NASA Astrophysics Data System (ADS)
Kravtsov, Alexander L.; Bobyleva, Elena V.; Grebenyukova, Tatyana P.; Kuznetsov, Oleg S.; Kulyash, Youri V.
2002-07-01
A quantitative flow microfluorometric method was used to study the intensity of human blood phagocyte degranulation in response to viable staphylococcus aureus or Yersinia pestis cells. Microorganisms were added directly to defibrinated whole blood. Uninfected and infected blood samples were incubated at 37 degrees C to 8 h. The results were recorded in dynamics after the staining of whole blood with acridine orange solution. Lymphocytes with a low azurophilic granule per cell content were discriminated from phagocytes by the measurement of single cell red cytoplasmic granule fluorescence. 30,000 cells in each sample were examined. S. aureus cells caused a dose-dependent decrease in the number of phagocytes having a high red cytoplasmic fluorescence intensity and a corresponding increase in the weakly fluorescence cell population. In the presence of an initial S. aureus-to-phagocyte ratio more than 1:1, degranulation was measured after 3 h of incubation and to 8 h the percentage of degranulated phagocytes was at least 100 percent Y. pestis cells grown for 48 h at 28 degrees C caused at same condition as the degranulation only about 50 percent of cells. Y.pestis EV cells preincubated in broth for 12 h at 37 degrees C did no stimulate the phahocyte degranulation. The results of these studies suggest that analysis of cell populations via flow microfluorimeter technology may be a powerful tool in analysis bacterial infection.
Unified approach for incompressible flows
NASA Technical Reports Server (NTRS)
Chang, Tyne-Hsien
1995-01-01
A unified approach for solving incompressible flows has been investigated in this study. The numerical CTVD (Centered Total Variation Diminishing) scheme used in this study was successfully developed by Sanders and Li for compressible flows, especially for the high speed. The CTVD scheme possesses better mathematical properties to damp out the spurious oscillations while providing high-order accuracy for high speed flows. It leads us to believe that the CTVD scheme can equally well apply to solve incompressible flows. Because of the mathematical difference between the governing equations for incompressible and compressible flows, the scheme can not directly apply to the incompressible flows. However, if one can modify the continuity equation for incompressible flows by introducing pseudo-compressibility, the governing equations for incompressible flows would have the same mathematical characters as compressible flows. The application of the algorithm to incompressible flows thus becomes feasible. In this study, the governing equations for incompressible flows comprise continuity equation and momentum equations. The continuity equation is modified by adding a time-derivative of the pressure term containing the artificial compressibility. The modified continuity equation together with the unsteady momentum equations forms a hyperbolic-parabolic type of time-dependent system of equations. Thus, the CTVD schemes can be implemented. In addition, the physical and numerical boundary conditions are properly implemented by the characteristic boundary conditions. Accordingly, a CFD code has been developed for this research and is currently under testing. Flow past a circular cylinder was chosen for numerical experiments to determine the accuracy and efficiency of the code. The code has shown some promising results.
Unified approach for incompressible flows
NASA Technical Reports Server (NTRS)
Chang, Tyne-Hsien
1993-01-01
An unified approach for solving both compressible and incompressible flows was investigated in this study. The difference in CFD code development between incompressible and compressible flows is due to the mathematical characteristics. However, if one can modify the continuity equation for incompressible flows by introducing pseudocompressibility, the governing equations for incompressible flows would have the same mathematical characters as compressible flows. The application of a compressible flow code to solve incompressible flows becomes feasible. Among numerical algorithms developed for compressible flows, the Centered Total Variation Diminishing (CTVD) schemes possess better mathematical properties to damp out the spurious oscillations while providing high-order accuracy for high speed flows. It leads us to believe that CTVD schemes can equally well solve incompressible flows. In this study, the governing equations for incompressible flows include the continuity equation and momentum equations. The continuity equation is modified by adding a time-derivative of the pressure term containing the artificial compressibility. The modified continuity equation together with the unsteady momentum equations forms a hyperbolic-parabolic type of time-dependent system of equations. The continuity equation is modified by adding a time-derivative of the pressure term containing the artificial compressibility. The modified continuity equation together with the unsteady momentum equations forms a hyperbolic-parabolic type of time-dependent system of equations. Thus, the CTVD schemes can be implemented. In addition, the boundary conditions including physical and numerical boundary conditions must be properly specified to obtain accurate solution. The CFD code for this research is currently in progress. Flow past a circular cylinder will be used for numerical experiments to determine the accuracy and efficiency of the code before applying this code to more specific applications.
Flow Analysis: A Novel Approach For Classification.
Vakh, Christina; Falkova, Marina; Timofeeva, Irina; Moskvin, Alexey; Moskvin, Leonid; Bulatov, Andrey
2016-09-01
We suggest a novel approach for classification of flow analysis methods according to the conditions under which the mass transfer processes and chemical reactions take place in the flow mode: dispersion-convection flow methods and forced-convection flow methods. The first group includes continuous flow analysis, flow injection analysis, all injection analysis, sequential injection analysis, sequential injection chromatography, cross injection analysis, multi-commutated flow analysis, multi-syringe flow injection analysis, multi-pumping flow systems, loop flow analysis, and simultaneous injection effective mixing flow analysis. The second group includes segmented flow analysis, zone fluidics, flow batch analysis, sequential injection analysis with a mixing chamber, stepwise injection analysis, and multi-commutated stepwise injection analysis. The offered classification allows systematizing a large number of flow analysis methods. Recent developments and applications of dispersion-convection flow methods and forced-convection flow methods are presented. PMID:26364745
Anisotropic flow in transport + hydrodynamics hybrid approaches
NASA Astrophysics Data System (ADS)
Petersen, Hannah
2014-12-01
This contribution to the focus issue covers anisotropic flow in hybrid approaches. The historical development of hybrid approaches and their impact on the interpretation of flow measurements is reviewed. The major ingredients of a hybrid approach and the transition criteria between transport and hydrodynamics are discussed. The results for anisotropic flow in (event-by-event) hybrid approaches are presented. Some hybrid approaches rely on hadronic transport for the late stages for the reaction (so called afterburner) and others employ transport approaches for the early non-equilibrium evolution. In addition, there are ‘full’ hybrid calculations where a fluid evolution is dynamically embedded in a transport simulation. After demonstrating the success of hybrid approaches at high Relativistic Heavy Ion Collider and Large Hadron Collider energies, existing hybrid caluclations for collective flow observables at lower beam energies are discussed and remaining challenges outlined.
Lattice Boltzmann approach for complex nonequilibrium flows.
Montessori, A; Prestininzi, P; La Rocca, M; Succi, S
2015-10-01
We present a lattice Boltzmann realization of Grad's extended hydrodynamic approach to nonequilibrium flows. This is achieved by using higher-order isotropic lattices coupled with a higher-order regularization procedure. The method is assessed for flow across parallel plates and three-dimensional flows in porous media, showing excellent agreement of the mass flow with analytical and numerical solutions of the Boltzmann equation across the full range of Knudsen numbers, from the hydrodynamic regime to ballistic motion. PMID:26565365
Multidomain approach for calculating compressible flows
NASA Technical Reports Server (NTRS)
Cambier, L.; Chazzi, W.; Veuillot, J. P.; Viviand, H.
1982-01-01
A multidomain approach for calculating compressible flows by using unsteady or pseudo-unsteady methods is presented. This approach is based on a general technique of connecting together two domains in which hyperbolic systems (that may differ) are solved with the aid of compatibility relations associated with these systems. Some examples of this approach's application to calculating transonic flows in ideal fluids are shown, particularly the adjustment of shock waves. The approach is then applied to treating a shock/boundary layer interaction problem in a transonic channel.
Multigrid Approach to Incompressible Viscous Cavity Flows
NASA Technical Reports Server (NTRS)
Wood, William A.
1996-01-01
Two-dimensional incompressible viscous driven-cavity flows are computed for Reynolds numbers on the range 100-20,000 using a loosely coupled, implicit, second-order centrally-different scheme. Mesh sequencing and three-level V-cycle multigrid error smoothing are incorporated into the symmetric Gauss-Seidel time-integration algorithm. Parametrics on the numerical parameters are performed, achieving reductions in solution times by more than 60 percent with the full multigrid approach. Details of the circulation patterns are investigated in cavities of 2-to-1, 1-to-1, and 1-to-2 depth to width ratios.
PDF approach for compressible turbulent reacting flows
NASA Technical Reports Server (NTRS)
Hsu, A. T.; Tsai, Y.-L. P.; Raju, M. S.
1993-01-01
The objective of the present work is to develop a probability density function (pdf) turbulence model for compressible reacting flows for use with a CFD flow solver. The probability density function of the species mass fraction and enthalpy are obtained by solving a pdf evolution equation using a Monte Carlo scheme. The pdf solution procedure is coupled with a compressible CFD flow solver which provides the velocity and pressure fields. A modeled pdf equation for compressible flows, capable of capturing shock waves and suitable to the present coupling scheme, is proposed and tested. Convergence of the combined finite-volume Monte Carlo solution procedure is discussed, and an averaging procedure is developed to provide smooth Monte-Carlo solutions to ensure convergence. Two supersonic diffusion flames are studied using the proposed pdf model and the results are compared with experimental data; marked improvements over CFD solutions without pdf are observed. Preliminary applications of pdf to 3D flows are also reported.
New flow cytometry approaches in equine andrology.
Peña, Fernando J; Ortega Ferrusola, Cristina; Martín Muñoz, Patricia
2016-07-01
Flow cytometry is currently recognized as a robust tool for the evaluation of sperm quality and function. However, within equine reproduction, this technique has not reached the sophistication of other areas of biology and medicine. In recent years, more sophisticated flow cytometers have been introduced in andrology laboratories, and the number of tests that can be potentially used in the evaluation of sperm physiology has increased accordingly. In this review, recent advances in the evaluation of stallion spermatozoa will be discussed. These new techniques in flow cytometry are able to simultaneously measure damage to different sperm regions and/or changes in functionality. PMID:27160445
The pdf approach to turbulent flow
NASA Technical Reports Server (NTRS)
Kollmann, W.
1990-01-01
This paper provides a detailed discussion of the theory and application of probability density function (pdf) methods, which provide a complete statistical description of turbulent flow fields at a single point or a finite number of points. The basic laws governing the flow of Newtonian fluids are set up in the Eulerian and the Lagrangian frame, and the exact and linear equations for the characteristic functionals in those frames are discussed. Pdf equations in both frames are derived as Fourier transforms of the equations of the characteristic functions. Possible formulations for the nonclosed terms in the pdf equation are discussed, their properties are assessed, and closure modes for the molecular-transport and the fluctuating pressure-gradient terms are reviewed. The application of pdf methods to turbulent combustion flows, supersonic flows, and the interaction of turbulence with shock waves is discussed.
Parametric and experimental analysis using a power flow approach
NASA Technical Reports Server (NTRS)
Cuschieri, J. M.
1990-01-01
A structural power flow approach for the analysis of structure-borne transmission of vibrations is used to analyze the influence of structural parameters on transmitted power. The parametric analysis is also performed using the Statistical Energy Analysis approach and the results are compared with those obtained using the power flow approach. The advantages of structural power flow analysis are demonstrated by comparing the type of results that are obtained by the two analytical methods. Also, to demonstrate that the power flow results represent a direct physical parameter that can be measured on a typical structure, an experimental study of structural power flow is presented. This experimental study presents results for an L shaped beam for which an available solution was already obtained. Various methods to measure vibrational power flow are compared to study their advantages and disadvantages.
Magnetohydrodynamic equilibria with incompressible flows: Symmetry approach
Cicogna, G.; Pegoraro, F.
2015-02-15
We identify and discuss a family of azimuthally symmetric, incompressible, magnetohydrodynamic plasma equilibria with poloidal and toroidal flows in terms of solutions of the Generalized Grad Shafranov (GGS) equation. These solutions are derived by exploiting the incompressibility assumption, in order to rewrite the GGS equation in terms of a different dependent variable, and the continuous Lie symmetry properties of the resulting equation and, in particular, a special type of “weak” symmetries.
Annular flow optimization: A new integrated approach
Maglione, R.; Robotti, G.; Romagnoli, R.
1997-07-01
During the drilling stage of an oil and gas well the hydraulic circuit of the mud assumes great importance with respect to most of the numerous and various constituting parts (mostly in the annular sections). Each of them has some points to be satisfied in order to guarantee both the safety of the operations and the performance optimization of each of the single elements of the circuit. The most important tasks for the annular part of the drilling hydraulic circuit are the following: (1) Maximum available pressure to the last casing shoe; (2) avoid borehole wall erosions; and (3) guarantee the hole cleaning. A new integrated system considering all the elements of the annular part of the drilling hydraulic circuit and the constraints imposed from each of them has been realized. In this way the family of the flow parameters (mud rheology and pump rate) satisfying simultaneously all the variables of the annular section has been found. Finally two examples regarding a standard and narrow annular section (slim hole) will be reported, showing briefly all the steps of the calculations until reaching the optimum flow parameters family (for that operational condition of drilling) that satisfies simultaneous all the flow parameters limitations imposed by the elements of the annular section circuit.
Receptivity in parallel flows: An adjoint approach
NASA Technical Reports Server (NTRS)
Hill, D. Christopher
1993-01-01
Linear receptivity studies in parallel flows are aimed at understanding how external forcing couples to the natural unstable motions which a flow can support. The vibrating ribbon problem models the original Schubauer and Skramstad boundary layer experiment and represents the classic boundary layer receptivity problem. The process by which disturbances are initiated in convectively-unstable jets and shear layers has also received attention. Gaster was the first to handle the boundary layer analysis with the recognition that spatial modes, rather than temporal modes, were relevant when studying convectively-unstable flows that are driven by a time-harmonic source. The amplitude of the least stable spatial mode, far downstream of the source, is related to the source strength by a coupling coefficient. The determination of this coefficient is at the heart of this type of linear receptivity study. The first objective of the present study was to determine whether the various wave number derivative factors, appearing in the coupling coefficients for linear receptivity problems, could be reexpressed in a simpler form involving adjoint eigensolutions. Secondly, it was hoped that the general nature of this simplification could be shown; indeed, a rather elegant characterization of the receptivity properties of spatial instabilities does emerge. The analysis is quite distinct from the usual Fourier-inversion procedures, although a detailed knowledge of the spectrum of the Orr-Sommerfeld equation is still required. Since the cylinder wake analysis proved very useful in addressing control considerations, the final objective was to provide a foundation upon which boundary layer control theory may be developed.
A Logical Approach to the Statement of Cash Flows
ERIC Educational Resources Information Center
Petro, Fred; Gean, Farrell
2014-01-01
Of the three financial statements in financial reporting, the Statement of Cash Flows (SCF) is perhaps the most challenging. The most difficult aspect of the SCF is in developing an understanding of how previous transactions are finalized in this document. The purpose of this paper is to logically explain the indirect approach of cash flow whereby…
Traffic flow forecasting: Comparison of modeling approaches
Smith, B.L.; Demetsky, M.J.
1997-08-01
The capability to forecast traffic volume in an operational setting has been identified as a critical need for intelligent transportation systems (ITS). In particular, traffic volume forecasts will support proactive, dynamic traffic control. However, previous attempts to develop traffic volume forecasting models have met with limited success. This research effort focused on developing traffic volume forecasting models for two sites on Northern Virginia`s Capital Beltway. Four models were developed and tested for the freeway traffic flow forecasting problem, which is defined as estimating traffic flow 15 min into the future. They were the historical average, time-series, neural network, and nonparametric regression models. The nonparametric regression model significantly outperformed the other models. A Wilcoxon signed-rank test revealed that the nonparametric regression model experienced significantly lower errors than the other models. In addition, the nonparametric regression model was easy to implement, and proved to be portable, performing well at two distinct sites. Based on its success, research is ongoing to refine the nonparametric regression model and to extend it to produce multiple interval forecasts.
Neural Flows in Hopfield Network Approach
NASA Astrophysics Data System (ADS)
Ionescu, Carmen; Panaitescu, Emilian; Stoicescu, Mihai
2013-12-01
In most of the applications involving neural networks, the main problem consists in finding an optimal procedure to reduce the real neuron to simpler models which still express the biological complexity but allow highlighting the main characteristics of the system. We effectively investigate a simple reduction procedure which leads from complex models of Hodgkin-Huxley type to very convenient binary models of Hopfield type. The reduction will allow to describe the neuron interconnections in a quite large network and to obtain information concerning its symmetry and stability. Both cases, on homogeneous voltage across the membrane and inhomogeneous voltage along the axon will be tackled out. Few numerical simulations of the neural flow based on the cable-equation will be also presented.
A convex complementarity approach for simulating large granular flows.
Tasora, A.; Anitescu, M.; Mathematics and Computer Science; Univ. degli Studi di Parma
2010-07-01
Aiming at the simulation of dense granular flows, we propose and test a numerical method based on successive convex complementarity problems. This approach originates from a multibody description of the granular flow: all the particles are simulated as rigid bodies with arbitrary shapes and frictional contacts. Unlike the discrete element method (DEM), the proposed approach does not require small integration time steps typical of stiff particle interaction; this fact, together with the development of optimized algorithms that can run also on parallel computing architectures, allows an efficient application of the proposed methodology to granular flows with a large number of particles. We present an application to the analysis of the refueling flow in pebble-bed nuclear reactors. Extensive validation of our method against both DEM and physical experiments results indicates that essential collective characteristics of dense granular flow are accurately predicted.
A mechanistic approach to blood flow occlusion.
Loenneke, J P; Wilson, G J; Wilson, J M
2010-01-01
Low-Intensity occlusion training provides a unique beneficial training mode for promoting muscle hypertrophy. Training at intensities as low as 20% 1RM with moderate vascular occlusion results in muscle hypertrophy in as little as three weeks. The primary mechanisms by which occlusion training is thought to stimulate growth include, metabolic accumulation, which stimulates a subsequent increase in anabolic growth factors, fast-twitch fiber recruitment (FT), and increased protein synthesis through the mammalian target of rapamycin (mTOR) pathway. Heat shock proteins, Nitric oxide synthase-1 (NOS-1) and Myostatin have also been shown to be affected by an occlusion stimulus. In conclusion, low-intensity occlusion training appears to work through a variety of mechanisms. The research behind these mechanisms is incomplete thus far, and requires further examination, primarily to identify the actual metabolite responsible for the increase in GH with occlusion, and determine which mechanisms are associated to a greater degree with the hypertrophic/anti-catabolic changes seen with blood flow restriction. PMID:19885776
Parametric and experimental analysis using a power flow approach
NASA Technical Reports Server (NTRS)
Cuschieri, J. M.
1988-01-01
Having defined and developed a structural power flow approach for the analysis of structure-borne transmission of structural vibrations, the technique is used to perform an analysis of the influence of structural parameters on the transmitted energy. As a base for comparison, the parametric analysis is first performed using a Statistical Energy Analysis approach and the results compared with those obtained using the power flow approach. The advantages of using structural power flow are thus demonstrated by comparing the type of results obtained by the two methods. Additionally, to demonstrate the advantages of using the power flow method and to show that the power flow results represent a direct physical parameter that can be measured on a typical structure, an experimental investigation of structural power flow is also presented. Results are presented for an L-shaped beam for which an analytical solution has already been obtained. Furthermore, the various methods available to measure vibrational power flow are compared to investigate the advantages and disadvantages of each method.
An engineering based approach for hydraulic computations in river flows
NASA Astrophysics Data System (ADS)
Di Francesco, S.; Biscarini, C.; Pierleoni, A.; Manciola, P.
2016-06-01
This paper presents an engineering based approach for hydraulic risk evaluation. The aim of the research is to identify a criteria for the choice of the simplest and appropriate model to use in different scenarios varying the characteristics of main river channel. The complete flow field, generally expressed in terms of pressure, velocities, accelerations can be described through a three dimensional approach that consider all the flow properties varying in all directions. In many practical applications for river flow studies, however, the greatest changes occur only in two dimensions or even only in one. In these cases the use of simplified approaches can lead to accurate results, with easy to build and faster simulations. The study has been conducted taking in account a dimensionless parameter of channels (ratio of curvature radius and width of the channel (R/B).
Optimal active power dispatch by network flow approach
Carvalho, M.F. ); Soares, S.; Ohishi, T. )
1988-11-01
In this paper the optimal active power dispatch problem is formulated as a nonlinear capacitated network flow problem with additional linear constraints. Transmission flow limits and both Kirchhoff's laws are taken into account. The problem is solved by a Generalized Upper Bounding technique that takes advantage of the network flow structure of the problem. The new approach has potential applications on power systems problems such as economic dispatch, load supplying capability, minimum load shedding, and generation-transmission reliability. The paper also reviews the use of transportation models for power system analysis. A detailed illustrative example is presented.
An active, collaborative approach to learning skills in flow cytometry.
Fuller, Kathryn; Linden, Matthew D; Lee-Pullen, Tracey; Fragall, Clayton; Erber, Wendy N; Röhrig, Kimberley J
2016-06-01
Advances in science education research have the potential to improve the way students learn to perform scientific interpretations and understand science concepts. We developed active, collaborative activities to teach skills in manipulating flow cytometry data using FlowJo software. Undergraduate students were given compensated clinical flow cytometry listmode output (FCS) files and asked to design a gating strategy to diagnose patients with different hematological malignancies on the basis of their immunophenotype. A separate cohort of research trainees was given uncompensated data files on which they performed their own compensation, calculated the antibody staining index, designed a sequential gating strategy, and quantified rare immune cell subsets. Student engagement, confidence, and perceptions of flow cytometry were assessed using a survey. Competency against the learning outcomes was assessed by asking students to undertake tasks that required understanding of flow cytometry dot plot data and gating sequences. The active, collaborative approach allowed students to achieve learning outcomes not previously possible with traditional teaching formats, for example, having students design their own gating strategy, without forgoing essential outcomes such as the interpretation of dot plots. In undergraduate students, favorable perceptions of flow cytometry as a field and as a potential career choice were correlated with student confidence but not the ability to perform flow cytometry data analysis. We demonstrate that this new pedagogical approach to teaching flow cytometry is beneficial for student understanding and interpretation of complex concepts. It should be considered as a useful new method for incorporating complex data analysis tasks such as flow cytometry into curricula. PMID:27068992
Is the modal approach appropriate for analysis of energy flow?
NASA Astrophysics Data System (ADS)
Pavic, Goran
2002-11-01
Modal superposition is a most commonly used approach in a numerical analysis of vibration. However, the computation requirements of a typical analysis of energy flow limit the attractiveness of the modal approach because, as a rule, a very large number of modes have to be taken into account in order to produce realistic results. The reason for this particularity is that the energy analysis involves not only vibration displacements but also higher derivatives of these which are contributed by higher modes, the higher the derivative order. More careful analysis of structure-borne vibration shows that the modal truncation is not the only inconvenience where the modal approach is used. An equally important factor limiting its use is the representation of vibration dissipation by modal damping. The paper shows comparisons of computed energy flow in plates using modal and wave approaches. The differences between the two are noticeable, in particular where the vectorial functions of energy flow field, divergence and curl, are concerned. The wave approach to vibration analysis is shown to be more physically consistent than the modal approach.
Partial Averaged Navier-Stokes approach for cavitating flow
NASA Astrophysics Data System (ADS)
Zhang, L.; Zhang, Y. N.
2015-01-01
Partial Averaged Navier Stokes (PANS) is a numerical approach developed for studying practical engineering problems (e.g. cavitating flow inside hydroturbines) with a resonance cost and accuracy. One of the advantages of PANS is that it is suitable for any filter width, leading a bridging method from traditional Reynolds Averaged Navier-Stokes (RANS) to direct numerical simulations by choosing appropriate parameters. Comparing with RANS, the PANS model will inherit many physical nature from parent RANS but further resolve more scales of motion in great details, leading to PANS superior to RANS. As an important step for PANS approach, one need to identify appropriate physical filter-width control parameters e.g. ratios of unresolved-to-total kinetic energy and dissipation. In present paper, recent studies of cavitating flow based on PANS approach are introduced with a focus on the influences of filter-width control parameters on the simulation results.
A Galerkin least squares approach to viscoelastic flow.
Rao, Rekha R.; Schunk, Peter Randall
2015-10-01
A Galerkin/least-squares stabilization technique is applied to a discrete Elastic Viscous Stress Splitting formulation of for viscoelastic flow. From this, a possible viscoelastic stabilization method is proposed. This method is tested with the flow of an Oldroyd-B fluid past a rigid cylinder, where it is found to produce inaccurate drag coefficients. Furthermore, it fails for relatively low Weissenberg number indicating it is not suited for use as a general algorithm. In addition, a decoupled approach is used as a way separating the constitutive equation from the rest of the system. A Pressure Poisson equation is used when the velocity and pressure are sought to be decoupled, but this fails to produce a solution when inflow/outflow boundaries are considered. However, a coupled pressure-velocity equation with a decoupled constitutive equation is successful for the flow past a rigid cylinder and seems to be suitable as a general-use algorithm.
A Shallow Layer Approach for Geo-flow emplacement
NASA Astrophysics Data System (ADS)
Costa, A.; Folch, A.; Mecedonio, G.
2009-04-01
Geophysical flows such as lahars or lava flows severely threat the communities located on or near the volcano flanks. Risks and damages caused by the propagation of this kind of flows require a quantitative description of this phenomenon and reliable tools for forecasting their emplacement. Computational models are a valuable tool for planning risk mitigation countermeasures, such as human intervention to force flow diversion, artificial barriers, and allow for significant economical and social benefits. A FORTRAN 90 code based on a Shallow Layer Approach for Geo-flows (SLAG) for describing transport and emplacement of diluted lahars, water and lava was developed in both serial and parallel version. Three rheological models, such as those describing i) a viscous, ii) a turbulent, and iii) a dilatant flow respectively, were implemented in order to describe transport of lavas, water and diluted lahars. The code was made user-friendly by creating some interfaces that allow the user to easily define the problem, extract and interpolate the topography of the simulation domain. Moreover SLAG outputs can be written in both GRD format (e.g., Surfer), NetCDF format, or visualized directly in GoogleEarth. In SLAG the governing equations were treated using a Godunov splitting method following George (2008) algorithm based on a Riemann solver for the shallow water equations that decomposes an augmented state variable the depth, momentum, momentum flux, and bathymetry into four propagating discontinuities or waves. For our application, the algorithm was generalized for solving the energy equation. For validating the code in simulating real geophysical flows, we performed few simulations the lava flow event of the the 3rd and 4th January 1992 Etna eruption, the July 2001 Etna lava flows, January 2002 Nyragongo lava flows and few test cases for simulating transport of diluted lahars. Ref: George, D.L. (2008), Augmented Riemann Solvers for the Shallow Water Equations over Variable
A conservative approach for flow field calculations on multiple grids
NASA Technical Reports Server (NTRS)
Kathong, Monchai; Tiwari, Surendra N.
1988-01-01
In the computation of flow fields about complex configurations, it is very difficult to construct body-fitted coordinate systems. An alternative approach is to use several grids at once, each of which is generated independently. This procedure is called the multiple grids or zonal grids approach and its applications are investigated in this study. The method follows the conservative approach and provides conservation of fluxes at grid interfaces. The Euler equations are solved numerically on such grids for various configurations. The numerical scheme used is the finite-volume technique with a three-state Runge-Kutta time integration. The code is vectorized and programmed to run on the CDC VPS-32 computer. Some steady state solutions of the Euler equations are presented and discussed.
An Efficient Sparse Approach for Core Flow Problems
NASA Astrophysics Data System (ADS)
Marti, P.; Calkins, M. A.; Aurnou, J. M.; Julien, K. A.
2013-12-01
Traditionally fully spectral simulations for core flows based on Chebyshev series, Fourier series and spherical harmonics do not require the solution of very large linear systems of equations to advance in time. The explicit treatment of the Coriolis term does generally lead to a large number of decoupled equations of moderate size. It is possible in this context to work with dense matrices and dense solvers. On the other hand, an implicit treatment of the Coriolis term or certain sets of asymptotically reduced equations can not be treated in this way. The time marching of these equations requires solving few very large linear systems. Dense matrices and dense solvers become prohibitively expensive due to a very high memory footprint as well as a very slow execution time. We present a numerical approach converting theses dense systems into equivalent sparse systems that can be solved efficiently. We demonstrate our approach on a set of rapidly rotating flow problems in Cartesian, cylindrical and spherical geometry and compare it to a standard approach.
A hydrometeorological forecasting approach for basins with complex flow regime
NASA Astrophysics Data System (ADS)
Zarkadoulas, Akis; Mantesi, Konstantina; Efstratiadis, Andreas; Koussis, Antonis; Mazi, Aikaterini; Katsanos, Demetris; Koukouvinos, Antonis; Koutsoyiannis, Demetris
2015-04-01
The combined use of weather forecasting models and hydrological models in flood risk estimations is an established technique, with several successful applications worldwide. However, most known hydrometeorological forecasting systems have been established in large rivers with perpetual flow. Experience from small- and medium-scale basins, which are often affected by flash floods, is very limited. In this work we investigate the perspectives of hydrometeorological forecasting, by emphasizing two issues: (a) which modelling approach can credibly represent the complex dynamics of basins with highly variable runoff (intermittent or ephemeral); and (b) which transformation of point-precipitation forecasts provides the most reliable estimations of spatially aggregated data, to be used as inputs to semi-distributed hydrological models. Using as case studies the Sarantapotamos river basin, in Eastern Greece (145 km2), and the Nedontas river basin, in SW Peloponnese (120 km2), we demonstrate the advantages of continuous simulation through the HYDROGEIOS model. This employs conjunctive modelling of surface and groundwater flows and their interactions (percolation, infiltration, underground losses), which are key processes in river basins characterized by significantly variability of runoff. The model was calibrated against hourly flow data at two and three hydrometric stations, respectively, for a 3-year period (2011-2014). Next we attempted to reproduce the most intense flood events of that period, by substituting observed rainfall by forecast scenarios. In this respect, we used consecutive point forecasts of a 6-hour lead time, provided by the numerical weather prediction model WRF (Advanced Research version), dynamically downscaled from the ~1° forecast of GSF-NCEP/NOAA successively first to ~18 km, then to ~6 km and ultimately at the horizontal grid resolution of 2x2 km2. We examined alternative spatial integration approaches, using as reference the rainfall stations
Temporal volume flow: an approach to tracking failure recovery
NASA Astrophysics Data System (ADS)
Liu, Jianfei; Subramanian, Kalpathi R.; Yoo, Terry S.
2011-03-01
The simultaneous use of pre-segmented CT colonoscopy images and optical colonoscopy images during routine endoscopic procedures provides useful clinical information to the gastroenterologist. Blurry images in the video stream can cause the tracking system to fail during the procedure, due to the endoscope touching the colon wall or a polyp. The ability to recover from such failures is necessary to continually track images, and goes towards building a robust tracking system. Identifying similar images before and after the blurry sequence is central to this task. In this work, we propose a Temporal Volume Flow(TVF) based approach to search for a similar image pair before and after blurry sequences in the optical colonoscopy video. TVF employs nonlinear intensity and gradient constancy models, as well as a discontinuity-preserving smoothness constraint to formulate an energy function; minimizing this function between two temporal volumes before and after the blurry sequence results in an estimate of TVF. A voting approach is then used to determine an image pair with the maximum number of point correspondences. Region flow algorithm10 is applied to the selected image pair to determine camera motion parameters. We applied our algorithm to three optical colonoscopy sequences. The first sequence had 235 images in the ascending colon, and 12 blurry images. The image pair selected by TVF decreases the rotation error of the tracking results using the region flow algorithm. Similar results were observed in the second patient in the descending colon, containing 535 images and 24 blurry images. The third sequence contained 580 images in the descending colon and 172 blurry images. Region flow method failed in this case due to improper image pair selection; using TVF to determine the image pair allowed the system to successfully recover from the blurry sequence.
