Triticum aestivum) was conducted in the sub-temperate sub-humid agro-climate of Solan, Himachal Pradesh, India. Model-predicted soil moisture parameters, i.e., moisture status at various depths, moisture depletion and soil moisture profile in the root zone, are in good agreement with experiment results. The results of simulation emphasize the utility of the RWU model across different agro-climatic regions. The model can be used for sound irrigation management especially in water-scarce humid, temperate, arid and semi-arid regions and can also be integrated with a water transport equation to predict the solute uptake by plant biomass.

Comparison of the Melting Temperatures of Classical and Quantum Water Potential Models

NASA Astrophysics Data System (ADS)

Du, Sen; Yoo, Soohaeng; Li, Jinjin

2017-08-01

As theoretical approaches and technical methods improve over time, the field of computer simulations for water has greatly progressed. Water potential models become much more complex when additional interactions and advanced theories are considered. Macroscopic properties of water predicted by computer simulations using water potential models are expected to be consistent with experimental outcomes. As such, discrepancies between computer simulations and experiments could be a criterion to comment on the performances of various water potential models. Notably, water can occur not only as liquid phases but also as solid and vapor phases. Therefore, the melting temperature related to the solid and liquid phase equilibrium is an effective parameter to judge the performances of different water potential models. As a mini review, our purpose is to introduce some water models developed in recent years and the melting temperatures obtained through simulations with such models. Moreover, some explanations referred to in the literature are described for the additional evaluation of the water potential models.

Pressure-induced transformations in glassy water: A computer simulation study using the TIP4P/2005 model

NASA Astrophysics Data System (ADS)

Wong, Jessina; Jahn, David A.; Giovambattista, Nicolas

2015-08-01

We study the pressure-induced transformations between low-density amorphous (LDA) and high-density amorphous (HDA) ice by performing out-of-equilibrium molecular dynamics (MD) simulations. We employ the TIP4P/2005 water model and show that this model reproduces qualitatively the LDA-HDA transformations observed experimentally. Specifically, the TIP4P/2005 model reproduces remarkably well the (i) structure (OO, OH, and HH radial distribution functions) and (ii) densities of LDA and HDA at P = 0.1 MPa and T = 80 K, as well as (iii) the qualitative behavior of ρ(P) during compression-induced LDA-to-HDA and decompression-induced HDA-to-LDA transformations. At the rates explored, the HDA-to-LDA transformation is less pronounced than in experiments. By studying the LDA-HDA transformations for a broad range of compression/decompression temperatures, we construct a "P-T phase diagram" for glassy water that is consistent with experiments and remarkably similar to that reported previously for ST2 water. This phase diagram is not inconsistent with the possibility of TIP4P/2005 water exhibiting a liquid-liquid phase transition at low temperatures. A comparison with previous MD simulation studies of SPC/E and ST2 water as well as experiments indicates that, overall, the TIP4P/2005 model performs better than the SPC/E and ST2 models. The effects of cooling and compression rates as well as aging on our MD simulations results are also discussed. The MD results are qualitatively robust under variations of cooling/compression rates (accessible in simulations) and are not affected by aging the hyperquenched glass for at least 1 μs. A byproduct of this work is the calculation of TIP4P/2005 water's diffusion coefficient D(T) at P = 0.1 MPa. It is found that, for T ≥ 210 K, D(T) ≈ (T - TMCT)-γ as predicted by mode coupling theory and in agreement with experiments. For TIP4P/2005 water, TMCT = 209 K and γ = 2.14, very close to the corresponding experimental values TMCT = 221 K and γ = 2.2.

Pressure-induced transformations in glassy water: A computer simulation study using the TIP4P/2005 model.

PubMed

Wong, Jessina; Jahn, David A; Giovambattista, Nicolas

2015-08-21

We study the pressure-induced transformations between low-density amorphous (LDA) and high-density amorphous (HDA) ice by performing out-of-equilibrium molecular dynamics (MD) simulations. We employ the TIP4P/2005 water model and show that this model reproduces qualitatively the LDA-HDA transformations observed experimentally. Specifically, the TIP4P/2005 model reproduces remarkably well the (i) structure (OO, OH, and HH radial distribution functions) and (ii) densities of LDA and HDA at P = 0.1 MPa and T = 80 K, as well as (iii) the qualitative behavior of ρ(P) during compression-induced LDA-to-HDA and decompression-induced HDA-to-LDA transformations. At the rates explored, the HDA-to-LDA transformation is less pronounced than in experiments. By studying the LDA-HDA transformations for a broad range of compression/decompression temperatures, we construct a "P-T phase diagram" for glassy water that is consistent with experiments and remarkably similar to that reported previously for ST2 water. This phase diagram is not inconsistent with the possibility of TIP4P/2005 water exhibiting a liquid-liquid phase transition at low temperatures. A comparison with previous MD simulation studies of SPC/E and ST2 water as well as experiments indicates that, overall, the TIP4P/2005 model performs better than the SPC/E and ST2 models. The effects of cooling and compression rates as well as aging on our MD simulations results are also discussed. The MD results are qualitatively robust under variations of cooling/compression rates (accessible in simulations) and are not affected by aging the hyperquenched glass for at least 1 μs. A byproduct of this work is the calculation of TIP4P/2005 water's diffusion coefficient D(T) at P = 0.1 MPa. It is found that, for T ≥ 210 K, D(T) ≈ (T - T(MCT))(-γ) as predicted by mode coupling theory and in agreement with experiments. For TIP4P/2005 water, T(MCT) = 209 K and γ = 2.14, very close to the corresponding experimental values T(MCT) = 221 K and γ = 2.2.

Pressure-induced transformations in computer simulations of glassy water.

PubMed

Chiu, Janet; Starr, Francis W; Giovambattista, Nicolas

2013-11-14

Glassy water occurs in at least two broad categories: low-density amorphous (LDA) and high-density amorphous (HDA) solid water. We perform out-of-equilibrium molecular dynamics simulations to study the transformations of glassy water using the ST2 model. Specifically, we study the known (i) compression-induced LDA-to-HDA, (ii) decompression-induced HDA-to-LDA, and (iii) compression-induced hexagonal ice-to-HDA transformations. We study each transformation for a broad range of compression/decompression temperatures, enabling us to construct a "P-T phase diagram" for glassy water. The resulting phase diagram shows the same qualitative features reported from experiments. While many simulations have probed the liquid-state phase behavior, comparatively little work has examined the transitions of glassy water. We examine how the glass transformations relate to the (first-order) liquid-liquid phase transition previously reported for this model. Specifically, our results support the hypothesis that the liquid-liquid spinodal lines, between a low-density and high-density liquid, are extensions of the LDA-HDA transformation lines in the limit of slow compression. Extending decompression runs to negative pressures, we locate the sublimation lines for both LDA and hyperquenched glassy water (HGW), and find that HGW is relatively more stable to the vapor. Additionally, we observe spontaneous crystallization of HDA at high pressure to ice VII. Experiments have also seen crystallization of HDA, but to ice XII. Finally, we contrast the structure of LDA and HDA for the ST2 model with experiments. We find that while the radial distribution functions (RDFs) of LDA are similar to those observed in experiments, considerable differences exist between the HDA RDFs of ST2 water and experiment. The differences in HDA structure, as well as the formation of ice VII (a tetrahedral crystal), are a consequence of ST2 overemphasizing the tetrahedral character of water.

Pressure-induced transformations in computer simulations of glassy water

NASA Astrophysics Data System (ADS)

Chiu, Janet; Starr, Francis W.; Giovambattista, Nicolas

2013-11-01

Glassy water occurs in at least two broad categories: low-density amorphous (LDA) and high-density amorphous (HDA) solid water. We perform out-of-equilibrium molecular dynamics simulations to study the transformations of glassy water using the ST2 model. Specifically, we study the known (i) compression-induced LDA-to-HDA, (ii) decompression-induced HDA-to-LDA, and (iii) compression-induced hexagonal ice-to-HDA transformations. We study each transformation for a broad range of compression/decompression temperatures, enabling us to construct a "P-T phase diagram" for glassy water. The resulting phase diagram shows the same qualitative features reported from experiments. While many simulations have probed the liquid-state phase behavior, comparatively little work has examined the transitions of glassy water. We examine how the glass transformations relate to the (first-order) liquid-liquid phase transition previously reported for this model. Specifically, our results support the hypothesis that the liquid-liquid spinodal lines, between a low-density and high-density liquid, are extensions of the LDA-HDA transformation lines in the limit of slow compression. Extending decompression runs to negative pressures, we locate the sublimation lines for both LDA and hyperquenched glassy water (HGW), and find that HGW is relatively more stable to the vapor. Additionally, we observe spontaneous crystallization of HDA at high pressure to ice VII. Experiments have also seen crystallization of HDA, but to ice XII. Finally, we contrast the structure of LDA and HDA for the ST2 model with experiments. We find that while the radial distribution functions (RDFs) of LDA are similar to those observed in experiments, considerable differences exist between the HDA RDFs of ST2 water and experiment. The differences in HDA structure, as well as the formation of ice VII (a tetrahedral crystal), are a consequence of ST2 overemphasizing the tetrahedral character of water.

A model for interpretation of brine-dependent spontaneous imbibition experiments

NASA Astrophysics Data System (ADS)

Evje, S.; Hiorth, A.

2011-12-01

Previous experimental results for spontaneous imbibition experiments in the context of chalk cores have revealed a rather puzzling behavior: the oil recovery curves, both the shape as well as the steady state level which is reached, depend strongly on the brine composition. In particular, it has been demonstrated that Mg,SO42-, and Ca 2+ play a central role in this physico-chemical system. A good theoretical understanding of these experimental results, in terms of mathematical models that can suggest possible explanations of the lab experiments as well as predict behavior not yet tested in the lab, seems to still be lacking. The purpose of this paper is to try to shed light on some important modeling aspects. The model we propose is an extended version of the classical Buckley-Leverett (BL) equation for two-phase spontaneous imbibition where the water saturation equation has been coupled to a system of reaction-diffusion (RD) equations describing water-rock chemistry relevant for chalk core plugs. As far as water-rock chemistry is concerned we focus in this work on the combined effect of transport and dissolution/precipitation of calcite, magnesite, and anhydrite. The line we pursue is to couple changes of the wetting state, expressed in terms of the relative permeability and capillary pressure functions, to the water-rock chemistry behavior. More precisely, we build into the model the mechanism that the rock surface will become more water-wet at the places where dissolution of calcite takes place. In particular, we illustrate and analyze how different compositions of the imbibing brine then lead to different water-rock interaction scenarios which in turn gives qualitative and quantitative differences in the solution of the saturation equation describing spontaneous imbibition. Comparison with relevant experimental behavior is included as well as illustration of some possible interesting and non-trivial characteristic features of the model reflecting the nonlinear coupling mechanisms between the RD model for the water-rock chemistry and the BL equation for the water-oil transport.

Effects of liquid layers and distribution patterns on three-phase saturation and relative permeability relationships: a micromodel study.

PubMed

Tsai, Jui-Pin; Chang, Liang-Cheng; Hsu, Shao-Yiu; Shan, Hsin-Yu

2017-12-01

In the current study, we used micromodel experiments to study three-phase fluid flow in porous media. In contrast to previous studies, we simultaneously observed and measured pore-scale fluid behavior and three-phase constitutive relationships with digital image acquisition/analysis, fluid pressure control, and permeability assays. Our results showed that the fluid layers significantly influenced pore-scale, three-phase fluid displacement as well as water relative permeability. At low water saturation, water relative permeability not only depended on water saturation but also on the distributions of air and diesel. The results also indicate that the relative permeability-saturation model proposed by Parker et al. (1987) could not completely describe the experimental data from our three-phase flow experiments because these models ignore the effects of phase distribution. A simple bundle-of-tubes model shows that the water relative permeability was proportional to the number of apparently continuous water paths before the critical stage in which no apparently continuous water flow path could be found. Our findings constitute additional information about the essential constitutive relationships involved in both the understanding and the modeling of three-phase flows in porous media.

Imaging and modelling root water uptake

NASA Astrophysics Data System (ADS)

Zarebanadkouki, M.; Meunier, F.; Javaux, M.; Kaestner, A.; Carminati, A.

2017-12-01

Spatially resolved measurement and modelling of root water uptake is urgently needed to identify root traits that can improve capture of water from the soil. However, measuring water fluxes into roots of transpiring plants growing in soil remains challenging. Here, we describe an in-situ technique to measure local fluxes of water into roots. The technique consists of tracing the transport of deuterated water (D2O) in soil and roots using time series neutron radiography and tomography. A diffusion-convection model was used to model the transport of D2O in roots. The model includes root features such as the endodermis, xylem and the composite flow of water in the apoplastic and symplastic pathways. Diffusion permeability of root cells and of the endodermis were estimated by fitting the experiment during the night, when transpiration was negligible. The water fluxes at different position of the root system were obtained by fitting the experiments at daytime. The results showed that root water uptake was not uniform along root system and varied among different root types. The measured profiles of root water uptake into roots were used to estimate the radial and axial hydraulic of the roots. A three-dimensional model of root water uptake was used to fit the measured water fluxes by adjusting the root radial and axial hydraulic conductivities. We found that the estimated radial conductivities decreased with root age, while the axial conducances increased, and they are different among root types. The significance of this study is the development of a method to estimate 1) water uptake and 2) the radial and axial hydraulic conductivities of roots of transpiring plants growing in the soil.

Modeling and experiments on tritium permeation in fusion reactor blankets

NASA Astrophysics Data System (ADS)

Holland, D. F.; Longhurst, G. R.

The determination of tritium loss from helium-cooled fusion breeding blankets are discussed. The issues are: (1) applicability of present models to permeation at low tritium pressures; (2) effectiveness of oxide layers in reducing permeation; (3) effectiveness of hydrogen addition as a means to lower tritium permeation; and (4) effectiveness of conversion to tritiated water and subsequent trapping to reduce permeation. Theoretical models applicable to these issues are discussed, and results of experiments in two areas are presented; permeation of mixtures of hydrogen isotopes and conversion to tritiated water.

Adsorptive Water Removal from Dichloromethane and Vapor-Phase Regeneration of a Molecular Sieve 3A Packed Bed

PubMed Central

2017-01-01

The drying of dichloromethane with a molecular sieve 3A packed bed process is modeled and experimentally verified. In the process, the dichloromethane is dried in the liquid phase and the adsorbent is regenerated by water desorption with dried dichloromethane product in the vapor phase. Adsorption equilibrium experiments show that dichloromethane does not compete with water adsorption, because of size exclusion; the pure water vapor isotherm from literature provides an accurate representation of the experiments. The breakthrough curves are adequately described by a mathematical model that includes external mass transfer, pore diffusion, and surface diffusion. During the desorption step, the main heat transfer mechanism is the condensation of the superheated dichloromethane vapor. The regeneration time is shortened significantly by external bed heating. Cyclic steady-state experiments demonstrate the feasibility of this novel, zero-emission drying process. PMID:28539701

THE VELOCITY OF DNAPL FINGERING IN WATER-SATURATED POROUS MEDIA LABORATORY EXPERIMENTS AND A MOBILE-IMMOBILE-ZONE MODEL. (R826157)

EPA Science Inventory

Dense nonaqueous phase liquids (DNAPLs) are immiscible with water and can give rise to highly fingered fluid distributions when infiltrating through water-saturated porous media. In this paper, a conceptual mobile_¯immobile_¯zone (MIZ) model is pr...

Integrating watershed hydrology and economics to establish a local market for water quality improvement: A field experiment

EPA Science Inventory

Innovative market mechanisms are being increasingly recognized as effective decision-making institutions to incorporate the value of ecosystem services into the economy. We present a field experiment that integrates an economic auction and a biophysical water flux model to develo...

Is the Water Heating Curve as Described?

ERIC Educational Resources Information Center

Riveros, H. G.; Oliva, A. I.

2008-01-01

We analysed the heating curve of water which is described in textbooks. An experiment combined with some simple heat transfer calculations is discussed. The theoretical behaviour can be altered by changing the conditions under which the experiment is modelled. By identifying and controlling the different parameters involved during the heating…

Air drying modelling of Mastocarpus stellatus seaweed a source of hybrid carrageenan

NASA Astrophysics Data System (ADS)

Arufe, Santiago; Torres, Maria D.; Chenlo, Francisco; Moreira, Ramon

2018-01-01

Water sorption isotherms from 5 up to 65 °C and air drying kinetics at 35, 45 and 55 °C of Mastocarpus stellatus seaweed were determined. Experimental sorption data were modelled using BET and Oswin models. A four-parameter model, based on Oswin model, was proposed to estimate equilibrium moisture content as function of water activity and temperature simultaneously. Drying experiments showed that water removal rate increased significantly with temperature from 35 to 45 °C, but at higher temperatures drying rate remained constant. Some chemical modifications of the hybrid carrageenans present in the seaweed can be responsible of this unexpected thermal trend. Experimental drying data were modelled using two-parameter Page model (n, k). Page parameter n was constant (1.31 ± 0.10) at tested temperatures, but k varied significantly with drying temperature (from 18.5 ± 0.2 10-3 min-n at 35 °C up to 28.4 ± 0.8 10-3 min-n at 45 and 55 °C). Drying experiments allowed the determination of the critical moisture content of seaweed (0.87 ± 0.06 kg water (kg d.b.)-1). A diffusional model considering slab geometry was employed to determine the effective diffusion coefficient of water during the falling rate period at different temperatures.

Experiment and simulation study of laser dicing silicon with water-jet

NASA Astrophysics Data System (ADS)

Bao, Jiading; Long, Yuhong; Tong, Youqun; Yang, Xiaoqing; Zhang, Bin; Zhou, Zupeng

2016-11-01

Water-jet laser processing is an internationally advanced technique, which combines the advantages of laser processing with water jet cutting. In the study, the experiment of water-jet laser dicing are conducted with ns pulsed laser of 1064 nm irradiating, and Smooth Particle Hydrodynamic (SPH) technique by AUTODYN software was modeled to research the fluid dynamics of water and melt when water jet impacting molten material. The silicon surface morphology of the irradiated spots has an appearance as one can see in porous formation. The surface morphology exhibits a large number of cavities which indicates as bubble nucleation sites. The observed surface morphology shows that the explosive melt expulsion could be a dominant process for the laser ablating silicon in liquids with nanosecond pulse laser of 1064 nm irradiating. Self-focusing phenomenon was found and its causes are analyzed. Smooth Particle Hydrodynamic (SPH) modeling technique was employed to understand the effect of water and water-jet on debris removal during water-jet laser machining.

CFD Application to Flow-Accelerated Corrosion in Feeder Bends

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pietralik, John M.; Smith, Bruce A.W.

2006-07-01

Feeder piping in CANDU{sup R} plants experiences a thinning degradation mechanism called Flow-Accelerated Corrosion (FAC). The piping is made of carbon steel and has high water flow speeds. Although the water chemistry is highly alkaline with room-temperature pH in a range of 10.0-10.5, the piping has FAC rates exceeding 0.1 mm/year in some locations, e.g., in bends. One of the most important parameters affecting the FAC rate is the mass transfer coefficient for convective mass transport of ferrous ions. The ions are created at the pipe wall as a result of corrosion, diffuse through the oxide layer, and are transportedmore » from the oxide-layer/water interface to the bulk water by mass transport. Consequently, the local flow characteristics contribute to the highly turbulent convective mass transfer. Plant data and laboratory experiments indicate that the mass transfer step dominates FAC under feeder conditions. In this study, the flow and mass transfer in a feeder bend under operating conditions were simulated using the Fluent{sup TM} computer code. Because the flow speed is very high, with the Reynolds numbers in a range of several millions, and because the geometry is complex, experiments in a 1:1 scale were conducted with the main objective to validate flow simulations. The experiments measured pressure at several key locations and visualized the flow. The flow and mass transfer models were validated using available friction-factor and mass transfer correlations and literature experiments on mass transfer in a bend. The validation showed that the turbulence model that best predicts the experiments is the realizable k-{epsilon} model. Other two-equation turbulence models, as well as one-equation models and Reynolds stress models were tried. The near-wall treatment used the non-equilibrium wall functions. The wall functions were modified for surface roughness when necessary. A comparison of the local mass transfer coefficient with measured FAC rate in plant specimens shows very good agreement. Visualization experiments indicate secondary flows in the bends. No boundary layer separation was observed in experiments or in simulations. (authors)« less

Laboratory Scale Experiments and Numerical Modeling of Cosolvent flushing of NAPL Mixtures in Saturated Porous Media

NASA Astrophysics Data System (ADS)

Agaoglu, B.; Scheytt, T. J.; Copty, N. K.

2011-12-01

This study examines the mechanistic processes governing multiphase flow of a water-cosolvent-NAPL system in saturated porous media. Laboratory batch and column flushing experiments were conducted to determine the equilibrium properties of pure NAPL and synthetically prepared NAPL mixtures as well as NAPL recovery mechanisms for different water-ethanol contents. The effect of contact time was investigated by considering different steady and intermittent flow velocities. A modified version of multiphase flow simulator (UTCHEM) was used to compare the multiphase model simulations with the column experiment results. The effect of employing different grid geometries (1D, 2D, 3D), heterogeneity and different initial NAPL saturation configurations were also examined in the model. It is shown that the change in velocity affects the mass transfer rate between phases as well as the ultimate NAPL recovery percentage. The experiments with slow flow rate flushing of pure NAPL and the 3D UTCHEM simulations gave similar effluent concentrations and NAPL cumulative recoveries. The results were less consistent for fast non-equilibrium flow conditions. The dissolution process from the NAPL mixture into the water-ethanol flushing solutions was found to be more complex than dissolution expressions incorporated in the numerical model. The dissolution rate of individual organic compounds (namely Toluene and Benzene) from a mixture NAPL into the ethanol-water flushing solution is found not to correlate with their equilibrium solubility values.The implications of this controlled experimental and modeling study on field cosolvent remediation applications are discussed.

Development of a multicomponent force and moment balance for water tunnel applications, volume 1

NASA Technical Reports Server (NTRS)

Suarez, Carlos J.; Malcolm, Gerald N.; Kramer, Brian R.; Smith, Brooke C.; Ayers, Bert F.

1994-01-01

The principal objective of this research effort was to develop a multicomponent strain gauge balance to measure forces and moments on models tested in flow visualization water tunnels. An internal balance was designed that allows measuring normal and side forces, and pitching, yawing and rolling moments (no axial force). The five-components to applied loads, low interactions between the sections and no hysteresis. Static experiments (which are discussed in this Volume) were conducted in the Eidetics water tunnel with delta wings and a model of the F/A-18. Experiments with the F/A-18 model included a thorough baseline study and investigations of the effect of control surface deflections and of several Forebody Vortex Control (FVC) techniques. Results were compared to wind tunnel data and, in general, the agreement is very satisfactory. The results of the static tests provide confidence that loads can be measured accurately in the water tunnel with a relatively simple multicomponent internal balance. Dynamic experiments were also performed using the balance, and the results are discussed in detail in Volume 2 of this report.

MODELING OF MULTICOMPONENT PERVAPORATION FOR REMOVAL OF VOLATILE ORGANIC COMPOUNDS FROM WATER

EPA Science Inventory

A resistance-in-series model was used to study the pervaporation of multiple volatile organic compounds (VOCs)-water mixtures. Permeation experiments were carried out for four membranes: poly(dimethylsiloxane) (PDMS), polyether-block-polyamides (PEBA), polyurethane (PUR) and sil...

Model for dynamic self-assembled magnetic surface structures

NASA Astrophysics Data System (ADS)

Belkin, M.; Glatz, A.; Snezhko, A.; Aranson, I. S.

2010-07-01

We propose a first-principles model for the dynamic self-assembly of magnetic structures at a water-air interface reported in earlier experiments. The model is based on the Navier-Stokes equation for liquids in shallow water approximation coupled to Newton equations for interacting magnetic particles suspended at a water-air interface. The model reproduces most of the observed phenomenology, including spontaneous formation of magnetic snakelike structures, generation of large-scale vortex flows, complex ferromagnetic-antiferromagnetic ordering of the snake, and self-propulsion of bead-snake hybrids.

Analyzing the Limitations and the Applicability Domain of Water-Sediment Transformation Tests like OECD 308.

PubMed

Ter Horst, Mechteld M S; Koelmans, Albert A

2016-10-04

The assessment of chemical degradation rates from water-sediment experiments like for instance OECD 308 is challenging due to parallel occurrence of processes like degradation, sorption and diffusive transport, at different rates in water and sediment or at their interface. To systematically and quantitatively analyze this limitation, we generated artificial experiment data sets using model simulations and then used these data sets in an inverse modeling exercise to estimate degradation half-lives in water and sediment (DegT50 wat and DegT50 sed ), which then were evaluated against their true values. Results were visualized by chemical space diagrams that identified those substance property combinations for which the OECD 308 test is fundamentally inappropriate. We show that the uncertainty in estimated degradation half-lives in water increases as the process of diffusion to the sediment becomes dominant over degradation in the water. We show that in theory the uncertainty in the estimated DegT50 sed is smaller than the uncertainty in the DegT50 wat . The predictive value of our chemical space diagrams was validated using literature transformation rates and their uncertainties that were inferred from real water-sediment experiments.

Sensitivity of Vadose Zone Water Fluxes to Climate Shifts in Arid Settings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pfletschinger, H.; Prömmel, K.; Schüth, C.

2014-01-01

Vadose zone water fluxes in arid settings are investigated regarding their sensitivity to hydraulic soil parameters and meteorological data. The study is based on the inverse modeling of highly defined soil column experiments and subsequent scenario modeling comparing different climate projections for a defined arid region. In arid regions, groundwater resources are prone to depletion due to excessive water use and little recharge potential. Especially in sand dune areas, groundwater recharge is highly dependent on vadose zone properties and corresponding water fluxes. Nevertheless, vadose zone water fluxes under arid conditions are hard to determine owing to, among other reasons, deepmore » vadose zones with generally low fluxes and only sporadic high infiltration events. In this study, we present an inverse model of infiltration experiments accounting for variable saturated nonisothermal water fluxes to estimate effective hydraulic and thermal parameters of dune sands. A subsequent scenario modeling links the results of the inverse model with projections of a global climate model until 2100. The scenario modeling clearly showed the high dependency of groundwater recharge on precipitation amounts and intensities, whereas temperature increases are only of minor importance for deep infiltration. However, simulated precipitation rates are still affected by high uncertainties in the response to the hydrological input data of the climate model. Thus, higher certainty in the prediction of precipitation pattern is a major future goal for climate modeling to constrain future groundwater management strategies in arid regions.« less

Water injection into vapor- and liquid-dominated reservoirs: Modeling of heat transfer and mass transport

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pruess, K.; Oldenburg, C.; Moridis, G.

1997-12-31

This paper summarizes recent advances in methods for simulating water and tracer injection, and presents illustrative applications to liquid- and vapor-dominated geothermal reservoirs. High-resolution simulations of water injection into heterogeneous, vertical fractures in superheated vapor zones were performed. Injected water was found to move in dendritic patterns, and to experience stronger lateral flow effects than predicted from homogeneous medium models. Higher-order differencing methods were applied to modeling water and tracer injection into liquid-dominated systems. Conventional upstream weighting techniques were shown to be adequate for predicting the migration of thermal fronts, while higher-order methods give far better accuracy for tracer transport.more » A new fluid property module for the TOUGH2 simulator is described which allows a more accurate description of geofluids, and includes mineral dissolution and precipitation effects with associated porosity and permeability change. Comparisons between numerical simulation predictions and data for laboratory and field injection experiments are summarized. Enhanced simulation capabilities include a new linear solver package for TOUGH2, and inverse modeling techniques for automatic history matching and optimization.« less

Investigation of the behavior of VOCs in ground water across fine- and coarse-grained geological contacts using a medium-scale physical model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoffman, F.; Chiarappa, M.L.

1998-03-01

One of the serious impediments to the remediation of ground water contaminated with volatile organic compounds (VOCs) is that the VOCs are retarded with respect to the movement of the ground water. Although the processes that result in VOC retardation are poorly understood, we have developed a conceptual model that includes several retarding mechanisms. These include adsorption to inorganic surfaces, absorption to organic carbon, and diffusion into areas of immobile waters. This project was designed to evaluate the relative contributions of these mechanisms; by improving our understanding, we hope to inspire new remediation technologies or approaches. Our project consisted ofmore » a series of column experiments designed to measure the retardation, in different geological media, of four common ground water VOCs (chloroform, carbon tetrachloride, trichloroethylene, and tetrachloroethylene) which have differing physical and chemical characteristics. It also included a series of diffusion parameters that constrain the model, we compared the data from these experiments to the output of a computational model.« less

Modeling SST gradient changes, the hydrological cycle response, and deep water formation in the North Pacific

NASA Astrophysics Data System (ADS)

Burls, N.; Ford, H. L.; Fedorov, A. V.; Jahn, A.; Jacobs, P.

2017-12-01

The absence of deep-water formation and a deep meridional overturning cell in the modern North Pacific has been attributed to the relatively fresh surface conditions in the subarctic. These conditions are, in turn, best explained by the local excess of precipitation over evaporation in the northern Pacific due to net moisture transport from the Atlantic to the Pacific and/or moisture transport associated with the Asian monsoon. Some studies link the lack of deep-water formation in the Pacific directly to its occurrence in the Atlantic via the Atlantic-Pacific seesaw effect and idealized experiments indicate that the smaller width of the Atlantic predisposes it to higher salinity and deep-water formation. We have conducted a series of coupled model experiments across which global mean temperatures and large-scale meridional SST gradients are varied. We perturb either atmospheric CO2 concentrations or the meridional gradient in cloud radiative forcing and run each experiment out to 3000 years so that the deep ocean has equilibrated. As the strength of the meridional temperature gradient decreases across our experiments, a Pacific Meridional Overturning Circulation develops. The strength of this Pacific Meridional Overturning Circulation generally increases as the gradient weakens. In one of these experiments where the meridional SST gradient most closely resembles Pliocene reconstructions, a PMOC exists of comparable in strength to the modern AMOC. We will describe how the hydrological cycle response to reduced meridional SST gradients acts to increase the strength of the PMOC across our sensitivity experiments. Additionally, we will discuss our effort to include carbon isotopes in our Pliocene-like simulation for data-model comparisons. Calcium carbonate accumulation data from Subarctic North Pacific Site 882 and new and previously published carbon isotope records from the Pacific appear to support our modelling results suggesting that weaker meridonal SST gradients during the Pliocene could have supported deep water formation in the subarctic Pacific and a strong PMOC.

Assay of the Martian Regolith with Neutrons

NASA Technical Reports Server (NTRS)

Drake, Darrell M.

1997-01-01

The purpose of the research is to combine experiments and Monte Carlo transport of neutrons through volume of soil in an attempt to model neutron leakage from planetary surfaces. Emphasis is given to the change of neutron spectra as a function of water content and location. During the first stage of effort, two experiments were conducted in which leakage of neutrons from a Pu-Be source through about 30 g/cm(exp 2) of soil were measured with several counters. A Monte Carlo code, MCNP, has been used to model many of the 100 individual runs of the experiment. Hydrogen is the element that has the most dramatic effect on the neutron spectrum and its effect on the neutron spectrum is almost the same whether it is in the form of water or polyethylene. In order to simulate various water configurations, sheets of polyethylene have been used between layers of soil as well as water in several concentrations up to 18%. Comparison of experimental results to theoretical predictions made with the MCNP code were disappointing for low concentrations of water. We have made extensive calculations to see if room return could be the cause of the discrepancies. Water concentrations of the 'dry' soil were measured by two different laboratories and differed only by 0.5%. We have made calculations to optimize the next experiment and are investigating other methods of determining the water content of 'dry' soil.

A simple analytical infiltration model for short-duration rainfall

NASA Astrophysics Data System (ADS)

Wang, Kaiwen; Yang, Xiaohua; Liu, Xiaomang; Liu, Changming

2017-12-01

Many infiltration models have been proposed to simulate infiltration process. Different initial soil conditions and non-uniform initial water content can lead to infiltration simulation errors, especially for short-duration rainfall (SHR). Few infiltration models are specifically derived to eliminate the errors caused by the complex initial soil conditions. We present a simple analytical infiltration model for SHR infiltration simulation, i.e., Short-duration Infiltration Process model (SHIP model). The infiltration simulated by 5 models (i.e., SHIP (high) model, SHIP (middle) model, SHIP (low) model, Philip model and Parlange model) were compared based on numerical experiments and soil column experiments. In numerical experiments, SHIP (middle) and Parlange models had robust solutions for SHR infiltration simulation of 12 typical soils under different initial soil conditions. The absolute values of percent bias were less than 12% and the values of Nash and Sutcliffe efficiency were greater than 0.83. Additionally, in soil column experiments, infiltration rate fluctuated in a range because of non-uniform initial water content. SHIP (high) and SHIP (low) models can simulate an infiltration range, which successfully covered the fluctuation range of the observed infiltration rate. According to the robustness of solutions and the coverage of fluctuation range of infiltration rate, SHIP model can be integrated into hydrologic models to simulate SHR infiltration process and benefit the flood forecast.

Multi-Periodic Waves in Shallow Water

DTIC Science & Technology

1992-09-01

models-the Kadomtsev - Petviashvili (KP) equation . The KP equation describes the evolu- tion of weakly nonlinear, weakly two-dimensional waves on water of...experimentally. The analytical model is a family of periodic solutions of the Kadomtsev -Petviashuili equation . The experiments demonstrate the accuracy... Petviashvili Equation (with Norman Schef- fner & Harvey Segur). Proceedings, Nonlinear Water Waves Workshop, University of Bristol. England, 1991. Resonant

Inspiring a Broader Socio-Hydrological Negotiation Approach With Interdisciplinary Field-Based Experience

NASA Astrophysics Data System (ADS)

Massuel, S.; Riaux, J.; Molle, F.; Kuper, M.; Ogilvie, A.; Collard, A.-L.; Leduc, C.; Barreteau, O.

2018-04-01

Socio-hydrology advanced the field of hydrology by considering humans and their activities as part of the water cycle, rather than as external drivers. Models are used to infer reproducible trends in human interactions with water resources. However, defining and handling water problems in this way may restrict the scope of such modeling approaches. We propose an interdisciplinary socio-hydrological approach to overcome this limit and complement modeling approaches. It starts from concrete field-based situations, combines disciplinary as well as local knowledge on water-society relationships, with the aim of broadening the hydrocentric analysis and modeling of water systems. The paper argues that an analysis of social dynamics linked to water is highly complementary to traditional hydrological tools but requires a negotiated and contextualized interdisciplinary approach to the representation and analysis of socio-hydro systems. This reflection emerged from experience gained in the field where a water-budget modeling framework failed to adequately incorporate the multiplicity of (nonhydrological) factors that determine the volumes of withdrawals for irrigation. The pathway subsequently explored was to move away from the hydrologic view of the phenomena and, in collaboration with social scientists, to produce a shared conceptualization of a coupled human-water system through a negotiated approach. This approach changed the way hydrological research issues were addressed and limited the number of strong assumptions needed for simplification in modeling. The proposed socio-hydrological approach led to a deeper understanding of the mechanisms behind local water-related problems and to debates on the interactions between social and political decisions and the dynamics of these problems.

Heterogeneity and scaling land-atmospheric water and energy fluxes in climate systems

NASA Technical Reports Server (NTRS)

Wood, Eric F.

1993-01-01

The effects of small-scale heterogeneity in land surface characteristics on the large-scale fluxes of water and energy in land-atmosphere system has become a central focus of many of the climatology research experiments. The acquisition of high resolution land surface data through remote sensing and intensive land-climatology field experiments (like HAPEX and FIFE) has provided data to investigate the interactions between microscale land-atmosphere interactions and macroscale models. One essential research question is how to account for the small scale heterogeneities and whether 'effective' parameters can be used in the macroscale models. To address this question of scaling, three modeling experiments were performed and are reviewed in the paper. The first is concerned with the aggregation of parameters and inputs for a terrestrial water and energy balance model. The second experiment analyzed the scaling behavior of hydrologic responses during rain events and between rain events. The third experiment compared the hydrologic responses from distributed models with a lumped model that uses spatially constant inputs and parameters. The results show that the patterns of small scale variations can be represented statistically if the scale is larger than a representative elementary area scale, which appears to be about 2 - 3 times the correlation length of the process. For natural catchments this appears to be about 1 - 2 sq km. The results concerning distributed versus lumped representations are more complicated. For conditions when the processes are nonlinear, then lumping results in biases; otherwise a one-dimensional model based on 'equivalent' parameters provides quite good results. Further research is needed to fully understand these conditions.

A comparative modeling study of a dual tracer experiment in a large lysimeter under atmospheric conditions

NASA Astrophysics Data System (ADS)

Stumpp, C.; Nützmann, G.; Maciejewski, S.; Maloszewski, P.

2009-09-01

SummaryIn this paper, five model approaches with different physical and mathematical concepts varying in their model complexity and requirements were applied to identify the transport processes in the unsaturated zone. The applicability of these model approaches were compared and evaluated investigating two tracer breakthrough curves (bromide, deuterium) in a cropped, free-draining lysimeter experiment under natural atmospheric boundary conditions. The data set consisted of time series of water balance, depth resolved water contents, pressure heads and resident concentrations measured during 800 days. The tracer transport parameters were determined using a simple stochastic (stream tube model), three lumped parameter (constant water content model, multi-flow dispersion model, variable flow dispersion model) and a transient model approach. All of them were able to fit the tracer breakthrough curves. The identified transport parameters of each model approach were compared. Despite the differing physical and mathematical concepts the resulting parameters (mean water contents, mean water flux, dispersivities) of the five model approaches were all in the same range. The results indicate that the flow processes are also describable assuming steady state conditions. Homogeneous matrix flow is dominant and a small pore volume with enhanced flow velocities near saturation was identified with variable saturation flow and transport approach. The multi-flow dispersion model also identified preferential flow and additionally suggested a third less mobile flow component. Due to high fitting accuracy and parameter similarity all model approaches indicated reliable results.

Isotopic fractionation of gases during its migration: experiments and 2D numerical simulation

NASA Astrophysics Data System (ADS)

Kara, S.; Prinzhofer, A.

2003-04-01

Several works have been developed in the last decade on the experimental isotope fractionation of gases during migration (Prinzhofer et al., 1997 and Zhang &Krooss, 2001 among others). We add to these results new experiments on diffusion of CO_2, which becomes currently a crucial subject for environmental purpose. Our experiments showed that transport by diffusion of CO_2 through a water saturated shale induces a significant and systematic carbon isotopic fractionation with heavier (13C enriched) CO_2 migrating first. In all experiments, significant isotope fractionation was found but still remains without quantitative interpretation. To interpret these data, we developed a 2D numerical model at the pore scale. The general principle of this model is the study of transport by water solubilization/diffusion of gas in a capillary saturated with water with two different media : a mobile zone representing free water and a immobile zone representing bounded water. The model takes also into account solubilization coefficients of gas in water, as well as the migration distance and the volume of upstream and downstream reservoirs. Using our numerical model, we could reproduce the evolution of isotopic fractionations and the velocity of CO_2 migration versus the production factor F (proportion of diffused gas). We determined some physical parameters of the porous medium (bentonite) which are not directly measurable at the present time. Furthermore, we used these parameters to reproduce the curves of isotopic fractionation obtained by Pernaton (1998) on methane migration with the same porous rock. We used also a modified version of this model with infinite reservoirs to reproduce the curves of isotopic fractionation of Zhang &Krooss (2001). Application of this model to geological scale is under progress, in order to implement it into sedimentary basins modelling. REFERENCES: Zhang T. and Krooss M. (2001). Geochim. Cosmochim. Acta, Vol. 65, No.16, pp. 2723-2742. Pernaton E. (1998) PhD. Thesis, Université de Paris VII, 272 pp. Prinzhofer A. and Pernaton E. (1997) Chem. Geol., vol. 142, 193-200.

A mass-balance code for the quantitative interpretation of fluid column profiles in ground-water studies

NASA Astrophysics Data System (ADS)

Paillet, Frederick

2012-08-01

A simple mass-balance code allows effective modeling of conventional fluid column resistivity logs in dilution tests involving column replacement with either distilled water or dilute brine. Modeling a series of column profiles where the inflowing formation water introduces water quality interfaces propagating along the borehole gives effective estimates of the rate of borehole flow. Application of the dilution model yields estimates of borehole flow rates that agree with measurements made with the heat-pulse flowmeter under ambient and pumping conditions. Model dilution experiments are used to demonstrate how dilution logging can extend the range of borehole flow measurement at least an order of magnitude beyond that achieved with flowmeters. However, dilution logging has the same dynamic range limitation encountered with flowmeters because it is difficult to detect and characterize flow zones that contribute a small fraction of total flow when that contribution is superimposed on a larger flow. When the smaller contribution is located below the primary zone, ambient downflow may disguise the zone if pumping is not strong enough to reverse the outflow. This situation can be addressed by increased pumping. But this is likely to make the moveout of water quality interfaces too fast to measure in the upper part of the borehole, so that a combination of flowmeter and dilution method may be more appropriate. Numerical experiments show that the expected weak horizontal flow across the borehole at conductive zones would be almost impossible to recognize if any ambient vertical flow is present. In situations where natural water quality differences occur such as flowing boreholes or injection experiments, the simple mass-balance code can be used to quantitatively model the evolution of fluid column logs. Otherwise, dilution experiments can be combined with high-resolution flowmeter profiles to obtain results not attainable using either method alone.

Confined water: a Mercedes-Benz model study.

PubMed

Urbic, T; Vlachy, V; Dill, K A

2006-03-16

We study water that is confined within small geometric spaces. We use the Mercedes-Benz (MB) model of water, in NVT and muVT Monte Carlo computer simulations. For MB water molecules between two planes separated by a distance d, we explore the structures, hydrogen bond networks, and thermodynamics as a function of d, temperature T, and water chemical potential mu. We find that squeezing the planes close enough together leads to a vaporization of waters out of the cavity. This vaporization transition has a corresponding peak in the heat capacity of the water. We also find that, in small pores, hydrogen bonding is not isotropic but, rather, it preferentially forms chains along the axis of the cavity. This may be relevant for fast proton transport in pores. Our simulations show oscillations in the forces between the inert plates, due to water structure, even for plate separations of 5-10 water diameters, consistent with experiments by Israelachvili et al. [Nature 1983, 306, 249]. Finally, we find that confinement affects water's heat capacity, consistent with recent experiments of Tombari et al. on Vycor nanopores [J. Chem. Phys. 2005, 122, 104712].

Chlorinated Cyanurates: Method Interferences and Application Implications

EPA Science Inventory

Experiments were conducted to investigate method interferences, residual stability, regulated DBP formation, and a water chemistry model associated with the use of Dichlor & Trichlor in drinking water.

Modeling the effects of throughfall reduction on soil water content in a Brazilian Oxisol under a moist tropical forest

NASA Astrophysics Data System (ADS)

Belk, Elizabeth L.; Markewitz, Daniel; Rasmussen, Todd C.; Carvalho, Eduardo J. Maklouf; Nepstad, Daniel C.; Davidson, Eric A.

2007-08-01

Access to water reserves in deep soil during drought periods determines whether or not the tropical moist forests of Amazonia will be buffered from the deleterious effects of water deficits. Changing climatic conditions are predicted to increase periods of drought in Amazonian forests and may lead to increased tree mortality, changes in forest composition, or greater susceptibility to fire. A throughfall reduction experiment has been established in the Tapajós National Forest of east-central Amazonia (Brazil) to test the potential effects of severe water stress during prolonged droughts. Using time domain reflectometry observations of water contents from this experiment, we have developed a dynamic, one-dimensional, vertical flow model to enhance our understanding of hydrologic processes within these tall-stature forests on well-drained, upland, deep Oxisols and to simulate changes in the distribution of soil water. Simulations using 960 days of data accurately captured mild soil water depletion near the surface after the first treatment year and decreasing soil moisture at depth during the second treatment year. The model is sensitive to the water retention and unsaturated flow equation parameters, specifically the van Genuchten parameters θs, θr, and n, but less sensitive to Ks and α. The low root-mean-square error between observed and predicted volumetric soil water content suggests that this vertical flow model captures the most important hydrologic processes in the upper landscape position of this study site. The model indicates that present rates of evapotranspiration within the exclusion plot have been sustained at the expense of soil water storage.

Hollow-Fiber Cartridges: Model Systems for Virus Removal from Blood

NASA Astrophysics Data System (ADS)

Jacobitz, Frank; Menon, Jeevan

2005-11-01

Aethlon Medical is developing a hollow-fiber hemodialysis device designed to remove viruses and toxins from blood. Possible target viruses include HIV and pox-viruses. The filter could reduce virus and viral toxin concentration in the patient's blood, delaying illness so the patient's immune system can fight off the virus. In order to optimize the design of such a filter, the fluid mechanics of the device is both modeled analytically and investigated experimentally. The flow configuration of the proposed device is that of Starling flow. Polysulfone hollow-fiber dialysis cartridges were used. The cartridges are charged with water as a model fluid for blood and fluorescent latex beads are used in the experiments as a model for viruses. In the experiments, properties of the flow through the cartridge are determined through pressure and volume flow rate measurements of water. The removal of latex beads, which are captured in the porous walls of the fibers, was measured spectrophotometrically. Experimentally derived coefficients derived from these experiments are used in the analytical model of the flow and removal predictions from the model are compared to those obtained from the experiments.

Vibrational spectroscopy of water at interfaces

PubMed Central

Skinner, J. L.; Pieniazek, P. A.; Gruenbaum, S. M.

2011-01-01

Conspectus Recent experimental advances in vibrational spectroscopy, such as ultrafast pulses and heterodyne detection, have made it possible to probe the structure and dynamics of bulk and interfacial water in unprecedented detail. We consider three aqueous interfaces: the water liquid/vapor interface, the interface between water and the surfactant headgroups of reverse micelles, and the interface between water and the lipid headgroups of aligned multi-bilayers. In the first case, sum-frequency spectroscopy is used to probe the interface, while in the second and third cases, the confined water pools are sufficiently small that techniques of bulk spectroscopy such as FTIR, pump-probe, 2DIR, etc. can be used to probe the interfacial water. In this review, we discuss our attempts to model these three systems and interpret the existing experiments. In particular, for the water liquid/vapor interface we find that three-body interactions are essential for reproducing the experimental sum-frequency spectrum, and presumably for the structure of the interface as well. The observed spectrum is interpreted as arising from overlapping and cancelling positive and negative contributions from molecules in different hydrogen-bonding environments. For the reverse micelles, our theoretical models confirm that the experimentally observed blue shift of the water OD stretch (for dilute HOD in H2O) arises from weaker hydrogen bonding to sulfonate oxygens. We interpret the observed slow-down in water rotational dynamics as arising from curvature-induced frustration. For the water confined between lipid bilayers, our theoretical models confirm that the experimentally observed red shift of the water OD stretch arises from stronger hydrogen bonding to phosphate oxygens. We develop a model for heterogeneous vibrational lifetime distributions, and implement the model to calculate isotropic and anisotropic pump-probe decays, and compare with experiment. PMID:22032305

Keeping warm with fur in cold water: entrainment of air in hairy surfaces

NASA Astrophysics Data System (ADS)

Nasto, Alice; Regli, Marianne; Brun, Pierre-Thomas; Clanet, Christophe; Hosoi, Anette

2015-11-01

Instead of relying on a thick layer of body fat for insulation as many aquatic mammals do, fur seals and otters trap air in their dense fur for insulation in cold water. Using a combination of model experiments and theory, we rationalize this mechanism of air trapping underwater for thermoregulation. For the model experiments, hairy surfaces are fabricated using laser cut molds and casting samples with PDMS. Modeling the hairy texture as a network of capillary tubes, the imbibition speed of water into the hairs is obtained through a balance of hydrostatic pressure and viscous stress. In this scenario, the bending of the hairs and capillary forces are negligible. The maximum diving depth that can be achieved before the hairs are wetted to the roots is predicted from a comparison of the diving speed and imbibition speed. The amount of air that is entrained in hairy surfaces is greater than what is expected for classic Landau-Levich-Derjaguin plate plunging. A phase diagram with the parameters from experiments and biological data allows a comparison of the model system and animals.

Development of a 5-Component Balance for Water Tunnel Applications

NASA Technical Reports Server (NTRS)

Suarez, Carlos J.; Kramer, Brian R.; Smith, Brooke C.

1999-01-01

The principal objective of this research/development effort was to develop a multi-component strain gage balance to measure both static and dynamic forces and moments on models tested in flow visualization water tunnels. A balance was designed that allows measuring normal and side forces, and pitching, yawing and rolling moments (no axial force). The balance mounts internally in the model and is used in a manner typical of wind tunnel balances. The key differences between a water tunnel balance and a wind tunnel balance are the requirement for very high sensitivity since the loads are very low (typical normal force is 90 grams or 0.2 lbs), the need for water proofing the gage elements, and the small size required to fit into typical water tunnel models. The five-component balance was calibrated and demonstrated linearity in the responses of the primary components to applied loads, very low interactions between the sections and no hysteresis. Static experiments were conducted in the Eidetics water tunnel with delta wings and F/A-18 models. The data were compared to forces and moments from wind tunnel tests of the same or similar configurations. The comparison showed very good agreement, providing confidence that loads can be measured accurately in the water tunnel with a relatively simple multi-component internal balance. The success of the static experiments encouraged the use of the balance for dynamic experiments. Among the advantages of conducting dynamic tests in a water tunnel are less demanding motion and data acquisition rates than in a wind tunnel test (because of the low-speed flow) and the capability of performing flow visualization and force/moment (F/M) measurements simultaneously with relative simplicity. This capability of simultaneous flow visualization and for F/M measurements proved extremely useful to explain the results obtained during these dynamic tests. In general, the development of this balance should encourage the use of water tunnels for a wider range of quantitative and qualitative experiments, especially during the preliminary phase of aircraft design.

Pollutant dispersion in a large indoor space: Part 1 -- Scaled experiments using a water-filled model with occupants and furniture.

PubMed

Thatcher, T L; Wilson, D J; Wood, E E; Craig, M J; Sextro, R G

2004-08-01

Scale modeling is a useful tool for analyzing complex indoor spaces. Scale model experiments can reduce experimental costs, improve control of flow and temperature conditions, and provide a practical method for pretesting full-scale system modifications. However, changes in physical scale and working fluid (air or water) can complicate interpretation of the equivalent effects in the full-scale structure. This paper presents a detailed scaling analysis of a water tank experiment designed to model a large indoor space, and experimental results obtained with this model to assess the influence of furniture and people in the pollutant concentration field at breathing height. Theoretical calculations are derived for predicting the effects from losses of molecular diffusion, small scale eddies, turbulent kinetic energy, and turbulent mass diffusivity in a scale model, even without Reynolds number matching. Pollutant dispersion experiments were performed in a water-filled 30:1 scale model of a large room, using uranine dye injected continuously from a small point source. Pollutant concentrations were measured in a plane, using laser-induced fluorescence techniques, for three interior configurations: unobstructed, table-like obstructions, and table-like and figure-like obstructions. Concentrations within the measurement plane varied by more than an order of magnitude, even after the concentration field was fully developed. Objects in the model interior had a significant effect on both the concentration field and fluctuation intensity in the measurement plane. PRACTICAL IMPLICATION: This scale model study demonstrates both the utility of scale models for investigating dispersion in indoor environments and the significant impact of turbulence created by furnishings and people on pollutant transport from floor level sources. In a room with no furniture or occupants, the average concentration can vary by about a factor of 3 across the room. Adding furniture and occupants can increase this spatial variation by another factor of 3.

Phase transitions and dynamics of bulk and interfacial water.

PubMed

Franzese, G; Hernando-Martínez, A; Kumar, P; Mazza, M G; Stokely, K; Strekalova, E G; de los Santos, F; Stanley, H E

2010-07-21

New experiments on water at the surface of proteins at very low temperature display intriguing dynamic behaviors. The extreme conditions of these experiments make it difficult to explore the wide range of thermodynamic state points needed to offer a suitable interpretation. Detailed simulations suffer from the same problem, where equilibration times at low temperature become extremely long. We show how Monte Carlo simulations and mean field calculations using a tractable model of water help interpret the experimental results. Here we summarize the results for bulk water and investigate the thermodynamic and dynamic properties of supercooled water at an interface.

[A review on research of land surface water and heat fluxes].

PubMed

Sun, Rui; Liu, Changming

2003-03-01

Many field experiments were done, and soil-vegetation-atmosphere transfer(SVAT) models were stablished to estimate land surface heat fluxes. In this paper, the processes of experimental research on land surface water and heat fluxes are reviewed, and three kinds of SVAT model(single layer model, two layer model and multi-layer model) are analyzed. Remote sensing data are widely used to estimate land surface heat fluxes. Based on remote sensing and energy balance equation, different models such as simplified model, single layer model, extra resistance model, crop water stress index model and two source resistance model are developed to estimate land surface heat fluxes and evapotranspiration. These models are also analyzed in this paper.

Deep and intermediate mediterranean water in the western Alboran Sea

NASA Astrophysics Data System (ADS)

Parrilla, Gregorio; Kinder, Thomas H.; Preller, Ruth H.

1986-01-01

Hydrographic and current meter data, obtained during June to October 1982, and numerical model experiments are used to study the distribution and flow of Mediterranean waters in the western Alboran Sea. The Intermediate Water is more pronounced in the northern three-fourths of the sea, but its distribution is patchy as manifested by variability of the temperature and salinity maxima at scales ≤10 km. Current meters in the lower Intermediate Water showed mean flow toward the Strait at 2 cm s -1. A reversal of this flow lasted about 2 weeks. A rough estimate of the mean westward Intermediate Water transport was 0.4 × 10 6 m 3 s -1, about one-third of the total outflow, so that the best estimates of the contributions of traditionally defined Intermediate Water and Deep Water account for only about one-half of the total outflow. The Deep Water was uplifted against the southern continental slope from Alboran Island (3°W) to the Strait. There was also a similar but much weaker banking against the Spanish slope, but a deep current record showed that the eastward recirculation implied by this banking is probably intermittent. Two-layer numerical model experiments simulated the Intermediate Water flow with a flat bottom and the Deep Water with realistic bottom topography. Both experiments replicated the major circulation features, and the Intermediate Water flow was concentrated in the north because of rotation and the Deep Water flow in the south because of topographic control.

Experimentally Modeling Black and White Hole Event Horizons via Fluid Flow

NASA Astrophysics Data System (ADS)

Manheim, Marc E.; Lindner, John F.; Manz, Niklas

We will present a scaled down experiment that hydrodynamically models the interaction between electromagnetic waves and black/white holes. It has been mathematically proven that gravity waves in water can behave analogously to electromagnetic waves traveling through spacetime. In this experiment, gravity waves will be generated in a water tank and propagate in a direction opposed to a flow of varying rate. We observe a noticeable change in the wave's spreading behavior as it travels through the simulated horizon with decreased wave speeds up to standing waves, depending on the opposite flow rate. Such an experiment has already been performed in a 97.2 cubic meter tank. We reduced the size significantly to be able to perform the experiment under normal lab conditions.

Laboratory-scale experiments and numerical modeling of cosolvent flushing of multi-component NAPLs in saturated porous media

NASA Astrophysics Data System (ADS)

Agaoglu, Berken; Scheytt, Traugott; Copty, Nadim K.

2012-10-01

This study examines the mechanistic processes governing multiphase flow of a water-cosolvent-NAPL system in saturated porous media. Laboratory batch and column flushing experiments were conducted to determine the equilibrium properties of pure NAPL and synthetically prepared NAPL mixtures as well as NAPL recovery mechanisms for different water-ethanol contents. The effect of contact time was investigated by considering different steady and intermittent flow velocities. A modified version of multiphase flow simulator (UTCHEM) was used to compare the multiphase model simulations with the column experiment results. The effect of employing different grid geometries (1D, 2D, 3D), heterogeneity and different initial NAPL saturation configurations was also examined in the model. It is shown that the change in velocity affects the mass transfer rate between phases as well as the ultimate NAPL recovery percentage. The experiments with low flow rate flushing of pure NAPL and the 3D UTCHEM simulations gave similar effluent concentrations and NAPL cumulative recoveries. Model simulations over-estimated NAPL recovery for high specific discharges and rate-limited mass transfer, suggesting a constant mass transfer coefficient for the entire flushing experiment may not be valid. When multi-component NAPLs are present, the dissolution rate of individual organic compounds (namely, toluene and benzene) into the ethanol-water flushing solution is found not to correlate with their equilibrium solubility values.

Short-term Operation of Multi-purpose Reservoir using Model Predictive Control

NASA Astrophysics Data System (ADS)

Uysal, Gokcen; Schwanenberg, Dirk; Alvarado Montero, Rodolfo; Sensoy, Aynur; Arda Sorman, Ali

2017-04-01

Operation of water structures especially with conflicting water supply and flood mitigation objectives is under more stress attributed to growing water demand and changing hydro-climatic conditions. Model Predictive Control (MPC) based optimal control solutions has been successfully applied to different water resources applications. In this study, Feedback Control (FBC) and MPC get combined and an improved joint optimization-simulation operating scheme is proposed. Water supply and flood control objectives are fulfilled by incorporating the long term water supply objectives into a time-dependent variable guide curve policy whereas the extreme floods are attenuated by means of short-term optimization based on MPC. A final experiment is carried out to assess the lead time performance and reliability of forecasts in a hindcasting experiment with imperfect, perturbed forecasts. The framework is tested in Yuvacık Dam reservoir where the main water supply reservoir of Kocaeli City in the northwestern part of Turkey (the Marmara region) and it requires a challenging gate operation due to restricted downstream flow conditions.

Lithium levels in tap water and psychotic experiences in a general population of adolescents.

PubMed

Shimodera, Shinji; Koike, Shinsuke; Ando, Shuntaro; Yamasaki, Syudo; Fujito, Ryosuke; Endo, Kaori; Iijima, Yudai; Yamamoto, Yu; Morita, Masaya; Sawada, Ken; Ohara, Nobuki; Okazaki, Yuji; Nishida, Atsushi

2018-06-09

Recently, several epidemiologic studies have reported that lithium in drinking water may be associated with lower rates of suicide mortality, lower incidence of dementia, and lower levels of adolescents' depression and aggression at the population level. However, to our knowledge, no study has investigated lithium level in tap water in relation to psychotic experiences in a general population of adolescents. This is the first study to investigate this using a large dataset. Information on psychotic experiences, distress associated with these experiences, and depressive symptoms were collected in 24 public junior high schools in Kochi Prefecture in Japan. Samples were collected from sources that supplied drinking water to schools, and lithium levels were measured using atomic absorption spectrophotometry. The association of lithium levels with psychotic experiences, considering distress as a degree of severity, was examined using an ordinal logistic regression model with schools and depressive symptoms as random effects. In total, 3040 students responded to the self-reporting questionnaire (response rate: 91.8%). Lithium levels in tap water were inversely associated with psychotic experiences (p = 0.021). We concluded that lithium level in tap water was inversely associated with psychotic experiences among a general population of adolescents and may have a preventive effect for such experiences and distress. Copyright © 2018 Elsevier B.V. All rights reserved.

Applying a health behavior theory to explore the influence of information and experience on arsenic risk representations, policy beliefs, and protective behavior.

PubMed

Severtson, Dolores J; Baumann, Linda C; Brown, Roger L

2006-04-01

The common sense model (CSM) shows how people process information to construct representations, or mental models, that guide responses to health threats. We applied the CSM to understand how people responded to information about arsenic-contaminated well water. Constructs included external information (arsenic level and information use), experience (perceived water quality and arsenic-related health effects), representations, safety judgments, opinions about policies to mitigate environmental arsenic, and protective behavior. Of 649 surveys mailed to private well users with arsenic levels exceeding the maximum contaminant level, 545 (84%) were analyzed. Structural equation modeling quantified CSM relationships. Both external information and experience had substantial effects on behavior. Participants who identified a water problem were more likely to reduce exposure to arsenic. However, about 60% perceived good water quality and 60% safe water. Participants with higher arsenic levels selected higher personal safety thresholds and 20% reported a lower arsenic level than indicated by their well test. These beliefs would support judgments of safe water. A variety of psychological and contextual factors may explain judgments of safe water when information suggested otherwise. Information use had an indirect effect on policy beliefs through understanding environmental causes of arsenic. People need concrete information about environmental risk at both personal and environmental-systems levels to promote a comprehensive understanding and response. The CSM explained responses to arsenic information and may have application to other environmental risks.

Predictability and Quantification of Complex Groundwater Table Dynamics Driven by Irregular Surface Water Fluctuations

NASA Astrophysics Data System (ADS)

Xin, Pei; Wang, Shen S. J.; Shen, Chengji; Zhang, Zeyu; Lu, Chunhui; Li, Ling

2018-03-01

Shallow groundwater interacts strongly with surface water across a quarter of global land area, affecting significantly the terrestrial eco-hydrology and biogeochemistry. We examined groundwater behavior subjected to unimodal impulse and irregular surface water fluctuations, combining physical experiments, numerical simulations, and functional data analysis. Both the experiments and numerical simulations demonstrated a damped and delayed response of groundwater table to surface water fluctuations. To quantify this hysteretic shallow groundwater behavior, we developed a regression model with the Gamma distribution functions adopted to account for the dependence of groundwater behavior on antecedent surface water conditions. The regression model fits and predicts well the groundwater table oscillations resulting from propagation of irregular surface water fluctuations in both laboratory and large-scale aquifers. The coefficients of the Gamma distribution function vary spatially, reflecting the hysteresis effect associated with increased amplitude damping and delay as the fluctuation propagates. The regression model, in a relatively simple functional form, has demonstrated its capacity of reproducing high-order nonlinear effects that underpin the surface water and groundwater interactions. The finding has important implications for understanding and predicting shallow groundwater behavior and associated biogeochemical processes, and will contribute broadly to studies of groundwater-dependent ecology and biogeochemistry.

Upper Blue Nile basin water budget from a multi-model perspective

NASA Astrophysics Data System (ADS)

Jung, Hahn Chul; Getirana, Augusto; Policelli, Frederick; McNally, Amy; Arsenault, Kristi R.; Kumar, Sujay; Tadesse, Tsegaye; Peters-Lidard, Christa D.

2017-12-01

Improved understanding of the water balance in the Blue Nile is of critical importance because of increasingly frequent hydroclimatic extremes under a changing climate. The intercomparison and evaluation of multiple land surface models (LSMs) associated with different meteorological forcing and precipitation datasets can offer a moderate range of water budget variable estimates. In this context, two LSMs, Noah version 3.3 (Noah3.3) and Catchment LSM version Fortuna 2.5 (CLSMF2.5) coupled with the Hydrological Modeling and Analysis Platform (HyMAP) river routing scheme are used to produce hydrological estimates over the region. The two LSMs were forced with different combinations of two reanalysis-based meteorological datasets from the Modern-Era Retrospective analysis for Research and Applications datasets (i.e., MERRA-Land and MERRA-2) and three observation-based precipitation datasets, generating a total of 16 experiments. Modeled evapotranspiration (ET), streamflow, and terrestrial water storage estimates were evaluated against the Atmosphere-Land Exchange Inverse (ALEXI) ET, in-situ streamflow observations, and NASA Gravity Recovery and Climate Experiment (GRACE) products, respectively. Results show that CLSMF2.5 provided better representation of the water budget variables than Noah3.3 in terms of Nash-Sutcliffe coefficient when considering all meteorological forcing datasets and precipitation datasets. The model experiments forced with observation-based products, the Climate Hazards group Infrared Precipitation with Stations (CHIRPS) and the Tropical Rainfall Measuring Mission (TRMM) Multi-Satellite Precipitation Analysis (TMPA), outperform those run with MERRA-Land and MERRA-2 precipitation. The results presented in this paper would suggest that the Famine Early Warning Systems Network (FEWS NET) Land Data Assimilation System incorporate CLSMF2.5 and HyMAP routing scheme to better represent the water balance in this region.

Hydrothermal germination models: Improving experimental efficiency by limiting data collection to the relevant hydrothermal range

USDA-ARS?s Scientific Manuscript database

Hydrothermal models used to predict germination response in the field are usually parameterized with data from laboratory experiments that examine the full range of germination response to temperature and water potential. Inclusion of low water potential and high and low-temperature treatments, how...

Catalytic wet oxidation: mathematical modeling of multicompound destruction.

PubMed

Yang, J; Hand, D W; Hokanson, D R; Crittenden, J C; Oman, E J

2003-01-01

A mathematical model of a three-phase catalytic reactor, CatReac, was developed for analysis and optimization of a catalytic oxidation reactor that is used in the International Space Station potable water processor. The packed-bed catalytic reactor, known as the volatile reactor assembly (VRA), is operated as a three-phase reactor and contains a proprietary catalyst, a pure-oxygen gas phase, and the contaminated water. The contaminated water being fed to the VRA primarily consists of acetic acid, acetone, ethanol, 1-propanol, 2-propanol, and propionic acid ranging in concentration from 1 to 10 mg/L. The Langmuir-Hinshelwood Hougen-Watson (L-H) (Hougen, 1943) expression was used to describe the surface reaction rate for these compounds. Single and multicompound short-column experiments were used to determine the L-H rate parameters and calibrate the model. The model was able to predict steady-state multicomponent effluent profiles for short and full-scale reactor experiments.

U.S. Geological Survey Groundwater Modeling Software: Making Sense of a Complex Natural Resource

USGS Publications Warehouse

Provost, Alden M.; Reilly, Thomas E.; Harbaugh, Arlen W.; Pollock, David W.

2009-01-01

Computer models of groundwater systems simulate the flow of groundwater, including water levels, and the transport of chemical constituents and thermal energy. Groundwater models afford hydrologists a framework on which to organize their knowledge and understanding of groundwater systems, and they provide insights water-resources managers need to plan effectively for future water demands. Building on decades of experience, the U.S. Geological Survey (USGS) continues to lead in the development and application of computer software that allows groundwater models to address scientific and management questions of increasing complexity.

Evidence from Amazonian forests is consistent with isohydric control of leaf water potential.

PubMed

Fisher, Rosie A; Williams, Mathew; Do Vale, Raquel Lobo; Da Costa, Antonio Lola; Meir, Patrick

2006-02-01

Climate modelling studies predict that the rain forests of the Eastern Amazon basin are likely to experience reductions in rainfall of up to 50% over the next 50-100 years. Efforts to predict the effects of changing climate, especially drought stress, on forest gas exchange are currently limited by uncertainty about the mechanism that controls stomatal closure in response to low soil moisture. At a through-fall exclusion experiment in Eastern Amazonia where water was experimentally excluded from the soil, we tested the hypothesis that plants are isohydric, that is, when water is scarce, the stomata act to prevent leaf water potential from dropping below a critical threshold level. We made diurnal measurements of leaf water potential (psi 1), stomatal conductance (g(s)), sap flow and stem water potential (psi stem) in the wet and dry seasons. We compared the data with the predictions of the soil-plant-atmosphere (SPA) model, which embeds the isohydric hypothesis within its stomatal conductance algorithm. The model inputs for meteorology, leaf area index (LAI), soil water potential and soil-to-leaf hydraulic resistance (R) were altered between seasons in accordance with measured values. No optimization parameters were used to adjust the model. This 'mechanistic' model of stomatal function was able to explain the individual tree-level seasonal changes in water relations (r2 = 0.85, 0.90 and 0.58 for psi 1, sap flow and g(s), respectively). The model indicated that the measured increase in R was the dominant cause of restricted water use during the dry season, resulting in a modelled restriction of sap flow four times greater than that caused by reduced soil water potential. Higher resistance during the dry season resulted from an increase in below-ground resistance (including root and soil-to-root resistance) to water flow.

Porous Media and Mixture Models for Hygrothermal Behavior of Phenolic Composites

NASA Technical Reports Server (NTRS)

Sullivan, Roy M.; Stokes, Eric H.

1999-01-01

Theoretical models are proposed to describe the interaction of water with phenolic polymer. The theoretical models involve the study of the flow of a viscous fluid through a porous media and the thermodynamic theory of mixtures. From the theory, a set of mathematical relations are developed to simulate the effect of water on the thermostructural response of phenolic composites. The expressions are applied to simulate the measured effect of water in a series of experiments conducted on carbon phenolic composites.

Experimental feasibility of the airborne measurement of absolute oil fluorescence spectral conversion efficiency

NASA Technical Reports Server (NTRS)

Hoge, F. E.; Swift, R. N.

1983-01-01

Airborne lidar oil spill experiments carried out to determine the practicability of the AOFSCE (absolute oil fluorescence spectral conversion efficiency) computational model are described. The results reveal that the model is suitable over a considerable range of oil film thicknesses provided the fluorescence efficiency of the oil does not approach the minimum detection sensitivity limitations of the lidar system. Separate airborne lidar experiments to demonstrate measurement of the water column Raman conversion efficiency are also conducted to ascertain the ultimate feasibility of converting such relative oil fluorescence to absolute values. Whereas the AOFSCE model is seen as highly promising, further airborne water column Raman conversion efficiency experiments with improved temporal or depth-resolved waveform calibration and software deconvolution techniques are thought necessary for a final determination of suitability.

GPS Water Vapor Tomography: First results from the ESCOMPTE Field Experiment

NASA Astrophysics Data System (ADS)

Masson, F.; Champollion, C.; Bouin, M.-N.; Walpersdorf, A.; van Baelen, J.; Doerflinger, E.; Bock, O.

2003-04-01

We develop a tomographic software to model the spatial distribution of the tropospheric water vapor from GPS data. First we present simulations based on a real GPS station distribution and simple tropospheric models, which prove the potentiality of the method. Second we apply the software to the ESCOMPTE data. During the ESCOMPTE field experiment, a dense network of 17 dual frequency GPS receivers has been operated for two weeks within a 20 km x 20 km area around Marseille (Southern France). The network extends from the sea level to the top of the Etoile chain (~700 m high). The input data are the slant delay values obtained by combining the estimated zenith delay values with the horizontal gradients. The effect of the initial tropospheric water vapor model, the number and thickness of the layers of the model, the a priori model and data covariance and some other parameters will be discussed. Simultaneously water vapor radiometer, solar spectrometer, Raman lidar and radiosondes have been deployed to get a data set usable for comparison with the tomographic inversion results and validation of the method. Comparison with meteorological models (MesoNH - Meteo-France) will be shown.

Multiphase flow experiments, mathematical modeling and numerical simulation of the water - gas - solute movement

NASA Astrophysics Data System (ADS)

Li, Y.; Ma, X.; Su, N.

2013-12-01

The movement of water and solute into and through the vadose zone is, in essence, an issue of immiscible displacement in pore-space network of a soil. Therefore, multiphase flow and transport in porous media, referring to three medium: air, water, and the solute, pose one of the largest unresolved challenges for porous medium fluid seepage. However, this phenomenon has always been largely neglected. It is expected that a reliable analysis model of the multi-phase flow in soil can truly reflect the process of natural movement about the infiltration, which is impossible to be observed directly. In such cases, geophysical applications of the nuclear magnetic resonance (NMR) provides the opportunity to measure the water movements into soils directly over a large scale from tiny pore to regional scale, accordingly enable it available both on the laboratory and on the field. In addition, the NMR provides useful information about the pore space properties. In this study, we proposed both laboratory and field experiments to measure the multi-phase flow parameters, together with optimize the model in computer programming based on the fractional partial differential equations (fPDE). In addition, we establish, for the first time, an infiltration model including solute flowing with water, which has huge influence on agriculture and soil environment pollution. Afterwards, with data collected from experiments, we simulate the model and analyze the spatial variability of parameters. Simulations are also conducted according to the model to evaluate the effects of airflow on water infiltration and other effects such as solute and absorption. It has significant meaning to oxygen irrigation aiming to higher crop yield, and shed more light into the dam slope stability. In summary, our framework is a first-time model added in solute to have a mathematic analysis with the fPDE and more instructive to agriculture activities.

Cooler?