Approaches to the simulation of unconfined flow and perched groundwater flow in MODFLOW
Bedekar, Vivek; Niswonger, Richard G.; Kipp, Kenneth; Panday, Sorab; Tonkin, Matthew
2012-01-01
Various approaches have been proposed to manage the nonlinearities associated with the unconfined flow equation and to simulate perched groundwater conditions using the MODFLOW family of codes. The approaches comprise a variety of numerical techniques to prevent dry cells from becoming inactive and to achieve a stable solution focused on formulations of the unconfined, partially-saturated, groundwater flow equation. Keeping dry cells active avoids a discontinuous head solution which in turn improves the effectiveness of parameter estimation software that relies on continuous derivatives. Most approaches implement an upstream weighting of intercell conductance and Newton-Raphson linearization to obtain robust convergence. In this study, several published approaches were implemented in a stepwise manner into MODFLOW for comparative analysis. First, a comparative analysis of the methods is presented using synthetic examples that create convergence issues or difficulty in handling perched conditions with the more common dry-cell simulation capabilities of MODFLOW. Next, a field-scale three-dimensional simulation is presented to examine the stability and performance of the discussed approaches in larger, practical, simulation settings.
Approaches to the simulation of unconfined flow and perched groundwater flow in MODFLOW.
Bedekar, Vivek; Niswonger, Richard G; Kipp, Kenneth; Panday, Sorab; Tonkin, Matthew
2012-01-01
Various approaches have been proposed to manage the nonlinearities associated with the unconfined flow equation and to simulate perched groundwater conditions using the MODFLOW family of codes. The approaches comprise a variety of numerical techniques to prevent dry cells from becoming inactive and to achieve a stable solution focused on formulations of the unconfined, partially-saturated, groundwater flow equation. Keeping dry cells active avoids a discontinuous head solution which in turn improves the effectiveness of parameter estimation software that relies on continuous derivatives. Most approaches implement an upstream weighting of intercell conductance and Newton-Raphson linearization to obtain robust convergence. In this study, several published approaches were implemented in a stepwise manner into MODFLOW for comparative analysis. First, a comparative analysis of the methods is presented using synthetic examples that create convergence issues or difficulty in handling perched conditions with the more common dry-cell simulation capabilities of MODFLOW. Next, a field-scale three-dimensional simulation is presented to examine the stability and performance of the discussed approaches in larger, practical, simulation settings. PMID:21635246
A methodological approach of estimating resistance to flow under unsteady flow conditions
NASA Astrophysics Data System (ADS)
Mrokowska, M. M.; Rowiński, P. M.; Kalinowska, M. B.
2015-10-01
This paper presents an evaluation and analysis of resistance parameters: friction slope, friction velocity and Manning coefficient in unsteady flow. The methodology to enhance the evaluation of resistance by relations derived from flow equations is proposed. The main points of the methodology are (1) to choose a resistance relation with regard to a shape of a channel and (2) type of wave, (3) to choose an appropriate method to evaluate slope of water depth, and (4) to assess the uncertainty of result. In addition to a critical analysis of existing methods, new approaches are presented: formulae for resistance parameters for a trapezoidal channel, and a translation method instead of Jones' formula to evaluate the gradient of flow depth. Measurements obtained from artificial dam-break flood waves in a small lowland watercourse have made it possible to apply the method and to analyse to what extent resistance parameters vary in unsteady flow. The study demonstrates that results of friction slope and friction velocity are more sensitive to applying simplified formulae than the Manning coefficient (n). n is adequate as a flood routing parameter but may be misleading when information on trend of resistance with flow rate is crucial. Then friction slope or friction velocity seems to be better choice.
A new simulation approach for modeling inflated pahoehoe lava flows
NASA Astrophysics Data System (ADS)
Baloga, S. M.; Glaze, L. S.; Hamilton, C.
2013-12-01
Pahoehoe lavas are recognized as an important landform on Earth, Mars and Io. Observations of such flows on Earth indicate that when flow rates are very low and emplacement occurs on very low slopes, the process is dominated by random effects. Existing models for lobate a`a lava flows that assume viscous fluid flow on an inclined plane are not appropriate for dealing with the numerous random factors present in pahoehoe emplacement. We present a new model that incorporates a simulation approach to quantifying the influence of random and ambient factors on the evolving three-dimensional shape and morphology of pahoehoe lobes. To simulate pahoehoe lava emplacement, we consider the movement of small parcels of lava with a volume equal to the size of a typical toe (70 x 70 x 20 cm3). The model develops a set of probabilistic rules for determining the location and direction of movement for each parcel. Unlike the classical random walk of Brownian motion, many parcels may remain dormant, but fluid, for multiple time steps. The net effect of this approach is that parcels tend to accumulate preferentially within the lobe producing cross-sectional topographic profiles with a medial ridge. The randomness of parcel volume transfers within the lobe interior as well as at the margins qualitatively reflects inflation processes observed in the field. This new model predicts that greater than 75% of pahoehoe lobe volume is contributed through inflation for typical lobes. The influences on planform shape and topographic cross-sectional profiles of total volume, source area and shape, topographic confinement, and sequential breakouts at the lobe margins, have been explored with the stochastic model. The model provides a means for assessing the relative importance of these processes through comparisons with field data. A major conclusion of this work is that sequential breakouts at the lobe margins are an important process controlling the final topographic distribution of observed
Solving the power flow equations: a monotone operator approach
Dvijotham, Krishnamurthy; Low, Steven; Chertkov, Michael
2015-07-21
The AC power flow equations underlie all operational aspects of power systems. They are solved routinely in operational practice using the Newton-Raphson method and its variants. These methods work well given a good initial “guess” for the solution, which is always available in normal system operations. However, with the increase in levels of intermittent generation, the assumption of a good initial guess always being available is no longer valid. In this paper, we solve this problem using the theory of monotone operators. We show that it is possible to compute (using an offline optimization) a “monotonicity domain” in the space of voltage phasors. Given this domain, there is a simple efficient algorithm that will either find a solution in the domain, or provably certify that no solutions exist in it. We validate the approach on several IEEE test cases and demonstrate that the offline optimization can be performed tractably and the computed “monotonicity domain” includes all practically relevant power flow solutions.
A Mixed Approach for Modeling Blood Flow in Brain Microcirculation
NASA Astrophysics Data System (ADS)
Lorthois, Sylvie; Peyrounette, Myriam; Davit, Yohan; Quintard, Michel; Groupe d'Etude sur les Milieux Poreux Team
2015-11-01
Consistent with its distribution and exchange functions, the vascular system of the human brain cortex is a superposition of two components. At small-scale, a homogeneous and space-filling mesh-like capillary network. At large scale, quasi-fractal branched veins and arteries. From a modeling perspective, this is the superposition of: (a) a continuum model resulting from the homogenization of slow transport in the small-scale capillary network; and (b) a discrete network approach describing fast transport in the arteries and veins, which cannot be homogenized because of their fractal nature. This problematic is analogous to fast conducting wells embedded in a reservoir rock in petroleum engineering. An efficient method to reduce the computational cost is to use relatively large grid blocks for the continuum model. This makes it difficult to accurately couple both components. We solve this issue by adapting the ``well model'' concept used in petroleum engineering to brain specific 3D situations. We obtain a unique linear system describing the discrete network, the continuum and the well model. Results are presented for realistic arterial and venous geometries. The mixed approach is compared with full network models including various idealized capillary networks of known permeability. ERC BrainMicroFlow GA615102.
A new approach to blood flow simulation in vascular networks.
Tamaddon, Houman; Behnia, Mehrdad; Behnia, Masud; Kritharides, Leonard
2016-01-01
A proper analysis of blood flow is contingent upon accurate modelling of the branching pattern and vascular geometry of the network of interest. It is challenging to reconstruct the entire vascular network of any organ experimentally, in particular the pulmonary vasculature, because of its very high number of vessels, complexity of the branching pattern and poor accessibility in vivo. The objective of our research is to develop an innovative approach for the reconstruction of the full pulmonary vascular tree from available morphometric data. Our method consists of the use of morphometric data on those parts of the pulmonary vascular tree that are too small to reconstruct by medical imaging methods. This method is a three-step technique that reconstructs the entire pulmonary arterial tree down to the capillary bed. Vessels greater than 2 mm are reconstructed from direct volume and surface analysis using contrast-enhanced computed tomography. Vessels smaller than 2 mm are reconstructed from available morphometric and distensibility data and rearranged by applying Murray's laws. Implementation of morphometric data to reconstruct the branching pattern and applying Murray's laws to every vessel bifurcation simultaneously leads to an accurate vascular tree reconstruction. The reconstruction algorithm generates full arterial tree topography down to the ﬁrst capillary bifurcation. Geometry of each order of the vascular tree is generated separately to minimize the construction and simulation time. The node-to-node connectivity along with the diameter and length of every vessel segment is established and order numbers, according to the diameter-deﬁned Strahler system, are assigned. In conclusion, the present model provides a morphological foundation for future analysis of blood flow in the pulmonary circulation. PMID:26195135
Augmenting the diagnostic power of flow-based approaches to functional reasoning
Chittaro, L.; Ranon, R.
1996-12-31
In this paper, we consider flow-based approaches to functional diagnosis. First, we contrast the existing approaches, pointing out the major limitations of each. Then, we choose one of them and extend it in order to overcome the identified limitations. Finally, we show how the proposed extension can be introduced into the other flow-based approaches.
Langevin equation approach to granular flow in a narrow pipe
Riethmueller, T.; Schimansky-Geier, L.; Rosenkranz, D.; Poeschel, T.
1997-01-01
The gravity-driven flow of granular material through a rough, narrow vertical pipe is described using the Langevin equation formalism. Above a critical particle density the homogeneous flow becomes unstable with respect to short-wave length perturbations. In correspondence with experimental observations, we find clogging and density waves in the flowing material.
An Active, Collaborative Approach to Learning Skills in Flow Cytometry
ERIC Educational Resources Information Center
Fuller, Kathryn; Linden, Matthew D.; Lee-Pullen, Tracey; Fragall, Clayton; Erber, Wendy N.; Röhrig, Kimberley J.
2016-01-01
Advances in science education research have the potential to improve the way students learn to perform scientific interpretations and understand science concepts. We developed active, collaborative activities to teach skills in manipulating flow cytometry data using FlowJo software. Undergraduate students were given compensated clinical flow…
Lattice kinetic approach to non-equilibrium flows
NASA Astrophysics Data System (ADS)
Montessori, A.; Prestininzi, P.; La Rocca, M.; Falcucci, G.; Succi, S.
2016-06-01
We present a Lattice Boltzmann method for the simulation of a wide range of Knudsen regimes. The method is assessed in terms of normalised discharge for flow across parallel plates and three-dimensional flows in porous media. Available analytical solutions are well reproduced, supporting the the method as an appealing candidate to bridge the gap between the hydrodynamic regime and free molecular motion.
Effects of gravity on interdendritic flow - An analytic approach
NASA Astrophysics Data System (ADS)
Simpson, M.; Flemings, M. C.
1984-11-01
The present investigation attempts to provide an aid to the understanding of the essence of the gravitational influence on interdendritic flow. An analytic solution of the equations governing interdendritic fluid flow is presented for a simple case, involving a semiinfinite mushy zone whose isotherms are flat, parallel, and inclined at an angle to the force of gravity. It is found that gravity in ingots with narrow mushy zones mainly produces interdendritic flow parallel to the liquidus confined to the vicinity of the liquidus. This flow can be large in comparison to the usual shrinkage-induced flows. Its existence is caused by the rapid increase of permeability with fraction liquid near the liquidus. For this reason, it cannot appear in numerical calculations which ignore the rapid variation of permeability.
Effects of gravity on interdendritic flow - An analytic approach
NASA Technical Reports Server (NTRS)
Simpson, M.; Flemings, M. C.
1984-01-01
The present investigation attempts to provide an aid to the understanding of the essence of the gravitational influence on interdendritic flow. An analytic solution of the equations governing interdendritic fluid flow is presented for a simple case, involving a semiinfinite mushy zone whose isotherms are flat, parallel, and inclined at an angle to the force of gravity. It is found that gravity in ingots with narrow mushy zones mainly produces interdendritic flow parallel to the liquidus confined to the vicinity of the liquidus. This flow can be large in comparison to the usual shrinkage-induced flows. Its existence is caused by the rapid increase of permeability with fraction liquid near the liquidus. For this reason, it cannot appear in numerical calculations which ignore the rapid variation of permeability.
Limiting flows of a viscous fluid with stationary separation zones with Re approaching infinity
NASA Technical Reports Server (NTRS)
Taganov, G. I.
1982-01-01
The limiting flows of a viscous noncondensable fluid, which are approached by flows with stationary separation zones behind planar symmetrical bodies, with an unlimited increase in the Reynolds number are studied. Quantitative results are obtained in the case of a circulation flow inside of a separation zone.
A Riparian Approach to Dendrochronological Flow Reconstruction, Yellowstone River, Montana
NASA Astrophysics Data System (ADS)
Schook, D. M.; Rathburn, S. L.; Friedman, J. M.
2015-12-01
Tree ring-based flow reconstructions can reveal river discharge variability over durations far exceeding the gauged record, building perspective for both the measured record and future flows. We use plains cottonwood (Populus deltoides subsp. monilifera) tree rings collected from four rivers to reconstruct flow history of the Yellowstone River near its confluence with the Missouri River. Upland trees in dry regions are typically used in flow reconstruction because their annual growth is controlled by the same precipitation that drives downstream flow, but our study improves flow reconstruction by including floodplain trees that are directly affected by the river. Cores from over 1000 cottonwoods along the Yellowstone, Powder, Little Missouri, and Redwater Rivers were collected from within a 170 km radius to reconstruct flows using the Age Curve Standardization technique in a multiple regression analysis. The large sample from trees spanning many age classes allows us to use only the rings that were produced when each tree was less than 50 years old and growth was most strongly correlated to river discharge. Using trees from a range of rivers improves our ability to differentiate between growth resulting from local precipitation and river flow, and we show that cottonwood growth differs across these neighboring rivers having different watersheds. Using the program Seascorr, tree growth is found to better correlated to seasonal river discharge (R = 0.69) than to local precipitation (R = 0.45). Our flow reconstruction reveals that the most extreme multi-year or multi-decade drought periods of the last 250 years on either the Yellowstone (1817-1821) or Powder (1846-1865) Rivers are missed by the gauged discharge record. Across all sites, we document increased growth in the 20th century compared to the 19th, a finding unattainable with conventional methods but having important implications for flow management.
Three Dimensional Alveolar Flow Phenomena Using a CFD Approach
NASA Astrophysics Data System (ADS)
Sznitman, Josue
2005-11-01
Respiratory flows in the lung periphery are characterized by low Reynolds numbers (typically Re<1) in sub-millimeter airways marked by the presence of alveoli (gas exchange units). We present for realistic breathing conditions using CFD simulations (CFX-5.7.1), 3D velocity fields and flow patterns induced by the expansion/contraction of alveoli and acinar ducts during oscillatory flow. Based on anatomical data, the alveolus and airway are modeled as a spherical cap connected to a cylindrical duct, both subject to moving wall boundary conditions simulating respiration. The resulting 3D flow patterns are complex and governed by the ratio of the alveolar to ductal flow rates. This ratio describes the interplay between alveolar recirculation, induced by the ductal shear flow over the alveolus opening, and alveolar radial flow, induced by the expansion/contraction motion. Our 3D results are in good agreement with 2D simulations reported in the literature. Although convection mechanisms may transport gas along acinar ducts and deeper into the acinus, velocity fields within alveoli predict that upon gas entering them, transport is then solely dominated by diffusion mechanisms.
Numerical and Experimental Approaches Toward Understanding Lava Flow Heat Transfer
NASA Astrophysics Data System (ADS)
Rumpf, M.; Fagents, S. A.; Hamilton, C.; Crawford, I. A.
2013-12-01
We have performed numerical modeling and experimental studies to quantify the heat transfer from a lava flow into an underlying particulate substrate. This project was initially motivated by a desire to understand the transfer of heat from a lava flow into the lunar regolith. Ancient regolith deposits that have been protected by a lava flow may contain ancient solar wind, solar flare, and galactic cosmic ray products that can give insight into the history of our solar system, provided the records were not heated and destroyed by the overlying lava flow. In addition, lava-substrate interaction is an important aspect of lava fluid dynamics that requires consideration in lava emplacement models Our numerical model determines the depth to which the heat pulse will penetrate beneath a lava flow into the underlying substrate. Rigorous treatment of the temperature dependence of lava and substrate thermal conductivity and specific heat capacity, density, and latent heat release are imperative to an accurate model. Experiments were conducted to verify the numerical model. Experimental containers with interior dimensions of 20 x 20 x 25 cm were constructed from 1 inch thick calcium silicate sheeting. For initial experiments, boxes were packed with lunar regolith simulant (GSC-1) to a depth of 15 cm with thermocouples embedded at regular intervals. Basalt collected at Kilauea Volcano, HI, was melted in a gas forge and poured directly onto the simulant. Initial lava temperatures ranged from ~1200 to 1300 °C. The system was allowed to cool while internal temperatures were monitored by a thermocouple array and external temperatures were monitored by a Forward Looking Infrared (FLIR) video camera. Numerical simulations of the experiments elucidate the details of lava latent heat release and constrain the temperature-dependence of the thermal conductivity of the particulate substrate. The temperature-dependence of thermal conductivity of particulate material is not well known
A novel approach to improve operation and performance in flow field-flow fractionation.
Johann, Christoph; Elsenberg, Stephan; Roesch, Ulrich; Rambaldi, Diana C; Zattoni, Andrea; Reschiglian, Pierluigi
2011-07-01
A new system design and setup are proposed for the combined use of asymmetrical flow field-flow fractionation (AF4) and hollow-fiber flow field-flow fractionation (HF5) within the same instrumentation. To this purpose, three innovations are presented: (a) a new flow control scheme where focusing flow rates are measured in real time allowing to adjust the flow rate ratio as desired; (b) a new HF5 channel design consisting of two sets of ferrule, gasket and cap nut used to mount the fiber inside a tube. This design provides a mechanism for effective and straightforward sealing of the fiber; (c) a new AF4 channel design with only two fluid connections on the upper plate. Only one pump is needed to deliver the necessary flow rates. In the focusing/relaxation step the two parts of the focusing flow and a bypass flow flushing the detectors are created with two splits of the flow from the pump. In the elution mode the cross-flow is measured and controlled with a flow controller device. This leads to reduced pressure pulsations in the channel and improves signal to noise ratio in the detectors. Experimental results of the separation of bovine serum albumin (BSA) and of a mix of four proteins demonstrate a significant improvement in the HF5 separation performance, in terms of efficiency, resolution, and run-to-run reproducibility compared to what has been reported in the literature. Separation performance in HF5 mode is shown to be comparable to the performance in AF4 mode using a channel with two connections in the upper plate. PMID:21227436
Chang, Chih-Hao . E-mail: chchang@engineering.ucsb.edu; Liou, Meng-Sing . E-mail: meng-sing.liou@grc.nasa.gov
2007-07-01
In this paper, we propose a new approach to compute compressible multifluid equations. Firstly, a single-pressure compressible multifluid model based on the stratified flow model is proposed. The stratified flow model, which defines different fluids in separated regions, is shown to be amenable to the finite volume method. We can apply the conservation law to each subregion and obtain a set of balance equations. Secondly, the AUSM{sup +} scheme, which is originally designed for the compressible gas flow, is extended to solve compressible liquid flows. By introducing additional dissipation terms into the numerical flux, the new scheme, called AUSM{sup +}-up, can be applied to both liquid and gas flows. Thirdly, the contribution to the numerical flux due to interactions between different phases is taken into account and solved by the exact Riemann solver. We will show that the proposed approach yields an accurate and robust method for computing compressible multiphase flows involving discontinuities, such as shock waves and fluid interfaces. Several one-dimensional test problems are used to demonstrate the capability of our method, including the Ransom's water faucet problem and the air-water shock tube problem. Finally, several two dimensional problems will show the capability to capture enormous details and complicated wave patterns in flows having large disparities in the fluid density and velocities, such as interactions between water shock wave and air bubble, between air shock wave and water column(s), and underwater explosion.
A new approach to highly resolved measurements of turbulent flow
NASA Astrophysics Data System (ADS)
Puczylowski, J.; Hölling, A.; Peinke, J.; Bhiladvala, R.; Hölling, M.
2015-05-01
In this paper we present the design and principle of a new anemometer, namely the 2d-Laser Cantilever Anemometer (2d-LCA), which has been developed for highly resolved flow speed measurements of two components (2d) under laboratory conditions. We will explain the working principle and demonstrate the sensor’s performance by means of comparison measurements of wake turbulence with a commercial X-wire. In the past we have shown that the 2d-LCA is capable of being applied in liquid and particle-laden domains, but we also believe that other challenging areas of operation such as near-wall flows can become accessible.
A General Approach to Time Periodic Incompressible Viscous Fluid Flow Problems
NASA Astrophysics Data System (ADS)
Geissert, Matthias; Hieber, Matthias; Nguyen, Thieu Huy
2016-06-01
This article develops a general approach to time periodic incompressible fluid flow problems and semilinear evolution equations. It yields, on the one hand, a unified approach to various classical problems in incompressible fluid flow and, on the other hand, gives new results for periodic solutions to the Navier-Stokes-Oseen flow, the Navier-Stokes flow past rotating obstacles, and, in the geophysical setting, for Ornstein-Uhlenbeck and various diffusion equations with rough coefficients. The method is based on a combination of interpolation and topological arguments, as well as on the smoothing properties of the linearized equation.
Rheological flow laws for multiphase magmas: An empirical approach
NASA Astrophysics Data System (ADS)
Pistone, Mattia; Cordonnier, Benoît; Ulmer, Peter; Caricchi, Luca
2016-07-01
The physical properties of magmas play a fundamental role in controlling the eruptive dynamics of volcanoes. Magmas are multiphase mixtures of crystals and gas bubbles suspended in a silicate melt and, to date, no flow laws describe their rheological behaviour. In this study we present a set of equations quantifying the flow of high-viscosity (> 105 Pa·s) silica-rich multiphase magmas, containing both crystals (24-65 vol.%) and gas bubbles (9-12 vol.%). Flow laws were obtained using deformation experiments performed at high temperature (673-1023 K) and pressure (200-250 MPa) over a range of strain-rates (5 · 10- 6 s- 1 to 4 · 10- 3 s- 1), conditions that are relevant for volcanic conduit processes of silica-rich systems ranging from crystal-rich lava domes to crystal-poor obsidian flows. We propose flow laws in which stress exponent, activation energy, and pre-exponential factor depend on a parameter that includes the volume fraction of weak phases (i.e. melt and gas bubbles) present in the magma. The bubble volume fraction has opposing effects depending on the relative crystal volume fraction: at low crystallinity bubble deformation generates gas connectivity and permeability pathways, whereas at high crystallinity bubbles do not connect and act as "lubricant" objects during strain localisation within shear bands. We show that such difference in the evolution of texture is mainly controlled by the strain-rate (i.e. the local stress within shear bands) at which the experiments are performed, and affect the empirical parameters used for the flow laws. At low crystallinity (< 44 vol.%) we observe an increase of viscosity with increasing strain-rate, while at high crystallinity (> 44 vol.%) the viscosity decreases with increasing strain-rate. Because these behaviours are also associated with modifications of sample textures during the experiment and, thus, are not purely the result of different deformation rates, we refer to "apparent shear-thickening" and
A Cartesian grid approach with hierarchical refinement for compressible flows
NASA Technical Reports Server (NTRS)
Quirk, James J.
1994-01-01
Many numerical studies of flows that involve complex geometries are limited by the difficulties in generating suitable grids. We present a Cartesian boundary scheme for two-dimensional, compressible flows that is unfettered by the need to generate a computational grid and so it may be used, routinely, even for the most awkward of geometries. In essence, an arbitrary-shaped body is allowed to blank out some region of a background Cartesian mesh and the resultant cut-cells are singled out for special treatment. This is done within a finite-volume framework and so, in principle, any explicit flux-based integration scheme can take advantage of this method for enforcing solid boundary conditions. For best effect, the present Cartesian boundary scheme has been combined with a sophisticated, local mesh refinement scheme, and a number of examples are shown in order to demonstrate the efficacy of the combined algorithm for simulations of shock interaction phenomena.
Hydrodynamical Approach to Vehicular Flow in the Urban Street Canyon
NASA Astrophysics Data System (ADS)
Duras, Maciej M.
2001-06-01
The vehicular flow in the urban street canyon is considered. The classical field description is used in the modelling of the vehicular movement and of gaseous mixture in generic urban street canyon. The dynamical variables include vehicular densities, velocities, and emissivities: of pollutants, heat and exhaust gases, as well as standard mixture components' variables: densities, velocities, temperature, pressures. The local balances' equations predict the dynamics of the complex system. The automatic control of the vehicular flow is attained by the sets of coordinated traffic lights. The automatic control is aimed at minimization of traffic ecological costs by the application of variational calculus (Lagrange's and Bolz's problems). The theoretical description is accompanied by numerical examples of computer fluid dynamics based on real traffic data.
Adjoint operator approach to shape design for internal incompressible flows
NASA Technical Reports Server (NTRS)
Cabuk, H.; Sung, C.-H.; Modi, V.
1991-01-01
The problem of determining the profile of a channel or duct that provides the maximum static pressure rise is solved. Incompressible, laminar flow governed by the steady state Navier-Stokes equations is assumed. Recent advances in computational resources and algorithms have made it possible to solve the direct problem of determining such a flow through a body of known geometry. It is possible to obtain a set of adjoint equations, the solution to which permits the calculation of the direction and relative magnitude of change in the diffuser profile that leads to a higher pressure rise. The solution to the adjoint problem can be shown to represent an artificially constructed flow. This interpretation provides a means to construct numerical solutions to the adjoint equations that do not compromise the fully viscous nature of the problem. The algorithmic and computational aspects of solving the adjoint equations are addressed. The form of these set of equations is similar but not identical to the Navier-Stokes equations. In particular some issues related to boundary conditions and stability are discussed.
Triangular flow in relativstic heavy ion collisions in an event-by-event hybrid approach
NASA Astrophysics Data System (ADS)
Petersen, Hannah; La Placa, Rolando; Bass, Steffen A.
2012-09-01
Triangular flow has been shown to be an interesting new observable to gain insights about the properties of hot and dense strongly interacting matter as it is produced in heavy ion collisions at RHIC and LHC. The potential of triangular flow for constraining the initial state granularity is explored by performing an explicit calculation of the triangularity and the final state anisotropic flow for initial states that exhibit different amounts of fluctuations. We present triangular flow results for Au+Au collisions at the highest RHIC energy calculated in a hybrid approach that includes a non-equilibrium initial evolution and an ideal hydrodynamic expansion with a hadronic afterburner in 3+1 dimensions. Triangular flow results for Pb+Pb collisions at LHC energies employing the same parameters that work at RHIC are compared to ALICE data. In addition, by comparing the hybrid approach calculation with a pure transport approach, the influence of viscosity is studied.
NASA Astrophysics Data System (ADS)
Wu, Fu-Chun; Chang, Ching-Fu; Shiau, Jenq-Tzong
2015-05-01
The full range of natural flow regime is essential for sustaining the riverine ecosystems and biodiversity, yet there are still limited tools available for assessment of flow regime alterations over a spectrum of temporal scales. Wavelet analysis has proven useful for detecting hydrologic alterations at multiple scales via the wavelet power spectrum (WPS) series. The existing approach based on the global WPS (GWPS) ratio tends to be dominated by the rare high-power flows so that alterations of the more frequent low-power flows are often underrepresented. We devise a new approach based on individual deviations between WPS (DWPS) that are root-mean-squared to yield the global DWPS (GDWPS). We test these two approaches on the three reaches of the Feitsui Reservoir system (Taiwan) that are subjected to different classes of anthropogenic interventions. The GDWPS reveal unique features that are not detected with the GWPS ratios. We also segregate the effects of individual subflow components on the overall flow regime alterations using the subflow GDWPS. The results show that the daily hydropeaking waves below the reservoir not only intensified the flow oscillations at daily scale but most significantly eliminated subweekly flow variability. Alterations of flow regime were most severe below the diversion weir, where the residual hydropeaking resulted in a maximum impact at daily scale while the postdiversion null flows led to large hydrologic alterations over submonthly scales. The smallest impacts below the confluence reveal that the hydrologic alterations at scales longer than 2 days were substantially mitigated with the joining of the unregulated tributary flows, whereas the daily-scale hydrologic alteration was retained because of the hydropeaking inherited from the reservoir releases. The proposed DWPS approach unravels for the first time the details of flow regime alterations at these intermediate scales that are overridden by the low-frequency high-power flows when
Field theoretical approach for bio-membrane coupled with flow field
NASA Astrophysics Data System (ADS)
Oya, Y.; Kawakatsu, T.
2013-02-01
Shape deformation of bio-membranes in flow field is well known phenomenon in biological systems, for example red blood cell in blood vessel. To simulate such deformation with use of field theoretical approach, we derived the dynamical equation of phase field for shape of membrane and coupled the equation with Navier-Stokes equation for flow field. In 2-dimensional simulations, we found that a bio-membrane in a Poiseuille flow takes a parachute shape similar to the red blood cells.
A new perturbation approach to the laminar fluid flow behind a two-dimensional solid body
NASA Astrophysics Data System (ADS)
Kida, T.
1984-10-01
Asymptotic solutions of the Navier-Stokes equations for the flow field in an incompressible laminar flow around an obstacle are obtained purely from integral representations and by means of matched asymptotic expansions. In the present approach, the principle of rapid decay is automatically satisfied. The approach has the advantage that the asymptotic solutions are obtained without using the integral theorem. It is shown that the Imai's approach is essentially the same as Chang's, and that these earlier approaches do not miss functions in an analysis.
Numerical simulation of polymer flows: A parallel computing approach
Aggarwal, R.; Keunings, R.; Roux, F.X.
1993-12-31
We present a parallel algorithm for the numerical simulation of viscoelastic fluids on distributed memory computers. The algorithm has been implemented within a general-purpose commercial finite element package used in polymer processing applications. Results obtained on the Intel iPSC/860 computer demonstrate high parallel efficiency in complex flow problems. However, since the computational load is unknown a priori, load balancing is a challenging issue. We have developed an adaptive allocation strategy which dynamically reallocates the work load to the processors based upon the history of the computational procedure. We compare the results obtained with the adaptive and static scheduling schemes.
Wang, W.; Rutqvist, J.; Gorke, U.-J.; Birkholzer, J.T.; Kolditz, O.
2010-03-15
The present work compares the performance of two alternative flow models for the simulation of thermal-hydraulic coupled processes in low permeable porous media: non-isothermal Richards and two-phase flow concepts. Both models take vaporization processes into account: however, the Richards model neglects dynamic pressure variations and bulk flow of the gaseous phase. For the comparison of the two approaches first published data from a laboratory experiment is studied involving thermally driven moisture flow in a partially saturated bentonite sample. Then a benchmark test of longer-term thermal-hydraulic behavior in the engineered barrier system of a geological nuclear waste repository is analyzed (DECOVALEX project). It was found that both models can be used to reproduce the vaporization process if the intrinsic permeability is relative high. However, when a thermal-hydraulic coupled problem has the same low intrinsic permeability for both the liquid and the gas phase, only the two-phase flow approach provides reasonable results.
Soares, Joao S.; Gao, Chao; Alemu, Yared; Slepian, Marvin; Bluestein, Danny
2013-01-01
Stresses on blood cellular constituents induced by blood flow can be represented by a continuum approach down to the μm level; however, the molecular mechanisms of thrombosis and platelet activation and aggregation are on the order of nm. The coupling of the disparate length and time scales between molecular and macroscopic transport phenomena represent a major computational challenge. In order to bridge the gap between macroscopic flow scales and the cellular scales with the goal of depicting and predicting flow induced thrombogenicity, multi-scale approaches based on particle methods are better suited. We present a top-scale model to describe bulk flow of platelet suspensions: we employ dissipative particle dynamics to model viscous flow dynamics and present a novel and general no-slip boundary condition that allows the description of three-dimensional viscous flows through complex geometries. Dissipative phenomena associated with boundary layers and recirculation zones are observed and favorably compared to benchmark viscous flow solutions (Poiseuille and Couette flows). Platelets in suspension, modeled as coarse-grained finite-sized ensembles of bound particles constituting an enclosed deformable membrane with flat ellipsoid shape, show self-orbiting motions in shear flows consistent with Jeffery's orbits, and are transported with the flow, flipping and colliding with the walls and interacting with other platelets. PMID:23695489
A kinetic-theory approach to turbulent chemically reacting flows
NASA Technical Reports Server (NTRS)
Chung, P. M.
1976-01-01
The paper examines the mathematical and physical foundations for the kinetic theory of reactive turbulent flows, discussing the differences and relation between the kinetic and averaged equations, and comparing some solutions of the kinetic equations obtained by the Green's function method with those obtained by the approximate bimodal method. The kinetic method described consists essentially in constructing the probability density functions of the chemical species on the basis of solutions of the Langevin stochastic equation for the influence of eddies on the behavior of fluid elements. When the kinetic equations are solved for the structure of the diffusion flame established in a shear layer by the bimodal method, discontinuities in gradients of the mean concentrations at the two flame edges appear. This is a consequence of the bimodal approximation of all distribution functions by two dissimilar half-Maxwellian functions, which is a very crude approximation. These discontinuities do not appear when the solutions are constructed by the Green's function method described here.
A numerical approach for groundwater flow in unsaturated porous media
NASA Astrophysics Data System (ADS)
Quintana, F.; Guarracino, L.; Saliba, R.
2006-07-01
In this article, a computational tool to simulate groundwater flow in variably saturated non-deformable fractured porous media is presented, which includes a conceptual model to obtain analytical expressions of water retention and hydraulic conductivity curves for fractured hard rocks and a numerical algorithm to solve the Richards equation. To calculate effective saturation and relative hydraulic conductivity curves we adopt the Brooks-Corey model assuming fractal laws for both aperture and number of fractures. A standard Galerkin formulation was employed to solve the Richards' equation together with a Crank-Nicholson scheme with Richardson extrapolation for the time discretization.The main contribution of this paper is to group an analytical model of the authors with a robust numerical algorithm designed to solve adequately the highly non-linear Richards' equation generating a tool for porous media engineering.
Neural network approach to classification of traffic flow states
Yang, H.; Qiao, F.
1998-11-01
The classification of traffic flow states in China has traditionally been based on the Highway Capacity Manual, published in the United States. Because traffic conditions are generally different from country to country, though, it is important to develop a practical and useful classification method applicable to Chinese highway traffic. In view of the difficulty and complexity of a mathematical and physical realization, modern pattern recognition methods are considered practical in fulfilling this goal. This study applies a self-organizing neural network pattern recognition method to classify highway traffic states into some distinctive cluster centers. A small scale test with actual data is conducted, and the method is found to be potentially applicable in practice.
Visual guidance based on optic flow: a biorobotic approach.
Franceschini, Nicolas
2004-01-01
This paper addresses some basic questions as to how vision links up with action and serves to guide locomotion in both biological and artificial creatures. The thorough knowledge gained during the past five decades on insects' sensory-motor abilities and the neuronal substrates involved has provided us with a rich source of inspiration for designing tomorrow's self-guided vehicles and micro-vehicles, which will be able to cope with unforeseen events on the ground, under water, in the air, in space, on other planets, and inside the human body. Insects can teach us some useful tricks for designing agile autonomous robots. Since constructing a "biorobot" first requires exactly formulating the biological principles presumably involved, it gives us a unique opportunity of checking the soundness and robustness of these principles by bringing them face to face with the real physical world. "Biorobotics" therefore goes one step beyond computer simulation. It leads to experimenting with real physical robots which have to pass the stringent test of the real world. Biorobotics provide us with a new tool, which can help neurobiologists and neuroethologists to identify and investigate worthwhile issues in the field of sensory-motor control. Here we describe some of the visually guided terrestrial and aerial robots we have developed since 1985 on the basis of our biological findings. All these robots behave in response to the optic flow, i.e., they work by measuring the slip speed of the retinal image. Optic flow is sensed on-board by miniature electro-optical velocity sensors. The very principle of these sensors was based on studies in which we recorded the responses of single identified neurons to single photoreceptor stimulation in a model visual system: the fly's compound eye. PMID:15477039
Flow Solution for Advanced Separate Flow Nozzles Response A: Structured Grid Navier-Stokes Approach
NASA Technical Reports Server (NTRS)
Kenzakowski, D. C.; Shipman, J.; Dash, S. M.; Saiyed, Naseem (Technical Monitor)
2001-01-01
NASA Glenn Research Center funded a computational study to investigate the effect of chevrons and tabs on the exhaust plume from separate flow nozzles. Numerical studies were conducted at typical takeoff power with 0.28 M flight speed. Report provides numerical data and insights into the mechanisms responsible for increased mixing.
Spatial dynamics of ecosystem service flows: a comprehensive approach to quantifying actual services
Bagstad, Kenneth J.; Johnson, Gary W.; Voigt, Brian; Villa, Ferdinando
2013-01-01
Recent ecosystem services research has highlighted the importance of spatial connectivity between ecosystems and their beneficiaries. Despite this need, a systematic approach to ecosystem service flow quantification has not yet emerged. In this article, we present such an approach, which we formalize as a class of agent-based models termed “Service Path Attribution Networks” (SPANs). These models, developed as part of the Artificial Intelligence for Ecosystem Services (ARIES) project, expand on ecosystem services classification terminology introduced by other authors. Conceptual elements needed to support flow modeling include a service's rivalness, its flow routing type (e.g., through hydrologic or transportation networks, lines of sight, or other approaches), and whether the benefit is supplied by an ecosystem's provision of a beneficial flow to people or by absorption of a detrimental flow before it reaches them. We describe our implementation of the SPAN framework for five ecosystem services and discuss how to generalize the approach to additional services. SPAN model outputs include maps of ecosystem service provision, use, depletion, and flows under theoretical, possible, actual, inaccessible, and blocked conditions. We highlight how these different ecosystem service flow maps could be used to support various types of decision making for conservation and resource management planning.
The objective of this research is to develop and demonstrate a general approach for modeling flow and transport in the heterogeneous vadose zone. The approach uses similar media scaling, geostatistics, and conditional simulation methods to estimate soil hydraulic parameters at un...
The objective of this research is to develop and demonstrate a general approach for modeling flow and transport in the heterogeneous vadose zone. The approach uses similar media scaling, geostatistics, and conditional simulation methods to estimate soil hydraulic parameters at un...
A SPATIOTEMPORAL APPROACH FOR HIGH RESOLUTION TRAFFIC FLOW IMPUTATION
Han, Lee; Chin, Shih-Miao; Hwang, Ho-Ling
2016-01-01
Along with the rapid development of Intelligent Transportation Systems (ITS), traffic data collection technologies have been evolving dramatically. The emergence of innovative data collection technologies such as Remote Traffic Microwave Sensor (RTMS), Bluetooth sensor, GPS-based Floating Car method, automated license plate recognition (ALPR) (1), etc., creates an explosion of traffic data, which brings transportation engineering into the new era of Big Data. However, despite the advance of technologies, the missing data issue is still inevitable and has posed great challenges for research such as traffic forecasting, real-time incident detection and management, dynamic route guidance, and massive evacuation optimization, because the degree of success of these endeavors depends on the timely availability of relatively complete and reasonably accurate traffic data. A thorough literature review suggests most current imputation models, if not all, focus largely on the temporal nature of the traffic data and fail to consider the fact that traffic stream characteristics at a certain location are closely related to those at neighboring locations and utilize these correlations for data imputation. To this end, this paper presents a Kriging based spatiotemporal data imputation approach that is able to fully utilize the spatiotemporal information underlying in traffic data. Imputation performance of the proposed approach was tested using simulated scenarios and achieved stable imputation accuracy. Moreover, the proposed Kriging imputation model is more flexible compared to current models.
A flow cytometric approach to assess phytoplankton respiration.
Grégori, Gérald; Denis, Michel; Lefèvre, Dominique; Beker, Beatriz
2002-01-01
Microbial respiration in the ocean is considered as the major process representative of the organic matter biological oxidation. The corresponding metabolic CO2 production was estimated to be about 22 Pg C y(-1). However, the in situ respiration rate is generally too low (by several orders of magnitude) to be accessible to the available direct measurement methods. Some fluorescent probes, such as DiOC6(3) (Molecular Probes, USA) have been shown to be very sensitive to changes in the proton electrochemical potential difference (DeltamuH+), characterising mitochondrial and plasmic membranes bearing the cell respiratory system in eukaryotic and prokaryotic cells respectively. In mitochondria, DeltamuH+ is linked to the flux of oxygen uptake by a linear relationship. To our knowledge, no such relationship has been established in the case of whole marine cells. In the present work, we addressed the dark respiration rate of the Chlorophyceae Dunaliella tertiolecta (Butcher) in axenic cultures, both directly by using a highly sensitive oxygraph (Oroboros) and by staining cells with DiOC6(3). We found and standardized a linear relationship between oxygen uptake by D. tertiolecta and its green fluorescence induced by DiOC6(3), enabling the determination by flow cytometry of the respiration rate of D. tertiolecta. PMID:12815298
A fractal approach to low velocity non-Darcy flow in a low permeability porous medium
NASA Astrophysics Data System (ADS)
Cai, Jian-Chao
2014-04-01
In this paper, the mechanism for fluid flow at low velocity in a porous medium is analyzed based on plastic flow of oil in a reservoir and the fractal approach. The analytical expressions for flow rate and velocity of non-Newtonian fluid flow in the low permeability porous medium are derived, and the threshold pressure gradient (TPG) is also obtained. It is notable that the TPG (J) and permeability (K) of the porous medium analytically exhibit the scaling behavior J ~ K-DT/(1=DT), where DT is the fractal dimension for tortuous capillaries. The fractal characteristics of tortuosity for capillaries should be considered in analysis of non-Darcy flow in a low permeability porous medium. The model predictions of TPG show good agreement with those obtained by the available expression and experimental data. The proposed model may be conducible to a better understanding of the mechanism for nonlinear flow in the low permeability porous medium.
NASA Astrophysics Data System (ADS)
Shiau, Jenq-Tzong; Wu, Fu-Chun
2010-08-01
Environmental flow schemes may be implemented through active or restrictive strategies. The former may be applied via reservoir releases, and the latter can be executed by reducing water demands. We present a dual active-restrictive approach to devising the optimal reservoir operation rules that aim to secure off-stream water supplies while maximizing environmental benefits. For the active part, a multicomponent environmental flow target (including the minimum and monthly flows) is incorporated in the operation rules. For the restrictive counterpart, we use a novel demands partitioning and prioritizing (DPP) approach to reallocating the demands of various sectors. The DPP approach partitions the existing off-stream demand and newly incorporated environmental demand and reassembles the two as the first- and second-priority demands. Water is reallocated to each demand according to the ratios derived from the prioritized demands. The proposed approach is coupled with a multicriteria optimization framework to seek the optimal operation rules for the existing Feitsui Reservoir system (Taiwan) under various scenarios. The best overall performance is achieved by an optimal dual strategy whose operational parameters are all determined by optimization. The optimal environmental flow target may well be a top-priority constant base flow rather than the variable quantities. The active strategy would outperform the restrictive one. For the former, a top-priority base flow target is essential; for the latter, the off-stream demand can become vanishingly small in compensation for the eliminated base flow target, thus promoting the monthly flow target as nearly the top-priority demand. For either the active or restrictive strategy, a prioritized environmental flow demand would provide a path toward the optimal overall performance. A significantly improved overall performance over the existing operation rules is unlikely if the active and restrictive parameters are both favorable
NASA Astrophysics Data System (ADS)
Stancanelli, L. M.; Foti, E.
2015-04-01
A detailed comparison between the performances of two different approaches to debris flow modelling was carried out. In particular, the results of a mono-phase Bingham model (FLO-2D) and that of a two-phase model (TRENT-2D) obtained from a blind test were compared. As a benchmark test the catastrophic event of 1 October 2009 which struck Sicily causing several fatalities and damage was chosen. The predicted temporal evolution of several parameters of the debris flow (such as flow depth and propagation velocity) was analysed in order to investigate the advantages and disadvantages of the two models in reproducing the global dynamics of the event. An analysis between the models' results with survey data have been carried out, not only for the determination of statistical indicators of prediction accuracy, but also for the application of the Receiver Operator Characteristic (ROC) approach. Provided that the proper rheological parameters and boundary conditions are assigned, both models seem capable of reproducing the inundation areas in a reasonably accurate way. However, the main differences in the application rely on the choice of such rheological parameters. Indeed, within the more user-friendly FLO-2D model the tuning of the parameters must be done empirically, with no evidence of the physics of the phenomena. On the other hand, for the TRENT-2D the parameters are physically based and can be estimated from the properties of the solid material, thus reproducing more reliable results. A second important difference between the two models is that in the first method the debris flow is treated as a homogeneous flow, in which the total mass is kept constant from its initiation in the upper part of the basin to the deposition in a debris fan. In contrast, the second approach is suited to reproduce the erosion and deposition processes and the displaced mass can be directly related to the rainfall event. Application of both models in a highly urbanized area reveals the
Modeling flow and transport in unsaturated fractured rock: An evaluation of the continuum approach
Liu, H.-H.; Haukwa, C.B.; Ahlers, C.F.; Bodvarsson, G.S.; Flint, A.L.; Guertal, W.B.
2003-01-01
Because the continuum approach is relatively simple and straightforward to implement, it has been commonly used in modeling flow and transport in unsaturated fractured rock. However, the usefulness of this approach can be questioned in terms of its adequacy for representing fingering flow and transport in unsaturated fractured rock. The continuum approach thus needs to be evaluated carefully by comparing simulation results with field observations directly related to unsaturated flow and transport processes. This paper reports on such an evaluation, based on a combination of model calibration and prediction, using data from an infiltration test carried out in a densely fractured rock within the unsaturated zone of Yucca Mountain, Nevada. Comparisons between experimental and modeling results show that the continuum approach may be able to capture important features of flow and transport processes observed from the test. The modeling results also show that matrix diffusion may have a significant effect on the overall transport behavior in unsaturated fractured rocks, which can be used to estimate effective fracture-matrix interface areas based on tracer transport data. While more theoretical, numerical, and experimental studies are needed to provide a conclusive evaluation, this study suggests that the continuum approach is useful for modeling flow and transport in unsaturated, densely fractured rock. ?? 2002 Elsevier Science B.V. All rights reserved.
Modeling flow and transport in unsaturated fractured rock: an evaluation of the continuum approach.
Liu, Hui-Hai; Haukwa, Charles B; Ahlers, C Fredrik; Bodvarsson, Gudmundur S; Flint, Alan L; Guertal, William B
2003-01-01
Because the continuum approach is relatively simple and straightforward to implement, it has been commonly used in modeling flow and transport in unsaturated fractured rock. However, the usefulness of this approach can be questioned in terms of its adequacy for representing fingering flow and transport in unsaturated fractured rock. The continuum approach thus needs to be evaluated carefully by comparing simulation results with field observations directly related to unsaturated flow and transport processes. This paper reports on such an evaluation, based on a combination of model calibration and prediction, using data from an infiltration test carried out in a densely fractured rock within the unsaturated zone of Yucca Mountain, Nevada. Comparisons between experimental and modeling results show that the continuum approach may be able to capture important features of flow and transport processes observed from the test. The modeling results also show that matrix diffusion may have a significant effect on the overall transport behavior in unsaturated fractured rocks, which can be used to estimate effective fracture-matrix interface areas based on tracer transport data. While more theoretical, numerical, and experimental studies are needed to provide a conclusive evaluation, this study suggests that the continuum approach is useful for modeling flow and transport in unsaturated, densely fractured rock. PMID:12714290
Modeling flow and transport in unsaturated fractured rock: An evaluation of the continuum approach
Liu, Hui-Hai; Haukwa, Charles B.; Ahlers, C. Fredrik; Bodvarsson, Gudmundur S.; Flint, Alan L.; Guertal, William B.
2002-09-01
Because the continuum approach is relatively simple and straightforward to implement, it has been commonly used in modeling flow and transport in unsaturated fractured rock. However, the usefulness of this approach can be questioned in terms of its adequacy for representing fingering flow and transport in unsaturated fractured rock. The continuum approach thus needs to be evaluated carefully by comparing simulation results with field observations directly related to unsaturated flow and transport processes. This paper reports on such an evaluation, based on a combination of model calibration and prediction, using data from an infiltration test carried out in a densely fractured rock within the unsaturated zone of Yucca Mountain, Nevada. Comparisons between experimental and modeling results show that the continuum approach may be able to capture important features of flow and transport processes observed from the test. The modeling results also show that matrix diffusion may have a significant effect on the overall transport behavior in unsaturated fractured rocks, which can be used to estimate effective fracture-matrix interface areas based on tracer transport data. While more theoretical, numerical, and experimental studies are needed to provide a conclusive evaluation, this study suggests that the continuum approach is useful for modeling flow and transport in unsaturated, densely fractured rock.
A Mixed Approach for Modeling Blood Flow in Brain Microcirculation
NASA Astrophysics Data System (ADS)
Peyrounette, M.; Sylvie, L.; Davit, Y.; Quintard, M.
2014-12-01
We have previously demonstrated [1] that the vascular system of the healthy human brain cortex is a superposition of two structural components, each corresponding to a different spatial scale. At small-scale, the vascular network has a capillary structure, which is homogeneous and space-filling over a cut-off length. At larger scale, veins and arteries conform to a quasi-fractal branched structure. This structural duality is consistent with the functional duality of the vasculature, i.e. distribution and exchange. From a modeling perspective, this can be viewed as the superposition of: (a) a continuum model describing slow transport in the small-scale capillary network, characterized by a representative elementary volume and effective properties; and (b) a discrete network approach [2] describing fast transport in the arterial and venous network, which cannot be homogenized because of its fractal nature. This problematic is analogous to modeling problems encountered in geological media, e.g, in petroleum engineering, where fast conducting channels (wells or fractures) are embedded in a porous medium (reservoir rock). An efficient method to reduce the computational cost of fractures/continuum simulations is to use relatively large grid blocks for the continuum model. However, this also makes it difficult to accurately couple both structural components. In this work, we solve this issue by adapting the "well model" concept used in petroleum engineering [3] to brain specific 3-D situations. We obtain a unique linear system of equations describing the discrete network, the continuum and the well model coupling. Results are presented for realistic geometries and compared with a non-homogenized small-scale network model of an idealized periodic capillary network of known permeability. [1] Lorthois & Cassot, J. Theor. Biol. 262, 614-633, 2010. [2] Lorthois et al., Neuroimage 54 : 1031-1042, 2011. [3] Peaceman, SPE J. 18, 183-194, 1978.
A Hybrid URANS/LES Approach Used for Simulations of Turbulent Flows
NASA Astrophysics Data System (ADS)
Fraňa, Karel; Stiller, Jörg
A hybrid model based on the unsteady Reynolds averaged Navier-Stokes approach represented by the one-equation Spalart-Allmaras model and the Large Eddy Simulation called Detached Eddy Simulation (DES) was applied for turbulent flow simulations. This turbulent approach was implemented into the flow solver based on the Finite-Element Method with pressure stabilized and streamlines upwind Petrov-Galerkin stabilization techniques. The effectiveness and robustness of this updated solver is successfully demonstrated at benchmark calculation represented by an unsteady turbulent flow past a cylinder at Reynolds number 3900. Results such as velocity fields and the flow periodicity, Reynolds stress tensor and eddy viscosity and pressure coefficient distributions are discussed and relatively good agreement was found to direct numerical simulations and experiments.
NASA Technical Reports Server (NTRS)
Bey, K. S.; Thornton, E. A.; Dechaumphai, P.; Ramakrishnan, R.
1985-01-01
Recent progress in the development of finite element methodology for the prediction of aerothermal loads is described. Two dimensional, inviscid computations are presented, but emphasis is placed on development of an approach extendable to three dimensional viscous flows. Research progress is described for: (1) utilization of a commerically available program to construct flow solution domains and display computational results, (2) development of an explicit Taylor-Galerkin solution algorithm, (3) closed form evaluation of finite element matrices, (4) vector computer programming strategies, and (5) validation of solutions. Two test problems of interest to NASA Langley aerothermal research are studied. Comparisons of finite element solutions for Mach 6 flow with other solution methods and experimental data validate fundamental capabilities of the approach for analyzing high speed inviscid compressible flows.
A study of multiphase flow in fractured porous media using a microscale lattice Boltzmann approach
Soll, W.E.; Eggert, K.E.; Grunau, D.W.; Schafer-Perini, A.L.
1994-02-01
The lattice Boltzmann technique has been shown to be an efficient and reliable approach to modeling single- and multi-fluid flow in porous media systems. The flexibility of this approach in discretizing the pore/solid space means it is particularly well suited to capturing fluid behavior, fluid-fluid interactions, and fluid-solid interactions at the scale of the individual pores. Such flexibility readily lends itself to studying processes occurring at physical interfaces, such as between a fracture and the surrounding porous matrix. Here we present pore-level simulations of fluid flow through a fracture embedded in an unsaturated matrix. Simulations are run on the massively parallel Connection Machine 5 (CM-5) using the two-fluid, two-dimensional lattice Boltzmann flow simulator developed at Los Alamos National Laboratory. We look at the effect of pressure gradients and initial matrix saturation on infiltration into the matrix and fluid flow along the fracture.
NASA Technical Reports Server (NTRS)
Glaze, L. S.; Baloga, S. M.
2014-01-01
Pahoehoe lavas are recognized as an important landform on Earth, Mars and Io. Observations of such flows on Earth (e.g., Figure 1) indicate that the emplacement process is dominated by random effects. Existing models for lobate a`a lava flows that assume viscous fluid flow on an inclined plane are not appropriate for dealing with the numerous random factors present in pahoehoe emplacement. Thus, interpretation of emplacement conditions for pahoehoe lava flows on Mars requires fundamentally different models. A new model that implements a simulation approach has recently been developed that allows exploration of a variety of key influences on pahoehoe lobe emplacement (e.g., source shape, confinement, slope). One important factor that has an impact on the final topographic shape and morphology of a pahoehoe lobe is the volumetric flow rate of lava, where cooling of lava on the lobe surface influences the likelihood of subsequent breakouts.
Arbitrary Lagrangian-Eulerian approach in reduced order modeling of a flow with a moving boundary
NASA Astrophysics Data System (ADS)
Stankiewicz, W.; Roszak, R.; Morzyński, M.
2013-06-01
Flow-induced deflections of aircraft structures result in oscillations that might turn into such a dangerous phenomena like flutter or buffeting. In this paper the design of an aeroelastic system consisting of Reduced Order Model (ROM) of the flow with a moving boundary is presented. The model is based on Galerkin projection of governing equation onto space spanned by modes obtained from high-fidelity computations. The motion of the boundary and mesh is defined in Arbitrary Lagrangian-Eulerian (ALE) approach and results in additional convective term in Galerkin system. The developed system is demonstrated on the example of a flow around an oscillating wing.
NASA Astrophysics Data System (ADS)
De Pretto, Lucas R.; Nogueira, Gesse E. C.; Freitas, Anderson Z.
2016-04-01
Functional modalities of Optical Coherence Tomography (OCT) based on speckle analysis are emerging in the literature. We propose a simple approach to the autocorrelation of OCT signal to enable volumetric flow rate differentiation, based on decorrelation time. Our results show that this technique could distinguish flows separated by 3 μl/min, limited by the acquisition speed of the system. We further perform a B-scan of gradient flow inside a microchannel, enabling the visualization of the drag effect on the walls.
Two-Fluid Large-Eddy Simulation Approach for Two-Phase Turbulent Flows.
NASA Astrophysics Data System (ADS)
Mashayek, F.; Pandya, R. V. R.
2002-11-01
In recent years, large-eddy simulation (LES) is emerging as a predictive tool for particle/droplet-laden turbulent flows. In common practice, LES of two-phase flows involves tracking a large number of particles in a Lagrangian framework while using the Eulerian flow field generated by LES of the carrier fluid phase and proper forms for various forces acting on the particle. The two-way coupling effects (i.e. the effects of the particles on the LES flow field and subgrid scales motion and vice versa) have yet to be accounted for fully and in rigorous manner in these Eulerian-Lagrangian approaches. Recently, a new Eulerian-Eulerian approach has been proposed(R.V.R. Pandya and F. Mashayek, ``Two-fluid large-eddy simulation approach for particle-laden turbulent flows,'' to appear in Int. J. Heat and Mass Transfer.) in which Eulerian `fluid' equations are derived for the dispersed phase using the kinetic or probability density function (pdf) modeling approach after solving the closure problems arising in the filtered pdf equation. The solution to the closure accounts properly for the effects of the subgrid scales on the particles. The two-way coupling effects are modeled in a rigorous manner and included in the dynamic localization model for the subgrid stresses of the carrier phase. The `fluid' equations are supposed to capture the preferential distribution of the particles.
NASA Astrophysics Data System (ADS)
Kozaka, Orçun E.; Özkan, Gökhan; Özdemir, Bedii I.
2004-01-01
Turbulent structure of flow behind a model car is investigated with local velocity measurements with emphasis on large structures and their relevance to aerodynamic forces. Results show that two counter-rotating helical vortices, which are formed within the inner wake region, play a key role in determining the flux of kinetic energy. The turbulence is generated within the outermost shear layers due to the instabilities, which also seem to be the basic drive for these relatively organized structures. The measured terms of the turbulent kinetic energy production, which are only part of the full expression, indicate that vortex centres act similar to the manifolds draining the energy in the streamwise direction. As the approach velocity increases, the streamwise convection becomes the dominant means of turbulent transport and, thus, the acquisition of turbulence by relatively non-turbulent flow around the wake region is suppressed.
NASA Astrophysics Data System (ADS)
Chen, Li; Acharya, Kumud; Stone, Mark C.
2014-11-01
Vegetation-induced flow roughness can result in significant changes in stream hydraulics. This study revisits the well-known empirical equation for submerged flexible vegetation developed by Kouwen and collaborators, which describes the relationships between shear stress, flexural rigidity, and vegetation deflection. Theoretical analysis shows that the theories for the mechanics of large deflection cantilever beams can essentially explain this equation. The results show that for moderate to large deflection (the ratio of deflected height to original height l/L < 0.85 - 0.9) the theoretically derived relationships can be approximated with power-law equations, which have similar exponents to the Kouwen's equation and agree with its empirical relationships, which indicates the consistency of the underlying physics for the two approaches. Direct comparisons under given vegetation-height conditions also show a general agreement between the empirical and the theoretical equations. For small deflections, the theoretical results exhibit a more intuitive trend, which shows that the shear stress approaches zero at infinitesimal deflection. Additionally, theoretical analysis suggests a different non-dimensional parameter for vegetation mechanical properties and a better structure of the equation, which is expected to improve the estimation of vegetation-induced roughness. Finally, theoretical analysis indicates that even though the structure maintains, the specific relationship between vegetation bending and resistance is dependent on the flow velocity profile. Further development of these approaches need to take flow characteristics into consideration.
Multi-compartment approach to identify minimal flow and maximal recreational use of a lowland river
NASA Astrophysics Data System (ADS)
Pusch, Martin; Lorenz, Stefan
2013-04-01
Most approaches to establish a minimum flow rate for river sections subjected to water abstraction focus on flow requirements of fish and benthic invertebrates. However, artificial reduction of river flow will always affect additional key ecosystem features, as sediment properties and the metabolism of matter in these ecosystems as well, and may even influence adjacent floodplains. Thus, significant effects e.g. on the dissolved oxygen content of river water, on habitat conditions in the benthic zone, and on water levels in the floodplain are to be expected. Thus, we chose a multiple compartment method to identify minimum flow requirements in a lowland River in northern Germany (Spree River), selecting the minimal required flow level out of all compartments studied. Results showed that minimal flow levels necessary to keep key ecosystem features at a 'good' state depended significantly on actual water quality and on river channel morphology. Thereby, water quality of the Spree is potentially influenced by recreational boating activity, which causes mussels to stop filter-feeding, and thus impedes self-purification. Disturbance of mussel feeding was shown to directly depend on boat type and speed, with substantial differences among mussel species. Thus, a maximal recreational boating intensity could be derived that does not significantly affect self purification. We conclude that minimal flow levels should be identified not only based on flow preferences of target species, but also considering channel morphology, ecological functions, and the intensity of other human uses of the river section.
NASA Astrophysics Data System (ADS)
Bour, O.; Klepikova, M.; Le Borgne, T.; De Dreuzy, J.
2013-12-01
Inverse modeling of hydraulic and geometrical properties of fractured media is a very challenging objective due to the spatial heterogeneity of the medium and the scarcity of data. Here we present a flow tomography approach that permits to characterize the location, the connectivity and the hydraulic properties of main flow paths in fractured media. The accurate characterization of the location, hydraulic properties and connectivity of major fracture zones is essential to model flow and solute transport in fractured media. Cross-borehole flowmeter tests, which consist of measuring changes in vertical borehole flows when pumping a neighboring borehole, were shown to be an efficient technique to provide information on the properties of the flow zones that connect borehole pairs [Paillet, 1998; Le Borgne et al., 2006]. The interpretation of such experiments may however be quite uncertain when multiple connections exist. In this study, we explore the potential of flow tomography (i.e., sequential cross-borehole flowmeter tests) for characterizing aquifer heterogeneity. We first propose a framework for inverting flow and drawdown data to infer fracture connectivity and transmissivities. Here we use a simplified discrete fracture network approach that highlights main connectivity structures. This conceptual model attempts to reproduce fracture network connectivity without taking fracture geometry (length, orientation, dip) into account. We then explore the potential of the method for simplified synthetic fracture network models and quantify the sensitivity of drawdown and borehole flow velocities to the transmissivity of the connecting flowpaths. Flow tomography is expected to be most effective if cross-borehole pumping induces large changes in vertical borehole velocities. The uncertainty of the transmissivity estimates increases for small borehole flow velocities. The uncertainty about the transmissivity of fractures that connect the main flowpath but not the boreholes
A Vocabulary Approach to Partial Streamline Matching and Exploratory Flow Visualization.