ERIC Educational Resources Information Center

Firth, Ian

1971-01-01

Presents experiments, models, and interpretations of reports that hot water begins to freeze faster than cooler water. Preliminary conclusions show that the surface area, side wall cooling, evaporation, and environment are the most important parameters. (DS)

Non-isothermal infiltration and tracer transport experiments on large soil columns

NASA Astrophysics Data System (ADS)

Sobotkova, Martina; Snehota, Michal; Cejkova, Eva; Tesar, Miroslav

2016-04-01

Isothermal and non-isothermal infiltration experiments were carried out in the laboratory on large undisturbed soil columns (19 cm in diameter, 25 cm high) taken at the experimental catchments Roklan (Sumava Mountains, Czech Republic) and Uhlirska (Jizera Mountains, Czech republic). The aim of the study was twofold. The first goal was to obtain water flow and heat transport data for indirect parameter estimation of thermal and hydraulic properties of soils from two sites by inverse modelling. The second aim was to investigate the extent of impact of the temperature on saturated hydraulic conductivity (Ksat) and dispersity of solute transport. The temperature of infiltrating water in isothermal experiment (20 °C) was equal to the initial temperature of the sample. For non-isothermal experiment water temperature was 5°C, while the initial temperature of the sample was 20°C as in previous case. The experiment was started by flooding the sample surface. Then water level was maintained at constant level throughout the infiltration run using the optical sensor and peristaltic pump. Concentration pulse of deuterium was applied at the top of the soil sample, during the steady state flow. Initial pressure head in the sample was close to field capacity. Two tensiometers and two temperature sensors were inserted in the soil sample in two depths (9 and 15 cm below the top of the sample). Two additional temperature sensors monitored the temperature entering and leaving the samples. Water drained freely through the perforated plate at the bottom of sample by gravity. Inflow and outflow water flux densities, water pressure heads and soil temperatures were monitored continuously during experiments. Effluent was sampled in regular time intervals and samples were analysed for deuterium concentrations by laser spectroscopy to develop breakthrough curves. The outcome of experiments are the series of measured water fluxes, pressure heads and temperatures ready for inverse modelling by dual permeability. The saturated hydraulic conductivity of soil columns was higher in the case of higher temperature of flowing water. The change was however not proportional to Ksat change induced by temperature change of viscosity only.

Irrigation water demand: A meta-analysis of price elasticities

NASA Astrophysics Data System (ADS)

Scheierling, Susanne M.; Loomis, John B.; Young, Robert A.

2006-01-01

Metaregression models are estimated to investigate sources of variation in empirical estimates of the price elasticity of irrigation water demand. Elasticity estimates are drawn from 24 studies reported in the United States since 1963, including mathematical programming, field experiments, and econometric studies. The mean price elasticity is 0.48. Long-run elasticities, those that are most useful for policy purposes, are likely larger than the mean estimate. Empirical results suggest that estimates may be more elastic if they are derived from mathematical programming or econometric studies and calculated at a higher irrigation water price. Less elastic estimates are found to be derived from models based on field experiments and in the presence of high-valued crops.

Global Energy and Water Cycle Experiment (GEWEX) and the Continental-scale International Project (GCIP)

NASA Technical Reports Server (NTRS)

Vane, Deborah

1993-01-01

A discussion of the objectives of the Global Energy and Water Cycle Experiment (GEWEX) and the Continental-scale International Project (GCIP) is presented in vugraph form. The objectives of GEWEX are as follows: determine the hydrological cycle by global measurements; model the global hydrological cycle; improve observations and data assimilation; and predict response to environmental change. The objectives of GCIP are as follows: determine the time/space variability of the hydrological cycle over a continental-scale region; develop macro-scale hydrologic models that are coupled to atmospheric models; develop information retrieval schemes; and support regional climate change impact assessment.

Atmospheric CO2 concentration impacts on maize yield performance under dry conditions: do crop model simulate it right ?

NASA Astrophysics Data System (ADS)

Durand, Jean-Louis; Delusca, Kénel; Boote, Ken; Lizaso, Jon; Manderscheid, Remy; Jochaim Weigel, Hans; Ruane, Alex C.; Rosenzweig, Cynthia; Jones, Jim; Ahuja, Laj; Anapalli, Saseendran; Basso, Bruno; Baron, Christian; Bertuzzi, Patrick; Biernath, Christian; Deryng, Delphine; Ewert, Frank; Gaiser, Thomas; Gayler, Sebastian; Heinlein, Florian; Kersebaum, Kurt Christian; Kim, Soo-Hyung; Müller, Christoph; Nendel, Claas; Olioso, Albert; Priesack, Eckhart; Ramirez-Villegas, Julian; Ripoche, Dominique; Rötter, Reimund; Seidel, Sabine; Srivastava, Amit; Tao, Fulu; Timlin, Dennis; Twine, Tracy; Wang, Enli; Webber, Heidi; Zhao, Shigan

2017-04-01

In most regions of the world, maize yields are at risk of be reduced due to rising temperatures and reduced water availability. Rising temperature tends to reduce the length of the growth cycle and the amount of intercepted solar energy. Water deficits reduce the leaf area expansion, photosynthesis and sometimes, with an even more pronounced impact, severely reduce the efficiency of kernel set. In maize, the major consequence of atmospheric CO2 concentration ([CO2]) is the stomatal closure-induced reduction of leaf transpiration rate, which tends to mitigate those negative impacts. Indeed FACE studies report significant positive responses to CO2 of maize yields (and other C4 crops) under dry conditions only. Given the projections by climatologists (typically doubling of [CO2] by the end of this century) projected impacts must take that climate variable into account. However, several studies show a large incertitude in estimating the impact of increasing [CO2] on maize remains using the main crop models. The aim of this work was to compare the simulations of different models using input data from a FACE experiment conducted in Braunschweig during 2 years under limiting and non-limiting water conditions. Twenty modelling groups using different maize models were given the same instructions and input data. Following calibration of cultivar parameters under non-limiting water conditions and under ambient [CO2] treatments of both years, simulations were undertaken for the other treatments: High [ CO2 ] (550 ppm) 2007 and 2008 in both irrigation regimes, and DRY AMBIENT 2007 and 2008. Only under severe water deficits did models simulate an increase in yield for CO2 enrichment, which was associated with higher harvest index and, for those models which simulated it, higher grain number. However, the CO2 enhancement under water deficit simulated by the 20 models was 20 % at most and 10 % on average only, i.e. twice less than observed in that experiment. As in the experiment, the simulated impact of [CO2 ] on water use was negligible, with a general displacement of the water deficit toward later phases of the crop along with longer green leaf area duration at reduced transpiration rate. In general models which used explicit response functions of stomatal conductance to [CO2] performed significantly better than those which did not. Our results highlight the need for model improvement with respect to simulating transpirational water use and its impact on water status during the kernel-set phase. We shall discuss the various ways of simulating the response of stomatal conductance to [CO2] and the response of kernel set to water deficits.

Dynamic compression of water to 700 GPa: single- and double shock experiments on Sandia's Z machine, first principles simulations, and structure of water planets

NASA Astrophysics Data System (ADS)

Mattsson, Thomas R.

2011-11-01

Significant progress has over the last few years been made in high energy density physics (HEDP) by executing high-precision multi-Mbar experiments and performing first-principles simulations for elements ranging from carbon [1] to xenon [2]. The properties of water under HEDP conditions are of particular importance in planetary science due to the existence of ice-giants like Neptune and Uranus. Modeling the two planets, as well as water-rich exoplanets, requires knowing the equation of state (EOS), the pressure as a function of density and temperature, of water with high accuracy. Although extensive density functional theory (DFT) simulations have been performed for water under planetary conditions [3] experimental validation has been lacking. Accessing thermodynamic states along planetary isentropes in dynamic compression experiments is challenging because the principal Hugoniot follows a significantly different path in the phase diagram. In this talk, we present experimental data for dynamic compression of water up to 700 GPa, including in a regime of the phase-diagram intersected by the Neptune isentrope and water-rich models for the exoplanet GJ436b. The data was obtained on the Z-accelerator at Sandia National Laboratories by performing magnetically accelerated flyer plate impact experiments measuring both the shock and re-shock in the sample. The high accuracy makes it possible for the data to be used for detailed model validation: the results validate first principles based thermodynamics as a reliable foundation for planetary modeling and confirm the fine effect of including nuclear quantum effects on the shock pressure. Sandia National Laboratories is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract No. DE-AC04-94AL85000. [4pt] [1] M.D. Knudson, D.H. Dolan, and M.P. Desjarlais, SCIENCE 322, 1822 (2008).[0pt] [2] S. Root, et al., Phys. Rev. Lett. 105, 085501 (2010).[0pt] [3] M. French, et al., Phys. Rev. B 79, 054107 (2009).

How accurately do maize crop models simulate the interactions of atmospheric CO2 concentration levels with limited water supply on water use and yield?

USDA-ARS?s Scientific Manuscript database

This study assesses the ability of 21 crop models to capture the impact of elevated CO2 concentration ([CO218 ]) on maize yield and water use as measured in a 2-year Free Air Carbon dioxide Enrichment experiment conducted at the Thünen Institute in Braunschweig, Germany (Manderscheid et al. 2014). D...

Evaluating the Impact of Global Warming on Water Balance of Maize by High-precision Controlled Experiment and MLCan model

NASA Astrophysics Data System (ADS)

Ma, Y.; Song, X.; Kumar, P.; Wu, Y.; Woo, D.; Le, P. V.; Ma, C.

2016-12-01

Increased temperature affects the agricultural hydrologic cycle not only by changing precipitation levels, evapotranspiration and the magnitude and timing of run-off, but also by impacting water flows and soil water dynamics. Accurate prediction of hydrologic change under global warming requires high-precision experiment and mathematical model to determine water interaction between interfaces in the soil-plant-atmosphere continuum. In this study, the weighting lysimeter and chamber were coupled to monitor water balance component dynamics of maize under controlled ambient temperature and elevated temperature of 2°C conditions. A mechanistic multilayer canopy-soil-root system model (MLCan) was used to predict hydrologic fluxes variation under different elevated temperature scenarios after calibration with experimental results. The results showed that maize growth period reduced 8 days under increased temperature of 2°C. The mean daily evapotranspiration, soil water storage change, and drainage was 2.66 mm, -2.75 mm, and 0.22 mm under controlled temperature condition, respectively. When temperature was elevated by 2°C, the average daily ET for maize significantly increased about 6.7% (p<0.05). However, there were non-significant impacts of increased temperature on the daily soil water storage change and drainage (p>0.05). Quantification of changes in water balance components induced by temperature increase for maize is critical for optimizing irrigation water management practices and improving water use efficiency.

Hysteresis of Soil Point Water Retention Functions Determined by Neutron Radiography

NASA Astrophysics Data System (ADS)

Perfect, E.; Kang, M.; Bilheux, H.; Willis, K. J.; Horita, J.; Warren, J.; Cheng, C.

2010-12-01

Soil point water retention functions are needed for modeling flow and transport in partially-saturated porous media. Such functions are usually determined by inverse modeling of average water retention data measured experimentally on columns of finite length. However, the resulting functions are subject to the appropriateness of the chosen model, as well as the initial and boundary condition assumptions employed. Soil point water retention functions are rarely measured directly and when they are the focus is invariably on the main drying branch. Previous direct measurement methods include time domain reflectometry and gamma beam attenuation. Here we report direct measurements of the main wetting and drying branches of the point water retention function using neutron radiography. The measurements were performed on a coarse sand (Flint #13) packed into 2.6 cm diameter x 4 cm long aluminum cylinders at the NIST BT-2 (50 μm resolution) and ORNL-HFIR CG1D (70 μm resolution) imaging beamlines. The sand columns were saturated with water and then drained and rewetted under quasi-equilibrium conditions using a hanging water column setup. 2048 x 2048 pixel images of the transmitted flux of neutrons through the column were acquired at each imposed suction (~10-15 suction values per experiment). Volumetric water contents were calculated on a pixel by pixel basis using Beer-Lambert’s law in conjunction with beam hardening and geometric corrections. The pixel rows were averaged and combined with information on the known distribution of suctions within the column to give 2048 point drying and wetting functions for each experiment. The point functions exhibited pronounced hysteresis and varied with column height, possibly due to differences in porosity caused by the packing procedure employed. Predicted point functions, extracted from the hanging water column volumetric data using the TrueCell inverse modeling procedure, showed very good agreement with the range of point functions measured within the column using neutron radiography. Extension of these experiments to 3-dimensions using neutron tomography is planned.

Visual analysis of immiscible displacement processes in porous media under ultrasound effect

NASA Astrophysics Data System (ADS)

Naderi, Khosrow; Babadagli, Tayfun

2011-05-01

The effect of sonic waves, in particular, ultrasonic radiation, on immiscible displacement in porous media and enhanced oil recovery has been of interest for more than five decades. Attempts were made to investigate the effect through core scale experimental or theoretical models. Visual experiments are useful to scrutinize the reason for improved oil recovery under acoustic waves of different frequency but are not abundant in literature. In this paper, we report observations and analyses as to the effects of ultrasonic energy on immiscible displacement and interaction of the fluid matrix visually in porous media through two-dimensional (2D) sand pack experiments. 2D glass bead models with different wettabilities were saturated with different viscosity oils and water was injected into the models. The experiments were conducted with and without ultrasound. Dynamic water injection experiments were preferred as they had both viscous and capillary forces in effect. The displacement patterns were evaluated both in terms of their shape, size, and the interface characteristics quantitatively and qualitatively to account for the effects of ultrasonic waves on the displacement and the reason for increased oil production under this type of sonic wave. More compact clusters were observed when ultrasonic energy was present in water-wet systems. In the oil-wet cases, more oil was produced after breakthrough when ultrasound was applied and no compact clusters were formed in contrast to the water-wet cases.

­­Drought, water conservation, and water demand rebound in California

NASA Astrophysics Data System (ADS)

Gonzales, P.; Ajami, N.

2017-12-01

There is growing recognition that dynamic community values, preferences, and water use behaviors are important drivers of water demand in addition to external factors such as temperature and precipitation. Water demand drivers have been extensively studied, yet they have traditionally been applied to models that assume static conditions and usually do not account for potential societal changes in response to increased scarcity awareness. For example, following a period of sustained low demand such as during a drought, communities often increase water use during a hydrologically wet period, a phenomenon known as "rebounding" water use. Yet previous experiences show the extent of this rebound is not a straightforward function of policy and efficiency improvements, but may also reflect short-term or long-lasting change in community behavior, which are not easily captured by models that assume stationarity. In this study we explore cycles of decreased water demand during drought and subsequent water use rebound observed in California in recent decades. We have developed a novel dynamic system model for water demand in three diverse but interconnected service areas in the San Francisco Bay Area, exposing local trends of changing water use behaviors and long-term impacts on water demand since 1980 to the present. In this model, we apply the concept of social memory, defined as a community's inherited knowledge about hazardous events or degraded environmental conditions from past experiences. While this concept has been applied to further conceptual understanding of socio-hydrologic systems in response to hydrological extremes, to the best of our knowledge this the first study to incorporate social memory to model the water demand rebound phenomenon and to use such a model in the examination of changing dynamics validated by historical data. In addition, we take a closer look at water demand during the recent historic drought in California from 2012-16, and relate our long-term insights to recent events and statewide trends. This comparative modeling exercise shows that increased public awareness during droughts can be related to systematic changes in the way diverse communities respond to near- and long-term conservation incentives.

Acceleration induced water removal from ear canals.

NASA Astrophysics Data System (ADS)

Kang, Hosung; Averett, Katelee; Jung, Sunghwan

2017-11-01

Children and adults commonly experience having water trapped in the ear canals after swimming. To remove the water, individuals will shake their head sideways. Since a child's ear canal has a smaller diameter, it requires more acceleration of the head to remove the trapped water. In this study, we theoretically and experimentally investigated the acceleration required to break the surface meniscus of the water in artificial ear canals and hydrophobic-coated glass tubes. In experiments, ear canal models were 3D-printed from a CT-scanned human head. Also, glass tubes were coated with silane to match the hydrophobicity in ear canals. Then, using a linear stage, we measured the acceleration values required to forcefully eject the water from the artificial ear canals and glass tubes. A theoretical model was developed to predict the critical acceleration at a given tube diameter and water volume by using a modified Rayleigh-Taylor instability. Furthermore, this research can shed light on the potential of long-term brain injury and damage by shaking the head to push the water out of the ear canal. This research was supported by National Science Foundation Grant CBET-1604424.

Effects of Salt Accumulation in Soil by Evaporation on Unsaturated Soil Hydraulic Properties

NASA Astrophysics Data System (ADS)

Liu, Y.; Liu, Q.

2017-12-01

Soil salinization is one type of soil degradation caused by saline groundwater evaporation. Salt accumulation in the soil will change the pore structure of soil, which should change the unsaturated soil hydraulic properties including the soil water characteristic curve (SWCC). To investigate the effect of salt accumulation on the SWCC and find the best suitable SWCC model to characterize the relationship of soil moisture and soil matrix potential, we have conducted laboratory SWCC experiments with the soil columns saturated by NaCl solution with different concentration (deionized water, 3 g/L, 15 g/L, 50 g/L, 100 g/L and 200 g/L). As the concentration of initial solution increases, the matrix potential corresponding to the same moisture increases. As the water was evaporated, the salt would precipitate in soil continuously, which would decrease the porosity of soils and increase the negative pressure of soils. With higher initial concentration, the more salt accumulation caused the more residual water content in the soils. For van Genuchten-Mualem model, the residual water contents θr were 0.0159, 0.0181, 0.0182, 0.0328, 0.0312, 0.0723, 0.0864 in the columns initially saturated by deionized water, 3 g/L, 15 g/L, 50 g/L, 100 g/L and 200 g/L, respectively. The van Genuchten-Mualem model, Fredlund-Xing model, Gardern model, Mckee-Bumb model and Brooks-Corey model were fitted by MATLAB with the experiments data, and the fitted coefficients were compared. The Fredlund-Xing model has the best fitting coefficients and the calculated value was consistent with the observed data.

Quantum chemistry in arbitrary dielectric environments: Theory and implementation of nonequilibrium Poisson boundary conditions and application to compute vertical ionization energies at the air/water interface

NASA Astrophysics Data System (ADS)

Coons, Marc P.; Herbert, John M.

2018-06-01

Widely used continuum solvation models for electronic structure calculations, including popular polarizable continuum models (PCMs), usually assume that the continuum environment is isotropic and characterized by a scalar dielectric constant, ɛ. This assumption is invalid at a liquid/vapor interface or any other anisotropic solvation environment. To address such scenarios, we introduce a more general formalism based on solution of Poisson's equation for a spatially varying dielectric function, ɛ(r). Inspired by nonequilibrium versions of PCMs, we develop a similar formalism within the context of Poisson's equation that includes the out-of-equilibrium dielectric response that accompanies a sudden change in the electron density of the solute, such as that which occurs in a vertical ionization process. A multigrid solver for Poisson's equation is developed to accommodate the large spatial grids necessary to discretize the three-dimensional electron density. We apply this methodology to compute vertical ionization energies (VIEs) of various solutes at the air/water interface and compare them to VIEs computed in bulk water, finding only very small differences between the two environments. VIEs computed using approximately two solvation shells of explicit water molecules are in excellent agreement with experiment for F-(aq), Cl-(aq), neat liquid water, and the hydrated electron, although errors for Li+(aq) and Na+(aq) are somewhat larger. Nonequilibrium corrections modify VIEs by up to 1.2 eV, relative to models based only on the static dielectric constant, and are therefore essential to obtain agreement with experiment. Given that the experiments (liquid microjet photoelectron spectroscopy) may be more sensitive to solutes situated at the air/water interface as compared to those in bulk water, our calculations provide some confidence that these experiments can indeed be interpreted as measurements of VIEs in bulk water.

Quantum chemistry in arbitrary dielectric environments: Theory and implementation of nonequilibrium Poisson boundary conditions and application to compute vertical ionization energies at the air/water interface.

PubMed

Coons, Marc P; Herbert, John M

2018-06-14

Widely used continuum solvation models for electronic structure calculations, including popular polarizable continuum models (PCMs), usually assume that the continuum environment is isotropic and characterized by a scalar dielectric constant, ε. This assumption is invalid at a liquid/vapor interface or any other anisotropic solvation environment. To address such scenarios, we introduce a more general formalism based on solution of Poisson's equation for a spatially varying dielectric function, ε(r). Inspired by nonequilibrium versions of PCMs, we develop a similar formalism within the context of Poisson's equation that includes the out-of-equilibrium dielectric response that accompanies a sudden change in the electron density of the solute, such as that which occurs in a vertical ionization process. A multigrid solver for Poisson's equation is developed to accommodate the large spatial grids necessary to discretize the three-dimensional electron density. We apply this methodology to compute vertical ionization energies (VIEs) of various solutes at the air/water interface and compare them to VIEs computed in bulk water, finding only very small differences between the two environments. VIEs computed using approximately two solvation shells of explicit water molecules are in excellent agreement with experiment for F - (aq), Cl - (aq), neat liquid water, and the hydrated electron, although errors for Li + (aq) and Na + (aq) are somewhat larger. Nonequilibrium corrections modify VIEs by up to 1.2 eV, relative to models based only on the static dielectric constant, and are therefore essential to obtain agreement with experiment. Given that the experiments (liquid microjet photoelectron spectroscopy) may be more sensitive to solutes situated at the air/water interface as compared to those in bulk water, our calculations provide some confidence that these experiments can indeed be interpreted as measurements of VIEs in bulk water.

Experimental vs. modeled water use in mature Norway spruce (Picea abies) exposed to elevated CO(2).

PubMed

Leuzinger, Sebastian; Bader, Martin K-F

2012-01-01

Rising levels of atmospheric CO(2) have often been reported to reduce plant water use. Such behavior is also predicted by standard equations relating photosynthesis, stomatal conductance, and atmospheric CO(2) concentration, which form the core of dynamic global vegetation models (DGVMs). Here, we provide first results from a free air CO(2) enrichment (FACE) experiment with naturally growing, mature (35 m) Picea abies (L.) (Norway spruce) and compare them to simulations by the DGVM LPJ-GUESS. We monitored sap flow, stem water deficit, stomatal conductance, leaf water potential, and soil moisture in five 35-40 m tall CO(2)-treated (550 ppm) trees over two seasons. Using LPJ-GUESS, we simulated this experiment using climate data from a nearby weather station. While the model predicted a stable reduction of transpiration of between 9% and 18% (at concentrations of 550-700 ppm atmospheric CO(2)), the combined evidence from various methods characterizing water use in our experimental trees suggest no changes in response to future CO(2) concentrations. The discrepancy between the modeled and the experimental results may be a scaling issue: while dynamic vegetation models correctly predict leaf-level responses, they may not sufficiently account for the processes involved at the canopy and ecosystem scale, which could offset the first-order stomatal response.

Numerical modeling of NI-monitored 3D infiltration experiment

NASA Astrophysics Data System (ADS)

Dohnal, Michal; Dusek, Jaromir; Snehota, Michal; Sacha, Jan; Vogel, Tomas; Votrubova, Jana

2014-05-01

It is well known that the temporal changes of saturated hydraulic conductivity caused by the occurrence of air phase discontinuities often play an important role in water flow and solute transport experiments. In the present study, a series of infiltration-outflow experiments was conducted to test several working hypotheses about the mechanism of air phase trapping. The experiments were performed on a porous sample with artificial internal structure, using three sandy materials with contrasting hydraulic properties. The sample was axially symmetric with continuous preferential pathways and separate porous matrix blocks (the sample was 3.4 cm in diameter and 8.8 cm high). The infiltration experiments were monitored by neutron imaging (NI). The NI data were then used to quantify the water content of the selected sample regions. The flow regime in the sample was studied using a three-dimensional model based on Richards' equation. The equation was solved by the finite element method. The results of the numerical simulations of the infiltration experiments were compared with the measured outflow rates and with the spatial distribution of water content determined by NI. The research was supported by the Czech Science Foundation Project No. 14-03691S.

Ultrafast pump-probe and 2DIR anisotropy and temperature-dependent dynamics of liquid water within the E3B model.

PubMed

Ni, Yicun; Skinner, J L

2014-07-14

Recently, Tainter et al. [J. Chem. Phys. 134, 184501 (2011)] reparameterized a new rigid water model (E3B) that explicitly includes three-body interactions in its Hamiltonian. Compared to commonly used water models such as SPC/E and TIP4P, the new model shows better agreement with experiment for many physical properties including liquid density, melting temperature, virial coefficients, etc. However, the dynamics of the E3B model, especially as a function of temperature, has not been systematically evaluated. Experimental nonlinear vibrational spectroscopy is an ideal tool to study the dynamics of matter in condensed phases. In the present study, we calculate linear and nonlinear vibrational spectroscopy observables for liquid water using the E3B model at five temperatures: 10, 30, 50, 70 and 90 °C. Specifically, we calculate absorption and Raman spectra and pump-probe anisotropy for HOD in H2O at all temperatures, frequency-resolved pump-probe anisotropy for HOD in both H2O and D2O at 30 °C, and 2DIR anisotropy for HOD in D2O at 30 °C. In all cases, we find reasonable agreement with experiment, and for the ultrafast spectroscopy our results are a significant improvement over those of the SPC/E model. A likely reason for this improvement is that the three-body interaction terms in the E3B model are able to model cooperative hydrogen bonding. We also calculate rotational and frequency relaxation times at all temperatures, and fit the results to the Arrhenius equation. We find that the activation energy for hydrogen-bond switching in liquid water is 3.8 kcal/mol, which agrees well with the experimental value of 3.7 kcal/mol obtained from anisotropy decay experiments.

Models for predicting disinfection byproduct (DBP) formation in drinking waters: a chronological review.

PubMed

Chowdhury, Shakhawat; Champagne, Pascale; McLellan, P James

2009-07-01

Disinfection for the supply of safe drinking water forms a variety of known and unknown byproducts through reactions between the disinfectants and natural organic matter. Chronic exposure to disinfection byproducts through the ingestion of drinking water, inhalation and dermal contact during regular indoor activities (e.g., showering, bathing, cooking) may pose cancer and non-cancer risks to human health. Since their discovery in drinking water in 1974, numerous studies have presented models to predict DBP formation in drinking water. To date, more than 48 scientific publications have reported 118 models to predict DBP formation in drinking waters. These models were developed through laboratory and field-scale experiments using raw, pretreated and synthetic waters. This paper aims to review DBP predictive models, analyze the model variables, assess the model advantages and limitations, and to determine their applicability to different water supply systems. The paper identifies the current challenges and future research needs to better control DBP formation. Finally, important directions for future research are recommended to protect human health and to follow the best management practices.

Solvent fluctuations and nuclear quantum effects modulate the molecular hyperpolarizability of water

NASA Astrophysics Data System (ADS)

Liang, Chungwen; Tocci, Gabriele; Wilkins, David M.; Grisafi, Andrea; Roke, Sylvie; Ceriotti, Michele

2017-07-01

Second-harmonic scattering (SHS) experiments provide a unique approach to probe noncentrosymmetric environments in aqueous media, from bulk solutions to interfaces, living cells, and tissue. A central assumption made in analyzing SHS experiments is that each molecule scatters light according to a constant molecular hyperpolarizability tensor β(2 ). Here, we investigate the dependence of the molecular hyperpolarizability of water on its environment and internal geometric distortions, in order to test the hypothesis of constant β(2 ). We use quantum chemistry calculations of the hyperpolarizability of a molecule embedded in point-charge environments obtained from simulations of bulk water. We demonstrate that both the heterogeneity of the solvent configurations and the quantum mechanical fluctuations of the molecular geometry introduce large variations in the nonlinear optical response of water. This finding has the potential to change the way SHS experiments are interpreted: In particular, isotopic differences between H2O and D2O could explain recent SHS observations. Finally, we show that a machine-learning framework can predict accurately the fluctuations of the molecular hyperpolarizability. This model accounts for the microscopic inhomogeneity of the solvent and represents a step towards quantitative modeling of SHS experiments.

Offset-Free Model Predictive Control of Open Water Channel Based on Moving Horizon Estimation

NASA Astrophysics Data System (ADS)

Ekin Aydin, Boran; Rutten, Martine

2016-04-01

Model predictive control (MPC) is a powerful control option which is increasingly used by operational water managers for managing water systems. The explicit consideration of constraints and multi-objective management are important features of MPC. However, due to the water loss in open water systems by seepage, leakage and evaporation a mismatch between the model and the real system will be created. These mismatch affects the performance of MPC and creates an offset from the reference set point of the water level. We present model predictive control based on moving horizon estimation (MHE-MPC) to achieve offset free control of water level for open water canals. MHE-MPC uses the past predictions of the model and the past measurements of the system to estimate unknown disturbances and the offset in the controlled water level is systematically removed. We numerically tested MHE-MPC on an accurate hydro-dynamic model of the laboratory canal UPC-PAC located in Barcelona. In addition, we also used well known disturbance modeling offset free control scheme for the same test case. Simulation experiments on a single canal reach show that MHE-MPC outperforms disturbance modeling offset free control scheme.

MODELING HEXAVALENT CHROMIUM REDUCTION IN GROUND- WATER IN FIELD-SCALE TRANSPORT AND LABORATORY BATCH EXPERIMENTS

EPA Science Inventory

A plausible and consistent model is developed to obtain a quantitative description of the gradual disappearance of hexavalent chromium (Cr(VI)) from groundwater in a small-scale field tracer test and in batch kinetic experiments using aquifer sediments under similar chemical cond...

The Acoustic Model Evaluation Committee (AMEC) Reports. Volume 1A. Summary of Range Independent Environment Acoustic Propagation Data Sets

DTIC Science & Technology

1982-09-01

experiment were: isothermal layer depth 36 ft depressed channel axis 66 ft surface water temperature 59.4 F sea state 2 Discussion The propagation loss...experiments were: isothermal layer depths 56 ft surface water temperature 59.7 0F - sea state 1 Discussion The propagation loss measurements are summarized...number of observations 1854 isothermal layer depth 33 ft surface water temperature 59.9°F sea state 2 Discussion The propagation loss measurements

Determination of Transport Parameters in Unsaturated Zone by Tracer Experiment in the Porous Aquifer located at Ljubljana, Slovenia

NASA Astrophysics Data System (ADS)

Vidmar, S.; Cencur Curk, B.

2009-04-01

The gravel sandy aquifer of Ljubljansko polje is the source of drinking water for nearly 300.000 inhabitants of the Ljubljana city and vicinity. There are two main waterworks: Kleče and Hrastje. The plain area of Ljubljansko polje is a tectonic sink and consists of river sediments that can reach in thickness more than 100 m in the deepest part. The bedrock is the impermeable permocarbonic clayey shale, mudstones and sandstones. The hydraulic conductivity of Ljubljansko polje sediments is very good, from 10-2 m/s in the central part to 3.7•10-3 m/s on the borders of the plain. The average groundwater level is 20 m below surface. A numerical groundwater flow model was established for the wider area of the Ljubljansko polje aquifer. The fore mentioned model was not calibrated on solute transport parameters but only on water levels and this lead to unreliability in the transport model and its predictions of pollution scenarios. The transport model needs to calculate reliable scenarios of pollution dispersion, which can only be achieved with the application of real transport parameters. Human activities in the area of the Hrastje waterworks of Ljubljana threaten to degrade groundwater quality. For this reason several tracer experiments were carried out in the past. Despite a great risk, the experiments were performed on the catchment area of the Hrastje waterworks, inside the second water protection zone. During the experiments the water from Hrastje waterworks was still in use for drinking water supply. The tracer experiments were carried out in order to determine the solute transport parameters such as advection, dispersion and sorption. The research proved that the tracers could be used safely on sensitive area and that the researchers are capable and qualified to carry it out with a highest level of security. Since none of the past tracer experiments, carried out in the same area, gave us any detailed information on pollutant spreading in unsaturated zone a new tracer experiment was performed. Uranine was used as a tracer with a single time injection (1 kg) directly into the unsaturated zone. To achieve no sorption on organic particles the top layer of the ground (approx. 1m) was removed. The concentrations of the tracer spreading were observed in the well which is down gradient (approx. 22m) from the injection point. The tracer experiment was monitored for 305 days with records recorded every 4 minutes. All major events observed from the breakthrough curve, corresponded to rain events with a different delay depending on the water content in the unsaturated zone. When the unsaturated zone contains water the response in the observation well was faster than when the unsaturated zone was dry. The obtained data have been used in an analytical method (Multi-Dispersion-Model (MDM)). This solution provided the following transport parameters: mean transit time, mean velocity, longitudinal dispersion and dispersivity. The obtained parameters from the analytical solution will also be verified in the numerical model. The final results should enable better knowledge of the solute transport parameters and thus a better understanding of pollution dispersion as a help for water supply management system including measures for pollution prevention and as an actions/measure scenario in case of pollution.

Implications of Modeling Uncertainty for Water Quality Decision Making

NASA Astrophysics Data System (ADS)

Shabman, L.

2002-05-01

The report, National Academy of Sciences report, "Assessing the TMDL Approach to Water Quality Management" endorsed the "watershed" and "ambient water quality focused" approach" to water quality management called for in the TMDL program. The committee felt that available data and models were adequate to move such a program forward, if the EPA and all stakeholders better understood the nature of the scientific enterprise and its application to the TMDL program. Specifically, the report called for a greater acknowledgement of model prediction uncertinaity in making and implementing TMDL plans. To assure that such uncertinaity was addressed in water quality decision making the committee called for a commitment to "adaptive implementation" of water quality management plans. The committee found that the number and complexity of the interactions of multiple stressors, combined with model prediction uncertinaity means that we need to avoid the temptation to make assurances that specific actions will result in attainment of particular water quality standards. Until the work on solving a water quality problem begins, analysts and decision makers cannot be sure what the correct solutions are, or even what water quality goals a community should be seeking. In complex systems we need to act in order to learn; adaptive implementation is a concurrent process of action and learning. Learning requires (1) continued monitoring of the waterbody to determine how it responds to the actions taken and (2) carefully designed experiments in the watershed. If we do not design learning into what we attempt we are not doing adaptive implementation. Therefore, there needs to be an increased commitment to monitoring and experiments in watersheds that will lead to learning. This presentation will 1) explain the logic for adaptive implementation; 2) discuss the ways that water quality modelers could characterize and explain model uncertinaity to decision makers; 3) speculate on the implications of the adaptive implementation for setting of water quality standards, for design of watershed monitoring programs and for the regulatory rules governing the TMDL program implementation.

Automated optimization of water-water interaction parameters for a coarse-grained model.

PubMed

Fogarty, Joseph C; Chiu, See-Wing; Kirby, Peter; Jakobsson, Eric; Pandit, Sagar A

2014-02-13

We have developed an automated parameter optimization software framework (ParOpt) that implements the Nelder-Mead simplex algorithm and applied it to a coarse-grained polarizable water model. The model employs a tabulated, modified Morse potential with decoupled short- and long-range interactions incorporating four water molecules per interaction site. Polarizability is introduced by the addition of a harmonic angle term defined among three charged points within each bead. The target function for parameter optimization was based on the experimental density, surface tension, electric field permittivity, and diffusion coefficient. The model was validated by comparison of statistical quantities with experimental observation. We found very good performance of the optimization procedure and good agreement of the model with experiment.

Development of an on-line aqueous particle sensor to study the performance of inclusions in a 12 tonne, delta shaped full scale water model tundish

NASA Astrophysics Data System (ADS)

Chakraborty, Abhishek

Detection of particulate matter thinly dispersed in a fluid medium with the aid of the difference in electrical conductivity between the pure fluid and the particles has been practiced at least since the last 50 to 60 years. The first such instruments were employed to measure cell counts in samples of biological fluid. Following a detailed study of the physics and principles operating within the device, called the Electric Sensing Zone (ESZ) principle, a new device called the Liquid Metal Cleanliness Analyzer (LiMCA) was invented which could measure and count particles of inclusions in molten metal. It provided a fast and fairly accurate tool to make online measurement of the quality of steel during refining and casting operations. On similar lines of development as the LiMCA, a water analogue of the device called, the Aqueous Particle Sensor (APS) was developed for physical modeling experiments of metal refining operations involving water models. The APS can detect and measure simulated particles of inclusions added to the working fluid (water). The present study involves the designing, building and final application of a new and improved APS in water modeling experiments to study inclusion behavior in a tundish operation. The custom built instrument shows superior performance and applicability in experiments involving physical modeling of metal refining operations, compared to its commercial counterparts. In addition to higher accuracy and range of operating parameters, its capability to take real-time experimental data for extended periods of time helps to reduce the total number of experiments required to reach a result, and makes it suitable for analyzing temporal changes occurring in unsteady systems. With the modern impetus on the quality of the final product of metallurgical operations, the new APS can prove to be an indispensable research tool to study and put forward innovative design and parametric changes in industrially practised metallurgical operations.

Microstructure and hydrogen bonding in water-acetonitrile mixtures.

PubMed

Mountain, Raymond D

2010-12-16

The connection of hydrogen bonding between water and acetonitrile in determining the microheterogeneity of the liquid mixture is examined using NPT molecular dynamics simulations. Mixtures for six, rigid, three-site models for acetonitrile and one water model (SPC/E) were simulated to determine the amount of water-acetonitrile hydrogen bonding. Only one of the six acetonitrile models (TraPPE-UA) was able to reproduce both the liquid density and the experimental estimates of hydrogen bonding derived from Raman scattering of the CN stretch band or from NMR quadrupole relaxation measurements. A simple modification of the acetonitrile model parameters for the models that provided poor estimates produced hydrogen-bonding results consistent with experiments for two of the models. Of these, only one of the modified models also accurately determined the density of the mixtures. The self-diffusion coefficient of liquid acetonitrile provided a final winnowing of the modified model and the successful, unmodified model. The unmodified model is provisionally recommended for simulations of water-acetonitrile mixtures.

Model Design for Water Wheel Control System of Heumgyeonggaknu

NASA Astrophysics Data System (ADS)

Kim, Sang Hyuk; Ham, Seon Young; Lee, Yong Sam

2016-03-01

Heumgyeonggaknu (????) is powered by a water-hammering-type water wheel. The technique that maintains the constant speed of the water wheel is assumed to be the one used in the Cheonhyeong (???) apparatus in Shui Yun Yi Xiang Tai (???) made by the Northern Song (??) dynasty in the 11th century. We investigated the history of the development and characteristics of the Cheonhyeong apparatus, and we analyzed ways to transmit the power of Heumgyeonggaknu. In addition, we carried out a conceptual design to systematically examine the power control system. Based on the conceptual design, we built a model for a water wheel control system that could be used in experiments by drawing a 3D model and a basic design.

Evaluation of an Infiltration Model with Microchannels

NASA Astrophysics Data System (ADS)

Garcia-Serrana, M.; Gulliver, J. S.; Nieber, J. L.

2015-12-01

This research goal is to develop and demonstrate the means by which roadside drainage ditches and filter strips can be assigned the appropriate volume reduction credits by infiltration. These vegetated surfaces convey stormwater, infiltrate runoff, and filter and/or settle solids, and are often placed along roads and other impermeable surfaces. Infiltration rates are typically calculated by assuming that water flows as sheet flow over the slope. However, for most intensities water flow occurs in narrow and shallow micro-channels and concentrates in depressions. This channelization reduces the fraction of the soil surface covered with the water coming from the road. The non-uniform distribution of water along a hillslope directly affects infiltration. First, laboratory and field experiments have been conducted to characterize the spatial pattern of flow for stormwater runoff entering onto the surface of a sloped surface in a drainage ditch. In the laboratory experiments different micro-topographies were tested over bare sandy loam soil: a smooth surface, and three and five parallel rills. All the surfaces experienced erosion; the initially smooth surface developed a system of channels over time that increased runoff generation. On average, the initially smooth surfaces infiltrated 10% more volume than the initially rilled surfaces. The field experiments were performed in the side slope of established roadside drainage ditches. Three rates of runoff from a road surface into the swale slope were tested, representing runoff from 1, 2, and 10-year storm events. The average percentage of input runoff water infiltrated in the 32 experiments was 67%, with a 21% standard deviation. Multiple measurements of saturated hydraulic conductivity were conducted to account for its spatial variability. Second, a rate-based coupled infiltration and overland model has been designed that calculates stormwater infiltration efficiency of swales. The Green-Ampt-Mein-Larson assumptions were implemented to calculate infiltration along with a kinematic wave model for overland flow that accounts for short-circuiting of flow. Additionally, a sensitivity analysis on the parameters implemented in the model has been performed. Finally, the field experiments results have been used to quantify the validity of the coupled model.

Improving Groundwater Data Interoperability: Results of the Second OGC Groundwater Interoperability Experiment

NASA Astrophysics Data System (ADS)

Lucido, J. M.; Booth, N.

2014-12-01

Interoperable sharing of groundwater data across international boarders is essential for the proper management of global water resources. However storage and management of groundwater data is often times distributed across many agencies or organizations. Furthermore these data may be represented in disparate proprietary formats, posing a significant challenge for integration. For this reason standard data models are required to achieve interoperability across geographical and political boundaries. The GroundWater Markup Language 1.0 (GWML1) was developed in 2010 as an extension of the Geography Markup Language (GML) in order to support groundwater data exchange within Spatial Data Infrastructures (SDI). In 2013, development of GWML2 was initiated under the sponsorship of the Open Geospatial Consortium (OGC) for intended adoption by the international community as the authoritative standard for the transfer of groundwater feature data, including data about water wells, aquifers, and related entities. GWML2 harmonizes GWML1 and the EU's INSPIRE models related to geology and hydrogeology. Additionally, an interoperability experiment was initiated to test the model for commercial, technical, scientific, and policy use cases. The scientific use case focuses on the delivery of data required for input into computational flow modeling software used to determine the flow of groundwater within a particular aquifer system. It involves the delivery of properties associated with hydrogeologic units, observations related to those units, and information about the related aquifers. To test this use case web services are being implemented using GWML2 and WaterML2, which is the authoritative standard for water time series observations, in order to serve USGS water well and hydrogeologic data via standard OGC protocols. Furthermore, integration of these data into a computational groundwater flow model will be tested. This submission will present the GWML2 information model and results of an interoperability experiment with a particular emphasis on the scientific use case.

Numerical modelling of wind effects on breaking waves in the surf zone

NASA Astrophysics Data System (ADS)

Xie, Zhihua

2017-10-01

Wind effects on periodic breaking waves in the surf zone have been investigated in this study using a two-phase flow model. The model solves the Reynolds-averaged Navier-Stokes equations with the k - 𝜖 turbulence model simultaneously for the flows both in the air and water. Both spilling and plunging breakers over a 1:35 sloping beach have been studied under the influence of wind, with a focus during wave breaking. Detailed information of the distribution of wave amplitudes and mean water level, wave-height-to-water-depth ratio, the water surface profiles, velocity, vorticity, and turbulence fields have been presented and discussed. The inclusion of wind alters the air flow structure above water waves, increases the generation of vorticity, and affects the wave shoaling, breaking, overturning, and splash-up processes. Wind increases the water particle velocities and causes water waves to break earlier and seaward, which agrees with the previous experiment.

Analytical theory of the hydrophobic effect of solutes in water.

PubMed

Urbic, Tomaz; Dill, Ken A

2017-09-01

We develop an analytical statistical-mechanical model for hydrophobic solvation in water. In this three-dimensional Mercedes-Benz-like model, two neighboring waters have three possible interaction states: a radial van der Waals interaction, a tetrahedral orientation-dependent hydrogen-bonding interaction, or no interaction. Nonpolar solutes are modeled as van der Waals particles of different radii. The model is sufficiently simple that we can calculate the partition function and thermal and volumetric properties of solvation versus temperature, pressure, and solute radius. Predictions are in good agreement with results of Monte Carlo simulations. And their trends agree with experiments on hydrophobic solute insertion. The theory shows that first-shell waters are more highly structured than bulk waters, because of hydrogen bonding, and that that structure melts out faster with temperature than it does in bulk waters. Because the theory is analytical, it can explore a broad range of solvation properties and anomalies of water, at minimal computational expense.

Analytical theory of the hydrophobic effect of solutes in water

NASA Astrophysics Data System (ADS)

Urbic, Tomaz; Dill, Ken A.

2017-09-01

We develop an analytical statistical-mechanical model for hydrophobic solvation in water. In this three-dimensional Mercedes-Benz-like model, two neighboring waters have three possible interaction states: a radial van der Waals interaction, a tetrahedral orientation-dependent hydrogen-bonding interaction, or no interaction. Nonpolar solutes are modeled as van der Waals particles of different radii. The model is sufficiently simple that we can calculate the partition function and thermal and volumetric properties of solvation versus temperature, pressure, and solute radius. Predictions are in good agreement with results of Monte Carlo simulations. And their trends agree with experiments on hydrophobic solute insertion. The theory shows that first-shell waters are more highly structured than bulk waters, because of hydrogen bonding, and that that structure melts out faster with temperature than it does in bulk waters. Because the theory is analytical, it can explore a broad range of solvation properties and anomalies of water, at minimal computational expense.

Laboratory-scale experiments and numerical modeling of cosolvent flushing of multi-component NAPLs in saturated porous media.

PubMed

Agaoglu, Berken; Scheytt, Traugott; Copty, Nadim K

2012-10-01

This study examines the mechanistic processes governing multiphase flow of a water-cosolvent-NAPL system in saturated porous media. Laboratory batch and column flushing experiments were conducted to determine the equilibrium properties of pure NAPL and synthetically prepared NAPL mixtures as well as NAPL recovery mechanisms for different water-ethanol contents. The effect of contact time was investigated by considering different steady and intermittent flow velocities. A modified version of multiphase flow simulator (UTCHEM) was used to compare the multiphase model simulations with the column experiment results. The effect of employing different grid geometries (1D, 2D, 3D), heterogeneity and different initial NAPL saturation configurations was also examined in the model. It is shown that the change in velocity affects the mass transfer rate between phases as well as the ultimate NAPL recovery percentage. The experiments with low flow rate flushing of pure NAPL and the 3D UTCHEM simulations gave similar effluent concentrations and NAPL cumulative recoveries. Model simulations over-estimated NAPL recovery for high specific discharges and rate-limited mass transfer, suggesting a constant mass transfer coefficient for the entire flushing experiment may not be valid. When multi-component NAPLs are present, the dissolution rate of individual organic compounds (namely, toluene and benzene) into the ethanol-water flushing solution is found not to correlate with their equilibrium solubility values. Copyright © 2012 Elsevier B.V. All rights reserved.

Rheology of water and ammonia-water ices

NASA Technical Reports Server (NTRS)

Goldsby, D. L.; Kohlstedt, D. L.; Durham, W. B.

1993-01-01

Creep experiments on fine-grained water and ammonia-water ices have been performed at one atmosphere and high confining pressure in order to develop constitutive relationships necessary to model tectonic processes and interpret surface features of icy moons of the outer solar system. The present series of experiments explores the effects of temperature, strain rate, grain size, and melt fraction on creep strength. In general, creep strength decreases with increasing temperature, decreasing strain rate, and increasing melt fraction. A transition from dislocation creep to diffusion creep occurs at finer grain sizes, higher temperatures, and lower strain rates.

A Comparison of Climate Feedback Strength between CO2 Doubling and LGM Experiments

NASA Astrophysics Data System (ADS)

Yoshimori, M.; Yokohata, T.; Abe-Ouchi, A.

2008-12-01

Studies of past climate potentially provide a constraint on the uncertainty of climate sensitivity, but previous studies warn against a simple scaling to the future. The climate sensitivity is determined by various feedback processes and they may vary with climate states and forcings. In this study, we investigate similarities and differences of feedbacks for a CO2 doubling, a last glacial maximum (LGM), and LGM greenhouse gas (GHG) forcing experiments, using an atmospheric general circulation model coupled to a slab ocean model. After computing the radiative forcing, the individual feedback strengths: water vapor, lapse rate, albedo, and cloud feedbacks, are evaluated explicitly. For this particular model, the difference in the climate sensitivity among experiments is attributed to the shortwave cloud feedback in which there is a tendency that it becomes weaker or even negative in the cooling experiments. No significant difference is found in the water vapor feedback between warming and cooling experiments by GHGs despite the nonlinear dependence of the Clausius-Clapeyron relation on temperature. The weaker water vapor feedback in the LGM experiment due to a relatively weaker tropical forcing is compensated by the stronger lapse rate feedback due to a relatively stronger extratropical forcing. A hypothesis is proposed which explains the asymmetric cloud response between warming and cooling experiments associated with a displacement of the region of mixed- phase clouds. The difference in the total feedback strength between experiments is, however, relatively small compared to the current intermodel spread, and does not necessarily preclude the use of LGM climate as a future constraint.

Field Investigation and Modeling Development for Hydrological and Carbon Cycles in Southwest Karst Region of China

NASA Astrophysics Data System (ADS)

Hu, X. B.

2017-12-01

It is required to understanding water cycle and carbon cycle processes for water resource management and pollution prevention and global warming influence in southwest karst region of China. Lijiang river basin is selected as our study region. Interdisciplinary field and laboratory experiments with various technologies are conducted to characterize the karst aquifers in detail. Key processes in the karst water cycle and carbon cycle are determined. Based on the MODFLOW-CFP model, new watershed flow and carbon cycle models are developed coupled subsurface and surface water flow models. Our study focus on the karst springshed in Mao village, the mechanisms coupling carbon cycle and water cycle are explored. This study provides basic theory and simulation method for water resource management and groundwater pollution prevention in China karst region.

Closing the loop: integrating human impacts on water resources to advanced land surface models

NASA Astrophysics Data System (ADS)

Zaitchik, B. F.; Nie, W.; Rodell, M.; Kumar, S.; Li, B.

2016-12-01

Advanced Land Surface Models (LSMs), including those used in the North American Land Data Assimilation System (NLDAS), offer a physically consistent and spatially and temporally complete analysis of the distributed water balance. These models are constrained both by physically-based process representation and by observations ingested as meteorological forcing or as data assimilation updates. As such, they have become important tools for hydrological monitoring and long-term climate analysis. The representation of water management, however, is extremely limited in these models. Recent advances have brought prognostic irrigation routines into models used in NLDAS, while assimilation of Gravity Recovery and Climate Experiment (GRACE) derived estimates of terrestrial water storage anomaly has made it possible to nudge models towards observed states in water storage below the root zone. But with few exceptions these LSMs do not account for the source of irrigation water, leading to a disconnect between the simulated water balance and the observed human impact on water resources. This inconsistency is unacceptable for long-term studies of climate change and human impact on water resources in North America. Here we define the modeling challenge, review instances of models that have begun to account for water withdrawals (e.g., CLM), and present ongoing efforts to improve representation of human impacts on water storage across models through integration of irrigation routines, water withdrawal information, and GRACE Data Assimilation in NLDAS LSMs.

Nickel absorption and kinetics in human volunteers.

PubMed

Sunderman, F W; Hopfer, S M; Sweeney, K R; Marcus, A H; Most, B M; Creason, J

1989-05-01

Mathematical modeling of the kinetics of nickel absorption, distribution, and elimination was performed in healthy human volunteers who ingested NiSO4 drinking water (Experiment 1) or added to food (Experiment 2). Nickel was analyzed by electrothermal atomic absorption spectrophotometry in serum, urine, and feces collected during 2 days before and 4 days after a specified NiSO4 dose (12 micrograms of nickel/kg, n = 4; 18 micrograms of nickel/kg, n = 4; or 50 micrograms of nickel/kg, n = 1). In Experiment 1, each of the subjects fasted 12 hr before and 3 hr after drinking one of the specified NiSO4 doses dissolved in water; in Experiment 2, the respective subjects fasted 12 hr before consuming a standard American breakfast that contained the identical dose of NiSO4 added to scrambled eggs. Kinetic analyses, using a compartmental model, provided excellent goodness-of-fit for paired data sets from all subjects. Absorbed nickel averaged 27 +/- 17% (mean +/- SD) of the dose ingested in water vs 0.7 +/- 0.4% of the same dose ingested in food (a 40-fold difference); rate constants for nickel absorption, transfer, and elimination were not significantly influenced by the oral vehicle. The elimination half-time for absorbed nickel averaged 28 +/- 9 hr. Renal clearance of nickel averaged 8.3 +/- 2.0 ml/min/1.73 m2 in Experiment 1 and 5.8 +/- 4.3 ml/min/1.73 m2 in Experiment 2. This study confirms that dietary constituents profoundly reduce the bioavailability of Ni2+ for alimentary absorption; approximately one-quarter of nickel ingested in drinking water after an over-night fast is absorbed from the human intestine and excreted in urine, compared with only 1% of nickel ingested in food. The compartmental model and kinetic parameters provided by this study will reduce the uncertainty of toxicologic risk assessments of human exposures to nickel in drinking water and food.

How ions affect the structure of water.

PubMed

Hribar, Barbara; Southall, Noel T; Vlachy, Vojko; Dill, Ken A

2002-10-16

We model ion solvation in water. We use the MB model of water, a simple two-dimensional statistical mechanical model in which waters are represented as Lennard-Jones disks having Gaussian hydrogen-bonding arms. We introduce a charge dipole into MB waters. We perform (NPT) Monte Carlo simulations to explore how water molecules are organized around ions and around nonpolar solutes in salt solutions. The model gives good qualitative agreement with experiments, including Jones-Dole viscosity B coefficients, Samoilov and Hirata ion hydration activation energies, ion solvation thermodynamics, and Setschenow coefficients for Hofmeister series ions, which describe the salt concentration dependence of the solubilities of hydrophobic solutes. The two main ideas captured here are (1) that charge densities govern the interactions of ions with water, and (2) that a balance of forces determines water structure: electrostatics (water's dipole interacting with ions) and hydrogen bonding (water interacting with neighboring waters). Small ions (kosmotropes) have high charge densities so they cause strong electrostatic ordering of nearby waters, breaking hydrogen bonds. In contrast, large ions (chaotropes) have low charge densities, and surrounding water molecules are largely hydrogen bonded.

Rapid freezing of water under dynamic compression

NASA Astrophysics Data System (ADS)

Myint, Philip C.; Belof, Jonathan L.

2018-06-01

Understanding the behavior of materials at extreme pressures is a central issue in fields like aerodynamics, astronomy, and geology, as well as for advancing technological grand challenges such as inertial confinement fusion. Dynamic compression experiments to probe high-pressure states often encounter rapid phase transitions that may cause the materials to behave in unexpected ways, and understanding the kinetics of these phase transitions remains an area of great interest. In this review, we examine experimental and theoretical/computational efforts to study the freezing kinetics of water to a high-pressure solid phase known as ice VII. We first present a detailed analysis of dynamic compression experiments in which water has been observed to freeze on sub-microsecond time scales to ice VII. This is followed by a discussion of the limitations of currently available molecular and continuum simulation methods in modeling these experiments. We then describe how our phase transition kinetics models, which are based on classical nucleation theory, provide a more physics-based framework that overcomes some of these limitations. Finally, we give suggestions on future experimental and modeling work on the liquid–ice VII transition, including an outline of the development of a predictive multiscale model in which molecular and continuum simulations are intimately coupled.

Rapid freezing of water under dynamic compression.

PubMed

Myint, Philip C; Belof, Jonathan L

2018-06-13

Understanding the behavior of materials at extreme pressures is a central issue in fields like aerodynamics, astronomy, and geology, as well as for advancing technological grand challenges such as inertial confinement fusion. Dynamic compression experiments to probe high-pressure states often encounter rapid phase transitions that may cause the materials to behave in unexpected ways, and understanding the kinetics of these phase transitions remains an area of great interest. In this review, we examine experimental and theoretical/computational efforts to study the freezing kinetics of water to a high-pressure solid phase known as ice VII. We first present a detailed analysis of dynamic compression experiments in which water has been observed to freeze on sub-microsecond time scales to ice VII. This is followed by a discussion of the limitations of currently available molecular and continuum simulation methods in modeling these experiments. We then describe how our phase transition kinetics models, which are based on classical nucleation theory, provide a more physics-based framework that overcomes some of these limitations. Finally, we give suggestions on future experimental and modeling work on the liquid-ice VII transition, including an outline of the development of a predictive multiscale model in which molecular and continuum simulations are intimately coupled.

Using models to guide field experiments: a priori predictions for the CO2 response of a nutrient- and water-limited native Eucalypt woodland.

PubMed

Medlyn, Belinda E; De Kauwe, Martin G; Zaehle, Sönke; Walker, Anthony P; Duursma, Remko A; Luus, Kristina; Mishurov, Mikhail; Pak, Bernard; Smith, Benjamin; Wang, Ying-Ping; Yang, Xiaojuan; Crous, Kristine Y; Drake, John E; Gimeno, Teresa E; Macdonald, Catriona A; Norby, Richard J; Power, Sally A; Tjoelker, Mark G; Ellsworth, David S

2016-08-01

The response of terrestrial ecosystems to rising atmospheric CO2 concentration (Ca ), particularly under nutrient-limited conditions, is a major uncertainty in Earth System models. The Eucalyptus Free-Air CO2 Enrichment (EucFACE) experiment, recently established in a nutrient- and water-limited woodland presents a unique opportunity to address this uncertainty, but can best do so if key model uncertainties have been identified in advance. We applied seven vegetation models, which have previously been comprehensively assessed against earlier forest FACE experiments, to simulate a priori possible outcomes from EucFACE. Our goals were to provide quantitative projections against which to evaluate data as they are collected, and to identify key measurements that should be made in the experiment to allow discrimination among alternative model assumptions in a postexperiment model intercomparison. Simulated responses of annual net primary productivity (NPP) to elevated Ca ranged from 0.5 to 25% across models. The simulated reduction of NPP during a low-rainfall year also varied widely, from 24 to 70%. Key processes where assumptions caused disagreement among models included nutrient limitations to growth; feedbacks to nutrient uptake; autotrophic respiration; and the impact of low soil moisture availability on plant processes. Knowledge of the causes of variation among models is now guiding data collection in the experiment, with the expectation that the experimental data can optimally inform future model improvements. © 2016 John Wiley & Sons Ltd.

Using models to guide field experiments: a priori predictions for the CO 2 response of a nutrient- and water-limited native Eucalypt woodland

DOE PAGES

Medlyn, Belinda E.; De Kauwe, Martin G.; Zaehle, Sönke; ...

2016-05-09

One major uncertainty in Earth System models is the response of terrestrial ecosystems to rising atmospheric CO 2 concentration (Ca), particularly under nutrient-lim- ited conditions. The Eucalyptus Free-Air CO 2 Enrichment (EucFACE) experiment, recently established in a nutrient- and water-limited woodlands, presents a unique opportunity to address this uncertainty, but can best do so if key model uncertainties have been identified in advance. Moreover, we applied seven vegetation models, which have previously been comprehensively assessed against earlier forest FACE experi- ments, to simulate a priori possible outcomes from EucFACE. Our goals were to provide quantitative projections against which to evaluatemore » data as they are collected, and to identify key measurements that should be made in the experiment to allow discrimination among alternative model assumptions in a postexperiment model intercompari- son. Simulated responses of annual net primary productivity (NPP) to elevated Ca ranged from 0.5 to 25% across models. The simulated reduction of NPP during a low-rainfall year also varied widely, from 24 to 70%. Key processes where assumptions caused disagreement among models included nutrient limitations to growth; feedbacks to nutri- ent uptake; autotrophic respiration; and the impact of low soil moisture availability on plant processes. Finally, knowledge of the causes of variation among models is now guiding data collection in the experiment, with the expectation that the experimental data can optimally inform future model improvements.« less

Using models to guide field experiments: a priori predictions for the CO 2 response of a nutrient- and water-limited native Eucalypt woodland

DOE Office of Scientific and Technical Information (OSTI.GOV)

Medlyn, Belinda E.; De Kauwe, Martin G.; Zaehle, Sönke

One major uncertainty in Earth System models is the response of terrestrial ecosystems to rising atmospheric CO 2 concentration (Ca), particularly under nutrient-lim- ited conditions. The Eucalyptus Free-Air CO 2 Enrichment (EucFACE) experiment, recently established in a nutrient- and water-limited woodlands, presents a unique opportunity to address this uncertainty, but can best do so if key model uncertainties have been identified in advance. Moreover, we applied seven vegetation models, which have previously been comprehensively assessed against earlier forest FACE experi- ments, to simulate a priori possible outcomes from EucFACE. Our goals were to provide quantitative projections against which to evaluatemore » data as they are collected, and to identify key measurements that should be made in the experiment to allow discrimination among alternative model assumptions in a postexperiment model intercompari- son. Simulated responses of annual net primary productivity (NPP) to elevated Ca ranged from 0.5 to 25% across models. The simulated reduction of NPP during a low-rainfall year also varied widely, from 24 to 70%. Key processes where assumptions caused disagreement among models included nutrient limitations to growth; feedbacks to nutri- ent uptake; autotrophic respiration; and the impact of low soil moisture availability on plant processes. Finally, knowledge of the causes of variation among models is now guiding data collection in the experiment, with the expectation that the experimental data can optimally inform future model improvements.« less

Testing the Structure of Hydrological Models using Genetic Programming

NASA Astrophysics Data System (ADS)

Selle, B.; Muttil, N.

2009-04-01

Genetic Programming is able to systematically explore many alternative model structures of different complexity from available input and response data. We hypothesised that genetic programming can be used to test the structure hydrological models and to identify dominant processes in hydrological systems. To test this, genetic programming was used to analyse a data set from a lysimeter experiment in southeastern Australia. The lysimeter experiment was conducted to quantify the deep percolation response under surface irrigated pasture to different soil types, water table depths and water ponding times during surface irrigation. Using genetic programming, a simple model of deep percolation was consistently evolved in multiple model runs. This simple and interpretable model confirmed the dominant process contributing to deep percolation represented in a conceptual model that was published earlier. Thus, this study shows that genetic programming can be used to evaluate the structure of hydrological models and to gain insight about the dominant processes in hydrological systems.

Water Balance in the Amazon Basin from a Land Surface Model Ensemble

NASA Technical Reports Server (NTRS)

Getirana, Augusto C. V.; Dutra, Emanuel; Guimberteau, Matthieu; Kam, Jonghun; Li, Hong-Yi; Decharme, Bertrand; Zhang, Zhengqiu; Ducharne, Agnes; Boone, Aaron; Balsamo, Gianpaolo;

Fate and Transport of Bacteriophage (MS2 and PRD1) During Field-Scale Infiltration at a Research Site in Los Angeles County, CA

NASA Astrophysics Data System (ADS)

Anders, R.; Chrysikopoulos, C. V.

2003-12-01

As the use of tertiary-treated municipal wastewater (recycled water) for replenishment purposes continues to increase, provisions are being established to protect ground-water resources by ensuring that adequate soil-retention time and distance requirements are met for pathogen removal. However, many of the factors controlling virus fate and transport (e.g. hydraulic conditions, ground-water chemistry, and sediment mineralogy) are interrelated and poorly understood. Therefore, conducting field-scale experiments using surrogates for human enteric viruses at an actual recharge basin that uses recycled water may represent the best approach for establishing adequate setback requirements. Three field-scale infiltration experiments were conducted at such a basin using bacterial viruses (bacteriophage) MS2 and PRD1 as surrogates for human viruses, bromide as a conservative tracer, and recycled water. The specific research site consists of a test basin constructed adjacent to a large recharge facility (spreading grounds) located in the Montebello Forebay of Los Angeles County, California. The soil beneath the test basin is predominantly medium to coarse, moderately sorted, grayish-brown sand. The first experiment was conducted over a 2-day period to determine the feasibility of conducting field-scale infiltration experiments using recycled water seeded with high concentrations of bacteriophage and bromide as tracers. Based on the results of the first experiment, a second experiment was completed when similar hydraulic conditions existed at the test basin. The third infiltration experiment was conducted to confirm the results obtained from the second experiment. Data were obtained for samples collected during the second and third field-scale infiltration experiments from the test basin itself and from depths of 0.3, 0.6, 1.0, 1.5, 3.0, and 7.6 m below the bottom of the test basin. These field-scale tracer experiments indicate bacteriophage are attenuated by removal and (or) inactivation during subsurface transport. To simulate the transport and fate of viruses during infiltration, a nonlinear least-squares regression program was used to fit a one-dimensional virus transport model to the experimental data. The model simulates virus transport in homogeneous, saturated porous media with first-order adsorption (or filtration) and inactivation. Furthermore, the model obtains a semi-analytical solution for the special case of a broad pulse and time-dependent source concentration using the principle of superposition. The fitted parameters include the clogging and declogging rate constants and the inactivation constants of suspended and adsorbed viruses. Preliminary results show a reasonable match of the first arrival of bacteriophage and bromide.

[Study of high temperature water vapor concentration measurement method based on absorption spectroscopy].

PubMed

Chen, Jiu-ying; Liu, Jian-guo; He, Jun-feng; He, Ya-bai; Zhang, Guang-le; Xu, Zhen-yu; Gang, Qiang; Wang, Liao; Yao, Lu; Yuan, Song; Ruan, Jun; Dai, Yun-hai; Kan, Rui-feng

2014-12-01

Tunable diode laser absorption spectroscopy (TDLAS) has been developed to realize the real-time and dynamic measurement of the combustion temperature, gas component concentration, velocity and other flow parameters, owing to its high sensitivity, fast time response, non-invasive character and robust nature. In order to obtain accurate water vapor concentration at high temperature, several absorption spectra of water vapor near 1.39 μm from 773 to 1273 K under ordinary pressure were recorded in a high temperature experiment setup using a narrow band diode laser. The absorbance of high temperature absorption spectra was calculated by combined multi-line nonlinear least squares fitting method. Two water vapor absorption lines near 7154.35 and 7157.73 cm(-1) were selected for measurement of water vapor at high temperature. A model method for high temperature water vapor concentration was first proposed. Water vapor concentration from the model method at high temperature is in accordance with theoretical reasoning, concentration measurement standard error is less than 0.2%, and the relative error is less than 6%. The feasibility of this measuring method is verified by experiment.

Water related triggering mechanisms of shallow landslides: Numerical modelling of hydraulic flows in slopes verified with field experiments

NASA Astrophysics Data System (ADS)

Broennimann, C.; Tacher, L.

2009-04-01

To assess hill slope stability and landslide triggering mechanisms, it is essential to understand the hydrogeological regime in slopes. In this work finite element models are elaborated and field experiments are carried out to study particularly shallow landslides with thickness of a few meters. The basis hypothesis of the presented research assumes that even for shallow landslides the hydrogeological role of the substratum, mostly bedrock, is determinant for the slopes behaviour, either it is draining or feeding the overlaying unstable mass. The investigated area of about 1 square kilometre is situated next to the villages Buchberg and Rüdlingen (canton Schaffhausen, Switzerland) at the border of the river Rhine. The lithology in this region is characterized mainly by horizontally layered sandstones intersected by marls from the upper seawater and the lower freshwater molasse, overlaid by soil and weathered bedrock of about 1 to 4 m thickness, both classified as silty sands. With a slope inclination of locally up to 40° the area is rather steep and characterized by continuous regressive erosion processes. During heavy rainfall events, such as the one from May 2002, shallow landslides occurred in the area affecting afforested soils as well as woodless areas. Geological field observations, infiltration and tracer tests show a fairly complicated hydrogeological character of the region. Along the slope, in the first few meters of depth, no groundwater table was found. However, seasonally controlled sources can be observed in-between outcropping bedrock. Within the sandstone, vertical faults in decametre scale oriented parallel to the Rhine that most likely opened during decompression due to the cutting of the river affect locally the hydrogeological regime by draining the slope. This implies a high grade of heterogeneity in the water flows in a local scale. Based on these conceptual hydrological and geological models, a numerical flow model was obtained using finite element software. Different scenarios of groundwater flow pattern and hydraulic head distribution in the saturated and unsaturated zones were modelled considering transient hydraulic conditions. The hydraulic pressure boundary conditions can then be introduced in a geomechanical model in order to evaluate mass movements and to estimate the soil stability. In a next step, a 10 x 30 m large test side situated inside the above mentioned study area was chosen to investigate the slopes behaviour during a triggering field experiment carried out in October 2008. With the aim to provoke a shallow landslide the test site with a mean inclination of 35° was intensely irrigated with sprinklers during 5 days (20 - 30 mm/hr). Transient soil parameters such as suction, pore water pressure and saturation at different depth, water infiltration rate, ground water table and soil movements in a mm-scale were measured. During this first field experiment, the slope remained stable. At this state the results of experiment and models suggest that: - At the experiment scale, heavy rainfall is not sufficient to trigger a mass movement if the hydrogeological conditions inside the substratum (bedrock) are not in a critical state as well. During the experiment, the bedrock was not saturated and played a draining role. - The behaviour of the local area, at the experiment scale, must be modelled within a regional scale (e.g. kilometric) to consider the role of hydraulic pressures inside the bedrock. The results obtained from the experiment will be used to refine the numeric models and to design future field experiments.

Removal of bio-aerosols by water flow on surfaces in health-care settings

NASA Astrophysics Data System (ADS)

Yu, Han; Li, Yuguo

2016-11-01

Hand hygiene is one of the most important and efficient measures to prevent infections, however the compliance with hand hygiene remains poor especially for health-care workers. To improve this situation, the mechanisms of hand cleansing need to be explored and a detailed study on the adhesion interactions for bio-aerosols on hand surfaces and the process during particles removal by flow is significant for more efficient methods to decrease infections. The first part of presentation will focus on modelling adhesion interactions between particles, like bacteria and virus, and hand surfaces with roughness in water environment. The model presented is based on the DLVO and its extended theories. The removal process comes next, which will put forward a new model to describe the removal of particles by water flow. In this model, molecular dynamics is combined with particle motion and the results by the model will be compared with experiment results and existed models (RnR, Rock & Roll). Finally, possible improvement of the study and future design of experiments will be discussed.

Xylem anisotropy and water transport--a model for the double sawcut experiment

Treesearch

Paul J. Schulte; David G. Costa

2010-01-01

Early experiments with overlapping cuts to the stems of trees demonstrated that lateral flow within the stem must be possible to allow such trees to maintain water flow to their leaves. We present a mathematical approach to considering lateral flow in stems by treating the xylem as an anisotropic medium for flow and develop an expression of its conductivity in the form...

Systematized water content calculation in cartilage using T1-mapping MR estimations: design and validation of a mathematical model.

PubMed

Shiguetomi-Medina, J M; Ramirez-Gl, J L; Stødkilde-Jørgensen, H; Møller-Madsen, B

2017-09-01

Up to 80 % of cartilage is water; the rest is collagen fibers and proteoglycans. Magnetic resonance (MR) T1-weighted measurements can be employed to calculate the water content of a tissue using T1 mapping. In this study, a method that translates T1 values into water content data was tested statistically. To develop a predictive equation, T1 values were obtained for tissue-mimicking gelatin samples. 1.5 T MRI was performed using inverse angle phase and an inverse sequence at 37 (±0.5) °C. Regions of interest were manually delineated and the mean T1 value was estimated in arbitrary units. Data were collected and modeled using linear regression. To validate the method, articular cartilage from six healthy pigs was used. The experiment was conducted in accordance with the Danish Animal Experiment Committee. Double measurements were performed for each animal. Ex vivo, all water in the tissue was extracted by lyophilization, thus allowing the volume of water to be measured. This was then compared with the predicted water content via Lin's concordance correlation coefficient at the 95 % confidence level. The mathematical model was highly significant when compared to a null model (p < 0.0001). 97.3 % of the variation in water content can be explained by absolute T1 values. Percentage water content could be predicted as 0.476 + (T1 value) × 0.000193 × 100 %. We found that there was 98 % concordance between the actual and predicted water contents. The results of this study demonstrate that MR data can be used to predict percentage water contents of cartilage samples. 3 (case-control study).

Differential water sorption studies on Kevlar 49 and As-polymerized poly(p-phenylene terephthalamide): determination of water transport properties.

PubMed

Mooney, Damian A; MacElroy, J M Don

2007-11-06

Water vapor sorption experiments have been conducted on Kevlar 49 at 30 degrees C over a range of water vapor pressures in 0-90% of saturation and on the as-polymerized form of the material at 30, 45, and 60 degrees C over a series of water vapor pressures of 0-60%, 0-25%, and 0-15%, respectively. For each of the differential steps in water vapor pressure, dynamic uptake curves were generated and analyzed according to a number of different mathematical models, including Fickian, Coaxial cylindrical, and intercalation models. The intercalation model was demonstrated to be the most successful model and considered two time-scales involved in the diffusion process, i.e., a penetrant-diffusive time-scale and a polymer-local-matrix-relaxation time-scale. The success of this model reinforces previously reported adsorption and desorption isotherms which suggested that water may penetrate into the surface layers of the polymer crystallite through a process known as intercalation.

Second-Order Chlorine Decay and Trihalomethanes Formation in a Pilot-Scale Water Distribution Systems

EPA Science Inventory

It is well known that model-building of chlorine decay in real water distribution systems is difficult because chlorine decay is influenced by many factors (e.g., bulk water demand, pipe-wall demand, piping material, flow velocity, and residence time). In this paper, experiments ...