Tao, Jun; Wang, Chaoli; Shene, Ching-Kuang; Shaw, Raymond A
2016-05-01
Measuring the similarity of integral curves is fundamental to many important flow data analysis and visualization tasks such as feature detection, pattern querying, streamline clustering, and hierarchical exploration. In this paper, we introduce FlowString, a novel vocabulary approach that extracts shape invariant features from streamlines and utilizes a string-based method for exploratory streamline analysis and visualization. Our solution first resamples streamlines by considering their local feature scales. We then classify resampled points along streamlines based on the shape similarity around their local neighborhoods. We encode each streamline into a string of well-selected shape characters, from which we construct meaningful words for querying and retrieval. A unique feature of our approach is that it captures intrinsic streamline similarity that is invariant under translation, rotation and scaling. We design an intuitive interface and user interactions to support flexible querying, allowing exact and approximate searches for partial streamline matching. Users can perform queries at either the character level or the word level, and define their own characters or words conveniently for customized search. We demonstrate the effectiveness of FlowString with several flow field data sets of different sizes and characteristics. We also extend FlowString to handle multiple data sets and perform an empirical expert evaluation to confirm the usefulness of this approach. PMID:27045908
Combined multi-fluid and drift-flux approaches for analysis of pipe flows
NASA Astrophysics Data System (ADS)
Krasnopolsky, B.; Starostin, A.; Spesivtsev, P.; Shaposhnikov, D.; Osiptsov, A.
2013-10-01
We propose an approach for generalization of 1D transient model for multiphase flows. It allows to combine an arbitrary number of phases with interaction defined by multi-fluid and drift-flux models. Commonly a fluid carries a number of components. The model is based on a graph of fluids and components, where on higher level the flow of several fluids is governed by the multi-fluid approach, while on lower level the relative motion of components within each fluid is described by drift-flux relations. The proposed model is applied to flows in oil and gas wells. The model is implemented numerically using a SIMPLE-like iterative scheme with the geometry conservation based algorithm (GCBA). The numerical realization of the algorithm for an arbitrary number of fluids and components is presented. For illustration, particular cases are considered which are relevant to wellbore flows in oil and gas applications. The introduction of drift-flux correlations into the numerical implementation is discussed. The code is validated against experimental flow patterns and stability study of stratified flows. The typical graphs for gas/liquid transport are discussed. The simulation of phase segregation in a vertical pipe demonstrates the flexibility of model.
Analyzing unsaturated flow patterns in fractured rock using an integrated modeling approach
NASA Astrophysics Data System (ADS)
Wu, Yu-Shu; Lu, Guoping; Zhang, Keni; Pan, Lehua; Bodvarsson, Gudmundur S.
2007-05-01
Characterizing percolation patterns in unsaturated fractured rock has posed a greater challenge to modeling investigations than comparable saturated zone studies due to the heterogeneous nature of unsaturated media and the great number of variables impacting unsaturated flow. An integrated modeling methodology has been developed for quantitatively characterizing percolation patterns in the unsaturated zone of Yucca Mountain, Nevada (USA), a proposed underground repository site for storing high-level radioactive waste. The approach integrates moisture, pneumatic, thermal, and isotopic geochemical field data into a comprehensive three-dimensional numerical model for analyses. It takes into account the coupled processes of fluid and heat flow and chemical isotopic transport in Yucca Mountain’s highly heterogeneous, unsaturated fractured tuffs. Modeling results are examined against different types of field-measured data and then used to evaluate different hydrogeological conceptualizations through analyzing flow patterns in the unsaturated zone. In particular, this model provides clearer understanding of percolation patterns and flow behavior through the unsaturated zone, both crucial issues in assessing repository performance. The integrated approach for quantifying Yucca Mountain’s flow system is demonstrated to provide a practical modeling tool for characterizing flow and transport processes in complex subsurface systems.
Analyzing Unsatirated Flow Patterns in Fractured Rock Using an Integrated Modeling Approach
Y.S. Wu; G. Lu; K. Zhang; L. Pan; G.S. Bodvarsson
2006-08-03
Characterizing percolation patterns in unsaturated fractured rock has posed a greater challenge to modeling investigations than comparable saturated zone studies, because of the heterogeneous nature of unsaturated media and the great number of variables impacting unsaturated flow. This paper presents an integrated modeling methodology for quantitatively characterizing percolation patterns in the unsaturated zone of Yucca Mountain, Nevada, a proposed underground repository site for storing high-level radioactive waste. The modeling approach integrates a wide variety of moisture, pneumatic, thermal, and isotopic geochemical field data into a comprehensive three-dimensional numerical model for modeling analyses. It takes into account the coupled processes of fluid and heat flow and chemical isotopic transport in Yucca Mountain's highly heterogeneous, unsaturated fractured tuffs. Modeling results are examined against different types of field-measured data and then used to evaluate different hydrogeological conceptualizations and their results of flow patterns in the unsaturated zone. In particular, this model provides a much clearer understanding of percolation patterns and flow behavior through the unsaturated zone, both crucial issues in assessing repository performance. The integrated approach for quantifying Yucca Mountain's flow system is demonstrated to provide a practical modeling tool for characterizing flow and transport processes in complex subsurface systems.
NASA Technical Reports Server (NTRS)
Sidilkover, David
1997-01-01
Some important advances took place during the last several years in the development of genuinely multidimensional upwind schemes for the compressible Euler equations. In particular, a robust, high-resolution genuinely multidimensional scheme which can be used for any of the flow regimes computations was constructed. This paper summarizes briefly these developments and outlines the fundamental advantages of this approach.
ERIC Educational Resources Information Center
Djelic, Marina; Mazic, Sanja; Zikic, Dejan
2013-01-01
In the frame of a laboratory training course for medicine students, a new approach for laboratory exercises has been applied to teach the phenomena of circulation. The exercise program included measurements of radial artery blood flow waveform for different age groups using a noninvasive optical sensor. Arterial wave reflection was identified by…
Innovative Approaches for Urban Watershed Wet-Weather Flow Management and Control
The “Innovative Approaches for Urban Watershed Wet-Weather Flow Management and Control: State of the Technology” project investigated a range of innovative technology and management strategies emerging outside the normal realm of business within the continental United States, fo...
An algorithm for fast DNS cavitating flows simulations using homogeneous mixture approach
NASA Astrophysics Data System (ADS)
Žnidarčič, A.; Coutier-Delgosha, O.; Marquillie, M.; Dular, M.
2015-12-01
A new algorithm for fast DNS cavitating flows simulations is developed. The algorithm is based on Kim and Moin projection method form. Homogeneous mixture approach with transport equation for vapour volume fraction is used to model cavitation and various cavitation models can be used. Influence matrix and matrix diagonalisation technique enable fast parallel computations.
NASA Astrophysics Data System (ADS)
Carmignani, Luca; Celniker, Greg; Bussett, Kyle; Paolini, Christopher; Bhattacharjee, Subrata
2015-05-01
Opposed-flow flame spread over solid fuels is a fundamental area of research in fire science. Typically combustion wind tunnels are used to generate the opposing flow of oxidizer against which a laminar flame spread occurs along the fuel samples. The spreading flame is generally embedded in a laminar boundary layer, which interacts with the strong buoyancy-induced flow to affect the mechanism of flame spread. In this work, two different approaches for creating the opposed-flow are compared. In the first approach, a vertical combustion tunnel is used where a thin fuel sample, thin acrylic or ashless filter paper, is held vertically along the axis of the test-section with the airflow controlled by controlling the duty cycles of four fans. As the sample is ignited, a flame spreads downward in a steady manner along a developing boundary layer. In the second approach, the sample is held in a movable cart placed in an eight-meter tall vertical chamber filled with air. As the sample is ignited, the cart is moved downward (through a remote-controlled mechanism) at a prescribed velocity. The results from the two approaches are compared to establish the boundary layer effect on flame spread over thin fuels.
Two Experiments to Approach the Boltzmann Factor: Chemical Reaction and Viscous Flow
ERIC Educational Resources Information Center
Fazio, Claudio; Battaglia, Onofrio R.; Guastella, Ivan
2012-01-01
In this paper we discuss a pedagogical approach aimed at pointing out the role played by the Boltzmann factor in describing phenomena usually perceived as regulated by different mechanisms of functioning. Experimental results regarding some aspects of a chemical reaction and of the viscous flow of some liquids are analysed and described in terms…
Wu, Yu-Shu; Lu, Guoping; Zhang, Keni; Pan, Lehua; Bodvarsson,Gudmundur S.
2003-11-03
This paper presents a series of modeling investigations to characterize percolation patterns in the unsaturated zone of Yucca Mountain, Nevada, a proposed underground repository site for storing high-level radioactive waste. The investigations are conducted using a modeling approach that integrates a wide variety of moisture, pneumatic, thermal, and isotopic geochemical field data into a comprehensive three-dimensional numerical model through model calibration. This integrated modeling approach, based on a dual-continuum formulation, takes into account the coupled processes of fluid and heat flow and chemical isotopic transport in Yucca Mountain's highly heterogeneous, unsaturated fractured tuffs. In particular, the model results are examined against different types of field-measured data and used to evaluate different hydrogeological conceptual models and their effects on flow patterns in the unsaturated zone. The objective of this work to provide understanding of percolation patterns and flow behavior through the unsaturated zone, which is a crucial issue in assessing repository performance.
A knowledge-based approach to automated flow-field zoning for computational fluid dynamics
NASA Technical Reports Server (NTRS)
Vogel, Alison Andrews
1989-01-01
An automated three-dimensional zonal grid generation capability for computational fluid dynamics is shown through the development of a demonstration computer program capable of automatically zoning the flow field of representative two-dimensional (2-D) aerodynamic configurations. The applicability of a knowledge-based programming approach to the domain of flow-field zoning is examined. Several aspects of flow-field zoning make the application of knowledge-based techniques challenging: the need for perceptual information, the role of individual bias in the design and evaluation of zonings, and the fact that the zoning process is modeled as a constructive, design-type task (for which there are relatively few examples of successful knowledge-based systems in any domain). Engineering solutions to the problems arising from these aspects are developed, and a demonstration system is implemented which can design, generate, and output flow-field zonings for representative 2-D aerodynamic configurations.
Flow equation approach to one-body and many-body localization
NASA Astrophysics Data System (ADS)
Quito, Victor; Bhattacharjee, Paraj; Pekker, David; Refael, Gil
2014-03-01
We study one-body and many-body localization using the flow equation technique applied to spin-1/2 Hamiltonians. This technique, first introduced by Wegner, allows us to exact diagonalize interacting systems by solving a set of first-order differential equations for coupling constants. Besides, by the flow of individual operators we also compute physical properties, such as correlation and localization lengths, by looking at the flow of probability distributions of couplings in the Hilbert space. As a first example, we analyze the one-body localization problem written in terms of spins, the disordered XY model with a random transverse field. We compare the results obtained in the flow equation approach with the diagonalization in the fermionic language. For the many-body problem, we investigate the physical properties of the disordered XXZ Hamiltonian with a random transverse field in the z-direction.
NASA Astrophysics Data System (ADS)
Chigullapalli, Sruti
Micro-electro-mechanical systems (MEMS) are widely used in automotive, communications and consumer electronics applications with microactuators, micro gyroscopes and microaccelerometers being just a few examples. However, in areas where high reliability is critical, such as in aerospace and defense applications, very few MEMS technologies have been adopted so far. Further development of high frequency microsystems such as resonators, RF MEMS, microturbines and pulsed-detonation microengines require improved understanding of unsteady gas dynamics at the micro scale. Accurate computational simulation of such flows demands new approaches beyond the conventional formulations based on the macroscopic constitutive laws. This is due to the breakdown of the continuum hypothesis in the presence of significant non-equilibrium and rarefaction because of large gradients and small scales, respectively. More generally, the motion of molecules in a gas is described by the kinetic Boltzmann equation which is valid for arbitrary Knudsen numbers. However, due to the multidimensionality of the phase space and the complex non-linearity of the collision term, numerical solution of the Boltzmann equation is challenging for practical problems. In this thesis a fully deterministic, as opposed to a statistical, finite volume based three-dimensional solution of Boltzmann ES-BGK model kinetic equation is formulated to enable simulations of unsteady rarefied flows. The main goal of this research is to develop an unsteady rarefied solver integrated with finite volume method (FVM) solver in MEMOSA (MEMS Overall Simulation Administrator) developed by PRISM: NNSA center for Prediction of Reliability, Integrity and Survivability of Microsystems (PRISM) at Purdue and apply it to study micro-scale gas damping. Formulation and verification of finite volume method for unsteady rarefied flow solver based on Boltzmann-ESBGK equations in arbitrary three-dimensional geometries are presented. The solver is
NASA Astrophysics Data System (ADS)
Delay, Frederick; Porel, Gilles; Chatelier, Marion
2013-07-01
We present a modeling exercise of solute transport and biodegradation in a coarse porous medium widely colonized by a biofilm phase. Tracer tests in large laboratory columns using both conservative (fluorescein) and biodegradable (nitrate) solutes are simulated by means of a dual flowing continuum approach. The latter clearly distinguishes concentrations in a flowing porous phase from concentrations conveyed in the biofilm. With this conceptual setting, it becomes possible to simulate the sharp front of concentrations at early times and the flat tail of low concentrations at late times observed on the experimental breakthrough curves. Thanks to the separation of flow in two phases at different velocities, dispersion coefficients in both flowing phases keep reasonable values with some physical meaning. This is not the case with simpler models based on a single continuum (eventually concealing dead-ends), for which inferred dispersivity may reach the unphysical value of twice the size of the columns. We also show that the behavior of the dual flowing continuum is mainly controlled by the relative fractions of flow passing in each phase and the rate of mass transfer between phases. These parameters also condition the efficiency of nitrate degradation, the degradation rate in a well-seeded medium being a weakly sensitive parameter. Even though the concept of dual flowing continuum appears promising for simulating transport in complex porous media, its inversion onto experimental data really benefits from attempts with simpler models providing a rough pre-evaluation of parameters such as porosity and mean fluid velocity in the system.
Issues and approach to develop validated analysis tools for hypersonic flows: One perspective
NASA Technical Reports Server (NTRS)
Deiwert, George S.
1992-01-01
Critical issues concerning the modeling of low-density hypervelocity flows where thermochemical nonequilibrium effects are pronounced are discussed. Emphasis is on the development of validated analysis tools. A description of the activity in the Ames Research Center's Aerothermodynamics Branch is also given. Inherent in the process is a strong synergism between ground test and real-gas computational fluid dynamics (CFD). Approaches to develop and/or enhance phenomenological models and incorporate them into computational flow-field simulation codes are discussed. These models have been partially validated with experimental data for flows where the gas temperature is raised (compressive flows). Expanding flows, where temperatures drop, however, exhibit somewhat different behavior. Experimental data for these expanding flow conditions are sparse; reliance must be made on intuition and guidance from computational chemistry to model transport processes under these conditions. Ground-based experimental studies used to provide necessary data for model development and validation are described. Included are the performance characteristics of high-enthalpy flow facilities, such as shock tubes and ballistic ranges.
Eulerian Mapping Closure Approach for Probability Density Function of Concentration in Shear Flows
NASA Technical Reports Server (NTRS)
He, Guowei; Bushnell, Dennis M. (Technical Monitor)
2002-01-01
The Eulerian mapping closure approach is developed for uncertainty propagation in computational fluid mechanics. The approach is used to study the Probability Density Function (PDF) for the concentration of species advected by a random shear flow. An analytical argument shows that fluctuation of the concentration field at one point in space is non-Gaussian and exhibits stretched exponential form. An Eulerian mapping approach provides an appropriate approximation to both convection and diffusion terms and leads to a closed mapping equation. The results obtained describe the evolution of the initial Gaussian field, which is in agreement with direct numerical simulations.
NASA Astrophysics Data System (ADS)
Zacny, K.; Nagihara, S.; Hedlund, M.; Paulsen, G.; Shasho, J.; Mumm, E.; Kumar, N.; Szwarc, T.; Chu, P.; Craft, J.; Taylor, P.; Milam, M.
2013-11-01
In this paper, the development of heat flow probes for measuring the geothermal gradient and conductivity of lunar regolith are presented. These two measurements are the required information for determining the heat flow of a planetary body. Considering the Moon as an example, heat flow properties are very important information for studying the radiogenic isotopes, the thermal evolution and differentiation history, and the mechanical properties of the interior. In order to obtain the best measurements, the sensors must be extended to a depth of at least 3 m, i.e. beyond the depth of significant thermal cycles. Two approaches to heat flow deployment and measurement are discussed in this paper: a percussive approach and a pneumatic approach. The percussive approach utilizes a high frequency hammer to drive a cone penetrometer into the lunar simulant. Ring-like thermal sensors (heaters and temperature sensors) on the penetrometer rod are deployed into the simulant every 30 cm as the penetrometer penetrates to the required 3 m depth. Once the target depth has been achieved, the deployment rod is removed from the simulant, eliminating any thermal path to the lander. The pneumatic approach relies on pressurized gas to excavate, using a cone-shaped nozzle to penetrate the simulant. The nozzle is attached to a coiled stem with thermal sensors embedded along the length of the stem. As the simulant is being lofted out of the hole by the escaping gas, the stem is progressively reeled out from a spool, thus moving the cone deeper into the hole. Thermal conductivity is measured using a needle probe attached to the end of the cone. Breadboard prototypes of these two heat flow probe systems have been constructed and successfully tested under lunar-like conditions to approximately 70 cm, which was the maximum possible depth allowed by the size of the test bin and the chamber.
Comparison of two inlet boundary approaches in numerical simulation of car ventilation outlet flow
NASA Astrophysics Data System (ADS)
Talanda, Tomáš; Niedoba, Pavel; Lízal, František; Jícha, Miroslav
2016-03-01
The paper is concerned with the comparison of two inlet boundary approaches of numerical simulations. The first approach is based on the simulation of a sufficiently long duct upstream the area of interest with known volumetric flow rate. The second approach rests on the experimental measurement of the section closer to the area of interest. The experimental measurement provides velocity profile and in addition turbulent intensity compared to the first approach where only a velocity profile can be computed according to known volumetric flow rate. A simplified model of car ventilation outlet was chosen as a test case. The model consists of circular and rectangular duct, area of interest (closing flap, vertical slats and horizontal slats) and outlet box. We have compared the two mentioned inlet boundary approaches for two distinct values of volumetric flow rate for which the experimental data of the section upstream of the area of interest are available. The velocity and the turbulent kinetic energy profiles downstream of the area of interest were chosen as comparative characteristics.
Pressure from particle image velocimetry for convective flows: a Taylor’s hypothesis approach
NASA Astrophysics Data System (ADS)
de Kat, R.; Ganapathisubramani, B.
2013-02-01
Taylor’s hypothesis is often applied in turbulent flow analysis to map temporal information into spatial information. Recent efforts in deriving pressure from particle image velocimetry (PIV) have proposed multiple approaches, each with its own weakness and strength. Application of Taylor’s hypothesis allows us to counter the weakness of an Eulerian approach that is described by de Kat and van Oudheusden (2012 Exp. Fluids 52 1089-106). Two different approaches of using Taylor’s hypothesis in determining planar pressure are investigated: one where pressure is determined from volumetric PIV data and one where pressure is determined from time-resolved stereoscopic PIV data. A performance assessment on synthetic data shows that application of Taylor’s hypothesis can improve determination of pressure from PIV data significantly compared with a time-resolved volumetric approach. The technique is then applied to time-resolved PIV data taken in a cross-flow plane of a turbulent jet (Ganapathisubramani et al 2007 Exp. Fluids 42 923-39). Results appear to indicate that pressure can indeed be obtained from PIV data in turbulent convective flows using the Taylor’s hypothesis approach, where there are no other methods to determine pressure. The role of convection velocity in determination of pressure is also discussed.
NASA Astrophysics Data System (ADS)
Mott Lacroix, Kelly E.; Xiu, Brittany C.; Megdal, Sharon B.
2016-04-01
Despite increased understanding of the science of environmental flows, identification and implementation of effective environmental flow policies remains elusive. Perhaps the greatest barrier to implementing flow policies is the framework for water management. An alternative management approach is needed when legal rights for environmental flows do not exist, or are ineffective at protecting ecosystems. The research presented here, conducted in the U.S. state of Arizona, provides an empirical example of engagement to promote social learning as an approach to finding ways to provide water for the environment where legal rights for environmental flows are inadequate. Based on our engagement process we propose that identifying and then building common ground require attention to the process of analyzing qualitative data and the methods for displaying complex information, two aspects not frequently discussed in the social learning or stakeholder engagement literature. The results and methods from this study can help communities develop an engagement process that will find and build common ground, increase stakeholder involvement, and identify innovative solutions to provide water for the environment that reflect the concerns of current water users.
Xu, Tianfu; Pruess, Karsten
2000-08-08
Reactive fluid flow and geochemical transport in unsaturated fractured rocks has received increasing attention for studies of contaminant transport, groundwater quality, waste disposal, acid mine drainage remediation, mineral deposits, sedimentary diagenesis, and fluid-rock interactions in hydrothermal systems. This paper presents methods for modeling geochemical systems that emphasize: (1) involvement of the gas phase in addition to liquid and solid phases in fluid flow, mass transport and chemical reactions, (2) treatment of physically and chemically heterogeneous and fractured rocks, (3) the effect of heat on fluid flow and reaction properties and processes, and (4) the kinetics of fluid-rock interaction. The physical and chemical process model is embodied in a system of partial differential equations for flow and transport, coupled to algebraic equations and ordinary differential equations for chemical interactions. For numerical solution, the continuum equations are discretized in space and time. Space discretization is based on a flexible integral finite difference approach that can use irregular gridding to model geologic structure; time is discretized fully implicitly as a first-order finite difference. Heterogeneous and fractured media are treated with a general multiple interacting continua method that includes double-porosity, dual-permeability, and multi-region models as special cases. A sequential iteration approach is used to treat the coupling between fluid flow and mass transport on the one hand, chemical reactions on the other. Applications of the methods developed here to variably saturated geochemical systems are presented in a companion paper (part 2, this issue).
Preferential Water Flow in a Frozen Soil - a Two-Domain Model Approach
NASA Astrophysics Data System (ADS)
Stähli, Manfred; Jansson, Per-Erik; Lundin, Lars-Christer
1996-10-01
Earlier modelling studies have shown the difficulty of accurately simulating snowmelt infiltration into frozen soil using the hydraulic model approach. Comparison of model outputs and field measurements have inferred the occurrence of rapid flow even during periods when the soil is still partly frozen. A one-dimensional, physically based soil water and heat model (SOIL) has been complemented with a new two-domain approach option to simulate preferential flow through frozen layers. The ice is assumed to be first formed at the largest water filled pore upon freezing. Infiltrating water may be conducted rapidly through previously air-filled pores which are not occupied by ice. A minor fraction of water is slowly transferred within the liquid water domain, which is absorbed by the solid particles. A model validation with field measurements at a location in the middle-east of Sweden indicated that the two-domain approach was suitable for improving the prediction of drainage during snowmelting. In particular, the correlation between simulated and observed onset of drainage in spring was improved. The validation also showed that the effect of the high flow domain was highly sensitive to the degree of saturation in the topsoil during freezing, as well as to the hydraulic properties at the lower frost boundary regulating the upward water flow to the frozen soil and ice formation.
High-energy ions produced by two approaching flow fronts in the magnetotail
NASA Astrophysics Data System (ADS)
Uchino, H.; Ieda, A.; Machida, S.; Imada, S.
2015-12-01
During a substorm event in 2009, THEMIS probes observed high-energy (≲ 1MeV) ions and characteristic time evolution of the differential flux. The high-energy ions seem to be produced in the magnetotail, but existing acceleration theories cannot explain the production of such high-energy ions due to the limitation of dawn-dusk (DD) flow scale. We propose that if two approaching flow fronts exist simultaneously in the magnetotail, the production of high-energy ions can be achieved. Namely, some ideal ions are repeatedly reflected by the two fronts and accelerated to high energies, exceeding the energy-limit given by the product of the duskward electric field and DD scale length of the flows. In addition, this acceleration model similar to "first-order Fermi acceleration" can produce the observed differential flux change. We have analytically calculated the energy-gain of each ion between two approaching flow fronts, and roughly estimated the efficiency of the acceleration and the spectrum change. In order to include the DD flow scale, we have further performed a spatially 1-D (2-D in velocity) test particle simulation where a couple of flow fronts approach each other. Using the simulation, we have confirmed the production of high-energy ions as well as the change of the energy spectrum of ions associated with the acceleration. The simulation result shows that high-energy ions can be produced with shorter DD scale length compared to that of the simple acceleration for trapped particles in the flow front. If we assume that the DD scale length of the flow is 10Re, the simulated ion maximum energy near 1MeV and differential flux change are similar to those of the observation. This scale length is less than half of the length needed for the product with the duskward electric field to produce 1MeV ions. This estimated 10Re flow scale in that event does not contradict previous studies.
A new approach to wall modeling in LES of incompressible flow via function enrichment
NASA Astrophysics Data System (ADS)
Krank, Benjamin; Wall, Wolfgang A.
2016-07-01
A novel approach to wall modeling for the incompressible Navier-Stokes equations including flows of moderate and large Reynolds numbers is presented. The basic idea is that a problem-tailored function space allows prediction of turbulent boundary layer gradients with very coarse meshes. The proposed function space consists of a standard polynomial function space plus an enrichment, which is constructed using Spalding's law-of-the-wall. The enrichment function is not enforced but "allowed" in a consistent way and the overall methodology is much more general and also enables other enrichment functions. The proposed method is closely related to detached-eddy simulation as near-wall turbulence is modeled statistically and large eddies are resolved in the bulk flow. Interpreted in terms of a three-scale separation within the variational multiscale method, the standard scale resolves large eddies and the enrichment scale represents boundary layer turbulence in an averaged sense. The potential of the scheme is shown applying it to turbulent channel flow of friction Reynolds numbers from Reτ = 590 and up to 5,000, flow over periodic constrictions at the Reynolds numbers ReH = 10 , 595 and 19,000 as well as backward-facing step flow at Reh = 5 , 000, all with extremely coarse meshes. Excellent agreement with experimental and DNS data is observed with the first grid point located at up to y1+ = 500 and especially under adverse pressure gradients as well as in separated flows.
A Fundamental Approach to the Simulation of Flow and Dispersion in Fractured Media
Miller, J.D.
1983-12-15
Fracture systems may be generalized in terms of number and orientation of sets of parallel fractures and the distribution of length, width, thickness and separation. Borehole measurements may be used to particularize these parameters for a specific site. Global flow and dispersion in an aquifer occur in the interconnected fractures and may be related to specific fracture elements. A fluid dynamics code named SALE has been used to solve the Navier-Stokes equations for laminar flow in these elemental geometries. A marker particle calculation has been added to characterize longitudinal dispersion due to the velocity profile across the fracture and lateral dispersion due to flow disturbances at junctions. Local flow and dispersion in the matrix occur in the finer fracture structure and are evaluated using porous media approaches. These results or models are integrated in a 2D isothermal reservoir simulator named FRACSL. Discrete fractures are superimposed on the edges or diagnoals of rectangular grid elements. Water may flow from node to node through the matrix or through the fracture. The heads are found by iterating for the distribution which conserves the appropriate local mass. Marker particles are used to monitor the tracer dispersion due to motion in the fractures, in the matrix and between the two. Results are given showing flow and dispersion in an orthogonal junction and in a sample fractured reservoir.
Sequential approach to joint flow-seismic inversion for improved characterization of fractured media
NASA Astrophysics Data System (ADS)
Kang, Peter K.; Zheng, Yingcai; Fang, Xinding; Wojcik, Rafal; McLaughlin, Dennis; Brown, Stephen; Fehler, Michael C.; Burns, Daniel R.; Juanes, Ruben
2016-02-01
Seismic interpretation of subsurface structures is traditionally performed without any account of flow behavior. Here we present a methodology for characterizing fractured geologic reservoirs by integrating flow and seismic data. The key element of the proposed approach is the identification—within the inversion—of the intimate relation between fracture compliance and fracture transmissivity, which determine the acoustic and flow responses of a fractured reservoir, respectively. Owing to the strong (but highly uncertain) dependence of fracture transmissivity on fracture compliance, the modeled flow response in a fractured reservoir is highly sensitive to the geophysical interpretation. By means of synthetic models, we show that by incorporating flow data (well pressures and tracer breakthrough curves) into the inversion workflow, we can simultaneously reduce the error in the seismic interpretation and improve predictions of the reservoir flow dynamics. While the inversion results are robust with respect to noise in the data for this synthetic example, the applicability of the methodology remains to be tested for more complex synthetic models and field cases.
Issues and approach to develop validated analysis tools for hypersonic flows: One perspective
NASA Technical Reports Server (NTRS)
Deiwert, George S.
1993-01-01
Critical issues concerning the modeling of low density hypervelocity flows where thermochemical nonequilibrium effects are pronounced are discussed. Emphasis is on the development of validated analysis tools, and the activity in the NASA Ames Research Center's Aerothermodynamics Branch is described. Inherent in the process is a strong synergism between ground test and real gas computational fluid dynamics (CFD). Approaches to develop and/or enhance phenomenological models and incorporate them into computational flowfield simulation codes are discussed. These models were partially validated with experimental data for flows where the gas temperature is raised (compressive flows). Expanding flows, where temperatures drop, however, exhibit somewhat different behavior. Experimental data for these expanding flow conditions is sparse and reliance must be made on intuition and guidance from computational chemistry to model transport processes under these conditions. Ground based experimental studies used to provide necessary data for model development and validation are described. Included are the performance characteristics of high enthalpy flow facilities, such as shock tubes and ballistic ranges.
Cardinal, Trevor R.; Hoying, James B.
2007-01-01
The goal of this study was to develop a modified fluorescent microsphere-based approach for measuring resting and hyperemic blood flows in individual mouse skeletal muscles. Absolute resting blood flow in the left gracilis posterior was 1.04±0.12 ml·min−1·g−1, while functional hyperemia following muscle activity was 5.94±1.33 ml·min−1·g−1. Measuring absolute blood flow requires sampling arterial blood that serves as a flow-rate and concentration reference to the fluorescent microsphere (FMS) content in the tissue-of-interest for calculating the flow value. Because sampling arterial blood can impair cardiovascular function in the mouse, we also modified our FMS approach to determine relative blood flows in the left gracilis posterior by using the contralateral muscle as our reference in blood flow calculations. Absolute and relative hyperemia measurements detect similar increases in blood flow — 521.93±216.76% and 555.24±213.82%, respectively. However, sampling arterial blood during absolute blood flow measurements significantly decreased mean arterial pressure from the beginning to the end of our experiments, from 102.7±2.18 to 75.5±9.71 mm Hg. This decrease was not seen when measuring relative blood flows. This approach provides critical advantages over contemporary blood flow measurement approaches by allowing blood flow measurements in small and non-superficial tissues. PMID:17500044
The Hawaiian Volcano Observatory's current approach to forecasting lava flow hazards (Invited)
NASA Astrophysics Data System (ADS)
Kauahikaua, J. P.
2013-12-01
Hawaiian Volcanoes are best known for their frequent basaltic eruptions, which typically start with fast-moving channelized `a`a flows fed by high eruptions rates. If the flows continue, they generally transition into pahoehoe flows, fed by lower eruption rates, after a few days to weeks. Kilauea Volcano's ongoing eruption illustrates this--since 1986, effusion at Kilauea has mostly produced pahoehoe. The current state of lava flow simulation is quite advanced, but the simplicity of the models mean that they are most appropriately used during the first, most vigorous, days to weeks of an eruption - during the effusion of `a`a flows. Colleagues at INGV in Catania have shown decisively that MAGFLOW simulations utilizing satellite-derived eruption rates can be effective at estimating hazards during the initial periods of an eruption crisis. However, the algorithms do not simulate the complexity of pahoehoe flows. Forecasts of lava flow hazards are the most common form of volcanic hazard assessments made in Hawai`i. Communications with emergency managers over the last decade have relied on simple steepest-descent line maps, coupled with empirical lava flow advance rate information, to portray the imminence of lava flow hazard to nearby communities. Lavasheds, calculated as watersheds, are used as a broader context for the future flow paths and to advise on the utility of diversion efforts, should they be contemplated. The key is to communicate the uncertainty of any approach used to formulate a forecast and, if the forecast uses simple tools, these communications can be fairly straightforward. The calculation of steepest-descent paths and lavasheds relies on the accuracy of the digital elevation model (DEM) used, so the choice of DEM is critical. In Hawai`i, the best choice is not the most recent but is a 1980s-vintage 10-m DEM--more recent LIDAR and satellite radar DEM are referenced to the ellipsoid and include vegetation effects. On low-slope terrain, steepest
Some Approaches to Modeling Diffuse Flow at Mid-Ocean Ridges
NASA Astrophysics Data System (ADS)
Farough, A.; Lowell, R. P.; Craft, K.; Germanovich, L. N.
2011-12-01
To obtain a sound understanding of subsurface temperatures and the extent of the subsurface biosphere in young oceanic crust, one must understand the mechanisms of diffuse flow at oceanic spreading centers. Mathematical modeling of diffuse flow at oceanic spreading centers has received relatively little attention compared to high-temperature black smoker discharge, in part because the temperature and fluid flow data required to constrain the models are scarce. We review a number of different approaches to modelling diffuse flow: (1) The simplest method considers 1-D steady-state uniform upflow from below subject to a heat transfer boundary condition at the surface, which represents the effects of mixing of hydrothermal fluid with seawater. These models, in which the heat transfer coefficient and the velocity of the ascending fluid are constrained by observed diffuse flow vent temperature and heat flux, typically result in a steep temperature gradient near the seafloor and subsurface biological activity may be limited to the upper few cm of the crust. (2) A related method uses data on the partitioning of heat flux between focused and diffuse flow and chemical data from the focused and diffuse flow components in a two-limb single pass modeling approach to determine the fraction of high-temperature fluid that is incorporated in the diffuse flow. Using data available from EPR 950', the Main Endeavour Field, and ASHES vent field at Axial Volcano on the Juan de Fuca Ridge in conjunction with Mg as a passive tracer, we find that the mixing ratio of high temperature in diffuse flow is <10%. The high-temperature contribution to the diffuse heat flux remains large, however, and high-temperature vent fluid ultimately contributes ~ 90% of the total heat output from the vent field. In these models mixing between high-temperature fluid and seawater may occur over a considerable depth, and the subsurface biosphere may be ~ 100 m deep beneath diffuse flow sites. (3) Finally, in
The design/analysis of flows through turbomachinery - A viscous/inviscid approach
NASA Astrophysics Data System (ADS)
Miller, D. P.; Reddy, D. R.
1991-06-01
A new design/analysis system for the flows through turbomachinery is currently being developed for studying turbomachinery problems with an axisymmetric viscous/inviscid 'average-passage' throughflow code. The advantage of this approach, compared to streamline curvature codes, is that the solutions obtained simulate some of the unsteadiness, compressibility and viscous effects of a multistage turbomachine. The design/analysis system consists of three elemental parts, the axisymmetric block grid generator, the blade surface element code, and the axisymmetric flow code. Each element of the system will be discussed and the flow solutions for three axisymmetric geometries will be shown compared to experimental data where available. The computations are shown to be in very good agreement with test data for SR7 spinner body and transonic boattail geometry obtained in the wind tunnels at NASA Lewis Research Center. The VIADAC Rotor 67 Fan results were compared to PARC2D calculated results and shown to be in very good agreement.
Navier-Stokes simulation of transonic wing flow fields using a zonal grid approach
NASA Technical Reports Server (NTRS)
Chaderjian, Neal M.
1988-01-01
The transonic Navier-Stokes code was used to simulate flow fields about isolated wings for workshop wind-tunnel and free-air cases using the thin-layer Reynolds-averaged Navier-Stokes equations. An implicit finite-difference scheme based on a diagonal version of the Beam-Warming algorithm was used to integrate the governing equations. A zonal grid approach was used to allow efficient grid refinement near the wing surface. The flow field was sensitive to the turbulent transition model, and flow unsteadiness was observed for a wind-tunnel case but not for the corresponding free-air case. The specification of experimental pressure at the wind-tunnel exit plane is the primary reason for the difference of these two numerical solutions.
The moving boundary approach to modeling gravity-driven stable and unstable flow in soils
NASA Astrophysics Data System (ADS)
Brindt, Naaran; Wallach, Rony
2016-04-01
Many field and laboratory studies in the last 40 years have found that water flow in homogeneous soil profiles may occur in preferential flow pathways rather than in a laterally uniform wetting front, as expected from classical soil physics theory and expressed by the Richards equation. The water-content distribution within such gravity-driven fingers was found to be nonmonotonic due to water accumulation behind a sharp wetting front (denoted as saturation overshoot). The unstable flow was first related to soil coarseness. However, its appearance in water-repellent soils led the authors to hypothesize that gravity-driven unstable flow formation is triggered by a non-zero contact angle between water and soil particles. Despite its widespread occurrence, a macroscopic-type model describing the nonmonotonic water distribution and sharp wetting front is still lacking. The moving boundary approach, which divides the flow domain into two well-defined subdomains with a sharp change in fluid saturation between them, is suggested to replace the classical approach of solving the Richards equation for the entire flow domain. The upper subdomain consists of water and air, whose relationship varies with space and time following the imposed boundary condition at the soil surface as calculated by the Richards equation. The lower subdomain also consists of water and air, but their relationship remains constant following the predetermined initial condition. The moving boundary between the two subdomains is the sharp wetting front, whose location is part of the solution. As such, the problem is inherently nonlinear. The wetting front's movement is controlled by the dynamic water-entry pressure of the soil, which depends on soil wettability and the front's propagation rate. A lower soil wettability, which hinders the spontaneous invasion of dry pores and increases the water-entry pressure, induces a sharp wetting front and water accumulation behind it. The wetting front starts to
A hydrogeological conceptual approach to study urban groundwater flow in Bucharest city, Romania
NASA Astrophysics Data System (ADS)
Boukhemacha, Mohamed Amine; Gogu, Constantin Radu; Serpescu, Irina; Gaitanaru, Dragos; Bica, Ioan
2015-05-01
Management of groundwater systems in urban areas is necessary and can be reliably performed by means of mathematical modeling combined with geospatial analysis. A conceptual approach for the study of urban hydrogeological systems is presented. The proposed approach is based on the features of Bucharest city (Romania) and can be adapted to other urban areas showing similar characteristics. It takes into account the interaction between groundwater and significant urban infrastructure elements that can be encountered in modern cities such as subway tunnels and water-supply networks, and gives special attention to the sewer system. In this respect, an adaptation of the leakage factor approach is proposed, which uses a sewer-system zoning function related to the conduits' location in the aquifer system and a sewer-conduits classification function related to their structural and/or hydraulic properties. The approach was used to elaborate a single-layered steady state groundwater flow model for a pilot zone of Bucharest city.
Approaching a universal scaling relationship between fracture stiffness and fluid flow
NASA Astrophysics Data System (ADS)
Pyrak-Nolte, Laura J.; Nolte, David D.
2016-02-01
A goal of subsurface geophysical monitoring is the detection and characterization of fracture alterations that affect the hydraulic integrity of a site. Achievement of this goal requires a link between the mechanical and hydraulic properties of a fracture. Here we present a scaling relationship between fluid flow and fracture-specific stiffness that approaches universality. Fracture-specific stiffness is a mechanical property dependent on fracture geometry that can be monitored remotely using seismic techniques. A Monte Carlo numerical approach demonstrates that a scaling relationship exists between flow and stiffness for fractures with strongly correlated aperture distributions, and continues to hold for fractures deformed by applied stress and by chemical erosion as well. This new scaling relationship provides a foundation for simulating changes in fracture behaviour as a function of stress or depth in the Earth and will aid risk assessment of the hydraulic integrity of subsurface sites.
A triple-continuum approach for modeling flow and transport processes in fractured rock.
Wu, Yu-Shu; Liu, H H; Bodvarsson, G S
2004-09-01
This paper presents a triple-continuum conceptual model for simulating flow and transport processes in fractured rock. Field data collected from the unsaturated zone of Yucca Mountain, a repository site of high-level nuclear waste, show a large number of small-scale fractures. The effect of these small fractures has not been considered in previous modeling investigations within the context of a continuum approach. A new triple-continuum model (consisting of matrix, small-fracture, and large-fracture continua) has been developed to investigate the effect of these small fractures. This paper derives the model formulation and discusses the basic triple-continuum behavior of flow and transport processes under different conditions, using both analytical solutions and numerical approaches. The simulation results from the site-scale model of the unsaturated zone of Yucca Mountain indicate that these small fractures may have an important effect on radionuclide transport within the mountain. PMID:15336793
An approach to the segmentation of multi-page document flow using binary classification
NASA Astrophysics Data System (ADS)
Agin, Onur; Ulas, Cagdas; Ahat, Mehmet; Bekar, Can
2015-03-01
In this paper, we present a method for segmentation of document page flow applied to heterogeneous real bank documents. The approach is based on the content of images and it also incorporates font based features inside the documents. Our method involves a bag of visual words (BoVW) model on the designed image based feature descriptors and a novel approach to combine the consecutive pages of a document into a single feature vector that represents the transition between these pages. The transitions here could be represented by one of the two different classes: continuity of the same document or beginning of a new document. Using the transition feature vectors, we utilize three different binary classifiers to make predictions on the relationship between consecutive pages. Our initial results demonstrate that the proposed method can exhibit promising performance for document flow segmentation at this stage.
Approaching a universal scaling relationship between fracture stiffness and fluid flow.
Pyrak-Nolte, Laura J; Nolte, David D
2016-01-01
A goal of subsurface geophysical monitoring is the detection and characterization of fracture alterations that affect the hydraulic integrity of a site. Achievement of this goal requires a link between the mechanical and hydraulic properties of a fracture. Here we present a scaling relationship between fluid flow and fracture-specific stiffness that approaches universality. Fracture-specific stiffness is a mechanical property dependent on fracture geometry that can be monitored remotely using seismic techniques. A Monte Carlo numerical approach demonstrates that a scaling relationship exists between flow and stiffness for fractures with strongly correlated aperture distributions, and continues to hold for fractures deformed by applied stress and by chemical erosion as well. This new scaling relationship provides a foundation for simulating changes in fracture behaviour as a function of stress or depth in the Earth and will aid risk assessment of the hydraulic integrity of subsurface sites. PMID:26868649
Approaching a universal scaling relationship between fracture stiffness and fluid flow
Pyrak-Nolte, Laura J.; Nolte, David D.
2016-01-01
A goal of subsurface geophysical monitoring is the detection and characterization of fracture alterations that affect the hydraulic integrity of a site. Achievement of this goal requires a link between the mechanical and hydraulic properties of a fracture. Here we present a scaling relationship between fluid flow and fracture-specific stiffness that approaches universality. Fracture-specific stiffness is a mechanical property dependent on fracture geometry that can be monitored remotely using seismic techniques. A Monte Carlo numerical approach demonstrates that a scaling relationship exists between flow and stiffness for fractures with strongly correlated aperture distributions, and continues to hold for fractures deformed by applied stress and by chemical erosion as well. This new scaling relationship provides a foundation for simulating changes in fracture behaviour as a function of stress or depth in the Earth and will aid risk assessment of the hydraulic integrity of subsurface sites. PMID:26868649
NASA Astrophysics Data System (ADS)
Mahmoudi, M.; Nalesso, M.; Garcia, R. F.; Miralles-Wilhelm, F.
2013-05-01
cells in LILA. The constant flowing cell, M2, was selected as the study area. Flow was simulated using FLO2D, a FEMA approved program that simulates flow depth and velocity by using modified manning's roughness coefficient based on vegetation drag approach. The result of this simulation will provide an improved understanding of the effect of vegetation dynamics on hydrology and how different vegetation type and density may change flow velocity and therefore sediment transport over time.
A genetic algorithm-based approach to flexible flow-line scheduling with variable lot sizes.
Lee, I; Sikora, R; Shaw, M J
1997-01-01
Genetic algorithms (GAs) have been used widely for such combinatorial optimization problems as the traveling salesman problem (TSP), the quadratic assignment problem (QAP), and job shop scheduling. In all of these problems there is usually a well defined representation which GA's use to solve the problem. We present a novel approach for solving two related problems-lot sizing and sequencing-concurrently using GAs. The essence of our approach lies in the concept of using a unified representation for the information about both the lot sizes and the sequence and enabling GAs to evolve the chromosome by replacing primitive genes with good building blocks. In addition, a simulated annealing procedure is incorporated to further improve the performance. We evaluate the performance of applying the above approach to flexible flow line scheduling with variable lot sizes for an actual manufacturing facility, comparing it to such alternative approaches as pair wise exchange improvement, tabu search, and simulated annealing procedures. The results show the efficacy of this approach for flexible flow line scheduling. PMID:18255838
A simplified approach for the computation of steady two-phase flow in inverted siphons.
Diogo, A Freire; Oliveira, Maria C
2016-01-15
Hydraulic, sanitary, and sulfide control conditions of inverted siphons, particularly in large wastewater systems, can be substantially improved by continuous air injection in the base of the inclined rising branch. This paper presents a simplified approach that was developed for the two-phase flow of the rising branch using the energy equation for a steady pipe flow, based on the average fluid fraction, observed slippage between phases, and isothermal assumption. As in a conventional siphon design, open channel steady uniform flow is assumed in inlet and outlet chambers, corresponding to the wastewater hydraulic characteristics in the upstream and downstream sewers, and the descending branch operates in steady uniform single-phase pipe flow. The proposed approach is tested and compared with data obtained in an experimental siphon setup with two plastic barrels of different diameters operating separately as in a single-barrel siphon. Although the formulations developed are very simple, the results show a good adjustment for the set of the parameters used and conditions tested and are promising mainly for sanitary siphons with relatively moderate heights of the ascending branch. PMID:26517278
Advanced digital methods for blood flow flux analysis using µPIV approach
NASA Astrophysics Data System (ADS)
Kurochkin, Maxim A.; Timoshina, Polina A.; Fedosov, Ivan V.; Tuchin, Valery V.
2015-03-01
A digital optical system focused on work with laboratory animals for intravital capillaroscopy has been developed. It implements the particle image velocimetry (PIV) based approach for measurements of red blood cells velocity in laboratory rat stomach capillaries. We propose a method of involuntary displacement compensation of the capillary network images. Image stabilization algorithm is based on correlation of feature tracking. The efficiency of designed image stabilization algorithm was experimentally demonstrated. The results of capillary blood flow analysis are demonstrated.
Computation of wall bounded flows with heat transfer in the framework of SRS approaches
NASA Astrophysics Data System (ADS)
Gritskevich, M. S.; Garbaruk, A. V.; Menter, F. R.
2014-12-01
A detailed assessment of Scale Adaptive Simulation (SAS) and Improved Delayed Detached Eddy Simulation (IDDES) is performed for prediction of heat transfer for several wall bounded flow. For that purpose a zero pressure gradient boundary layer, a backward facing step, and a thermal mixing in a T-Junction test cases are considered. The results, obtained with the use of ANSYS-FLUENT, show that both approaches are capable to predict both mean and RMS velocity and temperature with sufficient accuracy.
Large-eddy simulation of approaching-flow stratification on dispersion over arrays of buildings
NASA Astrophysics Data System (ADS)
Xie, Zheng-Tong; Hayden, Paul; Wood, Curtis R.
2013-06-01
The study investigates thermal stratification effects of approach flows on dispersion in urban environments. This is in some ways analogous to a well-developed non-neutral flow (e.g. through a large urban area) approaching a neighbourhood-scale urban region, where the effect of the local heat transfer was assumed less important. A generic urban-type geometry, i.e. a group of staggered cubes, was taken as the first test case. The DAPPLE site, which was about a one-km2 region near the intersection of Marylebone Road and Gloucester Place in central London, was taken as the second test case. Only weakly unstable conditions (i.e. bulk Richardson number R≥-0.2) of approach flows were considered, with adiabatic boundary conditions at the ground and building surfaces. A number of numerical experiments were performed. The modelled mean concentration for Rb = -0.1 gave the best agreement with the field data at all DAPPLE stations. This suggests that stratification effects on dispersion in weakly unstable conditions (e.g. in London) are not negligible.
NASA Technical Reports Server (NTRS)
Goldstein, David B.; Varghese, Philip L.
1997-01-01
We proposed to create a single computational code incorporating methods that can model both rarefied and continuum flow to enable the efficient simulation of flow about space craft and high altitude hypersonic aerospace vehicles. The code was to use a single grid structure that permits a smooth transition between the continuum and rarefied portions of the flow. Developing an appropriate computational boundary between the two regions represented a major challenge. The primary approach chosen involves coupling a four-speed Lattice Boltzmann model for the continuum flow with the DSMC method in the rarefied regime. We also explored the possibility of using a standard finite difference Navier Stokes solver for the continuum flow. With the resulting code we will ultimately investigate three-dimensional plume impingement effects, a subject of critical importance to NASA and related to the work of Drs. Forrest Lumpkin, Steve Fitzgerald and Jay Le Beau at Johnson Space Center. Below is a brief background on the project and a summary of the results as of the end of the grant.
A network theory approach for a better understanding of overland flow connectivity
NASA Astrophysics Data System (ADS)
Masselink, Rens; Heckmann, Tobias; Temme, Arnaud; Anders, Niels; Keesstra, Saskia
2016-04-01
Hydrological connectivity describes the physical coupling, or linkages of different elements within a landscape regarding (sub)surface flows. A firm understanding of hydrological connectivity is important for catchment management applications, for e.g. habitat and species protection, and for flood resistance and resilience improvement. Thinking about (geomorphological) systems as networks can lead to new insights, which has been recognised within the scientific community as well, seeing the recent increase in the use of network (graph) theory within the geosciences. Network theory supports the analysis and understanding of complex systems by providing data structures for modelling objects and their linkages, and a versatile toolbox to quantitatively appraise network structure and properties. The objective of this study was to characterise overland flow connectivity dynamics on hillslopes in a humid sub-Mediterranean environment by using a combination of high-resolution digital-terrain models, overland flow sensors and a network approach. Results showed that there are significant differences between overland flow on agricultural areas and semi-natural shrubs areas. Positive correlations between connectivity and precipitation characteristics were found, while negative correlations between connectivity and soil moisture were found, probably due to soil water repellency. The combination of a structural network to determine potential connectivity with dynamic networks to determine the actual connectivity proved a powerful tool in analysing overland flow connectivity.
NASA Astrophysics Data System (ADS)
Keylock, C. J.; Constantinescu, G.; Hardy, R. J.
2012-12-01
In the last decade, as computing power has increased, there has been an explosion in the use of eddy-resolving numerical methods in the engineering, earth and environmental sciences. For complex geomorphic flows, where accurate field investigations are difficult to perform and where experiments may be difficult to scale, these numerical approaches are beginning to give key insights into the nature of these flows. Eddy-resolving methods such as Large and Detached Eddy Simulation (LES/DES) may be contrasted with the time-averaged, three-dimensional simulations that only really began to be applied seriously in geomorphology fifteen years ago. While the potential of LES for geomorphology has been examined previously, DES is a relatively recent method that deserves further consideration. In this paper, we explain the method and then utilise examples from meander and confluence flows, as well as flow near the bed of a gravel bed river, to highlight the improvements to both the representation of the mean flow, and to the representation of time-varying processes, that result from the use of LES/DES. Some suggestions are provided for the future use of such techniques in geomorphology.
NASA Astrophysics Data System (ADS)
Chang, Ching-Min; Yeh, Hund-Der
2009-01-01
This paper describes a stochastic analysis of steady state flow in a bounded, partially saturated heterogeneous porous medium subject to distributed infiltration. The presence of boundary conditions leads to non-uniformity in the mean unsaturated flow, which in turn causes non-stationarity in the statistics of velocity fields. Motivated by this, our aim is to investigate the impact of boundary conditions on the behavior of field-scale unsaturated flow. Within the framework of spectral theory based on Fourier-Stieltjes representations for the perturbed quantities, the general expressions for the pressure head variance, variance of log unsaturated hydraulic conductivity and variance of the specific discharge are presented in the wave number domain. Closed-form expressions are developed for the simplified case of statistical isotropy of the log hydraulic conductivity field with a constant soil pore-size distribution parameter. These expressions allow us to investigate the impact of the boundary conditions, namely the vertical infiltration from the soil surface and a prescribed pressure head at a certain depth below the soil surface. It is found that the boundary conditions are critical in predicting uncertainty in bounded unsaturated flow. Our analytical expression for the pressure head variance in a one-dimensional, heterogeneous flow domain, developed using a nonstationary spectral representation approach [Li S-G, McLaughlin D. A nonstationary spectral method for solving stochastic groundwater problems: unconditional analysis. Water Resour Res 1991;27(7):1589-605; Li S-G, McLaughlin D. Using the nonstationary spectral method to analyze flow through heterogeneous trending media. Water Resour Res 1995; 31(3):541-51], is precisely equivalent to the published result of Lu et al. [Lu Z, Zhang D. Analytical solutions to steady state unsaturated flow in layered, randomly heterogeneous soils via Kirchhoff transformation. Adv Water Resour 2004;27:775-84].
A Stochastic Differential Equation Approach To Multiphase Flow In Porous Media
NASA Astrophysics Data System (ADS)
Dean, D.; Russell, T.
2003-12-01
The motivation for using stochastic differential equations in multiphase flow systems stems from our work in developing an upscaling methodology for single phase flow. The long term goals of this project include: I. Extending this work to a nonlinear upscaling methodology II. Developing a macro-scale stochastic theory of multiphase flow and transport that accounts for micro-scale heterogeneities and interfaces. In this talk, we present a stochastic differential equation approach to multiphase flow, a typical example of which is flow in the unsaturated domain. Specifically, a two phase problem is studied which consists of a wetting phase and a non-wetting phase. The approach given results in a nonlinear stochastic differential equation describing the position of the non-wetting phase fluid particle. Our fundamental assumption is that the flow of fluid particles is described by a stochastic process and that the positions of the fluid particles over time are governed by the law of the process. It is this law which we seek to determine. The nonlinearity in the stochastic differential equation arises because both the drift and diffusion coefficients depend on the volumetric fraction of the phase which in turn depends on the position of the fluid particles in the experimental domain. The concept of a fluid particle is central to the development of the model described in this talk. Expressions for both saturation and volumetric fraction are developed using the fluid particle concept. Darcy's law and the continuity equation are then used to derive a Fokker-Planck equation using these expressions. The Ito calculus is then applied to derive a stochastic differential equation for the non-wetting phase. This equation has both drift and diffusion terms which depend on the volumetric fraction of the non-wetting phase. Standard stochastic theories based on the Ito calculus and the Wiener process and the equivalent Fokker-Planck PDE's are typically used to model dispersion
A scenario neutral approach to assess low flow sensitivity to climate change
NASA Astrophysics Data System (ADS)
Sauquet, Eric; Prudhomme, Christel
2015-04-01
Most impact studies of climate change on river flow regime are performed following top-down approaches, where changes in hydrological characteristics are obtained from rainfall-runoff models forced by downscaled projections provided by GCMs. However, such approaches are not always considered robust enough to bridge the gap between climate research and stake holders needs to develop relevant adaptation strategy (Wilby et al., 2014). Alternatively, 'bottom-up' approaches can be applied to climate change impact studies on water resources to assess the intrinsic vulnerability of the catchments and ultimately help to prioritize adaptation actions for areas highly sensitive to small deviations from the present-day climate conditions. A general framework combining the scenario-neutral methodology developed by Prudhomme et al. (2010) and climate elasticity analyses (Sankarasubramanian et al., 2001) is presented and applied to measure the vulnerability of low flows and droughts on a large dataset of more than 400 French gauged basins. The different steps involved in the suggested framework are: - Calibration of the GR5J rainfall runoff model (Pushpalatha et al., 2011) against observations, - Identification of the main climate factors influencing low flows, - Definition of the sensitivity domain for precipitation (P), temperature (T) and potential evapotranspiration (PE) scenarios consistent with most recent climate change projections, - Derivation of the response surface describing changes in low flow and drought regime in terms of severity, duration and seasonality (Catalogne, 2012), - Uncertainty assessment. Results are the basis for a classification of river basins according to their sensitivity at national scale and for discussions on adaptation requirements with stakeholders. Catalogne C (2012) Amélioration des méthodes de prédétermination des débits de référence d'étiage en sites peu ou pas jaugés. PHD thesis, Université Joseph Fourier, Grenoble, 285 pp
An Aerial-Image Dense Matching Approach Based on Optical Flow Field
NASA Astrophysics Data System (ADS)
Yuan, Wei; Chen, Shiyu; Zhang, Yong; Gong, Jianya; Shibasaki, Ryosuke
2016-06-01
Dense matching plays an important role in many fields, such as DEM (digital evaluation model) producing, robot navigation and 3D environment reconstruction. Traditional approaches may meet the demand of accuracy. But the calculation time and out puts density is hardly be accepted. Focus on the matching efficiency and complex terrain surface matching feasibility an aerial image dense matching method based on optical flow field is proposed in this paper. First, some high accurate and uniformed control points are extracted by using the feature based matching method. Then the optical flow is calculated by using these control points, so as to determine the similar region between two images. Second, the optical flow field is interpolated by using the multi-level B-spline interpolation in the similar region and accomplished the pixel by pixel coarse matching. Final, the results related to the coarse matching refinement based on the combined constraint, which recognizes the same points between images. The experimental results have shown that our method can achieve per-pixel dense matching points, the matching accuracy achieves sub-pixel level, and fully meet the three-dimensional reconstruction and automatic generation of DSM-intensive matching's requirements. The comparison experiments demonstrated that our approach's matching efficiency is higher than semi-global matching (SGM) and Patch-based multi-view stereo matching (PMVS) which verifies the feasibility and effectiveness of the algorithm.
Molecule-based approach for computing chemical-reaction rates in upper atmosphere hypersonic flows.
Gallis, Michail A.; Bond, Ryan Bomar; Torczynski, John Robert
2009-08-01
This report summarizes the work completed during FY2009 for the LDRD project 09-1332 'Molecule-Based Approach for Computing Chemical-Reaction Rates in Upper-Atmosphere Hypersonic Flows'. The goal of this project was to apply a recently proposed approach for the Direct Simulation Monte Carlo (DSMC) method to calculate chemical-reaction rates for high-temperature atmospheric species. The new DSMC model reproduces measured equilibrium reaction rates without using any macroscopic reaction-rate information. Since it uses only molecular properties, the new model is inherently able to predict reaction rates for arbitrary nonequilibrium conditions. DSMC non-equilibrium reaction rates are compared to Park's phenomenological non-equilibrium reaction-rate model, the predominant model for hypersonic-flow-field calculations. For near-equilibrium conditions, Park's model is in good agreement with the DSMC-calculated reaction rates. For far-from-equilibrium conditions, corresponding to a typical shock layer, the difference between the two models can exceed 10 orders of magnitude. The DSMC predictions are also found to be in very good agreement with measured and calculated non-equilibrium reaction rates. Extensions of the model to reactions typically found in combustion flows and ionizing reactions are also found to be in very good agreement with available measurements, offering strong evidence that this is a viable and reliable technique to predict chemical reaction rates.
NASA Astrophysics Data System (ADS)
Del Ventisette, C.; Garfagnoli, F.; Ciampalini, A.; Battistini, A.; Gigli, G.; Moretti, S.; Casagli, N.
2012-09-01
On 1 October 2009, a prolonged and intense rainstorm triggered hundreds of landslides (predominantly debris flows) in an area of about 50 km2 in the north-eastern sector of Sicily (Italy). Debris flows swept the highest parts of many villages and passed over the SS114 state highway and the Messina-Catania railway, causing more than 30 fatalities. This region has a high relief, due to recent uplift. The peculiar geological and geomorphological framework represents one of the most common predisposing causes of rainstorm-triggered debris flows. This paper deals with the geological and hydro-geomorphological studies performed as a part of the post-disaster activities operated in collaboration with Civil Protection Authority, with the aim at examining landslides effects and mechanisms. The data were elaborated into a GIS platform, to evaluate the influence of urbanisation on the drainage pattern, and were correlated with the lithological and structural framework of the area. Our study points at the evaluation of the volume involved, the detection of triggering mechanisms and the precise reconstruction of the influence of urbanisation as fundamental tools for understanding the dynamics of catastrophic landslides. This kind of analysis, including all the desirable approaches for the correct management of debris flow should be the starting point for robust urban planning.
Exact Solutions for Stokes' Flow of a Non-Newtonian Nanofluid Model: A Lie Similarity Approach
NASA Astrophysics Data System (ADS)
Aziz, Taha; Aziz, A.; Khalique, C. M.
2016-07-01
The fully developed time-dependent flow of an incompressible, thermodynamically compatible non-Newtonian third-grade nanofluid is investigated. The classical Stokes model is considered in which the flow is generated due to the motion of the plate in its own plane with an impulsive velocity. The Lie symmetry approach is utilised to convert the governing nonlinear partial differential equation into different linear and nonlinear ordinary differential equations. The reduced ordinary differential equations are then solved by using the compatibility and generalised group method. Exact solutions for the model equation are deduced in the form of closed-form exponential functions which are not available in the literature before. In addition, we also derived the conservation laws associated with the governing model. Finally, the physical features of the pertinent parameters are discussed in detail through several graphs.
Ababou, R.
1991-08-01
This report develops a broad review and assessment of quantitative modeling approaches and data requirements for large-scale subsurface flow in radioactive waste geologic repository. The data review includes discussions of controlled field experiments, existing contamination sites, and site-specific hydrogeologic conditions at Yucca Mountain. Local-scale constitutive models for the unsaturated hydrodynamic properties of geologic media are analyzed, with particular emphasis on the effect of structural characteristics of the medium. The report further reviews and analyzes large-scale hydrogeologic spatial variability from aquifer data, unsaturated soil data, and fracture network data gathered from the literature. Finally, various modeling strategies toward large-scale flow simulations are assessed, including direct high-resolution simulation, and coarse-scale simulation based on auxiliary hydrodynamic models such as single equivalent continuum and dual-porosity continuum. The roles of anisotropy, fracturing, and broad-band spatial variability are emphasized. 252 refs.
Assessing material flows in urban systems: an approach to maximize the use of incomplete data sets.
Espinosa, G; Otterpohl, R
2014-01-01
Data scarcity and uncertainty are the main limiting factors for an integral evaluation of the urban water and wastewater management system (WWMS) in developing countries. The present research shows an approach to use incomplete data sets to analyse the flows of water and nitrogen and to make an integral evaluation of the WWMS at a case study city. By means of data validation and model adaptations the use of literature values is kept at the minimum possible and so the current trends for water consumption and pollution in the city are identified. The material flows were calculated as central values with a certain confidence range and met the selected plausibility criteria. Thus, the first essential step needed to identify the challenges and opportunities of future improvement strategies at the WWMS of the city was possible. PMID:25259505
Bandiera, Glen; Gaunt, Karen; Sinclair, Douglas; Trafford, Anne
2014-01-01
Emergency department (ED) overcrowding and long wait times are major concerns in health systems the world over. Many ED-focused innovations--such as revising staff mix, improving internal processes and exploiting decision-support software--have been implemented to address these complex problems, often with limited success. Beginning in 2008, St. Michael's Hospital in Toronto, which had some of the most challenging ED overcrowding and longest wait times in Ontario, has charted a different course. By taking an organization-wide corporate approach to the challenge of patient flow throughout the hospital, St. Michael's has significantly improved key ED flow metrics for both its admitted and non-admitted patients. PMID:25906463
Strongly coupled partitioned approach for fluid structure interaction in free surface flows
NASA Astrophysics Data System (ADS)
Facci, Andrea Luigi; Ubertini, Stefano
2016-06-01
In this paper we describe and validate a methodology for the numerical simulation of the fluid structure interaction in free surface flows. Specifically, this study concentrates on the vertical impact of a rigid body on the water surface, (i.e. on the hull slamming problem). The fluid flow is modeled through the volume of fluid methodology, and the structure dynamics is described by the Newton's second law. An iterative algorithm guarantees the tight coupling between the fluid and solid solvers, allowing the simulations of lightweight (i.e. buoyant) structures. The methodology is validated comparing numerical results to experimental data on the free fall of different rigid wedges. The correspondence between numerical results and independent experimental findings from literature evidences the reliability and the accuracy of the proposed approach.