Biodiversity effects on the water balance of an experimental grassland

NASA Astrophysics Data System (ADS)

Leimer, Sophia; Kreutziger, Yvonne; Rosenkranz, Stephan; Beßler, Holger; Engels, Christof; Oelmann, Yvonne; Weisser, Wolfgang W.; Wirth, Christian; Wilcke, Wolfgang

2013-04-01

Plant species richness increases aboveground biomass production in biodiversity experiments. Biomass production depends on and feeds back to the water balance, but it remains unclear how plant species richness influences soil water contents and water fluxes (actual evapotranspiration (ETa), downward flux (DF), and upward flux (UF)). Our objective was to determine the effects of plant species and functional richness and functional identity on soil water contents and water fluxes for two soil depths (0-0.3 and 0.3.-0.7 m). To achieve this, we used a water balance model in connection with Bayesian hierarchical modeling. We monitored soil water contents on 86 plots of a grassland plant diversity experiment in Jena, Germany between July 2002 and January 2006. In the field experiment, plant species richness (0, 1, 2, 4, 8, 16, 60) and functional group composition (0-4 functional groups: legumes, grasses, non-leguminous tall herbs, non-leguminous small herbs) were manipulated in a factorial design. Climate data (air temperature, precipitation, wind velocity, relative humidity, global radiation, soil moisture) was measured at a central climate station between July 2002 and December 2007. Root biomass data from July 2006 was available per plot. Missing water contents per plot and depth were estimated in weekly resolution for the years 2003-2007 with a Bayesian hierarchical model using measured water contents per plot and centrally measured soil moisture. To obtain ETa, DF, and UF of the two different soil depths, we modified a soil water balance model which had been developed for our study site. The model is based on changes in soil water content between subsequent observation dates and modeled potential evapotranspiration which was partitioned between soil layers according to percentage of root biomass. The presence of specific functional groups significantly changed water contents and fluxes with partly opposing effects in the two soil depths. Presence of grasses decreased water contents in both depths, DF in topsoil, and ETa in subsoil, but increased ETa in topsoil. As grasses produce less shade than other plant functional groups because of their leaf morphology, higher ETa in topsoil could be explained by higher soil evaporation. Moreover, grasses have an extensive, shallow rooting system which facilitates exhaustive water use from the upper soil layer and therefore probably decreases water contents and DF. Species richness did not significantly affect water contents and fluxes in both soil layers except that the relation between species richness and water contents in subsoil changed over time. This can be explained by two equivalent but opposite effects. Transpiration increases with biomass which is positively correlated with species richness. By contrast, soil evaporation decreases with species richness because the greater vegetation cover in species-rich communities produces more shade. We conclude that the contrasting effects of plant species richness on transpiration and evaporation counterbalance each other and that functional traits of specific plant functional groups mediate the biologically-induced changes in the water balance.

Channel Formation in Physical Experiments: Examples from Deep and Shallow Water Clastic Sedimentary Systems

NASA Astrophysics Data System (ADS)

Hoyal, D. C.; Sheets, B. A.

2005-12-01

The degree to which experimental sedimentary systems form channels has an important bearing on their applicability as analogs of large-scale natural systems, where channels and their associated landforms are ubiquitous. The internal geometry and properties (e.g., grain size, vertical succession and stacking) of many depositional landforms can be directly linked to the processes of channel initiation and evolution. Unfortunately, strong self-channelization, a prerequisite for certain natural phenomena (e.g. mouth lobe development, meandering, etc.), has been difficult to reproduce at laboratory scales. In shallow-water experiments (sub-aerial), although weak channelization develops relatively easily, as is commonly observed in gutters after a rain storm, strong channelization with well-developed banks has proved difficult to model. In deep water experiments the challenge is even greater. Despite considerable research effort experimental conditions for deep water channel initiation have only recently been identified. Experiments on the requisite conditions for channelization in shallow and deep water have been ongoing at the ExxonMobil Upstream Research Company (EMURC) for several years. By primarily manipulating the cohesiveness of the sediment supply we have developed models of distributive systems with well-defined channels in shallow water, reminiscent of fine grained river-dominated deltas like the Mississippi. In deep water we have developed models that demonstrate strong channelization and associated lobe behavior in a distributive setting, by scaling up an approach developed by another group using salt-water flows and low-density plastic sediment. The experiments highlight a number of important controls on experimental channel formation, including: (1) bed strength or cohesiveness; (2) bedform development; and (3) Reynolds number. Among these controls bed forms disrupt the channel forming instability, reducing the energy available for channelization. The fundamental channel instability develops in both laminar and turbulent flow but with important differences. The scaling of these effects is the focus of ongoing research. In general it was observed that there are strong similarities between the processes and sedimentary products in shallow and deep water systems. Further, strong channelization in EMURC experiments provides insights into the evolution of distributive systems including: (1) the cyclic process of lobe formation and channel growth at a channel mouth, (2) types of channel fill, (3) architectural differences between channel fill and lobe deposits, (4) channel backfilling and avulsion, (5) Channel initiation vs. entrenched channel phases, (6) knickpoints and channel erosion, (7) structure of overbank, levee-building flows, and (8) the role of levees in altering the distributive channel pattern.

Tracer experiments in periodical heterogeneous model porous medium

NASA Astrophysics Data System (ADS)

Majdalani, Samer; Delenne, Carole; Guinot, Vincent

2017-06-01

It is established that solute transport in homogenous porous media follows a classical 'S' shape breakthrough curve that can easily be modelled by a convection dispersion equation. In this study, we designed a Model Heterogeneous Porous Medium (MHPM) with a high degree of heterogeneity, in which the breakthrough curve does not follow the classical 'S' shape. The contrast in porosity is obtained by placing a cylindrical cavity (100% porosity) inside a 40% porosity medium composed with 1mm glass beads. Step tracing experiments are done by injecting salty water in the study column initially containing deionised water, until the outlet concentration stabilises to the input one. Several replicates of the experiment were conducted for n = 1 to 6 MHPM placed in series. The total of 116 experiments gives a high-quality database allowing the assessment of experimental uncertainty. The experimental results show that the breakthrough curve is very different from the `S' shape for small values of n, but the more n increases, the more the classical shape is recovered.

Effects of clay dispersion on aquifer storage and recovery in coastal aquifers

USGS Publications Warehouse

Konikow, Leonard F.; August, L.L.; Voss, C.I.

2001-01-01

Cyclic injection, storage, and withdrawal of freshwater in brackish aquifers is a form of aquifer storage and recovery (ASR) that can beneficially supplement water supplies in coastal areas. A 1970s field experiment in Norfolk, Virginia, showed that clay dispersion in the unconsolidated sedimentary aquifer occurred because of cation exchange on clay minerals as freshwater displaced brackish formation water. Migration of interstitial clay particles clogged pores, reduced permeability, and decreased recovery efficiency, but a calcium preflush was found to reduce clay dispersion and lead to a higher recovery efficiency. Column experiments were performed in this study to quantify the relations between permeability changes and clay mineralogy, clay content, and initial water salinity. The results of these experiments indicate that dispersion of montmorillonite clay is a primary contributor to formation damage. The reduction in permeability by clay dispersion may be expressed as a linear function of chloride content. Incorporating these simple functions into a radial, cross-sectional, variable-density, ground-water flow and transport model yielded a satisfactory simulation of the Norfolk field test - and represented an improvement over the model that ignored changes in permeability. This type of model offers a useful planning and design tool for ASR operations in coastal clastic aquifer systems.

Plantago maxima leaves extract inhibits adipogenic action of a high-fat diet in female Wistar rats.

PubMed

Tinkov, Alexey A; Nemereshina, Olga N; Popova, Elizaveta V; Polyakova, Valentina S; Gritsenko, Viktor A; Nikonorov, Alexandr A

2014-04-01

The primary objective of this study is to investigate the content of biologically active compounds producing an antioxidant effect in Plantago maxima and their influence on main mechanisms of dietary obesity development. Biologically active compounds in P. maxima were tested using paper chromatography. In in vivo experiment, high-fat-fed Wistar rats obtained P. maxima water extract for 3 months. Morphometric parameters, weight gain, serum adipokines, and cytokines, as well as oxidative stress biomarkers in rats’ tissues were evaluated. Gut microflora was also examined. Plantago maxima leaves used in the experiment contained significant amount of flavonoids, iridoids, phenol carboxylic acids, and tannins and ascorbic acid. Our in vivo experiment data demonstrate that P. maxima water extract prevents excessive adiposity in a diet-induced model. P. maxima consumption reduced serum leptin (twofold), macrophage chemoattractant protein-1 (sevenfold), tumornecrosis factor-α (25%), and interleukine-6 (26%) levels. P. maxima water extract decreased adipose tissue oxidative stress biomarkers in rats fed a high-fat diet. In addition, increased bacterial growth in the diet-induced obesity model was reversed by the P. maxima extract treatment. Plantago maxima water extract possessed antiadipogenic, antidiabetic, antiinflammatory, antioxidant activity, and normalized gut microflora in a rat model of diet-induced excessive adiposity due to a high content of biologically active compounds.

A "First Principles" Potential Energy Surface for Liquid Water from VRT Spectroscopy of Water Clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goldman, N; Leforestier, C; Saykally, R J

We present results of gas phase cluster and liquid water simulations from the recently determined VRT(ASP-W)III water dimer potential energy surface. VRT(ASP-W)III is shown to not only be a model of high ''spectroscopic'' accuracy for the water dimer, but also makes accurate predictions of vibrational ground-state properties for clusters up through the hexamer. Results of ambient liquid water simulations from VRT(ASP-W)III are compared to those from ab initio Molecular Dynamics, other potentials of ''spectroscopic'' accuracy, and to experiment. The results herein represent the first time that a ''spectroscopic'' potential surface is able to correctly model condensed phase properties of water.

Effects of Humidity Swings on Adsorption Columns for Air Revitalization: Modeling and Experiments

NASA Technical Reports Server (NTRS)

LeVan, M. Douglas; Finn, John E.

1997-01-01

Air purification systems are necessary to provide clean air in the closed environments aboard spacecraft. Trace contaminants are removed using adsorption. One major factor concerning the removal of trace contaminants is relative humidity. Water can reduce adsorption capacity and, due to constant fluctuations, its presence is difficult to incorporate into adsorption column designs. The purpose of the research was to allow for better design techniques in trace contaminant adsorption systems, especially for feeds with water present. Experiments and mathematical modeling research on effects of humidity swings on adsorption columns for air revitalization were carried out.

Statistical analysis of the induced Basel 2006 earthquake sequence: introducing a probability-based monitoring approach for Enhanced Geothermal Systems

NASA Astrophysics Data System (ADS)

Bachmann, C. E.; Wiemer, S.; Woessner, J.; Hainzl, S.

2011-08-01

Geothermal energy is becoming an important clean energy source, however, the stimulation of a reservoir for an Enhanced Geothermal System (EGS) is associated with seismic risk due to induced seismicity. Seismicity occurring due to the water injection at depth have to be well recorded and monitored. To mitigate the seismic risk of a damaging event, an appropriate alarm system needs to be in place for each individual experiment. In recent experiments, the so-called traffic-light alarm system, based on public response, local magnitude and peak ground velocity, was used. We aim to improve the pre-defined alarm system by introducing a probability-based approach; we retrospectively model the ongoing seismicity in real time with multiple statistical forecast models and then translate the forecast to seismic hazard in terms of probabilities of exceeding a ground motion intensity level. One class of models accounts for the water injection rate, the main parameter that can be controlled by the operators during an experiment. By translating the models into time-varying probabilities of exceeding various intensity levels, we provide tools which are well understood by the decision makers and can be used to determine thresholds non-exceedance during a reservoir stimulation; this, however, remains an entrepreneurial or political decision of the responsible project coordinators. We introduce forecast models based on the data set of an EGS experiment in the city of Basel. Between 2006 December 2 and 8, approximately 11 500 m3 of water was injected into a 5-km-deep well at high pressures. A six-sensor borehole array, was installed by the company Geothermal Explorers Limited (GEL) at depths between 300 and 2700 m around the well to monitor the induced seismicity. The network recorded approximately 11 200 events during the injection phase, more than 3500 of which were located. With the traffic-light system, actions where implemented after an ML 2.7 event, the water injection was reduced and then stopped after another ML 2.5 event. A few hours later, an earthquake with ML 3.4, felt within the city, occurred, which led to bleed-off of the well. A risk study was later issued with the outcome that the experiment could not be resumed. We analyse the statistical features of the sequence and show that the sequence is well modelled with the Omori-Utsu law following the termination of water injection. Based on this model, the sequence will last 31+29/-14 years to reach the background level. We introduce statistical models based on Reasenberg and Jones and Epidemic Type Aftershock Sequence (ETAS) models, commonly used to model aftershock sequences. We compare and test different model setups to simulate the sequences, varying the number of fixed and free parameters. For one class of the ETAS models, we account for the flow rate at the injection borehole. We test the models against the observed data with standard likelihood tests and find the ETAS model accounting for the on flow rate to perform best. Such a model may in future serve as a valuable tool for designing probabilistic alarm systems for EGS experiments.

Squirt flow due to interfacial water films in hydrate bearing sediments

NASA Astrophysics Data System (ADS)

Sell, Kathleen; Quintal, Beatriz; Kersten, Michael; Saenger, Erik H.

2018-05-01

Sediments containing gas hydrate dispersed in the pore space are known to show a characteristic seismic anomaly which is a high attenuation along with increasing seismic velocities. Currently, this observation cannot be fully explained albeit squirt-flow type mechanisms on the microscale have been speculated to be the cause. Recent major findings from in situ experiments, using the gas in excess and water in excess formation method, and coupled with high-resolution synchrotron-based X-ray micro-tomography, have revealed the systematic presence of thin water films between the quartz grains and the encrusting hydrate. The data obtained from these experiments underwent an image processing procedure to quantify the thicknesses and geometries of the aforementioned interfacial water films. Overall, the water films vary from sub-micrometer to a few micrometers in thickness. In addition, some of the water films interconnect through water bridges. This geometrical analysis is used to propose a new conceptual squirt flow model for hydrate bearing sediments. A series of numerical simulations is performed considering variations of the proposed model to study seismic attenuation caused by such thin water films. Our results support previous speculation that squirt flow can explain high attenuation at seismic frequencies in hydrate bearing sediments, but based on a conceptual squirt flow model which is geometrically different than those previously considered.

Regional disparities in the beneficial effects of rising CO2 concentrations on crop water productivity

NASA Astrophysics Data System (ADS)

Deryng, Delphine; Elliott, Joshua; Folberth, Christian; Müller, Christoph; Pugh, Thomas A. M.; Boote, Kenneth J.; Conway, Declan; Ruane, Alex C.; Gerten, Dieter; Jones, James W.; Khabarov, Nikolay; Olin, Stefan; Schaphoff, Sibyll; Schmid, Erwin; Yang, Hong; Rosenzweig, Cynthia

2016-08-01

Rising atmospheric CO2 concentrations ([CO2]) are expected to enhance photosynthesis and reduce crop water use. However, there is high uncertainty about the global implications of these effects for future crop production and agricultural water requirements under climate change. Here we combine results from networks of field experiments and global crop models to present a spatially explicit global perspective on crop water productivity (CWP, the ratio of crop yield to evapotranspiration) for wheat, maize, rice and soybean under elevated [CO2] and associated climate change projected for a high-end greenhouse gas emissions scenario. We find CO2 effects increase global CWP by 10[047]%-27[737]% (median[interquartile range] across the model ensemble) by the 2080s depending on crop types, with particularly large increases in arid regions (by up to 48[25;56]% for rainfed wheat). If realized in the fields, the effects of elevated [CO2] could considerably mitigate global yield losses whilst reducing agricultural consumptive water use (4-17%). We identify regional disparities driven by differences in growing conditions across agro-ecosystems that could have implications for increasing food production without compromising water security. Finally, our results demonstrate the need to expand field experiments and encourage greater consistency in modelling the effects of rising [CO2] across crop and hydrological modelling communities.

Regional Disparities in the Beneficial Effects of Rising CO2 Emissions on Crop Water Productivity

NASA Technical Reports Server (NTRS)

Deryng, Delphine; Elliott, Joshua; Folberth, Christian; Meuller, Christoph; Pugh, Thomas A. M.; Boote, Kenneth J.; Conway, Declan; Ruane, Alex C.; Gerten, Dieter; Jones, James W.;

Simple model of hydrophobic hydration.

PubMed

Lukšič, Miha; Urbic, Tomaz; Hribar-Lee, Barbara; Dill, Ken A

2012-05-31

Water is an unusual liquid in its solvation properties. Here, we model the process of transferring a nonpolar solute into water. Our goal was to capture the physical balance between water's hydrogen bonding and van der Waals interactions in a model that is simple enough to be nearly analytical and not heavily computational. We develop a 2-dimensional Mercedes-Benz-like model of water with which we compute the free energy, enthalpy, entropy, and the heat capacity of transfer as a function of temperature, pressure, and solute size. As validation, we find that this model gives the same trends as Monte Carlo simulations of the underlying 2D model and gives qualitative agreement with experiments. The advantages of this model are that it gives simple insights and that computational time is negligible. It may provide a useful starting point for developing more efficient and more realistic 3D models of aqueous solvation.

Gauging Through the Crowd: A Crowd-Sourcing Approach to Urban Rainfall Measurement and Storm Water Modeling Implications

NASA Astrophysics Data System (ADS)

Yang, Pan; Ng, Tze Ling

2017-11-01

Accurate rainfall measurement at high spatial and temporal resolutions is critical for the modeling and management of urban storm water. In this study, we conduct computer simulation experiments to test the potential of a crowd-sourcing approach, where smartphones, surveillance cameras, and other devices act as precipitation sensors, as an alternative to the traditional approach of using rain gauges to monitor urban rainfall. The crowd-sourcing approach is promising as it has the potential to provide high-density measurements, albeit with relatively large individual errors. We explore the potential of this approach for urban rainfall monitoring and the subsequent implications for storm water modeling through a series of simulation experiments involving synthetically generated crowd-sourced rainfall data and a storm water model. The results show that even under conservative assumptions, crowd-sourced rainfall data lead to more accurate modeling of storm water flows as compared to rain gauge data. We observe the relative superiority of the crowd-sourcing approach to vary depending on crowd participation rate, measurement accuracy, drainage area, choice of performance statistic, and crowd-sourced observation type. A possible reason for our findings is the differences between the error structures of crowd-sourced and rain gauge rainfall fields resulting from the differences between the errors and densities of the raw measurement data underlying the two field types.

Experimental vs. modeled water use in mature Norway spruce (Picea abies) exposed to elevated CO2

PubMed Central

Leuzinger, Sebastian; Bader, Martin K.-F.

2012-01-01

Rising levels of atmospheric CO2 have often been reported to reduce plant water use. Such behavior is also predicted by standard equations relating photosynthesis, stomatal conductance, and atmospheric CO2 concentration, which form the core of dynamic global vegetation models (DGVMs). Here, we provide first results from a free air CO2 enrichment (FACE) experiment with naturally growing, mature (35 m) Picea abies (L.) (Norway spruce) and compare them to simulations by the DGVM LPJ-GUESS. We monitored sap flow, stem water deficit, stomatal conductance, leaf water potential, and soil moisture in five 35–40 m tall CO2-treated (550 ppm) trees over two seasons. Using LPJ-GUESS, we simulated this experiment using climate data from a nearby weather station. While the model predicted a stable reduction of transpiration of between 9% and 18% (at concentrations of 550–700 ppm atmospheric CO2), the combined evidence from various methods characterizing water use in our experimental trees suggest no changes in response to future CO2 concentrations. The discrepancy between the modeled and the experimental results may be a scaling issue: while dynamic vegetation models correctly predict leaf-level responses, they may not sufficiently account for the processes involved at the canopy and ecosystem scale, which could offset the first-order stomatal response. PMID:23087696

Identification of glacial meltwater runoff in a karstic environment and its implication for present and future water availability

NASA Astrophysics Data System (ADS)

Finger, D.; Hugentobler, A.; Huss, M.; Voinesco, A.; Wernli, H.; Fischer, D.; Weber, E.; Jeannin, P.-Y.; Kauzlaric, M.; Wirz, A.; Vennemann, T.; Hüsler, F.; Schädler, B.; Weingartner, R.

2013-08-01

Glaciers all over the world are expected to continue to retreat due to the global warming throughout the 21st century. Consequently, future seasonal water availability might become scarce once glacier areas have declined below a certain threshold affecting future water management strategies. Particular attention should be paid to glaciers located in a karstic environment, as parts of the meltwater can be drained by underlying karst systems, making it difficult to assess water availability. In this study tracer experiments, karst modeling and glacier melt modeling are combined in order to identify flow paths in a high alpine, glacierized, karstic environment (Glacier de la Plaine Morte, Switzerland) and to investigate current and predict future downstream water availability. Flow paths through the karst underground were determined with natural and fluorescent tracers. Subsequently, geologic information and the findings from tracer experiments were assembled in a karst model. Finally, glacier melt projections driven with a climate scenario were performed to discuss future water availability in the area surrounding the glacier. The results suggest that during late summer glacier meltwater is rapidly drained through well-developed channels at the glacier bottom to the north of the glacier, while during low flow season meltwater enters into the karst and is drained to the south. Climate change projections with the glacier melt model reveal that by the end of the century glacier melt will be significantly reduced in the summer, jeopardizing water availability in glacier-fed karst springs.

Plant functional diversity increases grassland productivity-related water vapor fluxes: an Ecotron and modeling approach.

PubMed

Milcu, Alexandru; Eugster, Werner; Bachmann, Dörte; Guderle, Marcus; Roscher, Christiane; Gockele, Annette; Landais, Damien; Ravel, Olivier; Gessler, Arthur; Lange, Markus; Ebeling, Anne; Weisser, Wolfgang W; Roy, Jacques; Hildebrandt, Anke; Buchmann, Nina

2016-08-01

The impact of species richness and functional diversity of plants on ecosystem water vapor fluxes has been little investigated. To address this knowledge gap, we combined a lysimeter setup in a controlled environment facility (Ecotron) with large ecosystem samples/monoliths originating from a long-term biodiversity experiment (The Jena Experiment) and a modeling approach. Our goals were (1) quantifying the impact of plant species richness (four vs. 16 species) on day- and nighttime ecosystem water vapor fluxes; (2) partitioning ecosystem evapotranspiration into evaporation and plant transpiration using the Shuttleworth and Wallace (SW) energy partitioning model; and (3) identifying the most parsimonious predictors of water vapor fluxes using plant functional-trait-based metrics such as functional diversity and community weighted means. Daytime measured and modeled evapotranspiration were significantly higher in the higher plant diversity treatment, suggesting increased water acquisition. The SW model suggests that, at low plant species richness, a higher proportion of the available energy was diverted to evaporation (a non-productive flux), while, at higher species richness, the proportion of ecosystem transpiration (a productivity-related water flux) increased. While it is well established that LAI controls ecosystem transpiration, here we also identified that the diversity of leaf nitrogen concentration among species in a community is a consistent predictor of ecosystem water vapor fluxes during daytime. The results provide evidence that, at the peak of the growing season, higher leaf area index (LAI) and lower percentage of bare ground at high plant diversity diverts more of the available water to transpiration, a flux closely coupled with photosynthesis and productivity. Higher rates of transpiration presumably contribute to the positive effect of diversity on productivity. © 2016 by the Ecological Society of America.

Microwave Remote Sensing and the Cold Land Processes Field Experiment

NASA Technical Reports Server (NTRS)

Kim, Edward J.; Cline, Don; Davis, Bert; Hildebrand, Peter H. (Technical Monitor)

2001-01-01

The Cold Land Processes Field Experiment (CLPX) has been designed to advance our understanding of the terrestrial cryosphere. Developing a more complete understanding of fluxes, storage, and transformations of water and energy in cold land areas is a critical focus of the NASA Earth Science Enterprise Research Strategy, the NASA Global Water and Energy Cycle (GWEC) Initiative, the Global Energy and Water Cycle Experiment (GEWEX), and the GEWEX Americas Prediction Project (GAPP). The movement of water and energy through cold regions in turn plays a large role in ecological activity and biogeochemical cycles. Quantitative understanding of cold land processes over large areas will require synergistic advancements in 1) understanding how cold land processes, most comprehensively understood at local or hillslope scales, extend to larger scales, 2) improved representation of cold land processes in coupled and uncoupled land-surface models, and 3) a breakthrough in large-scale observation of hydrologic properties, including snow characteristics, soil moisture, the extent of frozen soils, and the transition between frozen and thawed soil conditions. The CLPX Plan has been developed through the efforts of over 60 interested scientists that have participated in the NASA Cold Land Processes Working Group (CLPWG). This group is charged with the task of assessing, planning and implementing the required background science, technology, and application infrastructure to support successful land surface hydrology remote sensing space missions. A major product of the experiment will be a comprehensive, legacy data set that will energize many aspects of cold land processes research. The CLPX will focus on developing the quantitative understanding, models, and measurements necessary to extend our local-scale understanding of water fluxes, storage, and transformations to regional and global scales. The experiment will particularly emphasize developing a strong synergism between process-oriented understanding, land surface models and microwave remote sensing. The experimental design is a multi-sensor, multi-scale (1-ha to 160,000 km ^ {2}) approach to providing the comprehensive data set necessary to address several experiment objectives. A description focusing on the microwave remote sensing components (ground, airborne, and spaceborne) of the experiment will be presented.

Drought and Water Supply. Implications of the Massachusetts Experience for Municipal Planning.

ERIC Educational Resources Information Center

Russell, Clifford S.; And Others

This book uses the 1962-66 Massachusetts drought data as a base of information to build a planning model of water resources that is of interest to students and professionals involved with water management. Using a demand-supply ratio to measure the relative inadequacy of a given water system, the authors then project demand into the drought period…

The Boson peak in supercooled water.

PubMed

Kumar, Pradeep; Wikfeldt, K Thor; Schlesinger, Daniel; Pettersson, Lars G M; Stanley, H Eugene

2013-01-01

We perform extensive molecular dynamics simulations of the TIP4P/2005 model of water to investigate the origin of the Boson peak reported in experiments on supercooled water in nanoconfined pores, and in hydration water around proteins. We find that the onset of the Boson peak in supercooled bulk water coincides with the crossover to a predominantly low-density-like liquid below the Widom line TW. The frequency and onset temperature of the Boson peak in our simulations of bulk water agree well with the results from experiments on nanoconfined water. Our results suggest that the Boson peak in water is not an exclusive effect of confinement. We further find that, similar to other glass-forming liquids, the vibrational modes corresponding to the Boson peak are spatially extended and are related to transverse phonons found in the parent crystal, here ice Ih.

Virtual laboratories: new opportunities for collaborative water science

NASA Astrophysics Data System (ADS)

Ceola, Serena; Arheimer, Berit; Bloeschl, Guenter; Baratti, Emanuele; Capell, Rene; Castellarin, Attilio; Freer, Jim; Han, Dawei; Hrachowitz, Markus; Hundecha, Yeshewatesfa; Hutton, Christopher; Lindström, Goran; Montanari, Alberto; Nijzink, Remko; Parajka, Juraj; Toth, Elena; Viglione, Alberto; Wagener, Thorsten

2015-04-01

Reproducibility and repeatability of experiments are the fundamental prerequisites that allow researchers to validate results and share hydrological knowledge, experience and expertise in the light of global water management problems. Virtual laboratories offer new opportunities to enable these prerequisites since they allow experimenters to share data, tools and pre-defined experimental procedures (i.e. protocols). Here we present the outcomes of a first collaborative numerical experiment undertaken by five different international research groups in a virtual laboratory to address the key issues of reproducibility and repeatability. Moving from the definition of accurate and detailed experimental protocols, a rainfall-runoff model was independently applied to 15 European catchments by the research groups and model results were collectively examined through a web-based discussion. We found that a detailed modelling protocol was crucial to ensure the comparability and reproducibility of the proposed experiment across groups. Our results suggest that sharing comprehensive and precise protocols and running the experiments within a controlled environment (e.g. virtual laboratory) is as fundamental as sharing data and tools for ensuring experiment repeatability and reproducibility across the broad scientific community and thus advancing hydrology in a more coherent way.

Development of a method for comprehensive water quality forecasting and its application in Miyun reservoir of Beijing, China.

PubMed

Zhang, Lei; Zou, Zhihong; Shan, Wei

2017-06-01

Water quality forecasting is an essential part of water resource management. Spatiotemporal variations of water quality and their inherent constraints make it very complex. This study explored a data-based method for short-term water quality forecasting. Prediction of water quality indicators including dissolved oxygen, chemical oxygen demand by KMnO 4 and ammonia nitrogen using support vector machine was taken as inputs of the particle swarm algorithm based optimal wavelet neural network to forecast the whole status index of water quality. Gubeikou monitoring section of Miyun reservoir in Beijing, China was taken as the study case to examine effectiveness of this approach. The experiment results also revealed that the proposed model has advantages of stability and time reduction in comparison with other data-driven models including traditional BP neural network model, wavelet neural network model and Gradient Boosting Decision Tree model. It can be used as an effective approach to perform short-term comprehensive water quality prediction. Copyright © 2016. Published by Elsevier B.V.

Removal of emerging micropollutants from water using cyclodextrin.

PubMed

Nagy, Zsuzsanna Magdolna; Molnár, Mónika; Fekete-Kertész, Ildikó; Molnár-Perl, Ibolya; Fenyvesi, Éva; Gruiz, Katalin

2014-07-01

Small scale laboratory experiment series were performed to study the suitability of a cyclodextrin-based sorbent (ß-cyclodextrin bead polymer, BCDP) for modelling the removal of micropollutants from drinking water and purified waste water using simulated inflow test solutions containing target analytes (ibuprofen, naproxen, ketoprofen, bisphenol-A, diclofenac, β-estradiol, ethinylestradiol, estriol, cholesterol at 2-6 μg/L level). This work was focused on the preliminary evaluation of BCDP as a sorbent in two different model systems (filtration and fluidization) applied for risk reduction of emerging micropollutants. For comparison different filter systems combined with various sorbents (commercial filter and activated carbon) were applied and evaluated in the filtration experiment series. The spiked test solution (inflow) and the treated outflows were characterized by an integrated methodology including chemical analytical methods gas chromatography-tandem mass spectrometry (GC-MS/MS) and various environmental toxicity tests to determine the efficiency and selectivity of the applied sorbents. Under experimental conditions the cyclodextrin-based filters used for purification of drinking water in most cases were able to absorb more than 90% of the bisphenol-A and of the estrogenic compounds. Both the analytical chemistry and toxicity results showed efficient elimination of these pollutants. Especially the toxicity of the filtrate decreased considerably. Laboratory experiment modelling post-purification of waste water was also performed applying fluidization technology by ß-cyclodextrin bead polymer. The BCDP removed efficiently from the spiked test solution most of the micropollutants, especially the bisphenol-A (94%) and the hormones (87-99%) The results confirmed that the BCDP-containing sorbents provide a good solution to water quality problems and they are able to decrease the load and risk posed by micropollutants to the water systems. Copyright © 2014 Elsevier B.V. All rights reserved.

Water-water correlations in electrolyte solutions probed by hyper-Rayleigh scattering

NASA Astrophysics Data System (ADS)

Shelton, David P.

2017-12-01

Long-range ion-induced correlations between water molecules have been observed by second-harmonic or hyper-Rayleigh scattering experiments with conflicting results. The most recent work observed a large difference between the results for H2O and D2O, and large discrepancies with the previously proposed theory. However, the present observations are in quantitative agreement with the model where the ion electric field induces second harmonic generation by the water molecules, and ion-ion correlations given by the Debye-Huckel theory account for intensity saturation at high ion concentration. This work compares experimental results with theory and addresses the apparent discrepancies with previous experiments.

Analysis of terahertz dielectric properties of pork tissue

NASA Astrophysics Data System (ADS)

Huang, Yuqing; Xie, Qiaoling; Sun, Ping

2017-10-01

Seeing that about 70% component of fresh biological tissues is water, many scientists try to use water models to describe the dielectric properties of biological tissues. The classical water dielectric models are Debye model, Double Debye model and Cole-Cole model. This work aims to determine a suitable model by comparing three models above with experimental data. These models are applied to fresh pork tissue. By means of least square method, the parameters of different models are fitted with the experimental data. Comparing different models on both dielectric function, the Cole-Cole model is verified the best to describe the experiments of pork tissue. The correction factor α of the Cole-Cole model is an important modification for biological tissues. So Cole-Cole model is supposed to be a priority selection to describe the dielectric properties for biological tissues in the terahertz range.

Insight into the hydraulics and resilience of Ponderosa pine seedlings using a mechanistic ecohydrologic model

NASA Astrophysics Data System (ADS)

Maneta, M. P.; Simeone, C.; Dobrowski, S.; Holden, Z.; Sapes, G.; Sala, A.; Begueria, S.

2017-12-01

In semiarid regions, drought-induced seedling mortality is considered to be caused by failure in the tree hydraulic column. Understanding the mechanisms that cause hydraulic failure and death in seedlings is important, among other things, to diagnose where some tree species may fail to regenerate, triggering demographic imbalances in the forest that could result in climate-driven shifts of tree species. Ponderosa pine is a common lower tree line species in the western US. Seedlings of ponderosa pine are often subject to low soil water potentials, which require lower water potentials in the xylem and leaves to maintain the negative pressure gradient that drives water upward. The resilience of the hydraulic column to hydraulic tension is species dependent, but from greenhouse experiments, we have identified general tension thresholds beyond which loss of xylem conductivity becomes critical, and mortality in Ponderosa pine seedlings start to occur. We describe this hydraulic behavior of plants using a mechanistic soil-vegetation-atmosphere transfer model. Before we use this models to understand water-stress induced seedling mortality at the landscape scale, we perform a modeling analysis of the dynamics of soil moisture, transpiration, leaf water potential and loss of plant water conductivity using detailed data from our green house experiments. The analysis is done using a spatially distributed model that simulates water fluxes, energy exchanges and water potentials in the soil-vegetation-atmosphere continuum. Plant hydraulic and physiological parameters of this model were calibrated using Monte Carlo methods against information on soil moisture, soil hydraulic potential, transpiration, leaf water potential and percent loss of conductivity in the xylem. This analysis permits us to construct a full portrait of the parameter space for Ponderosa pine seedling and generate posterior predictive distributions of tree response to understand the sensitivity of transpiration, hydraulic tension in the plant, and percent loss of conductivity to environmental stresses.

Experimental study on the heat transfer characteristics of a nuclear reactor containment wall cooled by gravitationally falling water

NASA Astrophysics Data System (ADS)

Pasek, Ari D.; Umar, Efrison; Suwono, Aryadi; Manalu, Reinhard E. E.

2012-06-01

Gravitationally falling water cooling is one of mechanism utilized by a modern nuclear Pressurized Water Reactor (PWR) for its Passive Containment Cooling System (PCCS). Since the cooling is closely related to the safety, water film cooling characteristics of the PCCS should be studied. This paper deals with the experimental study of laminar water film cooling on the containment model wall. The influences of water mass flow rate and wall heat rate on the heat transfer characteristic were studied. This research was started with design and assembly of a containment model equipped with the water cooling system, and calibration of all measurement devices. The containment model is a scaled down model of AP 1000 reactor. Below the containment steam is generated using electrical heaters. The steam heated the containment wall, and then the temperatures of the wall in several positions were measure transiently using thermocouples and data acquisition. The containment was then cooled by falling water sprayed from the top of the containment. The experiments were done for various wall heat rate and cooling water flow rate. The objective of the research is to find the temperature profile along the wall before and after the water cooling applied, prediction of the water film characteristic such as means velocity, thickness and their influence to the heat transfer coefficient. The result of the experiments shows that the wall temperatures significantly drop after being sprayed with water. The thickness of water film increases with increasing water flow rate and remained constant with increasing wall heat rate. The heat transfer coefficient decreases as film mass flow rate increase due to the increases of the film thickness which causes the increasing of the thermal resistance. The heat transfer coefficient increases slightly as the wall heat rate increases. The experimental results were then compared with previous theoretical studied.

Project Fog Drops 5. Task 1: A numerical model of advection fog. Task 2: Recommendations for simplified individual zero-gravity cloud physics experiments

NASA Technical Reports Server (NTRS)

Rogers, C. W.; Eadie, W. J.; Katz, U.; Kocmond, W. C.

1975-01-01

A two-dimensional numerical model was used to investigate the formation of marine advection fog. The model predicts the evolution of potential temperature, horizontal wind, water vapor content, and liquid water content in a vertical cross section of the atmosphere as determined by vertical turbulent transfer and horizontal advection, as well as radiative cooling and drop sedimentation. The model is designed to simulate the formation, development, or dissipation of advection fog in response to transfer of heat and moisture between the atmosphere and the surface as driven by advection over horizontal discontinuities in the surface temperature. Results from numerical simulations of advection fog formation are discussed with reference to observations of marine fog. A survey of candidate fog or cloud microphysics experiments which might be performed in the low gravity environment of a shuttle-type spacecraft in presented. Recommendations are given for relatively simple experiments which are relevent to fog modification problems.

Inverse Modeling of Water-Rock-CO2 Batch Experiments: Potential Impacts on Groundwater Resources at Carbon Sequestration Sites.

PubMed

Yang, Changbing; Dai, Zhenxue; Romanak, Katherine D; Hovorka, Susan D; Treviño, Ramón H

2014-01-01

This study developed a multicomponent geochemical model to interpret responses of water chemistry to introduction of CO2 into six water-rock batches with sedimentary samples collected from representative potable aquifers in the Gulf Coast area. The model simulated CO2 dissolution in groundwater, aqueous complexation, mineral reactions (dissolution/precipitation), and surface complexation on clay mineral surfaces. An inverse method was used to estimate mineral surface area, the key parameter for describing kinetic mineral reactions. Modeling results suggested that reductions in groundwater pH were more significant in the carbonate-poor aquifers than in the carbonate-rich aquifers, resulting in potential groundwater acidification. Modeled concentrations of major ions showed overall increasing trends, depending on mineralogy of the sediments, especially carbonate content. The geochemical model confirmed that mobilization of trace metals was caused likely by mineral dissolution and surface complexation on clay mineral surfaces. Although dissolved inorganic carbon and pH may be used as indicative parameters in potable aquifers, selection of geochemical parameters for CO2 leakage detection is site-specific and a stepwise procedure may be followed. A combined study of the geochemical models with the laboratory batch experiments improves our understanding of the mechanisms that dominate responses of water chemistry to CO2 leakage and also provides a frame of reference for designing monitoring strategy in potable aquifers.

Biodegradation of phenol, salicylic acid, benzenesulfonic acid, and iomeprol by Pseudomonas fluorescens in the capillary fringe

NASA Astrophysics Data System (ADS)

Hack, Norman; Reinwand, Christian; Abbt-Braun, Gudrun; Horn, Harald; Frimmel, Fritz H.

2015-12-01

Mass transfer and biological transformation phenomena in the capillary fringe were studied using phenol, salicylic acid, benzenesulfonic acid, and the iodinated X-ray contrast agent iomeprol as model organic compounds and the microorganism strain Pseudomonas fluorescens. Three experimental approaches were used: Batch experiments (uniform water saturation and transport by diffusion), in static columns (with a gradient of water saturation and advective transport in the capillaries) and in a flow-through cell (with a gradient of water saturation and transport by horizontal and vertical flow: 2-dimension flow-through microcosm). The reactors employed for the experiments were filled with quartz sand of defined particle size distribution (dp = 200…600 μm, porosity ε = 0.42). Batch experiments showed that phenol and salicylic acid have a high, whereas benzenesulfonic acid and iomeprol have a quite low potential for biodegradation under aerobic conditions and in a matrix nearly close to water saturation. Batch experiments under anoxic conditions with nitrate as electron acceptor revealed that the biodegradation of the model compounds was lower than under aerobic conditions. Nevertheless, the experiments showed that the moisture content was also responsible for an optimized transport in the liquid phase of a porous medium. Biodegradation in the capillary fringe was found to be influenced by both the moisture content and availability of the dissolved substrate, as seen in static column experiments. The gas-liquid mass transfer of oxygen also played an important role for the biological activity. In static column experiments under aerobic conditions, the highest biodegradation was found in the capillary fringe (e.g. βt/β0 (phenol) = 0 after t = 6 d) relative to the zone below the water table and unsaturated zone. The highest biodegradation occurred in the flow-through cell experiment where the height of the capillary fringe was largest.

Biodegradation of phenol, salicylic acid, benzenesulfonic acid, and iomeprol by Pseudomonas fluorescens in the capillary fringe.

PubMed

Hack, Norman; Reinwand, Christian; Abbt-Braun, Gudrun; Horn, Harald; Frimmel, Fritz H

2015-12-01

Mass transfer and biological transformation phenomena in the capillary fringe were studied using phenol, salicylic acid, benzenesulfonic acid, and the iodinated X-ray contrast agent iomeprol as model organic compounds and the microorganism strain Pseudomonas fluorescens. Three experimental approaches were used: Batch experiments (uniform water saturation and transport by diffusion), in static columns (with a gradient of water saturation and advective transport in the capillaries) and in a flow-through cell (with a gradient of water saturation and transport by horizontal and vertical flow: 2-dimension flow-through microcosm). The reactors employed for the experiments were filled with quartz sand of defined particle size distribution (dp=200...600 μm, porosity ε=0.42). Batch experiments showed that phenol and salicylic acid have a high, whereas benzenesulfonic acid and iomeprol have a quite low potential for biodegradation under aerobic conditions and in a matrix nearly close to water saturation. Batch experiments under anoxic conditions with nitrate as electron acceptor revealed that the biodegradation of the model compounds was lower than under aerobic conditions. Nevertheless, the experiments showed that the moisture content was also responsible for an optimized transport in the liquid phase of a porous medium. Biodegradation in the capillary fringe was found to be influenced by both the moisture content and availability of the dissolved substrate, as seen in static column experiments. The gas-liquid mass transfer of oxygen also played an important role for the biological activity. In static column experiments under aerobic conditions, the highest biodegradation was found in the capillary fringe (e.g. βt/β0 (phenol)=0 after t=6 d) relative to the zone below the water table and unsaturated zone. The highest biodegradation occurred in the flow-through cell experiment where the height of the capillary fringe was largest. Copyright © 2015 Elsevier B.V. All rights reserved.

Long-Term Monitoring of Rainfed Wheat Yield and Soil Water at the Loess Plateau Reveals Low Water Use Efficiency

PubMed Central

Qin, Wei; Chi, Baoliang; Oenema, Oene

2013-01-01

Increasing crop yield and water use efficiency (WUE) in dryland farming requires a quantitative understanding of relationships between crop yield and the water balance over many years. Here, we report on a long-term dryland monitoring site at the Loess Plateau, Shanxi, China, where winter wheat was grown for 30 consecutive years and soil water content (0–200 cm) was measured every 10 days. The monitoring data were used to calibrate the AquaCrop model and then to analyse the components of the water balance. There was a strong positive relationship between total available water and mean cereal yield. However, only one-third of the available water was actually used by the winter wheat for crop transpiration. The remaining two-thirds were lost by soil evaporation, of which 40 and 60% was lost during the growing and fallow seasons, respectively. Wheat yields ranged from 0.6 to 3.9 ton/ha and WUE from 0.3 to 0.9 kg/m3. Results of model experiments suggest that minimizing soil evaporation via straw mulch or plastic film covers could potentially double wheat yields and WUE. We conclude that the relatively low wheat yields and low WUE were mainly related to (i) limited rainfall, (ii) low soil water storage during fallow season due to large soil evaporation, and (iii) poor synchronisation of the wheat growing season to the rain season. The model experiments suggest significant potential for increased yields and WUE. PMID:24302987

CRBR pump water test experience

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cook, M.E.; Huber, K.A.

1983-01-01

The hydraulic design features and water testing of the hydraulic scale model and prototype pump of the sodium pumps used in the primary and intermediate sodium loops of the Clinch River Breeder Reactor Plant (CRBRP) are described. The Hydraulic Scale Model tests are performed and the results of these tests are discussed. The Prototype Pump tests are performed and the results of these tests are discussed.

A simple, efficient polarizable coarse-grained water model for molecular dynamics simulations.

PubMed

Riniker, Sereina; van Gunsteren, Wilfred F

2011-02-28

The development of coarse-grained (CG) models that correctly represent the important features of compounds is essential to overcome the limitations in time scale and system size currently encountered in atomistic molecular dynamics simulations. Most approaches reported in the literature model one or several molecules into a single uncharged CG bead. For water, this implicit treatment of the electrostatic interactions, however, fails to mimic important properties, e.g., the dielectric screening. Therefore, a coarse-grained model for water is proposed which treats the electrostatic interactions between clusters of water molecules explicitly. Five water molecules are embedded in a spherical CG bead consisting of two oppositely charged particles which represent a dipole. The bond connecting the two particles in a bead is unconstrained, which makes the model polarizable. Experimental and all-atom simulated data of liquid water at room temperature are used for parametrization of the model. The experimental density and the relative static dielectric permittivity were chosen as primary target properties. The model properties are compared with those obtained from experiment, from clusters of simple-point-charge water molecules of appropriate size in the liquid phase, and for other CG water models if available. The comparison shows that not all atomistic properties can be reproduced by a CG model, so properties of key importance have to be selected when coarse graining is applied. Yet, the CG model reproduces the key characteristics of liquid water while being computationally 1-2 orders of magnitude more efficient than standard fine-grained atomistic water models.

Application of spectral decomposition algorithm for mapping water quality in a turbid lake (Lake Kasumigaura, Japan) from Landsat TM data

NASA Astrophysics Data System (ADS)

Oyama, Youichi; Matsushita, Bunkei; Fukushima, Takehiko; Matsushige, Kazuo; Imai, Akio

The remote sensing of Case 2 water has been far less successful than that of Case 1 water, due mainly to the complex interactions among optically active substances (e.g., phytoplankton, suspended sediments, colored dissolved organic matter, and water) in the former. To address this problem, we developed a spectral decomposition algorithm (SDA), based on a spectral linear mixture modeling approach. Through a tank experiment, we found that the SDA-based models were superior to conventional empirical models (e.g. using single band, band ratio, or arithmetic calculation of band) for accurate estimates of water quality parameters. In this paper, we develop a method for applying the SDA to Landsat-5 TM data on Lake Kasumigaura, a eutrophic lake in Japan characterized by high concentrations of suspended sediment, for mapping chlorophyll-a (Chl-a) and non-phytoplankton suspended sediment (NPSS) distributions. The results show that the SDA-based estimation model can be obtained by a tank experiment. Moreover, by combining this estimation model with satellite-SRSs (standard reflectance spectra: i.e., spectral end-members) derived from bio-optical modeling, we can directly apply the model to a satellite image. The same SDA-based estimation model for Chl-a concentration was applied to two Landsat-5 TM images, one acquired in April 1994 and the other in February 2006. The average Chl-a estimation error between the two was 9.9%, a result that indicates the potential robustness of the SDA-based estimation model. The average estimation error of NPSS concentration from the 2006 Landsat-5 TM image was 15.9%. The key point for successfully applying the SDA-based estimation model to satellite data is the method used to obtain a suitable satellite-SRS for each end-member.

Unraveling the hydrodynamics of split root water uptake experiments using CT scanned root architectures and three dimensional flow simulations

PubMed Central

Koebernick, Nicolai; Huber, Katrin; Kerkhofs, Elien; Vanderborght, Jan; Javaux, Mathieu; Vereecken, Harry; Vetterlein, Doris

2015-01-01

Split root experiments have the potential to disentangle water transport in roots and soil, enabling the investigation of the water uptake pattern of a root system. Interpretation of the experimental data assumes that water flow between the split soil compartments does not occur. Another approach to investigate root water uptake is by numerical simulations combining soil and root water flow depending on the parameterization and description of the root system. Our aim is to demonstrate the synergisms that emerge from combining split root experiments with simulations. We show how growing root architectures derived from temporally repeated X-ray CT scanning can be implemented in numerical soil-plant models. Faba beans were grown with and without split layers and exposed to a single drought period during which plant and soil water status were measured. Root architectures were reconstructed from CT scans and used in the model R-SWMS (root-soil water movement and solute transport) to simulate water potentials in soil and roots in 3D as well as water uptake by growing roots in different depths. CT scans revealed that root development was considerably lower with split layers compared to without. This coincided with a reduction of transpiration, stomatal conductance and shoot growth. Simulated predawn water potentials were lower in the presence of split layers. Simulations showed that this was related to an increased resistance to vertical water flow in the soil by the split layers. Comparison between measured and simulated soil water potentials proved that the split layers were not perfectly isolating and that redistribution of water from the lower, wetter compartments to the drier upper compartments took place, thus water losses were not equal to the root water uptake from those compartments. Still, the layers increased the resistance to vertical flow which resulted in lower simulated collar water potentials that led to reduced stomatal conductance and growth. PMID:26074935

Relationship between the line of density anomaly and the lines of melting, crystallization, cavitation, and liquid spinodal in coarse-grained water models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Jibao; Molinero, Valeria, E-mail: Valeria.Molinero@utah.edu; Chakravarty, Charusita

2016-06-21

Liquid water has several anomalous properties, including a non-monotonous dependence of density with temperature and an increase of thermodynamic response functions upon supercooling. Four thermodynamic scenarios have been proposed to explain the anomalies of water, but it is not yet possible to decide between them from experiments because of the crystallization and cavitation of metastable liquid water. Molecular simulations provide a versatile tool to study the anomalies and phase behavior of water, assess their agreement with the phenomenology of water under conditions accessible to experiments, and provide insight into the behavior of water in regions that are challenging to probemore » in the laboratory. Here we investigate the behavior of the computationally efficient monatomic water models mW and mTIP4P/2005{sup REM}, with the aim of unraveling the relationships between the lines of density extrema in the p-T plane, and the lines of melting, liquid-vapor spinodal and non-equilibrium crystallization and cavitation. We focus particularly on the conditions for which the line of density maxima (LDM) in the liquid emerges and disappears as the pressure is increased. We find that these models present a retracing LDM, same as previously found for atomistic water models and models of other tetrahedral liquids. The low-pressure end of the LDM occurs near the pressure of maximum of the melting line, a feature that seems to be general to models that produce tetrahedrally coordinated crystals. We find that the mW water model qualitatively reproduces several key properties of real water: (i) the LDM is terminated by cavitation at low pressures and by crystallization of ice I{sub h} at high pressures, (ii) the LDM meets the crystallization line close to the crossover in crystallization from ice I{sub h} to a non-tetrahedral four-coordinated crystal, and (iii) the density of the liquid at the crossover in crystallization from ice I{sub h} to a four-coordinated non-tetrahedral crystal coincides with the locus of maximum in diffusivity as a function of pressure. The similarities in equilibrium and non-equilibrium phase behavior between the mW model and real water provide support to the quest to find a compressibility extremum, and determine whether it presents a maximum, in the doubly metastable region.« less

Relationship between the line of density anomaly and the lines of melting, crystallization, cavitation, and liquid spinodal in coarse-grained water models.

PubMed

Lu, Jibao; Chakravarty, Charusita; Molinero, Valeria

2016-06-21

Liquid water has several anomalous properties, including a non-monotonous dependence of density with temperature and an increase of thermodynamic response functions upon supercooling. Four thermodynamic scenarios have been proposed to explain the anomalies of water, but it is not yet possible to decide between them from experiments because of the crystallization and cavitation of metastable liquid water. Molecular simulations provide a versatile tool to study the anomalies and phase behavior of water, assess their agreement with the phenomenology of water under conditions accessible to experiments, and provide insight into the behavior of water in regions that are challenging to probe in the laboratory. Here we investigate the behavior of the computationally efficient monatomic water models mW and mTIP4P/2005(REM), with the aim of unraveling the relationships between the lines of density extrema in the p-T plane, and the lines of melting, liquid-vapor spinodal and non-equilibrium crystallization and cavitation. We focus particularly on the conditions for which the line of density maxima (LDM) in the liquid emerges and disappears as the pressure is increased. We find that these models present a retracing LDM, same as previously found for atomistic water models and models of other tetrahedral liquids. The low-pressure end of the LDM occurs near the pressure of maximum of the melting line, a feature that seems to be general to models that produce tetrahedrally coordinated crystals. We find that the mW water model qualitatively reproduces several key properties of real water: (i) the LDM is terminated by cavitation at low pressures and by crystallization of ice Ih at high pressures, (ii) the LDM meets the crystallization line close to the crossover in crystallization from ice Ih to a non-tetrahedral four-coordinated crystal, and (iii) the density of the liquid at the crossover in crystallization from ice Ih to a four-coordinated non-tetrahedral crystal coincides with the locus of maximum in diffusivity as a function of pressure. The similarities in equilibrium and non-equilibrium phase behavior between the mW model and real water provide support to the quest to find a compressibility extremum, and determine whether it presents a maximum, in the doubly metastable region.

Factorial analysis of trihalomethanes formation in drinking water.

PubMed

Chowdhury, Shakhawat; Champagne, Pascale; McLellan, P James

2010-06-01

Disinfection of drinking water reduces pathogenic infection, but may pose risks to human health through the formation of disinfection byproducts. The effects of different factors on the formation of trihalomethanes were investigated using a statistically designed experimental program, and a predictive model for trihalomethanes formation was developed. Synthetic water samples with different factor levels were produced, and trihalomethanes concentrations were measured. A replicated fractional factorial design with center points was performed, and significant factors were identified through statistical analysis. A second-order trihalomethanes formation model was developed from 92 experiments, and the statistical adequacy was assessed through appropriate diagnostics. This model was validated using additional data from the Drinking Water Surveillance Program database and was applied to the Smiths Falls water supply system in Ontario, Canada. The model predictions were correlated strongly to the measured trihalomethanes, with correlations of 0.95 and 0.91, respectively. The resulting model can assist in analyzing risk-cost tradeoffs in the design and operation of water supply systems.

Global modeling of land water and energy balances. Part II: Land-characteristic contributions to spatial variability

USGS Publications Warehouse

Milly, P.C.D.; Shmakin, A.B.

2002-01-01

Land water and energy balances vary around the globe because of variations in amount and temporal distribution of water and energy supplies and because of variations in land characteristics. The former control (water and energy supplies) explains much more variance in water and energy balances than the latter (land characteristics). A largely untested hypothesis underlying most global models of land water and energy balance is the assumption that parameter values based on estimated geographic distributions of soil and vegetation characteristics improve the performance of the models relative to the use of globally constant land parameters. This hypothesis is tested here through an evaluation of the improvement in performance of one land model associated with the introduction of geographic information on land characteristics. The capability of the model to reproduce annual runoff ratios of large river basins, with and without information on the global distribution of albedo, rooting depth, and stomatal resistance, is assessed. To allow a fair comparison, the model is calibrated in both cases by adjusting globally constant scale factors for snow-free albedo, non-water-stressed bulk stomatal resistance, and critical root density (which is used to determine effective root-zone depth). The test is made in stand-alone mode, that is, using prescribed radiative and atmospheric forcing. Model performance is evaluated by comparing modeled runoff ratios with observed runoff ratios for a set of basins where precipitation biases have been shown to be minimal. The withholding of information on global variations in these parameters leads to a significant degradation of the capability of the model to simulate the annual runoff ratio. An additional set of optimization experiments, in which the parameters are examined individually, reveals that the stomatal resistance is, by far, the parameter among these three whose spatial variations add the most predictive power to the model in stand-alone mode. Further single-parameter experiments with surface roughness length, available water capacity, thermal conductivity, and thermal diffusivity show very little sensitivity to estimated global variations in these parameters. Finally, it is found that even the constant-parameter model performance exceeds that of the Budyko and generalized Turc-Pike water-balance equations, suggesting that the model benefits also from information on the geographic variability of the temporal structure of forcing.

Structure of colloidosomes with tunable particle density: Simulation versus experiment

NASA Astrophysics Data System (ADS)

Fantoni, Riccardo; Salari, Johannes W. O.; Klumperman, Bert

2012-06-01

Colloidosomes are created in the laboratory from a Pickering emulsion of water droplets in oil. The colloidosomes have approximately the same diameter and by choosing (hairy) particles of different diameters it is possible to control the particle density on the droplets. The experiment is performed at room temperature. The radial distribution function of the assembly of (primary) particles on the water droplet is measured in the laboratory and in a computer experiment of a fluid model of particles with pairwise interactions on the surface of a sphere.

Mobility of multiwalled carbon nanotubes in porous media.

PubMed

Liu, Xueying; O'Carroll, Denis M; Petersen, Elijah J; Huang, Qingguo; Anderson, C Lindsay

2009-11-01

Engineered multiwalled carbon nanotubes (MWCNTs) are the subject of intense research and are expected to gain widespread usage in a broad variety of commercial products. However, concerns have been raised regarding potential environmental and human health risks. The mobility of MWCNTs in porous media is examined in this study using one-dimensional flow-through column experiments under conditions representative of subsurface and drinking water treatment systems. Results demonstrate that pore water velocity strongly influenced MWCNT transport, with high MWCNT mobility at pore water velocities greater than 4.0 m/d. A numerical simulator, which incorporated a newly developed theoretical collector efficiency relationship for MWCNTs in spherical porous media, was developed to model observed column results. The model, which incorporated traditional colloid filtration theory in conjunction with a site-blocking term, yielded good agreement with observed results in quartz sand-packed column experiments. Experiments were also conducted in glass bead-packed columns with the same mean grain size as the quartz sand-packed columns. MWCNTs were more mobile in the glass bead-packed columns.

Laboratory experiments to investigate sublimation rates of water ice in nighttime lunar regolith

NASA Astrophysics Data System (ADS)

Piquette, Marcus; Horányi, Mihály; Stern, S. Alan

2017-09-01

The existence of water ice on the lunar surface has been a long-standing topic with implications for both lunar science and in-situ resource utilization (ISRU). Cold traps on the lunar surface may have conditions necessary to retain water ice, but no laboratory experiments have been conducted to verify modeling results. We present an experiment testing the ability to thermally control bulk samples of lunar regolith simulant mixed with water ice under vacuum in an effort to constrain sublimation rates. The simulant used was JSC-1A lunar regolith simulant developed by NASA's Johnson Space Center. Samples with varying ratios of water ice and JSC-1A regolith simulant, totally about 1 kg, were placed under vacuum and cooled to 100 K to simulate conditions in lunar cold traps. The resulting sublimation of water ice over an approximately five-day period was measured by comparing the mass of the samples before and after the experimental run. Our results indicate that water ice in lunar cold traps is stable on timescales comparable to the lunar night, and should continue to be studied as possible resources for future utilization. This experiment also gauges the efficacy of the synthetic lunar atmosphere mission (SLAM) as a low-cost water resupply mission to lunar outposts.

Length-scale crossover of the hydrophobic interaction in a coarse-grained water model

NASA Astrophysics Data System (ADS)

Chaimovich, Aviel; Shell, M. Scott

2013-11-01

It has been difficult to establish a clear connection between the hydrophobic interaction among small molecules typically studied in molecular simulations (a weak, oscillatory force) and that found between large, macroscopic surfaces in experiments (a strong, monotonic force). Here, we show that both types of interaction can emerge with a simple, core-softened water model that captures water's unique pairwise structure. As in hydrophobic hydration, we find that the hydrophobic interaction manifests a length-scale dependence, exhibiting distinct driving forces in the molecular and macroscopic regimes. Moreover, the ability of this simple model to capture both regimes suggests that several features of the hydrophobic force can be understood merely through water's pair correlations.

Length-scale crossover of the hydrophobic interaction in a coarse-grained water model.

PubMed

Chaimovich, Aviel; Shell, M Scott

2013-11-01

It has been difficult to establish a clear connection between the hydrophobic interaction among small molecules typically studied in molecular simulations (a weak, oscillatory force) and that found between large, macroscopic surfaces in experiments (a strong, monotonic force). Here, we show that both types of interaction can emerge with a simple, core-softened water model that captures water's unique pairwise structure. As in hydrophobic hydration, we find that the hydrophobic interaction manifests a length-scale dependence, exhibiting distinct driving forces in the molecular and macroscopic regimes. Moreover, the ability of this simple model to capture both regimes suggests that several features of the hydrophobic force can be understood merely through water's pair correlations.

Martian rampart crater ejecta - Experiments and analysis of melt-water interaction

NASA Technical Reports Server (NTRS)

Wohletz, K. H.; Sheridan, M. F.

1983-01-01

The possible effects of explosive water vaporization on ejecta emplacement after impact into a wet target are described. A general model is formulated from analysis of Viking imagery of Mars and experimental vapor explosions as well as consideration of fluidized particulate transport and lobate volcanic deposits. The discussed model contends that as target water content increases, the effects of vapor expansion due to impact increasingly modify the ballistic flow field during crater excavation. This modification results in transport by gravity-driven surface flowage, and is similar to that of atmospheric drag effects on ejecta modelled by Schultz and Gault (1979).

A comparative study of behaviors of ventilated supercavities between experimental models with different mounting configurations

NASA Astrophysics Data System (ADS)

Lee, Seung-Jae; Kawakami, Ellison; Karn, Ashish; Arndt, Roger E. A.

2016-08-01

Small-scale water tunnel experiments of the phenomenon of supercavitation can be carried out broadly using two different kinds of experimental models-in the first model (forward facing model, or FFM), the incoming flow first interacts with the cavitator at front, which is connected to the strut through a ventilation pipe. The second model could have the strut and the ventilation pipe preceding the cavitator (backward facing model, or BFM). This is the continuation of a water tunnel study of the effects of unsteady flows on axisymmetric supercavities. In this study, the unwanted effect of test model configuration on supercavity shape in periodic flows was explored through a comparison of FFM and BFM models. In our experiments, it was found that periodic gust flows have only a minimal effect on the maximum diameter and the cavity length can be shortened above a certain vertical velocity of periodic flows. These findings appear to be robust regardless of the model configuration.

Three phase heat and mass transfer model for unsaturated soil freezing process: Part 2 - model validation

NASA Astrophysics Data System (ADS)

Zhang, Yaning; Xu, Fei; Li, Bingxi; Kim, Yong-Song; Zhao, Wenke; Xie, Gongnan; Fu, Zhongbin

2018-04-01

This study aims to validate the three-phase heat and mass transfer model developed in the first part (Three phase heat and mass transfer model for unsaturated soil freezing process: Part 1 - model development). Experimental results from studies and experiments were used for the validation. The results showed that the correlation coefficients for the simulated and experimental water contents at different soil depths were between 0.83 and 0.92. The correlation coefficients for the simulated and experimental liquid water contents at different soil temperatures were between 0.95 and 0.99. With these high accuracies, the developed model can be well used to predict the water contents at different soil depths and temperatures.

Multiphase flow modelling of volcanic ash particle settling in water using adaptive unstructured meshes

NASA Astrophysics Data System (ADS)

Jacobs, C. T.; Collins, G. S.; Piggott, M. D.; Kramer, S. C.; Wilson, C. R. G.

2013-02-01

Small-scale experiments of volcanic ash particle settling in water have demonstrated that ash particles can either settle slowly and individually, or rapidly and collectively as a gravitationally unstable ash-laden plume. This has important implications for the emplacement of tephra deposits on the seabed. Numerical modelling has the potential to extend the results of laboratory experiments to larger scales and explore the conditions under which plumes may form and persist, but many existing models are computationally restricted by the fixed mesh approaches that they employ. In contrast, this paper presents a new multiphase flow model that uses an adaptive unstructured mesh approach. As a simulation progresses, the mesh is optimized to focus numerical resolution in areas important to the dynamics and decrease it where it is not needed, thereby potentially reducing computational requirements. Model verification is performed using the method of manufactured solutions, which shows the correct solution convergence rates. Model validation and application considers 2-D simulations of plume formation in a water tank which replicate published laboratory experiments. The numerically predicted settling velocities for both individual particles and plumes, as well as instability behaviour, agree well with experimental data and observations. Plume settling is clearly hindered by the presence of a salinity gradient, and its influence must therefore be taken into account when considering particles in bodies of saline water. Furthermore, individual particles settle in the laminar flow regime while plume settling is shown (by plume Reynolds numbers greater than unity) to be in the turbulent flow regime, which has a significant impact on entrainment and settling rates. Mesh adaptivity maintains solution accuracy while providing a substantial reduction in computational requirements when compared to the same simulation performed using a fixed mesh, highlighting the benefits of an adaptive unstructured mesh approach.

Chord length distributions interpretation using a polydispersed population: Modeling and experiments

NASA Astrophysics Data System (ADS)

Cameirao, A.; Le Ba, H.; Darbouret, M.; Herri, J.-M.; Peytavy, J.-L.; Glénat, P.

2012-03-01

Chord length distributions were measured during the crystallization of gas hydrates in a flow loop. The conditions on the flow loop were similar with the conditions in the marine pipelines. The flow loop was filled with water in oil emulsion and pressurized with methane (7 MPa) at low temperature (277 K). During crystallization water droplets crystallize and agglomerate. The CLD measures were interpreted in a preceding work [Le Ba et al., 2010] [1] by constructing random aggregates with known geometrical proprieties from a monodispersed population of droplets and calculating their CLD. Comparing calculated CLD with CLD from the experiment, the geometrical parameters: number of primary particles and fractal dimension of experimental aggregates are identified. However some differences remained between the experiment and the calculated CLD. In the present work the droplets population was considered polydispersed improving the comparison between the model and the experiment.

Optimization of permeability for quality improvement by using factorial design

NASA Astrophysics Data System (ADS)

Said, Rahaini Mohd; Miswan, Nor Hamizah; Juan, Ng Shu; Hussin, Nor Hafizah; Ahmad, Aminah; Kamal, Mohamad Ridzuan Mohamad

2017-05-01

Sand castings are used worldwide by the manufacturing process in Metal Casting Industry, whereby the green sand are the commonly used sand mould type in the industry of sand casting. The defects on the surface of casting product is one of the problems in the industry of sand casting. The problems that relates to the defect composition of green sand are such as blowholes, pinholes shrinkage and porosity. Our objective is to optimize the best composition of green sand in order to minimize the occurrence of defects. Sand specimen of difference parameters (Bentonite, Green Sand, Cold dust and water) were design and prepared to undergo permeability test. The 24 factorial design experiment with four factors at difference composition were runs, and the total of 16 runs experiment were conducted. The developed models based on the experimental design necessary models were obtained. The model with a high coefficient of determination (R2=0.9841) and model for predicted and actual fitted well with the experimental data. Using the Analysis of Design Expert software, we identified that bentonite and water are the main interaction effect in the experiments. The optimal settings for green sand composition are 100g silica sand, 21g bentonite, 6.5 g water and 6g coal dust. This composition gives an effect of permeability number 598.3GP.

Solute and heat transport model of the Henry and Hilleke laboratory experiment

USGS Publications Warehouse

Langevin, C.D.; Dausman, A.M.; Sukop, M.C.

2010-01-01

SEAWAT is a coupled version of MODFLOW and MT3DMS designed to simulate variable-density ground water flow and solute transport. The most recent version of SEAWAT, called SEAWAT Version 4, includes new capabilities to represent simultaneous multispecies solute and heat transport. To test the new features in SEAWAT, the laboratory experiment of Henry and Hilleke (1972) was simulated. Henry and Hilleke used warm fresh water to recharge a large sand-filled glass tank. A cold salt water boundary was represented on one side. Adjustable heating pads were used to heat the bottom and left sides of the tank. In the laboratory experiment, Henry and Hilleke observed both salt water and fresh water flow systems separated by a narrow transition zone. After minor tuning of several input parameters with a parameter estimation program, results from the SEAWAT simulation show good agreement with the experiment. SEAWAT results suggest that heat loss to the room was more than expected by Henry and Hilleke, and that multiple thermal convection cells are the likely cause of the widened transition zone near the hot end of the tank. Other computer programs with similar capabilities may benefit from benchmark testing with the Henry and Hilleke laboratory experiment. Journal Compilation ?? 2009 National Ground Water Association.

Simulation and experimental research on trans-media vehicle water-entry motion characteristics at low speed

PubMed Central

Yang, Jian; Feng, Jinfu; Hu, Junhua; Liu, An

2017-01-01

The motion characteristics of trans-media vehicles during the water-entry process were explored in this study in an effort to obtain the optimal water-entry condition of the vehicle for developing a novel, single control strategy integrating underwater non-control and in-air control. A water-entry dynamics model is established by combining the water-entry motion characteristics of the vehicle in uncontrolled conditions at low speed with time-varying parameters (e.g. buoyancy, added mass). A water-entry experiment is designed to confirm the effectiveness of the established model. After that, by comparing the experimental results with the simulated results, the model is further modified to more accurately reflect water-entry motion. The change laws of the vehicle’s attitude and position during the water-entry process are also obtained by analyzing the simulation of the modified model under different velocity, angle, and angle of attack conditions. The results presented here have guiding significance for the future realization of reaching the stable underwater navigation state of the vehicle after water-entry process. PMID:28558012

Simulation and experimental research on trans-media vehicle water-entry motion characteristics at low speed.

PubMed

Yang, Jian; Li, Yongli; Feng, Jinfu; Hu, Junhua; Liu, An

2017-01-01

The motion characteristics of trans-media vehicles during the water-entry process were explored in this study in an effort to obtain the optimal water-entry condition of the vehicle for developing a novel, single control strategy integrating underwater non-control and in-air control. A water-entry dynamics model is established by combining the water-entry motion characteristics of the vehicle in uncontrolled conditions at low speed with time-varying parameters (e.g. buoyancy, added mass). A water-entry experiment is designed to confirm the effectiveness of the established model. After that, by comparing the experimental results with the simulated results, the model is further modified to more accurately reflect water-entry motion. The change laws of the vehicle's attitude and position during the water-entry process are also obtained by analyzing the simulation of the modified model under different velocity, angle, and angle of attack conditions. The results presented here have guiding significance for the future realization of reaching the stable underwater navigation state of the vehicle after water-entry process.

Evaluating GCM land surface hydrology parameterizations by computing river discharges using a runoff routing model: Application to the Mississippi basin

NASA Technical Reports Server (NTRS)

Liston, G. E.; Sud, Y. C.; Wood, E. F.

1994-01-01

To relate general circulation model (GCM) hydrologic output to readily available river hydrographic data, a runoff routing scheme that routes gridded runoffs through regional- or continental-scale river drainage basins is developed. By following the basin overland flow paths, the routing model generates river discharge hydrographs that can be compared to observed river discharges, thus allowing an analysis of the GCM representation of monthly, seasonal, and annual water balances over large regions. The runoff routing model consists of two linear reservoirs, a surface reservoir and a groundwater reservoir, which store and transport water. The water transport mechanisms operating within these two reservoirs are differentiated by their time scales; the groundwater reservoir transports water much more slowly than the surface reservior. The groundwater reservior feeds the corresponding surface store, and the surface stores are connected via the river network. The routing model is implemented over the Global Energy and Water Cycle Experiment (GEWEX) Continental-Scale International Project Mississippi River basin on a rectangular grid of 2 deg X 2.5 deg. Two land surface hydrology parameterizations provide the gridded runoff data required to run the runoff routing scheme: the variable infiltration capacity model, and the soil moisture component of the simple biosphere model. These parameterizations are driven with 4 deg X 5 deg gridded climatological potential evapotranspiration and 1979 First Global Atmospheric Research Program (GARP) Global Experiment precipitation. These investigations have quantified the importance of physically realistic soil moisture holding capacities, evaporation parameters, and runoff mechanisms in land surface hydrology formulations.

Dynamics of Water Absorption and Evaporation During Methanol Droplet Combustion in Microgravity

NASA Technical Reports Server (NTRS)

Hicks, Michael C.; Dietrich, Daniel L.; Nayagam, Vedha; Williams, Forman A.

2012-01-01

The combustion of methanol droplets is profoundly influenced by the absorption and evaporation of water, generated in the gas phase as a part of the combustion products. Initially there is a water-absorption period of combustion during which the latent heat of condensation of water vapor, released into the droplet, enhances its burning rate, whereas later there is a water-evaporation period, during which the water vapor reduces the flame temperature suffciently to extinguish the flame. Recent methanol droplet-combustion experiments in ambient environments diluted with carbon dioxide, conducted in the Combustion Integrated Rack on the International Space Station (ISS), as a part of the FLEX project, provided a method to delineate the water-absorption period from the water-evaporation period using video images of flame intensity. These were obtained using an ultra-violet camera that captures the OH* radical emission at 310 nm wavelength and a color camera that captures visible flame emission. These results are compared with results of ground-based tests in the Zero Gravity Facility at the NASA Glenn Research Center which employed smaller droplets in argon-diluted environments. A simplified theoretical model developed earlier correlates the transition time at which water absorption ends and evaporation starts. The model results are shown to agree reasonably well with experiment.

ELF and ALEX SURF WINTER WAVES: Lidar Intercomparison of Aerosol and Water Vapor Measurements in the Baltimore-Washington Metropolitan Area During the Winter Water Vapor Validation Experiments (WAVES) 2008 campaign.

NASA Astrophysics Data System (ADS)

Delgado, R.; Weldegaber, M.; Wilson, R. C.; McMillan, W.; McCann, K. J.; Woodman, M.; Demoz, B.; Adam, M.; Connell, R.; Venable, D.; Joseph, E.; Rabenhorst, S.; Twigg, L.; McGee, T.; Whiteman, D. N.; Hoff, R. M.