Numerical solution of transonic wing flows using an Euler/Navier-Stokes zonal approach
NASA Technical Reports Server (NTRS)
Holst, T. L.; Gundy, K. L.; Thomas, S. D.; Chaderjian, N. M.; Flores, J.
1985-01-01
Transonic flow fields about wing geometries are computed using an Euler/Navier-Stokes approach in which the flow field is divided into several zones. The grid zones immediately adjacent to the wing surface are suitably clustered and solved with the Navier-Stokes equations. Grid zones removed from the wing are less finely clustered and are solved with the Euler equations. Wind tunnel wall effects are easily and accurately modeled with the new grid-zoning algorithm because the wind tunnel grid is constructed as an exact subset of the corresponding free-air grid. Solutions are obtained that are in good agreement with experiment, including cases with significant wind tunnel wall effects and shock-induced separation on the upper wing surface.
Application of the mobility power flow approach to structural response from distributed loading
NASA Technical Reports Server (NTRS)
Cuschieri, J. M.
1988-01-01
The problem of the vibration power flow through coupled substructures when one of the substructures is subjected to a distributed load is addressed. In all the work performed thus far, point force excitation was considered. However, in the case of the excitation of an aircraft fuselage, distributed loading on the whole surface of a panel can be as important as the excitation from directly applied forces at defined locations on the structures. Thus using a mobility power flow approach, expressions are developed for the transmission of vibrational power between two coupled plate substructures in an L configuration, with one of the surfaces of one of the plate substructures being subjected to a distributed load. The types of distributed loads that are considered are a force load with an arbitrary function in space and a distributed load similar to that from acoustic excitation.
Computation of transonic separated wing flows using an Euler/Navier-Stokes zonal approach
NASA Technical Reports Server (NTRS)
Kaynak, Uenver; Holst, Terry L.; Cantwell, Brian J.
1986-01-01
A computer program called Transonic Navier Stokes (TNS) has been developed which solves the Euler/Navier-Stokes equations around wings using a zonal grid approach. In the present zonal scheme, the physical domain of interest is divided into several subdomains called zones and the governing equations are solved interactively. The advantages of the Zonal Grid approach are as follows: (1) the grid for any subdomain can be generated easily; (2) grids can be, in a sense, adapted to the solution; (3) different equation sets can be used in different zones; and, (4) this approach allows for a convenient data base organization scheme. Using this code, separated flows on a NACA 0012 section wing and on the NASA Ames WING C have been computed. First, the effects of turbulence and artificial dissipation models incorporated into the code are assessed by comparing the TNS results with other CFD codes and experiments. Then a series of flow cases is described where data are available. The computed results, including cases with shock-induced separation, are in good agreement with experimental data. Finally, some futuristic cases are presented to demonstrate the abilities of the code for massively separated cases which do not have experimental data.
Solving Stochastic Flexible Flow Shop Scheduling Problems with a Decomposition-Based Approach
NASA Astrophysics Data System (ADS)
Wang, K.; Choi, S. H.
2010-06-01
Real manufacturing is dynamic and tends to suffer a lot of uncertainties. Research on production scheduling under uncertainty has recently received much attention. Although various approaches have been developed for scheduling under uncertainty, this problem is still difficult to tackle by any single approach, because of its inherent difficulties. This chapter describes a decomposition-based approach (DBA) for makespan minimisation of a flexible flow shop (FFS) scheduling problem with stochastic processing times. The DBA decomposes an FFS into several machine clusters which can be solved more easily by different approaches. A neighbouring K-means clustering algorithm is developed to firstly group the machines of an FFS into an appropriate number of machine clusters, based on a weighted cluster validity index. A back propagation network (BPN) is then adopted to assign either the Shortest Processing Time (SPT) Algorithm or the Genetic Algorithm (GA) to generate a sub-schedule for each machine cluster. After machine grouping and approach assignment, an overall schedule is generated by integrating the sub-schedules of the machine clusters. Computation results reveal that the DBA is superior to SPT and GA alone for FFS scheduling under stochastic processing times, and that it can be easily adapted to schedule FFS under other uncertainties.
NASA Astrophysics Data System (ADS)
Gerke, K.
2012-04-01
Most dye staining experiments in natural soils result in highly heterogeneous flow patterns which are usually explained with presence of preferential flow paths or different kinds of flow instabilities. It is quite logic that soil structure is one of the main factors affecting infiltrations regimes, however the degree of flow stochasticity is not studied enough. In this contribution a substantial amount of large scale (2-4 m lateral excavations) field experiment data is considered (including forested hillslopes and agricultural fields) with special attention to sprinkling of two different staining substances with different dyeing mechanisms (common dye is visible both in adsorbed and in solution states; fluorescent dye - only in solution). The latter method allows an estimation of the flow stability (stochasticity). Most staining field experiments are supported by undisturbed sample collections (laboratory measurements for hydraulic conductivity, water retention curves, X-ray microtomography scans, grain size distributions, etc.). Preliminary results strongly support the evidence of stability of flow under similar precipitation and moisture conditions. Infiltration also correlated with soil structure and microproperties. Numerical modeling using classical approach (single-porosity coupled Richard's and advection-dispersion equations, random hydraulic properties based on log-normal experimentally obtained distribution) fails to describe experimentally obtained staining patterns. Multi-porosity models may provide better tools to account for different soil heterogeneities, but their parameters can not be obtained experimentally. Small scale solutions using pore-network or lattice-Botzmann methods based on microtomography scans are accurate, but computationally expensive (volumes around tens of cm3). Based on field observations a simple cellular automata approach to model staining patterns is developed and tested on experimental data. Our results are much better then
Quantification of non-stormwater flow entries into storm drains using a water balance approach.
Xu, Zuxin; Yin, Hailong; Li, Huaizheng
2014-07-15
To make decisions about correcting illicit or inappropriate connections to storm drains, quantification of non-stormwater entries into storm drains was performed using a water flow balance approach, based on data analysis from 2008 to 2011 in a separate storm drainage system in a Shanghai downtown area of 374 ha. The study revealed severe sewage connections to storm drains; meanwhile, misconnections between surface water and storm drains were found to drive frequent non-stormwater pumping discharges at the outfall, producing a much larger volume of outfall flows in a short period. This paper presented a methodology to estimate quantities of inappropriate sewage flow, groundwater infiltration and river water backflow into the storm drains. It was concluded that inappropriate sewage discharge and groundwater seepage into storm drains were approximately 17,860 m(3)/d (i.e., up to 51% of the total sewage flow in the catchment) and 3,624 m(3)/d, respectively, and surface water backflow was up to an average 28,593 m(3)/d. On the basis of this work, end-of-storm pipe interceptor sewers of 0.25 m(3)/s (i.e., 21,600 m(3)/d) would be effective to tackle the problem of sewage connections and groundwater seepage to storm drains. Under this circumstance, the follow-up non-stormwater outfall pumping events indicate misconnections between surface water and storm drains, featuring pumping discharge equivalent to surface water backflow; hence the misconnections should be repaired. The information provided here is helpful in estimating the magnitude of non-stormwater flow entries into storm drains and designing the necessary pollution control activities, as well as combating city floods in storm events. PMID:24793842
NASA Technical Reports Server (NTRS)
Gupta, R. N.; Rodkiewicz, C. M.
1975-01-01
The numerical results are obtained for heat transfer, skin-friction, and viscous interaction induced pressure for a step-wise accelerated flat plate in hypersonic flow. In the unified approach here the results are presented for both weak and strong-interaction problems without employing any linearization scheme. With the help of the numerical method used in this work an accurate prediction of wall shear can be made for the problems with plate velocity changes of 1% or larger. The obtained results indicate that the transient contribution to the induced pressure for helium is greater than that for air.
A Multiblock Approach for Calculating Incompressible Fluid Flows on Unstructured Grids
NASA Technical Reports Server (NTRS)
Sheng, Chunhua; Whitfield, David L.; Anderson, W. Kyle
1997-01-01
A multiblock approach is presented for solving two-dimensional incompressible turbulent flows on unstructured grids. The artificial compressibility form of the governing equations is solved by a vertex-centered, finite-volume implicit scheme which uses a backward Euler time discretization. Point Gauss-Seidel relaxations are used to solve the linear system of equations at each time step. This work introduces a multiblock strategy to the solution procedure, which greatly improves the efficiency of the algorithm by significantly reducing the memory requirements while not increasing the CPU time. Results presented in this work shows that the current multiblock algorithm requires 70% less memory than the single block algorithm.
Computing 3-D steady supersonic flow via a new Lagrangian approach
NASA Technical Reports Server (NTRS)
Loh, C. Y.; Liou, M.-S.
1993-01-01
The new Lagrangian method introduced by Loh and Hui (1990) is extended for 3-D steady supersonic flow computation. Details of the conservation form, the implementation of the local Riemann solver, and the Godunov and the high resolution TVD schemes are presented. The new approach is robust yet accurate, capable of handling complicated geometry and reactions between discontinuous waves. It keeps all the advantages claimed in the 2-D method of Loh and Hui, e.g., crisp resolution for a slip surface (contact discontinuity) and automatic grid generation along the stream.
NASA Astrophysics Data System (ADS)
Gray, William G.; Miller, Cass T.
2006-11-01
This work is the third in a series of papers on the thermodynamically constrained averaging theory (TCAT) approach to modeling flow and transport phenomena in multiscale porous medium systems. Building upon the general TCAT framework and the mathematical foundation presented in previous works in this series, we demonstrate the TCAT approach for the case of single-fluid-phase flow. The formulated model is based upon conservation equations for mass, momentum, and energy and a general entropy inequality constraint, which is developed to guide model closure. A specific example of a closed model is derived under limiting assumptions using a linearization approach and these results are compared and contrasted with the traditional single-phase-flow model. Potential extensions to this work are discussed. Specific advancements in this work beyond previous averaging theory approaches to single-phase flow include use of macroscale thermodynamics that is averaged from the microscale, the use of derived equilibrium conditions to guide a flux-force pair approach to simplification, use of a general Lagrange multiplier approach to connect conservation equation constraints to the entropy inequality, and a focus on producing complete, closed models that are solvable.
NASA Astrophysics Data System (ADS)
Yadav, B. K.; Tomar, J.; Harter, T.
2014-12-01
We investigate nitrate movement from non-point sources in deep, heterogeneous vadose zones, using multi-dimensional variably saturated flow and transport simulations. We hypothesize that porous media heterogeneity causes saturation variability that leads to preferential flow systems such that a significant portion of the vadose zone does not significantly contribute to flow. We solve Richards' equation and the advection-dispersion equation to simulate soil moisture and nitrate transport regimes in plot-scale experiments conducted in the San Joaquin Valley, California. We compare equilibrium against non-equilibrium (dual-porosity) approaches. In the equilibrium approach we consider each soil layer to have unique hydraulic properties as a whole, while in the dual-porosity approach we assume that large fractions of the porous flow domain are immobile. However we consider exchange of water and solute between mobile and immobile zone using the appropriate mass transfer terms. The results indicate that flow and transport in a nearly 16 m deep stratified vadose zone comprised of eight layers of unconsolidated alluvium experiences highly non-uniform, localized preferential flow and transport patterns leading to accelerated nitrate transfer. The equilibrium approach largely under-predicted the leaching of nitrate to groundwater while the dual-porosity approach showed higher rates of nitrate leaching, consistent with field observations. The dual-porosity approach slightly over-predicted nitrogen storage in the vadose zone, which may be the result of limited matrix flow or denitrification not accounted for in the model. Results of this study may be helpful to better predict fertilizer and pesticide retention times in deep vadose zone, prior to recharge into the groundwater flow system. Keywords: Nitrate, Preferential flow, Heterogeneous vadose zone, Dual-porosity approach
Horizontal annular flow modelling using a compositional based interface capturing approach
NASA Astrophysics Data System (ADS)
Pavlidis, Dimitrios; Xie, Zhizhua; Percival, James; Gomes, Jefferson; Pain, Chris; Matar, Omar
2014-11-01
Progress on a consistent approach for interface-capturing in which each component represents a different phase/fluid is described. The aim is to develop a general multi-phase modelling approach based on fully-unstructured meshes that can exploit the latest mesh adaptivity methods, and in which each fluid phase may have a number of components. The method is compared against experimental results for a collapsing water column test case and a convergence study is performed. A number of numerical test cases are undertaken to demonstrate the method's ability to model arbitrary numbers of phases with arbitrary equations of state. The method is then used to simulate horizontal annular flows. EPSRC Programme Grant, MEMPHIS, EP/K0039761/1.
NASA Astrophysics Data System (ADS)
Han, Zheng; Chen, Guangqi; Li, Yange; Wang, Wei; Zhang, Hong
2015-07-01
The estimation of debris-flow velocity in a cross-section is of primary importance due to its correlation to impact force, run up and superelevation. However, previous methods sometimes neglect the observed asymmetric velocity distribution, and consequently underestimate the debris-flow velocity. This paper presents a new approach for exploring the debris-flow velocity distribution in a cross-section. The presented approach uses an iteration algorithm based on the Riemann integral method to search an approximate solution to the unknown flow surface. The established laws for vertical velocity profile are compared and subsequently integrated to analyze the velocity distribution in the cross-section. The major benefit of the presented approach is that natural channels typically with irregular beds and superelevations can be taken into account, and the resulting approximation by the approach well replicates the direct integral solution. The approach is programmed in MATLAB environment, and the code is open to the public. A well-documented debris-flow event in Sichuan Province, China, is used to demonstrate the presented approach. Results show that the solutions of the flow surface and the mean velocity well reproduce the investigated results. Discussion regarding the model sensitivity and the source of errors concludes the paper.
NASA Astrophysics Data System (ADS)
Wang, Mu; Brady, John
2015-11-01
We use Brownian dynamics to investigate the relation between the rheology and the microscopic particle dynamics in dense colloidal dispersions at constant stress and pressure. For each imposed stress/pressure pair, the suspension exhibits distinct strain rate distributions depending on the observation time. We measure the long-time self-diffusivity (LTSD) corresponding to the strain rate (inverse shear viscosity) and find that the LTSD results at different imposed stresses collapse to master curves that depends only on the imposed pressure. For low-pressure suspensions, the stress-scaled LTSD diverges at a finite scaled strain rate due to its liquid-like behavior, while at high pressures the scaled LTSD emerges from zero due to the flow-arrest transition. On the other hand, we discover that the particle friction coefficient--the ratio of the particle shear stress to the particle (osmotic) pressure--is proportional to the strain rate scaled by the LTSD for all flowing suspensions. Our results demonstrate the effectiveness of the constant stress and pressure approach for dense suspension rheology, and show that, although the flow of amorphous materials is inherently far-from-equilibrium without a linear response regime, a mean-field description should remain valid.
Runoff modelling using radar data and flow measurements in a stochastic state space approach.
Krämer, S; Grum, M; Verworn, H R; Redder, A
2005-01-01
In urban drainage the estimation of runoff with the help of models is a complex task. This is in part due to the fact that rainfall, the most important input to urban drainage modelling, is highly uncertain. Added to the uncertainty of rainfall is the complexity of performing accurate flow measurements. In terms of deterministic modelling techniques these are needed for calibration and evaluation of the applied model. Therefore, the uncertainties of rainfall and flow measurements have a severe impact on the model parameters and results. To overcome these problems a new methodology has been developed which is based on simple rain plane and runoff models that are incorporated into a stochastic state space model approach. The state estimation is done by using the extended Kalman filter in combination with a maximum likelihood criterion and an off-line optimization routine. This paper presents the results of this new methodology with respect to the combined consideration of uncertainties in distributed rainfall derived from radar data and uncertainties in measured flows in an urban catchment within the Emscher river basin, Germany. PMID:16248174
NASA Astrophysics Data System (ADS)
Dhir, Gaurav; Suman, Sawan
2015-11-01
Experimental evidence shows that aircrafts operating under heavy rainfall conditions face deterioration of lift and increase in drag. This scenario can be a critical design challenge especially for slow moving vehicles such as airships. Effective roughening of airfoil surface caused by an uneven water film, loss of flow momentum and the loss of vehicle momentum due to its collision with the raindrops are the primary reasons causing the drag to increase. Our work focuses primarily on the numerical quantification of boundary layer momentum loss caused due to raindrops. The collision of raindrops with a solid surface leads to formation of an ejecta fog of splashed back droplets with their sizes being of the order of micrometers and their acceleration leads to boundary layer momentum loss. We model the airflow within a flat plate boundary layer using a Lagrangian-Eulerian approach with the raindrops being considered as non-deformable, non-spinning and non-interacting droplets. We employ an inter-phase coupling term to account for the interaction between the boundary layer flow and the droplets. Our presentation will focus on several comparisons (velocity field, lift and drag at various angles of attack) with the results of the standard (rain-free) Prandtl boundary layer flow. Indian Institute of Technology, Delhi.
A Lagrangian approach to study flow topology around a flapping flat-plate wing
NASA Astrophysics Data System (ADS)
Krishna, Swathi; Mulleners, Karen; Green, Melissa
2015-11-01
The incredible flight performance of insects can be attributed in part to the generation and maintenance of stable regions of vorticity, which is achieved by manipulating the wing kinematics. Along with the prolonged attachment of the leading edge vortex during translation of the wing, the rotational motion at the end of the stroke is critical as it generates large amounts of lift required for the insect to remain air-borne while hovering. The wing reversal entails a change in the flow-field around the wing which is closely tied to variations in force production. Based on phase-averaged particle image velocimetry data we analyze the effect of a shift in the rotational phase of a flapping wing on the flow characteristics. A topological study is conducted using Lagrangian vortex detection techniques in order to characterize the shear layer formation, vortex interactions and flow separation. The Lagrangian analysis includes the calculation of Finite Time Lyapunov Exponents based on particle trajectories. An objective approach is employed to trace the location of separation or attachment points as an indication for changes in the strength, stability and shedding frequencies of vortices. These trajectories are correlated with fluctuations in aerodynamic force coefficients.
Solution-Adaptive Cartesian Cell Approach for Viscous and Inviscid Flows
NASA Technical Reports Server (NTRS)
Coirier, William J.; Powell, Kenneth G.
1996-01-01
A Cartesian cell-based approach for adaptively refined solutions of the Euler and Navier-Stokes equations in two dimensions is presented. Grids about geometrically complicated bodies are generated automatically, by the recursive subdivision of a single Cartesian cell encompassing the entire flow domain. Where the resulting cells intersect bodies, polygonal cut cells are created using modified polygon-clipping algorithms. The grid is stored in a binary tree data structure that provides a natural means of obtaining cell-to-cell connectivity and of carrying out solution-adaptive mesh refinement. The Euler and Navier-Stokes equations are solved on the resulting grids using a finite volume formulation. The convective terms are upwinded: A linear reconstruction of the primitive variables is performed, providing input states to an approximate Riemann solver for computing the fluxes between neighboring cells. The results of a study comparing the accuracy and positivity of two classes of cell-centered, viscous gradient reconstruction procedures is briefly summarized. Adaptively refined solutions of the Navier-Stokes equations are shown using the more robust of these gradient reconstruction procedures, where the results computed by the Cartesian approach are compared to theory, experiment, and other accepted computational results for a series of low and moderate Reynolds number flows.
A two-dimensional approach to modelling the short timescale zonal flow in Earth's core
NASA Astrophysics Data System (ADS)
More, C.; Dumberry, M.
2015-12-01
Reconstructions of flow in Earth's outer core based on surface magnetic data predict mean zonal accelerations on several timescales. Since accelerations in the core couple to the angular momentum of the mantle, their existence has been confirmed by length-of-day observations. Recent studies suggest that free modes of torsional oscillations are responsible for relatively weak signals with a 5-6 year period. The mechanisms responsible for stronger decadal signals are less well understood.To address the problem, we construct a quasi-geostrophic model of magnetoconvection, with thermally-driven flows perturbing a steady, imposed background magnetic field. This approach is justified by the Taylor-Proudman theorem, in which velocities in a rapidly rotating system vary little parallel to the rotational axis. Using only two dimensions allows a much more rapid exploration of parameter space than traditional three-dimensional approaches.Our model is capable of producing mean zonal accelerations similar to those predicted by the geomagnetic reconstructions of Earth. In particular, we see a clear separation in period between the free modes (short) and forced modes (long) of torsional oscillations. We then systematically run the model with a variety of parameters, attempting to extrapolate our results to the conditions found in Earth's core.
NASA Astrophysics Data System (ADS)
Meliga, Philippe; Chomaz, Jean-Marc; Gallaire, François
2011-07-01
This paper considers vortex-induced vibrations of a cylinder in water streams for renewable energy production. We use an analytical model recently obtained by the authors from the asymptotic analysis of a coupled flow-cylinder system, and assess the ability of a control velocity applied at the cylinder wall to optimize the magnitude of dissipated energy at disposal to be harvested. The retained approach is that of proportional feedback control. When the system evolves on its limit cycle, we show that the control yields an increase in the mean dissipated energy by 3.5%, as well as a significant improvement of the robustness with respect to small inaccuracies of the structural parameters. However, we also show that the system is susceptible to converge to cycles of lower energy when subjected to external disturbances, as a result of the simultaneous existence of multiple stable cycles. Consequently, we propose a transient control algorithm meant to force the return of the system to its optimal cycle. Its efficiency is assessed for two feedback approaches relying on distinct types of measurements: we find significant differences in the time needed to reach convergence to the optimal cycle, which ultimately results in energy being spent when feedback is designed from cylinder measurements, and in energy being harnessed when feedback is designed from flow measurements.
Directed flow in heavy-ion collisions from the PHSD transport approach
NASA Astrophysics Data System (ADS)
Palmese, A.; Cassing, W.
2016-01-01
Recent STAR data for the directed flow of protons, antiprotons, charged pions and kaons obtained within the beam energy scan (BES) program are analyzed within the Parton- Hadron-String-Dynamics (PHSD/HSD) transport models. Both versions of the kinetic approach are used to clarify the role of partonic degrees of freedom. The PHSD results, simulating a partonic phase and its coexistence with a hadronic one, are roughly consistent with the STAR data. Generally, the semi-qualitative agreement between the measured data and model results supports the idea of a crossover type of quark-hadron transition which softens the nuclear EoS but shows no indication of a first-order phase transition. Furthermore, the directed flow of kaons and antikaons is evaluated in the PHSD approach from √sNN ≈ 5-12 GeV which shows a high sensitivity to the hadronic potentials in the FAIR/NICA energy regime √sNN ≤⃒ 8 GeV.
Water flow modeling in the unsaturated zone with imprecise parameters using a fuzzy approach
NASA Astrophysics Data System (ADS)
Schulz, K.; Huwe, B.
1997-12-01
An alternative approach, based on fuzzy set theory, is presented to express imprecision of parameters in a non-probabilistic sense. Imprecision may originate from indirect measurements, estimation routines, subjective interpretation and expert judgement of available information. One dimensional, steady state water flow in the unsaturated zone of homogeneous soils, which is described by the Darcy-Buckingham equation, was chosen to evaluate and to incorporate fuzzy soil hydraulic properties and boundary conditions in the modeling procedure. It is here used to describe soil water pressures with depth, as well as to calculate maximum evapotranspiration rates under steady state conditions. Solving the fuzzy equation for steady state water flow results in minimizing/maximizing procedures, from where resulting membership functions of the dependent variable are calculated. A comparison to a more classical stochastic approach points out the main differences between fuzzy and stochastic concepts to account for uncertainties. Finally, a sensitivity analysis shows the strong impact of different shapes of membership functions of the input parameters on the resulting membership functions of maximum evapotranspiration rates and soil water pressures.
NASA Astrophysics Data System (ADS)
Severino, Gerardo; de Bartolo, Samuele; Toraldo, Gerardo; Srinivasan, Gowri; Viswanathan, Hari
2012-12-01
Diverging radial flow takes place in a heterogeneous porous medium where the log conductivity Y = ln K is modeled as a stationary random space function (RSF). The flow is steady, and is generated by a fully penetrating well. A linearly sorbing solute is injected through the well envelope, and we aim at computing the average flux concentration (breakthrough curve). A relatively simple solution for this difficult problem is achieved by adopting, similar to Indelman and Dagan (1999), a few simplifying assumptions: (i) a thick aquifer of large horizontal extent, (ii) mildly heterogeneous medium, (iii) strongly anisotropic formation, and (iv) large Peclet number. By introducing an appropriate Lagrangian framework, three-dimensional transport is mapped onto a one-dimensional domain (τ, t) where τ and t represent the fluid travel and current time, respectively. Central for this approach is the probability density function of the RSF τthat is derived consistently with the adopted assumptions stated above. Based on this, it is shown that the travel time can be regarded as a Gaussian random variable only in the far field. The breakthrough curves are analyzed to assess the impact of the hydraulic as well as reactive parameters. Finally, the travel time approach is tested against a forced-gradient transport experiment and shows good agreement.
An adaptive level set approach for incompressible two-phase flows
Sussman, M.; Almgren, A.S.; Bell, J.B.
1997-04-01
In Sussman, Smereka and Osher, a numerical method using the level set approach was formulated for solving incompressible two-phase flow with surface tension. In the level set approach, the interface is represented as the zero level set of a smooth function; this has the effect of replacing the advection of density, which has steep gradients at the interface, with the advection of the level set function, which is smooth. In addition, the interface can merge or break up with no special treatment. The authors maintain the level set function as the signed distance from the interface in order to robustly compute flows with high density ratios and stiff surface tension effects. In this work, they couple the level set scheme to an adaptive projection method for the incompressible Navier-Stokes equations, in order to achieve higher resolution of the interface with a minimum of additional expense. They present two-dimensional axisymmetric and fully three-dimensional results of air bubble and water drop computations.
NASA Astrophysics Data System (ADS)
Shyue, Keh-Ming; Xiao, Feng
2014-07-01
We describe a novel interface-sharpening approach for efficient numerical resolution of a compressible homogeneous two-phase flow governed by a quasi-conservative five-equation model of Allaire et al. (2001) [1]. The algorithm uses a semi-discrete wave propagation method to find approximate solution of this model numerically. In the algorithm, in regions near the interfaces where two different fluid components are present within a cell, the THINC (Tangent of Hyperbola for INterface Capturing) scheme is used as a basis for the reconstruction of a sub-grid discontinuity of volume fractions at each cell edge, and it is complemented by a homogeneous-equilibrium-consistent technique that is derived to ensure a consistent modeling of the other interpolated physical variables in the model. In regions away from the interfaces where the flow is single phase, standard reconstruction scheme such as MUSCL or WENO can be used for obtaining high-order interpolated states. These reconstructions are then used as the initial data for Riemann problems, and the resulting fluctuations form the basis for the spatial discretization. Time integration of the algorithm is done by employing a strong stability-preserving Runge-Kutta method. Numerical results are shown for sample problems with the Mie-Grüneisen equation of state for characterizing the materials of interests in both one and two space dimensions that demonstrate the feasibility of the proposed method for interface-sharpening of compressible two-phase flow. To demonstrate the competitiveness of our approach, we have also included results obtained using the anti-diffusion interface sharpening method.
NASA Astrophysics Data System (ADS)
Perona, P.; Burlando, P.
2009-12-01
Environmental flows can result from the economical competition for water allocation between traditional and non-traditional water uses. This requires the definition of convenient benefit functions (bf) associated with the use of the resource. Since the use of water by the riparian ecosystem is an intangible good, common ways based for instance on the “willingness to pay” have the dramatic weakness of not being objective with regard to the environmental rights. That is, water withdrawal from a given stream environment would depend on the importance and, in turn, on the economical value that people assign to this environment. In this work we discuss a possible objective criterion to establish benefit functions for the environmental uses of the water resource. Our approach is based on studying the optimal water allocation between the users as resulting from marginal economic analysis. That is, we show that the parameters of the marginal demand curve for the riparian ecosystem are intrinsically defined by knowing: (a) the ecological status of the riverine system in pristine conditions, and (b) the marginal benefit function of the potential competitor (e.g., exploitation activity). We solve analytically the water allocation problem for the simple case of water withdrawal from a fluvial system. We show the link between the parameters of the marginal benefit functions and the minimal environmental flow arising from classic engineering analysis, as well as their ecological meaning. This approach allows to restore a more natural variability of the streamflow regime in impounded reaches, to the cost of a profit reduction for the resource exploitation. However, on the long term, the overall idea is that the benefit for having preserved more natural environmental flow conditions since exploitation began would balance the future cost for potential restoration of the riverine corridor and the missing revenues.
A Simplified Approach to Modeling Two-phase Flow of Seawater Near a Dike
NASA Astrophysics Data System (ADS)
Lewis, K.; Lowell, R. P.
2001-12-01
Magmatic dikes represent the fundamental unit of mass accretion and heat input into the oceanic crust. Dikes also drive hydrothermal circulation that may result in event plumes, but in any case the circulation will carry a pulse of mineral-laden hydrothermal fluids and heat to the seafloor. Two-phase flow and phase segregation are important aspects of hydrothermal circulation following dike emplacement. These processes are confined to narrow regions near the dike margins, and the duration of two-phase flow is brief. Nevertheless, sampling of hydrothermal fluids following dike emplacement has shown the early appearance of low chlorinity vapor phase fluids followed, in some cases (e.g., "F" vent at EPR 9° N), by the appearance of brines. We provide a simplified treatment of two-phase flow of seawater near a dike in an effort to quantify the thickness and duration of the two-phase zone, the amount of brine formed, and its distribution in the subsurface. We first estimate these parameters by considering simple conductive cooling of the dike. This approach shows that for a two-meter wide dike, the width of the two-phase zone is approximately 15 cm and that a zone of halite is deposited near the dike wall. After 10 days, the two-phase zone has disappeared at the base of the dike, and disappears everywhere else after about 15 days. We then use a simplified buoyancy driven convection model to quantify the degree of phase segregation and the distribution of brine. The results of this simplified model are compared with data from "F" vent. This approach provides semi-quantitative and conceptual constraints on numerical models for two-phase convection in NaCl-H2O fluids.
A dual-permeability approach to preferential water flow and solute transport in shrinking soils
NASA Astrophysics Data System (ADS)
Coppola, Antonio; dragonetti, giovanna; Comegna, Alessandro; Gerke, Horst H.; Basile, Angelo
2016-04-01
The pore systems in most natural soils is dynamically changing due to alternating swelling and shrinkage processes, which induces changes in pore volume and pore size distribution including deformations in pore geometry. This is a serious difficulty for modeling flow and transport in dual permeability approaches, as it will also require that the geometrical deformation of both the soil matrix and the fracture porous systems be taken into account, as well as the dynamics of soil hydraulic properties in response to the domain deformations. This study follows up a previous work by the same authors extending the classical rigid (RGD) approach formerly proposed by Gerke and van Genuchten, to account for shrinking effects (SHR) in modeling water flow and solute transport in dual-permeability porous media. In this study we considered three SHR scenarios, assuming that aggregate shrinkage may change either: (i) the hydraulic properties of the two pore domains, (ii) their relative fractions, and (iii) both, hydraulic properties and fractions of the two domains. The objective was to compare simulation results obtained under the RGD and the SHR assumptions to illustrate the impact of matrix volume changes on water storage, water fluxes and solute concentrations during: 1) An infiltration process bringing an initially dry soil to saturation, 2) A drainage process starting from an initially saturated soil. For an infiltration process, the simulated wetting front and the solute concentration propagation velocity, as well as the water fluxes, water and solute exchange rates, for the three SHR scenarios significantly deviated from the RGD. By contrast, relatively similar water content profiles evolved under all scenarios during drying. Overall, compared to the RGD approach, the effect of changing the hydraulic properties and the weight of the two domains according to the shrinkage behavior of the soil aggregates induced a much more rapid response in terms of water fluxes and
NASA Astrophysics Data System (ADS)
Yao, Weigang; Liou, Meng-Sing
2016-08-01
To preserve nonlinearity of a full-order system over a range of parameters of interest, we propose an accurate and robust nonlinear modeling approach by assembling a set of piecewise linear local solutions expanded about some sampling states. The work by Rewienski and White [1] on micromachined devices inspired our use of piecewise linear local solutions to study nonlinear unsteady aerodynamics. These local approximations are assembled via nonlinear weights of radial basis functions. The efficacy of the proposed procedure is validated for a two-dimensional airfoil moving with different pitching motions, specifically AGARD's CT2 and CT5 problems [27], in which the flows exhibit different nonlinear behaviors. Furthermore, application of the developed aerodynamic model to a two-dimensional aero-elastic system proves the approach is capable of predicting limit cycle oscillations (LCOs) by using AGARD's CT6 [28] as a benchmark test. All results, based on inviscid solutions, confirm that our nonlinear model is stable and accurate, against the full model solutions and measurements, and for predicting not only aerodynamic forces but also detailed flowfields. Moreover, the model is robust for inputs that considerably depart from the base trajectory in form and magnitude. This modeling provides a very efficient way for predicting unsteady flowfields with varying parameters because it needs only a tiny fraction of the cost of a full-order modeling for each new condition-the more cases studied, the more savings rendered. Hence, the present approach is especially useful for parametric studies, such as in the case of design optimization and exploration of flow phenomena.
NASA Astrophysics Data System (ADS)
Ozbek, M. M.; Pinder, G. F.
2006-12-01
There is a growing need in hydrologic and environmental modeling and management to segregate uncertainty, whether it occurs in input parameters or in possible alternative models, into aleatory uncertainty (i.e., irreducible or stochastic) and epistemic uncertainty (i.e., reducible or due to lack of knowledge). While aleatory uncertainty has been known and used as the only source of uncertainty in the hydrologic community for a long time, the notion of epistemic uncertainty is relatively new and it can be due several reasons including 1) field and laboratory methods used in the measurement of parameters, 2) techniques used to interpolate measured values at selected locations, and more importantly, 3) subjective expert opinion interpreting data available to augment existing prior parametric information. A natural framework to quantify epistemic uncertainty has been fuzzy set theory. In this paper, we use the extension principle of fuzzy set theory to simulate groundwater flow and transport with fuzzy model parameters. Our novel implementation of the principle involves two major steps: 1) a tessellation of the parameter space that results in simplexes over which the state variable is approximated by means of trial functions, followed by 2) the optimization of degrees of membership for the state variable in each simplex where the trial functions and the fuzzy parameter membership functions are used as the constraints of the optimization algorithm. We compare our approach to other known approaches to using the extension principle to address groundwater flow and transport in the saturated zone, and highlight features of our approach that apply to any physically based model with fuzzy parameter input.
ERIC Educational Resources Information Center
Cermakova, Lucie; Moneta, Giovanni B.; Spada, Marcantonio M.
2010-01-01
This study investigated how attentional control and study-related dispositional flow influence students' approaches to studying when preparing for academic examinations. Based on information-processing theories, it was hypothesised that attentional control would be positively associated with deep and strategic approaches to studying, and…
Cihan, Abdullah; Birkholzer, Jens; Trevisan, Luca; Bianchi, Marco; Zhou, Quanlin; Illangasekare, Tissa
2014-12-31
During CO_{2} injection and storage in deep reservoirs, the injected CO_{2} enters into an initially brine saturated porous medium, and after the injection stops, natural groundwater flow eventually displaces the injected mobile-phase CO_{2}, leaving behind residual non-wetting fluid. Accurate modeling of two-phase flow processes are needed for predicting fate and transport of injected CO_{2}, evaluating environmental risks and designing more effective storage schemes. The entrapped non-wetting fluid saturation is typically a function of the spatially varying maximum saturation at the end of injection. At the pore-scale, distribution of void sizes and connectivity of void space play a major role for the macroscopic hysteresis behavior and capillary entrapment of wetting and non-wetting fluids. This paper presents development of an approach based on the connectivity of void space for modeling hysteretic capillary pressure-saturation-relative permeability relationships. The new approach uses void-size distribution and a measure of void space connectivity to compute the hysteretic constitutive functions and to predict entrapped fluid phase saturations. Two functions, the drainage connectivity function and the wetting connectivity function, are introduced to characterize connectivity of fluids in void space during drainage and wetting processes. These functions can be estimated through pore-scale simulations in computer-generated porous media or from traditional experimental measurements of primary drainage and main wetting curves. The hysteresis model for saturation-capillary pressure is tested successfully by comparing the model-predicted residual saturation and scanning curves with actual data sets obtained from column experiments found in the literature. A numerical two-phase model simulator with the new hysteresis functions is tested against laboratory experiments conducted in a quasi-two-dimensional flow cell (91.4cm×5.6cm×61cm
Cihan, Abdullah; Birkholzer, Jens; Trevisan, Luca; Bianchi, Marco; Zhou, Quanlin; Illangasekare, Tissa
2014-12-31
During CO2 injection and storage in deep reservoirs, the injected CO2 enters into an initially brine saturated porous medium, and after the injection stops, natural groundwater flow eventually displaces the injected mobile-phase CO2, leaving behind residual non-wetting fluid. Accurate modeling of two-phase flow processes are needed for predicting fate and transport of injected CO2, evaluating environmental risks and designing more effective storage schemes. The entrapped non-wetting fluid saturation is typically a function of the spatially varying maximum saturation at the end of injection. At the pore-scale, distribution of void sizes and connectivity of void space play a major role formore » the macroscopic hysteresis behavior and capillary entrapment of wetting and non-wetting fluids. This paper presents development of an approach based on the connectivity of void space for modeling hysteretic capillary pressure-saturation-relative permeability relationships. The new approach uses void-size distribution and a measure of void space connectivity to compute the hysteretic constitutive functions and to predict entrapped fluid phase saturations. Two functions, the drainage connectivity function and the wetting connectivity function, are introduced to characterize connectivity of fluids in void space during drainage and wetting processes. These functions can be estimated through pore-scale simulations in computer-generated porous media or from traditional experimental measurements of primary drainage and main wetting curves. The hysteresis model for saturation-capillary pressure is tested successfully by comparing the model-predicted residual saturation and scanning curves with actual data sets obtained from column experiments found in the literature. A numerical two-phase model simulator with the new hysteresis functions is tested against laboratory experiments conducted in a quasi-two-dimensional flow cell (91.4cm×5.6cm×61cm), packed with homogeneous and
A theory-based approach to thermal field-flow fractionation of polyacrylates.
Runyon, J Ray; Williams, S Kim Ratanathanawongs
2011-09-28
A theory-based approach is presented for the development of thermal field-flow fractionation (ThFFF) of polyacrylates. The use of ThFFF for polymer analysis has been limited by an incomplete understanding of the thermal diffusion which plays an important role in retention and separation. Hence, a tedious trial-and-error approach to method development has been the normal practice when analyzing new materials. In this work, thermal diffusion theories based on temperature dependent osmotic pressure gradient and polymer-solvent interaction parameters were used to estimate thermal diffusion coefficients (D(T)) and retention times (t(r)) for different polymer-solvent pairs. These calculations identified methyl ethyl ketone as a solvent that would cause significant retention of poly(n-butyl acrylate) (PBA) and poly(methyl acrylate) (PMA). Experiments confirmed retention of these two polymers that have not been previously analyzed by ThFFF. Theoretical and experimental D(T)s and t(r)s for PBA, PMA, and polystyrene in different solvents agreed to within 20% and demonstrate the feasibility of this theory-based approach. PMID:21872869
An objective and parsimonious approach for classifying natural flow regimes at a continental scale
Archfield, Stacey A.; Kennen, Jonathan G.; Carlisle, Daren M.; Wolock, David M.
2014-01-01
Hydro-ecological stream classification-the process of grouping streams by similar hydrologic responses and, by extension, similar aquatic habitat-has been widely accepted and is considered by some to be one of the first steps towards developing ecological flow targets. A new classification of 1543 streamgauges in the contiguous USA is presented by use of a novel and parsimonious approach to understand similarity in ecological streamflow response. This novel classification approach uses seven fundamental daily streamflow statistics (FDSS) rather than winnowing down an uncorrelated subset from 200 or more ecologically relevant streamflow statistics (ERSS) commonly used in hydro-ecological classification studies. The results of this investigation demonstrate that the distributions of 33 tested ERSS are consistently different among the classification groups derived from the seven FDSS. It is further shown that classification based solely on the 33 ERSS generally does a poorer job in grouping similar streamgauges than the classification based on the seven FDSS. This new classification approach has the additional advantages of overcoming some of the subjectivity associated with the selection of the classification variables and provides a set of robust continental-scale classes of US streamgauges. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.
An efficient continuous flow approach to furnish furan-based biaryls.
Trinh, Trieu N; Hizartzidis, Lacey; Lin, Andrew J S; Harman, David G; McCluskey, Adam; Gordon, Christopher P
2014-12-21
Suzuki cross-couplings of 5-formyl-2-furanylboronic acid with activated or neutral aryl bromides were performed under continuous flow conditions in the presence of (Bu)4N(+)F(-) and the immobilised t-butyl based palladium catalyst CatCart™ FC1032™. Deactivated aryl bromides and activated aryl chlorides were cross-coupled with 5-formyl-2-furanylboronic in the presence of (Bu)4N(+)OAc(-) using the bis-triphenylphosphine CatCart™ PdCl2(PPh3)2-DVB. Initial evidence indicates the latter method may serve as a universal approach to conduct Suzuki cross-couplings with the protocol successfully employed in the synthesis of the current gold standard Hedgehog pathway inhibitor LDE225. PMID:25333944
A triple-continuum approach for modeling flow and transportprocesses in fractured rock
Wu, Yu-Shu; Liu, H.H.; Bodvarsson, G.S; Zellmer, K .E.
2001-08-31
This paper presents a triple-continuum conceptual model forsimulating flow and transport processes in fractured rock. Field datacollected from the unsaturated zone of Yucca Mountain, a repository siteof high-level nuclear waste, show a large number of small-scalefractures. The effect of these small fractures has not been considered inprevious modeling investigations within the context of a continuumapproach. A new triple-continuum model (consisting of matrix,small-fracture, and large-fracture continua) has been developed toinvestigate the effect of these small fractures. This paper derives themodel formulation and discusses the basic triple-continuum behavior offlow and transport processes under different conditions, using bothanalytical solutions and numerical approaches. The simulation resultsfrom the site-scale model of the unsaturated zone of Yucca Mountainindicate that these small fractures may have an important effect onradionuclide transport within the mountain
NASA Technical Reports Server (NTRS)
Egolf, T. A.; Landgrebe, A. J.
1982-01-01
A user's manual is provided which includes the technical approach for the Prescribed Wake Rotor Inflow and Flow Field Prediction Analysis. The analysis is used to provide the rotor wake induced velocities at the rotor blades for use in blade airloads and response analyses and to provide induced velocities at arbitrary field points such as at a tail surface. This analysis calculates the distribution of rotor wake induced velocities based on a prescribed wake model. Section operating conditions are prescribed from blade motion and controls determined by a separate blade response analysis. The analysis represents each blade by a segmented lifting line, and the rotor wake by discrete segmented trailing vortex filaments. Blade loading and circulation distributions are calculated based on blade element strip theory including the local induced velocity predicted by the numerical integration of the Biot-Savart Law applied to the vortex wake model.
Pina-Vaz, Cidália; Silva, Ana P; Faria-Ramos, Isabel; Teixeira-Santos, Rita; Moura, Daniel; Vieira, Tatiana F; Sousa, Sérgio F; Costa-de-Oliveira, Sofia; Cantón, Rafael; Rodrigues, Acácio G
2016-01-01
The synergy of carbapenem combinations regarding Enterobacteriaceae producing different types of carbapenemases was study through different approaches: flow cytometry and computational analysis. Ten well characterized Enterobacteriaceae (KPC, verona integron-encoded metallo-β-lactamases -VIM and OXA-48-like enzymes) were selected for the study. The cells were incubated with a combination of ertapenem with imipenem, meropenem, or doripenem and killing kinetic curves performed with and without reinforcements of the drugs. A cephalosporin was also used in combination with ertapenem. A flow cytometric assay with DiBAC4-(3), a membrane potential dye, was developed in order to evaluate the cellular lesion after 2 h incubation. A chemical computational study was performed to understand the affinity of the different drugs to the different types of enzymes. Flow cytometric analysis and time-kill assays showed a synergic effect against KPC and OXA-48 producing-bacteria with all combinations; only ertapenem with imipenem was synergic against VIM producing-bacteria. A bactericidal effect was observed in OXA-48-like enzymes. Ceftazidime plus ertapenem was synergic against ESBL-negative KPC producing-bacteria. Ertapenem had the highest affinity for those enzymes according to chemical computational study. The synergic effect between ertapenem and others carbapenems against different carbapenemase-producing bacteria, representing a therapeutic choice, was described for the first time. Easier and faster laboratorial methods for carbapenemase characterization are urgently needed. The design of an ertapenem derivative with similar affinity to carbapenemases but exhibiting more stable bonds was demonstrated as highly desirable. PMID:27555844
Pina-Vaz, Cidália; Silva, Ana P.; Faria-Ramos, Isabel; Teixeira-Santos, Rita; Moura, Daniel; Vieira, Tatiana F.; Sousa, Sérgio F.; Costa-de-Oliveira, Sofia; Cantón, Rafael; Rodrigues, Acácio G.
2016-01-01
The synergy of carbapenem combinations regarding Enterobacteriaceae producing different types of carbapenemases was study through different approaches: flow cytometry and computational analysis. Ten well characterized Enterobacteriaceae (KPC, verona integron-encoded metallo-β-lactamases –VIM and OXA-48-like enzymes) were selected for the study. The cells were incubated with a combination of ertapenem with imipenem, meropenem, or doripenem and killing kinetic curves performed with and without reinforcements of the drugs. A cephalosporin was also used in combination with ertapenem. A flow cytometric assay with DiBAC4-(3), a membrane potential dye, was developed in order to evaluate the cellular lesion after 2 h incubation. A chemical computational study was performed to understand the affinity of the different drugs to the different types of enzymes. Flow cytometric analysis and time-kill assays showed a synergic effect against KPC and OXA-48 producing-bacteria with all combinations; only ertapenem with imipenem was synergic against VIM producing-bacteria. A bactericidal effect was observed in OXA-48-like enzymes. Ceftazidime plus ertapenem was synergic against ESBL-negative KPC producing-bacteria. Ertapenem had the highest affinity for those enzymes according to chemical computational study. The synergic effect between ertapenem and others carbapenems against different carbapenemase-producing bacteria, representing a therapeutic choice, was described for the first time. Easier and faster laboratorial methods for carbapenemase characterization are urgently needed. The design of an ertapenem derivative with similar affinity to carbapenemases but exhibiting more stable bonds was demonstrated as highly desirable. PMID:27555844
Ghosh, Sayari; Chakraborty, Ishita; Chakraborty, Monojit; Mukhopadhyay, Ashis; Mishra, Raghwendra; Sarkar, Debasish
2016-04-01
Erythrocyte morphology is gaining importance as a powerful pathological index in identifying the severity of any blood related disease. However, the existing technique of quantitative microscopy is highly time consuming and prone to personalized bias. On the other hand, relatively unexplored, complementary technique based on flow cytometry has not been standardized till date, particularly due to the lack of a proper morphological scoring scale. In this article, we have presented a new approach to formulate a non-empirical scoring scale based on membrane roughness (R(rms)) data obtained from atomic force microscopy. Subsequently, the respective morphological quantifier of the whole erythrocyte population, commonly known as morphological index, was expressed as a function of highest correlated statistical parameters of scattered signal profiles generated by flow cytometry. Feed forward artificial neural network model with multilayer perceptron architecture was used to develop the intended functional form. High correlation coefficient (R(2) = 0.95), even for model-formulation exclusive samples, clearly indicates the universal validity of the proposed model. Moreover, a direct pathological application of the proposed model has been illustrated in relation to patients, diagnosed to be suffering from a wide variety of cancer. PMID:26824317
Warid, Warid; Hizam, Hashim; Mariun, Norman; Abdul-Wahab, Noor Izzri
2016-01-01
This paper proposes a new formulation for the multi-objective optimal power flow (MOOPF) problem for meshed power networks considering distributed generation. An efficacious multi-objective fuzzy linear programming optimization (MFLP) algorithm is proposed to solve the aforementioned problem with and without considering the distributed generation (DG) effect. A variant combination of objectives is considered for simultaneous optimization, including power loss, voltage stability, and shunt capacitors MVAR reserve. Fuzzy membership functions for these objectives are designed with extreme targets, whereas the inequality constraints are treated as hard constraints. The multi-objective fuzzy optimal power flow (OPF) formulation was converted into a crisp OPF in a successive linear programming (SLP) framework and solved using an efficient interior point method (IPM). To test the efficacy of the proposed approach, simulations are performed on the IEEE 30-busand IEEE 118-bus test systems. The MFLP optimization is solved for several optimization cases. The obtained results are compared with those presented in the literature. A unique solution with a high satisfaction for the assigned targets is gained. Results demonstrate the effectiveness of the proposed MFLP technique in terms of solution optimality and rapid convergence. Moreover, the results indicate that using the optimal DG location with the MFLP algorithm provides the solution with the highest quality. PMID:26954783
An Integrated Design approach to Power Systems: from Power Flows to Electricity Markets
NASA Astrophysics Data System (ADS)
Bose, Subhonmesh
Power system is at the brink of change. Engineering needs, economic forces and environmental factors are the main drivers of this change. The vision is to build a smart electrical grid and a smarter market mechanism around it to fulfill mandates on clean energy. Looking at engineering and economic issues in isolation is no longer an option today; it needs an integrated design approach. In this thesis, I shall revisit some of the classical questions on the engineering operation of power systems that deals with the nonconvexity of power flow equations. Then I shall explore some issues of the interaction of these power flow equations on the electricity markets to address the fundamental issue of market power in a deregulated market environment. Finally, motivated by the emergence of new storage technologies, I present an interesting result on the investment decision problem of placing storage over a power network. The goal of this study is to demonstrate that modern optimization and game theory can provide unique insights into this complex system. Some of the ideas carry over to applications beyond power systems.
Bailey, Matthew R; Pentecost, Amber M; Selimovic, Asmira; Martin, R Scott; Schultz, Zachary D
2015-04-21
The combination of hydrodynamic focusing with embedded capillaries in a microfluidic device is shown to enable both surface enhanced Raman scattering (SERS) and electrochemical characterization of analytes at nanomolar concentrations in flow. The approach utilizes a versatile polystyrene device that contains an encapsulated microelectrode and fluidic tubing, which is shown to enable straightforward hydrodynamic focusing onto the electrode surface to improve detection. A polydimethyslsiloxane (PDMS) microchannel positioned over both the embedded tubing and SERS active electrode (aligned ∼200 μm from each other) generates a sheath flow that confines the analyte molecules eluting from the embedded tubing over the SERS electrode, increasing the interaction between the Riboflavin (vitamin B2) and the SERS active electrode. The microfluidic device was characterized using finite element simulations, amperometry, and Raman experiments. This device shows a SERS and amperometric detection limit near 1 and 100 nM, respectively. This combination of SERS and amperometry in a single device provides an improved method to identify and quantify electroactive analytes over either technique independently. PMID:25815795
NASA Astrophysics Data System (ADS)
Becker, Patrick; Jouvet, Guillaume; Funk, Martin; Seguinot, Julien
2015-04-01
About 20,000 years before present at the end of the Würm glaciation, glaciers in Europe have reached their maximum extent and wide parts of the forelands were covered by ice. Our goal is to reconstruct the European alpine ice cap during the last glaciation using numerical simulations of the ice flow. To do that, we use the Parallel Ice Sheet Model (PISM) to simulate the ice flow. PISM is capable to simulate the time evolution of a large scale ice sheet for millenniums by accounting for the dynamics of ice, englacial temperature, bedrock temperature, lithosphere deformation and surface mass balance. The latter is computed using a positive degree day model that is forced by climate data. A classical approach consists of applying a constant temperature offset to present-day temperature data, while keeping constant today's precipitation patterns. However, geomorphological hints show that the prevailing precipitation regime during the last glaciation was dominated by a southerly atmospheric circulation pattern, in contrast to today's prevalent westerly airflow. Due to this fact we propose several empirical corrections to the present-day precipitation patterns and select those which yield the best match between modeled ice cap extents and geomorphologically-based margin reconstructions.
Assessing Skin Blood Flow Dynamics in Older Adults Using a Modified Sample Entropy Approach
Liao, Fuyuan; Jan, Yih-Kuen
2015-01-01
The aging process may result in attenuated microvascular reactivity in response to environmental stimuli, which can be evaluated by analyzing skin blood flow (SBF) signals. Among various methods for analyzing physiological signals, sample entropy (SE) is commonly used to quantify the degree of regularity of time series. However, we found that for temporally correlated data, SE value depends on the sampling rate. When data are oversampled, SE may give misleading results. To address this problem, we propose to modify the definition of SE by using time-lagged vectors in the calculation of the conditional probability that any two vectors of successive data points are within a tolerance r for m points remain within the tolerance at the next point. The lag could be chosen as the first minimum of the auto mutual information function. We tested the performance of modified SE using simulated signals and SBF data. The results showed that modified SE is able to quantify the degree of regularity of the signals regardless of sampling rate. Using this approach, we observed a more regular behavior of blood flow oscillations (BFO) during local heating-induced maximal vasodilation period compared to the baseline in young and older adults and a more regular behavior of BFO in older adults compared to young adults. These results suggest that modified SE may be useful in the study of SBF dynamics. PMID:25570060
2015-01-01
The combination of hydrodynamic focusing with embedded capillaries in a microfluidic device is shown to enable both surface enhanced Raman scattering (SERS) and electrochemical characterization of analytes at nanomolar concentrations in flow. The approach utilizes a versatile polystyrene device that contains an encapsulated microelectrode and fluidic tubing, which is shown to enable straightforward hydrodynamic focusing onto the electrode surface to improve detection. A polydimethyslsiloxane (PDMS) microchannel positioned over both the embedded tubing and SERS active electrode (aligned ∼200 μm from each other) generates a sheath flow that confines the analyte molecules eluting from the embedded tubing over the SERS electrode, increasing the interaction between the Riboflavin (vitamin B2) and the SERS active electrode. The microfluidic device was characterized using finite element simulations, amperometry, and Raman experiments. This device shows a SERS and amperometric detection limit near 1 and 100 nM, respectively. This combination of SERS and amperometry in a single device provides an improved method to identify and quantify electroactive analytes over either technique independently. PMID:25815795
Fluid migration in the subduction zone: a coupled fluid flow approach
NASA Astrophysics Data System (ADS)
Wang, Hongliang; Huismans, Ritske; Rondenay, Stéphane
2016-04-01
Subduction zone are the main entry point of water into earth's mantle and play an important role in the global water cycle. The progressive release of water by metamorphic dehydration induce important physical-chemical process in the subduction zone, such as hydrous melting, hydration and weakening of the mantle wedge, creation of pore fluid pressures that may weaken the subduction interface and induce earthquakes. Most previous studies on the role of fluids in subduction zones assume vertical migration or migration according to the dynamic pressure in the solid matrix without considering the pore fluid pressure effect on the deformation of the solid matrix. Here we investigate this interaction by explicitly modeling two-phase coupled poro-plastic flow during subduction. In this approach, the fluid migrates by compaction and decompaction of the solid matrix and affects the subduction dynamics through pore fluid pressure dependent frictional-plastic yield. Our preliminary results indicate that: 1) the rate of fluid migration depends strongly on the permeability and the bulk viscosity of the solid matrix, 2) fluid transfer occurs preferentially along the slab and then propagates into the mantle wedge by viscous compaction driven fluid flow, 3) fluid transport from the surface to depth is a prerequisite for producing high fluid pore pressures and associated hydration induced weakening of the subduction zone interface.
NASA Astrophysics Data System (ADS)
Hagan, Jonathan; Priede, Jānis
2013-12-01
We analyze weakly nonlinear stability of a flow of viscous conducting liquid driven by pressure gradient in the channel between two parallel walls subject to a transverse magnetic field. Using a non-standard numerical approach, we compute the linear growth rate correction and the first Landau coefficient, which in a sufficiently strong magnetic field vary with the Hartmann number as μ 1˜ (0.814-i19.8)× 10^{-3}textit {Ha} and μ 2˜ (2.73-i1.50)× 10^{-5}textit {Ha}^{-4}. These coefficients describe a subcritical transverse velocity perturbation with the equilibrium amplitude |A|2=Re [μ 1]/Re [μ 2](textit {Re}c-textit {Re})˜ 29.8textit {Ha}5(textit {Re}c-textit {Re}), which exists at Reynolds numbers below the linear stability threshold textit {Re}c˜ 4.83× 104textit {Ha}. We find that the flow remains subcritically unstable regardless of the magnetic field strength. Our method for computing Landau coefficients differs from the standard one by the application of the solvability condition to the discretized rather than continuous problem. This allows us to bypass both the solution of the adjoint problem and the subsequent evaluation of the integrals defining the inner products, which results in a significant simplification of the method.
Modern approaches to processing large hyperspectral and multispectral aerospace data flows
NASA Astrophysics Data System (ADS)
Bondur, V. G.
2014-12-01
We consider approaches to processing large hyperspectral and multispectral imaging flows produced in aerospace monitoring for solving a wide range of problems of management of natural resources, environmental security, prevention of natural disasters and technogenic accidents, as well as problems of real economy, and basic and applied sciences. We analyze the specific features of the phases of hyperspectral data analysis and describe a software and hardware system that uses new and improved methods and algorithms for processing large flows of hyperspectral and other aerospace data and has a high-performance computer. This system contains different types of software for identifying the types of given objects by solving inverse problems of remote sensing as well as by analyzing their qualitative and quantitative characteristics, combined multiparameter processing of hyperspectral aerospace data, tracking the local changes including those related to changes in meteorological conditions and vegetation periods, detecting and identifying the types of small objects on the basis of analysis of individual parts of the image, detecting and identifying heat sources, etc. We bring examples of processing of hyperspectral and multispectral satellite images with the help of software and hardware tools developed.
Warid, Warid; Hizam, Hashim; Mariun, Norman; Abdul-Wahab, Noor Izzri
2016-01-01
This paper proposes a new formulation for the multi-objective optimal power flow (MOOPF) problem for meshed power networks considering distributed generation. An efficacious multi-objective fuzzy linear programming optimization (MFLP) algorithm is proposed to solve the aforementioned problem with and without considering the distributed generation (DG) effect. A variant combination of objectives is considered for simultaneous optimization, including power loss, voltage stability, and shunt capacitors MVAR reserve. Fuzzy membership functions for these objectives are designed with extreme targets, whereas the inequality constraints are treated as hard constraints. The multi-objective fuzzy optimal power flow (OPF) formulation was converted into a crisp OPF in a successive linear programming (SLP) framework and solved using an efficient interior point method (IPM). To test the efficacy of the proposed approach, simulations are performed on the IEEE 30-busand IEEE 118-bus test systems. The MFLP optimization is solved for several optimization cases. The obtained results are compared with those presented in the literature. A unique solution with a high satisfaction for the assigned targets is gained. Results demonstrate the effectiveness of the proposed MFLP technique in terms of solution optimality and rapid convergence. Moreover, the results indicate that using the optimal DG location with the MFLP algorithm provides the solution with the highest quality. PMID:26954783
A Navier-Stokes-Based Approach for Mean Flow Perturbation Analysis
NASA Astrophysics Data System (ADS)
Bhaumik, Swagata; Gaitonde, Datta; Waindim, Mbu; The Ohio State University Team
2014-11-01
The manner in which a basic state, obtained from a time-averaged unsteady flowfield, processes perturbations can provide significant insight into the cause and evolution of instabilities. A widely used approach is based on Parabolized Stability Equations (PSE), which limits streamwise mean flow variation and is often applied to 2-D base flows. To avoid some of these issues, we advance a Navier-Stokes-based method, which can address non-trivial three-dimensional fields. The method stems from that employed by Touber and Sandham (Theor. Comput. Fluid. Dyn., 23, 79, 2009) to analyze global modes in nominally 2-D shock-wave turbulent-boundary layer interactions (STBLI). We first develop its theoretical underpinnings by examining conditions under which it degenerates to traditional methods. We then illustrate the application by considering perturbations to an entropy layer at Mach 6, a turbulent supersonic jet at Mach 1.3 and STBLI at Mach 2.3. For the entropy layer and jet cases, known linear stability and PSE results are successfully reproduced, while global modes are obtained for STBLI. The results not only validate the proposed technique, but also demonstrate its suitability in analyzing instabilities for any general 3D basic state, including impulse response. Sponsored by AFOSR.
Guan, Xiangmin; Zhang, Xuejun; Zhu, Yanbo; Sun, Dengfeng; Lei, Jiaxing
2015-01-01
Considering reducing the airspace congestion and the flight delay simultaneously, this paper formulates the airway network flow assignment (ANFA) problem as a multiobjective optimization model and presents a new multiobjective optimization framework to solve it. Firstly, an effective multi-island parallel evolution algorithm with multiple evolution populations is employed to improve the optimization capability. Secondly, the nondominated sorting genetic algorithm II is applied for each population. In addition, a cooperative coevolution algorithm is adapted to divide the ANFA problem into several low-dimensional biobjective optimization problems which are easier to deal with. Finally, in order to maintain the diversity of solutions and to avoid prematurity, a dynamic adjustment operator based on solution congestion degree is specifically designed for the ANFA problem. Simulation results using the real traffic data from China air route network and daily flight plans demonstrate that the proposed approach can improve the solution quality effectively, showing superiority to the existing approaches such as the multiobjective genetic algorithm, the well-known multiobjective evolutionary algorithm based on decomposition, and a cooperative coevolution multiobjective algorithm as well as other parallel evolution algorithms with different migration topology. PMID:26180840
Comparison of two different approaches for the control of convectively unstable flows
NASA Astrophysics Data System (ADS)
Juillet, Fabien; Schmid, Peter; McKeon, Beverley; Huerre, Patrick
2011-11-01
The probably most widely used control strategy in the literature is based on the Linear Quadratic Gaussian (LQG) framework. However, this approach seems to be difficult to apply to some fluid systems. In particular, due to their high sensitivity to external noise, amplifier flows are hard to control and the classical LQG compensator may be unable to describe the noise with sufficient accuracy. Another strategy aims at directly measuring these noise sources through a sensor called ``spy.'' The LQG and the spy approaches will be presented and compared using the Ginzburg-Landau equation as a model. It will be shown that the use of a spy is particularly relevant for convectively unstable systems. In addition, the ability of Subspace Identification Methods to provide satisfactory models is demonstrated. Finally, the findings from the Ginzburg-Landau investigation are generalized and applied to a more realistic system, namely a backward-facing step at Re = 350 . Support from Ecole Polytechnique and the Partner University Fund (PUF) is gratefully acknowledged.