2008-12-01

Elastic and Raman lidar measurements were conducted to measure the vertical distribution of aerosols and water vapor during the Water Vapor Validation Experiments (WAVES) 2008 campaign by the University of Maryland Baltimore County (UMBC) Atmospheric Lidar Group at UMBC, at the same time as measurements at Howard University's Beltsville Research Station (26.5 km distant). The lidar profiles of atmospheric water vapor and aerosols allowed comparison for AURA/Aqua retrieval studies, by performing instrument accuracy assessments and data, generated by various independent active and passive remote sensing instruments for case studies of regional water vapor and aerosol sub-pixel variability. Integration of the lidar water vapor mixing ratios has been carried out to generate a column precipitable water vapor timeseries that can be compared to UMBC's SUOMINET station and Baltimore Bomem Atmospheric Emitted Radiance Interferometer (BBAERI). Changes in atmospheric aerosol concentration and water vapor mixing ratios due to meteorological events observed in the lidar timeseries have been correlated to the vertical temperature timeseries of BBAERI and to modeling of the air mass over the Baltimore-Washington metro area with the Weather Research and Forecasting (WRF) model.

Linking Water Pathways and Sources of Dissolved Organic Matter at the Hillslope Scale: A 24-Day Sprinkling Experiment

NASA Astrophysics Data System (ADS)

van Verseveld, W. J.; Graham, C. B.; Barnard, H. R.; McDonnell, J. J.; Lajtha, K.; Brooks, R. J.; Bond, B. J.

2006-12-01

The link between water flow paths, dissolved organic matter (DOM) sources and DOM production is poorly understood. The few investigations that have explored such relations in forest systems have relied passively on natural rainfall and drainage events. As a result, it has been difficult to identify the first order controls on water- biogeochemical processes. While we often assume an unlimited supply of DOM in our hydro-biogeochemical models, few studies have explicitly tested this. This work reports on a 24-day sprinkler experiment in Watershed-10 at the H.J. Andrews Experimental Forest in Oregon, USA. Our research objectives were: (1) To quantify the labile DOM pool in the upper soil layers at the hillslope scale, (2) To resolve the dominant flowpath at the hillslope scale that flush DOM from the soil profile to the stream channel, and (3) quantify the mixing between sprinkler water and hillslope subsurface flux. We injected 0,8 L of 100% deuterium into the sprinkler water for 24 hours and sampled soil and groundwater at daily to 2 days intervals throughout the 24 day experiment. We extracted 10 soil samples each week from the test hillslope and an adjacent similar reference plot and incubated them to quantify potential N mineralization and supply of organic carbon and nitrogen. Preliminary results suggested that DOM was transport-limited during the sprinkler experiment. Shallow lateral flow through the unsaturated zone; at 30 cm depth was very likely the dominant DOM pathway to the stream for the first two days (and 95 mm of sprinkled water) of the sprinkler experiment. After more than 4 days (and 395 mm of sprinkled water), saturation occurred at 100 cm, and deeper flowpaths became activated. These results challenge many of the assumptions in hydro-biogeochemical models where an unlimited supply of DOM is usually assumed.

Skylab fluid mechanics simulations: Oscillation, rotation, collision and coalescence of water droplets under low-gravity environment

NASA Technical Reports Server (NTRS)

Vaughan, O. H., Jr.; Hung, R. J.

1975-01-01

Skylab 4 crew members performed a series of demonstrations showing the oscillations, rotations, as well as collision coalescence of water droplets which simulate various physical models of fluids under low gravity environment. The results from Skylab demonstrations provide information and illustrate the potential of an orbiting space-oriented research laboratory for the study of more sophisticated fluid mechanic experiments. Experiments and results are discussed.

Adopting adequate leaching requirement for practical response models of basil to salinity

NASA Astrophysics Data System (ADS)

Babazadeh, Hossein; Tabrizi, Mahdi Sarai; Darvishi, Hossein Hassanpour

2016-07-01

Several mathematical models are being used for assessing plant response to salinity of the root zone. Objectives of this study included quantifying the yield salinity threshold value of basil plants to irrigation water salinity and investigating the possibilities of using irrigation water salinity instead of saturated extract salinity in the available mathematical models for estimating yield. To achieve the above objectives, an extensive greenhouse experiment was conducted with 13 irrigation water salinity levels, namely 1.175 dS m-1 (control treatment) and 1.8 to 10 dS m-1. The result indicated that, among these models, the modified discount model (one of the most famous root water uptake model which is based on statistics) produced more accurate results in simulating the basil yield reduction function using irrigation water salinities. Overall the statistical model of Steppuhn et al. on the modified discount model and the math-empirical model of van Genuchten and Hoffman provided the best results. In general, all of the statistical models produced very similar results and their results were better than math-empirical models. It was also concluded that if enough leaching was present, there was no significant difference between the soil salinity saturated extract models and the models using irrigation water salinity.

Representing Plant Hydraulics in a Global Model: Updates to the Community Land Model

NASA Astrophysics Data System (ADS)

Kennedy, D.; Swenson, S. C.; Oleson, K. W.; Lawrence, D. M.; Fisher, R.; Gentine, P.

2017-12-01

In previous versions, the Community Land Model has used soil moisture to stand in for plant water status, with transpiration and photosynthesis driven directly by soil water potential. This eschews significant literature demonstrating the importance of plant hydraulic traits in the dynamics of water flow through the soil-plant-atmosphere continuum and in the regulation of stomatal aperture. In this study we install a simplified hydraulic framework to represent vegetation water potential and to regulate root water uptake and turbulent fluxes. Plant hydraulics allow for a more explicit representation of plant water status, which improves the physical basis for many processes represented in CLM. This includes root water uptake and the attenuation of photosynthesis and transpiration with drought. Model description is accompanied by results from a point simulation based at the Caxiuanã flux tower site in Eastern Amazonia, covering a throughfall exclusion experiment from 2001-2003. Including plant hydraulics improves the response to drought forcing compared to previous versions of CLM. Parameter sensitivity is examined at the same site and presented in the context of estimating hydraulic parameters in a global model.

Kinetic Release of Alkalinity from Particle-Containing Oil-in-Water Emulsions

NASA Astrophysics Data System (ADS)

Muller, K.; Chapra, S. C.; Ramsburg, A.

2014-12-01

Oil-in-water emulsions are typically employed during remediation to promote biotic reduction of contaminants. Emulsions, however, hold promise for encapsulated delivery of many types of active ingredients required for successful site remediation or long-term site stewardship. Our research is currently focused on using alkalinity-containing particles held within oil-in-water emulsions to sustain control of subsurface pH. Here we describe results from laboratory experiments and mathematical modeling conducted to quantify the kinetics associated with the emulsion delivery and alkalinity release process. Kinetically stable oil-in-water emulsions containing (~60 nmCaCO3 or ~100 nm MgO particles) were previously developed using soybean oil and Gum Arabic as a stabilizing agent. Batch and column experiments were employed to assess the accessibility and release of the alkalinity from the emulsion. Successive additions of HCl were used in batch systems to produce several pH responses (pH rebounds) that were subsequently modeled to elucidate release mechanisms and rates for varying emulsion compositions and particle types. Initial results suggest that a linear-driving-force model is generally able to capture the release behavior in the batch system when the temporally-constant, lumped mass-transfer coefficient is scaled by the fraction of particle mass remaining within the droplets. This result suggests that the rate limiting step in the release process may be the interphase transfer of reactive species at the oil-water interface. 1-d column experiments were also completed in order to quantify the extent and rate of alkalinity release from emulsion droplets retained in a sandy medium. Alkalinity release from the retained droplets treated a pH 4 influent water for 25-60 pore volumes (the duration depended on particle type and mass loading), and the cessation in treatment corresponded to exhaustion of the particle mass held within the oil. Column experiments were simulated using a transport code containing the linear-driving-force expression evaluated in the batch experiments. In these simulations the lumped mass transfer coefficient was fit and compared with values predicted using existing correlations for liquid-liquid and solid-liquid interfaces in porous media.

Diminished mercury emission from waters with duckweed cover

NASA Astrophysics Data System (ADS)

Wollenberg, Jennifer L.; Peters, Stephen C.

2009-06-01

Duckweeds (Lemnaceae) are a widely distributed type of floating vegetation in freshwater systems. Under suitable conditions, duckweeds form a dense vegetative mat on the water surface, which reduces light penetration into the water column and limits gas exchange at the water-air interface by decreasing the area of open water surface. Experiments were conducted to determine whether duckweed decreases mercury emission by limiting gas diffusion across the water-air interface and attenuating light, or, conversely, enhances emission via transpiration of mercury vapor. Microcosm flux chamber experiments indicate that duckweed decreases mercury emission from the water surface compared to open water controls. Fluxes under duckweed were 17-67% lower than in controls, with lower fluxes occurring at higher percent cover. The decrease in mercury emission suggests that duckweed may limit emission through one of several mechanisms, including limited gas transport across the air-water interface, decreased photoreactions due to light attenuation, and plant-mercury interactions. The results of this experiment were applied to a model lake system to illustrate the magnitude of potential effects on mercury cycling. The mercury retained in the lake as a result of hindered emission may increase bioaccumulation potential in lakes with duckweed cover.

Numerical analysis of the primary processes controlling oxygen dynamics on the Louisiana Shelf

NASA Astrophysics Data System (ADS)

Yu, L.; Fennel, K.; Laurent, A.; Murrell, M. C.; Lehrter, J. C.

2014-10-01

The Louisiana shelf in the northern Gulf of Mexico receives large amounts of freshwater and nutrients from the Mississippi/Atchafalaya River system. These river inputs contribute to widespread bottom-water hypoxia every summer. In this study, we use a physical-biogeochemical model that explicitly simulates oxygen sources and sinks on the Louisiana shelf to identify the key mechanisms controlling hypoxia development. First, we validate the model simulation against observed dissolved oxygen concentrations, primary production, water column respiration, and sediment oxygen consumption. In the model simulation, heterotrophy is prevalent in shelf waters throughout the year except near the mouths of the Mississippi and Atchafalaya Rivers where primary production exceeds respiratory oxygen consumption during June and July. During this time, efflux of oxygen to the atmosphere, driven by photosynthesis and surface warming, becomes a significant oxygen sink while the well-developed pycnocline isolates autotrophic surface waters from the heterotrophic and hypoxic waters below. A substantial fraction of primary production occurs below the pycnocline in summer. We investigate whether this primary production below the pycnocline is mitigating the development of hypoxic conditions with the help of a sensitivity experiment where we disable biological processes in the water column (i.e. primary production and water column respiration). In this experiment below-pycnocline primary production reduces the spatial extent of hypoxic bottom waters only slightly. Our results suggest that the combination of physical processes and sediment oxygen consumption largely determine the spatial extent and dynamics of hypoxia on the Louisiana shelf.

Linear shoaling of free-surface waves in multi-layer non-hydrostatic models

NASA Astrophysics Data System (ADS)

Bai, Yefei; Cheung, Kwok Fai

2018-01-01

The capability to describe shoaling over sloping bottom is fundamental to modeling of coastal wave transformation. The linear shoaling gradient provides a metric to measure this property in non-hydrostatic models with layer-integrated formulations. The governing equations in Boussinesq form facilitate derivation of the linear shoaling gradient, which is in the form of a [ 2 P + 2 , 2 P ] expansion of the water depth parameter kd with P equal to 1 for a one-layer model and (4 N - 4) for an N-layer model. The expansion reproduces the analytical solution from Airy wave theory at the shallow water limit and maintains a reasonable approximation up to kd = 1.2 and 2 for the one and two-layer models. Additional layers provide rapid and monotonic convergence of the shoaling gradient into deep water. Numerical experiments of wave propagation over a plane slope illustrate manifestation of the shoaling errors through the transformation processes from deep to shallow water. Even though outside the zone of active wave transformation, shoaling errors from deep to intermediate water are cumulative to produce appreciable impact to the wave amplitude in shallow water.

Airborne Lidar Bathymetry Beam Diagnostics Using an Underwater Optical Detector Array

NASA Astrophysics Data System (ADS)

Birkebak, Matthew

The surface geometry of air-water interface is considered as an important factor affecting the performance of Airborne Lidar Bathymetry (ALB), and laser optical communication through the water surface. ALB is a remote sensing technique that utilizes a pulsed green (532 nm) laser mounted to an airborne platform in order to measure water depth. The water surface (i.e., air-water interface) can distort the light beam's ray-path geometry and add uncertainty to range calculation measurements. Previous studies on light refracting through a complex water surface are heavily dependent on theoretical models and simulations. In addition, only very limited work has been conducted to validate these theoretical models using experiments under well-controlled laboratory conditions. The goal of the study is to establish a clear relationship between water-surface conditions and the uncertainty of ALB measurement. This relationship will be determined by conducting more extensive empirical measurements to characterize the changes in beam slant path associated with a variety of short wavelength wind ripples, typically seen in ALB survey conditions. This study will focus on the effects of capillary and gravity-capillary waves with surface wavelengths smaller than the diameter of the laser beam on the water surface. Simulations using Monte-Carlo techniques of the ALB beam footprints and the environmental conditions were used to analyze the ray-path geometries. Based on the simulation results, laboratory experiments were then designed to test key parameters that have the greatest contribution on beam path and direction through the water. The laser beam dispersion experiments were conducted in well-controlled laboratory setting at the University of New Hampshire's Wave and Tow tank. The spatial elevations of the water surface were independently measured using a high resolution wave staff. The refracted laser beam footprint was measured using an underwater optical detector consisting of a 6x6 array of photodiodes. Image processing techniques were used to estimate the laser's incidence angle intercepted by the detector array. Beam patterns that resulted from intersection between the laser beam light field underwater and the detector array were modeled and used to calculate changes in position and orientation for water surface conditions containing wavelengths less than 0.1m. Finally, a total horizontal uncertainty (THU) model was estimated, which can be implemented in total propagated uncertainty (TPU) models for reporting as a measure of the quality of each measurement. The wave refraction error for various sea states and beam characteristics was successfully quantified using both experimental and analytical techniques.

Destruction of Energetic Materials in Supercritical Water

DTIC Science & Technology

2002-06-25

PHASE BEHAVIOR UNDER HYDROTHERMAL PROCESSING CONDITIONS...172 E. MODELING TOOLS FOR SOLVATION FREE ENERGIES IN HYDROTHERMAL SYSTEMS...potential equations of state of hydrothermal solutions. Figure 25 shows a schematic of the transient grating experiment. In this experiment, two laser

Basin Scale Estimates of Evapotranspiration Using GRACE and other Observations

NASA Technical Reports Server (NTRS)

Rodell, M.; Famiglietti, J. S.; Chen, J.; Seneviratne, S. I.; Viterbo, P.; Holl, S.; Wilson, C. R.

2004-01-01

Evapotranspiration is integral to studies of the Earth system, yet it is difficult to measure on regional scales. One estimation technique is a terrestrial water budget, i.e., total precipitation minus the sum of evapotranspiration and net runoff equals the change in water storage. Gravity Recovery and Climate Experiment (GRACE) satellite gravity observations are now enabling closure of this equation by providing the terrestrial water storage change. Equations are presented here for estimating evapotranspiration using observation based information, taking into account the unique nature of GRACE observations. GRACE water storage changes are first substantiated by comparing with results from a land surface model and a combined atmospheric-terrestrial water budget approach. Evapotranspiration is then estimated for 14 time periods over the Mississippi River basin and compared with output from three modeling systems. The GRACE estimates generally lay in the middle of the models and may provide skill in evaluating modeled evapotranspiration.

Marrying Hydrological Modelling and Integrated Assessment for the needs of Water Resource Management

NASA Astrophysics Data System (ADS)

Croke, B. F. W.; Blakers, R. S.; El Sawah, S.; Fu, B.; Guillaume, J. H. A.; Kelly, R. A.; Patrick, M. J.; Ross, A.; Ticehurst, J.; Barthel, R.; Jakeman, A. J.

2014-09-01

This paper discusses the integration of hydrology with other disciplines using an Integrated Assessment (IA) and modelling approach to the management and allocation of water resources. Recent developments in the field of socio-hydrology aim to develop stronger relationships between hydrology and the human dimensions of Water Resource Management (WRM). This should build on an existing wealth of knowledge and experience of coupled human-water systems. To further strengthen this relationship and contribute to this broad body of knowledge, we propose a strong and durable "marriage" between IA and hydrology. The foundation of this marriage requires engagement with appropriate concepts, model structures, scales of analyses, performance evaluation and communication - and the associated tools and models that are needed for pragmatic deployment or operation. To gain insight into how this can be achieved, an IA case study in water allocation in the Lower Namoi catchment, NSW, Australia is presented.

Integrating watershed hydrology and economics to establish a local market for water quality improvement: A field experiment.

PubMed

Uchida, Emi; Swallow, Stephen K; Gold, Arthur; Opaluch, James; Kafle, Achyut; Merrill, Nathaniel; Michaud, Clayton; Gill, Carrie Anne

2018-04-01

Innovative market mechanisms are being increasingly recognized as effective decision-making institutions to incorporate the value of ecosystem services into the economy. We present a field experiment that integrates an economic auction and a biophysical water flux model to develop a local market process consisting of both the supply and demand sides. On the supply side, we operate an auction with small-scale livestock owners who bid for contracts to implement site-specific manure management practices that reduce phosphorus loadings to a major reservoir. On the demand side, we implement a real money, multi-unit public good auction for these contracts with residents who potentially benefit from reduced water quality risks. The experiments allow us to construct supply and demand curves to find an equilibrium price for water quality improvement. The field experiments provide a proof-of-concept for practical implementation of a local market for environmental improvements, even for the challenging context of nonpoint pollution.

A Water Temperature Simulation Model for Rice Paddies With Variable Water Depths

NASA Astrophysics Data System (ADS)

Maruyama, Atsushi; Nemoto, Manabu; Hamasaki, Takahiro; Ishida, Sachinobu; Kuwagata, Tsuneo

2017-12-01

A water temperature simulation model was developed to estimate the effects of water management on the thermal environment in rice paddies. The model was based on two energy balance equations: for the ground and for the vegetation, and considered the water layer and changes in the aerodynamic properties of its surface with water depth. The model was examined with field experiments for water depths of 0 mm (drained conditions) and 100 mm (flooded condition) at two locations. Daily mean water temperatures in the flooded condition were mostly higher than in the drained condition in both locations, and the maximum difference reached 2.6°C. This difference was mainly caused by the difference in surface roughness of the ground. Heat exchange by free convection played an important role in determining water temperature. From the model simulation, the temperature difference between drained and flooded conditions was more apparent under low air temperature and small leaf area index conditions; the maximum difference reached 3°C. Most of this difference occurred when the range of water depth was lower than 50 mm. The season-long variation in modeled water temperature showed good agreement with an observation data set from rice paddies with various rice-growing seasons, for a diverse range of water depths (root mean square error of 0.8-1.0°C). The proposed model can estimate water temperature for a given water depth, irrigation, and drainage conditions, which will improve our understanding of the effect of water management on plant growth and greenhouse gas emissions through the thermal environment of rice paddies.

Impact of Plumbing Age on Copper Levels in Drinking Water

EPA Science Inventory

Theory and limited practical experiences suggest that higher copper levels in drinking water tap samples are typically associated with newer plumbing systems, and levels decrease with increasing plumbing age. Past researchers have developed a conceptual model to explain the “agin...

Physics Parameterization for Seasonal Prediction

DTIC Science & Technology

2012-09-30

comparison Project, a joint effort between the Year of Tropical Convection (YOTC) Program and the Global Energy and Water Cycle Experiment (GEWEX) Cloud...unified” representation of the water cycle in the model. One such area is the correspondence between diagnosed cloud cover and prognostic cloud

How Accurately Do Maize Crop Models Simulate the Interactions of Atmospheric CO2 Concentration Levels With Limited Water Supply on Water Use and Yield?

NASA Technical Reports Server (NTRS)

Durand, Jean-Louis; Delusca, Kenel; Boote, Ken; Lizaso, Jon; Manderscheid, Remy; Weigel, Hans Johachim; Ruane, Alexander Clark; Rosenzweig, Cynthia E.; Jones, Jim; Ahuja, Laj;

Visualizing landscape hydrology as a means of education - The water cycle in a box

NASA Astrophysics Data System (ADS)

Lehr, Christian; Rauneker, Philipp; Fahle, Marcus; Hohenbrink, Tobias; Böttcher, Steven; Natkhin, Marco; Thomas, Björn; Dannowski, Ralf; Schwien, Bernd; Lischeid, Gunnar

2016-04-01

We used an aquarium to construct a physical model of the water cycle. The model can be used to visualize the movement of the water through the landscape from precipitation and infiltration via surface and subsurface flow to discharge into the sea. The model consists of two aquifers that are divided by a loamy aquitard. The 'geological' setting enables us to establish confining groundwater conditions and to demonstrate the functioning of artesian wells. Furthermore, small experiments with colored water as tracer can be performed to identify flow paths below the ground, simulate water supply problems like pollution of drinking water wells from inflowing contaminated groundwater or changes in subsurface flow direction due to changes in the predominant pressure gradients. Hydrological basics such as the connectivity of streams, lakes and the surrounding groundwater or the dependency of groundwater flow velocity from different substrates can directly be visualized. We used the model as an instructive tool in education and for public relations. We presented the model to different audiences from primary school pupils to laymen, students of hydrology up to university professors. The model was presented to the scientific community as part of the "Face of the Earth" exhibition at the EGU general assembly 2014. Independent of the antecedent knowledge of the audience, the predominant reactions were very positive. The model often acted as icebreaker to get a conversation on hydrological topics started. Because of the great interest, we prepared video material and a photo documentation on 1) the construction of the model and 2) the visualization of steady and dynamic hydrological situations. The videos will be published soon under creative common license and the collected material will be made accessible online. Accompanying documents will address professionals in hydrology as well as non-experts. In the PICO session, we will present details about the construction of the model and its main features. Further, short videos of specific processes and experiments will be shown.

Case study of the effectiveness of passive grease trap for management on domestic kitchen waste water

NASA Astrophysics Data System (ADS)

Nidzamuddin, M. Y.; Juffrizal, K.; Mustapha, F.; Zulfattah, Z. M.; Tan, C. F.; Taha, M. M.; Hidayah, I.; Hilwa, M. Z.

2015-05-01

Household waste, generally known as trash or garbage is mostly includes food wastes, product packaging, and other miscellaneous inorganic wastes that are coming from domestic household. Grease waste such as oil and fats can contaminate water and also clot on pipes provoking blockages. Thus, waste water from kitchen sink need a proper way of filtration. Grease trap developed in this paper is viable in trapping the grease residue. The experiments have been conducted in controlled environment and the objectives are to investigate the effectiveness of grease trap by proving the existence of retention time and the expected ratio of collected water and oil during experiment process using a prototype model.

Development and validation of a two-dimensional fast-response flood estimation model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Judi, David R; Mcpherson, Timothy N; Burian, Steven J

2009-01-01

A finite difference formulation of the shallow water equations using an upwind differencing method was developed maintaining computational efficiency and accuracy such that it can be used as a fast-response flood estimation tool. The model was validated using both laboratory controlled experiments and an actual dam breach. Through the laboratory experiments, the model was shown to give good estimations of depth and velocity when compared to the measured data, as well as when compared to a more complex two-dimensional model. Additionally, the model was compared to high water mark data obtained from the failure of the Taum Sauk dam. Themore » simulated inundation extent agreed well with the observed extent, with the most notable differences resulting from the inability to model sediment transport. The results of these validation studies complex two-dimensional model. Additionally, the model was compared to high water mark data obtained from the failure of the Taum Sauk dam. The simulated inundation extent agreed well with the observed extent, with the most notable differences resulting from the inability to model sediment transport. The results of these validation studies show that a relatively numerical scheme used to solve the complete shallow water equations can be used to accurately estimate flood inundation. Future work will focus on further reducing the computation time needed to provide flood inundation estimates for fast-response analyses. This will be accomplished through the efficient use of multi-core, multi-processor computers coupled with an efficient domain-tracking algorithm, as well as an understanding of the impacts of grid resolution on model results.« less

Impacts of historic and projected land-cover, land-use, and land-management change on carbon and water fluxes: The Land Use Model Intercomparison Project (LUMIP)

NASA Astrophysics Data System (ADS)

Lawrence, D. M.; Lombardozzi, D. L.; Lawrence, P.; Hurtt, G. C.

2017-12-01

Human land-use activities have resulted in large changes to the Earth surface, with resulting implications for climate. In the future, land-use activities are likely to intensify to meet growing demands for food, fiber, and energy. The Land Use Model Intercomparison Project (LUMIP) aims to further advance understanding of the broad question of impacts of land-use and land-cover change (LULCC) as well as more detailed science questions to get at process-level attribution, uncertainty, and data requirements in more depth and sophistication than possible in a multi-model context to date. LUMIP is multi-faceted and aims to advance our understanding of land-use change from several perspectives. In particular, LUMIP includes a factorial set of land-only simulations that differ from each other with respect to the specific treatment of land use or land management (e.g., irrigation active or not, crop fertilization active or not, wood harvest on or not), or in terms of prescribed climate. This factorial series of experiments serves several purposes and is designed to provide a detailed assessment of how the specification of land-cover change and land management affects the carbon, water, and energy cycle response to land-use change. The potential analyses that are possible through this set of experiments are vast. For example, comparing a control experiment with all land management active to an experiment with no irrigation allows a multi-model assessment of whether or not the increasing use of irrigation during the 20th century is likely to have significantly altered trends of regional water and energy fluxes (and therefore climate) and/or crop yield and carbon fluxes in agricultural regions. Here, we will present preliminary results from the factorial set of experiments utilizing the Community Land Model (CLM5). The analyses presented here will help guide multi-model analyses once the full set of LUMIP simulations are available.

Modelling the Mont Terri HE-D experiment for the Thermal–Hydraulic–Mechanical response of a bedded argillaceous formation to heating

DOE PAGES

Garitte, B.; Nguyen, T. S.; Barnichon, J. D.; ...

2017-05-09

Coupled thermal–hydrological–mechanical (THM) processes in the near field of deep geological repositories can influence several safety features of the engineered and geological barriers. Among those features are: the possibility of damage in the host rock, the time for re-saturation of the bentonite, and the perturbations in the hydraulic regime in both the rock and engineered seals. Within the international cooperative code-validation project DECOVALEX-2015, eight research teams developed models to simulate an in situ heater experiment, called HE-D, in Opalinus Clay at the Mont Terri Underground Research Laboratory in Switzerland. The models were developed from the theory of poroelasticity in ordermore » to simulate the coupled THM processes that prevailed during the experiment and thereby to characterize the in situ THM properties of Opalinus Clay. The modelling results for the evolution of temperature, pore water pressure, and deformation at different points are consistent among the research teams and compare favourably with the experimental data in terms of trends and absolute values. The models were able to reproduce the main physical processes of the experiment. In particular, most teams simulated temperature and thermally induced pore water pressure well, including spatial variations caused by inherent anisotropy due to bedding.« less

Modelling the Mont Terri HE-D experiment for the Thermal–Hydraulic–Mechanical response of a bedded argillaceous formation to heating

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garitte, B.; Nguyen, T. S.; Barnichon, J. D.

Coupled thermal–hydrological–mechanical (THM) processes in the near field of deep geological repositories can influence several safety features of the engineered and geological barriers. Among those features are: the possibility of damage in the host rock, the time for re-saturation of the bentonite, and the perturbations in the hydraulic regime in both the rock and engineered seals. Within the international cooperative code-validation project DECOVALEX-2015, eight research teams developed models to simulate an in situ heater experiment, called HE-D, in Opalinus Clay at the Mont Terri Underground Research Laboratory in Switzerland. The models were developed from the theory of poroelasticity in ordermore » to simulate the coupled THM processes that prevailed during the experiment and thereby to characterize the in situ THM properties of Opalinus Clay. The modelling results for the evolution of temperature, pore water pressure, and deformation at different points are consistent among the research teams and compare favourably with the experimental data in terms of trends and absolute values. The models were able to reproduce the main physical processes of the experiment. In particular, most teams simulated temperature and thermally induced pore water pressure well, including spatial variations caused by inherent anisotropy due to bedding.« less

Ginzburg-Landau equation as a heuristic model for generating rogue waves

NASA Astrophysics Data System (ADS)

Lechuga, Antonio

2016-04-01

Envelope equations have many applications in the study of physical systems. Particularly interesting is the case 0f surface water waves. In steady conditions, laboratory experiments are carried out for multiple purposes either for researches or for practical problems. In both cases envelope equations are useful for understanding qualitative and quantitative results. The Ginzburg-Landau equation provides an excellent model for systems of that kind with remarkable patterns. Taking into account the above paragraph the main aim of our work is to generate waves in a water tank with almost a symmetric spectrum according to Akhmediev (2011) and thus, to produce a succession of rogue waves. The envelope of these waves gives us some patterns whose model is a type of Ginzburg-Landau equation, Danilov et al (1988). From a heuristic point of view the link between the experiment and the model is achieved. Further, the next step consists of changing generating parameters on the water tank and also the coefficients of the Ginzburg-Landau equation, Lechuga (2013) in order to reach a sufficient good approach.

Impact of climate variations on Managed Aquifer Recharge infiltration basins.

NASA Astrophysics Data System (ADS)

Barquero, Felix; Stefan, Catalin

2017-04-01

KEYWORDS: Managed Aquifer Recharge, field scale infiltration unit, climatic conditions, numerical model Managed Aquifer Recharge (MAR) is a technique that is gaining more attention as a sustainable alternative for areas where water scarcity is increasing. Main concept relies on facilitating the vertical infiltration of a source of fresh water (river water, rainwater, reclaimed water, etc). The groundwater acts as storage of water for further use in the future, for example in times of water scarcity. In some MAR types the soil itself can be used even as a filter for the removal of specific organic and inorganic compounds. In order to promote the benefits of MAR in different zones of the globe with variable climate conditions, including the effects of climate change, a numerical model (HYDRUS 2D/3D) is being set up. Coupled with the model a field-scale rapid infiltration unit (4m x 5m x 1.5m) was constructed with the capacity to log different MAR key parameters in the soil (tension, water content, temperature and electrical conductivity) in space and time. These data will feed the model for its calibration using specific hydrogeological characteristics of the packing material and hydraulic characteristics of the infiltrated fluid. The unit is located in the city of Pirna (German), 200 m north from the Elbe River where the groundwater level varies seasonally between 6 and 9 m below the ground surface. Together with the field scale rapid infiltration unit, a set of multi-parametric sensors (measuring in time: water stage, electrical conductivity, dissolved oxygen and temperature) in six monitoring wells, located on the basin surroundings, were installed. The purpose of these sensors is to estimate, via tracer experiments, the time that the infiltrated water needed to reach the groundwater and the flow speed in which it travelled once it reached the saturated zone. Once calibrated, the model will be able to estimate the flow behaviour under variable climate conditions (temperature, precipitation and evaporation), representative for different climatic zones in the globe. The simulation results of the different climate models reported by the IPCC will also be considered for critical zones where fresh water availability will decrease considerably. In the field, the first results confirmed the arrival, after 14 days of travel time, of the infiltrated river water front to the monitoring wells located next to the infiltration unit. Further tracer experiments have to be performed in order to catch a stronger breakthrough curve in more than one observation point. Interesting open questions arise from the data stored in the trench sensors. How the change of the travel velocity depends on different external parameters like time of operation, cyclic wetting and drying regime and temperature, will be analysed together with the results of the ongoing experiments.

Cloud/climate sensitivity experiments

NASA Technical Reports Server (NTRS)

Roads, J. O.; Vallis, G. K.; Remer, L.

1982-01-01

A study of the relationships between large-scale cloud fields and large scale circulation patterns is presented. The basic tool is a multi-level numerical model comprising conservation equations for temperature, water vapor and cloud water and appropriate parameterizations for evaporation, condensation, precipitation and radiative feedbacks. Incorporating an equation for cloud water in a large-scale model is somewhat novel and allows the formation and advection of clouds to be treated explicitly. The model is run on a two-dimensional, vertical-horizontal grid with constant winds. It is shown that cloud cover increases with decreased eddy vertical velocity, decreased horizontal advection, decreased atmospheric temperature, increased surface temperature, and decreased precipitation efficiency. The cloud field is found to be well correlated with the relative humidity field except at the highest levels. When radiative feedbacks are incorporated and the temperature increased by increasing CO2 content, cloud amounts decrease at upper-levels or equivalently cloud top height falls. This reduces the temperature response, especially at upper levels, compared with an experiment in which cloud cover is fixed.

Water Budget Estimation by Assimilating Multiple Observations and Hydrological Modeling Using Constrained Ensemble Kalman Filtering

NASA Astrophysics Data System (ADS)

Pan, M.; Wood, E. F.

2004-05-01

This study explores a method to estimate various components of the water cycle (ET, runoff, land storage, etc.) based on a number of different info sources, including both observations and observation-enhanced model simulations. Different from existing data assimilations, this constrained Kalman filtering approach keeps the water budget perfectly closed while updating the states of the underlying model (VIC model) optimally using observations. Assimilating different data sources in this way has several advantages: (1) physical model is included to make estimation time series smooth, missing-free, and more physically consistent; (2) uncertainties in the model and observations are properly addressed; (3) model is constrained by observation thus to reduce model biases; (4) balance of water is always preserved along the assimilation. Experiments are carried out in Southern Great Plain region where necessary observations have been collected. This method may also be implemented in other applications with physical constraints (e.g. energy cycles) and at different scales.

Modeling contribution of shallow groundwater to evapotranspiration and yield of maize in an arid area

NASA Astrophysics Data System (ADS)

Gao, Xiaoyu; Huo, Zailin; Qu, Zhongyi; Xu, Xu; Huang, Guanhua; Steenhuis, Tammo S.

2017-02-01

Capillary rise from shallow groundwater can decrease the need for irrigation water. However, simple techniques do not exist to quantify the contribution of capillary flux to crop water use. In this study we develop the Agricultural Water Productivity Model for Shallow Groundwater (AWPM-SG) for calculating capillary fluxes from shallow groundwater using readily available data. The model combines an analytical solution of upward flux from groundwater with the EPIC crop growth model. AWPM-SG was calibrated and validated with 2-year lysimetric experiment with maize. Predicted soil moisture, groundwater depth and leaf area index agreed with the observations. To investigate the response of model, various scenarios were run in which the irrigation amount and groundwater depth were varied. Simulations shows that at groundwater depth of 1 m capillary upward supplied 41% of the evapotranspiration. This reduced to 6% at groundwater depth of 2 m. The yield per unit water consumed (water productivity) was nearly constant for 2.3 kg/m3. The yield per unit water applied (irrigation water productivity) increased with decreasing irrigation water because capillary rise made up in part for the lack of irrigation water. Consequently, using AWPM-SG in irrigation scheduling will be beneficial to save more water in areas with shallow groundwater.

Modeling contribution of shallow groundwater to evapotranspiration and yield of maize in an arid area

PubMed Central

Gao, Xiaoyu; Huo, Zailin; Qu, Zhongyi; Xu, Xu; Huang, Guanhua; Steenhuis, Tammo S.

2017-01-01

Capillary rise from shallow groundwater can decrease the need for irrigation water. However, simple techniques do not exist to quantify the contribution of capillary flux to crop water use. In this study we develop the Agricultural Water Productivity Model for Shallow Groundwater (AWPM-SG) for calculating capillary fluxes from shallow groundwater using readily available data. The model combines an analytical solution of upward flux from groundwater with the EPIC crop growth model. AWPM-SG was calibrated and validated with 2-year lysimetric experiment with maize. Predicted soil moisture, groundwater depth and leaf area index agreed with the observations. To investigate the response of model, various scenarios were run in which the irrigation amount and groundwater depth were varied. Simulations shows that at groundwater depth of 1 m capillary upward supplied 41% of the evapotranspiration. This reduced to 6% at groundwater depth of 2 m. The yield per unit water consumed (water productivity) was nearly constant for 2.3 kg/m3. The yield per unit water applied (irrigation water productivity) increased with decreasing irrigation water because capillary rise made up in part for the lack of irrigation water. Consequently, using AWPM-SG in irrigation scheduling will be beneficial to save more water in areas with shallow groundwater. PMID:28220874

Modeling contribution of shallow groundwater to evapotranspiration and yield of maize in an arid area.

PubMed

Gao, Xiaoyu; Huo, Zailin; Qu, Zhongyi; Xu, Xu; Huang, Guanhua; Steenhuis, Tammo S

2017-02-21

Capillary rise from shallow groundwater can decrease the need for irrigation water. However, simple techniques do not exist to quantify the contribution of capillary flux to crop water use. In this study we develop the Agricultural Water Productivity Model for Shallow Groundwater (AWPM-SG) for calculating capillary fluxes from shallow groundwater using readily available data. The model combines an analytical solution of upward flux from groundwater with the EPIC crop growth model. AWPM-SG was calibrated and validated with 2-year lysimetric experiment with maize. Predicted soil moisture, groundwater depth and leaf area index agreed with the observations. To investigate the response of model, various scenarios were run in which the irrigation amount and groundwater depth were varied. Simulations shows that at groundwater depth of 1 m capillary upward supplied 41% of the evapotranspiration. This reduced to 6% at groundwater depth of 2 m. The yield per unit water consumed (water productivity) was nearly constant for 2.3 kg/m 3 . The yield per unit water applied (irrigation water productivity) increased with decreasing irrigation water because capillary rise made up in part for the lack of irrigation water. Consequently, using AWPM-SG in irrigation scheduling will be beneficial to save more water in areas with shallow groundwater.

Numerical study of water mitigation effects on blast wave

NASA Astrophysics Data System (ADS)

Cheng, M.; Hung, K. C.; Chong, O. Y.

2005-11-01

The mitigating effect of a water wall on the generation and propagation of blast waves of a nearby explosive has been investigated using a numerical approach. A multimaterial Eulerian finite element technique is used to study the influence of the design parameters, such as the water-to-explosive weight ratio, the water wall thickness, the air-gap and the cover area ratio of water on the effectiveness of the water mitigation concept. In the computational model, the detonation gases are modelled with the standard Jones Wilkins Lee (JWL) equation of state. Water, on the other hand, is treated as a compressible fluid with the Mie Gruneisen equation of state model. The validity of the computational model is checked against a limited amount of available experimental data, and the influence of mesh sizes on the convergence of results is also discussed. From the results of the extensive numerical experiments, it is deduced that firstly, the presence of an air-gap reduces the effectiveness of the water mitigator. Secondly, the higher the water-to-explosive weight ratio, the more significant is the reduction in peak pressure of the explosion. Typically, water-to-explosive weight ratios in the range of 1 3 are found to be most practical.

Numerical modeling of water spray suppression of conveyor belt fires in a large-scale tunnel.

PubMed

Yuan, Liming; Smith, Alex C

2015-05-01

Conveyor belt fires in an underground mine pose a serious life threat to miners. Water sprinkler systems are usually used to extinguish underground conveyor belt fires, but because of the complex interaction between conveyor belt fires and mine ventilation airflow, more effective engineering designs are needed for the installation of water sprinkler systems. A computational fluid dynamics (CFD) model was developed to simulate the interaction between the ventilation airflow, the belt flame spread, and the water spray system in a mine entry. The CFD model was calibrated using test results from a large-scale conveyor belt fire suppression experiment. Simulations were conducted using the calibrated CFD model to investigate the effects of sprinkler location, water flow rate, and sprinkler activation temperature on the suppression of conveyor belt fires. The sprinkler location and the activation temperature were found to have a major effect on the suppression of the belt fire, while the water flow rate had a minor effect.

Numerical modeling of water spray suppression of conveyor belt fires in a large-scale tunnel

PubMed Central

Yuan, Liming; Smith, Alex C.

2015-01-01

Conveyor belt fires in an underground mine pose a serious life threat to miners. Water sprinkler systems are usually used to extinguish underground conveyor belt fires, but because of the complex interaction between conveyor belt fires and mine ventilation airflow, more effective engineering designs are needed for the installation of water sprinkler systems. A computational fluid dynamics (CFD) model was developed to simulate the interaction between the ventilation airflow, the belt flame spread, and the water spray system in a mine entry. The CFD model was calibrated using test results from a large-scale conveyor belt fire suppression experiment. Simulations were conducted using the calibrated CFD model to investigate the effects of sprinkler location, water flow rate, and sprinkler activation temperature on the suppression of conveyor belt fires. The sprinkler location and the activation temperature were found to have a major effect on the suppression of the belt fire, while the water flow rate had a minor effect. PMID:26190905

Well logging interpretation of production profile in horizontal oil-water two phase flow pipes

NASA Astrophysics Data System (ADS)

Zhai, Lu-Sheng; Jin, Ning-De; Gao, Zhong-Ke; Zheng, Xi-Ke

2012-03-01

Due to the complicated distribution of local velocity and local phase hold up along the radial direction of pipe in horizontal oil-water two phase flow, it is difficult to measure the total flow rate and phase volume fraction. In this study, we carried out dynamic experiment in horizontal oil-water two phases flow simulation well by using combination measurement system including turbine flowmeter with petal type concentrating diverter, conductance sensor and flowpassing capacitance sensor. According to the response resolution ability of the conductance and capacitance sensor in different range of total flow rate and water-cut, we use drift flux model and statistical model to predict the partial phase flow rate, respectively. The results indicate that the variable coefficient drift flux model can self-adaptively tone the model parameter according to the oil-water two phase flow characteristic, and the prediction result of partial phase flow rate of oil-water two phase flow is of high accuracy.

Solvent-shared pairs of densely charged ions induce intense but short-range supra-additive slowdown of water rotation.

PubMed

Vila Verde, Ana; Santer, Mark; Lipowsky, Reinhard

2016-01-21

The question "Can ions exert supra-additive effects on water dynamics?" has had several opposing answers from both simulation and experiment. We address this ongoing controversy by investigating water reorientation in aqueous solutions of two salts with large (magnesium sulfate) and small (cesium chloride) effects on water dynamics using molecular dynamics simulations and classical, polarizable models. The salt models are reparameterized to reproduce properties of both dilute and concentrated solutions. We demonstrate that water rotation in concentrated MgSO4 solutions is unexpectedly slow, in agreement with experiment, and that the slowdown is supra-additive: the observed slowdown is larger than that predicted by assuming that the resultant of the extra forces induced by the ions on the rotating water molecules tilts the free energy landscape associated with water rotation. Supra-additive slow down is very intense but short-range, and is strongly ion-specific: in contrast to the long-range picture initially proposed based on experiment, we find that intense supra-additivity is limited to water molecules directly bridging two ions in solvent-shared ion pair configuration; in contrast to a non-ion-specific origin to supra-additive effects proposed from simulations, we find that the magnitude of supra-additive slowdown strongly depends on the identity of the cations and anions. Supra-additive slowdown of water dynamics requires long-lived solvent-shared ion pairs; long-lived ion pairs should be typical for salts of multivalent ions. We discuss the origin of the apparent disagreement between the various studies on this topic and show that the short-range cooperative slowdown scenario proposed here resolves the existing controversy.

Modeling the photodegradation of emerging contaminants in waters by UV radiation and UV/H2O2 system.

PubMed

Benitez, F Javier; Acero, Juan L; Real, Francisco J; Roldan, Gloria; Rodriguez, Elena

2013-01-01

Five emerging contaminants (1-H-Benzotriazole, N,N-diethyl-m-toluamide or DEET, Chlorophene, 3-Methylindole, and Nortriptyline HCl), frequently found in surface waters and wastewaters, were selected to be photooxidized in several water matrices. Previous degradation experiments of these compounds individually dissolved in ultra pure water were performed by using UV radiation at 254 nm and the Fenton's reagent. These oxidation systems allowed the determination of the quantum yields and the rate constants for the radical reaction between each compound and hydroxyl radicals. Later, the simultaneous photodegradation of mixtures of the selected ECs in several types of water (ultrapure water, reservoir water, and two effluents from WWTPs) was carried out and a kinetic study was conducted. A model is proposed for the ECs elimination, and the theoretically calculated concentrations with this model agreed well with the experimental results obtained, which confirmed that it constitutes an excellent tool to predict the elimination of these compounds in waters.

Quantifying the Effect of Soil Water Repellency on Infiltration Parameters Using a Dry Sand

NASA Astrophysics Data System (ADS)

Shillito, R.; Berli, M.; Ghezzehei, T. A.; Kaminski, E.

2017-12-01

Water infiltration into less than perfectly wettable soils has usually been considered an exceptional case—in fact, it may be the rule. Infiltration into soils exhibiting some degree of water repellency has important implications in agricultural irrigation, post-fire runoff, golf course and landscape management, and spill and contaminant mitigation. Beginning from fundamental principles, we developed a physically-based model to quantify the effect of water repellency on infiltration parameters. Experimentally, we used a dry silica sand and treated it to achieve various known degrees of water repellency. The model was verified using data gathered from multiple upward infiltration (wicking) experiments using the treated sand. The model also allowed us to explore the effect of initial soil moisture conditions on infiltration into water-repellent soils, and the physical interpretation of the simple water drop penetration time test. These results provide a fundamental step in the physically-based understanding of how water infiltrates into a less than perfectly wettable porous media.

A vegetation-focused soil-plant-atmospheric continuum model to study hydrodynamic soil-plant water relations

NASA Astrophysics Data System (ADS)

Deng, Zijuan; Guan, Huade; Hutson, John; Forster, Michael A.; Wang, Yunquan; Simmons, Craig T.

2017-06-01

A novel simple soil-plant-atmospheric continuum model that emphasizes the vegetation's role in controlling water transfer (v-SPAC) has been developed in this study. The v-SPAC model aims to incorporate both plant and soil hydrological measurements into plant water transfer modeling. The model is different from previous SPAC models in which v-SPAC uses (1) a dynamic plant resistance system in the form of a vulnerability curve that can be easily obtained from sap flow and stem xylem water potential time series and (2) a plant capacitance parameter to buffer the effects of transpiration on root water uptake. The unique representation of root resistance and capacitance allows the model to embrace SPAC hydraulic pathway from bulk soil, to soil-root interface, to root xylem, and finally to stem xylem where the xylem water potential is measured. The v-SPAC model was tested on a native tree species in Australia, Eucalyptus crenulata saplings, with controlled drought treatment. To further validate the robustness of the v-SPAC model, it was compared against a soil-focused SPAC model, LEACHM. The v-SPAC model simulation results closely matched the observed sap flow and stem water potential time series, as well as the soil moisture variation of the experiment. The v-SPAC model was found to be more accurate in predicting measured data than the LEACHM model, underscoring the importance of incorporating root resistance into SPAC models and the benefit of integrating plant measurements to constrain SPAC modeling.

Modeling and optimization of trihalomethanes formation potential of surface water (a drinking water source) using Box-Behnken design.

PubMed

Singh, Kunwar P; Rai, Premanjali; Pandey, Priyanka; Sinha, Sarita

2012-01-01

The present research aims to investigate the individual and interactive effects of chlorine dose/dissolved organic carbon ratio, pH, temperature, bromide concentration, and reaction time on trihalomethanes (THMs) formation in surface water (a drinking water source) during disinfection by chlorination in a prototype laboratory-scale simulation and to develop a model for the prediction and optimization of THMs levels in chlorinated water for their effective control. A five-factor Box-Behnken experimental design combined with response surface and optimization modeling was used for predicting the THMs levels in chlorinated water. The adequacy of the selected model and statistical significance of the regression coefficients, independent variables, and their interactions were tested by the analysis of variance and t test statistics. The THMs levels predicted by the model were very close to the experimental values (R(2) = 0.95). Optimization modeling predicted maximum (192 μg/l) TMHs formation (highest risk) level in water during chlorination was very close to the experimental value (186.8 ± 1.72 μg/l) determined in laboratory experiments. The pH of water followed by reaction time and temperature were the most significant factors that affect the THMs formation during chlorination. The developed model can be used to determine the optimum characteristics of raw water and chlorination conditions for maintaining the THMs levels within the safe limit.

Numerical simulation of water injection into vapor-dominated reservoirs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pruess, K.

1995-01-01

Water injection into vapor-dominated reservoirs is a means of condensate disposal, as well as a reservoir management tool for enhancing energy recovery and reservoir life. We review different approaches to modeling the complex fluid and heat flow processes during injection into vapor-dominated systems. Vapor pressure lowering, grid orientation effects, and physical dispersion of injection plumes from reservoir heterogeneity are important considerations for a realistic modeling of injection effects. An example of detailed three-dimensional modeling of injection experiments at The Geysers is given.

From Buckets to Basins: Scaling up from the CZO to the NOAA National Water Model

NASA Astrophysics Data System (ADS)

Dugger, A. L.; Gochis, D.; Cosgrove, B.; Sampson, K. M.; McCreight, J. L.; Rafieeinasab, A.

2017-12-01

NOAA's National Water Model (NWM) is generating terabytes of data on current and future states of water in streams, soils, snowpacks, lakes, and floodplains across the U.S. Altogether there are approximately 2.7 million stream reaches in the NWM and land cells distributed every 250-m (soil moisture, inundation) and 1-km (snow, evapotranspiration). Water predictions span the next hour to the next 30 days. Flood forecasting is an obvious NWM priority in the near term, but longer-range plans extend to water supply planning, drought forecasting, and water quality. An obvious question posed to a model operating across this many dimensions of space, time, and variables is: are you including the right processes and parameterizations to capture the hydrologic behaviors you are designed for? To answer this question, we generally rely on networks of in-situ observations to constrain models via parameter estimation or evaluate alternate process representations. While this gets us part of the way there, the question remains how well these in-situ characterizations scale up in the context of a national-scale model. The WRF-Hydro community hydrologic modeling system provides the initial backbone for the NWM, driving simulation of water and energy within the critical zone - vertical energy and water fluxes, lateral redistribution of surface and subsurface water, simple deep groundwater dynamics, and channel routing. In this study, we first present baseline performance of the NWM over US-wide networks of streamflow (USGS), soil moisture (CRN, SCAN), and evapotranspiration (Ameriflux) observations at a range of spatial and temporal scales. We conduct a series of simple experiments using different submodel combinations of WRF-Hydro at high-resolution to predict water storage and partitioning behavior at 3 well-instrumented catchments, with the goal of optimizing combined performance of snowpack, soil moisture, ET, and streamflow prediction. We scale-up the optimal physics suites and parameters to the Omernik Level 3 Ecoregion at the NWM scale and assess changes in water storage and partitioning at all gages within the ecoregion. While this is a fairly limited experiment, we hope to engage the critical zone research community in considering how we can leverage the CZO networks to inform NWM model improvement.

Groundwater development stress: Global-scale indices compared to regional modeling

USGS Publications Warehouse

Alley, William; Clark, Brian R.; Ely, Matt; Faunt, Claudia

2018-01-01

The increased availability of global datasets and technologies such as global hydrologic models and the Gravity Recovery and Climate Experiment (GRACE) satellites have resulted in a growing number of global-scale assessments of water availability using simple indices of water stress. Developed initially for surface water, such indices are increasingly used to evaluate global groundwater resources. We compare indices of groundwater development stress for three major agricultural areas of the United States to information available from regional water budgets developed from detailed groundwater modeling. These comparisons illustrate the potential value of regional-scale analyses to supplement global hydrological models and GRACE analyses of groundwater depletion. Regional-scale analyses allow assessments of water stress that better account for scale effects, the dynamics of groundwater flow systems, the complexities of irrigated agricultural systems, and the laws, regulations, engineering, and socioeconomic factors that govern groundwater use. Strategic use of regional-scale models with global-scale analyses would greatly enhance knowledge of the global groundwater depletion problem.

Thermodynamical effects accompanied freezing of two water layers separated by sea ice sheet

NASA Astrophysics Data System (ADS)

Bogorodsky, Petr; Marchenko, Aleksey

2014-05-01

The process of melt pond freezing is very important for generation of sea ice cover thermodynamic and mass balance during winterperiod. However, due to significant difficulties of field measurements the available data of model estimations still have no instrumental confirmation. In May 2009 the authors carried out laboratory experiment on freezing of limited water volume in the University Centre in Svalbard ice tank. In the course of experiment fresh water layer of 27.5 cm thickness at freezing point poured on the 24 cm sea ice layer was cooled during 50 hours at the temperature -10º C and then once again during 60 hours at -20º C. For revealing process typical characteristics the data of continuous measurements of temperature and salinity in different phases were compared with data of numerical computations obtained with thermodynamic model which was formulated in the frames of 1-D equation system (infinite extension of water freezing layer) and adapted to laboratory conditions. The known surprise of the experiment became proximity of calculated and measured estimates of process dynamics that confirmed the adequacy of the problem mathematical statement (excluding probably process finale stage). This effect can be explained by formation of cracks on the upper layer of ice at sharp decreases of air temperature, which temporary compensated hydrostatic pressure growth during freezing of closed water volume. Another compensated mechanism can be migration of brine through the lower layer of ice under influence of vertical pressure gradient and also rejection of gas dissolved in water which increased its compressibility. During 110 hours cooling thickness of water layer between ice layers reduced approximately to 2 cm. According to computations this layer is not chilled completely but keeps as thin brine interlayer within ice body whose thickness (about units of mm) is determined by temperature fluctuations of cooled surface. Nevertheless, despite good coincidence of experimental and model estimates the question of existence of liquid phase under actual conditions is still open and can be clarified in a continuous laboratory experiment. This work was supported by Russian Foundation for Basic Research (Project # 14-05-00677).

Modelling non-steady-state isotope enrichment of leaf water in a gas-exchange cuvette environment.

PubMed

Song, Xin; Simonin, Kevin A; Loucos, Karen E; Barbour, Margaret M

2015-12-01

The combined use of a gas-exchange system and laser-based isotope measurement is a tool of growing interest in plant ecophysiological studies, owing to its relevance for assessing isotopic variability in leaf water and/or transpiration under non-steady-state (NSS) conditions. However, the current Farquhar & Cernusak (F&C) NSS leaf water model, originally developed for open-field scenarios, is unsuited for use in a gas-exchange cuvette environment where isotope composition of water vapour (δv ) is intrinsically linked to that of transpiration (δE ). Here, we modified the F&C model to make it directly compatible with the δv -δE dynamic characteristic of a typical cuvette setting. The resultant new model suggests a role of 'net-flux' (rather than 'gross-flux' as suggested by the original F&C model)-based leaf water turnover rate in controlling the time constant (τ) for the approach to steady sate. The validity of the new model was subsequently confirmed in a cuvette experiment involving cotton leaves, for which we demonstrated close agreement between τ values predicted from the model and those measured from NSS variations in isotope enrichment of transpiration. Hence, we recommend that our new model be incorporated into future isotope studies involving a cuvette condition where the transpiration flux directly influences δv . There is an increasing popularity among plant ecophysiologists to use a gas-exchange system coupled to laser-based isotope measurement for investigating non-steady state (NSS) isotopic variability in leaf water (and/or transpiration); however, the current Farquhar & Cernusak (F&C) NSS leaf water model is unsuited for use in a gas-exchange cuvette environment due to its implicit assumption of isotope composition of water vapor (δv ) being constant and independent of that of transpiration (δE ). In the present study, we modified the F&C model to make it compatible with the dynamic relationship between δv and δE as is typically associated with a cuvette setting. Using an experiment conducted on cotton leaves, we show that the modified NSS model performed well in predicting the time constant for the exponential approach of leaf water toward steady state under cuvette conditions. Such a result demonstrates the applicability of this new model to gas-exchange cuvette conditions where the transpiration flux directly influences δv , and therefore suggests the need to incorporate this model into future isotope studies that employ a laser-cuvette coupled system. © 2015 John Wiley & Sons Ltd.

Simulations of initial MHD experiments on the Madison Dynamo Experiment

NASA Astrophysics Data System (ADS)

O'Connell, R.; Forest, C. B.; Goldwin, J. M.; Kendrick, R. D.; Canary, H. W.; Nornberg, M. D.; Jaun, A.

1999-11-01

Initial experiments for a liquid metal MHD device have been modelled using measurements from geometrically similar water experiments. In the low B limit the water flows are the same as sodium flows. Two codes have been written to predict 1) linear stability of the system and 2) the response of the system to an externally applied vertical magnetic field, using measured velocity profiles. Predictions are made for a first set of MHD experiments, including: a) demonstration of the distortion and amplification of externally applied magnetic fields by sheared flows, b) demonstration of the β-effect by measurement of the turbulent conductivity, c) demonstration of a turbulent α effect and d) characterization of magnetic eigenmodes.

Statistical characterization of fluctuations of a laser beam transmitted through a random air-water interface: new results from a laboratory experiment

NASA Astrophysics Data System (ADS)

Majumdar, Arun K.; Land, Phillip; Siegenthaler, John

2014-10-01

New results for characterizing laser intensity fluctuation statistics of a laser beam transmitted through a random air-water interface relevant to underwater communications are presented. A laboratory watertank experiment is described to investigate the beam wandering effects of the transmitted beam. Preliminary results from the experiment provide information about histograms of the probability density functions of intensity fluctuations for different wind speeds measured by a CMOS camera for the transmitted beam. Angular displacements of the centroids of the fluctuating laser beam generates the beam wander effects. This research develops a probabilistic model for optical propagation at the random air-water interface for a transmission case under different wind speed conditions. Preliminary results for bit-error-rate (BER) estimates as a function of fade margin for an on-off keying (OOK) optical communication through the air-water interface are presented for a communication system where a random air-water interface is a part of the communication channel.

Contemporary multilevel analysis of the effectiveness of water fluoridation in Australia.

PubMed

Do, Loc; Spencer, A John

2015-02-01

Water fluoridation was extended in Queensland, Australia, across 2009-2011. A research program was commenced to inform the rationale for and the outcome of this program, to estimate the effectiveness of water fluoridation in preventing caries and to predict changes in caries experience as a result of the extension of fluoridation. Queensland children were selected through a stratified random sample selection in 2010-2012. Oral epidemiological examinations provided individual-level outcomes for decayed, missing or filled primary or permanent tooth surfaces: dmfs (among 5-8-year-olds) and DMFS (9-14-year-olds). Explanatory factors at the individual-level, school-level and area-level fluoridation status were derived. Data were weighted to represent the population. Three-level multilevel multivariable models were sequentially specified for negative binomial distribution of dmfs/DMFS to estimate rate ratios (RR). The effectiveness of area-level water fluoridation was evaluated in the full models controlling for other factors. Data from 2,214 5-8 year-olds and 3,186 9-14 year-olds from 207 schools in 16 areas were analysed. Queensland's average dmfs was 4.23 and DMFS 1.47. The lowest levels of dental caries were observed in long-term fluoridated Townsville. In the full models, Townsville children had significantly lower caries experience (RR for dmfs: 0.61 (95%CI: 0.44-0.82); RR for DMFS 0.60 (95%CI: 0.42-0.88)) compared with children in non-fluoridated areas. Comparison of caries experience of children at the time of the extension of water fluoridation supported the rationale for this population health measure. © 2014 Public Health Association of Australia.

Effects of Precipitation on Ocean Mixed-Layer Temperature and Salinity as Simulated in a 2-D Coupled Ocean-Cloud Resolving Atmosphere Model

NASA Technical Reports Server (NTRS)

Li, Xiaofan; Sui, C.-H.; Lau, K-M.; Adamec, D.

1999-01-01

A two-dimensional coupled ocean-cloud resolving atmosphere model is used to investigate possible roles of convective scale ocean disturbances induced by atmospheric precipitation on ocean mixed-layer heat and salt budgets. The model couples a cloud resolving model with an embedded mixed layer-ocean circulation model. Five experiment are performed under imposed large-scale atmospheric forcing in terms of vertical velocity derived from the TOGA COARE observations during a selected seven-day period. The dominant variability of mixed-layer temperature and salinity are simulated by the coupled model with imposed large-scale forcing. The mixed-layer temperatures in the coupled experiments with 1-D and 2-D ocean models show similar variations when salinity effects are not included. When salinity effects are included, however, differences in the domain-mean mixed-layer salinity and temperature between coupled experiments with 1-D and 2-D ocean models could be as large as 0.3 PSU and 0.4 C respectively. Without fresh water effects, the nocturnal heat loss over ocean surface causes deep mixed layers and weak cooling rates so that the nocturnal mixed-layer temperatures tend to be horizontally-uniform. The fresh water flux, however, causes shallow mixed layers over convective areas while the nocturnal heat loss causes deep mixed layer over convection-free areas so that the mixed-layer temperatures have large horizontal fluctuations. Furthermore, fresh water flux exhibits larger spatial fluctuations than surface heat flux because heavy rainfall occurs over convective areas embedded in broad non-convective or clear areas, whereas diurnal signals over whole model areas yield high spatial correlation of surface heat flux. As a result, mixed-layer salinities contribute more to the density differences than do mixed-layer temperatures.

Modeling biophysical/biogeochemical/ecological/ocean/atmosphere two-way interactions using NCEP CFS/SSiB5/TRIFFID/DAYCENT: challenge and promising

NASA Astrophysics Data System (ADS)

Xue, Y.; Liu, Y.; Cox, P. M.; De Sales, F.; Lee, J.; Marx, L.; Hartman, M. D.; Yang, R.; Parton, W. J.; Qiu, B.; Ek, M. B.

2016-12-01

Evaluations of several dynamic vegetation models' (DVM) performances in the offline experiments and in the CMIP5 simulations suggest that most of the DVMs substantially overestimate leaf area index (LAI) and length of the growing season, which contribute to overestimation in their coupled models' precipitation. These results suggest important deficiencies in today's DVMs but also show the importance of proper ecological processes in the Earth System Modeling. We have developed a water-carbon-energy balance-based ecosystem model (SSiB4/TRIFFID) and verified it with field and satellite measurement at seasonal to decadal and longer scales. In the global offline tests, the model was integrated from 1950 to 2010 driven by observed meteorological forcing. The simulated trend and decadal variabilities in surface ecosystem conditions (e.g., Plant functional types, LAI, GPP), and surface water and energy balances are analyzed; further experiments and analyses are carried to isolate the contribution due to elevated atmospheric carbon concentration, global warming, soil moisture, and climate variability. How nitrogen processes simulated by the DayCent model Climate Forecast System (CFS) model, which has consistently shown improvements in simulated atmospheric & ocean conditions compared with those runs with specified vegetation conditions. In an experiment, two parametrizations that calculate the mean water potential in soil layers, which affect transpiration and plants' mortality, are tested. It shows that these two methods have substantial impact on global decadal variability of precipitation and surface temperature, with even opposite signs over some regions in the worlds. These results show the uncertainty in DVM modeling with significant implication for the future prediction. It is imperative to evaluate DVMs with comprehensive observational data.

Accuracy limit of rigid 3-point water models

NASA Astrophysics Data System (ADS)

Izadi, Saeed; Onufriev, Alexey V.

2016-08-01

Classical 3-point rigid water models are most widely used due to their computational efficiency. Recently, we introduced a new approach to constructing classical rigid water models [S. Izadi et al., J. Phys. Chem. Lett. 5, 3863 (2014)], which permits a virtually exhaustive search for globally optimal model parameters in the sub-space that is most relevant to the electrostatic properties of the water molecule in liquid phase. Here we apply the approach to develop a 3-point Optimal Point Charge (OPC3) water model. OPC3 is significantly more accurate than the commonly used water models of same class (TIP3P and SPCE) in reproducing a comprehensive set of liquid bulk properties, over a wide range of temperatures. Beyond bulk properties, we show that OPC3 predicts the intrinsic charge hydration asymmetry (CHA) of water — a characteristic dependence of hydration free energy on the sign of the solute charge — in very close agreement with experiment. Two other recent 3-point rigid water models, TIP3PFB and H2ODC, each developed by its own, completely different optimization method, approach the global accuracy optimum represented by OPC3 in both the parameter space and accuracy of bulk properties. Thus, we argue that an accuracy limit of practical 3-point rigid non-polarizable models has effectively been reached; remaining accuracy issues are discussed.

Dielectric constant and low-frequency infrared spectra for liquid water and ice Ih within the E3B model.

PubMed

Shi, L; Ni, Y; Drews, S E P; Skinner, J L

2014-08-28

Two intrinsic difficulties in modeling condensed-phase water with conventional rigid non-polarizable water models are: reproducing the static dielectric constants for liquid water and ice Ih, and generating the peak at about 200 cm(-1) in the low-frequency infrared spectrum for liquid water. The primary physical reason for these failures is believed to be the missing polarization effect in these models, and consequently various sophisticated polarizable water models have been developed. However, in this work we pursue a different strategy and propose a simple empirical scheme to include the polarization effect only on the dipole surface (without modifying a model's intermolecular interaction potential). We implement this strategy for our explicit three-body (E3B) model. Our calculated static dielectric constants and low-frequency infrared spectra are in good agreement with experiment for both liquid water and ice Ih over wide temperature ranges, albeit with one fitting parameter for each phase. The success of our modeling also suggests that thermal fluctuations about local minima and the energy differences between different proton-disordered configurations play minor roles in the static dielectric constant of ice Ih. Our analysis shows that the polarization effect is important in resolving the two difficulties mentioned above and sheds some light on the origin of several features in the low-frequency infrared spectra for liquid water and ice Ih.

[Homeopathy and structure of water: a physical model].

PubMed

Kratky, K W

2004-02-01

Formerly, the author has suggested a relatively simple water model. There, the dynamical structure of a typical water cluster was investigated, being represented by the movement of a ball in an abstract energy landscape. Now the above-mentioned model is investigated in more detail to answer the following question: Are essential claims of homeopathy concerning potentiation (diluting and shaking) in agreement with science? Equations of motion are employed that represent vibrations of clusters. For the computer experiments, the formalism of Nosé-Hoover is used, the surrounding water being interpreted as a heat bath. Diluting corresponds to a shift of the energy landscape towards the pure solvent (water), shaking is accompanied by an increase of the contact to the heat bath. There is a tendency of the ball to be caught in local valleys of the energy landscape (metastable states) if the temperature is not too high and if the liquid is not shaken. Thus, even for a given landscape there are a variety of structures being durable for some time. The computer experiments suggest that the repeated process of potentiation eventually results in a specific metastable state of the pure solvent. The initial substance helps to obtain this goal, but is no longer necessary at last. Copyright 2004 S. Karger GmbH, Freiburg

The Grape Remote Sensing Atmospheric Profile and Evapotranspiration eXperiment (GRAPEX): a multidisciplinary project to develop a robust remote sensing-based ET modeling tool for vineyards

USDA-ARS?s Scientific Manuscript database

The recent drought in much of California, particularly in the Central Valley region, has caused severe reduction in water reservoir levels and a major depletion of ground water by agriculture. Dramatic improvements in water and irrigation management practices are critical for agriculture to remain s...

Contrasting response to nutrient manipulation in Arctic mesocosms are reproduced by a minimum microbial food web model.

PubMed

Larsen, Aud; Egge, Jorun K; Nejstgaard, Jens C; Di Capua, Iole; Thyrhaug, Runar; Bratbak, Gunnar; Thingstad, T Frede

2015-03-01

A minimum mathematical model of the marine pelagic microbial food web has previously shown to be able to reproduce central aspects of observed system response to different bottom-up manipulations in a mesocosm experiment Microbial Ecosystem Dynamics (MEDEA) in Danish waters. In this study, we apply this model to two mesocosm experiments (Polar Aquatic Microbial Ecology (PAME)-I and PAME-II) conducted at the Arctic location Kongsfjorden, Svalbard. The different responses of the microbial community to similar nutrient manipulation in the three mesocosm experiments may be described as diatom-dominated (MEDEA), bacteria-dominated (PAME-I), and flagellated-dominated (PAME-II). When allowing ciliates to be able to feed on small diatoms, the model describing the diatom-dominated MEDEA experiment give a bacteria-dominated response as observed in PAME I in which the diatom community comprised almost exclusively small-sized cells. Introducing a high initial mesozooplankton stock as observed in PAME-II, the model gives a flagellate-dominated response in accordance with the observed response also of this experiment. The ability of the model originally developed for temperate waters to reproduce population dynamics in a 10°C colder Arctic fjord, does not support the existence of important shifts in population balances over this temperature range. Rather, it suggests a quite resilient microbial food web when adapted to in situ temperature. The sensitivity of the model response to its mesozooplankton component suggests, however, that the seasonal vertical migration of Arctic copepods may be a strong forcing factor on Arctic microbial food webs.

Contrasting response to nutrient manipulation in Arctic mesocosms are reproduced by a minimum microbial food web model

PubMed Central

Larsen, Aud; Egge, Jorun K; Nejstgaard, Jens C; Di Capua, Iole; Thyrhaug, Runar; Bratbak, Gunnar; Thingstad, T Frede

2015-01-01

A minimum mathematical model of the marine pelagic microbial food web has previously shown to be able to reproduce central aspects of observed system response to different bottom-up manipulations in a mesocosm experiment Microbial Ecosystem Dynamics (MEDEA) in Danish waters. In this study, we apply this model to two mesocosm experiments (Polar Aquatic Microbial Ecology (PAME)-I and PAME-II) conducted at the Arctic location Kongsfjorden, Svalbard. The different responses of the microbial community to similar nutrient manipulation in the three mesocosm experiments may be described as diatom-dominated (MEDEA), bacteria-dominated (PAME-I), and flagellated-dominated (PAME-II). When allowing ciliates to be able to feed on small diatoms, the model describing the diatom-dominated MEDEA experiment give a bacteria-dominated response as observed in PAME I in which the diatom community comprised almost exclusively small-sized cells. Introducing a high initial mesozooplankton stock as observed in PAME-II, the model gives a flagellate-dominated response in accordance with the observed response also of this experiment. The ability of the model originally developed for temperate waters to reproduce population dynamics in a 10°C colder Arctic fjord, does not support the existence of important shifts in population balances over this temperature range. Rather, it suggests a quite resilient microbial food web when adapted to in situ temperature. The sensitivity of the model response to its mesozooplankton component suggests, however, that the seasonal vertical migration of Arctic copepods may be a strong forcing factor on Arctic microbial food webs. PMID:26074626

Generation of ultra-fast cumulative water jets by sub-microsecond underwater electrical explosion of conical wire arrays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shafer, D.; Gurovich, V. Tz.; Gleizer, S.

The results of experiments with underwater electrical explosion of modified conical arrays of copper and aluminum wires are presented. A pulsed generator producing a 550 kA-amplitude current with a 400 ns rise time was used in the explosion of the arrays. The array explosion generates water flows converging at the axis of the cone. This flow generates a fast-moving water jet with a velocity exceeding 1.8 × 10{sup 5 }cm/s, which was observed being ejected from the surface of the water covering the array. The positions of the water jet were measured by multiple-exposure fast framing imaging. In experiments, the apex angle of the array,more » the thickness of the water layer above the arrays, or the material of the wires was altered, which changed the resulting velocities and shapes of the emitted jets. A model that considers the converging stationary flow of a slightly compressible fluid is suggested. The velocities and shapes of the jets obtained by this model agree well with the experimentally measured jet velocities.« less

A numerical model for simulation of bioremediation of hydrocarbons in aquifers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Munoz, J.F.; Irarrazaval, M.J.

1998-03-01

A numerical model was developed to describe the bioremediation of hydrocarbons in ground water aquifers considering aerobic degradation. The model solves the independent transport of three solutes (oxygen, hydrocarbons, and microorganisms) in ground water flow using the method of characteristics. Interactions between the three solutes, in which oxygen and hydrocarbons are consumed by microorganisms, are represented by Monod kinetics, solved using a Runge-Kutta method. Model simulations showed good correlation as compared with results of soil column experiments. The model was used to estimate the time needed to remediate the columns, which varied from one to two years.

Bacteriophage PRD1 batch experiments to study attachment, detachment and inactivation processes

NASA Astrophysics Data System (ADS)

Sadeghi, Gholamreza; Schijven, Jack F.; Behrends, Thilo; Hassanizadeh, S. Majid; van Genuchten, Martinus Th.

2013-09-01

Knowledge of virus removal in subsurface environments is pivotal for assessing the risk of viral contamination of water resources and developing appropriate protection measures. Columns packed with sand are frequently used to quantify attachment, detachment and inactivation rates of viruses. Since column transport experiments are very laborious, a common alternative is to perform batch experiments where usually one or two measurements are done assuming equilibrium is reached. It is also possible to perform kinetic batch experiments. In that case, however, it is necessary to monitor changes in the concentration with time. This means that kinetic batch experiments will be almost as laborious as column experiments. Moreover, attachment and detachment rate coefficients derived from batch experiments may differ from those determined using column experiments. The aim of this study was to determine the utility of kinetic batch experiments and investigate the effects of different designs of the batch experiments on estimated attachment, detachment and inactivation rate coefficients. The experiments involved various combinations of container size, sand-water ratio, and mixing method (i.e., rolling or tumbling by pivoting the tubes around their horizontal or vertical axes, respectively). Batch experiments were conducted with clean quartz sand, water at pH 7 and ionic strength of 20 mM, and using the bacteriophage PRD1 as a model virus. Values of attachment, detachment and inactivation rate coefficients were found by fitting an analytical solution of the kinetic model equations to the data. Attachment rate coefficients were found to be systematically higher under tumbling than under rolling conditions because of better mixing and more efficient contact of phages with the surfaces of the sand grains. In both mixing methods, more sand in the container yielded higher attachment rate coefficients. A linear increase in the detachment rate coefficient was observed with increased solid-water ratio using tumbling method. Given the differences in the attachment rate coefficients, and assuming the same sticking efficiencies since chemical conditions of the batch and column experiments were the same, our results show that collision efficiencies of batch experiments are not the same as those of column experiments. Upscaling of the attachment rate from batch to column experiments hence requires proper understanding of the mixing conditions. Because batch experiments, in which the kinetics are monitored, are as laborious as column experiments, there seems to be no major advantage in performing batch instead of column experiments.

Design, fabrication, and evaluation of a partially melted ice particle cloud facility

NASA Astrophysics Data System (ADS)

Soltis, Jared T.

High altitude ice crystal clouds created by highly convective storm cells are dangerous to jet transport aircraft because the crystals are ingested into the compressor section, partially melt, accrete, and cause roll back or flame out. Current facilities to test engine particle icing are not ideal for fundamental mixed-phase ice accretion experiments or do not generate frozen droplet clouds under representative conditions. The goal of this research was to develop a novel facility capable of testing fundamental partially melted ice particle icing physics and to collect ice accretion data related to mixed-phase ice accretion. The Penn State Icing Tunnel (PSIT) has been designed and fabricated to conduct partially melted ice particle cloud accretion. The PSIT generated a cloud with air assisted atomizing nozzles. The water droplets cool from the 60psi pressure drop as the water exited the nozzle and fully glaciate while flowing in the -11.0°C tunnel air flow. The glaciated cloud flowed through a duct in the center of the tunnel where hot air was introduced. The temperature of the duct was regulated from 3.3°C to 24°C which melted particle the frozen particle from 0% to 90%. The partially melted particle cloud impinged on a temperature controlled flat plate. Ice accretion data was taken for a range of duct temperature from 3.3°C to 24°C and plate temperature from -4.5°C to 7.0°C. The particle median volumetric diameter was 23mum, the total water content was 4.5 g/m 3, the specific humidity was 1.12g/kg, and the wet bulb temperature ranged from 1.0°C to 7.0°C depending on the duct temperature. The boundaries between ice particle bounce off, ice accretion, and water run off were determined. When the particle were totally frozen and the plate surface was below freezing, the ice particle bounced off as expected. Ice accretion was seen for all percent melts tested, but the plate temperature boundary between water runoff and ice accretion increased from 0°C at 8% melt to 3°C at 90%. There were two types of ice accretion with a transition zone in between. The first type of ice was opaque in color and had a rough surface. This ice occurred roughly from 6.0°C to 12.0°C duct temperatures (8% to 50% melt). The qualitative characteristics of the ice were produced from the low water content in the cloud. The water that was available froze instantly and trapped ice particle. Duct temperatures greater than 17.5°C (80% melt) produced ice that was clear and smooth. The water in the surface did not freeze instantly due to the high water content creating a water film that froze. A mixed-phase cloud dynamics model from NASA Glenn was used to estimate the percent melt of the cloud exiting the duct. There was no way to validate the model by directly measuring the percent melt of the cloud, so single particle melt experiments were conducted and compared to the model. A 0.05g/L solution of rhodamine b was sprayed into a levitator and droplets formed at the nodes of the wave. A 532nm green laser was used to illuminate the dye, and the water emitted orange 593nm light given the luminescent properties of the ink. The emitted light intensity was recorded, and a linear relationship between the light intensity of ice to the light intensity of water was used to determine the percent melt of a droplet. The droplets were frozen with a cold flow of nitrogen gas via a liquid nitrogen heat exchanger. The droplets melted under natural convection when the cold nitrogen was shut off. Fifteen cases were compared with droplet diameters ranging from 324mum to 1112mum, air temperatures from 16°C to 31°C, and relative humidities from 41% to 100%. The average discrepancy between predictions and results for the cases that melted slower than ten seconds was 13% while the cases that melted faster than 10 second had 64% discrepancy between the model and experiment. To explain the discrepancy between the experiment and model, sensitivity studies of the model were conducted. It was seen that the melt time from the model was most sensitive to ambient temperature (1s/°C). It was also seen that the thermistors used in the experiment were accurate to 0.7°C. Transient effects of the rhodamine b caused an overshoot in light intensity, making it difficult to accurately determine the melting stop time. These factors led to the difference in melt time between the model and experiments. A 2.7s difference between model and experiments was deemed to be a successful correlation between predictions and experimental results given the model sensitivity to temperature, the difficulty in measuring temperatures at the position of the droplet, and the transient characteristics of rhodamine b.

Spread of large LNG pools on the sea.

PubMed

Fay, J A

2007-02-20

A review of the standard model of LNG pool spreading on water, comparing it with the model and experiments on oil pool spread from which the LNG model is extrapolated, raises questions about the validity of the former as applied to spills from marine tankers. These questions arise from the difference in fluid density ratios, in the multi-dimensional flow at the pool edge, in the effects of LNG pool boiling at the LNG-water interface, and in the model and experimental initial conditions compared with the inflow conditions from a marine tanker spill. An alternate supercritical flow model is proposed that avoids these difficulties; it predicts significant increase in the maximum pool radius compared with the standard model and is partially corroborated by tests of LNG pool fires on water. Wind driven ocean wave interaction has little effect on either spread model.

Effect of gravity on colloid transport through water-saturated columns packed with glass beads: modeling and experiments.

PubMed

Chrysikopoulos, Constantinos V; Syngouna, Vasiliki I

2014-06-17

The role of gravitational force on colloid transport in water-saturated columns packed with glass beads was investigated. Transport experiments were performed with colloids (clays: kaolinite KGa-1b, montmorillonite STx-1b). The packed columns were placed in various orientations (horizontal, vertical, and diagonal) and a steady flow rate of Q = 1.5 mL/min was applied in both up-flow and down-flow modes. All experiments were conducted under electrostatically unfavorable conditions. The experimental data were fitted with a newly developed, analytical, one-dimensional, colloid transport model. The effect of gravity is incorporated in the mathematical model by combining the interstitial velocity (advection) with the settling velocity (gravity effect). The results revealed that flow direction influences colloid transport in porous media. The rate of particle deposition was shown to be greater for up-flow than for down-flow direction, suggesting that gravity was a significant driving force for colloid deposition.

Toward the Application of the Implicit Particle Filter to Real Data in a Shallow Water Model of the Nearshore Ocean

NASA Astrophysics Data System (ADS)

Miller, R.

2015-12-01

Following the success of the implicit particle filter in twin experiments with a shallow water model of the nearshore environment, the planned next step is application to the intensive Sandy Duck data set, gathered at Duck, NC. Adaptation of the present system to the Sandy Duck data set will require construction and evaluation of error models for both the model and the data, as well as significant modification of the system to allow for the properties of the data set. Successful implementation of the particle filter promises to shed light on the details of the capabilities and limitations of shallow water models of the nearshore ocean relative to more detailed models. Since the shallow water model admits distinct dynamical regimes, reliable parameter estimation will be important. Previous work by other groups give cause for optimism. In this talk I will describe my progress toward implementation of the new system, including problems solved, pitfalls remaining and preliminary results

Solute transport along preferential flow paths in unsaturated fractures

USGS Publications Warehouse

Su, Grace W.; Geller, Jil T.; Pruess, Karsten; Hunt, James R.

2001-01-01

Laboratory experiments were conducted to study solute transport along preferential flow paths in unsaturated, inclined fractures. Qualitative aspects of solute transport were identified in a miscible dye tracer experiment conducted in a transparent replica of a natural granite fracture. Additional experiments were conducted to measure the breakthrough curves of a conservative tracer introduced into an established preferential flow path in two different fracture replicas and a rock‐replica combination. The influence of gravity was investigated by varying fracture inclination. The relationship between the travel times of the solute and the relative influence of gravity was substantially affected by two modes of intermittent flow that occurred: the snapping rivulet and the pulsating blob modes. The measured travel times of the solute were evaluated with three transfer function models: the axial dispersion, the reactors‐in‐series, and the lognormal models. The three models described the solute travel times nearly equally well. A mechanistic model was also formulated to describe transport when the pulsating blob mode occurred which assumed blobs of water containing solute mixed with residual pools of water along the flow path.

Reactive transport modeling of ⁹⁰Sr sorption in reactive sandpacks.

PubMed

Yin, Jun; Jeen, Sung-Wook; Lee, David R; Mayer, K Ulrich

2014-09-15

Strontium-90 ((90)Sr) is one of the most problematic radioactive contaminants in groundwater at nuclear sites. Although (90)Sr is retarded relative to groundwater flow, it is sufficiently mobile and long-lived to require treatment in many hydrogeological settings. A detailed study was performed on the practicality of using granular clinoptilolite as a sandpack around groundwater wells where groundwater is contaminated with (90)Sr and the water table must be lowered. The effectiveness of the reactive sandpack concept and the mechanisms controlling (90)Sr attenuation was investigated by numerical analysis of data obtained from four in situ column experiments. The experiments spanned the range of pore-water velocities that would occur during radial flow through granular clinoptilolite sandpacks. A kinetic sorption model was required to adequately reproduce the experimentally observed (90)Sr behavior. Calibrated first-order kinetic rates were correlated with pore-water velocities. After calibration, three sorption models were used to simulate (90)Sr attenuation for four hypothetical pumping scenarios. Results show that a velocity-dependent kinetic model accurately simulates the observed early breakthrough for high pore-water velocities. The results indicate (1) that reactive sandpacks have good potential for in situ remediation and construction dewatering and (2) that quantitative modeling can aid in the design and application of this novel technique. Copyright © 2014 Elsevier B.V. All rights reserved.

The impact of geoengineering on vegetation in experiment G1 of the GeoMIP

NASA Astrophysics Data System (ADS)

Glienke, Susanne; Irvine, Peter J.; Lawrence, Mark G.

2015-10-01

Solar Radiation Management (SRM) has been proposed as a mean to partly counteract global warming. The Geoengineering Model Intercomparison Project (GeoMIP) has simulated the climate consequences of a number of SRM techniques. Thus far, the effects on vegetation have not yet been thoroughly analyzed. Here the vegetation response to the idealized GeoMIP G1 experiment from eight fully coupled Earth system models (ESMs) is analyzed, in which a reduction of the solar constant counterbalances the radiative effects of quadrupled atmospheric CO2 concentrations (abrupt4 × CO2). For most models and regions, changes in net primary productivity (NPP) are dominated by the increase in CO2, via the CO2 fertilization effect. As SRM will reduce temperatures relative to abrupt4 × CO2, in high latitudes this will offset increases in NPP. In low latitudes, this cooling relative to the abrupt4 × CO2 simulation decreases plant respiration while having little effect on gross primary productivity, thus increasing NPP. In Central America and the Mediterranean, generally dry regions which are expected to experience increased water stress with global warming, NPP is highest in the G1 experiment for all models due to the easing of water limitations from increased water use efficiency at high-CO2 concentrations and the reduced evaporative demand in a geoengineered climate. The largest differences in the vegetation response are between models with and without a nitrogen cycle, with a much smaller CO2 fertilization effect for the former. These results suggest that until key vegetation processes are integrated into ESM predictions, the vegetation response to SRM will remain highly uncertain.

Optimum coagulant forecasting by modeling jar test experiments using ANNs

NASA Astrophysics Data System (ADS)

Haghiri, Sadaf; Daghighi, Amin; Moharramzadeh, Sina

2018-01-01

Currently, the proper utilization of water treatment plants and optimizing their use is of particular importance. Coagulation and flocculation in water treatment are the common ways through which the use of coagulants leads to instability of particles and the formation of larger and heavier particles, resulting in improvement of sedimentation and filtration processes. Determination of the optimum dose of such a coagulant is of particular significance. A high dose, in addition to adding costs, can cause the sediment to remain in the filtrate, a dangerous condition according to the standards, while a sub-adequate dose of coagulants can result in the reducing the required quality and acceptable performance of the coagulation process. Although jar tests are used for testing coagulants, such experiments face many constraints with respect to evaluating the results produced by sudden changes in input water because of their significant costs, long time requirements, and complex relationships among the many factors (turbidity, temperature, pH, alkalinity, etc.) that can influence the efficiency of coagulant and test results. Modeling can be used to overcome these limitations; in this research study, an artificial neural network (ANN) multi-layer perceptron (MLP) with one hidden layer has been used for modeling the jar test to determine the dosage level of used coagulant in water treatment processes. The data contained in this research have been obtained from the drinking water treatment plant located in Ardabil province in Iran. To evaluate the performance of the model, the mean squared error (MSE) and correlation coefficient (R2) parameters have been used. The obtained values are within an acceptable range that demonstrates the high accuracy of the models with respect to the estimation of water-quality characteristics and the optimal dosages of coagulants; so using these models will allow operators to not only reduce costs and time taken to perform experimental jar tests but also to predict a proper dosage for coagulant amounts and to project the quality of the output water under real conditions.

Laboratory and numerical experiments on water and energy fluxes during freezing and thawing in the unsaturated zone

NASA Astrophysics Data System (ADS)

Holländer, Hartmut; Montasir Islam, Md.; Šimunek, Jirka

2017-04-01

Frozen soil has a major effect in many hydrologic processes, and its effects are difficult to predict. A prime example is flood forecasting during spring snowmelt within the Canadian Prairies. One key driver for the extent of flooding is the antecedent soil moisture and the possibility for water to infiltrate into frozen soils. Therefore, these situations are crucial for accurate flood prediction during every spring. The main objective of this study was to evaluate the water flow and heat transport within HYDRUS-1D version 4.16 and with Hansson's model, which is a detailed freezing/thawing module (Hansson et al., 2004), to predict the impact of frozen and partly frozen soil on infiltration. We developed a standardized data set of water flow and heat transport into (partial) frozen soil by laboratory experiments using fine sand. Temperature, soil moisture, and percolated water were observed at different freezing conditions as well as at thawing conditions. Significant variation in soil moisture was found between the top and the bottom of the soil column at the starting of the thawing period. However, with increasing temperature, the lower depth of the soil column showed higher moisture as the soil became enriched with moisture due to the release of heat by soil particles during the thawing cycle. We applied vadose zone modeling using the results from the laboratory experiments. The simulated water content by HYDRUS-1D 4.16 showed large errors compared to the observed data showing by negative Nash-Sutcliffe Efficiency. Hansson's model was not able to predict soil water fluxes due to its unstable behavior (Šimunek et al., 2016). The soil temperature profile simulated using HYDRUS-1D 4.16 was not able to predict the release of latent heat during the phase change of water that was visible in Hansson's model. Hansson's model includes the energy gain/loss due to the phase change in the amount of latent energy stored in the modified heat transport equation. However, in situations when the thermal heat gradient was large, the latent heat was not the key process, and HYDRUS-1D 4.16 was predicting better soil temperatures compared to Hansson's model. The newly developed data showed their usefulness for the evaluation and validation of the numerical models. We claim that these laboratory results will be useful for the validation of numerical models and for developing scientific knowledge to suggest potential code variations or new code development in numerical models. References: Hansson, K., J. Šimunek, M. Mizoguchi, L.-C. Lundin, and M. T. van Genuchten (2004), Water Flow and Heat Transport in Frozen Soil, Vadose Zone J, 3(2), 693-704. Šimunek, J., M. T. van Genuchten, and M. Sejna (2016), Recent developments and applications of the HYDRUS computer software packages, Vadose Zone J, 15(7).

Uranium Hydride Nucleation and Growth Model FY'16 ESC Annual Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hill, Mary Ann; Richards, Andrew Walter; Holby, Edward F.

2016-12-20

Uranium hydride corrosion is of great interest to the nuclear industry. Uranium reacts with water and/or hydrogen to form uranium hydride which adversely affects material performance. Hydride nucleation is influenced by thermal history, mechanical defects, oxide thickness, and chemical defects. Information has been gathered from past hydride experiments to formulate a uranium hydride model to be used in a Canned Subassembly (CSA) lifetime prediction model. This multi-scale computer modeling effort started in FY’13, and the fourth generation model is now complete. Additional high-resolution experiments will be run to further test the model.

Isotope effects accompanying evaporation of water from leaky containers.

PubMed

Rozanski, Kazimierz; Chmura, Lukasz

2008-03-01

Laboratory experiments aimed at quantifying isotope effects associated with partial evaporation of water from leaky containers have been performed under three different settings: (i) evaporation into dry atmosphere, performed in a dynamic mode, (ii) evaporation into dry atmosphere, performed in a static mode, and (iii) evaporation into free laboratory atmosphere. The results demonstrate that evaporative enrichment of water stored in leaky containers can be properly described in the framework of the Craig-Gordon evaporation model. The key parameter controlling the degree of isotope enrichment is the remaining fraction of water in the leaking containers. Other factors such as temperature, relative humidity, or extent of kinetic fractionation play only minor roles. Satisfactory agreement between observed and predicted isotope enrichments for both (18)O and (2)H in experiments for the case of evaporation into dry atmosphere could be obtained only when molecular diffusivity ratios of isotope water molecules as suggested recently by Cappa et al. [J. Geophys. Res., 108, 4525-4535, (2003).] were adopted. However, the observed and modelled isotope enrichments for (2)H and (18)O could be reconciled also for the ratios of molecular diffusivities obtained by Merlivat [J. Chem. Phys., 69, 2864-2871 (1978).], if non-negligible transport resistance in the viscous liquid sub-layer adjacent to the evaporating surface is considered. The evaporation experiments revealed that the loss of mass of water stored in leaky containers in the order of 1%, will lead to an increase of the heavy isotope content in this water by ca. 0.35 and 1.1 per thousand, for delta (18)O and delta (2)H, respectively.

The removal of disinfection by-product precursors from water with ceramic membranes.

PubMed

Harman, B I; Koseoglu, H; Yigit, N O; Sayilgan, E; Beyhan, M; Kitis, M

2010-01-01

The main objective of this work was to investigate the effectiveness of ceramic ultrafiltration (UF) membranes with different pore sizes in removing natural organic matter (NOM) from model solutions and drinking water sources. A lab-scale, cross-flow ceramic membrane test unit was used in all experiments. Two different single-channel tubular ceramic membrane modules were tested with average pore sizes of 4 and 10 nm. The impacts of membrane pore size and pressure on permeate flux and the removals of UV(280 nm) absorbance, specific UV absorbance (SUVA(280 nm)), and dissolved organic carbon (DOC) were determined. Prior to experiments with model solutions and raw waters, clean water flux tests were conducted. UV(280) absorbance reductions ranged between 63 and 83% for all pressures and membranes tested in the raw water. More than 90% of UV(280) absorbance reduction was consistently achieved with both membranes in the model NOM solutions. Such high UV absorbance reductions are advantageous due to the fact that UV absorbing sites of NOM are known to be one of the major precursors to disinfection by-products (DBP) such as trihalomethanes and haloacetic acids. For both UF membranes, the ranges of DOC removals in the raw water and model NOM solutions were 55-73% and 79-91%, respectively. SUVA(280) value of the raw water decreased from 2 to about 1.5 L/mg-m by both membranes. For the model solutions, SUVA(280) values were consistently reduced to < or =1 L/mg-m levels after membrane treatment. As the SUVA(280) value of the NOM source increased, the extent of SUVA(280) reduction and DOC removal by the tested ceramic UF membranes also increased. The results overall indicated that ceramic UF membranes, especially the one with 4 nm average pore size, appear to be effective in removing organic matter and DBP precursors from drinking water sources with relatively high and sustainable permeate flux values.

A diffusion model-free framework with echo time dependence for free-water elimination and brain tissue microstructure characterization.

PubMed

Molina-Romero, Miguel; Gómez, Pedro A; Sperl, Jonathan I; Czisch, Michael; Sämann, Philipp G; Jones, Derek K; Menzel, Marion I; Menze, Bjoern H

2018-03-23

The compartmental nature of brain tissue microstructure is typically studied by diffusion MRI, MR relaxometry or their correlation. Diffusion MRI relies on signal representations or biophysical models, while MR relaxometry and correlation studies are based on regularized inverse Laplace transforms (ILTs). Here we introduce a general framework for characterizing microstructure that does not depend on diffusion modeling and replaces ill-posed ILTs with blind source separation (BSS). This framework yields proton density, relaxation times, volume fractions, and signal disentanglement, allowing for separation of the free-water component. Diffusion experiments repeated for several different echo times, contain entangled diffusion and relaxation compartmental information. These can be disentangled by BSS using a physically constrained nonnegative matrix factorization. Computer simulations, phantom studies, together with repeatability and reproducibility experiments demonstrated that BSS is capable of estimating proton density, compartmental volume fractions and transversal relaxations. In vivo results proved its potential to correct for free-water contamination and to estimate tissue parameters. Formulation of the diffusion-relaxation dependence as a BSS problem introduces a new framework for studying microstructure compartmentalization, and a novel tool for free-water elimination. © 2018 International Society for Magnetic Resonance in Medicine.

Terrestrial Water Mass Load Changes from Gravity Recovery and Climate Experiment (GRACE)

NASA Technical Reports Server (NTRS)

Seo, K.-W.; Wilson, C. R.; Famiglietti, J. S.; Chen, J. L.; Rodell M.

2006-01-01

Recent studies show that data from the Gravity Recovery and Climate Experiment (GRACE) is promising for basin- to global-scale water cycle research. This study provides varied assessments of errors associated with GRACE water storage estimates. Thirteen monthly GRACE gravity solutions from August 2002 to December 2004 are examined, along with synthesized GRACE gravity fields for the same period that incorporate simulated errors. The synthetic GRACE fields are calculated using numerical climate models and GRACE internal error estimates. We consider the influence of measurement noise, spatial leakage error, and atmospheric and ocean dealiasing (AOD) model error as the major contributors to the error budget. Leakage error arises from the limited range of GRACE spherical harmonics not corrupted by noise. AOD model error is due to imperfect correction for atmosphere and ocean mass redistribution applied during GRACE processing. Four methods of forming water storage estimates from GRACE spherical harmonics (four different basin filters) are applied to both GRACE and synthetic data. Two basin filters use Gaussian smoothing, and the other two are dynamic basin filters which use knowledge of geographical locations where water storage variations are expected. Global maps of measurement noise, leakage error, and AOD model errors are estimated for each basin filter. Dynamic basin filters yield the smallest errors and highest signal-to-noise ratio. Within 12 selected basins, GRACE and synthetic data show similar amplitudes of water storage change. Using 53 river basins, covering most of Earth's land surface excluding Antarctica and Greenland, we document how error changes with basin size, latitude, and shape. Leakage error is most affected by basin size and latitude, and AOD model error is most dependent on basin latitude.

Estimating future temperature maxima in lakes across the United States using a surrogate modeling approach

PubMed Central

Zi, Tan; Schmidt, Michelle; Johnson, Thomas E.; Nover, Daniel M.; Clark, Christopher M.

2017-01-01

A warming climate increases thermal inputs to lakes with potential implications for water quality and aquatic ecosystems. In a previous study, we used a dynamic water column temperature and mixing simulation model to simulate chronic (7-day average) maximum temperatures under a range of potential future climate projections at selected sites representative of different U.S. regions. Here, to extend results to lakes where dynamic models have not been developed, we apply a novel machine learning approach that uses Gaussian Process regression to describe the model response surface as a function of simplified lake characteristics (depth, surface area, water clarity) and climate forcing (winter and summer air temperatures and potential evapotranspiration). We use this approach to extrapolate predictions from the simulation model to the statistical sample of U.S. lakes in the National Lakes Assessment (NLA) database. Results provide a national-scale scoping assessment of the potential thermal risk to lake water quality and ecosystems across the U.S. We suggest a small fraction of lakes will experience less risk of summer thermal stress events due to changes in stratification and mixing dynamics, but most will experience increases. The percentage of lakes in the NLA with simulated 7-day average maximum water temperatures in excess of 30°C is projected to increase from less than 2% to approximately 22% by the end of the 21st century, which could significantly reduce the number of lakes that can support cold water fisheries. Site-specific analysis of the full range of factors that influence thermal profiles in individual lakes is needed to develop appropriate adaptation strategies. PMID:29121058

Predicting the scanning branches of hysteretic soil water-retention capacity with use of the method of mathematical modeling

NASA Astrophysics Data System (ADS)

Terleev, V.; Ginevsky, R.; Lazarev, V.; Nikonorov, A.; Togo, I.; Topaj, A.; Moiseev, K.; Abakumov, E.; Melnichuk, A.; Dunaieva, I.

2017-10-01

A mathematical model of the hysteresis of the water-retention capacity of the soil is proposed. The parameters of the model are interpreted within the framework of physical concepts of the structure and capillary properties of soil pores. On the basis of the model, a computer program with an interface that allows for dialogue with the user is developed. The program has some of options: visualization of experimental data; identification of the model parameters with use of measured data by means of an optimizing algorithm; graphical presentation of the hysteresis loop with application of the assigned parameters. Using the program, computational experiments were carried out, which consisted in verifying the identifiability of the model parameters from data on the main branches, and also in testing the ability to predict the scanning branches of the hysteresis loop. For the experiments, literature data on two sandy soils were used. The absence of an “artificial pump effect” is proved. A sufficiently high accuracy of the prediction of the scanning branches of the hysteresis loop has been achieved in comparison with the three models of the precursors. The practical importance of the proposed model and computer program, which is developed on its basis, is to ensure the calculation of precision irrigation rates. The application of such rates in irrigation farming will help to prevent excess moisture from flowing beyond the root layer of the soil and, thus, minimize the unproductive loss of irrigation water and agrochemicals, as well as reduce the risk of groundwater contamination and natural water eutrophication.

BNL severe-accident sequence experiments and analysis program. [PWR; BWR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Greene, G.A.; Ginsberg, T.; Tutu, N.K.

1983-01-01

In the analysis of degraded core accidents, the two major sources of pressure loading on light water reactor containments are: steam generation from core debris-water thermal interactions; and molten core-concrete interactions. Experiments are in progress at BNL in support of analytical model development related to aspects of the above containment loading mechanisms. The work supports development and evaluation of the CORCON (Muir, 1981) and MARCH (Wooton, 1980) computer codes. Progress in the two programs is described.

Modeling the Secondary Drying Stage of Freeze Drying: Development and Validation of an Excel-Based Model.

PubMed

Sahni, Ekneet K; Pikal, Michael J

2017-03-01

Although several mathematical models of primary drying have been developed over the years, with significant impact on the efficiency of process design, models of secondary drying have been confined to highly complex models. The simple-to-use Excel-based model developed here is, in essence, a series of steady state calculations of heat and mass transfer in the 2 halves of the dry layer where drying time is divided into a large number of time steps, where in each time step steady state conditions prevail. Water desorption isotherm and mass transfer coefficient data are required. We use the Excel "Solver" to estimate the parameters that define the mass transfer coefficient by minimizing the deviations in water content between calculation and a calibration drying experiment. This tool allows the user to input the parameters specific to the product, process, container, and equipment. Temporal variations in average moisture contents and product temperatures are outputs and are compared with experiment. We observe good agreement between experiments and calculations, generally well within experimental error, for sucrose at various concentrations, temperatures, and ice nucleation temperatures. We conclude that this model can serve as an important process development tool for process design and manufacturing problem-solving. Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Experimental Insights into Multiphase (H2O-CO2) Fluid-Rock Interactions in Geothermal Systems

NASA Astrophysics Data System (ADS)

Kaszuba, J. P.; Lo Re, C.; Martin, J.; McPherson, B. J.; Moore, J. N.

2012-12-01

Integrated hydrothermal experiments and geochemical modeling elucidate fluid-rock interactions and reaction pathways in both natural and anthropogenic systems, including enhanced geothermal systems (EGS) in which CO2 is introduced as a working fluid. Experiments are conducted in rocker bombs and flexible Au-Ti reaction cells. Individual experiments require one to three months to complete; intensive in-situ fluid/gas sampling gauges reaction progress. Investigation of granitic reservoirs and associated vein minerals are broadly based on the Roosevelt Hot Springs thermal area, Utah, USA. The granite consists of subequal amounts of quartz, perthitic K-feldspar (~25% wt% albite and 75% wt% K-feldspar), and oligoclase (An23), and 4 wt% Fe-rich biotite. Vein minerals include epidote and chlorite (clinochlore). Experiments are conducted at 250°C and 25 to 45 MPa. Each experiment uses mineral powders (75 wt% of rock mass, ground to <45 um) to increase reactivity and also mineral pieces (0.1-0.7 cm in size) to promote petrologic evaluation of mineral reactions. The water (I ≈ 0.1 molal) initially contains millimolal quantities of SiO2, Al, Ca, Mg, K, SO4, and HCO3 and is designed to be saturated with all of the minerals present at the start of each experiment. Excess CO2 is injected to saturate the water and maintain an immiscible supercritical fluid phase. The entire evolutionary path of the natural system is not replicated at laboratory scales. Instead, experiments define a segment of the reaction path and, in combination with geochemical modeling, provide clear trajectories towards equilibrium. Reaction of granite+water yields illite+zeolite; smectite subsequently precipitates in response to CO2 injection. Reaction of granite+epidote+water yields illite+zeolite+smectite; zeolite does not precipitate after CO2 is injected. Water in all experiments become saturated with chalcedony. Carbonate minerals do not precipitate but are predicted as final equilbrium products. Enhanced Geothermal Systems are expected to follow similar reaction pathways and produce metastable minerals during initial development.

Global models underestimate large decadal declining and rising water storage trends relative to GRACE satellite data

PubMed Central

Scanlon, Bridget R.; Zhang, Zizhan; Save, Himanshu; Sun, Alexander Y.; van Beek, Ludovicus P. H.; Wiese, David N.; Reedy, Robert C.; Longuevergne, Laurent; Döll, Petra; Bierkens, Marc F. P.

2018-01-01

Assessing reliability of global models is critical because of increasing reliance on these models to address past and projected future climate and human stresses on global water resources. Here, we evaluate model reliability based on a comprehensive comparison of decadal trends (2002–2014) in land water storage from seven global models (WGHM, PCR-GLOBWB, GLDAS NOAH, MOSAIC, VIC, CLM, and CLSM) to trends from three Gravity Recovery and Climate Experiment (GRACE) satellite solutions in 186 river basins (∼60% of global land area). Medians of modeled basin water storage trends greatly underestimate GRACE-derived large decreasing (≤−0.5 km3/y) and increasing (≥0.5 km3/y) trends. Decreasing trends from GRACE are mostly related to human use (irrigation) and climate variations, whereas increasing trends reflect climate variations. For example, in the Amazon, GRACE estimates a large increasing trend of ∼43 km3/y, whereas most models estimate decreasing trends (−71 to 11 km3/y). Land water storage trends, summed over all basins, are positive for GRACE (∼71–82 km3/y) but negative for models (−450 to −12 km3/y), contributing opposing trends to global mean sea level change. Impacts of climate forcing on decadal land water storage trends exceed those of modeled human intervention by about a factor of 2. The model-GRACE comparison highlights potential areas of future model development, particularly simulated water storage. The inability of models to capture large decadal water storage trends based on GRACE indicates that model projections of climate and human-induced water storage changes may be underestimated. PMID:29358394

Global models underestimate large decadal declining and rising water storage trends relative to GRACE satellite data.

PubMed

Scanlon, Bridget R; Zhang, Zizhan; Save, Himanshu; Sun, Alexander Y; Müller Schmied, Hannes; van Beek, Ludovicus P H; Wiese, David N; Wada, Yoshihide; Long, Di; Reedy, Robert C; Longuevergne, Laurent; Döll, Petra; Bierkens, Marc F P

2018-02-06

Assessing reliability of global models is critical because of increasing reliance on these models to address past and projected future climate and human stresses on global water resources. Here, we evaluate model reliability based on a comprehensive comparison of decadal trends (2002-2014) in land water storage from seven global models (WGHM, PCR-GLOBWB, GLDAS NOAH, MOSAIC, VIC, CLM, and CLSM) to trends from three Gravity Recovery and Climate Experiment (GRACE) satellite solutions in 186 river basins (∼60% of global land area). Medians of modeled basin water storage trends greatly underestimate GRACE-derived large decreasing (≤-0.5 km 3 /y) and increasing (≥0.5 km 3 /y) trends. Decreasing trends from GRACE are mostly related to human use (irrigation) and climate variations, whereas increasing trends reflect climate variations. For example, in the Amazon, GRACE estimates a large increasing trend of ∼43 km 3 /y, whereas most models estimate decreasing trends (-71 to 11 km 3 /y). Land water storage trends, summed over all basins, are positive for GRACE (∼71-82 km 3 /y) but negative for models (-450 to -12 km 3 /y), contributing opposing trends to global mean sea level change. Impacts of climate forcing on decadal land water storage trends exceed those of modeled human intervention by about a factor of 2. The model-GRACE comparison highlights potential areas of future model development, particularly simulated water storage. The inability of models to capture large decadal water storage trends based on GRACE indicates that model projections of climate and human-induced water storage changes may be underestimated. Copyright © 2018 the Author(s). Published by PNAS.

A data assimilation system combining CryoSat-2 data and hydrodynamic river models

NASA Astrophysics Data System (ADS)

Schneider, Raphael; Ridler, Marc-Etienne; Godiksen, Peter Nygaard; Madsen, Henrik; Bauer-Gottwein, Peter

2018-02-01

There are numerous hydrologic studies using satellite altimetry data from repeat-orbit missions such as Envisat or Jason over rivers. This study is one of the first examples for the combination of altimetry from drifting-ground track satellite missions, namely CryoSat-2, with a river model. CryoSat-2 SARIn Level 2 data is used to improve a 1D hydrodynamic model of the Brahmaputra River in South Asia, which is based on the Saint-Venant equations for unsteady flow and set up in the MIKE HYDRO River software. After calibration of discharge and water level the hydrodynamic model can accurately and bias-free represent the spatio-temporal variations of water levels. A data assimilation framework has been developed and linked with the model. It is a flexible framework that can assimilate water level data which are arbitrarily distributed in time and space. The setup has been used to assimilate CryoSat-2 water level observations over the Assam valley for the years 2010-2015, using an Ensemble Transform Kalman Filter (ETKF). Performance improvement in terms of discharge forecasting skill was then evaluated. For experiments with synthetic CryoSat-2 data the continuous ranked probability score (CRPS) was improved by up to 32%, whilst for experiments assimilating real data it could be improved by up to 10%. The developed methods are expected to be transferable to other rivers and altimeter missions. The model setup and calibration is based almost entirely on globally available remote sensing data.

Finite difference model for aquifer simulation in two dimensions with results of numerical experiments

USGS Publications Warehouse

Trescott, Peter C.; Pinder, George Francis; Larson, S.P.

1976-01-01

The model will simulate ground-water flow in an artesian aquifer, a water-table aquifer, or a combined artesian and water-table aquifer. The aquifer may be heterogeneous and anisotropic and have irregular boundaries. The source term in the flow equation may include well discharge, constant recharge, leakage from confining beds in which the effects of storage are considered, and evapotranspiration as a linear function of depth to water. The theoretical development includes presentation of the appropriate flow equations and derivation of the finite-difference approximations (written for a variable grid). The documentation emphasizes the numerical techniques that can be used for solving the simultaneous equations and describes the results of numerical experiments using these techniques. Of the three numerical techniques available in the model, the strongly implicit procedure, in general, requires less computer time and has fewer numerical difficulties than do the iterative alternating direction implicit procedure and line successive overrelaxation (which includes a two-dimensional correction procedure to accelerate convergence). The documentation includes a flow chart, program listing, an example simulation, and sections on designing an aquifer model and requirements for data input. It illustrates how model results can be presented on the line printer and pen plotters with a program that utilizes the graphical display software available from the Geological Survey Computer Center Division. In addition the model includes options for reading input data from a disk and writing intermediate results on a disk.

The Value of GRACE Data in Improving, Assessing and Evaluating Land Surface and Climate Models

NASA Astrophysics Data System (ADS)

Yang, Z.

2011-12-01

I will review how the Gravity Recovery and Climate Experiment (GRACE) satellite measurements have improved land surface models that are developed for weather, climate, and hydrological studies. GRACE-derived terrestrial water storage (TWS) changes have been successfully used to assess and evaluate the improved representations of land-surface hydrological processes such as groundwater-soil moisture interaction, frozen soil and infiltration, and the topographic control on runoff production, as evident in the simulations from the latest Noah-MP, the Community Land Model, and the Community Climate System Model. GRACE data sets have made it possible to estimate key terrestrial water storage components (snow mass, surface water, groundwater or water table depth), biomass, and surface water fluxes (evapotranspiration, solid precipitation, melt of snow/ice). Many of the examples will draw from my Land, Environment and Atmosphere Dynamics group's work on land surface model developments, snow mass retrieval, and multi-sensor snow data assimilation using the ensemble Karman filter and the ensemble Karman smoother. Finally, I will briefly outline some future directions in using GRACE in land surface modeling.

Comparison of the magnitude and phase of the reflection coefficient from a smooth water/sand interface with elastic and poroelastic models

NASA Astrophysics Data System (ADS)

Isakson, Marcia; Camin, H. John; Canepa, Gaetano

2005-04-01

The reflection coefficient from a sand/water interface is an important parameter in modeling the acoustics of littoral environments. Many models have been advanced to describe the influence of the sediment parameters and interface roughness parameters on the reflection coefficient. In this study, the magnitude and phase of the reflection coefficient from 30 to 160 kHz is measured in a bistatic experiment on a smoothed water/sand interface at grazing angles from 5 to 75 degrees. The measured complex reflection coefficient is compared with the fluid model, the elastic model and poro-elastic models. Effects of rough surface scattering are investigated using the Bottom Response from Inhomogeneities and Surface using Small Slope Approximation (BoRIS-SSA). Spherical wave effects are modeled using plane wave decomposition. Models are considered for their ability to predict the measured results using realistic parameters. [Work supported by ONR, Ocean Acoustics.

Aquifer storage and recovery: recent hydrogeological advances and system performance.

PubMed

Maliva, Robert G; Guo, Weixing; Missimer, Thomas M

2006-12-01

Aquifer storage and recovery (ASR) is part of the solution to the global problem of managing water resources to meet existing and future freshwater demands. However, the metaphoric "ASR bubble" has been burst with the realization that ASR systems are more physically and chemically complex than the general conceptualization. Aquifer heterogeneity and fluid-rock interactions can greatly affect ASR system performance. The results of modeling studies and field experiences indicate that more sophisticated data collection and solute-transport modeling are required to predict how stored water will migrate in heterogeneous aquifers and how fluid-rock interactions will affect the quality of stored water. It has been well-demonstrated, by historic experience, that ASR systems can provide very large volumes of storage at a lesser cost than other options. The challenges moving forward are to improve the success rate of ASR systems, optimize system performance, and set expectations appropriately.

Calibration of a turbidity meter for making estimates of total suspended solids concentrations and beam attenuation coefficients in field experiments

NASA Technical Reports Server (NTRS)

Usry, J. W.; Whitlock, C. H.

1981-01-01

Management of water resources such as a reservoir requires using analytical models which describe such parameters as the suspended sediment field. To select or develop an appropriate model requires making many measurements to describe the distribution of this parameter in the water column. One potential method for making those measurements expeditiously is to measure light transmission or turbidity and relate that parameter to total suspended solids concentrations. An instrument which may be used for this purpose was calibrated by generating curves of transmission measurements plotted against measured values of total suspended solids concentrations and beam attenuation coefficients. Results of these experiments indicate that field measurements made with this instrument using curves generated in this study should correlate with total suspended solids concentrations and beam attenuation coefficients in the water column within 20 percent.

A deformable surface model for real-time water drop animation.

PubMed

Zhang, Yizhong; Wang, Huamin; Wang, Shuai; Tong, Yiying; Zhou, Kun

2012-08-01

A water drop behaves differently from a large water body because of its strong viscosity and surface tension under the small scale. Surface tension causes the motion of a water drop to be largely determined by its boundary surface. Meanwhile, viscosity makes the interior of a water drop less relevant to its motion, as the smooth velocity field can be well approximated by an interpolation of the velocity on the boundary. Consequently, we propose a fast deformable surface model to realistically animate water drops and their flowing behaviors on solid surfaces. Our system efficiently simulates water drop motions in a Lagrangian fashion, by reducing 3D fluid dynamics over the whole liquid volume to a deformable surface model. In each time step, the model uses an implicit mean curvature flow operator to produce surface tension effects, a contact angle operator to change droplet shapes on solid surfaces, and a set of mesh connectivity updates to handle topological changes and improve mesh quality over time. Our numerical experiments demonstrate a variety of physically plausible water drop phenomena at a real-time rate, including capillary waves when water drops collide, pinch-off of water jets, and droplets flowing over solid materials. The whole system performs orders-of-magnitude faster than existing simulation approaches that generate comparable water drop effects.

Communication: Modeling of concentration dependent water diffusivity in ionic solutions: Role of intermolecular charge transfer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yao, Yi; Berkowitz, Max L., E-mail: maxb@unc.edu, E-mail: ykanai@unc.edu; Kanai, Yosuke, E-mail: maxb@unc.edu, E-mail: ykanai@unc.edu

2015-12-28

The translational diffusivity of water in solutions of alkali halide salts depends on the identity of ions, exhibiting dramatically different behavior even in solutions of similar salts of NaCl and KCl. The water diffusion coefficient decreases as the salt concentration increases in NaCl. Yet, in KCl solution, it slightly increases and remains above bulk value as salt concentration increases. Previous classical molecular dynamics simulations have failed to describe this important behavior even when polarizable models were used. Here, we show that inclusion of dynamical charge transfer among water molecules produces results in a quantitative agreement with experiments. Our results indicatemore » that the concentration-dependent diffusivity reflects the importance of many-body effects among the water molecules in aqueous ionic solutions. Comparison with quantum mechanical calculations shows that a heterogeneous and extended distribution of charges on water molecules around the ions due to ion-water and also water-water charge transfer plays a very important role in controlling water diffusivity. Explicit inclusion of the charge transfer allows us to model accurately the difference in the concentration-dependent water diffusivity between Na{sup +} and K{sup +} ions in simulations, and it is likely to impact modeling of a wide range of systems for medical and technological applications.« less

Improved regional water management utilizing climate forecasts: An interbasin transfer model with a risk management framework

NASA Astrophysics Data System (ADS)

Li, Weihua; Sankarasubramanian, A.; Ranjithan, R. S.; Brill, E. D.

2014-08-01

Regional water supply systems undergo surplus and deficit conditions due to differences in inflow characteristics as well as due to their seasonal demand patterns. This study proposes a framework for regional water management by proposing an interbasin transfer (IBT) model that uses climate-information-based inflow forecast for minimizing the deviations from the end-of-season target storage across the participating pools. Using the ensemble streamflow forecast, the IBT water allocation model was applied for two reservoir systems in the North Carolina Triangle Area. Results show that interbasin transfers initiated by the ensemble streamflow forecast could potentially improve the overall water supply reliability as the demand continues to grow in the Triangle Area. To further understand the utility of climate forecasts in facilitating IBT under different spatial correlation structures between inflows and between the initial storages of the two systems, a synthetic experiment was designed to evaluate the framework under inflow forecast having different skills. Findings from the synthetic study can be summarized as follows: (a) inflow forecasts combined with the proposed IBT optimization model provide improved allocation in comparison to the allocations obtained under the no-transfer scenario as well as under transfers obtained with climatology; (b) spatial correlations between inflows and between initial storages among participating reservoirs could also influence the potential benefits that could be achieved through IBT; (c) IBT is particularly beneficial for systems that experience low correlations between inflows or between initial storages or on both attributes of the regional water supply system. Thus, if both infrastructure and permitting structures exist for promoting interbasin transfers, season-ahead inflow forecasts could provide added benefits in forecasting surplus/deficit conditions among the participating pools in the regional water supply system.

Improved Regional Water Management Utilizing Climate Forecasts: An Inter-basin Transfer Model with a Risk Management Framework

NASA Astrophysics Data System (ADS)

Li, W.; Arumugam, S.; Ranjithan, R. S.; Brill, E. D., Jr.

2014-12-01

Regional water supply systems undergo surplus and deficit conditions due to differences in inflow characteristics as well as due to their seasonal demand patterns. This study presents a framework for regional water management by proposing an Inter-Basin Transfer (IBT) model that uses climate-information-based inflow forecast for minimizing the deviations from the end- of-season target storage across the participating reservoirs. Using the ensemble streamflow forecast, the IBT water allocation model was applied for two reservoir systems in the North Carolina Triangle area. Results show that inter-basin transfers initiated by the ensemble streamflow forecast could potentially improve the overall water supply reliability as the demand continues to grow in the Triangle Area. To further understand the utility of climate forecasts in facilitating IBT under different spatial correlation structures between inflows and between the initial storages of the two systems, a synthetic experiment was designed to evaluate the framework under inflow forecast having different skills. Findings from the synthetic study can be summarized as follows: (a) Inflow forecasts combined with the proposed IBT optimization model provide improved allocation in comparison to the allocations obtained under the no- transfer scenario as well as under transfers obtained with climatology; (b) Spatial correlations between inflows and between initial storages among participating reservoirs could also influence the potential benefits that could be achieved through IBT; (c) IBT is particularly beneficial for systems that experience low correlations between inflows or between initial storages or on both attributes of the regional water supply system. Thus, if both infrastructure and permitting structures exist for promoting inter-basin transfers, season-ahead inflow forecasts could provide added benefits in forecasting surplus/deficit conditions among the participating reservoirs in the regional water supply system.

Karst medium characterization and simulation of groundwater flow in Lijiang Riversed, China

NASA Astrophysics Data System (ADS)

Hu, B. X.

2015-12-01

It is important to study water and carbon cycle processes for water resource management, pollution prevention and global warming influence on southwest karst region of China. Lijiang river basin is selected as our study region. Interdisciplinary field and laboratory experiments with various technologies are conducted to characterize the karst aquifers in detail. Key processes in the karst water cycle and carbon cycle are determined. Based on the MODFLOW-CFP model, new watershed flow and carbon cycle models are developed coupled subsurface and surface water flow models, flow and chemical/biological models. Our study is focused on the karst springshed in Mao village. The mechanisms coupling carbon cycle and water cycle are explored. Parallel computing technology is used to construct the numerical model for the carbon cycle and water cycle in the small scale watershed, which are calibrated and verified by field observations. The developed coupling model for the small scale watershed is extended to a large scale watershed considering the scale effect of model parameters and proper model structure simplification. The large scale watershed model is used to study water cycle and carbon cycle in Lijiang rivershed, and to calculate the carbon flux and carbon sinks in the Lijiang river basin. The study results provide scientific methods for water resources management and environmental protection in southwest karst region corresponding to global climate change. This study could provide basic theory and simulation method for geological carbon sequestration in China karst region.

Simulation of groundwater flow and evaluation of carbon sink in Lijiang Rivershed, China

NASA Astrophysics Data System (ADS)

Hu, Bill X.; Cao, Jianhua; Tong, Juxiu; Gao, Bing

2016-04-01

It is important to study water and carbon cycle processes for water resource management, pollution prevention and global warming influence on southwest karst region of China. Lijiang river basin is selected as our study region. Interdisciplinary field and laboratory experiments with various technologies are conducted to characterize the karst aquifers in detail. Key processes in the karst water cycle and carbon cycle are determined. Based on the MODFLOW-CFP model, new watershed flow and carbon cycle models are developed coupled subsurface and surface water flow models, flow and chemical/biological models. Our study is focused on the karst springshed in Mao village. The mechanisms coupling carbon cycle and water cycle are explored. Parallel computing technology is used to construct the numerical model for the carbon cycle and water cycle in the small scale watershed, which are calibrated and verified by field observations. The developed coupling model for the small scale watershed is extended to a large scale watershed considering the scale effect of model parameters and proper model structure simplification. The large scale watershed model is used to study water cycle and carbon cycle in Lijiang rivershed, and to calculate the carbon flux and carbon sinks in the Lijiang river basin. The study results provide scientific methods for water resources management and environmental protection in southwest karst region corresponding to global climate change. This study could provide basic theory and simulation method for geological carbon sequestration in China karst region.

Global Change And Water Availability And Quality: Challenges Ahead

NASA Astrophysics Data System (ADS)

Larsen, M. C.; Ryker, S. J.

2012-12-01

The United States is in the midst of a continental-scale, multi-year water-resources experiment, in which society has not defined testable hypotheses or set the duration and scope of the experiment. What are we doing? We are expanding population at two to three times the national growth rate in our most water-scarce states, in the southwest, where water stress is already great and modeling predicts decreased streamflow by the middle of this century. We are expanding irrigated agriculture from the west into the east, particularly to the southeastern states, where increased competition for ground and surface water has urban, agricultural, and environmental interests at odds, and increasingly, in court. We are expanding our consumption of pharmaceutical and personal care products to historic high levels and disposing of them in surface and groundwater, through sewage treatment plants and individual septic systems that were not designed to treat them. These and other examples of our national-scale experiment are likely to continue well into the 21st century. This experiment and related challenges will continue and likely intensify as non-climatic and climatic factors, such as predicted rising temperature and changes in the distribution of precipitation in time and space, continue to develop.

Development of a Scale-up Tool for Pervaporation Processes

PubMed Central

Thiess, Holger; Strube, Jochen

2018-01-01

In this study, an engineering tool for the design and optimization of pervaporation processes is developed based on physico-chemical modelling coupled with laboratory/mini-plant experiments. The model incorporates the solution-diffusion-mechanism, polarization effects (concentration and temperature), axial dispersion, pressure drop and the temperature drop in the feed channel due to vaporization of the permeating components. The permeance, being the key model parameter, was determined via dehydration experiments on a mini-plant scale for the binary mixtures ethanol/water and ethyl acetate/water. A second set of experimental data was utilized for the validation of the model for two chemical systems. The industrially relevant ternary mixture, ethanol/ethyl acetate/water, was investigated close to its azeotropic point and compared to a simulation conducted with the determined binary permeance data. Experimental and simulation data proved to agree very well for the investigated process conditions. In order to test the scalability of the developed engineering tool, large-scale data from an industrial pervaporation plant used for the dehydration of ethanol was compared to a process simulation conducted with the validated physico-chemical model. Since the membranes employed in both mini-plant and industrial scale were of the same type, the permeance data could be transferred. The comparison of the measured and simulated data proved the scalability of the derived model. PMID:29342956

Development of a Screening Model for Design and Costing of an Innovative Tailored Granular Activated Carbon Technology to Treat Perchlorate-Contaminated Water

DTIC Science & Technology

2007-03-01

column experiments were used to obtain model parameters . Cost data used in the model were based on conventional GAC installations, as modified to...43 Calculation of Parameters ...66 Determination of Parameter Values

Project Physics Handbook 5, Models of the Atom.

ERIC Educational Resources Information Center

Harvard Univ., Cambridge, MA. Harvard Project Physics.

Five experiments and 19 activities are presented in this Unit 5 handbook. The experiments are related to electrolysis, charge-to-mass ratio, elementary charge determination, photoelectric effects, and spectroscopic analyses. The activities are concerned with Dalton's theory, water electrolysis, periodic tables, single-electron plating, cloud…

Model-experiment synthesis at two FACE sites in the southeastern US. Forest ecosystem responses to elevated CO[2]. (Invited)

NASA Astrophysics Data System (ADS)

Walker, A. P.; Zaehle, S.; De Kauwe, M. G.; Medlyn, B. E.; Dietze, M.; Hickler, T.; Iversen, C. M.; Jain, A. K.; Luo, Y.; McCarthy, H. R.; Parton, W. J.; Prentice, C.; Thornton, P. E.; Wang, S.; Wang, Y.; Warlind, D.; Warren, J.; Weng, E.; Hanson, P. J.; Oren, R.; Norby, R. J.

2013-12-01

Ecosystem observations from two long-term Free-Air CO[2] Enrichment (FACE) experiments (Duke forest and Oak Ridge forest) were used to evaluate the assumptions of 11 terrestrial ecosystem models and the consequences of those assumptions for the responses of ecosystem water, carbon (C) and nitrogen (N) fluxes to elevated CO[2] (eCO[2]). Nitrogen dynamics were the main constraint on simulated productivity responses to eCO[2]. At Oak Ridge some models reproduced the declining response of C and N fluxes, while at Duke none of the models were able to maintain the observed sustained responses. C and N cycles are coupled through a number of complex interactions, which causes uncertainty in model simulations in multiple ways. Nonetheless, the major difference between models and experiments was a larger than observed increase in N-use efficiency and lower than observed response of N uptake. The results indicate that at Duke there were mechanisms by which trees accessed additional N in response to eCO[2] that were not represented in the ecosystem models, and which did not operate with the same efficiency at Oak Ridge. Sequestration of the additional productivity under eCO[2] into forest biomass depended largely on C allocation. Allocation assumptions were classified into three main categories--fixed partitioning coefficients, functional relationships and a partial (leaf allocation only) optimisation. The assumption which best constrained model results was a functional relationship between leaf area and sapwood area (pipe-model) and increased root allocation when nitrogen or water were limiting. Both, productivity and allocation responses to eCO[2] determined the ecosystem-level response of LAI, which together with the response of stomatal conductance (and hence water-use efficiency; WUE) determined the ecosystem response of transpiration. Differences in the WUE response across models were related to the representation of the relationship of stomatal conductance to CO[2] and the relative importance of the combined boundary and aerodynamic resistances in the total resistance to leaf-atmosphere water transport.

Simulation of Stomatal Conductance and Water Use Efficiency of Tomato Leaves Exposed to Different Irrigation Regimes and Air CO2 Concentrations by a Modified "Ball-Berry" Model.

PubMed

Wei, Zhenhua; Du, Taisheng; Li, Xiangnan; Fang, Liang; Liu, Fulai

2018-01-01

Stomatal conductance ( g s ) and water use efficiency ( WUE ) of tomato leaves exposed to different irrigation regimes and at ambient CO 2 ( a [CO 2 ], 400 ppm) and elevated CO 2 ( e [CO 2 ], 800 ppm) environments were simulated using the "Ball-Berry" model (BB-model). Data obtained from a preliminary experiment (Exp. I) was used for model parameterization, where measurements of leaf gas exchange of potted tomatoes were done during progressive soil drying for 5 days. The measured photosynthetic rate ( P n ) was used as an input for the model. Considering the effect of soil water deficits on g s , an equation modifying the slope ( m ) based on the mean soil water potential (Ψ s ) in the whole root zone was introduced. Compared to the original BB-model, the modified model showed greater predictability for both g s and WUE of tomato leaves at each [CO 2 ] growth environment. The models were further validated with data obtained from an independent experiment (Exp. II) where plants were subjected to three irrigation regimes: full irrigation (FI), deficit irrigation (DI), and alternative partial root-zone irrigation (PRI) for 40 days at both a [CO 2 ] and e [CO 2 ] environment. The simulation results indicated that g s was independently acclimated to e [CO 2 ] from P n . The modified BB-model performed better in estimating g s and WUE , especially for PRI strategy at both [CO 2 ] environments. A greater WUE could be seen in plants grown under e [CO 2 ] associated with PRI regime. Conclusively, the modified BB-model was capable of predicting g s and WUE of tomato leaves in various irrigation regimes at both a [CO 2 ] and e [CO 2 ] environments. This study could provide valuable information for better predicting plant WUE adapted to the future water-limited and CO 2 enriched environment.

Significant impacts of irrigation water sources and methods on modeling irrigation effects in the ACME Land Model

DOE PAGES

Leng, Guoyong; Leung, L. Ruby; Huang, Maoyi

2017-06-20

An irrigation module that considers both irrigation water sources and irrigation methods has been incorporated into the ACME Land Model (ALM). Global numerical experiments were conducted to evaluate the impacts of irrigation water sources and irrigation methods on the simulated irrigation effects. All simulations shared the same irrigation soil moisture target constrained by a global census dataset of irrigation amounts. Irrigation has large impacts on terrestrial water balances especially in regions with extensive irrigation. Such effects depend on the irrigation water sources: surface-water-fed irrigation leads to decreases in runoff and water table depth, while groundwater-fed irrigation increases water table depth,more » with positive or negative effects on runoff depending on the pumping intensity. Irrigation effects also depend significantly on the irrigation methods. Flood irrigation applies water in large volumes within short durations, resulting in much larger impacts on runoff and water table depth than drip and sprinkler irrigations. Differentiating the irrigation water sources and methods is important not only for representing the distinct pathways of how irrigation influences the terrestrial water balances, but also for estimating irrigation water use efficiency. Specifically, groundwater pumping has lower irrigation water use efficiency due to enhanced recharge rates. Different irrigation methods also affect water use efficiency, with drip irrigation the most efficient followed by sprinkler and flood irrigation. Furthermore, our results highlight the importance of explicitly accounting for irrigation sources and irrigation methods, which are the least understood and constrained aspects in modeling irrigation water demand, water scarcity and irrigation effects in Earth System Models.« less

Significant impacts of irrigation water sources and methods on modeling irrigation effects in the ACME Land Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leng, Guoyong; Leung, L. Ruby; Huang, Maoyi

An irrigation module that considers both irrigation water sources and irrigation methods has been incorporated into the ACME Land Model (ALM). Global numerical experiments were conducted to evaluate the impacts of irrigation water sources and irrigation methods on the simulated irrigation effects. All simulations shared the same irrigation soil moisture target constrained by a global census dataset of irrigation amounts. Irrigation has large impacts on terrestrial water balances especially in regions with extensive irrigation. Such effects depend on the irrigation water sources: surface-water-fed irrigation leads to decreases in runoff and water table depth, while groundwater-fed irrigation increases water table depth,more » with positive or negative effects on runoff depending on the pumping intensity. Irrigation effects also depend significantly on the irrigation methods. Flood irrigation applies water in large volumes within short durations, resulting in much larger impacts on runoff and water table depth than drip and sprinkler irrigations. Differentiating the irrigation water sources and methods is important not only for representing the distinct pathways of how irrigation influences the terrestrial water balances, but also for estimating irrigation water use efficiency. Specifically, groundwater pumping has lower irrigation water use efficiency due to enhanced recharge rates. Different irrigation methods also affect water use efficiency, with drip irrigation the most efficient followed by sprinkler and flood irrigation. Furthermore, our results highlight the importance of explicitly accounting for irrigation sources and irrigation methods, which are the least understood and constrained aspects in modeling irrigation water demand, water scarcity and irrigation effects in Earth System Models.« less

Deep Space Network Radiometric Remote Sensing Program

NASA Technical Reports Server (NTRS)

Walter, Steven J.

1994-01-01

Planetary spacecraft are viewed through a troposphere that absorbs and delays radio signals propagating through it. Tropospheric water, in the form of vapor, cloud liquid, and precipitation, emits radio noise which limits satellite telemetry communication link performance. Even at X-band, rain storms have severely affected several satellite experiments including a planetary encounter. The problem will worsen with DSN implementation of Ka-band because communication link budgets will be dominated by tropospheric conditions. Troposphere-induced propagation delays currently limit VLBI accuracy and are significant sources of error for Doppler tracking. Additionally, the success of radio science programs such as satellite gravity wave experiments and atmospheric occultation experiments depends on minimizing the effect of water vapor-induced propagation delays. In order to overcome limitations imposed by the troposphere, the Deep Space Network has supported a program of radiometric remote sensing. Currently, water vapor radiometers (WVRs) and microwave temperature profilers (MTPs) support many aspects of the Deep Space Network operations and research and development programs. Their capability to sense atmospheric water, microwave sky brightness, and atmospheric temperature is critical to development of Ka-band telemetry systems, communication link models, VLBI, satellite gravity wave experiments, and radio science missions. During 1993, WVRs provided data for propagation model development, supported planetary missions, and demonstrated advanced tracking capability. Collection of atmospheric statistics is necessary to model and predict performance of Ka-band telemetry links, antenna arrays, and radio science experiments. Since the spectrum of weather variations has power at very long time scales, atmospheric measurements have been requested for periods ranging from one year to a decade at each DSN site. The resulting database would provide reliable statistics on daily, monthly, and seasonal variations. Only long-term monitoring will prevent biases from being introduced by an exceptionally wet or dry year. Support for planetary missions included tropospheric calibration for the recent Mars Observer gravity wave experiments and Ka-band link experiment (KaBLE). Additionally, several proposed radio science experiments such as profiling planetary atmospheres using satellite occultations and Ka-band gravitational wave searches require advanced radiometer technology development. Finally, there has been a consistent advanced technology program to advance satellite navigational and tracking capabilities. This year that included an experiment with radiometer based tropospheric calibration for a series of VLBI catalog measurements.

Charge Equilibration Force Fields for Lipid Environments: Applications to Fully Hydrated DPPC Bilayers and DMPC-Embedded Gramicidin A

PubMed Central

Davis, Joseph E.; Patel, Sandeep

2009-01-01

Polarizable force fields for lipid and solvent environments are used for molecular dynamics simulations of a fully hydrated dipalmitoylphosphatidylcholine (DPPC) bilayer and gramicidin A (gA) dimer embedded in a dimyristoylphosphatidylcholine (DMPC) bilayer. The lipid bilayer is modelled using the CHARMM charge equilibration (CHEQ) polarizable force field for lipids and the TIP4P-FQ force field to represent solvent. For the DPPC bilayer system, results are compared to the same system simulated using the nonpolarizable CHARMM27r (C27r) force field and TIP3P water. Calculated atomic and electron density profiles, headgroup orientations as measured by the phosphorus-nitrogen vector orientation, and deuterium order parameters are found to be consistent with previous simulations and with experiment. The CHEQ model exhibits greater water penetration into the bilayer interior, as demonstrated by the potential of mean force calculated from the water density profile. This is a result of the variation of the water molecular dipole from 2.55 D in the bulk to 1.88 D in the interior. We discuss this finding in the context of previous studies (both simulation and experiment) that have investigated the extent of penetration of water into DPPC bilayers. We also discuss the effects of including explicit polarization on the water dipole moment variation as a function of distance from the bilayer. We show distributions of atomic charges over the course of the simulation, since the CHEQ model allows the charges to fluctuate. We have calculated the interfacial dipole potential, which the CHEQ model predicts to be 0.95 V compared to 0.86 V as predicted by the C27r model. We also discuss dielectric permittivity profiles and the differences arising between the two models. We obtain bulk values of 72.77 for the CHEQ model (TIP4P-FQ water) and 91.22 for C27r (TIP3P), and values approaching unity in the membrane interior. Finally, we present results of simulations of gA embedded in a DMPC bilayer using the CHEQ model and discuss structural properties. PMID:19526999

A 'first principles' potential energy surface for liquid water from VRT spectroscopy of water clusters.

PubMed

Goldman, Nir; Leforestier, Claude; Saykally, R J

2005-02-15

We present results of gas phase cluster and liquid water simulations from the recently determined VRT(ASP-W)III water dimer potential energy surface (the third fitting of the Anisotropic Site Potential with Woermer dispersion to vibration-rotation-tunnelling data). VRT(ASP-W)III is shown to not only be a model of high 'spectroscopic' accuracy for the water dimer, but also makes accurate predictions of vibrational ground-state properties for clusters up through the hexamer. Results of ambient liquid water simulations from VRT(ASP-W)III are compared with those from ab initio molecular dynamics, other potentials of 'spectroscopic' accuracy and with experiment. The results herein represent the first time to the authors' knowledge that a 'spectroscopic' potential surface is able to correctly model condensed phase properties of water.

Probing the triplet correlation function in liquid water by experiments and molecular simulations.

PubMed

Dhabal, Debdas; Wikfeldt, Kjartan Thor; Skinner, Lawrie B; Chakravarty, Charusita; Kashyap, Hemant K

2017-01-25

Despite very significant developments in scattering experiments like X-ray and neutron diffraction, it has been challenging to elucidate the nature of tetrahedral molecular configurations in liquid water. A key question is whether the pair correlation functions, which can be obtained from scattering experiments, are sufficient to describe the tetrahedral ordering of water molecules. In our previous study (Dhabal et al., J. Chem. Phys., 2014, 141, 174504), using data-sets generated from reverse Monte Carlo and molecular dynamics simulations, we showed that the triplet correlation functions contain important information on the tetrahedrality of water in the liquid state. In the present study, X-ray scattering experiments and molecular dynamics (MD) simulations are used to link the isothermal pressure derivative of the structure factor with the triplet correlation functions for water. Triplet functions are determined for water up to 3.3 kbar at 298 K to display the effect of pressure on the water structure. The results suggest that triplet functions (H[combining tilde](q)) obtained using a rigid-body TIP4P/2005 water model are consistent with the experimental results. The triplet functions obtained in experiment as well as in simulations evince that in the case of tetrahedral liquids, exertion of higher pressure leads to a better agreement with the Kirkwood superposition approximation (KSA). We further validate this observation using the triplet correlation functions (g (3) (r,s,t)) calculated directly from simulation trajectory, revealing that both H[combining tilde](q) in q-space and g (3) (r,s,t) in real-space contain similar information on the tetrahedrality of liquids. This study demonstrates that the structure factor, even though it has only pair correlation information of the liquid structure, can shed light on three-body correlations in liquid water through its isothermal pressure derivative term.

Resource Characterization | Water Power | NREL

Science.gov Websites

characterization and assessment, NREL has extended its capabilities to the field of water power. NREL's team of , modeling, data analysis, and Geographic Information Systems. Many years of experience in wind assessment have enabled NREL to develop the skills and methodologies to evaluate the development potential of many

Hydrogen and water reactor safety: proceedings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1982-01-01

Separate abstracts were prepared for papers presented in the following areas of interest: 1) hydrogen research programs; 2) hydrogen behavior during light water reactor accidents; 3) combustible gas generation; 4) hydrogen transport and mixing; 5) combustion modeling and experiments; 6) accelerated flames and detonations; 7) combustion mitigation and control; and 8) equipment survivability.

Calibration of the R/V Marcus G. Langseth Seismic Array in shallow Cascadia waters using the Multi-Channel Streamer

NASA Astrophysics Data System (ADS)

Crone, T. J.; Tolstoy, M.; Carton, H. D.

2013-12-01

In the summer of 2012, two multi-channel seismic (MCS) experiments, Cascadia Open-Access Seismic Transects (COAST) and Ridge2Trench, were conducted in the offshore Cascadia region. An area of growing environmental concern with active source seismic experiments is the potential impact of the received sound on marine mammals, but data relating to this issue is limited. For these surveys sound level 'mitigation radii' are established for the protection of marine mammals, based on direct arrival modeling and previous calibration experiments. Propagation of sound from seismic arrays can be accurately modeled in deep-water environments, but in shallow and sloped environments the complexity of local geology and bathymetry can make it difficult to predict sound levels as a function of distance from the source array. One potential solution to this problem is to measure the received levels in real-time using the ship's streamer (Diebold et al., 2010), which would allow the dynamic determination of suitable mitigation radii. We analyzed R/V Langseth streamer data collected on the shelf and slope off the Washington coast during the COAST experiment to measure received levels in situ up to 8 km away from the ship. Our analysis shows that water depth and bathymetric features can affect received levels in shallow water environments. The establishment of dynamic mitigation radii based on local conditions may help maximize the safety of marine mammals while also maximizing the ability of scientists to conduct seismic research. With increasing scientific and societal focus on subduction zone environments, a better understanding of shallow water sound propagation is essential for allowing seismic exploration of these hazardous environments to continue. Diebold, J. M., M. Tolstoy, L. Doermann, S. Nooner, S. Webb, and T. J. Crone (2010) R/V Marcus G. Langseth Seismic Source: Modeling and Calibration. Geochemistry, Geophysics, Geosystems, 11, Q12012, doi:10.1029/2010GC003216.

A modeling study of irrigation effects on global surface water and groundwater resources under a changing climate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leng, Guoyong; Huang, Maoyi; Tang, Qiuhong

In this paper, the effects of irrigation on global surface water (SW) and groundwater (GW) resources are investigated by performing simulations using Community Land Model 4.0 (CLM4) at 0.5-degree resolution driven by downscaled/bias-corrected historical simulations and future projections from five General Circulation Models (GCMs) for 1950-2099. For each climate scenario, three sets of numerical experiments were configured: (1) a control experiment (CTRL) in which all crops are assumed to be rainfed; (2) an irrigation experiment (IRRIG) in which the irrigation module using only SW for irrigation is activated; and (3) a groundwater pumping experiment (PUMP) in which a groundwater pumpingmore » scheme coupled with the irrigation module is activated for conjunctive use of SW and GW for irrigation. The parameters associated with irrigation and groundwater pumping are calibrated based on a global inventory of census-based SW and GW use compiled by the Food and Agricultural Organization (FAO). Our results suggest that irrigation could lead to two major opposing effects: SW depletion/GW accumulation in regions with irrigation primarily fed by SW, and SW accumulation/GW depletion in regions with irrigation fed primarily by GW. Furthermore, irrigation depending primarily on SW tends to have larger impacts on low-flow than high-flow conditions, suggesting the potential to increase vulnerability to drought. By the end of the 21st century (2070-2099), climate change significantly increases (relative to 1971-2000) irrigation water demand across the world. Combined with the increased temporal-spatial variability of water supply, this may lead to severe issues of local water scarcity for irrigation. Regionally, irrigation has the potential to aggravate/alleviate climate-induced changes of SW/GW although such effects are negligible when averaged globally. Our results emphasize the importance of accounting for irrigation effects and irrigation sources in regional climate change impact assessment.« less

A modeling study of irrigation effects on global surface water and groundwater resources under a changing climate

DOE PAGES

Leng, Guoyong; Huang, Maoyi; Tang, Qiuhong; ...

2015-08-25

In this paper, the effects of irrigation on global surface water (SW) and groundwater (GW) resources are investigated by performing simulations using Community Land Model 4.0 (CLM4) at 0.5-degree resolution driven by downscaled/bias-corrected historical simulations and future projections from five General Circulation Models (GCMs) for 1950-2099. For each climate scenario, three sets of numerical experiments were configured: (1) a control experiment (CTRL) in which all crops are assumed to be rainfed; (2) an irrigation experiment (IRRIG) in which the irrigation module using only SW for irrigation is activated; and (3) a groundwater pumping experiment (PUMP) in which a groundwater pumpingmore » scheme coupled with the irrigation module is activated for conjunctive use of SW and GW for irrigation. The parameters associated with irrigation and groundwater pumping are calibrated based on a global inventory of census-based SW and GW use compiled by the Food and Agricultural Organization (FAO). Our results suggest that irrigation could lead to two major opposing effects: SW depletion/GW accumulation in regions with irrigation primarily fed by SW, and SW accumulation/GW depletion in regions with irrigation fed primarily by GW. Furthermore, irrigation depending primarily on SW tends to have larger impacts on low-flow than high-flow conditions, suggesting the potential to increase vulnerability to drought. By the end of the 21st century (2070-2099), climate change significantly increases (relative to 1971-2000) irrigation water demand across the world. Combined with the increased temporal-spatial variability of water supply, this may lead to severe issues of local water scarcity for irrigation. Regionally, irrigation has the potential to aggravate/alleviate climate-induced changes of SW/GW although such effects are negligible when averaged globally. Our results emphasize the importance of accounting for irrigation effects and irrigation sources in regional climate change impact assessment.« less

How do current irrigation practices perform? Evaluation of different irrigation scheduling approaches based on experiements and crop model simulations

NASA Astrophysics Data System (ADS)

Seidel, Sabine J.; Werisch, Stefan; Barfus, Klemens; Wagner, Michael; Schütze, Niels; Laber, Hermann

2014-05-01

The increasing worldwide water scarcity, costs and negative off-site effects of irrigation are leading to the necessity of developing methods of irrigation that increase water productivity. Various approaches are available for irrigation scheduling. Traditionally schedules are calculated based on soil water balance (SWB) calculations using some measure of reference evaporation and empirical crop coeffcients. These crop-specific coefficients are provided by the FAO but are also available for different regions (e.g. Germany). The approach is simple but there are several inaccuracies due to simplifications and limitations such as poor transferability. Crop growth models - which simulate the main physiological plant processes through a set of assumptions and calibration parameter - are widely used to support decision making, but also for yield gap or scenario analyses. One major advantage of mechanistic models compared to empirical approaches is their spatial and temporal transferability. Irrigation scheduling can also be based on measurements of soil water tension which is closely related to plant stress. Advantages of precise and easy measurements are able to be automated but face difficulties of finding the place where to probe especially in heterogenous soils. In this study, a two-year field experiment was used to extensively evaluate the three mentioned irrigation scheduling approaches regarding their efficiency on irrigation water application with the aim to promote better agronomic practices in irrigated horticulture. To evaluate the tested irrigation scheduling approaches, an extensive plant and soil water data collection was used to precisely calibrate the mechanistic crop model Daisy. The experiment was conducted with white cabbage (Brassica oleracea L.) on a sandy loamy field in 2012/13 near Dresden, Germany. Hereby, three irrigation scheduling approaches were tested: (i) two schedules were estimated based on SWB calculations using different crop coefficients, and (ii) one treatment was automatically drip irrigated using tensiometers (irrigation of 15 mm at a soil tension of -250 hPa at 30 cm soil depth). In treatment (iii), the irrigation schedule was estimated (using the same critera as in the tension-based treatment) applying the model Daisy partially calibrated against data of 2012. Moreover, one control treatment was minimally irrigated. Measured yield was highest for the tension-based treatment with a low irrigation water input (8.5 DM t/ha, 120 mm). Both SWB treatments showed lower yields and higher irrigation water input (both 8.3 DM t/ha, 306 and 410 mm). The simulation model based treatment yielded lower (7.5 DM t/ha, 106 mm) mainly due to drought stress caused by inaccurate simulation of the soil water dynamics and thus an overestimation of the soil moisture. The evaluation using the calibrated model estimated heavy deep percolation under both SWB treatments. Targeting the challenge to increase water productivity, soil water tension-based irrigation should be favoured. Irrigation scheduling based on SWB calculation requires accurate estimates of crop coefficients. A robust calibration of mechanistic crop models implies a high effort and can be recommended to farmers only to some extent but enables comprehensive crop growth and site analyses.

Physically based modeling in catchment hydrology at 50: Survey and outlook

NASA Astrophysics Data System (ADS)

Paniconi, Claudio; Putti, Mario

2015-09-01

Integrated, process-based numerical models in hydrology are rapidly evolving, spurred by novel theories in mathematical physics, advances in computational methods, insights from laboratory and field experiments, and the need to better understand and predict the potential impacts of population, land use, and climate change on our water resources. At the catchment scale, these simulation models are commonly based on conservation principles for surface and subsurface water flow and solute transport (e.g., the Richards, shallow water, and advection-dispersion equations), and they require robust numerical techniques for their resolution. Traditional (and still open) challenges in developing reliable and efficient models are associated with heterogeneity and variability in parameters and state variables; nonlinearities and scale effects in process dynamics; and complex or poorly known boundary conditions and initial system states. As catchment modeling enters a highly interdisciplinary era, new challenges arise from the need to maintain physical and numerical consistency in the description of multiple processes that interact over a range of scales and across different compartments of an overall system. This paper first gives an historical overview (past 50 years) of some of the key developments in physically based hydrological modeling, emphasizing how the interplay between theory, experiments, and modeling has contributed to advancing the state of the art. The second part of the paper examines some outstanding problems in integrated catchment modeling from the perspective of recent developments in mathematical and computational science.

Changes in water mass exchange between the NW shelf areas and the North Atlantic and their impact on nutrient/carbon cycling

NASA Astrophysics Data System (ADS)

Gröger, Matthias; Maier-Reimer, Ernst; Mikolajewicz, Uwe; Segschneider, Joachim; Sein, Dimitry

2010-05-01

Despite their comparatively small extension on a global scale, shelf areas are of interest for several economic reasons and climatic processes related to nutrient cycling, sea food supply, and biological productivity. Moreover, they constitute an important interface for nutrients, pollutants and freshwater on their pathway from the continents to the open ocean. This modelling study aims to investigate the spatial and temporal variability of water mass exchange between the North Atlantic and the NW European shelf and their impact on nutrient/carbon cycling and biological productivity. For this, a new modeling approach has been set up which bridges the gap between pure shelf models where water mass transports across the model domain too strongly depend on the formulation of open boundaries and global models suffering under their too coarse resolution in shelf regions. The new model consists of the global ocean and carbon cycle model MPIOM/HAMOCC with strongly increased resolution in the North Sea and the North Atlantic coupled to the regional atmosphere model REMO. The model takes the full luni-solar tides into account. It includes further a 12 layer sediment module with the relevant pore water chemistry. The main focus lies on the governing mechanisms of water mass exchange across the shelf break and the imprint on shelf biogeochemistry. For this, artificial tracers with a prescribed decay rate have been implemented to distinguish waters arriving from polar and shelf regions and those that originate from the tropics. Experiments were carried out for the years 1948 - 2007. The relationship to larger scale circulation patterns like the position and variability of the subtropical and subpolar gyres is analyzed. The water mass exchange is analyzed with respect to the nutrient concentration and productivity on the European shelf areas. The implementation of tides leads to an enhanced vertical mixing which causes lower sea surface temperatures compared to simulations without tidal forcing. The simulated tidal currents exceed velocities of 30cm per second in the near bottom layer which leads to a strong resuspension of sediment particles. These effects are most pronounced along narrow and shallow topographic structures like e.g. the English Channel. Experiments with artificial tracers show that the composition of water column changes along with the induced climate warming.

Does plant diversity affect the water balance of established grassland systems?

NASA Astrophysics Data System (ADS)

Leimer, Sophia; Bischoff, Sebastian; Blaser, Stefan; Boch, Steffen; Busch, Verena; Escher, Peter; Fischer, Markus; Kaupenjohann, Martin; Kerber, Katja; Klaus, Valentin; Michalzik, Beate; Prati, Daniel; Schäfer, Deborah; Schmitt, Barbara; Schöning, Ingo; Schwarz, Martin T.; Siemens, Jan; Thieme, Lisa; Wilcke, Wolfgang

2017-04-01

The water cycle drives nutrient cycles and plant productivity. The impact of land use on the water cycle has been extensively studied and there is experimental evidence that biodiversity modifies the water cycle in grasslands. However, the combined influences of land-use and associated biodiversity on the water cycle in established land-use systems are unclear. Therefore, we investigated how evapotranspiration (ETa), downward water flux (DF), and capillary rise (CR) in topsoil and subsoil are related to land-use and plant diversity in established, commercially managed grassland and compared these results to findings from experiments where plant diversity was manipulated. In three Central European regions ("Biodiversity Exploratories"), we studied 29 grassland plots (50 m x 50 m; 9-11 plots per region) from 2010 to 2015. The land-use types cover pasture, mown pasture, and meadow in at least triplicate per region. On each plot, we measured soil water contents, meteorological data (hourly resolution), cumulative precipitation (biweekly), plant species richness, the number of plants in the functional groups of grasses, herbs, and legumes (annually), and root biomass (once). Potential evapotranspiration (ETp) was calculated from meteorological data per plot. Missing data points of ETp and soil water contents were estimated with Bayesian hierarchical models. ETa, DF, and CR were calculated for two soil layers with a soil water balance model. The model is based on changes in soil water storage between subsequent observation dates and ETp, which was partitioned between soil layers according to root distribution. Water fluxes in annual resolution were statistically analyzed for land-use and biodiversity effects using repeated-measures analysis of variance (ANOVA). Land-use type did not affect water fluxes. Species richness did not influence DF and CR. DF from topsoil was higher on plots with more grass species, which is opposite to the results from a manipulative biodiversity experiment. The number of grasses and herbs influenced CR into topsoil. ETa from topsoil decreased with increasing species richness while ETa from subsoil increased. Opposing effects on ETa in the two soil layers were also observed for the numbers of herb and legume species. In manipulative biodiversity experiments, opposing effects on ETa from different soil layers are explained by higher plant cover and biomass in species-rich mixtures, reducing evaporation by shading of the topsoil, and deeper roots in species-rich mixtures, facilitating water use and increasing transpiration from subsoil. In our study, biomass decreased with increasing species richness because fertilizer application increased biomass production and decreased species richness. Plots with more grasses showed lower ETa from topsoil than plots with less grasses. However, the within-subject effects indicated higher ETa from topsoil in years with more grasses on individual plots than in years with less grasses. The latter finding complies with the results from a manipulative biodiversity experiment, which has homogeneous soil properties and management. The opposite between-subject effect is probably caused by variations in environmental conditions between plots. This indicates that processes controlling the biodiversity-water cycle relationship vary in real-world systems with environmental conditions, which are largely controlled for in manipulative biodiversity experiments.

Seismo-acoustic ray model benchmarking against experimental tank data.

PubMed

Camargo Rodríguez, Orlando; Collis, Jon M; Simpson, Harry J; Ey, Emanuel; Schneiderwind, Joseph; Felisberto, Paulo

2012-08-01

Acoustic predictions of the recently developed traceo ray model, which accounts for bottom shear properties, are benchmarked against tank experimental data from the EPEE-1 and EPEE-2 (Elastic Parabolic Equation Experiment) experiments. Both experiments are representative of signal propagation in a Pekeris-like shallow-water waveguide over a non-flat isotropic elastic bottom, where significant interaction of the signal with the bottom can be expected. The benchmarks show, in particular, that the ray model can be as accurate as a parabolic approximation model benchmarked in similar conditions. The results of benchmarking are important, on one side, as a preliminary experimental validation of the model and, on the other side, demonstrates the reliability of the ray approach for seismo-acoustic applications.

Representing Northern Peatland Hydrology and Biogeochemistry with ALM Land Surface Model

NASA Astrophysics Data System (ADS)

Shi, X.; Ricciuto, D. M.; Thornton, P. E.; Hanson, P. J.; Xu, X.; Mao, J.; Warren, J.; Yuan, F.; Norby, R. J.; Sebestyen, S.; Griffiths, N.; Weston, D. J.; Walker, A.

2017-12-01

Northern peatlands are likely to be important in future carbon cycle-climate feedbacks due to their large carbon pool and vulnerability to hydrological change. Predictive understanding of northern peatland hydrology is a necessary precursor to understanding the fate of massive carbon stores in these systems under the influence of present and future climate change. Current models have begun to address microtopographic controls on peatland hydrology, but none have included a prognostic calculation of peatland water table depth for a vegetated wetland, independent of prescribed regional water tables. Firstly, we introduce a new configuration of the land model (ALM) of Accelerated Climate model for Energy (ACME), which includes a fully prognostic water table calculation for a vegetated peatland. Secondly, we couple our new hydrology treatment with vertically structured soil organic matter pool, and the addition of components from methane biogeochemistry. Thirdly, we introduce a new PFT for mosses and implement the water content dynamics and physiology of mosses. We inform and test our model based on SPRUCE experiment to get the reasonable results for the seasonal dynamics water table depths, water content dynamics and physiology of mosses, and correct soil carbon profiles. Then, we use our new model structure to test the how the water table depth and CH4 emission will respond to elevated CO2 and different warming scenarios.

Estimating Irrigation Water Requirements using MODIS Vegetation Indices and Inverse Biophysical Modeling

NASA Technical Reports Server (NTRS)

Imhoff, Marc L.; Bounoua, Lahouari; Harriss, Robert; Harriss, Robert; Wells, Gordon; Glantz, Michael; Dukhovny, Victor A.; Orlovsky, Leah

2007-01-01

An inverse process approach using satellite-driven (MODIS) biophysical modeling was used to quantitatively assess water resource demand in semi-arid and arid agricultural lands by comparing the carbon and water flux modeled under both equilibrium (in balance with prevailing climate) and non-equilibrium (irrigated) conditions. Since satellite observations of irrigated areas show higher leaf area indices (LAI) than is supportable by local precipitation, we postulate that the degree to which irrigated lands vary from equilibrium conditions is related to the amount of irrigation water used. For an observation year we used MODIS vegetation indices, local climate data, and the SiB2 photosynthesis-conductance model to examine the relationship between climate and the water stress function for a given grid-cell and observed leaf area. To estimate the minimum amount of supplemental water required for an observed cell, we added enough precipitation to the prevailing climatology at each time step to minimize the water stress function and bring the soil to field capacity. The experiment was conducted on irrigated lands on the U.S. Mexico border and Central Asia and compared to estimates of irrigation water used.

Comparing field investigations with laboratory models to predict landfill leachate emissions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fellner, Johann; Doeberl, Gernot; Allgaier, Gerhard

2009-06-15

Investigations into laboratory reactors and landfills are used for simulating and predicting emissions from municipal solid waste landfills. We examined water flow and solute transport through the same waste body for different volumetric scales (laboratory experiment: 0.08 m{sup 3}, landfill: 80,000 m{sup 3}), and assessed the differences in water flow and leachate emissions of chloride, total organic carbon and Kjeldahl nitrogen. The results indicate that, due to preferential pathways, the flow of water in field-scale landfills is less uniform than in laboratory reactors. Based on tracer experiments, it can be discerned that in laboratory-scale experiments around 40% of pore watermore » participates in advective solute transport, whereas this fraction amounts to less than 0.2% in the investigated full-scale landfill. Consequences of the difference in water flow and moisture distribution are: (1) leachate emissions from full-scale landfills decrease faster than predicted by laboratory experiments, and (2) the stock of materials remaining in the landfill body, and thus the long-term emission potential, is likely to be underestimated by laboratory landfill simulations.« less

Leveraging this Golden Age of Remote Sensing and Modeling of Terrestrial Hydrology to Understand Water Cycling in the Water Availability Grand Challenge for North America

NASA Astrophysics Data System (ADS)

Painter, T. H.; Famiglietti, J. S.; Stephens, G. L.

2016-12-01

We live in a time of increasing strains on our global fresh water availability due to increasing population, warming climate, changes in precipitation, and extensive depletion of groundwater supplies. At the same time, we have seen enormous growth in capabilities to remotely sense the regional to global water cycle and model complex systems with physically based frameworks. The GEWEX Water Availability Grand Challenge for North America is poised to leverage this convergence of remote sensing and modeling capabilities to answer fundamental questions on the water cycle. In particular, we envision an experiment that targets the complex and resource-critical Western US from California to just into the Great Plains, constraining physically-based hydrologic modeling with the US and international remote sensing capabilities. In particular, the last decade has seen the implementation or soon-to-be launch of water cycle missions such as GRACE and GRACE-FO for groundwater, SMAP for soil moisture, GPM for precipitation, SWOT for terrestrial surface water, and the Airborne Snow Observatory for snowpack. With the advent of convection-resolving mesoscale climate and water cycle modeling (e.g. WRF, WRF-Hydro) and mesoscale models capable of quantitative assimilation of remotely sensed data (e.g. the JPL Western States Water Mission), we can now begin to test hypotheses on the nature and changes in the water cycle of the Western US from a physical standpoint. In turn, by fusing water cycle science, water management, and ecosystem management while addressing these hypotheses, this golden age of remote sensing and modeling can bring all fields into a markedly less uncertain state of present knowledge and decadal scale forecasts.

The role of molecular hydrogen and methane oxidation in the water vapour budget of the stratosphere

NASA Technical Reports Server (NTRS)

Le Texier, H.; Solomon, S.; Garcia, R. R.

1988-01-01

The detailed photochemistry of methane oxidation has been studied in a coupled chemical/dynamical model of the middle atmosphere. The photochemistry of formaldehyde plays an important role in determining the production of water vapor from methane oxidation. At high latitudes, the production and transport of molecular hydrogen is particularly important in determining the water vapor distribution. It is shown that the ratio of the methane vertical gradient to the water vapor vertical gradient at any particular latitude should not be expected to be precisely 2, due both to photochemical and dynamical effects. Modeled H2O profiles are compared with measurements from the Limb Infrared Monitor of the Stratosphere (LIMS) experiment at various latitudes. Molecular hydrogen is shown to be responsible for the formation of a secondary maximum displayed by the model water vapor profiles in high latitude summer, a feature also found in the LIMS data.

Airflow in Gravity Sewers - Determination of Wastewater Drag Coefficient.

PubMed

Bentzen, Thomas Ruby; Østertoft, Kristian Kilsgaard; Vollertsen, Jes; Fuglsang, Emil Dietz; Nielsen, Asbjørn Haaning

2016-03-01

Several experiments have been conducted in order to improve the understanding of the wastewater drag and the wall frictional force acting on the headspace air in gravity sewers. The aim of the study is to improve the data basis for a numerical model of natural sewer ventilation. The results of the study shows that by integrating the top/side wall shear stresses the log-law models for the air velocity distribution along the unwetted perimeter resulted in a good agreement with the friction forces calculated by use of the Colebrook-White formula for hydraulic smooth pipes. Secondly, the water surface drags were found by log-law models of the velocity distribution in turbulent flows to fit velocity profiles measured from the water surface and by integrating the water surface drags along the wetted perimeter, mean water surface drags were found and a measure of the water surface drag coefficient was found.

Modeling phytoremediation of nitrogen-polluted water using water hyacinth (Eichhornia crassipes)

NASA Astrophysics Data System (ADS)

Mayo, Aloyce W.; Hanai, Emmanuel E.

2017-08-01

Water hyacinth (Eichhornia crassipes) has a great potential for purification of wastewater through physical, chemical and biological mechanisms. In an attempt to improve the quality of effluents discharged from waste stabilization ponds at the University of Dar es Salaam, a pilot plant was constructed to experiment the effectiveness of this plants for transformation and removal of nitrogen. Samples of wastewater were collected and examined for water quality parameters, including pH, temperature, dissolved oxygen, and various forms of nitrogen, which were used as input parameters in a kinetic mathematical model. A conceptual model was then developed to model various processes in the system using STELLA 6.0.1 software. The results show that total nitrogen was removed by 63.9%. Denitrification contributed 73.8% of the removed nitrogen. Other dominant nitrogen removal mechanisms are net sedimentation and uptake by water hyacinth, which contributed 16.7% and 9.5% of the removed nitrogen, respectively. The model indicated that in presence of water hyacinth biofilm about 1.26 g Nm-2day-1 of nitrogen was removed. However, in the absence of biofilm in water hyacinth pond, the permanent nitrogen removal was only 0.89 g Nm-2day-1. This suggests that in absence of water hyacinth, the efficiency of nitrogen removal would decrease by 29.4%.

Chemical reactions simulated by ground-water-quality models

USGS Publications Warehouse

Grove, David B.; Stollenwerk, Kenneth G.

1987-01-01

Recent literature concerning the modeling of chemical reactions during transport in ground water is examined with emphasis on sorption reactions. The theory of transport and reactions in porous media has been well documented. Numerous equations have been developed from this theory, to provide both continuous and sequential or multistep models, with the water phase considered for both mobile and immobile phases. Chemical reactions can be either equilibrium or non-equilibrium, and can be quantified in linear or non-linear mathematical forms. Non-equilibrium reactions can be separated into kinetic and diffusional rate-limiting mechanisms. Solutions to the equations are available by either analytical expressions or numerical techniques. Saturated and unsaturated batch, column, and field studies are discussed with one-dimensional, laboratory-column experiments predominating. A summary table is presented that references the various kinds of models studied and their applications in predicting chemical concentrations in ground waters.

Validation of pore network simulations of ex-situ water distributions in a gas diffusion layer of proton exchange membrane fuel cells with X-ray tomographic images

NASA Astrophysics Data System (ADS)

Agaesse, Tristan; Lamibrac, Adrien; Büchi, Felix N.; Pauchet, Joel; Prat, Marc

2016-11-01

Understanding and modeling two-phase flows in the gas diffusion layer (GDL) of proton exchange membrane fuel cells are important in order to improve fuel cells performance. They are scientifically challenging because of the peculiarities of GDLs microstructures. In the present work, simulations on a pore network model are compared to X-ray tomographic images of water distributions during an ex-situ water invasion experiment. A method based on watershed segmentation was developed to extract a pore network from the 3D segmented image of the dry GDL. Pore network modeling and a full morphology model were then used to perform two-phase simulations and compared to the experimental data. The results show good agreement between experimental and simulated microscopic water distributions. Pore network extraction parameters were also benchmarked using the experimental data and results from full morphology simulations.

A physical model of ice sheet response to changes in subglacial hydrology

NASA Astrophysics Data System (ADS)

Andrews, L. C.; Catania, G. A.; Buttles, J. L.; Andrews, A.; Markowski, M.

2010-12-01

Using a physical ice sheet model, we investigate the degree to which motion is controlled by local loss of basal traction versus longitudinal coupling during diurnal, seasonal, and event-type water pulses. Our model can be used to reproduce the spatial pattern and magnitude of ice surface displacements and can aid in the interpretation of ground-based GPS measurements, as it eliminates many of the complicating factors influencing surface velocity measurements. This model consists of a 3 x 1.5 meter plastic box with a grid of holes on the bed used to inject water directly between the interface of the box and a silicone polymer. Water flow is visualized using a colored dye. The polymer response to perturbations in water flow is measured by tracking surface markers through a series of overhead images. We report on a suite of experiments that explore the relationship between water discharge, basal traction, and surface displacements and compare our results to ground-based GPS measurements from a transect in western Greenland.

Land-use change may exacerbate climate change impacts on water resources in the Ganges basin

NASA Astrophysics Data System (ADS)

Tsarouchi, Gina; Buytaert, Wouter

2018-02-01

Quantifying how land-use change and climate change affect water resources is a challenge in hydrological science. This work aims to quantify how future projections of land-use and climate change might affect the hydrological response of the Upper Ganges river basin in northern India, which experiences monsoon flooding almost every year. Three different sets of modelling experiments were run using the Joint UK Land Environment Simulator (JULES) land surface model (LSM) and covering the period 2000-2035: in the first set, only climate change is taken into account, and JULES was driven by the CMIP5 (Coupled Model Intercomparison Project Phase 5) outputs of 21 models, under two representative concentration pathways (RCP4.5 and RCP8.5), whilst land use was held fixed at the year 2010. In the second set, only land-use change is taken into account, and JULES was driven by a time series of 15 future land-use pathways, based on Landsat satellite imagery and the Markov chain simulation, whilst the meteorological boundary conditions were held fixed at years 2000-2005. In the third set, both climate change and land-use change were taken into consideration, as the CMIP5 model outputs were used in conjunction with the 15 future land-use pathways to force JULES. Variations in hydrological variables (stream flow, evapotranspiration and soil moisture) are calculated during the simulation period. Significant changes in the near-future (years 2030-2035) hydrologic fluxes arise under future land-cover and climate change scenarios pointing towards a severe increase in high extremes of flow: the multi-model mean of the 95th percentile of streamflow (Q5) is projected to increase by 63 % under the combined land-use and climate change high emissions scenario (RCP8.5). The changes in all examined hydrological components are greater in the combined land-use and climate change experiment. Results are further presented in a water resources context, aiming to address potential implications of climate change and land-use change from a water demand perspective. We conclude that future water demands in the Upper Ganges region for winter months may not be met.

Bone quantitative susceptibility mapping using a chemical species-specific R2* signal model with ultrashort and conventional echo data.

PubMed

Dimov, Alexey V; Liu, Zhe; Spincemaille, Pascal; Prince, Martin R; Du, Jiang; Wang, Yi

2018-01-01

To develop quantitative susceptibility mapping (QSM) of bone using an ultrashort echo time (UTE) gradient echo (GRE) sequence for signal acquisition and a bone-specific effective transverse relaxation rate ( R2*) to model water-fat MR signals for field mapping. Three-dimensional radial UTE data (echo times ≥ 40 μs) was acquired on a 3 Tesla scanner and fitted with a bone-specific signal model to map the chemical species and susceptibility field. Experiments were performed ex vivo on a porcine hoof and in vivo on healthy human subjects (n = 7). For water-fat separation, a bone-specific model assigning R2* decay mostly to water was compared with the standard models that assigned the same decay for both fat and water. In the ex vivo experiment, bone QSM was correlated with CT. Compared with standard models, the bone-specific R2* method significantly reduced errors in the fat fraction within the cortical bone in all tested data sets, leading to reduced artifacts in QSM. Good correlation was found between bone CT and QSM values in the porcine hoof (R 2  = 0.77). Bone QSM was successfully generated in all subjects. The QSM of bone is feasible using UTE with a conventional echo time GRE acquisition and a bone-specific R2* signal model. Magn Reson Med 79:121-128, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Assay of the Martian Regolith with Neutrons

NASA Technical Reports Server (NTRS)

Drake, Darrell M.; Reedy, R.; Jakowsky, B.; Clark, B.; Squyres, S.

1998-01-01

Different aspects of assaying Martian regolith using neutrons have been investigated. The epithermal portion of moderated neutrons spectra is dramatically effected by the presence of hydrogen (usually in the form of water). A simple analytic formula has been derived to describe the amplitude of this portion of the neutron spectrum as a function of water concentration. Several demonstration experiments have been performed and modeled with a Monte Carlo code. Results of these experiments generally agreed with the calculations to within 20%. In addition to He-3 detectors, lithium-glass scintillators and U-238 fission ion chambers were investigated to determine their applicability to space experiments.

The footprint of CO2 leakage in the water-column: Insights from numerical modeling based on a North Sea gas release experiment

NASA Astrophysics Data System (ADS)

Vielstädte, L.; Linke, P.; Schmidt, M.; Sommer, S.; Wallmann, K.; McGinnis, D. F.; Haeckel, M.

2013-12-01

Assessing the environmental impact of potential CO2 leakage from offshore carbon dioxide storage sites necessitates the investigation of the corresponding pH change in the water-column. Numerical models have been developed to simulate the buoyant rise and dissolution of CO2 bubbles in the water-column and the subsequent near-field dispersion of dissolved CO2 in seawater under ocean current and tidal forcing. In order to test and improve numerical models a gas release experiment has been conducted at 80 m water-depth within the Sleipner area (North Sea). CO2 and Kr (used as inert tracer gas) were released on top of a benthic lander at varying gas flows (<140 kg/day) and bubble sizes (de: 1-6 mm). pCO2 and pH were measured by in situ sensors to monitor the spread of the solute in different vertical heights and distances downstream of the artificial leak. The experiment and numerical analysis show that the impact of such leakage rates is limited to the near-field bottom waters, due to the rapid dissolution of CO2 bubbles in seawater (CO2 is being stripped within the first two to five meters of bubble rise). In particular, small bubbles, which will dissolve close to the seafloor, may cause a dangerous low-pH environment for the marine benthos. However, on the larger scale, the advective transport by e.g. tidal currents, dominates the CO2 dispersal in the North Sea and dilutes the CO2 peak quickly. The model results show that at the small scales (<100 m) of the CO2 plume the lateral eddy diffusion (~0.01 m2/s) has only a negligible effect. Overall, we can postulate that CO2 leakage at a rate of ~ 100 kg per day as in our experiment will only have a localized impact on the marine environment, thereby reducing pH substantially (by 0.4 units) within a diameter of less than 50 m around the release spot (depending on the duration of leakage and the current velocities). Strong currents and tidal cycles significantly reduce the spreading of low-pH water masses into the far-field by efficiently diluting the amount of CO2 in ambient seawater.

Cirrus clouds. I - A cirrus cloud model. II - Numerical experiments on the formation and maintenance of cirrus

NASA Technical Reports Server (NTRS)

Starr, D. OC.; Cox, S. K.

1985-01-01

A simplified cirrus cloud model is presented which may be used to investigate the role of various physical processes in the life cycle of a cirrus cloud. The model is a two-dimensional, time-dependent, Eulerian numerical model where the focus is on cloud-scale processes. Parametrizations are developed to account for phase changes of water, radiative processes, and the effects of microphysical structure on the vertical flux of ice water. The results of a simulation of a thin cirrostratus cloud are given. The results of numerical experiments performed with the model are described in order to demonstrate the important role of cloud-scale processes in determining the cloud properties maintained in response to larger scale forcing. The effects of microphysical composition and radiative processes are considered, as well as their interaction with thermodynamic and dynamic processes within the cloud. It is shown that cirrus clouds operate in an entirely different manner than liquid phase stratiform clouds.

Impact of single-point GPS integrated water vapor estimates on short-range WRF model forecasts over southern India

NASA Astrophysics Data System (ADS)

Kumar, Prashant; Gopalan, Kaushik; Shukla, Bipasha Paul; Shyam, Abhineet

2017-11-01

Specifying physically consistent and accurate initial conditions is one of the major challenges of numerical weather prediction (NWP) models. In this study, ground-based global positioning system (GPS) integrated water vapor (IWV) measurements available from the International Global Navigation Satellite Systems (GNSS) Service (IGS) station in Bangalore, India, are used to assess the impact of GPS data on NWP model forecasts over southern India. Two experiments are performed with and without assimilation of GPS-retrieved IWV observations during the Indian winter monsoon period (November-December, 2012) using a four-dimensional variational (4D-Var) data assimilation method. Assimilation of GPS data improved the model IWV analysis as well as the subsequent forecasts. There is a positive impact of ˜10 % over Bangalore and nearby regions. The Weather Research and Forecasting (WRF) model-predicted 24-h surface temperature forecasts have also improved when compared with observations. Small but significant improvements were found in the rainfall forecasts compared to control experiments.

Dielectric constant and low-frequency infrared spectra for liquid water and ice Ih within the E3B model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shi, L.; Ni, Y.; Drews, S. E. P.

2014-08-28

Two intrinsic difficulties in modeling condensed-phase water with conventional rigid non-polarizable water models are: reproducing the static dielectric constants for liquid water and ice Ih, and generating the peak at about 200 cm{sup −1} in the low-frequency infrared spectrum for liquid water. The primary physical reason for these failures is believed to be the missing polarization effect in these models, and consequently various sophisticated polarizable water models have been developed. However, in this work we pursue a different strategy and propose a simple empirical scheme to include the polarization effect only on the dipole surface (without modifying a model's intermolecularmore » interaction potential). We implement this strategy for our explicit three-body (E3B) model. Our calculated static dielectric constants and low-frequency infrared spectra are in good agreement with experiment for both liquid water and ice Ih over wide temperature ranges, albeit with one fitting parameter for each phase. The success of our modeling also suggests that thermal fluctuations about local minima and the energy differences between different proton-disordered configurations play minor roles in the static dielectric constant of ice Ih. Our analysis shows that the polarization effect is important in resolving the two difficulties mentioned above and sheds some light on the origin of several features in the low-frequency infrared spectra for liquid water and ice Ih.« less

Models for root water uptake under deficit irrigation

NASA Astrophysics Data System (ADS)

Lazarovitch, Naftali; Krounbi, Leilah; Simunek, Jirka

2010-05-01

Modern agriculture, with its dependence on irrigation, fertilizers, and pesticide application, contributes significantly to the water and solute influx through the soil into the groundwater, specifically in arid areas. The quality and quantity of this water as it passes through the vadose zone is influenced primarily by plant roots. Root water uptake is a function of both a physical root parameter, commonly referred to as the root length density, and the soil water status. The location of maximum water uptake in a homogenous soil profile of uniform water content and hydraulic conductivity occurs in the soil layer containing the largest root length density. Under field conditions, in a drying soil, plants are both subject to, and the source of, great spatial variability in the soil water content. The upper soil layers containing the bulk of the root zone are usually the most water depleted, while the deeper regions of the soil profile containing fewer roots are wetter. Changes in the physiological functioning of plants have been shown to result from extended periods of water stress, but the short term effects of water stress on root water uptake are less well understood. While plants can minimize transpiration and the resulting growth rates under limiting conditions to conserve water, many plants maintain a constant potential transpiration rate long after the commencement of the drying process. Compensatory uptake, whereby plants respond to non-uniform, limiting conditions by increasing water uptake from areas in the root zone characterized by more favorable conditions, is one such mechanism by which plants sustain potential transpiration rates in drying soils. The development of models which accurately characterize temporal and spatial root water uptake patterns is important for agricultural resource optimization, upon which subsequent management decisions affecting resource conservation and environmental pollution are based. Numerical simulations of root water uptake in various irrigation and fertilization regimes provide a much-needed alternative to tiring and expensive field work. These simulations can aid in raising agricultural water use efficiency while preserving soil and water resources. In this research, controlled lab experiments were carried out in soil-packed lysimeters designed for plant cultivation. Both the water balance of the growing plants as well as the temporary matric head distribution in the soil profile were calculated and measured. The experiment was conducted with sweet sorghum grown in two different soil profiles with different hydraulic properties. The experiment provided the data necessary to calculate the parameters of various models used to simulate root water uptake, by using an inverse solution method imbedded in the HYDRUS-1D code. The observed increase in uptake from the wetter soil regions under drying conditions, as measured and calculated, sheds light on the dominant role of soil hydraulic properties over the root distribution, and consequently root water uptake.

Numerical Simulation of Tuff Dissolution and Precipitation Experiments: Validation of Thermal-Hydrologic-Chemical (THC) Coupled-Process Modeling

NASA Astrophysics Data System (ADS)

Dobson, P. F.; Kneafsey, T. J.

2001-12-01

As part of an ongoing effort to evaluate THC effects on flow in fractured media, we performed a laboratory experiment and numerical simulations to investigate mineral dissolution and precipitation. To replicate mineral dissolution by condensate in fractured tuff, deionized water equilibrated with carbon dioxide was flowed for 1,500 hours through crushed Yucca Mountain tuff at 94° C. The reacted water was collected and sampled for major dissolved species, total alkalinity, electrical conductivity, and pH. The resulting steady-state fluid composition had a total dissolved solids content of about 140 mg/L; silica was the dominant dissolved constituent. A portion of the steady-state reacted water was flowed at 10.8 mL/hr into a 31.7-cm tall, 16.2-cm wide vertically oriented planar fracture with a hydraulic aperture of 31 microns in a block of welded Topopah Spring tuff that was maintained at 80° C at the top and 130° C at the bottom. The fracture began to seal within five days. A 1-D plug-flow model using the TOUGHREACT code developed at Berkeley Lab was used to simulate mineral dissolution, and a 2-D model was developed to simulate the flow of mineralized water through a planar fracture, where boiling conditions led to mineral precipitation. Predicted concentrations of the major dissolved constituents for the tuff dissolution were within a factor of 2 of the measured average steady-state compositions. The fracture-plugging simulations result in the precipitation of amorphous silica at the base of the boiling front, leading to a hundred-fold decrease in fracture permeability in less than 6 days, consistent with the laboratory experiment. These results help validate the use of the TOUGHREACT code for THC modeling of the Yucca Mountain system. The experiment and simulations indicate that boiling and concomitant precipitation of amorphous silica could cause significant reductions in fracture porosity and permeability on a local scale. The TOUGHREACT code will be used to evaluate larger-scale silica sealing observed in a portion of the Yellowstone geothermal system, a natural analog for the precipitation-experiment processes.

Water fluxes in root-soil-systems investigated by Magnetic resonance imaging

NASA Astrophysics Data System (ADS)

Haber-Pohlmeier, Sabina; Javaux, Mathieu; Pohlmeier, Andreas

2010-05-01

Water flux through soils is one of the most important control function with respect to the water supply for root and plant growth. The understanding of these processes bases generally on the interplay between experimental investigations and the development of theory and numerical models. In recent time detailed 3D models have been developed, but experimental information is mainly available from two-dimensional rhizotrons or only with coarse resolution from water content measurements by means of TDR probes and tensiometers. An emerging powerful tool for high resolution, non-invasive imaging of water content and fluxes in soils in saturated and unsaturated state is Nuclear Magnetic Resonance Imaging (MRI)[1,2]. With respect to water fluxes the slow flow velocities do not allow the direct monitoring by MRI flow imaging so indirect methods like transport of contrast agents should be applied. Therefore we have chosen Gd-DTPA [3], a negatively charged paramagnetic Gd-complex, as tracer for the investigation of water fluxes during i) infiltration and ii) injection experiments of unsaturated model soil with maize and lupin plants. The contrast of the NMR measurements was optimised using high resolution T1 weighted spin echo sequences. With respect to the infiltration experiment we observed that during rapid infiltration from the bottom the plume moved homogeneously into the bulk soil, but leaves out the immediate surrounding of the maize roots. After this initial period a continuously increasing enrichment of tracer in this region is monitored, but no uptake by the plant within one hour. Continuing these studies injection experiments have been performed where the tracer was placed in a small volume in the direct vicinity of the roots, and the entire water content changed only minimal even under quite dry conditions. For a well developed lupin root system we observed diffusive spreading followed by a very slow transporte of the plume to the root system over a period of two days. The important difference to the short term experiment is the observation of tracer uptake followed by an upward transport in the inner root tissues. This could also be proved by a following chemical analysis showing decreasing Gd content from the roots over the shoot to the leaves. In parallel a high resolution 3d image of the root system architecture was performed, in order to compare the experimentally observed motion of the plume with detailed 3D model calculations of water uptake and tracer transport. References: 1. Pohlmeier, A., et al., Imaging water fluxes in porous media by magnetic resonance imaging using D2O as a tracer. Mag. Res. Imag., 2008. 27(2): p. 285-292. 2. Pohlmeier, A., et al., Changes in Soil Water Content Resulting from Ricinus Root Uptake Monitored by Magnetic Resonance Imaging Vadose Zone Journal, 2008. 7: p. 1010-1017. 3. Haber-Pohlmeier, S., Stapf S. and Pohlmeier A., Waterflow monitored by tracer transport in natural porouse media using MRI. Vadose Zone Journal, submitted

Homogeneous Freezing of Water Droplets and its Dependence on Droplet Size

NASA Astrophysics Data System (ADS)

Schmitt, Thea; Möhler, Ottmar; Höhler, Kristina; Leisner, Thomas

2014-05-01

The formulation and parameterisation of microphysical processes in tropospheric clouds, such as phase transitions, is still a challenge for weather and climate models. This includes the homogeneous freezing of supercooled water droplets, since this is an important process in deep convective systems, where almost pure water droplets may stay liquid until homogeneous freezing occurs at temperatures around 238 K. Though the homogeneous ice nucleation in supercooled water is considered to be well understood, recent laboratory experiments with typical cloud droplet sizes showed one to two orders of magnitude smaller nucleation rate coefficients than previous literature results, including earlier results from experiments with single levitated water droplets and from cloud simulation experiments at the AIDA (Aerosol Interaction and Dynamics in the Atmosphere) facility. This motivated us to re-analyse homogeneous droplet freezing experiments conducted during the previous years at the AIDA cloud chamber. This cloud chamber has a volume of 84m3 and operates under atmospherically relevant conditions within wide ranges of temperature, pressure and humidity, whereby investigations of both tropospheric mixed-phase clouds and cirrus clouds can be realised. By controlled adiabatic expansions, the ascent of an air parcel in the troposphere can be simulated. According to our new results and their comparison to the results from single levitated droplet experiments, the homogeneous freezing of water droplets seems to be a volume-dependent process, at least for droplets as small as a few micrometers in diameter. A contribution of surface induced freezing can be ruled out, in agreement to previous conclusions from the single droplet experiments. The obtained volume nucleation rate coefficients are in good agreement, within error bars, with some previous literature data, including our own results from earlier AIDA experiments, but they do not agree with recently published lower volume nucleation rate coefficients. This contribution will show the results from the re-analysis of AIDA homogeneous freezing experiments with pure water droplets and will discuss the comparison to the literature data.

Adsorption of hydraulic fracturing fluid components 2-butoxyethanol and furfural onto granular activated carbon and shale rock.

PubMed

Manz, Katherine E; Haerr, Gregory; Lucchesi, Jessica; Carter, Kimberly E

2016-12-01

The objective of this study was to understand the adsorption ability of a surfactant and a non-surfactant chemical additive used in hydraulic fracturing onto shale and GAC. Experiments were performed at varying temperatures and sodium chloride concentrations to establish these impacts on the adsorption of the furfural (a non-surfactant) and 2-Butoxyethanol (2-BE) (a surfactant). Experiments were carried out in continuously mixed batch experiments with Langmuir and Freundlich isotherm modeling. The results of the experiments showed that adsorption of these compounds onto shale does not occur, which may allow these compounds to return to the surface in flowback and produced waters. The adsorption potential for these chemicals onto GAC follows the assumptions of the Langmuir model more strongly than those of the Freundlich model. The results show uptake of furfural and 2-BE occurs within 23 h in the presence of DI water, 0.1 mol L -1 sodium chloride, and in lab synthesized hydraulic fracturing brine. Based on the data, 83% of the furfural and 62% of the 2-BE was adsorbed using GAC. Copyright © 2016 Elsevier Ltd. All rights reserved.

Laboratory investigation of flux reduction from dense non-aqueous phase liquid (DNAPL) partial source zone remediation by enhanced dissolution

NASA Astrophysics Data System (ADS)

Kaye, Andrew J.; Cho, Jaehyun; Basu, Nandita B.; Chen, Xiaosong; Annable, Michael D.; Jawitz, James W.

2008-11-01

This study investigated the benefits of partial removal of dense nonaqueous phase liquid (DNAPL) source zones using enhanced dissolution in eight laboratory scale experiments. The benefits were assessed by characterizing the relationship between reductions in DNAPL mass and the corresponding reduction in contaminant mass flux. Four flushing agents were evaluated in eight controlled laboratory experiments to examine the effects of displacement fluid property contrasts and associated override and underride on contaminant flux reduction ( Rj) vs. mass reduction ( Rm) relationships ( Rj( Rm)): 1) 50% ethanol/50% water (less dense than water), 2) 40% ethyl-lactate/60% water (more dense than water), 3) 18% ethanol/26% ethyl-lactate/56% water (neutrally buoyant), and 4) 2% Tween-80 surfactant (also neutrally buoyant). For each DNAPL architecture evaluated, replicate experiments were conducted where source zone dissolution was conducted with a single flushing event to remove most of the DNAPL from the system, and with multiple shorter-duration floods to determine the path of the Rj( Rm) relationship. All of the single-flushing experiments exhibited similar Rj( Rm) relationships indicating that override and underride effects associated with cosolvents did not significantly affect the remediation performance of the agents. The Rj( Rm) relationship of the multiple injection experiments for the cosolvents with a density contrast with water tended to be less desirable in the sense that there was less Rj for a given Rm. UTCHEM simulations supported the observations from the laboratory experiments and demonstrated the capability of this model to predict Rj( Rm) relationships for non-uniformly distributed NAPL sources.

Transport mechanisms through PE-CVD coatings: influence of temperature, coating properties and defects on permeation of water vapour

NASA Astrophysics Data System (ADS)

Kirchheim, Dennis; Jaritz, Montgomery; Mitschker, Felix; Gebhard, Maximilian; Brochhagen, Markus; Hopmann, Christian; Böke, Marc; Devi, Anjana; Awakowicz, Peter; Dahlmann, Rainer

2017-03-01

Gas transport mechanisms through plastics are usually described by the temperature-dependent Arrhenius-model and compositions of several plastic layers are represented by the CLT. When it comes to thin films such as plasma-enhanced chemical vapour deposition (PE-CVD) or plasma-enhanced atomic layer deposition (PE-ALD) coatings on substrates of polymeric material, a universal model is lacking. While existing models describe diffusion through defects, these models presume that permeation does not occur by other means of transport mechanisms. This paper correlates the existing transport models with data from water vapour transmission experiments.

Verification of the modified model of drying process of a polymer liquid film on a flat substrate by experiment (3) - using organic solvent

NASA Astrophysics Data System (ADS)

Kagami, Hiroyuki

2007-05-01

We have proposed and modified a model of drying process of polymer solution coated on a flat substrate for flat polymer film fabrication and have presented the fruits through Photomask Japan 2002, 2003, 2004, Smart Materials, Nano-, and Micro-Smart Systems 2006 and so on. And for example numerical simulation of the model qualitatively reappears a typical thickness profile of the polymer film formed after drying, that is, the profile that the edge of the film is thicker and just the region next to the edge's bump is thinner. Then we have clarified dependence of distribution of polymer molecules on a flat substrate on a various parameters based on analysis of many numerical simulations. Then we did a few kinds of experiments so as to verify the modified model and reported the results of them through Photomask Japan 2005 and 2006. We could observe some results supporting the modified model. But we could not observe a characteristic region of a valley next to the edge's bump of a polymer film after drying. After some trial of various improved experiments we reached the conclusion that the characteristic region didn't appear by reason that water which vaporized slower than organic solvent was used as solvent. Then, in this study, we adopted organic solvent instead of water as solvent for experiments. As a result, that the characteristic region as mentioned above could be seen and we could verify the model more accurately. In this paper, we present verification of the model through above improved experiments for verification using organic solvent.

Optimization of linear and branched alkane interactions with water to simulate hydrophobic hydration

NASA Astrophysics Data System (ADS)

Ashbaugh, Henry S.; Liu, Lixin; Surampudi, Lalitanand N.

2011-08-01

Previous studies of simple gas hydration have demonstrated that the accuracy of molecular simulations at capturing the thermodynamic signatures of hydrophobic hydration is linked both to the fidelity of the water model at replicating the experimental liquid density at ambient pressure and an accounting of polarization interactions between the solute and water. We extend those studies to examine alkane hydration using the transferable potentials for phase equilibria united-atom model for linear and branched alkanes, developed to reproduce alkane phase behavior, and the TIP4P/2005 model for water, which provides one of the best descriptions of liquid water for the available fixed-point charge models. Alkane site/water oxygen Lennard-Jones cross interactions were optimized to reproduce the experimental alkane hydration free energies over a range of temperatures. The optimized model reproduces the hydration free energies of the fitted alkanes with a root mean square difference between simulation and experiment of 0.06 kcal/mol over a wide temperature range, compared to 0.44 kcal/mol for the parent model. The optimized model accurately reproduces the temperature dependence of hydrophobic hydration, as characterized by the hydration enthalpies, entropies, and heat capacities, as well as the pressure response, as characterized by partial molar volumes.

Numerical analysis of the primary processes controlling oxygen dynamics on the Louisiana shelf

NASA Astrophysics Data System (ADS)

Yu, L.; Fennel, K.; Laurent, A.; Murrell, M. C.; Lehrter, J. C.

2015-04-01

The Louisiana shelf, in the northern Gulf of Mexico, receives large amounts of freshwater and nutrients from the Mississippi-Atchafalaya river system. These river inputs contribute to widespread bottom-water hypoxia every summer. In this study, we use a physical-biogeochemical model that explicitly simulates oxygen sources and sinks on the Louisiana shelf to identify the key mechanisms controlling hypoxia development. First, we validate the model simulation against observed dissolved oxygen concentrations, primary production, water column respiration, and sediment oxygen consumption. In the model simulation, heterotrophy is prevalent in shelf waters throughout the year, except near the mouths of the Mississippi and Atchafalaya rivers, where primary production exceeds respiratory oxygen consumption during June and July. During this time, efflux of oxygen to the atmosphere, driven by photosynthesis and surface warming, becomes a significant oxygen sink. A substantial fraction of primary production occurs below the pycnocline in summer. We investigate whether this primary production below the pycnocline is mitigating the development of hypoxic conditions with the help of a sensitivity experiment where we disable biological processes in the water column (i.e., primary production and water column respiration). With this experiment we show that below-pycnocline primary production reduces the spatial extent of hypoxic bottom waters only slightly. Our results suggest that the combination of physical processes (advection and vertical diffusion) and sediment oxygen consumption largely determine the spatial extent and dynamics of hypoxia on the Louisiana shelf.

Effects of a thermal perturbation on mineralogy and pore water composition in a clay-rock: An experimental and modeling study

NASA Astrophysics Data System (ADS)

Gailhanou, H.; Lerouge, C.; Debure, M.; Gaboreau, S.; Gaucher, E. C.; Grangeon, S.; Grenèche, J.-M.; Kars, M.; Madé, B.; Marty, N. C. M.; Warmont, F.; Tournassat, C.

2017-01-01

The physical and chemical properties of clay-rocks are, at least partly, controlled by the chemical composition of their pore water. In evaluating the concept of disposing of radioactive waste in clay-rock formations, determining pore water composition is an important step in predicting how a clay-rock will behave over time and as a function of external forces, such as chemical and thermal perturbations. This study aimed to assess experimental and modeling methodology to calculate pore water composition in a clay-rock as a function of temperature (up to 80 °C). Hydrothermal alteration experiments were carried out on clay-rock samples. We conducted comprehensive chemical and mineralogical characterization of the material before and after reaction, and monitored how the chemical parameters in the liquid and gas phases changed. We compared the experimental results with the a priori predictions made by various models that differed in their hypotheses on the reactivity of the minerals present in the system. Thermodynamic equilibrium could not be assessed unequivocally in these experiments and most of the predicted mineralogy changes were too subtle to be tracked quantitatively. However, from observing the neo-formation of minerals such as goethite we were able to assess the prominent role of Fe-bearing phases in the outcome of the experiments, especially for the measured pH and pCO2 values. After calibrating the amount of reacting Fe-bearing phases with our data, we proposed a thermodynamic model that was capable of predicting the chemical evolution of the systems under investigation as well as the evolution of other systems already published in the literature, with the same clay-rock material but with significant differences in experimental conditions.

Polymer tensiometer with ceramic cones: a case study for a Brazilian soil.

NASA Astrophysics Data System (ADS)

Durigon, A.; de Jong van Lier, Q.; van der Ploeg, M. J.; Gooren, H. P. A.; Metselaar, K.; de Rooij, G. H.

2009-04-01

Laboratory outflow experiments, in combination with inverse modeling techniques, allow to simultaneously determine retention and hydraulic conductivity functions. A numerical model solves the pressure-head-based form of the Richards' equation for unsaturated flow in a rigid porous medium. Applying adequate boundary conditions, the cumulative outflow is calculated at prescribed times, and as a function of the set of optimized parameters. These parameters are evaluated by nonlinear least-squares fitting of predicted to observed cumulative outflow with time. An objective function quantifies this difference between calculated and observed cumulative outflow and between predicted and measured soil water retention data. Using outflow data only in the objective function, the multistep outflow method results in unique estimates of the retention and hydraulic conductivity functions. To obtain more reliable estimates of the hydraulic conductivity as a function of the water content using the inverse method, the outflow data must be supplemented with soil retention data. To do so tensiometers filled with a polymer solution instead of water were used. The measurement range of these tensiometers is larger than that of the conventional tensiometers, being able to measure the entire pressure head range over which crops take up water, down to values in the order of -1.6 MPa. The objective of this study was to physically characterize a Brazilian red-yellow oxisol using measurements in outflow experiments by polymer tensiometers and processing these data with the inverse modeling technique for use in the analysis of a field experiment and in modeling. The soil was collected at an experimental site located in Piracicaba, Brazil, 22° 42 S, 47° 38 W, 550 m above sea level.

Analysis of the Impact of Realistic Wind Size Parameter on the Delft3D Model

NASA Astrophysics Data System (ADS)

Washington, M. H.; Kumar, S.

2017-12-01

The wind size parameter, which is the distance from the center of the storm to the location of the maximum winds, is currently a constant in the Delft3D model. As a result, the Delft3D model's output prediction of the water levels during a storm surge are inaccurate compared to the observed data. To address these issues, an algorithm to calculate a realistic wind size parameter for a given hurricane was designed and implemented using the observed water-level data for Hurricane Matthew. A performance evaluation experiment was conducted to demonstrate the accuracy of the model's prediction of water levels using the realistic wind size input parameter compared to the default constant wind size parameter for Hurricane Matthew, with the water level data observed from October 4th, 2016 to October 9th, 2016 from National Oceanic and Atmospheric Administration (NOAA) as a baseline. The experimental results demonstrate that the Delft3D water level output for the realistic wind size parameter, compared to the default constant size parameter, matches more accurately with the NOAA reference water level data.

Sediment transport through self-adjusting, bedrock-walled waterfall plunge pools

NASA Astrophysics Data System (ADS)

Scheingross, Joel S.; Lamb, Michael P.

2016-05-01

Many waterfalls have deep plunge pools that are often partially or fully filled with sediment. Sediment fill may control plunge-pool bedrock erosion rates, partially determine habitat availability for aquatic organisms, and affect sediment routing and debris flow initiation. Currently, there exists no mechanistic model to describe sediment transport through waterfall plunge pools. Here we develop an analytical model to predict steady-state plunge-pool depth and sediment-transport capacity by combining existing jet theory with sediment transport mechanics. Our model predicts plunge-pool sediment-transport capacity increases with increasing river discharge, flow velocity, and waterfall drop height and decreases with increasing plunge-pool depth, radius, and grain size. We tested the model using flume experiments under varying waterfall and plunge-pool geometries, flow hydraulics, and sediment size. The model and experiments show that through morphodynamic feedbacks, plunge pools aggrade to reach shallower equilibrium pool depths in response to increases in imposed sediment supply. Our theory for steady-state pool depth matches the experiments with an R2 value of 0.8, with discrepancies likely due to model simplifications of the hydraulics and sediment transport. Analysis of 75 waterfalls suggests that the water depths in natural plunge pools are strongly influenced by upstream sediment supply, and our model provides a mass-conserving framework to predict sediment and water storage in waterfall plunge pools for sediment routing, habitat assessment, and bedrock erosion modeling.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Getirana, Augusto; Dutra, Emanuel; Guimberteau, Matthieu

Despite recent advances in modeling and remote sensing of land surfaces, estimates of the global water budget are still fairly uncertain. The objective of this study is to evaluate the water budget of the Amazon basin based on several state-of-the-art land surface model (LSM) outputs. Water budget variables [total water storage (TWS), evapotranspiration (ET), surface runoff (R) and baseflow (B)] are evaluated at the basin scale using both remote sensing and in situ data. Fourteen LSMs were run using meteorological forcings at a 3-hourly time step and 1-degree spatial resolution. Three experiments are performed using precipitation which has been rescaledmore » to match monthly global GPCP and GPCC datasets and the daily HYBAM dataset for the Amazon basin. R and B are used to force the Hydrological Modeling and Analysis Platform (HyMAP) river routing scheme and simulated discharges are compared against observations at 165 gauges. Simulated ET and TWS are compared against FLUXNET and MOD16A2 evapotranspiration, and GRACE TWS estimates in different catchments. At the basin scale, simulated ET ranges from 2.39mm.d-1 to 3.26mm.d-1 and a low spatial correlation between ET and P indicates that evapotranspiration does not depend on water availability over most of the basin. Results also show that other simulated water budget variables vary significantly as a function of both the LSM and precipitation used, but simulated TWS generally agree at the basin scale. The best water budget simulations resulted from experiments using the HYBAM dataset, mostly explained by a denser rainfall gauge network the daily rescaling.« less

Deterministic Local Sensitivity Analysis of Augmented Systems - II: Applications to the QUENCH-04 Experiment Using the RELAP5/MOD3.2 Code System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ionescu-Bujor, Mihaela; Jin Xuezhou; Cacuci, Dan G.

2005-09-15

The adjoint sensitivity analysis procedure for augmented systems for application to the RELAP5/MOD3.2 code system is illustrated. Specifically, the adjoint sensitivity model corresponding to the heat structure models in RELAP5/MOD3.2 is derived and subsequently augmented to the two-fluid adjoint sensitivity model (ASM-REL/TF). The end product, called ASM-REL/TFH, comprises the complete adjoint sensitivity model for the coupled fluid dynamics/heat structure packages of the large-scale simulation code RELAP5/MOD3.2. The ASM-REL/TFH model is validated by computing sensitivities to the initial conditions for various time-dependent temperatures in the test bundle of the Quench-04 reactor safety experiment. This experiment simulates the reflooding with water ofmore » uncovered, degraded fuel rods, clad with material (Zircaloy-4) that has the same composition and size as that used in typical pressurized water reactors. The most important response for the Quench-04 experiment is the time evolution of the cladding temperature of heated fuel rods. The ASM-REL/TFH model is subsequently used to perform an illustrative sensitivity analysis of this and other time-dependent temperatures within the bundle. The results computed by using the augmented adjoint sensitivity system, ASM-REL/TFH, highlight the reliability, efficiency, and usefulness of the adjoint sensitivity analysis procedure for computing time-dependent sensitivities.« less

Forced convective melting at an evolving ice-water interface

NASA Astrophysics Data System (ADS)

Ramudu, Eshwan; Hirsh, Benjamin; Olson, Peter; Gnanadesikan, Anand

2015-11-01

The intrusion of warm Circumpolar Deep Water into the ocean cavity between the base of ice shelves and the sea bed in Antarctica causes melting at the ice shelves' basal surface, producing a turbulent melt plume. We conduct a series of laboratory experiments to investigate how the presence of forced convection (turbulent mixing) changes the delivery of heat to the ice-water interface. We also develop a theoretical model for the heat balance of the system that can be used to predict the change in ice thickness with time. In cases of turbulent mixing, the heat balance includes a term for turbulent heat transfer that depends on the friction velocity and an empirical coefficient. We obtain a new value for this coefficient by comparing the modeled ice thickness against measurements from a set of nine experiments covering one order of magnitude of Reynolds numbers. Our results are consistent with the altimetry-inferred melting rate under Antarctic ice shelves and can be used in climate models to predict their disintegration. This work was supported by NSF grant EAR-110371.

An Evaluation of the Scattering Law for Light and Heavy Water in ENDF-6 Format, Based on Experimental Data and Molecular Dynamics

NASA Astrophysics Data System (ADS)

Márquez Damián, J. I.; Granada, J. R.; Malaspina, D. C.

2014-04-01

In this work we present an evaluation in ENDF-6 format of the scattering law for light and heavy water computed using the LEAPR module of NJOY99. The models used in this evaluation are based on experimental data on light water dynamics measured by Novikov, partial structure factors obtained by Soper, and molecular dynamics calculations performed with GROMACS using a reparameterized version of the flexible SPC model by Toukan and Rahman. The models use the Egelstaff-Schofield diffusion equation for translational motion, and a continuous spectrum calculated from the velocity autocorrelation function computed with GROMACS. The scattering law for H in H2O is computed using the incoherent approximation, and the scattering law D and O in D2O are computed using the Sköld approximation for coherent scattering. The calculations show significant improvement over ENDF/B-VI and ENDF/B-VII when compared with measurements of the total cross section, differential scattering experiments and quasi-elastic neutron scattering experiments (QENS).

Improvements in and actual performance of the Plant Experiment Unit onboard Kibo, the Japanese experiment module on the international space station

NASA Astrophysics Data System (ADS)

Yano, Sachiko; Kasahara, Haruo; Masuda, Daisuke; Tanigaki, Fumiaki; Shimazu, Toru; Suzuki, Hiromi; Karahara, Ichirou; Soga, Kouichi; Hoson, Takayuki; Tayama, Ichiro; Tsuchiya, Yoshikazu; Kamisaka, Seiichiro

2013-03-01

In 2004, Japan Aerospace Exploration Agency developed the engineered model of the Plant Experiment Unit and the Cell Biology Experiment Facility. The Plant Experiment Unit was designed to be installed in the Cell Biology Experiment Facility and to support the seed-to-seed life cycle experiment of Arabidopsis plants in space in the project named Space Seed. Ground-based experiments to test the Plant Experiment Unit showed that the unit needed further improvement of a system to control the water content of a seedbed using an infrared moisture analyzer and that it was difficult to keep the relative humidity inside the Plant Experiment Unit between 70 and 80% because the Cell Biology Experiment Facility had neither a ventilation system nor a dehumidifying system. Therefore, excess moisture inside the Cell Biology Experiment Facility was removed with desiccant bags containing calcium chloride. Eight flight models of the Plant Experiment Unit in which dry Arabidopsis seeds were fixed to the seedbed with gum arabic were launched to the International Space Station in the space shuttle STS-128 (17A) on August 28, 2009. Plant Experiment Unit were installed in the Cell Biology Experiment Facility with desiccant boxes, and then the Space Seed experiment was started in the Japanese Experiment Module, named Kibo, which was part of the International Space Station, on September 10, 2009 by watering the seedbed and terminated 2 months later on November 11, 2009. On April 19, 2010, the Arabidopsis plants harvested in Kibo were retrieved and brought back to Earth by the space shuttle mission STS-131 (19A). The present paper describes the Space Seed experiment with particular reference to the development of the Plant Experiment Unit and its actual performance in Kibo onboard the International Space Station. Downlinked images from Kibo showed that the seeds had started germinating 3 days after the initial watering. The plants continued growing, producing rosette leaves, inflorescence stems, flowers, and fruits in the Plant Experiment Unit. In addition, the senescence of rosette leaves was found to be delayed in microgravity.

Temperature measuring analysis of the nuclear reactor fuel assembly

DOE Office of Scientific and Technical Information (OSTI.GOV)

Urban, F., E-mail: jozef.bereznai@stuba.sk, E-mail: zdenko.zavodny@stuba.sk; Kučák, L., E-mail: jozef.bereznai@stuba.sk, E-mail: zdenko.zavodny@stuba.sk; Bereznai, J., E-mail: jozef.bereznai@stuba.sk, E-mail: zdenko.zavodny@stuba.sk

2014-08-06

Study was based on rapid changes of measured temperature values from the thermocouple in the VVER 440 nuclear reactor fuel assembly. Task was to determine origin of fluctuations of the temperature values by experiments on physical model of the fuel assembly. During an experiment, heated water was circulating in the system and cold water inlet through central tube to record sensitivity of the temperature sensor. Two positions of the sensor was used. First, just above the central tube in the physical model fuel assembly axis and second at the position of the thermocouple in the VVER 440 nuclear reactor fuelmore » assembly. Dependency of the temperature values on time are presented in the diagram form in the paper.« less

Electrostatic Model Applied to ISS Charged Water Droplet Experiment

NASA Technical Reports Server (NTRS)

Stevenson, Daan; Schaub, Hanspeter; Pettit, Donald R.

2015-01-01

The electrostatic force can be used to create novel relative motion between charged bodies if it can be isolated from the stronger gravitational and dissipative forces. Recently, Coulomb orbital motion was demonstrated on the International Space Station by releasing charged water droplets in the vicinity of a charged knitting needle. In this investigation, the Multi-Sphere Method, an electrostatic model developed to study active spacecraft position control by Coulomb charging, is used to simulate the complex orbital motion of the droplets. When atmospheric drag is introduced, the simulated motion closely mimics that seen in the video footage of the experiment. The electrostatic force's inverse dependency on separation distance near the center of the needle lends itself to analytic predictions of the radial motion.

Modeling the water use efficiency of soybean and maize plants under environmental stresses: application of a synthetic model of photosynthesis-transpiration based on stomatal behavior.

PubMed

Yu, Gui-Rui; Wang, Qiu-Feng; Zhuang, Jie

2004-03-01

Understanding the variability of plant WUE and its control mechanism can promote the comprehension to the coupling relationship of water and carbon cycle in terrestrial ecosystem, which is the foundation for developing water-carbon coupling cycle model. In this paper, we made clear the differences of net assimilation rate, transpiration rate, and WUE between the two species by comparing the experiment data of soybean (Glycine max Merr.) and maize (Zea mays L.) plants under water and soil nutrient stresses. WUE of maize was about two and a half times more than that of soybean in the same weather conditions. Enhancement of water stresses led to the marked decrease of Am and Em of two species, but water stresses of some degree could improve WUE, and this effect was more obvious for soybean. WUE of the two species changed with psiL in a second-order curve relation, and the WUE at high fertilization was higher than that at low fertilization, this effect was especially obvious for maize. Moreover, according to the synthetic model of photosynthesis-transpiration based on stomatal behavior (SMPTSB) presented by Yu et al. (2001), the WUE model and its applicability were discussed with the data measured in this experiment. The WUE estimated by means of the model accorded well with the measured values. However, this model underestimated the WUE for maize slightly, thus further improvement on the original model was made in this study. Finally, by discussing some physiological factors controlling Am and WUE, we made clear the physiological explanation for differences of the relative contributions of stomata- and mesophyll processes to control of Am and WUE, and the applicability of WUE model between the two species. Because the requirement to stomatal conductance by unit change of net assimilation rate is different, the responses of opening-closing activity of stomata to environmental stresses are different between the two species. To obtain the same level of net assimilation rate, soybean has to open its stomata more widely to keep small stomatal resistance, as compared with maize.

Research on the water resources regulation ability model of dams in the Huai He River Basin considering ecological and management factors

NASA Astrophysics Data System (ADS)

Shui, Y.; Liu, H. C.; Li, L. H.; Yu, G. G.; Liu, J.

2016-08-01

Research that assesses the scheduling ability of dams gamers a great deal of attention due to the global water resource crisis. These studies can provide useful and practical suggestions for scheduling the water resources of dams to solve problems, such as addressing ecological water needs and so on. Recent studies have primarily evaluated the schedule ability of dams according to their quantifiable attributes, such as water quantity, flow velocity, etc. However, the ecological and management status can directly determine the possibility and efficiency of a dam's water resource scheduling. This paper presents an evaluation model to assess the scheduling capacity of dams that takes into consideration ecological and management factors. In the experiment stage, this paper takes the Sha Ying river of the Huai He River Basin as an example to evaluate the scheduling ability of its dams. The results indicate that the proposed evaluation model can provide more precise and practical suggestions.

Physically Accurate Soil Freeze-Thaw Processes in a Global Land Surface Scheme

NASA Astrophysics Data System (ADS)

Cuntz, Matthias; Haverd, Vanessa

2018-01-01

The model Soil-Litter-Iso (SLI) calculates coupled heat and water transport in soil. It was recently implemented into the Australian land surface model CABLE, which is the land component of the Australian Community Climate and Earth System Simulator (ACCESS). Here we extended SLI to include accurate freeze-thaw processes in the soil and snow. SLI provides thence an implicit solution of the energy and water balances of soil and snow as a standalone model and within CABLE. The enhanced SLI was tested extensively against theoretical formulations, laboratory experiments, field data, and satellite retrievals. The model performed well for all experiments at wide-ranging temporal and spatial scales. SLI melts snow faster at the end of the cold season compared to observations though because there is no subgrid variability within SLI given by the implicit, coupled solution of energy and water. Combined CABLE-SLI shows very realistic dynamics and extent of permafrost on the Northern hemisphere. It illustrated, however, also the limits of possible comparisons between large-scale land surface models and local permafrost observations. CABLE-SLI exhibits the same patterns of snow depth and snow water equivalent on the Northern hemisphere compared to satellite-derived observations but quantitative comparisons depend largely on the given meteorological input fields. Further extension of CABLE-SLI with depth-dependence of soil carbon will allow realistic projections of the development of permafrost and frozen carbon stocks in a changing climate.

Evaluating short-term hydro-meteorological fluxes using GRACE-derived water storage changes

NASA Astrophysics Data System (ADS)

Eicker, A.; Jensen, L.; Springer, A.; Kusche, J.

2017-12-01

Atmospheric and terrestrial water budgets, which represent important boundary conditions for both climate modeling and hydrological studies, are linked by evapotranspiration (E) and precipitation (P). These fields are provided by numerical weather prediction models and atmospheric reanalyses such as ERA-Interim and MERRA-Land; yet, in particular the quality of E is still not well evaluated. Via the terrestrial water budget equation, water storage changes derived from products of the Gravity Recovery and Climate Experiment (GRACE) mission, combined with runoff (R) data can be used to assess the realism of atmospheric models. In this contribution we will investigate the closure of the water balance for short-term fluxes, i.e. the agreement of GRACE water storage changes with P-E-R flux time series from different (global and regional) atmospheric reanalyses, land surface models, as well as observation-based data sets. Missing river runoff observations will be extrapolated using the calibrated rainfall-runoff model GR2M. We will perform a global analysis and will additionally focus on selected river basins in West Africa. The investigations will be carried out for various temporal scales, focusing on short-term fluxes down to daily variations to be detected in daily GRACE time series.

Modeling of bromate formation by ozonation of surface waters in drinking water treatment.

PubMed

Legube, Bernard; Parinet, Bernard; Gelinet, Karine; Berne, Florence; Croue, Jean-Philippe

2004-04-01

The main objective of this paper is to try to develop statistically and chemically rational models for bromate formation by ozonation of clarified surface waters. The results presented here show that bromate formation by ozonation of natural waters in drinking water treatment is directly proportional to the "Ct" value ("Ctau" in this study). Moreover, this proportionality strongly depends on many parameters: increasing of pH, temperature and bromide level leading to an increase of bromate formation; ammonia and dissolved organic carbon concentrations causing a reverse effect. Taking into account limitation of theoretical modeling, we proposed to predict bromate formation by stochastic simulations (multi-linear regression and artificial neural networks methods) from 40 experiments (BrO(3)(-) vs. "Ctau") carried out with three sand filtered waters sampled on three different waterworks. With seven selected variables we used a simple architecture of neural networks, optimized by "neural connection" of SPSS Inc./Recognition Inc. The bromate modeling by artificial neural networks gives better result than multi-linear regression. The artificial neural networks model allowed us classifying variables by decreasing order of influence (for the studied cases in our variables scale): "Ctau", [N-NH(4)(+)], [Br(-)], pH, temperature, DOC, alkalinity.

Obtaining higher-accuracy estimates of water-rich rocks and water-poor sand dunes on Mars in active neutron experiments

NASA Astrophysics Data System (ADS)

Gabriel, T. S. J.; Hardgrove, C.; Litvak, M. L.; Nowicki, S.; Mitrofanov, I. G.; Boynton, W. V.; Fedosov, F.; Golovin, D.; Jun, I.; Mischna, M.; Tate, C. G.; Moersch, J.; Harshman, K.; Kozyrev, A.; Malakhov, A. V.; Mokrousov, M.; Nikiforov, S.; Sanin, A. B.; Vostrukhin, A.; Thompson, L. M.

2017-12-01

The Dynamic Albedo of Neutrons (DAN) experiment on the Mars Science Laboratory Curiosity Rover delivers high-energy (14.1 MeV) pulses of neutrons into the surface when operating in "active" mode. Neutrons are moderated in the subsurface and return to two detectors to provide a time-of-flight profile in 64 time-bins in epithermal and thermal energy ranges. Results are compared to simulations of the experiment in the Monte Carlo N-Particle Transport Code where several aspects are modeled including the DAN detectors, neutron source, rover components, and underlying rock. Models can be improved by increasing the fidelity of the rock geochemistry as informed by instruments including the Alpha Particle X-Ray Spectrometer (APXS). Furthermore, increasing the fidelity of the rock morphology in models is enabled by the suite of imaging instruments on the rover.To rapidly interpret DAN data a set of pre-simulated generic rock density and bulk geochemistry models are compared to several DAN active observations. While, to first order, this methodology provides an indication of significant geochemical changes in the subsurface, higher-fidelity models should be used to provide accurate constraints on water content, depth of geologic layers, or abundance of neutron absorbers. For example, in high-silicon, low-iron rocks observed along the rover's traverse, generic models can differ by several wt%H2O from models that use APXS measurements of nearby drill samples. Accurate measurements of high-silicon targets are necessary in outlining the extent of aqueous alteration and hydrothermal activity in Gale Crater. Additionally, we find that for DAN active experiments over sand dunes best-fit models can differ by greater than 0.5 wt%HO when the upper layer density is reduced by 0.6 g/cm3 to account for the low-bulk density of sand. In areas where the rock geochemistry differs little from generic models the difference in results is expectedly less disparate. We report refined wt%HO values for high-silicon, aqueously-altered rock and comparatively dry sand dunes along the rover traverse. We also outline the methodology for providing accurate geochemical and morphological constraints using DAN active measurements.

Influences of pH and CO2 on the formation of Metasilicate mineral water in Changbai Mountain, Northeast China

NASA Astrophysics Data System (ADS)

Yan, Baizhong; Xiao, Changlai; Liang, Xiujuan; Wu, Shili

2017-07-01

Mineral dissolution reactions actively participate in controlling the composition of mineral water. In this study, water soluble, acidic-alkaline and carbonated solution experiments were designed, and mineral reaction mechanisms were researched using chemical kinetics and the minimum free-energy method. The results showed that the release of metasilicate was controlled by pH, CO2, and rock characteristics. In the water soluble experiment, the release process of metasilicate in powdered rocks reached equilibrium after 40 days, while metasilicate in solid rocks took 170 days. The release process of metasilicate in solid rocks satisfied an asymptotic model, while in powdered rocks it accorded with the Stanford reaction kinetic model. In the acidic-alkaline experiment, metasilicate was released earlier under acidic conditions (2.46 < pH < 7) than under alkaline conditions (7 < pH < 10.61). The release process of metasilicate under acidic conditions reached equilibrium in 40 days, compared with 60 days for alkaline conditions. The addition of CO2 to the water solution was beneficial to the formation of metasilicate. Under neutral pH conditions, the reaction barely occurred. Under alkaline conditions, metasilicate was produced by the hydrolysis of metasilicate minerals. Under acidic and additional CO2 conditions, metasilicate formation was mainly via the reaction of H+, CO2, and metasilicate minerals. From these results, we concluded that the metasilicate mineral water from the Changbai Mountains, Jingyu County, is generated by a combination of the hydrolysis of metasilicate minerals and the reaction of H+, CO2, and metasilicate minerals. These results can contribute to a better development and protection of the mineral water resources in the Changbai Mountains.

A sprinkling experiment to quantify celerity-velocity differences at the hillslope scale

EPA Science Inventory

The difference between celerity and velocity of hillslope water flow is poorly understood. We assessed these differences by combining a 24-day hillslope sprinkling experiment with a spatially explicit hydrologic model analysis. We focused our work at Watershed 10 at the H.J. And...

Coarse-grained model of water diffusion and proton conductivity in hydrated polyelectrolyte membrane

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Ming-Tsung; Vishnyakov, Aleksey; Neimark, Alexander V., E-mail: aneimark@rutgers.edu

2016-01-07

Using dissipative particle dynamics (DPD), we simulate nanoscale segregation, water diffusion, and proton conductivity in hydrated sulfonated polystyrene (sPS). We employ a novel model [Lee et al. J. Chem. Theory Comput. 11(9), 4395-4403 (2015)] that incorporates protonation/deprotonation equilibria into DPD simulations. The polymer and water are modeled by coarse-grained beads interacting via short-range soft repulsion and smeared charge electrostatic potentials. The proton is introduced as a separate charged bead that forms dissociable Morse bonds with the base beads representing water and sulfonate anions. Morse bond formation and breakup artificially mimics the Grotthuss mechanism of proton hopping between the bases. Themore » DPD model is parameterized by matching the proton mobility in bulk water, dissociation constant of benzenesulfonic acid, and liquid-liquid equilibrium of water-ethylbenzene solutions. The DPD simulations semi-quantitatively predict nanoscale segregation in the hydrated sPS into hydrophobic and hydrophilic subphases, water self-diffusion, and proton mobility. As the hydration level increases, the hydrophilic subphase exhibits a percolation transition from isolated water clusters to a 3D network. The analysis of hydrophilic subphase connectivity and water diffusion demonstrates the importance of the dynamic percolation effect of formation and breakup of temporary junctions between water clusters. The proposed DPD model qualitatively predicts the ratio of proton to water self-diffusion and its dependence on the hydration level that is in reasonable agreement with experiments.« less

Evaluating Cloud Initialization in a Convection-permit NWP Model

NASA Astrophysics Data System (ADS)

Li, Jia; Chen, Baode

2015-04-01

In general, to avoid "double counting precipitation" problem, in convection permit NWP models, it was a common practice to turn off convective parameterization. However, if there were not any cloud information in the initial conditions, the occurrence of precipitation could be delayed due to spin-up of cloud field or microphysical variables. In this study, we utilized the complex cloud analysis package from the Advanced Regional Prediction System (ARPS) to adjust the initial states of the model on water substance, such as cloud water, cloud ice, rain water, et al., that is, to initialize the microphysical variables (i.e., hydrometers), mainly based on radar reflectivity observations. Using the Advanced Research WRF (ARW) model, numerical experiments with/without cloud initialization and convective parameterization were carried out at grey-zone resolutions (i.e. 1, 3, and 9 km). The results from the experiments without convective parameterization indicate that model ignition with radar reflectivity can significantly reduce spin-up time and accurately simulate precipitation at the initial time. In addition, it helps to improve location and intensity of predicted precipitation. With grey-zone resolutions (i.e. 1, 3, and 9 km), using the cumulus convective parameterization scheme (without radar data) cannot produce realistic precipitation at the early time. The issues related to microphysical parametrization associated with cloud initialization were also discussed.

Application of Model Project Based Learning on Integrated Science in Water Pollution

NASA Astrophysics Data System (ADS)

Yamin, Y.; Permanasari, A.; Redjeki, S.; Sopandi, W.

2017-09-01

The function of this research was to analyze the influence model Project Based Learning (PjBl) on integrated science about the concept mastery for junior high school students. Method used for this research constitutes the quasi of experiment method. Population and sample for this research are the students junior high school in Bandung as many as two classes to be experiment and control class. The instrument that used for this research is the test concept mastery, assessment questionnaire of product and the questionnaire responses of the student about learning integrated science. Based on the result of this research get some data that with accomplishment the model of PjBl. Learning authority of integrated science can increase the concept mastery for junior high school students. The highest increase in the theme of pollution water is in the concept of mixtures and the separation method. The students give a positive response in learning of integrated science for the theme of pollution of the water used model PjBL with questionnaire of the opinion aspect in amount of 83.5%, the anxiety of the students in amount of 95.5%, the profit learning model of PjBL in amount of 96.25% and profit learning of integrated science in amount of 95.75%.

Development and application of a coupled bio-geochmical and hydrological model for point and non-point source river water pollution

NASA Astrophysics Data System (ADS)

Pohlert, T.

2007-12-01

The aim of this paper is to present recent developments of an integrated water- and N-balance model for the assessment of land use changes on water and N-fluxes for meso-scale river catchments. The semi-distributed water-balance model SWAT was coupled with algorithms of the bio-geochemical model DNDC as well as the model CropSyst. The new model that is further denoted as SWAT-N was tested with leaching data from a long- term lysimeter experiment as well as results from a 5-years sampling campaign that was conducted at the outlet of the meso-scale catchment of the River Dill (Germany). The model efficiency for N-load as well as the spatial representation of N-load along the river channel that was tested with results taken from longitudinal profiles show that the accuracy of the model has improved due to the integration of the aforementioned process-oriented models. After model development and model testing, SWAT-N was then used for the assessment of the EU agricultural policy (CAP reform) on land use change and consequent changes on N-fluxes within the Dill Catchment. giessen.de/geb/volltexte/2007/4531/

GRACE Detected Rise of Groundwater in the Sahelian Niger River Basin

NASA Astrophysics Data System (ADS)

Werth, S.; White, D.; Bliss, D. W.

2017-12-01

West African regions along the Niger River experience climate and land cover changes that affect hydrological processes and therewith the distribution of fresh water resources (WR). This study provides an investigation of long-term changes in terrestrial water storages (TWS) of the Niger River basin and its subregions by analyzing a decade of satellite gravity data from the Gravity Recovery and Climate Experiment (GRACE) mission. The location of large trends in TWS maps of differently processed GRACE solutions points to rising groundwater stocks. Soil moisture data from a global land surface model allow separating the effect of significantly increasing amount of WR from that of TWS variations. Surface water variations from a global water storage model validated with observations from altimetry data were applied to estimate the groundwater component in WR. For the whole Niger, a rise in groundwater stocks is estimated to be 93 ± 61 km3 between January 2003 and December 2013. A careful analysis of uncertainties in all data sets supports the significance of the groundwater rise. Our results confirm previous observations of rising water tables, indicating that effects of land cover changes on groundwater storage are relevant on basin scales. Areas with rising water storage are stocking a comfortable backup to mitigate possible future droughts and to deliver water to remote areas. This has implications for Niger water management strategies. Increasing groundwater recharges may be accompanied by reduction in water quality. This study helps to inform authority's decision to mitigate its negative impacts on local communities.

Integrated Model for the Acoustics of Sediments

DTIC Science & Technology

2013-09-30

1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Integrated Model for the Acoustics of Sediments...physics, and (3) the development and testing of sediment acoustic models through a series of at-sea experiments. APPROACH The approach may be...assess its impact on acoustic propagation and reverberation models . Practically, all underwater sediments are porous and water-permeable, therefore

Should we trust build-up/wash-off water quality models at the scale of urban catchments?

PubMed

Bonhomme, Céline; Petrucci, Guido

2017-01-01

Models of runoff water quality at the scale of an urban catchment usually rely on build-up/wash-off formulations obtained through small-scale experiments. Often, the physical interpretation of the model parameters, valid at the small-scale, is transposed to large-scale applications. Testing different levels of spatial variability, the parameter distributions of a water quality model are obtained in this paper through a Monte Carlo Markov Chain algorithm and analyzed. The simulated variable is the total suspended solid concentration at the outlet of a periurban catchment in the Paris region (2.3 km 2 ), for which high-frequency turbidity measurements are available. This application suggests that build-up/wash-off models applied at the catchment-scale do not maintain their physical meaning, but should be considered as "black-box" models. Copyright © 2016 Elsevier Ltd. All rights reserved.

Modeling and Simulations in Photoelectrochemical Water Oxidation: From Single Level to Multiscale Modeling.

PubMed

Zhang, Xueqing; Bieberle-Hütter, Anja

2016-06-08

This review summarizes recent developments, challenges, and strategies in the field of modeling and simulations of photoelectrochemical (PEC) water oxidation. We focus on water splitting by metal-oxide semiconductors and discuss topics such as theoretical calculations of light absorption, band gap/band edge, charge transport, and electrochemical reactions at the electrode-electrolyte interface. In particular, we review the mechanisms of the oxygen evolution reaction, strategies to lower overpotential, and computational methods applied to PEC systems with particular focus on multiscale modeling. The current challenges in modeling PEC interfaces and their processes are summarized. At the end, we propose a new multiscale modeling approach to simulate the PEC interface under conditions most similar to those of experiments. This approach will contribute to identifying the limitations at PEC interfaces. Its generic nature allows its application to a number of electrochemical systems. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Addressing water scarcity through limited irrigation cropping: Field experiments and modeling

USDA-ARS?s Scientific Manuscript database

Population growth in urbanizing areas such as the Front Range of Colorado has led to increased pressure to transfer water from agriculture to municipalities. In many cases this has led to complete dry up of productive irrigated lands. An option to complete dry-up is the practice of limited or defi...

Fine water spray for fire extinguishing. Phase 2: Turbine hood

NASA Astrophysics Data System (ADS)

Aune, P.; Wighus, R.; Drangsholt, G.; Stensaas, J. P.

1994-12-01

SINTEF has carried out tests of a Fine Water Spray fire suppression system intended to be used as a replacement for Halon systems in turbine hoods on offshore platforms operated by British Petroleum Norway. The tests were carried out in a 70 cu m full scale model representing a turbine hood of the Ula platform in the North Sea. A mock-up of a gas turbine was installed in the model. The scope of work in Phase 2 was to verify the efficiency of fire suppression in realistic fire scenarios using a Fine Water Spray system, and to find an optimum procedure for water application in a fire situation. Two reports have been made from the experiments in Phase 2, one Main Report, STF25 A94036, and the present Technical Report, STF25 A94037. The discussion and conclusions are given in the Main Report while this Technical Report gives a more thorough presentation of the experimental setup and methods used for calibration and calculation of measured values. In addition, a complete set of curves for each experiment is included.

Elastic spheres can walk on water.

PubMed

Belden, Jesse; Hurd, Randy C; Jandron, Michael A; Bower, Allan F; Truscott, Tadd T

2016-02-04

Incited by public fascination and engineering application, water-skipping of rigid stones and spheres has received considerable study. While these objects can be coaxed to ricochet, elastic spheres demonstrate superior water-skipping ability, but little is known about the effect of large material compliance on water impact physics. Here we show that upon water impact, very compliant spheres naturally assume a disk-like geometry and dynamic orientation that are favourable for water-skipping. Experiments and numerical modelling reveal that the initial spherical shape evolves as elastic waves propagate through the material. We find that the skipping dynamics are governed by the wave propagation speed and by the ratio of material shear modulus to hydrodynamic pressure. With these insights, we explain why softer spheres skip more easily than stiffer ones. Our results advance understanding of fluid-elastic body interaction during water impact, which could benefit inflatable craft modelling and, more playfully, design of elastic aquatic toys.

Elastic spheres can walk on water

PubMed Central

Belden, Jesse; Hurd, Randy C.; Jandron, Michael A.; Bower, Allan F.; Truscott, Tadd T.

2016-01-01

Incited by public fascination and engineering application, water-skipping of rigid stones and spheres has received considerable study. While these objects can be coaxed to ricochet, elastic spheres demonstrate superior water-skipping ability, but little is known about the effect of large material compliance on water impact physics. Here we show that upon water impact, very compliant spheres naturally assume a disk-like geometry and dynamic orientation that are favourable for water-skipping. Experiments and numerical modelling reveal that the initial spherical shape evolves as elastic waves propagate through the material. We find that the skipping dynamics are governed by the wave propagation speed and by the ratio of material shear modulus to hydrodynamic pressure. With these insights, we explain why softer spheres skip more easily than stiffer ones. Our results advance understanding of fluid-elastic body interaction during water impact, which could benefit inflatable craft modelling and, more playfully, design of elastic aquatic toys. PMID:26842860

Development of the Gecko (Pachydactylus turneri) Animal Model during Foton M-2 to Study Comparative Effects of Microgravity in Terrestrial and Aquatic Organisms

NASA Technical Reports Server (NTRS)

Almeida, E. A.; Roden, C.; Phillips, J. A.; Globus, R. K.; Searby, N.; Vercoutere, W.; Morey-Holton, E.; Gulimova, V.; Saveliev, S.; Tairbekov, M.;

Flume experimentation and simulation of bedrock channel processes

NASA Astrophysics Data System (ADS)

Thompson, Douglas; Wohl, Ellen

Flume experiments can provide cost effective, physically manageable miniature representations of complex bedrock channels. The inherent change in scale in such experiments requires a corresponding change in the scale of the forces represented in the flume system. Three modeling approaches have been developed that either ignore the scaling effects, utilize the change in scaled forces, or assume similarity of process between scales. An understanding of the nonlinear influence of a change in scale on all the forces involved is important to correctly analyze model results. Similarly, proper design and operation of flume experiments requires knowledge of the fundamental components of flume systems. Entrance and exit regions of the flume are used to provide good experimental conditions in the measurement region of the flume where data are collected. To insure reproducibility, large-scale turbulence must be removed in the head of the flume and velocity profiles must become fully developed in the entrance region. Water-surface slope and flow acceleration effects from downstream water-depth control must also be isolated in the exit region. Statistical design and development of representative channel substrate also influence model results in these systems. With proper experimental design, flumes may be used to investigate bedrock channel hydraulics, sediment-transport relations, and morphologic evolution. In particular, researchers have successfully used flume experiments to demonstrate the importance of turbulence and substrate characteristics in bedrock channel evolution. Turbulence often operates in a self perpetuating fashion, can erode bedrock walls with clear water and increase the mobility of sediment particles. Bedrock substrate influences channel evolution by offering varying resistance to erosion, controlling the location or type of incision and modifying the local influence of turbulence. An increased usage of scaled flume models may help to clarify the remaining uncertainties involving turbulence, channel substrate and bedrock channel evolution.

Accurate small and wide angle x-ray scattering profiles from atomic models of proteins and nucleic acids

NASA Astrophysics Data System (ADS)

Nguyen, Hung T.; Pabit, Suzette A.; Meisburger, Steve P.; Pollack, Lois; Case, David A.

2014-12-01

A new method is introduced to compute X-ray solution scattering profiles from atomic models of macromolecules. The three-dimensional version of the Reference Interaction Site Model (RISM) from liquid-state statistical mechanics is employed to compute the solvent distribution around the solute, including both water and ions. X-ray scattering profiles are computed from this distribution together with the solute geometry. We describe an efficient procedure for performing this calculation employing a Lebedev grid for the angular averaging. The intensity profiles (which involve no adjustable parameters) match experiment and molecular dynamics simulations up to wide angle for two proteins (lysozyme and myoglobin) in water, as well as the small-angle profiles for a dozen biomolecules taken from the BioIsis.net database. The RISM model is especially well-suited for studies of nucleic acids in salt solution. Use of fiber-diffraction models for the structure of duplex DNA in solution yields close agreement with the observed scattering profiles in both the small and wide angle scattering (SAXS and WAXS) regimes. In addition, computed profiles of anomalous SAXS signals (for Rb+ and Sr2+) emphasize the ionic contribution to scattering and are in reasonable agreement with experiment. In cases where an absolute calibration of the experimental data at q = 0 is available, one can extract a count of the excess number of waters and ions; computed values depend on the closure that is assumed in the solution of the Ornstein-Zernike equations, with results from the Kovalenko-Hirata closure being closest to experiment for the cases studied here.

Effects of Potamogeton crispus L.-bacteria interactions on the removal of phthalate acid esters from surface water.

PubMed

Chi, Jie; Gao, Jing

2015-01-01

To investigate the mechanism of submerged macrophyte-bacteria interactions on the removal of phthalic acid esters from surface water, experiments with and without Potamogeton crispus L. were performed. A two-compartment (i.e., water and plant) kinetic model was developed. The model adequately described the variation of dibutyl phthalate (DBP) and di-2-ethylhexyl phthalate (DEHP) in the plant-water system by providing the first-order rate constants of plant uptake (k1) and release (k2), microbial degradation in water (k3) and plant degradation (k4). During 10-d incubation, the presence of P. crispus enhanced the removal of DBP and DEHP from water by 6.3% and 22.4%. Compared with the experiment without P. crispus, biodegradation of DBP in water with P. crispus decreased by 8.3% because of plant uptake even though k3 increased by 30%. 21.4% of DBP transferred from water to plants, of which only small amount (5.1%) retained in the plant and the rest (94.9%) was degraded. Different from DBP, biodegradation of DEHP in water with P. crispus was a slightly higher than that without P. crispus. 25.5% of DEHP transferred from water to plants, of which a large portion (73.3%) retained in the plant and the rest (26.7%) was degraded. This finding reveals that the enhancement of DBP removal from surface water is mainly related to faster degradation in the plant, whereas it is mainly related to higher plant accumulation for DEHP. Copyright © 2014 Elsevier Ltd. All rights reserved.

An interoperability experiment for sharing hydrological rating tables

NASA Astrophysics Data System (ADS)

Lemon, D.; Taylor, P.; Sheahan, P.

2013-12-01

The increasing demand on freshwater resources is requiring authorities to produce more accurate and timely estimates of their available water. Calculation of continuous time-series of river discharge and storage volumes generally requires rating tables. These approximate relationships between two phenomena, such as river level and discharge, and allow us to produce continuous estimates of a phenomenon that may be impractical or impossible to measure directly. Standardised information models or access mechanisms for rating tables are required to support sharing and exchange of water flow data. An Interoperability Experiment (IE) is underway to test an information model that describes rating tables, the observations made to build these ratings, and river cross-section data. The IE is an initiative of the joint World Meteorological Organisation/Open Geospatial Consortium's Hydrology Domain Working Group (HydroDWG) and the model will be published as WaterML2.0 part 2. Interoperability Experiments (IEs) are low overhead, multiple member projects that are run under the OGC's interoperability program to test existing and emerging standards. The HydroDWG has previously run IEs to test early versions of OGC WaterML2.0 part 1 - timeseries. This IE is focussing on two key exchange scenarios: Sharing rating tables and gauging observations between water agencies. Through the use of standard OGC web services, rating tables and associated data will be made available from water agencies. The (Australian) Bureau of Meteorology will retrieve rating tables on-demand from water authorities, allowing the Bureau to run conversions of data within their own systems. Exposing rating tables and gaugings for online analysis and educational purposes. A web client will be developed to enable exploration and visualization of rating tables, gaugings and related metadata for monitoring points. The client gives a quick view into available rating tables, their periods of applicability and the standard deviation of observations against the relationship. An example of this client running can be seen at the link provided. The result of the IE will form the basis for the standardisation of WaterML2.0 part 2. The use of the standard will lead to increased transparency and accessibility of rating tables, while also improving general understanding of this important hydrological concept.

Diurnal trends in methylmercury concentration in a wetland adjacent to Great Salt Lake, Utah, USA

USGS Publications Warehouse

Naftz, D.L.; Cederberg, J.R.; Krabbenhoft, D.P.; Beisner, K.R.; Whitehead, J.; Gardberg, J.

2011-01-01

A 24-h field experiment was conducted during July 2008 at a wetland on the eastern shore of Great Salt Lake (GSL) to assess the diurnal cycling of methylmercury (MeHg). Dissolved (<0.45??m) MeHg showed a strong diurnal variation with consistently decreasing concentrations during daylight periods and increasing concentrations during non-daylight periods. The proportion of MeHg relative to total Hg in the water column consistently decreased with increasing sunlight duration, indicative of photodegradation. During the field experiment, measured MeHg photodegradation rates ranged from 0.02 to 0.06ngL-1h-1. Convective overturn of the water column driven by nighttime cooling of the water surface was hypothesized as the likely mechanism to replace the MeHg in the water column lost via photodegradation processes. A hydrodynamic model of the wetland successfully simulated convective overturn of the water column during the field experiment. Study results indicate that daytime monitoring of selected wetlands surrounding GSL may significantly underestimate the MeHg content in the water column. Wetland managers should consider practices that maximize the photodegradation of MeHg during daylight periods. ?? 2011.

Using the Sandia Z Machine to Probe Water at Planetary Conditions: Redefining the Properties of Water in the Ice Giants

NASA Astrophysics Data System (ADS)

Knudson, M. D.; Desjarlais, M.; Lemke, R.; Mattsson, T.; French, M.; Nettelmann, N.; Redmer, R.

2012-12-01

Recently, there has been a tremendous increase in the number of identified extrasolar planetary systems. Our understanding of their formation is tied to exoplanet internal structure models, which rely upon equation of state (EOS) models of light elements and compounds such as water at multi-Mbar pressure conditions. For the past decade, a large, interdisciplinary team at Sandia National Laboratories has been refining the Z Machine (20+ MA and 10+ MGauss) into a mature, robust, and precise platform for material dynamics experiments in the multi-Mbar pressure regime. In particular, significant effort has gone into effectively coupling condensed matter theory, magneto-hydrodynamic simulation, and electromagnetic modeling to produce a fully self-consistent simulation capability able to very accurately predict the performance of the Z machine and various experimental load configurations. This capability has been instrumental in the ability to develop experimental platforms to routinely perform magnetic ramp compression experiments to over 4 Mbar, and magnetically accelerate flyer plates to over 40 km/s, creating over 20 Mbar impact pressures. Furthermore, a strong tie has been developed between the condensed matter theory and the experimental program. This coupling has been proven time and again to be extremely fruitful, with the capability of both theory and experiment being challenged and advanced through this close interrelationship. This presentation will provide a short overview of the material dynamics platform and discuss in more detail the use of Z to perform extreme material dynamics studies with unprecedented accuracy on water in support of basic science, planetary astrophysics, and the emerging field of high energy density laboratory physics. It was found that widely used EOSs for water are much too compressible (up to 30 percent) at pressures and temperatures relevant to planetary interiors. Furthermore, it is shown that the behavior of water at these conditions, including its reflectivity and isentropic response, is well-described by an EOS for water based on recent first-principles calculations. These findings advocate that this water model be used as the standard for modeling Neptune, Uranus, and "hot Neptune" exoplanets, and should improve our understanding of these types of planetary systems. Sandia National Laboratories is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract No. DE-AC04-94AL85000.

Bacteriophage PRD1 batch experiments to study attachment, detachment and inactivation processes.

PubMed

Sadeghi, Gholamreza; Schijven, Jack F; Behrends, Thilo; Hassanizadeh, S Majid; van Genuchten, Martinus Th

2013-09-01

Knowledge of virus removal in subsurface environments is pivotal for assessing the risk of viral contamination of water resources and developing appropriate protection measures. Columns packed with sand are frequently used to quantify attachment, detachment and inactivation rates of viruses. Since column transport experiments are very laborious, a common alternative is to perform batch experiments where usually one or two measurements are done assuming equilibrium is reached. It is also possible to perform kinetic batch experiments. In that case, however, it is necessary to monitor changes in the concentration with time. This means that kinetic batch experiments will be almost as laborious as column experiments. Moreover, attachment and detachment rate coefficients derived from batch experiments may differ from those determined using column experiments. The aim of this study was to determine the utility of kinetic batch experiments and investigate the effects of different designs of the batch experiments on estimated attachment, detachment and inactivation rate coefficients. The experiments involved various combinations of container size, sand-water ratio, and mixing method (i.e., rolling or tumbling by pivoting the tubes around their horizontal or vertical axes, respectively). Batch experiments were conducted with clean quartz sand, water at pH 7 and ionic strength of 20 mM, and using the bacteriophage PRD1 as a model virus. Values of attachment, detachment and inactivation rate coefficients were found by fitting an analytical solution of the kinetic model equations to the data. Attachment rate coefficients were found to be systematically higher under tumbling than under rolling conditions because of better mixing and more efficient contact of phages with the surfaces of the sand grains. In both mixing methods, more sand in the container yielded higher attachment rate coefficients. A linear increase in the detachment rate coefficient was observed with increased solid-water ratio using tumbling method. Given the differences in the attachment rate coefficients, and assuming the same sticking efficiencies since chemical conditions of the batch and column experiments were the same, our results show that collision efficiencies of batch experiments are not the same as those of column experiments. Upscaling of the attachment rate from batch to column experiments hence requires proper understanding of the mixing conditions. Because batch experiments, in which the kinetics are monitored, are as laborious as column experiments, there seems to be no major advantage in performing batch instead of column experiments. Copyright © 2013 Elsevier B.V. All rights reserved.

Laboratory meter-scale seismic monitoring of varying water levels in granular media

NASA Astrophysics Data System (ADS)

Pasquet, S.; Bodet, L.; Bergamo, P.; Guérin, R.; Martin, R.; Mourgues, R.; Tournat, V.

2016-12-01

Laboratory physical modelling and non-contacting ultrasonic techniques are frequently proposed to tackle theoretical and methodological issues related to geophysical prospecting. Following recent developments illustrating the ability of seismic methods to image spatial and/or temporal variations of water content in the vadose zone, we developed laboratory experiments aimed at testing the sensitivity of seismic measurements (i.e., pressure-wave travel times and surface-wave phase velocities) to water saturation variations. Ultrasonic techniques were used to simulate typical seismic acquisitions on small-scale controlled granular media presenting different water levels. Travel times and phase velocity measurements obtained at the dry state were validated with both theoretical models and numerical simulations and serve as reference datasets. The increasing water level clearly affects the recorded wave field in both its phase and amplitude, but the collected data cannot yet be inverted in the absence of a comprehensive theoretical model for such partially saturated and unconsolidated granular media. The differences in travel time and phase velocity observed between the dry and wet models show patterns that are interestingly coincident with the observed water level and depth of the capillary fringe, thus offering attractive perspectives for studying soil water content variations in the field.

On the implications of aerosol liquid water and phase ...

EPA Pesticide Factsheets

Organic compounds and liquid water are major aerosol constituents in the southeast United States (SE US). Water associated with inorganic constituents (inorganic water) can contribute to the partitioning medium for organic aerosol when relative humidities or organic matter to organic carbon (OM ∕ OC) ratios are high such that separation relative humidities (SRH) are below the ambient relative humidity (RH). As OM ∕ OC ratios in the SE US are often between 1.8 and 2.2, organic aerosol experiences both mixing with inorganic water and separation from it. Regional chemical transport model simulations including inorganic water (but excluding water uptake by organic compounds) in the partitioning medium for secondary organic aerosol (SOA) when RH  >  SRH led to increased SOA concentrations, particularly at night. Water uptake to the organic phase resulted in even greater SOA concentrations as a result of a positive feedback in which water uptake increased SOA, which further increased aerosol water and organic aerosol. Aerosol properties, such as the OM ∕ OC and hygroscopicity parameter (κorg), were captured well by the model compared with measurements during the Southern Oxidant and Aerosol Study (SOAS) 2013. Organic nitrates from monoterpene oxidation were predicted to be the least water-soluble semivolatile species in the model, but most biogenically derived semivolatile species in the Community Multiscale Air Quality (CMAQ) model were hig

Fully coupled approach to modeling shallow water flow, sediment transport, and bed evolution in rivers

NASA Astrophysics Data System (ADS)

Li, Shuangcai; Duffy, Christopher J.

2011-03-01

Our ability to predict complex environmental fluid flow and transport hinges on accurate and efficient simulations of multiple physical phenomenon operating simultaneously over a wide range of spatial and temporal scales, including overbank floods, coastal storm surge events, drying and wetting bed conditions, and simultaneous bed form evolution. This research implements a fully coupled strategy for solving shallow water hydrodynamics, sediment transport, and morphological bed evolution in rivers and floodplains (PIHM_Hydro) and applies the model to field and laboratory experiments that cover a wide range of spatial and temporal scales. The model uses a standard upwind finite volume method and Roe's approximate Riemann solver for unstructured grids. A multidimensional linear reconstruction and slope limiter are implemented, achieving second-order spatial accuracy. Model efficiency and stability are treated using an explicit-implicit method for temporal discretization with operator splitting. Laboratory-and field-scale experiments were compiled where coupled processes across a range of scales were observed and where higher-order spatial and temporal accuracy might be needed for accurate and efficient solutions. These experiments demonstrate the ability of the fully coupled strategy in capturing dynamics of field-scale flood waves and small-scale drying-wetting processes.

[Effect of Novonukutskaya mineral water extracts on the clinical course of wound disease and wound healing in experiment].

PubMed

Malyshkina, N A; Iushkov, G G; Benemanskiĭ, V V; Shpeĭzer, G M; Khutorianskiĭ, V A; Smirnov, A I; Rodionova, V A; Mineeva, L A

2010-01-01

The objective of the present work was to study the wound-healing potential of the new preparation, Extramin (a 32% ethanol extract of organic substances from Novonukutskaya mineral water) in a series of experiments on a model of chemical burns in rabbits. The wound healing process was monitored based on biochemical, hematiological, and morphological indicators. Analysis of the results allows for the conclusion that Extramin is a powerful stimulator of the wound-healing processes and can be recommended for further clinical studies.

Household's willingness to pay for heterogeneous attributes of drinking water quality and services improvement: an application of choice experiment

NASA Astrophysics Data System (ADS)

Dauda, Suleiman Alhaji; Yacob, Mohd Rusli; Radam, Alias

2015-09-01

The service of providing good quality of drinking water can greatly improve the lives of the community and maintain a normal health standard. For a large number of population in the world, specifically in the developing countries, the availability of safe water for daily sustenance is none. Damaturu is the capital of Yobe State, Nigeria. It hosts a population of more than two hundred thousand, yet only 45 % of the households are connected to the network of Yobe State Water Corporation's pipe borne water services; this has led people to source for water from any available source and thus, exposed them to the danger of contracting waterborne diseases. In order to address the problem, Yobe State Government has embarked on the construction of a water treatment plant with a capacity and facility to improve the water quality and connect the town with water services network. The objectives of this study are to assess the households' demand preferences of the heterogeneous water attributes in Damaturu, and to estimate their marginal willingness to pay, using mixed logit model in comparison with conditional logit model. A survey of 300 households randomly sampled indicated that higher education greatly influenced the households' WTP decisions. The most significant variable from both of the models is TWQ, which is MRS that rates the water quality from the level of satisfactory to very good. 219 % in simple model is CLM, while 126 % is for the interaction model. As for MLM, 685 % is for the simple model and 572 % is for the interaction model. Estimate of MLM has more explanatory powers than CLM. Essentially, this finding can help the government in designing cost-effective management and efficient tariff structure.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Uchibori, Akihiro; Kurihara, Akikazu; Ohshima, Hiroyuki

A multiphysics analysis system for sodium-water reaction phenomena in a steam generator of sodium-cooled fast reactors was newly developed. The analysis system consists of the mechanistic numerical analysis codes, SERAPHIM, TACT, and RELAP5. The SERAPHIM code calculates the multicomponent multiphase flow and sodium-water chemical reaction caused by discharging of pressurized water vapor. Applicability of the SERAPHIM code was confirmed through the analyses of the experiment on water vapor discharging in liquid sodium. The TACT code was developed to calculate heat transfer from the reacting jet to the adjacent tube and to predict the tube failure occurrence. The numerical models integratedmore » into the TACT code were verified through some related experiments. The RELAP5 code evaluates thermal hydraulic behavior of water inside the tube. The original heat transfer correlations were corrected for the tube rapidly heated by the reacting jet. The developed system enables evaluation of the wastage environment and the possibility of the failure propagation.« less

Dependence of flow and transport through the Williamson River Delta, Upper Klamath Lake, Oregon, on wind, river inflow, and lake elevation

USGS Publications Warehouse

Wood, Tamara M.

2012-01-01

The hydrodynamic model of Upper Klamath and Agency Lakes, Oregon, was used to run 384 realizations of a numerical tracer experiment in order to understand the relative effects of wind, lake elevation, and Williamson River inflow on flow and transport (the movement of water and passively transported constituents) through the Williamson River Delta. Significant findings from this study include: * The replacement rate of water increased in Tulana and Goose Bay with increasing lake elevation, Williamson River inflow, and wind speed. * The fraction of Williamson River inflow passing through either side of the Delta increased with lake elevation and Williamson River inflow. * The partial replacement rate of water in Goose Bay with water from the Williamson River increased with wind speed. * The partial replacement rate of water in Tulana with water from the Williamson River decreased with wind speed. * Strong wind forcing at the water surface caused more of the Williamson River inflow to pass through Goose Bay than through Tulana. * Westerly to northwesterly winds result in more of the Williamson River inflow passing through the Goose Bay side of the Delta than through the Tulana side. * Regression models developed from the tracer experiments can be used to quantify the dependencies between transport and the independent variables to obtain rough estimates of useful quantities such as residence time and steady-state solute concentrations.

A Simple ab initio Model for the Hydrated Electron that Matches Experiment

PubMed Central

Kumar, Anil; Walker, Jonathan A.; Bartels, David M.; Sevilla, Michael D.

2015-01-01

Since its discovery over 50 years ago, the “structure” and properties of the hydrated electron has been a subject for wonderment and also fierce debate. In the present work we seriously explore a minimal model for the aqueous electron, consisting of a small water anion cluster embedded in a polarized continuum, using several levels of ab initio calculation and basis set. The minimum energy zero “Kelvin” structure found for any 4-water (or larger) anion cluster, at any post-Hartree-Fock theory level, is very similar to a recently reported embedded-DFT-in-classical-water-MD simulation (UMJ: Uhlig, Marsalek, and Jungwirth, Journal of Physical Chemistry Letters 2012, 3, 3071-5), with four OH bonds oriented toward the maximum charge density in a small central “void”. The minimum calculation with just four water molecules does a remarkably good job of reproducing the resonance Raman properties, the radius of gyration derived from the optical spectrum, the vertical detachment energy, and the hydration free energy. For the first time we also successfully calculate the EPR g-factor and (low temperature ice) hyperfine couplings. The simple tetrahedral anion cluster model conforms very well to experiment, suggesting it does in fact represent the dominant structural motif of the hydrated electron. PMID:26275103

Modeling preferential water flow and solute transport in unsaturated soil using the active region model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sheng, F.; Wang, K.; Zhang, R.

2009-03-15

Preferential flow and solute transport are common processes in the unsaturated soil, in which distributions of soil water content and solute concentrations are often characterized as fractal patterns. An active region model (ARM) was recently proposed to describe the preferential flow and transport patterns. In this study, ARM governing equations were derived to model the preferential soil water flow and solute transport processes. To evaluate the ARM equations, dye infiltration experiments were conducted, in which distributions of soil water content and Cl{sup -} concentration were measured. Predicted results using the ARM and the mobile-immobile region model (MIM) were compared withmore » the measured distributions of soil water content and Cl{sup -} concentration. Although both the ARM and the MIM are two-region models, they are fundamental different in terms of treatments of the flow region. The models were evaluated based on the modeling efficiency (ME). The MIM provided relatively poor prediction results of the preferential flow and transport with negative ME values or positive ME values less than 0.4. On the contrary, predicted distributions of soil water content and Cl- concentration using the ARM agreed reasonably well with the experimental data with ME values higher than 0.8. The results indicated that the ARM successfully captured the macroscopic behavior of preferential flow and solute transport in the unsaturated soil.« less

Estimation of bathymetric depth and slope from data assimilation of swath altimetry into a hydrodynamic model

NASA Astrophysics Data System (ADS)

Durand, Michael; Andreadis, Konstantinos M.; Alsdorf, Douglas E.; Lettenmaier, Dennis P.; Moller, Delwyn; Wilson, Matthew

2008-10-01

The proposed Surface Water and Ocean Topography (SWOT) mission would provide measurements of water surface elevation (WSE) for characterization of storage change and discharge. River channel bathymetry is a significant source of uncertainty in estimating discharge from WSE measurements, however. In this paper, we demonstrate an ensemble-based data assimilation (DA) methodology for estimating bathymetric depth and slope from WSE measurements and the LISFLOOD-FP hydrodynamic model. We performed two proof-of-concept experiments using synthetically generated SWOT measurements. The experiments demonstrated that bathymetric depth and slope can be estimated to within 3.0 microradians or 50 cm, respectively, using SWOT WSE measurements, within the context of our DA and modeling framework. We found that channel bathymetry estimation accuracy is relatively insensitive to SWOT measurement error, because uncertainty in LISFLOOD-FP inputs (such as channel roughness and upstream boundary conditions) is likely to be of greater magnitude than measurement error.

Impact of Aquifer Heterogeneities on Autotrophic Denitrification.

NASA Astrophysics Data System (ADS)

McCarthy, A.; Roques, C.; Selker, J. S.; Istok, J. D.; Pett-Ridge, J. C.

2015-12-01

Nitrate contamination in groundwater is a big challenge that will need to be addressed by hydrogeologists throughout the world. With a drinking water standard of 10mg/L of NO3-, innovative techniques will need to be pursued to ensure a decrease in drinking water nitrate concentration. At the pumping site scale, the influence and relationship between heterogeneous flow, mixing, and reactivity is not well understood. The purpose of this project is to incorporate both physical and chemical modeling techniques to better understand the effect of aquifer heterogeneities on autotrophic denitrification. We will investigate the link between heterogeneous hydraulic properties, transport, and the rate of autotrophic denitrification. Data collected in previous studies in laboratory experiments and pumping site scale experiments will be used to validate the models. The ultimate objective of this project is to develop a model in which such coupled processes are better understood resulting in best management practices of groundwater.

Fluoride and phosphate release from carbonate-rich fluorapatite during managed aquifer recharge

NASA Astrophysics Data System (ADS)

Schafer, David; Donn, Michael; Atteia, Olivier; Sun, Jing; MacRae, Colin; Raven, Mark; Pejcic, Bobby; Prommer, Henning

2018-07-01

Managed aquifer recharge (MAR) is increasingly used as a water management tool to enhance water availability and to improve water quality. Until now, however, the risk of fluoride release during MAR with low ionic strength injectate has not been recognised or examined. In this study we analyse and report the mobilisation of fluoride (up to 58 μM) and filterable reactive phosphorus (FRP) (up to 55 μM) during a field groundwater replenishment experiment in which highly treated, deionised wastewater (average TDS 33 mg/L) was injected into a siliciclastic Cretaceous aquifer. In the field experiment, maximum concentrations, which coincided with a rise in pH, exceeded background groundwater concentrations by an average factor of 3.6 for fluoride and 24 for FRP. The combined results from the field experiment, a detailed mineralogical characterisation and geochemical modelling suggested carbonate-rich fluorapatite (CFA: Ca10(PO4)5(CO3,F)F2) to be the most likely source of fluoride and phosphate release. An anoxic batch experiment with powdered CFA-rich nodules sourced from the target aquifer and aqueous solutions of successively decreasing ionic strength closely replicated the field-observed fluoride and phosphate behaviour. Based on the laboratory experiment and geochemical modelling, we hypothesise that the release of fluoride and phosphate results from the incongruent dissolution of CFA and the simultaneous formation of a depleted layer that has hydrated di-basic calcium phosphate (CaHPO4·nH2O) composition at the CFA-water interface. Disequilibrium caused by calcium removal following breakthrough of the deionised injectate triggered the release of fluoride and phosphate. Given the increasing use of highly treated, deionised water for MAR and the ubiquitous presence of CFA and fluorapatite (Ca10(PO4)6F2) in aquifer settings worldwide, the risk of fluoride and phosphate release needs to be considered in the MAR design process.

Dynamics of water confined in lyotropic liquid crystals: Molecular dynamics simulations of the dynamic structure factor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mantha, Sriteja; Yethiraj, Arun

2016-02-24

The properties of water under confinement are of practical and fundamental interest. Here in this work we study the properties of water in the self-assembled lyotropic phases of gemini surfactants with a focus on testing the standard analysis of quasi-elastic neutron scattering (QENS) experiments. In QENS experiments the dynamic structure factor is measured and fit to models to extract the translational diffusion constant, D T , and rotational relaxation time, τ R. We test this procedure by using simulation results for the dynamic structure factor, extracting the dynamic parameters from the fit as is typically done in experiments, and comparingmore » the values to those directly measured in the simulations. We find that the decoupling approximation, where the intermediate scattering function is assumed to be a product of translational and rotational contributions, is quite accurate. The jump-diffusion and isotropic rotation models, however, are not accurate when the degree of confinement is high. In particular, the exponential approximations for the intermediate scattering function fail for highly confined water and the values of D T and τ R can differ from the measured value by as much as a factor of two. Other models have more fit parameters, however, and with the range of energies and wave-vectors accessible to QENS, the typical analysis appears to be the best choice. In the most confined lamellar phase, the dynamics are sufficiently slow that QENS does not access a large enough time scale and neutron spin echo measurements would be a valuable technique in addition to QENS.« less

'Unconventional' experiments in biology and medicine with optimized design based on quantum-like correlations.

PubMed

Beauvais, Francis

2017-02-01

In previous articles, a description of 'unconventional' experiments (e.g. in vitro or clinical studies based on high dilutions, 'memory of water' or homeopathy) using quantum-like probability was proposed. Because the mathematical formulations of quantum logic are frequently an obstacle for physicians and biologists, a modified modeling that rests on classical probability is described in the present article. This modeling is inspired from a relational interpretation of quantum physics that applies not only to microscopic objects, but also to macroscopic structures, including experimental devices and observers. In this framework, any outcome of an experiment is not an absolute property of the observed system as usually considered but is expressed relatively to an observer. A team of interacting observers is thus described from an external view point based on two principles: the outcomes of experiments are expressed relatively to each observer and the observers agree on outcomes when they interact with each other. If probability fluctuations are also taken into account, correlations between 'expected' and observed outcomes emerge. Moreover, quantum-like correlations are predicted in experiments with local blind design but not with centralized blind design. No assumption on 'memory' or other physical modification of water is necessary in the present description although such hypotheses cannot be formally discarded. In conclusion, a simple modeling of 'unconventional' experiments based on classical probability is now available and its predictions can be tested. The underlying concepts are sufficiently intuitive to be spread into the homeopathy community and beyond. It is hoped that this modeling will encourage new studies with optimized designs for in vitro experiments and clinical trials. Copyright © 2017 The Faculty of Homeopathy. Published by Elsevier Ltd. All rights reserved.

Uranium plume persistence impacted by hydrologic and geochemical heterogeneity in the groundwater and river water interaction zone of Hanford site

NASA Astrophysics Data System (ADS)

Chen, X.; Zachara, J. M.; Vermeul, V. R.; Freshley, M.; Hammond, G. E.

2015-12-01

The behavior of a persistent uranium plume in an extended groundwater- river water (GW-SW) interaction zone at the DOE Hanford site is dominantly controlled by river stage fluctuations in the adjacent Columbia River. The plume behavior is further complicated by substantial heterogeneity in physical and geochemical properties of the host aquifer sediments. Multi-scale field and laboratory experiments and reactive transport modeling were integrated to understand the complex plume behavior influenced by highly variable hydrologic and geochemical conditions in time and space. In this presentation we (1) describe multiple data sets from field-scale uranium adsorption and desorption experiments performed at our experimental well-field, (2) develop a reactive transport model that incorporates hydrologic and geochemical heterogeneities characterized from multi-scale and multi-type datasets and a surface complexation reaction network based on laboratory studies, and (3) compare the modeling and observation results to provide insights on how to refine the conceptual model and reduce prediction uncertainties. The experimental results revealed significant spatial variability in uranium adsorption/desorption behavior, while modeling demonstrated that ambient hydrologic and geochemical conditions and heterogeneities in sediment physical and chemical properties both contributed to complex plume behavior and its persistence. Our analysis provides important insights into the characterization, understanding, modeling, and remediation of groundwater contaminant plumes influenced by surface water and groundwater interactions.

EXPERIMENTAL EVALUATION OF THE THERMAL PERFORMANCE OF A WATER SHIELD FOR A SURFACE POWER REACTOR

DOE Office of Scientific and Technical Information (OSTI.GOV)

REID, ROBERT S.; PEARSON, J. BOSIE; STEWART, ERIC T.

2007-01-16

Water based reactor shielding is being investigated for use on initial lunar surface power systems. A water shield may lower overall cost (as compared to development cost for other materials) and simplify operations in the setup and handling. The thermal hydraulic performance of the shield is of significant interest. The mechanism for transferring heat through the shield is natural convection. Natural convection in a 100 kWt lunar surface reactor shield design is evaluated with 2 kW power input to the water in the Water Shield Testbed (WST) at the NASA Marshall Space Flight Center. The experimental data from the WSTmore » is used to validate a CFD model. Performance of the water shield on the lunar surface is then predicted with a CFD model anchored to test data. The experiment had a maximum water temperature of 75 C. The CFD model with 1/6-g predicts a maximum water temperature of 88 C with the same heat load and external boundary conditions. This difference in maximum temperature does not greatly affect the structural design of the shield, and demonstrates that it may be possible to use water for a lunar reactor shield.« less

Assessment of the contamination of drinking water supply wells by pesticides from surface water resources using a finite element reactive transport model and global sensitivity analysis techniques

NASA Astrophysics Data System (ADS)

Malaguerra, Flavio; Albrechtsen, Hans-Jørgen; Binning, Philip John

2013-01-01

SummaryA reactive transport model is employed to evaluate the potential for contamination of drinking water wells by surface water pollution. The model considers various geologic settings, includes sorption and degradation processes and is tested by comparison with data from a tracer experiment where fluorescein dye injected in a river is monitored at nearby drinking water wells. Three compounds were considered: an older pesticide MCPP (Mecoprop) which is mobile and relatively persistent, glyphosate (Roundup), a newer biodegradable and strongly sorbing pesticide, and its degradation product AMPA. Global sensitivity analysis using the Morris method is employed to identify the dominant model parameters. Results show that the characteristics of clay aquitards (degree of fracturing and thickness), pollutant properties and well depths are crucial factors when evaluating the risk of drinking water well contamination from surface water. This study suggests that it is unlikely that glyphosate in streams can pose a threat to drinking water wells, while MCPP in surface water can represent a risk: MCPP concentration at the drinking water well can be up to 7% of surface water concentration in confined aquifers and up to 10% in unconfined aquifers. Thus, the presence of confining clay aquitards may not prevent contamination of drinking water wells by persistent compounds in surface water. Results are consistent with data on pesticide occurrence in Denmark where pesticides are found at higher concentrations at shallow depths and close to streams.

The influence of initial and surface boundary conditions on a model-generated January climatology

NASA Technical Reports Server (NTRS)

Wu, K. F.; Spar, J.

1981-01-01

The influence on a model-generated January climate of various surface boundary conditions, as well as initial conditions, was studied by using the GISS coarse-mesh climate model. Four experiments - two with water planets, one with flat continents, and one with mountains - were used to investigate the effects of initial conditions, and the thermal and dynamical effects of the surface on the model generated-climate. However, climatological mean zonal-symmetric sea surface temperature is used in all four runs over the model oceans. Moreover, zero ground wetness and uniform ground albedo except for snow are used in the last experiments.

Reuse rate of treated wastewater in water reuse system.

PubMed

Fan, Yao-bo; Yang, Wen-bo; Li, Gang; Wu, Lin-lin; Wei, Yuan-song

2005-01-01

A water quality model for water reuse was made by mathematics induction. The relationship among the reuse rate of treated wastewater (R), pollutant concentration of reused water (Cs), pollutant concentration of influent (C0), removal efficiency of pollutant in wastewater (E), and the standard of reuse water were discussed in this study. According to the experiment result of a toilet wastewater treatment and reuse with membrane bioreactors, R would be set at less than 40%, on which all the concemed parameters could meet with the reuse water standards. To raise R of reuse water in the toilet, an important way was to improve color removal of the wastewater.

Short-term responses of leaf growth rate to water deficit scale up to whole-plant and crop levels: an integrated modelling approach in maize.

PubMed

Chenu, Karine; Chapman, Scott C; Hammer, Graeme L; McLean, Greg; Salah, Halim Ben Haj; Tardieu, François

2008-03-01

Physiological and genetic studies of leaf growth often focus on short-term responses, leaving a gap to whole-plant models that predict biomass accumulation, transpiration and yield at crop scale. To bridge this gap, we developed a model that combines an existing model of leaf 6 expansion in response to short-term environmental variations with a model coordinating the development of all leaves of a plant. The latter was based on: (1) rates of leaf initiation, appearance and end of elongation measured in field experiments; and (2) the hypothesis of an independence of the growth between leaves. The resulting whole-plant leaf model was integrated into the generic crop model APSIM which provided dynamic feedback of environmental conditions to the leaf model and allowed simulation of crop growth at canopy level. The model was tested in 12 field situations with contrasting temperature, evaporative demand and soil water status. In observed and simulated data, high evaporative demand reduced leaf area at the whole-plant level, and short water deficits affected only leaves developing during the stress, either visible or still hidden in the whorl. The model adequately simulated whole-plant profiles of leaf area with a single set of parameters that applied to the same hybrid in all experiments. It was also suitable to predict biomass accumulation and yield of a similar hybrid grown in different conditions. This model extends to field conditions existing knowledge of the environmental controls of leaf elongation, and can be used to simulate how their genetic controls flow through to yield.

ESTABLISHMENT OF A GROUNDWATER RESEARCH DATA CENTER FOR VALIDATION OF SUBSURFACE FLOW AND TRANSPORT MODELS

EPA Science Inventory

The International Ground Water Modeling Center has established a Groundwater Research Data Center that provides information on datasets resulting from publicly funded field experiments and related bench studies in soil and groundwater pollution and distributes datasets for tes...

THE ESTABLISHMENT OF A GROUNDWATER RESEARCH DATA CENTER FOR VALIDATION OF SUBSURFACE FLOW AND TRANSPORT MODELS

EPA Science Inventory

The International Ground Water Modeling Center has established a Groundwater Research Data Center which provides information on research datasets resulting from publicly funded field experiments regarding soil and groundwater pollution and related laboratory bench studies, and wh...

Investigating Nitrogen Pollution: Activities and Models.

ERIC Educational Resources Information Center

Green Teacher, 2000

2000-01-01

Introduces activities on nitrogen, nitrogen pollution from school commuters, nitrogen response in native and introduced species, and nutrient loading models. These activities help students determine the nitrogen contribution from their parents' cars, test native plant responses to nitrogen, and experiment with the results of removing water from…

Linking the physical and the socio-economic compartments of an integrated water and land use management model on a river basin scale using an object-oriented water supply model

NASA Astrophysics Data System (ADS)

Barthel, Roland; Nickel, Darla; Meleg, Alejandro; Trifkovic, Aleksandar; Braun, Juergen

Within the framework of the research project ‘GLOWA-Danube’, a model of the water supply sector has been developed. GLOWA-Danube investigates long-term changes in the water cycle of the Upper Danube river basin in light of global change. For this purpose, the decision support system DANUBIA, comprising 15 fully coupled models, has been developed. Within DANUBIA the water supply model (‘WaterSupply’) forms the link between various physical models determining water quality and availability and several socio-economic models determining water consumption and demand. Having a central focus on public drinking water supply, its purpose is to correctly simulate the present day system of water extraction and distribution and the related costs, but also to allow meaningful response to possible future changes of boundary conditions, first and foremost changes in water demand or water availability and quality. Response mechanisms are also envisioned for changes in political and economic boundary conditions, and advances in technology. The model will be used locate critical regions which could experience water stress in the future, but does not aim to find the appropriate solutions or to predict the optimal organisation of water supply in the Danube Basin under such changing conditions. In the object-oriented model structure, both water supply companies (WSC) and communities are represented by main classes. Both classes have a limited view and knowledge of their environment. A community knows where and how much water is consumed and from which WSC it is served. A WSC possesses information regarding extraction sites and water rights, raw water quality and potential collaborating WSC. The WSC can perform actions that are different from ‘business as usual’. These deviations from their usual behaviour can be interpreted by decision makers but should not be regarded as a replacement for the decision-making process itself. The model is conceptualised using object-oriented concepts of the Unified Modelling Language (UML) and is implemented in JAVA. This short overview is meant to answer key questions such as why and how WaterSupply was implemented, what is unique and new about the model and what are the general lessons learned and the added value with regard to integrated modelling on a river basin scale. It is obvious that in the attempt to answer these questions it is not possible to satisfy experts from all the relevant related fields, which include computer sciences, economy, behavioural science and not least water supply engineering and hydrology.

Presenting the Rain-Sea Interaction Facility

NASA Technical Reports Server (NTRS)

Bliven, Larry F.; Elfouhaily, Tonas M.

1993-01-01

The new Rain-Sea Interaction Facility (RSIF) was established at GSFC/WFF and the first finds are presented. The unique feature of this laboratory is the ability to systematically study microwave scattering from a water surface roughened by artificial rain, for which the droplets are at terminal velocity. The fundamental instruments and systems (e.g., the rain simulator, scatterometers, and surface elevation probes) were installed and evaluated during these first experiments - so the majority of the data were obtained with the rain simulator at 1 m above the water tank. From these initial experiments, three new models were proposed: the square-root function for NCS vs. R, the log Gaussian model for ring-wave elevation frequency spectrum, and the Erland probability density distribution for back scattered power. Rain rate is the main input for these models, although the coefficients may be dependent upon other factors (drop-size distribution, fall velocity, radar configuration, etc.). The facility is functional and we foresee collaborative studies with investigators who are engaged in measuring and modeling rain-sea interaction processes.

Kinetic model of water disinfection using peracetic acid including synergistic effects.

PubMed

Flores, Marina J; Brandi, Rodolfo J; Cassano, Alberto E; Labas, Marisol D

2016-01-01

The disinfection efficiencies of a commercial mixture of peracetic acid against Escherichia coli were studied in laboratory scale experiments. The joint and separate action of two disinfectant agents, hydrogen peroxide and peracetic acid, were evaluated in order to observe synergistic effects. A kinetic model for each component of the mixture and for the commercial mixture was proposed. Through simple mathematical equations, the model describes different stages of attack by disinfectants during the inactivation process. Based on the experiments and the kinetic parameters obtained, it could be established that the efficiency of hydrogen peroxide was much lower than that of peracetic acid alone. However, the contribution of hydrogen peroxide was very important in the commercial mixture. It should be noted that this improvement occurred only after peracetic acid had initiated the attack on the cell. This synergistic effect was successfully explained by the proposed scheme and was verified by experimental results. Besides providing a clearer mechanistic understanding of water disinfection, such models may improve our ability to design reactors.

Steady nonuniform shallow flow within emergent vegetation

NASA Astrophysics Data System (ADS)

Wang, Wei-Jie; Huai, Wen-Xin; Thompson, Sally; Katul, Gabriel G.

2015-12-01

Surface flow redistribution on flat ground from crusted bare soil to vegetated patches following intense rainfall events elevates plant available water above that provided by rainfall. The significance of this surface water redistribution to sustaining vegetation in arid and semiarid regions is undisputed. What is disputed is the quantity and spatial distribution of the redistributed water. In ecohydrological models, such nonuniform flows are described using the Saint-Venant equation (SVE) subject to a Manning roughness coefficient closure. To explore these assumptions in the most idealized setting, flume experiments were conducted using rigid cylinders representing rigid vegetation with varying density. Flow was induced along the streamwise x direction by adjusting the free water surface height H(x) between the upstream and downstream boundaries mimicking the nonuniformity encountered in nature. In natural settings, such H(x) variations arise due to contrasts in infiltration capacity and ponded depths during storms. The measured H(x) values in the flume were interpreted using the SVE augmented with progressively elaborate approximations to the roughness representation. The simplest approximation employs a friction factor derived from a drag coefficient (Cd) for isolated cylinders in a locally (but not globally) uniform flow and upscaled using the rod density that was varied across experiments. Comparison between measured and modeled H(x) suggested that such a "naive" approach overpredicts H(x). Blockage was then incorporated into the SVE model calculations but resulted in underestimation of H(x). Biases in modeled H(x) suggest that Cd must be varying in x beyond what a local or bulk Reynolds number predicts. Inferred Cd(x) from the flume experiments exhibited a near-parabolic shape most peaked in the densest canopy cases. The outcome of such Cd(x) variations is then summarized in a bulk resistance formulation that may be beneficial to modeling runon-runoff processes on shallow slopes using SVE.

Five reasons not to use numerical models in water resource management (Arne Richter Award Lecture for OYS)

NASA Astrophysics Data System (ADS)

Pianosi, Francesca

2015-04-01

Sustainable water resource management in a quickly changing world poses new challenges to hydrology and decision sciences. Systems analysis can contribute to promote sustainable practices by providing the theoretical background and the operational tools for an objective and transparent appraisal of policy options for water resource systems (WRS) management. Traditionally, limited availability of data and computing resources imposed to use oversimplified WRS models, with little consideration of modeling uncertainties and of the non-stationarity and feedbacks between WRS drivers, and a priori aggregation of costs and benefits. Nowadays we increasingly recognize the inadequacy of these simplifications, and consider them among the reasons for the limited use of model-generated information in actual decision-making processes. On the other hand, fast-growing availability of data and computing resources are opening up unprecedented possibilities in the way we build and apply numerical models. In this talk I will discuss my experiences and ideas on how we can exploit this potential to improve model-informed decision-making while facing the challenges of uncertainty, non-stationarity, feedbacks and conflicting objectives. In particular, through practical examples of WRS design and operation problems, my talk will aim at stimulating discussion about the impact of uncertainty on decisions: can inaccurate and imprecise predictions still carry valuable information for decision-making? Does uncertainty in predictions necessarily limit our ability to make 'good' decisions? Or can uncertainty even be of help for decision-making, for instance by reducing the projected conflict between competing water use? Finally, I will also discuss how the traditionally separate disciplines of numerical modelling, optimization, and uncertainty and sensitivity analysis have in my experience been just different facets of the same 'systems approach'.

Applications of a thermal-based two-source energy balance model using Priestley-Taylor approach for surface temperature partitioning under advective conditions

NASA Astrophysics Data System (ADS)

Song, Lisheng; Kustas, William P.; Liu, Shaomin; Colaizzi, Paul D.; Nieto, Hector; Xu, Ziwei; Ma, Yanfei; Li, Mingsong; Xu, Tongren; Agam, Nurit; Tolk, Judy A.; Evett, Steven R.

2016-09-01

In this study ground measured soil and vegetation component temperatures and composite temperature from a high spatial resolution thermal camera and a network of thermal-IR sensors collected in an irrigated maize field and in an irrigated cotton field are used to assess and refine the component temperature partitioning approach in the Two-Source Energy Balance (TSEB) model. A refinement to TSEB using a non-iterative approach based on the application of the Priestley-Taylor formulation for surface temperature partitioning and estimating soil evaporation from soil moisture observations under advective conditions (TSEB-A) was developed. This modified TSEB formulation improved the agreement between observed and modeled soil and vegetation temperatures. In addition, the TSEB-A model output of evapotranspiration (ET) and the components evaporation (E), transpiration (T) when compared to ground observations using the stable isotopic method and eddy covariance (EC) technique from the HiWATER experiment and with microlysimeters and a large monolithic weighing lysimeter from the BEAREX08 experiment showed good agreement. Difference between the modeled and measured ET measurements were less than 10% and 20% on a daytime basis for HiWATER and BEAREX08 data sets, respectively. The TSEB-A model was found to accurately reproduce the temporal dynamics of E, T and ET over a full growing season under the advective conditions existing for these irrigated crops located in arid/semi-arid climates. With satellite data this TSEB-A modeling framework could potentially be used as a tool for improving water use efficiency and conservation practices in water limited regions. However, TSEB-A requires soil moisture information which is not currently available routinely from satellite at the field scale.

The North Pacific Acoustic Laboratory deep-water acoustic propagation experiments in the Philippine Sea.

PubMed

Worcester, Peter F; Dzieciuch, Matthew A; Mercer, James A; Andrew, Rex K; Dushaw, Brian D; Baggeroer, Arthur B; Heaney, Kevin D; D'Spain, Gerald L; Colosi, John A; Stephen, Ralph A; Kemp, John N; Howe, Bruce M; Van Uffelen, Lora J; Wage, Kathleen E

2013-10-01

A series of experiments conducted in the Philippine Sea during 2009-2011 investigated deep-water acoustic propagation and ambient noise in this oceanographically and geologically complex region: (i) the 2009 North Pacific Acoustic Laboratory (NPAL) Pilot Study/Engineering Test, (ii) the 2010-2011 NPAL Philippine Sea Experiment, and (iii) the Ocean Bottom Seismometer Augmentation of the 2010-2011 NPAL Philippine Sea Experiment. The experimental goals included (a) understanding the impacts of fronts, eddies, and internal tides on acoustic propagation, (b) determining whether acoustic methods, together with other measurements and ocean modeling, can yield estimates of the time-evolving ocean state useful for making improved acoustic predictions, (c) improving our understanding of the physics of scattering by internal waves and spice, (d) characterizing the depth dependence and temporal variability of ambient noise, and (e) understanding the relationship between the acoustic field in the water column and the seismic field in the seafloor. In these experiments, moored and ship-suspended low-frequency acoustic sources transmitted to a newly developed distributed vertical line array receiver capable of spanning the water column in the deep ocean. The acoustic transmissions and ambient noise were also recorded by a towed hydrophone array, by acoustic Seagliders, and by ocean bottom seismometers.

Study of lithium cation in water clusters: based on atom-bond electronegativity equalization method fused into molecular mechanics.

PubMed

Li, Xin; Yang, Zhong-Zhi

2005-05-12

We present a potential model for Li(+)-water clusters based on a combination of the atom-bond electronegativity equalization and molecular mechanics (ABEEM/MM) that is to take ABEEM charges of the cation and all atoms, bonds, and lone pairs of water molecules into the intermolecular electrostatic interaction term in molecular mechanics. The model allows point charges on cationic site and seven sites of an ABEEM-7P water molecule to fluctuate responding to the cluster geometry. The water molecules in the first sphere of Li(+) are strongly structured and there is obvious charge transfer between the cation and the water molecules; therefore, the charge constraint on the ionic cluster includes the charged constraint on the Li(+) and the first-shell water molecules and the charge neutrality constraint on each water molecule in the external hydration shells. The newly constructed potential model based on ABEEM/MM is first applied to ionic clusters and reproduces gas-phase state properties of Li(+)(H(2)O)(n) (n = 1-6 and 8) including optimized geometries, ABEEM charges, binding energies, frequencies, and so on, which are in fair agreement with those measured by available experiments and calculated by ab initio methods. Prospects and benefits introduced by this potential model are pointed out.

Model estimates of net primary productivity, evaportranspiration, and water use efficiency in the terrestrial ecosystems of the southern United States

Treesearch

Hanqin Tian; Guangsheng Chen; Mingliang Liu; Chi Zhang; Ge Sun; Chaoqun Lu; Xiaofeng Xu; Wei Ren; Shufen Pan; Arthur Chappelka

2010-01-01

The effects of global change on ecosystem productivity and water resources in the southern United States (SUS), a traditionally ‘water-rich’ region and the ‘timber basket’ of the country, are not well quantified. We carried out several simulation experiments to quantify ecosystem net primary productivity (NPP), evapotranspiration (ET)...

Laboratory investigation of flux reduction from dense non-aqueous phase liquid (DNAPL) partial source zone remediation by enhanced dissolution.

PubMed

Kaye, Andrew J; Cho, Jaehyun; Basu, Nandita B; Chen, Xiaosong; Annable, Michael D; Jawitz, James W

2008-11-14

This study investigated the benefits of partial removal of dense nonaqueous phase liquid (DNAPL) source zones using enhanced dissolution in eight laboratory scale experiments. The benefits were assessed by characterizing the relationship between reductions in DNAPL mass and the corresponding reduction in contaminant mass flux. Four flushing agents were evaluated in eight controlled laboratory experiments to examine the effects of displacement fluid property contrasts and associated override and underride on contaminant flux reduction (R(j)) vs. mass reduction (R(m)) relationships (R(j)(R(m))): 1) 50% ethanol/50% water (less dense than water), 2) 40% ethyl-lactate/60% water (more dense than water), 3) 18% ethanol/26% ethyl-lactate/56% water (neutrally buoyant), and 4) 2% Tween-80 surfactant (also neutrally buoyant). For each DNAPL architecture evaluated, replicate experiments were conducted where source zone dissolution was conducted with a single flushing event to remove most of the DNAPL from the system, and with multiple shorter-duration floods to determine the path of the R(j)(R(m)) relationship. All of the single-flushing experiments exhibited similar R(j)(R(m)) relationships indicating that override and underride effects associated with cosolvents did not significantly affect the remediation performance of the agents. The R(j)(R(m)) relationship of the multiple injection experiments for the cosolvents with a density contrast with water tended to be less desirable in the sense that there was less R(j) for a given R(m). UTCHEM simulations supported the observations from the laboratory experiments and demonstrated the capability of this model to predict R(j)(R(m)) relationships for non-uniformly distributed NAPL sources.

Fear of water in children and adults: etiology and familial effects.

PubMed

Graham, J; Gaffan, E A

1997-02-01

Water-fearful children (non-swimmers. 5-8 yrs and adults (non-swimmers or late learners, 23-73 yr) were compared with non-fearful controls of similar swimming ability. Parallel assessments were carried out with children and adults to investigate water-related experiences, water fear and competence in parents and siblings, and the relationship of water fear to other fear dimensions. Children were assessed behaviorally and by self and mother's report, adults by self-report. In neither children nor adults was there clear evidence that fearful and non-fearful groups differed in incidence of aversive water-related experience before fear onset. Parents usually believed that children's fear was present at first contact. In both samples, we found parent-offspring and sibling resemblances in fear. Analysis of details of children's contact with parents suggested that social learning within the family decreased water fear rather than increasing it; when both child and parent showed fear, that was as likely to reflect genetic influences as modeling. Young children's water fear forms part of a generic cluster, fear of the Unknown or Danger, while in adults it becomes independent of generic fears.

Validation of scintillometer measurements over a heterogeneous landscape: The LITFASS-2009 Experiment

NASA Astrophysics Data System (ADS)

Beyrich, F.; Bange, J.; Hartogensis, O.; Raasch, S.

2009-09-01

The turbulent exchange of heat and water vapour are essential land surface - atmosphere interaction processes in the local, regional and global energy and water cycles. Scintillometry can be considered as the only technique presently available for the quasi-operational experimental determination of area-averaged turbulent fluxes needed to validate the fluxes simulated by regional atmospheric models or derived from satellite images at a horizontal scale of a few kilometres. While scintillometry has found increasing application over the last years, some fundamental issues related to its use still need further investigation. In particular, no studies are known so far to reproduce the path-averaged structure parameters measured by scintillometers by independent measurements or modelling techniques. The LITFASS-2009 field experiment has been performed in the area around the Meteorological Observatory Lindenberg / Richard-Aßmann-Observatory in Germany during summer 2009. It was designed to investigate the spatial (horizontal and vertical) and temporal variability of structure parameters (underlying the scintillometer principle) over moderately heterogeneous terrain. The experiment essentially relied on a coupling of eddy-covariance measurements, scintillometry and airborne measurements with an unmanned autonomous aircraft able to strictly fly along the scintillometer path. Data interpretation will be supported by numerical modelling using a large-eddy simulation (LES) model. The paper will describe the design of the experiment. First preliminary results from the measurements will be presented.

Robust three-body water simulation model

NASA Astrophysics Data System (ADS)

Tainter, C. J.; Pieniazek, P. A.; Lin, Y.-S.; Skinner, J. L.

2011-05-01

The most common potentials used in classical simulations of liquid water assume a pairwise additive form. Although these models have been very successful in reproducing many properties of liquid water at ambient conditions, none is able to describe accurately water throughout its complicated phase diagram. The primary reason for this is the neglect of many-body interactions. To this end, a simulation model with explicit three-body interactions was introduced recently [R. Kumar and J. L. Skinner, J. Phys. Chem. B 112, 8311 (2008), 10.1021/jp8009468]. This model was parameterized to fit the experimental O-O radial distribution function and diffusion constant. Herein we reparameterize the model, fitting to a wider range of experimental properties (diffusion constant, rotational correlation time, density for the liquid, liquid/vapor surface tension, melting point, and the ice Ih density). The robustness of the model is then verified by comparing simulation to experiment for a number of other quantities (enthalpy of vaporization, dielectric constant, Debye relaxation time, temperature of maximum density, and the temperature-dependent second and third virial coefficients), with good agreement.

Interaction of lafutidine in binding to human serum albumin in gastric ulcer therapy: STD-NMR, WaterLOGSY-NMR, NMR relaxation times, Tr-NOESY, molecule docking, and spectroscopic studies.

PubMed

Yang, Hongqin; Huang, Yanmei; He, Jiawei; Li, Shanshan; Tang, Bin; Li, Hui

2016-09-15

In this study, lafutidine (LAF) was used as a model compound to investigate the binding mechanism between antiulcer drugs and human serum albumin (HSA) through various techniques, including STD-NMR, WaterLOGSY-NMR, (1)H NMR relaxation times, tr-NOESY, molecule docking calculation, FT-IR spectroscopy, and CD spectroscopy. The analyses of STD-NMR, which derived relative STD (%) intensities, and WaterLOGSY-NMR, determined that LAF bound to HSA. In particular, the pyridyl group of LAF was in close contact with HSA binding pocket, whereas furyl group had a secondary binding. Competitive STD-NMR and WaterLOGSY-NMR experiments, with warifarin and ibuprofen as site-selective probes, indicated that LAF preferentially bound to site II in the hydrophobic subdomains IIIA of HSA. The bound conformation of LAF at the HSA binding site was further elucidated by transferred NOE effect (tr-NOESY) experiment. Relaxation experiments provided quantitative information about the relationship between the affinity and structure of LAF. The molecule docking simulations conducted with AutoDock and the restraints derived from STD results led to three-dimensional models that were consistent with the NMR spectroscopic data. The presence of hydrophobic forces and hydrogen interactions was also determined. Additionally, FT-IR and CD spectroscopies showed that LAF induced secondary structure changes of HSA. Copyright © 2016 Elsevier Inc. All rights reserved.

Sensitivity of Atlantic meridional overturning circulation to the dynamical framework in an ocean general circulation model

NASA Astrophysics Data System (ADS)

Li, Xiaolan; Yu, Yongqiang; Liu, Hailong; Lin, Pengfei

2017-06-01

The horizontal coordinate systems commonly used in most global ocean models are the spherical latitude-longitude grid and displaced poles, such as a tripolar grid. The effect of the horizontal coordinate system on Atlantic meridional overturning circulation (AMOC) is evaluated by using an OGCM (ocean general circulation model). Two experiments are conducted with the model—one using a latitude-longitude grid (referred to as Lat_1) and the other using a tripolar grid (referred to as Tri). The results show that Tri simulates a stronger North Atlantic deep water (NADW) than Lat_1, as more saline water masses enter the Greenland-Iceland-Norwegian (GIN) seas in Tri. The stronger NADW can be attributed to two factors. One is the removal of the zonal filter in Tri, which leads to an increasing of the zonal gradient of temperature and salinity, thus strengthening the north geostrophic flow. In turn, it decreases the positive subsurface temperature and salinity biases in the subtropical regions. The other may be associated with topography at the North Pole, because realistic topography is applied in the tripolar grid while the latitude-longitude grid employs an artificial island around the North Pole. In order to evaluate the effect of the filter on AMOC, three enhanced filter experiments are carried out. Compared to Lat_1, an enhanced filter can also augment NADW formation, since more saline water is suppressed in the GIN seas, but accumulated in the Labrador Sea, especially in experiment Lat_2_S, which is the experiment with an enhanced filter on salinity.

PHYSICAL MODELING OF CONTRACTED FLOW.

USGS Publications Warehouse

Lee, Jonathan K.

1987-01-01

Experiments on steady flow over uniform grass roughness through centered single-opening contractions were conducted in the Flood Plain Simulation Facility at the U. S. Geological Survey's Gulf Coast Hydroscience Center near Bay St. Louis, Miss. The experimental series was designed to provide data for calibrating and verifying two-dimensional, vertically averaged surface-water flow models used to simulate flow through openings in highway embankments across inundated flood plains. Water-surface elevations, point velocities, and vertical velocity profiles were obtained at selected locations for design discharges ranging from 50 to 210 cfs. Examples of observed water-surface elevations and velocity magnitudes at basin cross-sections are presented.

Simulating the evolution of non-point source pollutants in a shallow water environment.

PubMed

Yan, Min; Kahawita, Rene

2007-03-01

Non-point source pollution originating from surface applied chemicals in either liquid or solid form as part of agricultural activities, appears in the surface runoff caused by rainfall. The infiltration and transport of these pollutants has a significant impact on subsurface and riverine water quality. The present paper describes the development of a unified 2-D mathematical model incorporating individual models for infiltration, adsorption, solubility rate, advection and diffusion, which significantly improve the current practice on mathematical modeling of pollutant evolution in shallow water. The governing equations have been solved numerically using cubic spline integration. Experiments were conducted at the Hydrodynamics Laboratory of the Ecole Polytechnique de Montreal to validate the mathematical model. Good correspondence between the computed results and experimental data has been obtained. The model may be used to predict the ultimate fate of surface applied chemicals by evaluating the proportions that are dissolved, infiltrated into the subsurface or are washed off.

Development of a distributed biosphere hydrological model and its evaluation with the Southern Great Plains Experiments (SGP97 and SGP99)

USDA-ARS?s Scientific Manuscript database

A distributed biosphere hydrological model, the so called water and energy budget-based distributed hydrological model (WEB-DHM), has been developed by fully coupling a biosphere scheme (SiB2) with a geomorphology-based hydrological model (GBHM). SiB2 describes the transfer of turbulent fluxes (ener...

Climate Change Impacts on River Temperature in the Southeastern United States: A Case Study of the Tennessee River Basin

NASA Astrophysics Data System (ADS)

Cheng, Y.; Niemeyer, R. J.; Mao, Y.; Yearsley, J. R.; Nijssen, B.

2016-12-01

In the coming decades, climate change and population growth are expected to affect water and energy supply as well as demand in the southeastern United States. Changes in temperature and precipitation impact river flow and stream temperature with implications for hydropower generation, industrial and municipal water supply, cooling for thermo-electric power plants, agricultural irrigation, ecosystem functions and flood control. At the same time, water and energy demand are expected to change in response to temperature increase, population growth and changing crop water requirements. As part of a multi-institution study of the food-energy-water nexus in the southeastern U.S., we are developing coupled hydrological and stream temperature models that will be linked to water resources, power systems and crop models at a later stage. Here we evaluate the ability of our system to simulate water supply and stream temperature in the Tennessee River Basin using the Variable Infiltration Capacity (VIC) macroscale hydrology model coupled to the River Basin Model (RBM), a 1-D semi-Lagrangian river temperature model, which has recently been expanded with a two-layer reservoir temperature model. Simulations with VIC-RBM were performed for the Tennessee River Basin at 1/8-degree spatial resolution and a temporal resolution of 1 day or less. Reservoir releases were prescribed based on historic operating rules. In future iterations, these releases will be modeled directly by a water resources model that incorporates flood control, and power and agricultural water demands. We compare simulated flows, as well as stream and reservoir temperatures with observed flows and temperatures throughout the basin. In preparation for later stages of the project, we also perform a set of climate change sensitivity experiments to evaluate how changes in climate may impact river and reservoir temperature.

Modeling climate change impacts on maize growth with the focus on plant internal water transport

NASA Astrophysics Data System (ADS)

Heinlein, Florian; Biernath, Christian; Klein, Christian; Thieme, Christoph; Priesack, Eckart

2015-04-01

Based on climate change experiments in chambers and on field measurements, the scientific community expects regional and global changes of crop biomass production and yields. In central Europe one major aspect of climate change is the shift of precipitation towards winter months and the increase of extreme events, e.g. heat stress and heavy precipitation, during the main growing season in summer. To understand water uptake, water use, and transpiration rates by plants numerous crop models were developed. We tested the ability of two existing canopy models (CERES-Maize and SPASS) embedded in the model environment Expert-N5.0 to simulate the water balance, water use efficiency and crop growth. Additionally, sap flow was measured using heat-ratio measurement devices at the stem base of individual plants. The models were tested against data on soil water contents, as well as on evaporation and transpiration rates of Maize plants, which were grown on lysimeters at Helmholtz Zentrum München and in the field at the research station Scheyern, Germany, in summer 2013 and 2014. We present the simulation results and discuss observed shortcomings of the models. CERES-Maize and SPASS could simulate the measured dynamics of xylem sap flow. However, these models oversimplify plant water transport, and thus, cannot explain the underlying mechanisms. Therefore, to overcome these shortcomings, we additionally propose a new model, which is based on two coupled 1-D Richards equations, describing explicitly the plant and soil water transport. This model, which has previously successfully been applied to simulate water flux of 94 individual beech trees of an old-grown forest, will lead to a more mechanistic representation of the soil-plant-water-flow-continuum. This xylem water flux model was now implemented into the crop model SPASS and adjusted to simulate water flux of single maize plants. The modified version is presented and explained. Basic model input requirements are the plant above- and below-ground architectures. Shoot architectures were derived from terrestrial laser scanning. Root architectures of Maize plants were generated using a simple L-system. Preliminary results will be presented together with simulation results by CERES-Maize and SPASS.

The water cycle in the general circulation model of the martian atmosphere

NASA Astrophysics Data System (ADS)

Shaposhnikov, D. S.; Rodin, A. V.; Medvedev, A. S.

2016-03-01

Within the numerical general-circulation model of the Martian atmosphere MAOAM (Martian Atmosphere: Observation and Modeling), we have developed the water cycle block, which is an essential component of modern general circulation models of the Martian atmosphere. The MAOAM model has a spectral dynamic core and successfully predicts the temperature regime on Mars through the use of physical parameterizations typical of both terrestrial and Martian models. We have achieved stable computation for three Martian years, while maintaining a conservative advection scheme taking into account the water-ice phase transitions, water exchange between the atmosphere and surface, and corrections for the vertical velocities of ice particles due to sedimentation. The studies show a strong dependence of the amount of water that is actively involved in the water cycle on the initial data, model temperatures, and the mechanism of water exchange between the atmosphere and the surface. The general pattern and seasonal asymmetry of the water cycle depends on the size of ice particles, the albedo, and the thermal inertia of the planet's surface. One of the modeling tasks, which results from a comparison of the model data with those of the TES experiment on board Mars Global Surveyor, is the increase in the total mass of water vapor in the model in the aphelion season and decrease in the mass of water ice clouds at the poles. The surface evaporation scheme, which takes into account the turbulent rise of water vapor, on the one hand, leads to the most complete evaporation of ice from the surface in the summer season in the northern hemisphere and, on the other hand, supersaturates the atmosphere with ice due to the vigorous evaporation, which leads to worse consistency between the amount of the precipitated atmospheric ice and the experimental data. The full evaporation of ice from the surface increases the model sensitivity to the size of the polar cap; therefore, the increase in the latter leads to better results. The use of a more accurate dust scenario changes the model temperatures, which also strongly affects the water cycle.

The Carbon-Water Interface: Modeling Challenges and Opportunities for the Water-Energy Nexus.

PubMed

Striolo, Alberto; Michaelides, Angelos; Joly, Laurent

2016-06-07

Providing clean water and sufficient affordable energy to all without compromising the environment is a key priority in the scientific community. Many recent studies have focused on carbon-based devices in the hope of addressing this grand challenge, justifying and motivating detailed studies of water in contact with carbonaceous materials. Such studies are becoming increasingly important because of the miniaturization of newly proposed devices, with ubiquitous nanopores, large surface-to-volume ratio, and many, perhaps most of the water molecules in contact with a carbon-based surface. In this brief review, we discuss some recent advances obtained via simulations and experiments in the development of carbon-based materials for applications in water desalination. We suggest possible ways forward, with particular emphasis on the synergistic combination of experiments and simulations, with simulations now sometimes offering sufficient accuracy to provide fundamental insights. We also point the interested reader to recent works that complement our short summary on the state of the art of this important and fascinating field.

[Development and application of a multi-species water quality model for water distribution systems with EPANET-MSX].

PubMed

Sun, Fu; Chen, Ji-ning; Zeng, Si-yu

2008-12-01

A conceptual multi-species water quality model for water distribution systems was developed on the basis of the toolkit of the EPANET-MSX software. The model divided the pipe segment into four compartments including pipe wall, biofilm, boundary layer and bulk liquid. The involved processes were substrate utilization and microbial growth, decay and inactivation of microorganisms, mass transfer of soluble components through the boundary layer, adsorption and desorption of particular components between bulk liquid and biofilm, oxidation and halogenation of organic matter by residual chlorine, and chlorine consumption by pipe wall. The fifteen simulated variables included the seven common variables both in the biofilm and in the bulk liquid, i.e. soluble organic matter, particular organic matter, ammonia nitrogen, residual chlorine, heterotrophic bacteria, autotrophic bacteria and inert solids, as well as biofilm thickness on the pipe wall. The model was validated against the data from a series of pilot experiments, and the simulation accuracy for residual chlorine and turbidity were 0.1 mg/L and 0.3 NTU respectively. A case study showed that the model could reasonably reflect the dynamic variation of residual chlorine and turbidity in the studied water distribution system, while Monte Carlo simulation, taking into account both the variability of finished water from the waterworks and the uncertainties of model parameters, could be performed to assess the violation risk of water quality in the water distribution system.

Validity of thermally-driven small-scale ventilated filling box models

NASA Astrophysics Data System (ADS)

Partridge, Jamie L.; Linden, P. F.

2013-11-01

The majority of previous work studying building ventilation flows at laboratory scale have used saline plumes in water. The production of buoyancy forces using salinity variations in water allows dynamic similarity between the small-scale models and the full-scale flows. However, in some situations, such as including the effects of non-adiabatic boundaries, the use of a thermal plume is desirable. The efficacy of using temperature differences to produce buoyancy-driven flows representing natural ventilation of a building in a small-scale model is examined here, with comparison between previous theoretical and new, heat-based, experiments.

Freezing Temperatures, Ice Nanotubes Structures, and Proton Ordering of TIP4P/ICE Water inside Single Wall Carbon Nanotubes.

PubMed

Pugliese, P; Conde, M M; Rovere, M; Gallo, P

2017-11-16

A very recent experimental paper importantly and unexpectedly showed that water in carbon nanotubes is already in the solid ordered phase at the temperature where bulk water boils. The water models used so far in literature for molecular dynamics simulations in carbon nanotubes show freezing temperatures lower than the experiments. We present here results from molecular dynamics simulations of water inside single walled carbon nanotubes using an extremely realistic model for both liquid and icy water, the TIP4P/ICE. The water behavior inside nanotubes of different diameters has been studied upon cooling along the isobars at ambient pressure starting from temperatures where water is in a liquid state. We studied the liquid/solid transition, and we observed freezing temperatures higher than in bulk water and that depend on the diameter of the nanotube. The maximum freezing temperature found is 390 K, which is in remarkable agreement with the recent experimental measurements. We have also analyzed the ice structure called "ice nanotube" that water forms inside the single walled carbon nanotubes when it freezes. The ice forms observed are in agreement with previous results obtained with different water models. A novel finding, a partial proton ordering, is evidenced in our ice nanotubes at finite temperature.

Toward a mechanistic understanding of the effect of biochar addition on soil water retention

NASA Astrophysics Data System (ADS)

Yi, S.; Chang, N.; Guo, M.; Imhoff, P. T.

2014-12-01

Biochar (BC) is a carbon-rich product produced by thermal degradation of biomass in an oxygen-free environment, whose application to sediment is said to improve water retention. However, BC produced from different feedstocks and pyrolyzed at different temperatures have distinct properties, which may alter water retention in ways difficult to predict a priori. Our goal is to develop a mechanistic understanding of BC addition on water retention by examining the impact of BC from two feedstocks, poultry litter (PL) and hardwood (HW), on the soil-water retention curves (SWRC) of a uniform sand and a sandy loam (SL). For experiments with sand, BC and sand were sieved to the same particle size (~ 0.547 mm) to minimize effects of BC addition on particle size distribution. Experiments with SL contained the same sieved BC. PL and HW bicohars were added at 2 and 7% (w/w), and water retention was measured from 0 to -4.38 × 106 cm-H2O. Both BCs increased porosities for sand and SL, up to 39 and 13% for sand and SL, respectively, with 7% HW BC addition. The primary cause for these increases was the internal porosity of BC particles. While the matric potential for air-entry was unchanged with BC addition, BC amendment increased water retention for sand and SL in the capillary region (0 to -15,000 cm-H2O) by an average of 26 and 33 % for 7% PL and HW BC in sand, respectively, but only 7 and 14 % for 7% PL and HW BC in SL. The most dramatic influence of BC amendment on water retention occurred in the adsorption region (< -15,000 cm-H2O), where water retention increased by a factor of 11 and 22 for 7% PL and HW BC in sand, respectively, but by 140 and 190 % for 7% PL and HW BC in SL, respectively. The impact of BC on water retention in these sediments is explained primarily by the additional surface area and internal porosity of PL and HW BC particles. van Genuchten (VG) models were fitted to the water retention data. For SL where the impact of BC addition on water retention was less significant, a unimodal model fit water retention data well for unamended and BC-amended media: the addition of BC did not create a new class of small pores that could not be described with a unimodal VG model. While a unimodal model fitted the sand data well, a bimodal model was required for all BC-amended sand. The influence of BC type, mass fraction and sediment on water retention models will be discussed.

Groundwater modeling in integrated water resources management--visions for 2020.

PubMed

Refsgaard, Jens Christian; Højberg, Anker Lajer; Møller, Ingelise; Hansen, Martin; Søndergaard, Verner

2010-01-01

Groundwater modeling is undergoing a change from traditional stand-alone studies toward being an integrated part of holistic water resources management procedures. This is illustrated by the development in Denmark, where comprehensive national databases for geologic borehole data, groundwater-related geophysical data, geologic models, as well as a national groundwater-surface water model have been established and integrated to support water management. This has enhanced the benefits of using groundwater models. Based on insight gained from this Danish experience, a scientifically realistic scenario for the use of groundwater modeling in 2020 has been developed, in which groundwater models will be a part of sophisticated databases and modeling systems. The databases and numerical models will be seamlessly integrated, and the tasks of monitoring and modeling will be merged. Numerical models for atmospheric, surface water, and groundwater processes will be coupled in one integrated modeling system that can operate at a wide range of spatial scales. Furthermore, the management systems will be constructed with a focus on building credibility of model and data use among all stakeholders and on facilitating a learning process whereby data and models, as well as stakeholders' understanding of the system, are updated to currently available information. The key scientific challenges for achieving this are (1) developing new methodologies for integration of statistical and qualitative uncertainty; (2) mapping geological heterogeneity and developing scaling methodologies; (3) developing coupled model codes; and (4) developing integrated information systems, including quality assurance and uncertainty information that facilitate active stakeholder involvement and learning.

Biofilm Effect on Flow Structure over a Permeable Bed

NASA Astrophysics Data System (ADS)

Kazemifar, F.; Blois, G.; Aybar, M.; Perez-Calleja, P.; Nerenberg, R.; Sinha, S.; Hardy, R. J.; Best, J.; Sambrook Smith, G.; Christensen, K. T.

2017-12-01

Biofilms constitute an important form of bacterial life in aquatic environments and are present at the fluid-solid interfaces in natural and industrial settings, such as water distribution systems and riverbeds among others. The permeable, heterogeneous, and deformable structure of biofilms can influence mass and momentum transport between the subsurface and freestream. However, this interaction is not fully understood, in part due to technical obstacles impeding quantitative experimental investigations. In this work, the effect of biofilm on flow structure over a permeable bed is studied. Experiments are conducted in a closed water channel equipped with an idealized two-dimensional permeable bed. Prior to conducting flow experiments, the models are placed within an independent recirculating reactor for biofilm growth. Once a targeted biofilm growth stage is achieved, the models are transferred to the water channel and subjected to transitional and turbulent flows. Long-distance microscopic particle image velocimetry measurements are performed to quantify the effect of biofilm on the turbulence structure of the free flow as well as the freestream-subsurface flow interaction.

Global water cycle and Earth's thermal evolution

NASA Astrophysics Data System (ADS)

Franck, Siegfried; Bounama, Christine

2001-09-01

Convergent margin processes play an important role in the distribution of terrestrial volatile species. During subduction processes volatiles are filtered from the subducting package and are restricted to return to the mantle. Water is the most abundant volatile and plays an important role in these processes. There is a number of geochemical investigations to determine the subduction, regassing, and recycling fluxes as well as the regassing ratio of water. The latter describes the partition of subducting water by water that is regassed into the mantle and water that is returned to the surface in arc magmas. Here we present a geophysical-based modelling approach for the calculation of such fluxes and ratios in order to compare them with the geochemical data. In order to assess the recent values and the evolution of the subduction, regassing, and the recycling flux a simple parameterized thermal convection model with a water-dependent rheology and a constant continental growth model is applied. To test the sensitivity of the results different continental growth models were applied and the total amount of water in the system was varied as well as the initial distribution of water in the reservoirs. According to our estimations a value of 0.31 for the time independent regassing ratio of water, RH 2O , is an acceptable upper bound. Lower values of RH 2O give larger water reservoirs on the surface compared to the recent situation. Larger values of RH 2O suggest smaller surface reservoirs of water and, therefore, seem to be unlikely. The model results show a relatively stable value for the regassing ratio of 0.31 by varying the initial conditions of the water distribution in the reservoirs (which are pretty much unknown at the present moment). But RH 2O is very sensitive towards the total amount of water in the system. Altering the value of four ocean masses to ten we get values for the regassing ratio from 0.31 to 0.89. Nevertheless, as a result of all numerical experiments the recent subduction flux is stable and equal to 1.02×10 15 g/a. The influence of the continental growth model on the results could be neglected. The calculated value for the recent subduction water flux fits the modern geochemical data very well while our value for RH 2O is smaller. One possible reason could be that in our experiments RH 2O remains constant and, therefore, represents an average value over Earth's history. In order to check this assumption we apply a simple exponential time dependence of RH 2O . Here, the modern regassing ratio increases to 0.41. Therefore, based on a geophysical modelling approach in contrast to the geochemical investigations we suggest a smaller value for the modern regassing ratio of about 0.3 to 0.4.

A mathematical model for the transfer of soil solutes to runoff under water scouring.

PubMed

Yang, Ting; Wang, Quanjiu; Wu, Laosheng; Zhang, Pengyu; Zhao, Guangxu; Liu, Yanli

2016-11-01

The transfer of nutrients from soil to runoff often causes unexpected pollution in water bodies. In this study, a mathematical model that relates to the detachment of soil particles by water flow and the degree of mixing between overland flow and soil nutrients was proposed. The model assumes that the mixing depth is an integral of average water flow depth, and it was evaluated by experiments with three water inflow rates to bare soil surfaces and to surfaces with eight treatments of different stone coverages. The model predicted outflow rates were compared with the experimentally observed data to test the accuracy of the infiltration parameters obtained by curve fitting the models to the data. Further analysis showed that the comprehensive mixing coefficient (ke) was linearly correlated with Reynolds' number Re (R(2)>0.9), and this relationship was verified by comparing the simulated potassium concentration and cumulative mass with observed data, respectively. The best performance with the bias error analysis (Nash Sutcliffe coefficient of efficiency (NS), relative error (RE) and the coefficient of determination (R(2))) showed that the predicted data by the proposed model was in good agreement with the measured data. Thus the model can be used to guide soil-water and fertilization management to minimize nutrient runoff from cropland. Copyright © 2016 Elsevier B.V. All rights reserved.

Mathematical Model Formulation And Validation Of Water And Solute Transport In Whole Hamster Pancreatic Islets

PubMed Central

Benson, Charles T.; Critser, John K.

2014-01-01

Optimization of cryopreservation protocols for cells and tissues requires accurate models of heat and mass transport. Model selection often depends on the configuration of the tissue. Here, a mathematical and conceptual model of water and solute transport for whole hamster pancreatic islets has been developed and experimentally validated incorporating fundamental biophysical data from previous studies on individual hamster islet cells while retaining whole-islet structural information. It describes coupled transport of water and solutes through the islet by three methods: intracellularly, intercellularly, and in combination. In particular we use domain decomposition techniques to couple a transmembrane flux model with an interstitial mass transfer model. The only significant undetermined variable is the cellular surface area which is in contact with the intercellularly transported solutes, Ais. The model was validated and Ais determined using a 3 × 3 factorial experimental design blocked for experimental day. Whole islet physical experiments were compared with model predictions at three temperatures, three perfusing solutions, and three islet size groups. A mean of 4.4 islets were compared at each of the 27 experimental conditions and found to correlate with a coefficient of determination of 0.87 ± 0.06 (mean ± S.D.). Only the treatment variable of perfusing solution was found to be significant (p < 0.05). We have devised a model that retains much of the intrinsic geometric configuration of the system, and thus fewer laboratory experiments are needed to determine model parameters and thus to develop new optimized cryopreservation protocols. Additionally, extensions to ovarian follicles and other concentric tissue structures may be made. PMID:24950195

Negative pressures and spallation in water drops subjected to nanosecond shock waves

DOE PAGES

Stan, Claudiu A.; Willmott, Philip R.; Stone, Howard A.; ...

2016-05-16

Most experimental studies of cavitation in liquid water at negative pressures reported cavitation at tensions significantly smaller than those expected for homogeneous nucleation, suggesting that achievable tensions are limited by heterogeneous cavitation. We generated tension pulses with nanosecond rise times in water by reflecting cylindrical shock waves, produced by X-ray laser pulses, at the internal surface of drops of water. Depending on the X-ray pulse energy, a range of cavitation phenomena occurred, including the rupture and detachment, or spallation, of thin liquid layers at the surface of the drop. When spallation occurred, we evaluated that negative pressures below –100 MPamore » were reached in the drops. As a result, we model the negative pressures from shock reflection experiments using a nucleation-and-growth model that explains how rapid decompression could outrun heterogeneous cavitation in water, and enable the study of stretched water close to homogeneous cavitation pressures.« less

Field warming experiments shed light on the wheat yield response to temperature in China

PubMed Central

Zhao, Chuang; Piao, Shilong; Huang, Yao; Wang, Xuhui; Ciais, Philippe; Huang, Mengtian; Zeng, Zhenzhong; Peng, Shushi

2016-01-01

Wheat growth is sensitive to temperature, but the effect of future warming on yield is uncertain. Here, focusing on China, we compiled 46 observations of the sensitivity of wheat yield to temperature change (SY,T, yield change per °C) from field warming experiments and 102 SY,T estimates from local process-based and statistical models. The average SY,T from field warming experiments, local process-based models and statistical models is −0.7±7.8(±s.d.)% per °C, −5.7±6.5% per °C and 0.4±4.4% per °C, respectively. Moreover, SY,T is different across regions and warming experiments indicate positive SY,T values in regions where growing-season mean temperature is low, and water supply is not limiting, and negative values elsewhere. Gridded crop model simulations from the Inter-Sectoral Impact Model Intercomparison Project appear to capture the spatial pattern of SY,T deduced from warming observations. These results from local manipulative experiments could be used to improve crop models in the future. PMID:27853151

Conceptualizing the dynamics of a drought affected agricultural community

NASA Astrophysics Data System (ADS)

Kuil, Linda; Carr, Gemma; Viglione, Alberto; Bloeschl, Guenter

2015-04-01

Climate and especially water availability and variability play an important role in the development of our societies. This can be seen through the vast investments that are made in reaching water security and the economic impact regions experience when the rains fail. However, the limit of available fresh water is increasingly felt as our population increases and the demand for water continues to rise. But how do we as society respond? Are periods of drought making us more resilient? The answer to this question is sought through the development of a stylized model that is built within the spirit of the Easter Island model by Brander and Taylor and aimed at capturing the essence of the dynamics of water supply and demand. By explicitly incorporating feedbacks, but keeping the framework simple, the model seeks to understand qualitative behavior of our socio-hydrological system as opposed to predicting exact pathways. The model shows that carrying capacity dynamics are a determining factor for continued growth. Future work will explore the underlying relationships further, among others, through examination of case studies.

Combined Experimental and Computational Approach to Predict the Glass-Water Reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pierce, Eric M.; Bacon, Diana H.

2011-10-01

The use of mineral and glass dissolution rates measured in laboratory experiments to predict the weathering of primary minerals and volcanic and nuclear waste glasses in field studies requires the construction of rate models that accurately describe the weathering process over geologic timescales. Additionally, the need to model the long-term behavior of nuclear waste glass for the purpose of estimating radionuclide release rates requires that rate models be validated with long-term experiments. Several long-term test methods have been developed to accelerate the glass-water reaction [drip test, vapor hydration test, product consistency test B, and pressurized unsaturated flow (PUF)], thereby reducingmore » the duration required to evaluate long-term performance. Currently, the PUF test is the only method that mimics the unsaturated hydraulic properties expected in a subsurface disposal facility and simultaneously monitors the glass-water reaction. PUF tests are being conducted to accelerate the weathering of glass and validate the model parameters being used to predict long-term glass behavior. A one-dimensional reactive chemical transport simulation of glass dissolution and secondary phase formation during a 1.5-year-long PUF experiment was conducted with the Subsurface Transport Over Reactive Multiphases (STORM) code. Results show that parameterization of the computer model by combining direct bench scale laboratory measurements and thermodynamic data provides an integrated approach to predicting glass behavior over the length of the experiment. Over the 1.5-year-long test duration, the rate decreased from 0.2 to 0.01 g/(m2 day) based on B release for low-activity waste glass LAWA44. The observed decrease is approximately two orders of magnitude higher than the decrease observed under static conditions with the SON68 glass (estimated to be a decrease by four orders of magnitude) and suggests that the gel-layer properties are less protective under these dynamic conditions.« less

Combined Experimental and Computational Approach to Predict the Glass-Water Reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pierce, Eric M; Bacon, Diana

2011-01-01

The use of mineral and glass dissolution rates measured in laboratory experiments to predict the weathering of primary minerals and volcanic and nuclear waste glasses in field studies requires the construction of rate models that accurately describe the weathering process over geologic time-scales. Additionally, the need to model the long-term behavior of nuclear waste glass for the purpose of estimating radionuclide release rates requires that rate models are validated with long-term experiments. Several long-term test methods have been developed to accelerate the glass-water reaction [drip test, vapor hydration test, product consistency test-B, and pressurized unsaturated flow (PUF)], thereby reducing themore » duration required to evaluate long-term performance. Currently, the PUF test is the only method that mimics the unsaturated hydraulic properties expected in a subsurface disposal facility and simultaneously monitors the glass-water reaction. PUF tests are being conducted to accelerate the weathering of glass and validate the model parameters being used to predict long-term glass behavior. A one-dimensional reactive chemical transport simulation of glass dissolution and secondary phase formation during a 1.5-year long PUF experiment was conducted with the subsurface transport over reactive multi-phases code. Results show that parameterization of the computer model by combining direct bench-scale laboratory measurements and thermodynamic data provides an integrated approach to predicting glass behavior over the length of the experiment. Over the 1.5-year long test duration, the rate decreased from 0.2 to 0.01 g/(m2 d) base on B release. The observed decrease is approximately two orders of magnitude higher than the decrease observed under static conditions with the SON68 glass (estimated to be a decrease by 4 orders of magnitude) and suggest the gel-layer properties are less protective under these dynamic conditions.« less

Simulating the impact of climate, land use and human water use on the hydrological system over the period 1850-2100 using PCR-GLOBWB

NASA Astrophysics Data System (ADS)

Bosmans, Joyce; van Beek, Rens; Bierkens, Marc

2015-04-01

In this study we investigate the impact of humans on the global hydrological system by separating the impacts of climate change, land use and land cover change, and human water use in a series of experiments with the PCR-GLOBWB hydrological model (e.g. van Beek et al., 2011; Sutanudjaja et al., 2014). We force PCR-GLOBWB with input from the EC-Earth and CESM GCMs, allowing us to extend our experiments from the pre-industrial (1850) to the end of the century (2099). Two greenhouse gas emission scenarios are used for the coming century: Representative Concentration Pathway 2.6 (RCP2.6), a low-end scenario, as well as the high-end RCP8.5 scenario. Precipitation, temperature and reference potential evapotranspiration are applied to PCR-GLOBWB, after bias-correction using the ISI-MIP method (Hempel et al., 2013). The reference potential evapotranspiration is computed using the Penman-Monteith equation with GCM wind, radiation, temperature, humidity and pressure as opposed to the Hamon method used as default in PCR-GLOBWB. To evaluate the impacts of climate change as well as land use and land cover (LULC) change, we apply a combination of fixed and transient LULC scenarios. First, LULC is kept fixed at 1850 values, so the hydrological model is only experiencing changes in precipitation, temperature and reference potential evapotranspiration. Then, LULC is allowed to vary according to historical reconstructions (HYDE) and future projections per RCP (Hurtt et al., 2011). In these experiments, anthropogenic effects are excluded. This is the first study to evaluate PCR-GLOBWB with pre-industrial or transient LULC in combination with present and future climate change. The next step is to investigate human impacts on the water system, by comparing the experiment with varying LULC to an experiment that additionally includes reservoir operations, human water abstractions including irrigation (paddy and non-paddy) and subsequent return flows. We aim to project future human impacts using information based on Shared Socioeconomic Pathways (SSPs). In previous studies, domestic, industrial and irrigation water demand were varied over the past decades in PCR-GLOBWB. Here we improve the analyses of human impacts on the hydrological system by looking further into the past and the future, as well as by comparing the impact of human water use to impacts of climate and LULC change. van Beek et al (2011), Global monthly water stress: 1. Water balance and water availability. Water Resources Research, Vol 47. Hempel et al (2013), A trend-preserving bias correction - the ISI-MIP approach. Earth System Dynamics, Vol 4. Hurtt et al (2011), Harmonization of land-use scenarios for the period 1500-2100: 600 years of global gridded annual land-use transitions, wood harvest, and resulting secondary lands. Climatic Change, Vol 109. Sutanudjaja et al (2014), Development and validation of PCR-GLOBWB 2.0: a 5 arc min resolution global hydrology and water resources model. EGU General Assembly Conference Abstracts

Developing a framework to assess the water quality and quantity impacts of climate change, shifting land use, and urbanization in a Midwestern agricultural landscape

NASA Astrophysics Data System (ADS)

Loheide, S. P.; Booth, E. G.; Kucharik, C. J.; Carpenter, S. R.; Gries, C.; Katt-Reinders, E.; Rissman, A. R.; Turner, M. G.

2011-12-01

Dynamic hydrological processes play a critical role in the structure and functioning of agricultural watersheds undergoing urbanization. Developing a predictive understanding of the complex interaction between agricultural productivity, ecosystem health, water quality, urban development, and public policy requires an interdisciplinary effort that investigates the important biophysical and social processes of the system. Our research group has initiated such a framework that includes a coordinated program of integrated scenarios, model experiments to assess the effects of changing drivers on a broad set of ecosystem services, evaluations of governance and leverage points, outreach and public engagement, and information management. Our geographic focus is the Yahara River watershed in south-central Wisconsin, which is an exemplar of water-related issues in the Upper Midwest. This research addresses three specific questions. 1) How do different patterns of land use, land cover, land management, and water resources engineering practices affect the resilience and sensitivity of ecosystem services under a changing climate? 2) How can regional governance systems for water and land use be made more resilient and adaptive to meet diverse human needs? 3) In what ways are regional human-environment systems resilient and in what ways are they vulnerable to potential changes in climate and water resources? A comprehensive program of model experiments and biophysical measurements will be utilized to evaluate changes in five freshwater ecosystem services (flood regulation, groundwater recharge, surface water quality, groundwater quality, and lake recreation) and five related ecosystem services (food crop yields, bioenergy crop yields, carbon storage in soil, albedo, and terrestrial recreation). Novel additions to existing biophysical models will allow us to simulate all components of the hydrological cycle as well as agricultural productivity, nitrogen and phosphorus transport, and lake water quality. The integrated model will be validated using a comprehensive observational database that includes soil moisture, evapotranspiration, stomatal conductance, streamflow, stream and lake water quality, and crop yields and productivity. Integrated scenarios will be developed to synthesize decision-maker perspectives, alternative approaches to resource governance, plausible trends in demographic and economic drivers, and model projections under alternate climate and land use regimes to understand future conditions of the watershed and its ecosystem services. The quantitative data and integrated scenarios will then be linked to evaluate governance of water and land use.

Role of cold water and beta-effect in the formation of the East Korean Warm Current in the East/Japan Sea: a numerical experiment

NASA Astrophysics Data System (ADS)

Kim, Yong-Yub; Cho, Yang-Ki; Kim, Young Ho

2018-06-01

The contributions of bottom cold water and planetary β-effect to the formation of the East Korean Warm Current (EKWC), the western boundary current in the East/Japan Sea (EJS), were evaluated using an idealized three-dimensional numerical model. The model results suggest that the bottom cold water and, to a lesser extent, the planetary β-effect both contribute to the formation of the EKWC. The cold water functions as the bottom of the upper layer, to control the EKWC via conservation of potential vorticity. It is known that cold waters, such as the North Korean Cold Water and Korea Strait Bottom Cold Water often observed during summer along the southwestern coast of the EJS, originate from the winter convection in the northern area. Observational studies consistently show that the EKWC strengthens in summer when the cold water extends further south along the western boundary.

Toward more accurate basal boundary conditions: a new 2-D model of distributed and channelised subglacial drainage

NASA Astrophysics Data System (ADS)

Werder, M. A.; Hewitt, I. J.; Schoof, C.; Flowers, G. E.

2012-04-01

Basal boundary conditions are one of the least constrained components of today's ice sheet models. To get at these one needs to know the distributed basal water pressure. We present a new glacier drainage system model to contribute to this missing piece of the puzzle. This two dimensional mathematical/numerical model combines distributed and channelised drainage at the ice-bed interface coupled to a water storage component. Notably the model determines the location of the channels as part of the solution. This is achieved by allowing channels (modelled as R-channels) to form on any of the edges of the unstructured triangular grid used to discretise the model. The distributed system is represented by a water sheet which is a continuum description of a linked-cavity system and exchanges water with the channels along their length. Water storage is parameterised as a function of the subglacial water pressure, which can be interpreted as storage in an englacial aquifer or due to elastic processes. The parabolic equation that determines the water pressure is solved using finite elements, the time evolution of the water sheet thickness and channel diameter are governed by local differential equations that are integrated using explicit methods. To explore the model's properties, we apply it to synthetic ice sheet catchments with areas up to 3000km2. We present steady state drainage system configurations and evaluate their channel-network properties (fractal dimensions, channel spacing). We find that an arborescent channel network forms whose density depends on the water sheet conductivity relative to water input. As a further experiment, we force the model with a seasonally and diurnally varying melt water input to investigate how the modelled drainage system evolves on these time scales: a channelised system grows up glacier as meltwater is delivered to the bed in spring and collapses in autumn. Water pressure is highest just before the formation of channels and then drops. Conversely, the diurnal variations in discharge affect the drainage system morphology only slightly. Instead they lead to large water pressure variations which lag meltwater input and coincide with changes in the volume of stored water. By incorporating an evolving R-channel network within a continuum model of distributed water drainage and storage, this 2-D model succeeds in qualitatively reproducing many of the observed and postulated features of the glacier drainage system.

Superstatistics model for T₂ distribution in NMR experiments on porous media.

PubMed

Correia, M D; Souza, A M; Sinnecker, J P; Sarthour, R S; Santos, B C C; Trevizan, W; Oliveira, I S

2014-07-01

We propose analytical functions for T2 distribution to describe transverse relaxation in high- and low-fields NMR experiments on porous media. The method is based on a superstatistics theory, and allows to find the mean and standard deviation of T2, directly from measurements. It is an alternative to multiexponential models for data decay inversion in NMR experiments. We exemplify the method with q-exponential functions and χ(2)-distributions to describe, respectively, data decay and T2 distribution on high-field experiments of fully water saturated glass microspheres bed packs, sedimentary rocks from outcrop and noisy low-field experiment on rocks. The method is general and can also be applied to biological systems. Copyright © 2014 Elsevier Inc. All rights reserved.

Performance simulation of the JPL solar-powered distiller. Part 1: Quasi-steady-state conditions. [for cooling microwave equipment

NASA Technical Reports Server (NTRS)

Yung, C. S.; Lansing, F. L.

1983-01-01

A 37.85 cu m (10,000 gallons) per year (nominal) passive solar powered water distillation system was installed and is operational in the Venus Deep Space Station. The system replaced an old, electrically powered water distiller. The distilled water produced with its high electrical resistivity is used to cool the sensitive microwave equipment. A detailed thermal model was developed to simulate the performance of the distiller and study its sensitivity under varying environment and load conditions. The quasi-steady state portion of the model is presented together with the formulas for heat and mass transfer coefficients used. Initial results indicated that a daily water evaporation efficiency of 30% can be achieved. A comparison made between a full day performance simulation and the actual field measurements gave good agreement between theory and experiment, which verified the model.

The ASSET intercomparison of stratosphere and lower mesosphere humidity analyses

NASA Astrophysics Data System (ADS)

Thornton, H. E.; Jackson, D. R.; Bekki, S.; Bormann, N.; Errera, Q.; Geer, A. J.; Lahoz, W. A.; Rharmili, S.

2008-07-01

This paper presents results from the first detailed intercomparison of stratosphere-lower mesosphere water vapour analyses; it builds on earlier results from the "Assimilation of ENVISAT Data" (ASSET) project. With the availability of high resolution, good quality Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) water vapour profiles, the ability of four different atmospheric models to assimilate these data is tested. MIPAS data have been assimilated over September 2003 into the models of the European Centre for Medium Range Weather Forecasts (ECMWF), the Belgian Institute for Space and Aeronomy (BIRA-IASB), the French Service d'Aéronomie (SA-IPSL) and the UK Met Office. The resultant middle atmosphere humidity analyses are compared against independent satellite data from the Halogen Occultation Experiment (HALOE), the Polar Ozone and Aerosol Measurement (POAM III) and the Stratospheric Aerosol and Gas Experiment (SAGE II). The MIPAS water vapour profiles are generally well assimilated in the ECMWF, BIRA-IASB and SA systems, producing stratosphere-mesosphere water vapour fields where the main features compare favourably with the independent observations. However, the models are less capable of assimilating the MIPAS data where water vapour values are locally extreme or in regions of strong humidity gradients, such as the Southern Hemisphere lower stratosphere polar vortex. Differences in the analyses can be attributed to the choice of humidity control variable, how the background error covariance matrix is generated, the model resolution and its complexity, the degree of quality control of the observations and the use of observations near the model boundaries. Due to the poor performance of the Met Office analyses the results are not included in the intercomparison, but are discussed separately. The Met Office results highlight the pitfalls in humidity assimilation, and provide lessons that should be learnt by developers of stratospheric humidity assimilation systems. In particular, they underline the importance of the background error covariances in generating a realistic troposphere to mesosphere water vapour analysis.

Sensitivity of open-water ice growth and ice concentration evolution in a coupled atmosphere-ocean-sea ice model

NASA Astrophysics Data System (ADS)

Shi, Xiaoxu; Lohmann, Gerrit

2017-09-01

A coupled atmosphere-ocean-sea ice model is applied to investigate to what degree the area-thickness distribution of new ice formed in open water affects the ice and ocean properties. Two sensitivity experiments are performed which modify the horizontal-to-vertical aspect ratio of open-water ice growth. The resulting changes in the Arctic sea-ice concentration strongly affect the surface albedo, the ocean heat release to the atmosphere, and the sea-ice production. The changes are further amplified through a positive feedback mechanism among the Arctic sea ice, the Atlantic Meridional Overturning Circulation (AMOC), and the surface air temperature in the Arctic, as the Fram Strait sea ice import influences the freshwater budget in the North Atlantic Ocean. Anomalies in sea-ice transport lead to changes in sea surface properties of the North Atlantic and the strength of AMOC. For the Southern Ocean, the most pronounced change is a warming along the Antarctic Circumpolar Current (ACC), owing to the interhemispheric bipolar seasaw linked to AMOC weakening. Another insight of this study lies on the improvement of our climate model. The ocean component FESOM is a newly developed ocean-sea ice model with an unstructured mesh and multi-resolution. We find that the subpolar sea-ice boundary in the Northern Hemisphere can be improved by tuning the process of open-water ice growth, which strongly influences the sea ice concentration in the marginal ice zone, the North Atlantic circulation, salinity and Arctic sea ice volume. Since the distribution of new ice on open water relies on many uncertain parameters and the knowledge of the detailed processes is currently too crude, it is a challenge to implement the processes realistically into models. Based on our sensitivity experiments, we conclude a pronounced uncertainty related to open-water sea ice growth which could significantly affect the climate system sensitivity.

Rising CO2 Levels Will Intensify Phytoplankton Blooms in Eutrophic and Hypertrophic Lakes

PubMed Central

Verspagen, Jolanda M. H.; Van de Waal, Dedmer B.; Finke, Jan F.; Visser, Petra M.; Van Donk, Ellen; Huisman, Jef

2014-01-01

Harmful algal blooms threaten the water quality of many eutrophic and hypertrophic lakes and cause severe ecological and economic damage worldwide. Dense blooms often deplete the dissolved CO2 concentration and raise pH. Yet, quantitative prediction of the feedbacks between phytoplankton growth, CO2 drawdown and the inorganic carbon chemistry of aquatic ecosystems has received surprisingly little attention. Here, we develop a mathematical model to predict dynamic changes in dissolved inorganic carbon (DIC), pH and alkalinity during phytoplankton bloom development. We tested the model in chemostat experiments with the freshwater cyanobacterium Microcystis aeruginosa at different CO2 levels. The experiments showed that dense blooms sequestered large amounts of atmospheric CO2, not only by their own biomass production but also by inducing a high pH and alkalinity that enhanced the capacity for DIC storage in the system. We used the model to explore how phytoplankton blooms of eutrophic waters will respond to rising CO2 levels. The model predicts that (1) dense phytoplankton blooms in low- and moderately alkaline waters can deplete the dissolved CO2 concentration to limiting levels and raise the pH over a relatively wide range of atmospheric CO2 conditions, (2) rising atmospheric CO2 levels will enhance phytoplankton blooms in low- and moderately alkaline waters with high nutrient loads, and (3) above some threshold, rising atmospheric CO2 will alleviate phytoplankton blooms from carbon limitation, resulting in less intense CO2 depletion and a lesser increase in pH. Sensitivity analysis indicated that the model predictions were qualitatively robust. Quantitatively, the predictions were sensitive to variation in lake depth, DIC input and CO2 gas transfer across the air-water interface, but relatively robust to variation in the carbon uptake mechanisms of phytoplankton. In total, these findings warn that rising CO2 levels may result in a marked intensification of phytoplankton blooms in eutrophic and hypertrophic waters. PMID:25119996

APEX Model Simulation for Row Crop Watersheds with Agroforestry and Grass Buffers

USDA-ARS?s Scientific Manuscript database

Watershed model simulation has become an important tool in studying ways and means to reduce transport of agricultural pollutants. Conducting field experiments to assess buffer influences on water quality are constrained by the large-scale nature of watersheds, high experimental costs, private owner...

Modeled ground water age distributions

USGS Publications Warehouse

Woolfenden, Linda R.; Ginn, Timothy R.

2009-01-01

The age of ground water in any given sample is a distributed quantity representing distributed provenance (in space and time) of the water. Conventional analysis of tracers such as unstable isotopes or anthropogenic chemical species gives discrete or binary measures of the presence of water of a given age. Modeled ground water age distributions provide a continuous measure of contributions from different recharge sources to aquifers. A numerical solution of the ground water age equation of Ginn (1999) was tested both on a hypothetical simplified one-dimensional flow system and under real world conditions. Results from these simulations yield the first continuous distributions of ground water age using this model. Complete age distributions as a function of one and two space dimensions were obtained from both numerical experiments. Simulations in the test problem produced mean ages that were consistent with the expected value at the end of the model domain for all dispersivity values tested, although the mean ages for the two highest dispersivity values deviated slightly from the expected value. Mean ages in the dispersionless case also were consistent with the expected mean ages throughout the physical model domain. Simulations under real world conditions for three dispersivity values resulted in decreasing mean age with increasing dispersivity. This likely is a consequence of an edge effect. However, simulations for all three dispersivity values tested were mass balanced and stable demonstrating that the solution of the ground water age equation can provide estimates of water mass density distributions over age under real world conditions.

Social and Structural Patterns of Drought-Related Water Conservation and Rebound

NASA Astrophysics Data System (ADS)

Gonzales, Patricia; Ajami, Newsha

2017-12-01

Water use practices and conservation are the result of complex sociotechnical interactions of political, economic, hydroclimatic, and social factors. While the drivers of water demand have been extensively studied, they have traditionally been applied to models that assume stationary relationships between these various factors, and usually do not account for potential societal changes in response to increased scarcity awareness. For example, following a period of sustained low demand such as during a drought, communities often increase water use during a hydrologically wet period, a phenomenon known as "rebounding" water use. Previous experiences show the extent of this rebound is not a straightforward function of policy and efficiency improvements, but may also reflect short-term or long-lasting change in community behavior, which are not easily captured by models that assume stationarity. In this work, we develop a system dynamics model to represent water demand as a function of both structural and social factors. We apply this model to the analysis of three diverse water utilities in the San Francisco Bay Area between 1980 and 2017, identifying drought response trends and drivers over time. Our model is consistent with empirical patterns and historical context of water use in California, and provides important insights on the rebound phenomenon that can be extended to other locations. This comparative assessment indicates that policies, public outreach, and better data availability have played a key role in raising public awareness of water scarcity, especially with the raise of the internet era in recent years.

Comparison of the Solubilization Properties of Polysorbate 80 and Isopropanol/Water Solvent Systems for Organic Compounds Extracted from Three Pharmaceutical Packaging Configurations.

PubMed

Zdravkovic, Steven A

2016-10-10

It has been reported that the presence of polysorbate 80 in a pharmaceutical product's formulation may increase the number and/or amount of impurities leached from materials used during its manufacture, storage, and/or administration. However, it is uncertain if/how the solubilization properties of this surfactant compare to non-surfactant solvent systems. The goal of this study is to provide insight into this area of uncertainty by comparing the solubilization properties of polysorbate 80 to those of isopropanol/water solutions while in contact with a plasticized polyvinylchloride parenteral delivery bag, a single-use type manufacturing bag, and a polypropylene bottle. These properties were determined via a binding experiment, in which a set of model compounds was introduced into the solutions, and via an extraction experiment, in which compounds were extracted from the packaging material by the solutions. In both experiments, the amount of each compound present at equilibrium was assayed to determine the extent they were solubilized by the solution from the packaging material. Results from these experiments illustrate differences in the magnitude of solubilization obtained from solutions containing polysorbate 80 as compared to those composed of isopropanol/water. However, it was also demonstrated that their solubilization properties can be linked via a mathematical model. Copyright © 2016 Elsevier B.V. All rights reserved.

The role of tissue microstructure and water exchange in biophysical modelling of diffusion in white matter.

PubMed

Nilsson, Markus; van Westen, Danielle; Ståhlberg, Freddy; Sundgren, Pia C; Lätt, Jimmy

2013-08-01

Biophysical models that describe the outcome of white matter diffusion MRI experiments have various degrees of complexity. While the simplest models assume equal-sized and parallel axons, more elaborate ones may include distributions of axon diameters and axonal orientation dispersions. These microstructural features can be inferred from diffusion-weighted signal attenuation curves by solving an inverse problem, validated in several Monte Carlo simulation studies. Model development has been paralleled by microscopy studies of the microstructure of excised and fixed nerves, confirming that axon diameter estimates from diffusion measurements agree with those from microscopy. However, results obtained in vivo are less conclusive. For example, the amount of slowly diffusing water is lower than expected, and the diffusion-encoded signal is apparently insensitive to diffusion time variations, contrary to what may be expected. Recent understandings of the resolution limit in diffusion MRI, the rate of water exchange, and the presence of microscopic axonal undulation and axonal orientation dispersions may, however, explain such apparent contradictions. Knowledge of the effects of biophysical mechanisms on water diffusion in tissue can be used to predict the outcome of diffusion tensor imaging (DTI) and of diffusion kurtosis imaging (DKI) studies. Alterations of DTI or DKI parameters found in studies of pathologies such as ischemic stroke can thus be compared with those predicted by modelling. Observations in agreement with the predictions strengthen the credibility of biophysical models; those in disagreement could provide clues of how to improve them. DKI is particularly suited for this purpose; it is performed using higher b-values than DTI, and thus carries more information about the tissue microstructure. The purpose of this review is to provide an update on the current understanding of how various properties of the tissue microstructure and the rate of water exchange between microenvironments are reflected in diffusion MRI measurements. We focus on the use of biophysical models for extracting tissue-specific parameters from data obtained with single PGSE sequences on clinical MRI scanners, but results obtained with animal MRI scanners are also considered. While modelling of white matter is the central theme, experiments on model systems that highlight important aspects of the biophysical models are also reviewed.

Oceanic response to tropical cyclone `Phailin' in the Bay of Bengal

NASA Astrophysics Data System (ADS)

Pant, V.; Prakash, K. R.

2016-02-01

Vertical mixing largely explains surface cooling induced by Tropical Cyclones (TCs). However, TC-induced upwelling of deeper waters plays an important role as it partly balances the warming of subsurface waters induced by vertical mixing. Below 100 m, vertical advection results in cooling that persists for a few days after the storm. The present study investigates the integrated ocean response to tropical cyclone `Phaillin' (10-14 October 2013) in the Bay of Bengal (BoB) through both coupled and stand-alone ocean-atmosphere models. Two numerical experiments with different coupling configurations between Regional Ocean Modelling System (ROMS) and Weather Research and Forecasting (WRF) were performed to investigate the impact of Phailin cyclone on the surface and sub-surface oceanic parameters. In the first experiment, ocean circulation model ROMS observe surface wind forcing from a mesoscale atmospheric model (WRF with nested damin setup), while rest forcing parameters are supplied to ROMS from NCEP data. In the second experiment, all surface forcing data to ROMS directly comes from WRF. The modeling components and data fields exchanged between atmospheric and oceanic models are described. The coupled modeling system is used to identify model sensitivity by exchanging prognostic variable fields between the two model components during simulation of Phallin cyclone (10-14 October 2013) in the BoB.In general, the simulated Phailin cyclone track and intensities agree well with observations in WRF simulations. Further, the inter-comparison between stand-alone and coupled model simulations validated against observations highlights better performance of coupled modeling system in simulating the oceanic conditions during the Phailin cyclone event.

Ocean Raman Scattering in Satellite Backscatter UV Measurements

NASA Technical Reports Server (NTRS)

Vasilkov, Alexander P.; Joiner, Joanna; Gleason, James; Bhartia, Pawan; Bhartia, P. K. (Technical Monitor)

2002-01-01

Ocean Raman scattering significantly contributes to the filling-in of solar Fraunhofer lines measured by satellite backscatter ultraviolet (buy) instruments in the cloudless atmosphere over clear ocean waters. A model accounting for this effect in buy measurements is developed and compared with observations from the Global Ozone Monitoring Experiment (GONE). The model extends existing models for ocean Raman scattering to the UV spectral range. Ocean Raman scattering radiance is propagated through the atmosphere using a concept of the Lambert equivalent reflectively and an accurate radiative transfer model for Rayleigh scattering. The model and observations can be used to evaluate laboratory measurements of pure water absorption in the UV. The good agreement between model and observations suggests that buy instruments may be useful for estimating chlorophyll content.

Dynamics of nonreactive solute transport in the permafrost environment

NASA Astrophysics Data System (ADS)

Svyatskiy, D.; Coon, E. T.; Moulton, J. D.

2017-12-01

As part of the DOE Office of Science Next Generation Ecosystem Experiment, NGEE-Arctic, researchers are developing process-rich models to understand and predict the evolution of water sources and hydrologic flow pathways resulting from degrading permafrost. The sources and interaction of surface and subsurface water and flow paths are complex in space and time due to strong interplay between heterogeneous subsurface parameters, the seasonal to decadal evolution of the flow domain, climate driven melting and release of permafrost ice as a liquid water source, evolving surface topography and highly variable meteorological data. In this study, we seek to characterize the magnitude of vertical and lateral subsurface flows in a cold, wet tundra, polygonal landscape characteristic of the Barrow Peninsula, AK. To better understand the factors controlling water flux partitioning in these low gradient landscapes, NGEE researchers developed and are applying the Advanced Terrestrial Simulator (ATS), which fully couples surface and subsurface flow and energy processes, snow distribution and atmospheric forcing. Here we demonstrate the integration of a new solute transport model within the ATS, which enables the interpretation of applied and natural tracer experiments and observations aimed at quantifying water sources and flux partitioning. We examine the role of ice wedge polygon structure, freeze-thaw processes and soil properties on the seasonal transport of water within and through polygons features, and compare results to tracer experiments on 2D low-centered and high-centered transects corresponding to artificial as well as realistic topographical data from sites in polygonal tundra. These simulations demonstrate significant difference between flow patterns between permafrost and non-permafrost environments due to active layer freeze-thaw processes.

Modeling the Surface Water-Groundwater Interaction in Arid and Semi-Arid Regions Impacted by Agricultural Activities

NASA Astrophysics Data System (ADS)

Tian, Y.; Wu, B.; Zheng, Y.

2013-12-01

In many semi-arid and arid regions, interaction between surface water and groundwater plays an important role in the eco-hydrological system. The interaction is often complicated by agricultural activities such as surface water diversion, groundwater pumping, and irrigation. In existing surface water-groundwater integrated models, simulation of the interaction is often simplified, which could introduce significant simulation uncertainty under certain circumstance. In this study, GSFLOW, a USGS model coupling PRMS and MODFLOW, was improved to better characterize the surface water-groundwater interaction. The practices of water diversion from rivers, groundwater pumping and irrigation are explicitly simulated. In addition, the original kinematic wave routing method was replaced by a dynamic wave routing method. The improved model was then applied in Zhangye Basin (the midstream part of Heihe River Baisn), China, where the famous 'Silk Road' came through. It is a typical semi-arid region of the western China, with extensive agriculture in its oasis. The model was established and calibrated using the data in 2000-2008. A series of numerical experiments were conducted to evaluate the effect of those improvements. It has been demonstrated that with the improvements, the observed streamflow and groundwater level were better reproduced by the model. The improvements have a significant impact on the simulation of multiple fluxes associated with the interaction, such as groundwater discharge, riverbed seepage, infiltration, etc. Human activities were proved to be key elements of the water cycle in the study area. The study results have important implications to the water resources modeling and management in semi-arid and arid basins.

Motion and shape of partially non-wetting drops on inclined surfaces

NASA Astrophysics Data System (ADS)

Puthenveettil, Baburaj A.; Senthilkumar K, Vijaya; Hopfinger, E. J.; IIT Madras-LEGI Collaboration

2011-11-01

We study high Reynolds number (Re) motion of partially non- wetting liquid drops on inclined surfaces using (i) water on Fluoro-Alkyl Silane (FAS) coated glass and (ii) mercury on glass. The high hysteresis (35°) water drop experiments have been conducted for a range of inclination angles 26° < α <62° which give a range of Capillary numbers 0 . 0003 < Ca < 0 . 0075 and 137 < Re < 3142 . For low hysteresis (6°) mercury on glass experiments, 5 .5° < α < 14 .3° so that 0 . 0002 < Ca < 0 . 0023 and 3037 < Re < 20069 . It is shown that when Re >>103 for water and Re >> 19 for mercury, the observed velocities are accounted for by a boundary layer flow model. The dimensionless velocity in the inertial regime, Ca√{ Re } scales as the modified Bond number (Bom), while Ca Bom at low Re . We show that even at high Re , the dynamic contact angles (θd) depend only on Ca , similar to that in low Re drops. Only the model by Shikhmurzaev is consistent with the variation of dynamic contact angles in both mercury and water drops. We show that the corner transition at the rear of the mercury drop occurs at a finite, receding contact angle, which is predicted by a wedge flow model that we propose. For water drops, there is a direct transition to a rivulet from the oval shape at a critical ratio of receding to static contact angles.

Modeled interactive effects of precipitation, temperature, and [CO2] on ecosystem carbon and water dynamics in different climatic zones

Treesearch

Yiqi Luo; Dieter Gerten; Guerric Le Maire; William J. Parton; Ensheng Weng; Xuhui Zhou; Cindy Keough; Claus Beier; Philippe Ciais; Wolfgang Cramer; Jeffrey S. Dukes; Bridget Emmett; Paul J. Hanson; Alan Knapp; Sune Linder; Dan Nepstad; Lindsey. Rustad

2008-01-01

Interactive effects of multiple global change factors on ecosystem processes are complex. It is relatively expensive to explore those interactions in manipulative experiments. We conducted a modeling analysis to identify potentially important interactions and to stimulate hypothesis formulation for experimental research. Four models were used to quantify interactive...

Simple analytical model of evapotranspiration in the presence of roots.

PubMed

Cejas, Cesare M; Hough, L A; Castaing, Jean-Christophe; Frétigny, Christian; Dreyfus, Rémi

2014-10-01

Evaporation of water out of a soil involves complicated and well-debated mechanisms. When plant roots are added into the soil, water transfer between the soil and the outside environment is even more complicated. Indeed, plants provide an additional process of water transfer. Water is pumped by the roots, channeled to the leaf surface, and released into the surrounding air by a process called transpiration. Prediction of the evapotranspiration of water over time in the presence of roots helps keep track of the amount of water that remains in the soil. Using a controlled visual setup of a two-dimensional model soil consisting of monodisperse glass beads, we perform experiments on actual roots grown under different relative humidity conditions. We record the total water mass loss in the medium and the position of the evaporating front that forms within the medium. We then develop a simple analytical model that predicts the position of the evaporating front as a function of time as well as the total amount of water that is lost from the medium due to the combined effects of evaporation and transpiration. The model is based on fundamental principles of evaporation fluxes and includes empirical assumptions on the quantity of open stomata in the leaves, where water transpiration occurs. Comparison between the model and experimental results shows excellent prediction of the position of the evaporating front as well as the total mass loss from evapotranspiration in the presence of roots. The model also provides a way to predict the lifetime of a plant.

The truth is out there: measured, calculated and modelled benthic fluxes.

NASA Astrophysics Data System (ADS)

Pakhomova, Svetlana; Protsenko, Elizaveta

2016-04-01

In a modern Earth science there is a great importance of understanding the processes, forming the benthic fluxes as one of element sources or sinks to or from the water body, which affects the elements balance in the water system. There are several ways to assess benthic fluxes and here we try to compare the results obtained by chamber experiments, calculated from porewater distributions and simulated with model. Benthic fluxes of dissolved elements (oxygen, nitrogen species, phosphate, silicate, alkalinity, iron and manganese species) were studied in the Baltic and Black Seas from 2000 to 2005. Fluxes were measured in situ using chamber incubations (Jch) and at the same time sediment cores were collected to assess the porewater distribution at different depths to calculate diffusive fluxes (Jpw). Model study was carried out with benthic-pelagic biogeochemical model BROM (O-N-P-Si-C-S-Mn-Fe redox model). It was applied to simulate biogeochemical structure of the water column and upper sediment and to assess the vertical fluxes (Jmd). By the behaviour at the water-sediment interface all studied elements can be divided into three groups: (1) elements which benthic fluxes are determined by the concentrations gradient only (Si, Mn), (2) elements which fluxes depend on redox conditions in the bottom water (Fe, PO4, NH4), and (3) elements which fluxes are strongly connected with organic matter fate (O2, Alk, NH4). For the first group it was found that measured fluxes are always higher than calculated diffusive fluxes (1.5

Aquifer recharge with reclaimed water in the Llobregat Delta. Laboratory batch experiments and field test site.

NASA Astrophysics Data System (ADS)

Tobella, J.

2010-05-01

Summary Spain, as most other Mediterranean countries, faces near future water shortages, generalized pollution and loss of water dependent ecosystems. Aquifer recharge represents a promising option to become a source for indirect potable reuse purposes but presence of pathogens as well as organic and inorganic pollutants should be avoided. To this end, understanding the processes of biogeochemical degradation occurring within the aquifer during infiltration is capital. A set of laboratory batch experiments has been assembled in order to assess the behaviour of selected pesticides, drugs, estrogens, surfactant degradation products, biocides and phthalates under different redox conditions. Data collected during laboratory experiments and monitoring activities at the Sant Vicenç dels Horts test site will be used to build and calibrate a numerical model (i) of the physical-chemical-biochemical processes occurring in the batches and (ii) of multicomponent reactive transport in the unsaturated/saturated zone at the test site. Keywords Aquifer recharge, batch experiments, emerging micropollutants, infiltration, numerical model, reclaimed water, redox conditions, Soil Aquifer Treatment (SAT). 1. Introduction In Spain, the Llobregat River and aquifers, which supply water to Barcelona, have been overexploited for years and therefore, suffer from serious damages: the river dries up on summer, riparian vegetation has disappeared and seawater has intruded the aquifer. In a global context, solutions to water stress problems are urgently needed yet must be sustainable, economical and safe. Recent developments of analytical techniques detect the presence of the so-called "emerging" organic micropollutants in water and soils. Such compounds may affect living organisms when occurring in the environment at very low concentrations (microg/l or ng/l). In wastewater and drinking water treatment plants, a remarkable removal of these chemicals from water can be obtained only using advanced and costly treatments. Nevertheless, a number of studies are demonstrating that physical, chemical and biochemical processes associated with water movement within the subsoil represent a natural alternative way to reduce the presence of these contaminants. This processes are called Soil Aquifer Treatment (SAT). Aquifer recharge will become a source for indirect potable reuse purposes as long as the presence of pathogens and organic and inorganic pollutants is avoided. To this end, understanding the biogeochemical degradation processes occurring within the aquifer during infiltration is capital. 2. Laboratory batch experiments A set of laboratory batch experiments has been assembled to assess the behaviour of selected pesticides, drugs, estrogens, surfactant degradation products, biocides and phthalates under different redox conditions. The setup of the experiments consists of glass bottles containing 120 g of soil and 240 ml of synthetic water spiked with the mix of micropollutants. A source of easily degradable organic carbon and, depending on the type of test, electron acceptors are added in order to yield aerobic respiration and nitrate/iron/manganese/sulphate reduction conditions. The evolution of the processes is monitored by sacrificing duplicate bottles according to a defined schedule and analysing water for major and minor components as well as for micropollutants. Results from biotic tests are compared with abiotic ones in order to discern biodegradation from other chemical processes. The soil, the synthetic water and the micropollutants selected for the experiments are representative of a test site in the nearby of Barcelona (Spain) where artificial recharge of groundwater through ponds is going to be performed using river water or tertiary effluent from a waste water treatment plant. The results of the experiments improve the knowledge on the behaviour of the selected micropollutants under different redox conditions and provide with useful information on the conditions to develop at the test site during artificial recharge. The data collected during the laboratory experiments and in the test site will be used to build and calibrate a numerical model of the physical-chemical-biochemical processes developing in the batches and of multicomponent reactive transport in the unsaturated/saturated zone in the test site area. 3. Field test site The infiltration site of Sant Vicenç dels Horts has been selected to assessing the biogeochemical processes occurring during SAT. The system consists of two ponds that have been built as compensatory measure for the reduction in natural recharge caused by the construction of the High Speed Train Line. The first pond acts as a decantation pond while the second one acts as an infiltration basin (Figure 1). Recharge water comes from the tertiary treatment plant of the El Prat de Llobregat WWTP and the river (?). The CUADLL (Lower Llobregat Aquifer End-Users Community) is now managing the system operation. Tasks that are currently being carried out at this Test Site aims at (i) improving the local experience on MAR through infiltration ponds operational aspects and (ii) monitoring the changes in water quality during the recharge processes (unsaturated and saturated zone). Special attention is being paid to the fate of emerging organic pollutants (pharmaceuticals, surfactants, pesticides, etc.). The yielding of the monitoring will be compared with the results from the laboratory batch experiments on the behaviour of selected emerging organic pollutants. To this end, observation wells have been constructed, pressure / temperature / electrical conductivity transducers have been installed and the vadose zone under the infiltration pond has been instrumented (tensiometers, water content probes and suction cups). In addition double ring and infiltration tests have been performed in order to forecast the infiltration capacity of the basin.

Response in the trophic state of stratified lakes to changes in hydrology and water level: potential effects of climate change

USGS Publications Warehouse

Robertson, Dale M.; Rose, William J.

2011-01-01

To determine how climate-induced changes in hydrology and water level may affect the trophic state (productivity) of stratified lakes, two relatively pristine dimictic temperate lakes in Wisconsin, USA, were examined. Both are closed-basin lakes that experience changes in water level and degradation in water quality during periods of high water. One, a seepage lake with no inlets or outlets, has a small drainage basin and hydrology dominated by precipitation and groundwater exchange causing small changes in water and phosphorus (P) loading, which resulted in small changes in water level, P concentrations, and productivity. The other, a terminal lake with inlets but no outlets, has a large drainage basin and hydrology dominated by runoff causing large changes in water and P loading, which resulted in large changes in water level, P concentrations, and productivity. Eutrophication models accurately predicted the effects of changes in hydrology, P loading, and water level on their trophic state. If climate changes, larger changes in hydrology and water levels than previously observed could occur. If this causes increased water and P loading, stratified (dimictic and monomictic) lakes are expected to experience higher water levels and become more eutrophic, especially those with large developed drainage basins.

Integration of remote sensing and hydrologic modeling through multi-disciplinary semiarid field campaigns: Moonsoon 1990, Walnut Gulch 1992, and SALSA-MEX

NASA Technical Reports Server (NTRS)

Moran, M. S.; Goodrich, D. C.; Kustas, W. P.

1994-01-01

A research and modeling strategy is presented for development of distributed hydrologic models given by a combination of remotely sensed and ground based data. In support of this strategy, two experiments Moonsoon'90 and Walnut Gulch'92 were conducted in a semiarid rangeland southeast of Tucson, Arizona, (U.S.) and a third experiment, the SALSA-MEX (Semi Arid Land Surface Atmospheric Mountain Experiment) was proposed. Results from the Moonsoon'90 experiment substantially advanced the understanding of the hydrologic and atmospheric fluxes in an arid environment and provided insight into the use of remote sensing data for hydrologic modeling. The Walnut Gulch'92 experiment addressed the seasonal hydrologic dynamics of the region and the potential of combined optical microwave remote sensing for hydrologic applications. SALSA-MEX will combine measurements and modeling to study hydrologic processes influenced by surrounding mountains, such as enhanced precipitation, snowmelt and recharge to ground water aquifers. The results from these experiments, along with the extensive experimental data bases, should aid the research community in large scale modeling of mass and energy exchanges across the soil-plant-atmosphere interface.

Hydraulic experiment on formation mechanism of tsunami deposit and verification of sediment transport model for tsunamis

NASA Astrophysics Data System (ADS)

Yamamoto, A.; Takahashi, T.; Harada, K.; Sakuraba, M.; Nojima, K.

2017-12-01

An underestimation of the 2011 Tohoku tsunami caused serious damage in coastal area. Reconsideration for tsunami estimation needs knowledge of paleo tsunamis. The historical records of giant tsunamis are limited, because they had occurred infrequently. Tsunami deposits may include many of tsunami records and are expected to analyze paleo tsunamis. However, present research on tsunami deposits are not able to estimate the tsunami source and its magnitude. Furthermore, numerical models of tsunami and its sediment transport are also important. Takahashi et al. (1999) proposed a model of movable bed condition due to tsunamis, although it has some issues. Improvement of the model needs basic data on sediment transport and deposition. This study investigated the formation mechanism of tsunami deposit by hydraulic experiment using a two-dimensional water channel with slope. In a fixed bed condition experiment, velocity, water level and suspended load concentration were measured at many points. In a movable bed condition, effects of sand grains and bore wave on the deposit were examined. Yamamoto et al. (2016) showed deposition range varied with sand grain sizes. In addition, it is revealed that the range fluctuated by number of waves and wave period. The measurements of velocity and water level showed that flow was clearly different near shoreline and in run-up area. Large velocity by return flow was affected the amount of sand deposit near shoreline. When a cutoff wall was installed on the slope, the amount of sand deposit repeatedly increased and decreased. Especially, sand deposit increased where velocity decreased. Takahashi et al. (1999) adapted the proposed model into Kesennuma bay when the 1960 Chilean tsunami arrived, although the amount of sand transportation was underestimated. The cause of the underestimation is inferred that the velocity of this model was underestimated. A relationship between velocity and sediment transport has to be studied in detail, but observation of velocity in Kesennnuma bay had a low accuracy. On the other hand, this hydraulic experiment measured accurate velocity and sand deposition distribution of various condition. Based on these data, we tried more accurate verification of the model of Takahashi et al. (1999).

Energy Saving Melting and Revert Reduction Technology (Energy-SMARRT): Clean Steel Casting Production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuyucak, Selcuk; Li, Delin

2013-12-31

Inclusions in steel castings can cause rework, scrap, poor machining, and reduced casting performance, which can obviously result in excess energy consumption. Significant progress in understanding inclusion source, formation and control has been made. Inclusions can be defined as non-metallic materials such as refractory, sand, slag, or coatings, embedded in a metallic matrix. This research project has focused on the mold filling aspects to examine the effects of pouring methods and gating designs on the steel casting cleanliness through water modeling, computer modeling, and melting/casting experiments. Early in the research project, comprehensive studies of bottom-pouring water modeling and low-alloy steelmore » casting experiments were completed. The extent of air entrainment in bottom-poured large castings was demonstrated by water modeling. Current gating systems are designed to prevent air aspiration. However, air entrainment is equally harmful and no prevention measures are in current practice. In this study, new basin designs included a basin dam, submerged nozzle, and nozzle extension. The entrained air and inclusions from the gating system were significantly reduced using the new basin method. Near the end of the project, there has been close collaboration with Wescast Industries Inc., a company manufacturing automotive exhaust components. Both computer modeling using Magma software and melting/casting experiments on thin wall turbo-housing stainless steel castings were completed in this short period of time. Six gating designs were created, including the current gating on the pattern, non-pressurized, partially pressurized, naturally pressurized, naturally pressurized without filter, and radial choke gating without filter, for Magma modeling. The melt filling velocity and temperature were determined from the modeling. Based on the simulation results, three gating designs were chosen for further melting and casting experiments on the same casting pattern using the lip pouring method. It was observed again that gating designs greatly influenced the melt filling velocity and the number of inclusion defects. The radial choked gating showed improvements in casting cleanliness and yield over the other gatings, even though no mold filters were used in the gating system.« less

Validation of MCNP: SPERT-D and BORAX-V fuel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crawford, C.; Palmer, B.

1992-11-01

This report discusses critical experiments involving SPERT-D{sup 1,2} fuel elements and BORAX-V{sup 3-8} fuel which have been modeled and calculations performed with MCNP. MCNP is a Monte Carlo based transport code. For this study continuous-energy nuclear data from the ENDF/B-V cross section library was used. The SPERT-D experiments consisted of various arrays of fuel elements moderated and reflected with either water or a uranyl nitrate solution. Some SPERT-D experiments used cadmium as a fixed neutron poison, while others were poisoned with various concentrations of boron in the moderating/reflecting solution. ne BORAX-V experiments were arrays of either boiling fuel rod assembliesmore » or superheater assemblies, both types of arrays were moderated and reflected with water. In one boiling fuel experiment, two fuel rods were replaced with borated stainless steel poison rods.« less

Validation of MCNP: SPERT-D and BORAX-V fuel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crawford, C.; Palmer, B.

1992-11-01

This report discusses critical experiments involving SPERT-D[sup 1,2] fuel elements and BORAX-V[sup 3-8] fuel which have been modeled and calculations performed with MCNP. MCNP is a Monte Carlo based transport code. For this study continuous-energy nuclear data from the ENDF/B-V cross section library was used. The SPERT-D experiments consisted of various arrays of fuel elements moderated and reflected with either water or a uranyl nitrate solution. Some SPERT-D experiments used cadmium as a fixed neutron poison, while others were poisoned with various concentrations of boron in the moderating/reflecting solution. ne BORAX-V experiments were arrays of either boiling fuel rod assembliesmore » or superheater assemblies, both types of arrays were moderated and reflected with water. In one boiling fuel experiment, two fuel rods were replaced with borated stainless steel poison rods.« less

Water Sorption in Electron-Beam Evaporated SiO2 on QCM Crystals and Its Influence on Polymer Thin Film Hydration Measurements.

PubMed

Kushner, Douglas I; Hickner, Michael A

2017-05-30

Spectroscopic ellipsometry (SE) and quartz crystal microbalance (QCM) measurements are two critical characterization techniques routinely employed for hydration studies of polymer thin films. Water uptake by thin polymer films is an important area of study to investigate antifouling surfaces, to probe the swelling of thin water-containing ionomer films, and to conduct fundamental studies of polymer brush hydration and swelling. SiO 2 -coated QCM crystals, employed as substrates in many of these hydration studies, show porosity in the thin electron-beam (e-beam) evaporated SiO 2 layer. The water sorption into this porous SiO 2 layer requires correction of the optical and mass characterization of the hydrated polymer due to changes in the SiO 2 layer as it sorbs water. This correction is especially important when experiments on SiO 2 -coated QCM crystals are compared to measurements on Si wafers with dense native SiO 2 layers. Water adsorption filling void space during hydration in ∼200-260 nm thick SiO 2 layers deposited on a QCM crystal resulted in increased refractive index of the layer during water uptake experiments. The increased refractive index led to artificially higher polymer swelling in the optical modeling of the hydration experiments. The SiO 2 -coated QCM crystals showed between 6 and 8% void as measured by QCM and SE, accounting for 60%-85% of the measured polymer swelling in the low humidity regime (<20% RH) and 25%-40% of the polymer swelling in the high humidity regime (>70% RH) from optical modeling for 105 and 47 nm thick sulfonated polymer films. Correcting the refractive index of the SiO 2 layer for its water content resulted in polymer swelling that successfully resembled swelling measured on a silicon wafer with nonporous native oxide.