Cold Flow as Versatile Approach for Stable and Highly Luminescent Quantum Dot-Salt Composites.
Benad, Albrecht; Guhrenz, Chris; Bauer, Christoph; Eichler, Franziska; Adam, Marcus; Ziegler, Christoph; Gaponik, Nikolai; Eychmüller, Alexander
2016-08-24
Since the beginning of the 1980s, colloidally synthesized quantum dots (QDs) have been in the focus of interest due to their possible implementation for color conversion, luminescent light concentrators, and lasing. For all these applications, the QDs benefit from being embedded into a host matrix to ensure stability and usability. Many different host materials used for this purpose still have their individual shortcomings. Here, we present a universal, fast, and flexible approach for the direct incorporation of a wide range of QDs into inorganic ionic crystals using cold flow. The QD solution is mixed with a finely milled salt, followed by the removal of the solvent under vacuum. Under high pressure (GPa), the salt powder loaded with QDs transforms into transparent pellets. This effect is well-known for many inorganic salts (e.g., KCl, KBr, KI, NaCl, CsI, AgCl) from, e.g., sample preparation for IR spectroscopy. With this approach, we are able to obtain strongly luminescent QD-salt composites, have precise control over the loading, and provide a chemically robust matrix ensuring long-term stability of the embedded QDs. Furthermore, we show the photo-, chemical, and thermal stability of the composite materials and their use as color conversion layers for a white light-emitting diode (w-LED). The method presented can potentially be used for all kinds of nanoparticles synthesized in organic as well as in aqueous media. PMID:27482755
Guan, Xiangmin; Zhang, Xuejun; Zhu, Yanbo; Sun, Dengfeng; Lei, Jiaxing
2015-01-01
Considering reducing the airspace congestion and the flight delay simultaneously, this paper formulates the airway network flow assignment (ANFA) problem as a multiobjective optimization model and presents a new multiobjective optimization framework to solve it. Firstly, an effective multi-island parallel evolution algorithm with multiple evolution populations is employed to improve the optimization capability. Secondly, the nondominated sorting genetic algorithm II is applied for each population. In addition, a cooperative coevolution algorithm is adapted to divide the ANFA problem into several low-dimensional biobjective optimization problems which are easier to deal with. Finally, in order to maintain the diversity of solutions and to avoid prematurity, a dynamic adjustment operator based on solution congestion degree is specifically designed for the ANFA problem. Simulation results using the real traffic data from China air route network and daily flight plans demonstrate that the proposed approach can improve the solution quality effectively, showing superiority to the existing approaches such as the multiobjective genetic algorithm, the well-known multiobjective evolutionary algorithm based on decomposition, and a cooperative coevolution multiobjective algorithm as well as other parallel evolution algorithms with different migration topology. PMID:26180840
ERIC Educational Resources Information Center
Gaske, Dan
1992-01-01
Provides a graphical framework for presenting interactions among current account flows, capital account flows, and exchange rates. Suggests that the two type of flows must be considered separately in discussions of foreign exchange equilibrium and balance of payments flows. Supplies sample graphs and instructions for applying the framework to real…
NASA Astrophysics Data System (ADS)
Sokhal, Abdellah; Bougandoura, Adel; Ouadfeul, Sid-Ali
2015-04-01
In this work, fluid flow paths are discriminated from standard well logs and core data through the utilization of Hydraulic Flow Units Approach (HFU) and an intelligent network. Firstly, the flow zone indicator (FZI), which is a unique parameter for each hydraulic unit, was used to characterize each rock type. The number of hydraulic flow units and mean values of FZI for each HFU were calculated from porosity and permeability measured from core-rocks. Application to data of a borehole located in the Algerian Sahara shows the existence of three HFUs and a correlation coefficient greater than 0.9 in each HFU was observed. Some FZI were attributed for un-cored wells using the Fuzzy Logic system (FL). Well-logs data that are used as an input to train the fuzzy system are the neutron porosity, the bulk density, the slowness of the P wave, the resistivity of the shallow and the deep zones and the natural gamma ray. The calculated FZI associated to these depths interval are used as an output. The presented methodology was successfully applied to a large data set of laboratory and well logging measurements from the Hassi D'zaabat field. Keywords: Fluid flow; FZI, Hydraulic Flow Unit (HFU); Fuzzy logic.
Ensuring the consistancy of Flow Direction Curve reconstructions: the 'quantile solidarity' approach
NASA Astrophysics Data System (ADS)
Poncelet, Carine; Andreassian, Vazken; Oudin, Ludovic
2015-04-01
Flow Duration Curves (FDCs) are a hydrologic tool describing the distribution of streamflows at a catchment outlet. FDCs are usually used for calibration of hydrological models, managing water quality and classifying catchments, among others. For gauged catchments, empirical FDCs can be computed from streamflow records. For ungauged catchments, on the other hand, FDCs cannot be obtained from streamflow records and must therefore be obtained in another manner, for example through reconstructions. Regression-based reconstructions are methods relying on the evaluation of quantiles separately from catchments' attributes (climatic or physical features).The advantage of this category of methods is that it is informative about the processes and it is non-parametric. However, the large number of parameters required can cause unwanted artifacts, typically reconstructions that do not always produce increasing quantiles. In this paper we propose a new approach named Quantile Solidarity (QS), which is applied under strict proxy-basin test conditions (Klemes, 1986) to a set of 600 French catchments. Half of the catchments are considered as gauged and used to calibrate the regression and compute residuals of the regression. The QS approach consists in a three-step regionalization scheme, which first links quantile values to physical descriptors, then reduces the number of regression parameters and finally exploits the spatial correlation of the residuals. The innovation is the utilisation of the parameters continuity across the quantiles to dramatically reduce the number of parameters. The second half of catchment is used as an independent validation set over which we show that the QS approach ensures strictly growing FDC reconstructions in ungauged conditions. Reference: V. KLEMEŠ (1986) Operational testing of hydrological simulation models, Hydrological Sciences Journal, 31:1, 13-24
NASA Astrophysics Data System (ADS)
Gallant, E.; Connor, C.; Richardson, J. A.; Wetmore, P. H.; Connor, L.
2015-12-01
We present the results of a lava flow hazard assessment for the Idaho National Laboratory (INL) using a new lava flow code, MOLASSES (MOdular LAva Simulation Software for Earth Science). INL is a nuclear research and development facility located on the eastern Snake River Plain with the potential for lava flow inundation from both monogenetic and polygenetic basaltic eruptions. Previously published inventories of observed surface vents and vents that are buried by younger lava flows and inferred from interpretation of borehole stratigraphy were used to created spatial density maps of vents within the INL region. Monte carlo simulations were run using the MOLASSES code to compare the difference between events initiated using only surface vents and events initiated using both the surface and the buried vents. We find that the inclusion of the buried vent locations drastically increases the number of site inundations and events initiating within INL boundaries. This highlights the need to seek out a more complete eruption record in an area of heavy prehistoric activity to better assess future hazard and associated risk.
Wang, J.S.Y.; Narasimhan, T.N.
1993-06-01
This report discusses conceptual models and mathematical equations, analyzes distributions and correlations among hydrological parameters of soils and tuff, introduces new path integration approaches, and outlines scaling procedures to model potential-driven fluid flow in heterogeneous media. To properly model the transition from fracture-dominated flow under saturated conditions to matrix-dominated flow under partially saturated conditions, characteristic curves and permeability functions for fractures and matrix need to be improved and validated. Couplings from two-phase flow, heat transfer, solute transport, and rock deformation to liquid flow are also important. For stochastic modeling of alternating units of welded and nonwelded tuff or formations bounded by fault zones, correlations and constraints on average values of saturated permeability and air entry scaling factor between different units need to be imposed to avoid unlikely combinations of parameters and predictions. Large-scale simulations require efficient and verifiable numerical algorithms. New path integration approaches based on postulates of minimum work and mass conservation to solve flow geometry and potential distribution simultaneously are introduced. This verifiable integral approach, together with fractal scaling procedures to generate statistical realizations with parameter distribution, correlation, and scaling taken into account, can be used to quantify uncertainties and generate the cumulative distribution function for groundwater travel times.
NASA Astrophysics Data System (ADS)
Chang, Tsang-Jung; Chang, Kao-Hua; Kao, Hong-Ming
2014-11-01
A new approach to model weakly nonhydrostatic shallow water flows in open channels is proposed by using a Lagrangian meshless method, smoothed particle hydrodynamics (SPH). The Lagrangian form of the Boussinesq equations is solved through SPH to merge the local and convective derivatives as the material derivative. In the numerical SPH procedure, the present study uses a predictor-corrector method, in which the pure space derivative terms (the hydrostatic and source terms) are explicitly solved and the mixed space and time derivatives term (the material term of B1 and B2) is computed with an implicit scheme. It is thus a convenient tool in the processes of the space discretization compared to other Eulerian approaches. Four typical benchmark problems in weakly nonhydrostatic shallow water flows, including solitary wave propagation, nonlinear interaction of two solitary waves, dambreak flow propagation, and undular bore development, are selected to employ model validation under the closed and open boundary conditions. Numerical results are compared with the analytical solutions or published laboratory and numerical results. It is found that the proposed approach is capable of resolving weakly nonhydrostatic shallow water flows. Thus, the proposed SPH approach can supplement the lack of the SPH-Boussinesq researches in the literatures, and provide an alternative to model weakly nonhydrostatic shallow water flows in open channels.
Hughes, Francine M R; Rood, Stewart B
2003-07-01
Floodplain forests are flood-dependent ecosystems. They rely on well-timed, periodic floods for the provision of regeneration sites and on tapered flood recession curves for the successful establishment of seedlings. These overbank flood events are described as "regeneration flows." Once floodplain forest trees are established, in order to grow they also require adequate, although variable, river stage levels or "maintenance flows" throughout the year. Regeneration flows are often synonymous with flood flows and only occur periodically. There is a disparity between this need for varied interannual flows over the decadal time frame and the usual annual cycle of flow management currently used by most river management agencies. Maintenance flows are often closer to established minimum flows and much easier to provide by current operational practices.A number of environmental flow methodologies, developed in North America, Australia, and South Africa are described in this review. They include the needs of the floodplain environment in the management and allocation of river flows. In North America, these methodologies have been put into practice in a number of river basins specifically to restore floodplain forest ecosystems. In Australia and South Africa, a series of related "holistic approaches" have been developed that include the needs of floodplain ecosystems as well as in-channel ecosystems. In most European countries, restoration of floodplain forests takes place at a few localized restoration sites, more often as part of a flood-defense scheme and usually not coordinated with flow allocation decisions throughout the river basin. The potential to apply existing environmental flow methodologies to the management of European floodplain forests is discussed. PMID:14703910
Minimal sensor count approach to fuzzy logic rotary blood pump flow control.
Casas, Fernando; Ahmed, Nisar; Reeves, Andrew
2007-01-01
A rotary blood pump fuzzy logic flow controller without flow sensors was developed and tested in vitro. The controller, implemented in LabView, was set to maintain a flow set point in the presence of external pressure disturbances. Flow was estimated as a function of measured pump's delta P and speed, using a steady-state, nonlinear approximation. The fuzzy controller used the pump's flow estimate and delta P as feedback variables. The defuzzified control output manipulated the pump speed. Membership functions included flow error, delta P, and pump speed. Experimental runs in a mock loop (water/glycerin 3.5 cPs, 37 degrees C), using the estimated flow, were compared with those using a Transonic flow meter for nine conditions of flow and delta P (4 to 6 L/min, 150 to 350 mm Hg). Pressure disturbances generated by a servo pinch valve ranged from +/-23 to +/-47 mm Hg. Results indicated that the fuzzy controller ably regulated the flow set point to within +/-10% of the baseline even under large swings in pressure. There was no difference in controller performance between the ultrasonic flow measurement and the estimated flow calculation scenarios. These tests demonstrated that the fuzzy controller is capable of rejecting disturbances and regulating flow to acceptable limits while using a flow estimate. PMID:17413551
NASA Astrophysics Data System (ADS)
Piotrowski, Adam P.; Napiorkowski, Jarosław J.
2011-09-01
SummaryAlthough neural networks have been widely applied to various hydrological problems, including river flow forecasting, for at least 15 years, they have usually been trained by means of gradient-based algorithms. Recently nature inspired Evolutionary Computation algorithms have rapidly developed as optimization methods able to cope not only with non-differentiable functions but also with a great number of local minima. Some of proposed Evolutionary Computation algorithms have been tested for neural networks training, but publications which compare their performance with gradient-based training methods are rare and present contradictory conclusions. The main goal of the present study is to verify the applicability of a number of recently developed Evolutionary Computation optimization methods, mostly from the Differential Evolution family, to multi-layer perceptron neural networks training for daily rainfall-runoff forecasting. In the present paper eight Evolutionary Computation methods, namely the first version of Differential Evolution (DE), Distributed DE with Explorative-Exploitative Population Families, Self-Adaptive DE, DE with Global and Local Neighbors, Grouping DE, JADE, Comprehensive Learning Particle Swarm Optimization and Efficient Population Utilization Strategy Particle Swarm Optimization are tested against the Levenberg-Marquardt algorithm - probably the most efficient in terms of speed and success rate among gradient-based methods. The Annapolis River catchment was selected as the area of this study due to its specific climatic conditions, characterized by significant seasonal changes in runoff, rapid floods, dry summers, severe winters with snowfall, snow melting, frequent freeze and thaw, and presence of river ice - conditions which make flow forecasting more troublesome. The overall performance of the Levenberg-Marquardt algorithm and the DE with Global and Local Neighbors method for neural networks training turns out to be superior to other
Mirus, Benjamin B.; Nimmo, J.R.
2013-01-01
The impact of preferential flow on recharge and contaminant transport poses a considerable challenge to water-resources management. Typical hydrologic models require extensive site characterization, but can underestimate fluxes when preferential flow is significant. A recently developed source-responsive model incorporates film-flow theory with conservation of mass to estimate unsaturated-zone preferential fluxes with readily available data. The term source-responsive describes the sensitivity of preferential flow in response to water availability at the source of input. We present the first rigorous tests of a parsimonious formulation for simulating water table fluctuations using two case studies, both in arid regions with thick unsaturated zones of fractured volcanic rock. Diffuse flow theory cannot adequately capture the observed water table responses at both sites; the source-responsive model is a viable alternative. We treat the active area fraction of preferential flow paths as a scaled function of water inputs at the land surface then calibrate the macropore density to fit observed water table rises. Unlike previous applications, we allow the characteristic film-flow velocity to vary, reflecting the lag time between source and deep water table responses. Analysis of model performance and parameter sensitivity for the two case studies underscores the importance of identifying thresholds for initiation of film flow in unsaturated rocks, and suggests that this parsimonious approach is potentially of great practical value.
Computation of viscous flows over airfoils, including separation, with a coupling approach
NASA Technical Reports Server (NTRS)
Leballeur, J. C.
1983-01-01
Viscous incompressible flows over single or multiple airfoils, with or without separation, were computed using an inviscid flow calculation, with modified boundary conditions, and by a method providing calculation and coupling for boundary layers and wakes, within conditions of strong viscous interaction. The inviscid flow is calculated with a method of singularities, the numerics of which were improved by using both source and vortex distributions over profiles, associated with regularity conditions for the fictitious flows inside of the airfoils. The viscous calculation estimates the difference between viscous flow and inviscid interacting flow, with a direct or inverse integral method, laminar or turbulent, with or without reverse flow. The numerical method for coupling determines iteratively the boundary conditions for the inviscid flow. For attached viscous layers regions, an underrelaxation is locally calculated to insure stability. For separated or separating regions, a special semi-inverse algorithm is used. Comparisons with experiments are presented.
A Many-Task Parallel Approach for Multiscale Simulations of Subsurface Flow and Reactive Transport
Scheibe, Timothy D.; Yang, Xiaofan; Schuchardt, Karen L.; Agarwal, Khushbu; Chase, Jared M.; Palmer, Bruce J.; Tartakovsky, Alexandre M.
2014-12-16
Continuum-scale models have long been used to study subsurface flow, transport, and reactions but lack the ability to resolve processes that are governed by pore-scale mixing. Recently, pore-scale models, which explicitly resolve individual pores and soil grains, have been developed to more accurately model pore-scale phenomena, particularly reaction processes that are controlled by local mixing. However, pore-scale models are prohibitively expensive for modeling application-scale domains. This motivates the use of a hybrid multiscale approach in which continuum- and pore-scale codes are coupled either hierarchically or concurrently within an overall simulation domain (time and space). This approach is naturally suited to an adaptive, loosely-coupled many-task methodology with three potential levels of concurrency. Each individual code (pore- and continuum-scale) can be implemented in parallel; multiple semi-independent instances of the pore-scale code are required at each time step providing a second level of concurrency; and Monte Carlo simulations of the overall system to represent uncertainty in material property distributions provide a third level of concurrency. We have developed a hybrid multiscale model of a mixing-controlled reaction in a porous medium wherein the reaction occurs only over a limited portion of the domain. Loose, minimally-invasive coupling of pre-existing parallel continuum- and pore-scale codes has been accomplished by an adaptive script-based workflow implemented in the Swift workflow system. We describe here the methods used to create the model system, adaptively control multiple coupled instances of pore- and continuum-scale simulations, and maximize the scalability of the overall system. We present results of numerical experiments conducted on NERSC supercomputing systems; our results demonstrate that loose many-task coupling provides a scalable solution for multiscale subsurface simulations with minimal overhead.
An approximate viscous shock layer approach to calculating hypersonic flows about blunt-nosed bodies
NASA Technical Reports Server (NTRS)
Cheatwood, F. MCN.; Dejarnette, F. R.
1991-01-01
An approximate axisymmetric method has been developed which can reliably calculate fully viscous hypersonic flows over blunt-nosed bodies. By substituting Maslen's second order pressure expression for the normal momentum equation, a simplified form of the viscous shock layer (VSL) equations is obtained. This approach can solve both the subsonic and supersonic regions of the shock layer without a starting solution for the shock shape. Since the method is fully viscous, the problems associated with coupling a boundary-layer solution with an inviscid-layer solution are avoided. This procedure is significantly faster than the parabolized Navier-Stokes (PNS) or VSL solvers and would be useful in a preliminary design environment. Problems associated with a previously developed approximate VSL technique are addressed. Surface heat transfer and pressure predictions are comparable to both VSL results and experimental data. The present technique generates its own shock shape as part of its solution, and therefore could be used to provide more accurate initial shock shapes for higher-order procedures which require starting solutions.
Space station electrical power distribution analysis using a load flow approach
NASA Technical Reports Server (NTRS)
Emanuel, Ervin M.
1987-01-01
The space station's electrical power system will evolve and grow in a manner much similar to the present terrestrial electrical power system utilities. The initial baseline reference configuration will contain more than 50 nodes or busses, inverters, transformers, overcurrent protection devices, distribution lines, solar arrays, and/or solar dynamic power generating sources. The system is designed to manage and distribute 75 KW of power single phase or three phase at 20 KHz, and grow to a level of 300 KW steady state, and must be capable of operating at a peak of 450 KW for 5 to 10 min. In order to plan far into the future and keep pace with load growth, a load flow power system analysis approach must be developed and utilized. This method is a well known energy assessment and management tool that is widely used throughout the Electrical Power Utility Industry. The results of a comprehensive evaluation and assessment of an Electrical Distribution System Analysis Program (EDSA) is discussed. Its potential use as an analysis and design tool for the 20 KHz space station electrical power system is addressed.
Rockfall and debris flow mitigation : Innovative systems for a new efficient and integrated approach
NASA Astrophysics Data System (ADS)
Villard, Nicolas; Robit, Philippe
2014-05-01
In the French Alps the latest generation of high performance systems against rockfall and debris flow has been developed by the contractor GTS taking a relatively lightweight approach, developed from decades of experience working with the more traditional catch fence systems. It allows to adapt the solution to the field rather than the opposite. Moreover it offers relevant alternates economically, in a global context of budget restrictions, and environmentally, with lower carbon emissions and impacts. The new barriers and patented systems have minimal anchoring requirements and are effective in difficult ground conditions. They are designed to be as simple, safe and rapid as possible to install in any location, including high on the slope by rope access workers. Barriers can now cost effectively be installed near the failure source, where energies are lower and where shorter fences can mitigate the hazard. System components have been kept as simple as possible to ensure maximum lifetime, minimise maintenance requirements and to facilitate repairs in the field at low cost. GTS has carried out extensive multi-scale analyses of their new systems including full scale testing to meet evolving guidelines.
A Hybrid Statistics/Amplitude Approach to the Theory of Interacting Drift Waves and Zonal Flows
NASA Astrophysics Data System (ADS)
Parker, Jeffrey; Krommes, John
2012-10-01
An approach to the theory of drift-wave--zonal-flow systems is adopted in which only the DW statistics but the full ZF amplitude are kept. Any statistical description of turbulence must inevitably face the closure problem. A particular closure, the Stochastic Structural Stability Theory (SSST), has been recently studied in plasmafootnotetextB. F. Farrell and P. J. Ioannou, Phys. Plasmas 16, 112903 (2009). as well as atmospheric-science contexts. First, the predictions of the SSST are examined in the weakly inhomogeneous limit, using the generalized Hasegawa--Mima model as a simple example. It is found that the equations do not admit a complete solution, as the characteristic ZF scale cannot be calculated. To address that deficiency, an analysis is performed of a bifurcation from a DW-only state to a DW--ZF state in the Hasegawa--Wakatani model in order to gain analytical insight into a nonlinear DW--ZF equilibrium, including prediction of the charactistic scale. The calculation permits discussion of the relative importance of eddy shearing and coupling to damped eigenmodes for the saturation of the self-consistently regulated turbulence level.
Habib, Komal; Schibye, Peter Klausen; Vestbø, Andreas Peter; Dall, Ole; Wenzel, Henrik
2014-10-21
Neodymium-iron-boron (NdFeB) magnets have become highly desirable for modern hi-tech applications. These magnets, in general, contain two key rare earth elements (REEs), i.e., neodymium (Nd) and dysprosium (Dy), which are responsible for the very high strength of these magnets, allowing for considerable size and weight reduction in modern applications. This study aims to explore the current and future potential of a secondary supply of neodymium and dysprosium from recycling of NdFeB magnets. For this purpose, material flow analysis (MFA) has been carried out to perform the detailed mapping of stocks and flows of NdFeB magnets in Denmark. A novel element of this study is the value added to the traditionally practiced MFAs at national and/or global levels by complementing them with a comprehensive sampling and elemental analysis of NdFeB magnets, taken out from a sample of 157 different products representing 18 various product types. The results show that the current amount of neodymium and dysprosium in NdFeB magnets present in the Danish waste stream is only 3 and 0.2 Mg, respectively. However, this number is estimated to increase to 175 Mg of neodymium and 11.4 Mg of dysprosium by 2035. Nevertheless, efficient recovery of these elements from a very diverse electronic waste stream remains a logistic and economic challenge. PMID:25238428
NASA Astrophysics Data System (ADS)
Corsini, A.
2009-04-01
Landslide monitoring has evolved as a crucial tool in civil protection to mitigate and prevent disasters. The research presents an approach to continuous monitoring of a large-scale active earth flow using a system that integrates surface measurements obtained by a GPS and an automatic total station. With the data obtained from the system the landslide can be monitored in near-real-time and surface displacements can be directly utilized to provide early warning of slope movements and to study the behavior of the landslide, e.g. to predict timing and mechanisms of future failure. The Valoria landslide located in the northern Apennines of Italy was reactivated in 2001, 2005 and 2007 damaging roads and endangering houses. A monitoring system was installed in 2007-2008 in the frame of a civil protection plan aimed at risk mitigation. The system consists of an automatic total station measuring about 40 prisms located in the landslide to a maximum distance of 1.800 km; one double-frequency GPS receiver connects in streaming by wireless communication with 4 single-frequency GPS in side the flow. Until December 2007 the monitoring network was operated with periodic static surveying followed by the data post-processing. From September 2007 until March 2008 the landslide deformation was evaluated by periodic surveys with the total station and the GPS system. This first measure showed that the displacements were influenced by the rainfall events and by the snow melting. The total displacements measured vary from centimeter scale in the crown zone, where retrogressive movements were in progress, to over 50 m in the flow track zone. Starting in March 2008 data acquisition by the total station system and GPS were automated in order to allow continuous and near-real-time data processing. The displacement data collected in one and a half year of continuous operation show different acceleration and deceleration phases as a result of the pore water pressure distribution inside the
Hollingsworth, Jennifer A.; Palaniappan, Kumaranand; Laocharoensuk, Rawiwan; Smith, Nickolaus A.; Dickerson, Robert M.; Casson, Joanna L.; Baldwin, Jon K.
2012-06-07
Semiconductor nanowires (SC-NWs) have potential applications in diverse technologies from nanoelectronics and photonics to energy harvesting and storage due to their quantum-confined opto-electronic properties coupled with their highly anisotropic shape. Here, we explore new approaches to an important solution-based growth method known as solution-liquid-solid (SLS) growth. In SLS, molecular precursors are reacted in the presence of low-melting metal nanoparticles that serve as molten fluxes to catalyze the growth of the SC-NWs. The mechanism of growth is assumed to be similar to that of vapor-liquid-solid (VLS) growth, with the clear distinctions of being conducted in solution in the presence of coordinating ligands and at relatively lower temperatures (<300 C). The resultant SC-NWs are soluble in common organic solvents and solution processable, offering advantages such as simplified processing, scale-up, ultra-small diameters for quantum-confinement effects, and flexible choice of materials from group III-V to groups II-VI, IV-VI, as well as truly ternary I-III-VI semiconductors as we recently demonstrates. Despite these advantages of SLS growth, VLS offers several clear opportunities not allowed by conventional SLS. Namely, VLS allows sequential addition of precursors for facile synthesis of complex axial heterostructures. In addition, growth proceeds relatively slowly compared to SLS, allowing clear assessments of growth kinetics. In order to retain the materials and processing flexibility afforded by SLS, but add the elements of controlled growth afforded by VLS, we transformed SLS into a flow based method by adapting it to synthesis in a microfluidic system. By this new method - so-called 'flow-SLS' (FSLS) - we have now demonstrated unprecedented fabrication of multi-segmented SC-NWs, e.g., 8-segmented CdSe/ZnSe defined by either compositionally abrupt or alloyed interfaces as a function of growth conditions. In addition, we have studied growth rates as a
NASA Astrophysics Data System (ADS)
Fischer, Thomas; Küfmann, Carola; Haas, Florian; Baume, Otfried; Becht, Michael
2013-04-01
The high mountain systems of Central Asia (Hindukush, Pamir and Tien Shan) are dominated by continental-climatic conditions. Nevertheless, westerly maritime air circulation and convective rainfalls during the summer season result in high rainfall intensities. In combination with a high availability of unconsolidated material rainfall triggered debris flows are prominent and intensive geomorphologic processes in these mountain areas. The presented study aims to figure out a regional based modeling approach for rainfall-induced debris flow processes based on combination of a disposition model for debris flow starting zones with process-flow models. The investigation area has a size of about 700 square kilometers and is situated in the Northern Tien Shan mountains in SE Kazakhstan (investigation areas: valleys of Prochadnaja, Big Almatinka, Little Almatinka and Left Talgar). The area is characterized by mountain forest zone, alpine meadows and high-alpine glaciated areas with the highest peaks at 4500m. In a first step the disposition (point of process triggering) of actual debris flows was analyzed. Due to different triggering mechanisms, the processes were divided into channel-type and slope-type debris flows. Detailed mapping of actual debris flows initiation areas and a GIS-based geostatistical disposition analysis are used to identify the main geofactor-variables and geofactor combinations which enhance the triggering of rainfall-induced debris flows. It can be shown that both, longtime variable geofactors (such as local geomorphology and hydrology) plays a significant role for triggering debris flows, as well as mid- and short time variable geofactors. Especially actual permafrost distribution and degradation plus glacier retreat comes into the focus of interest. This is most notably for rainfall induced slope-type debris flows which primarily are triggered in the discontinuous and continuous permafrost areas eroding younger unconsolidated material from actual
Approaches to Modeling Coupled Flow and Reaction in a 2-D Cementation Experiment
Steefel, Carl; Cochepin, B.; Trotignon, L.; Bildstein, O.; Steefel, C.; Lagneau, V.; van der Lee, J.
2008-04-01
Porosity evolution at reactive interfaces is a key process that governs the evolution and performances of many engineered systems that have important applications in earth and environmental sciences. This is the case, for example, at the interface between cement structures and clays in deep geological nuclear waste disposals. Although in a different transport regime, similar questions arise for permeable reactive barriers used for biogeochemical remediation in surface environments. The COMEDIE project aims at investigating the coupling between transport, hydrodynamics and chemistry when significant variations of porosity occur. The present work focuses on a numerical benchmark used as a design exercise for the future COMEDIE-2D experiment. The use of reactive transport simulation tools like Hytec and Crunch provides predictions of the physico-chemical evolutions that are expected during the future experiments in laboratory. Focus is given in this paper on the evolution during the simulated experiment of precipitate, permeability and porosity fields. A first case is considered in which the porosity is constant. Results obtained with Crunch and Hytec are in relatively good agreement. Differences are attributable to the models of reactive surface area taken into account for dissolution/precipitation processes. Crunch and Hytec simulations taking into account porosity variations are then presented and compared. Results given by the two codes are in qualitative agreement, with differences attributable in part to the models of reactive surface area for dissolution/precipitation processes. As a consequence, the localization of secondary precipitates predicted by Crunch leads to lower local porosities than for predictions obtained by Hytec and thus to a stronger coupling between flow and chemistry. This benchmark highlights the importance of the surface area model employed to describe systems in which strong porosity variations occur as a result of dissolution
Itu, Lucian; Rapaka, Saikiran; Passerini, Tiziano; Georgescu, Bogdan; Schwemmer, Chris; Schoebinger, Max; Flohr, Thomas; Sharma, Puneet; Comaniciu, Dorin
2016-07-01
Fractional flow reserve (FFR) is a functional index quantifying the severity of coronary artery lesions and is clinically obtained using an invasive, catheter-based measurement. Recently, physics-based models have shown great promise in being able to noninvasively estimate FFR from patient-specific anatomical information, e.g., obtained from computed tomography scans of the heart and the coronary arteries. However, these models have high computational demand, limiting their clinical adoption. In this paper, we present a machine-learning-based model for predicting FFR as an alternative to physics-based approaches. The model is trained on a large database of synthetically generated coronary anatomies, where the target values are computed using the physics-based model. The trained model predicts FFR at each point along the centerline of the coronary tree, and its performance was assessed by comparing the predictions against physics-based computations and against invasively measured FFR for 87 patients and 125 lesions in total. Correlation between machine-learning and physics-based predictions was excellent (0.9994, P < 0.001), and no systematic bias was found in Bland-Altman analysis: mean difference was -0.00081 ± 0.0039. Invasive FFR ≤ 0.80 was found in 38 lesions out of 125 and was predicted by the machine-learning algorithm with a sensitivity of 81.6%, a specificity of 83.9%, and an accuracy of 83.2%. The correlation was 0.729 (P < 0.001). Compared with the physics-based computation, average execution time was reduced by more than 80 times, leading to near real-time assessment of FFR. Average execution time went down from 196.3 ± 78.5 s for the CFD model to ∼2.4 ± 0.44 s for the machine-learning model on a workstation with 3.4-GHz Intel i7 8-core processor. PMID:27079692
Abgrall, Rémi; Congedo, Pietro Marco
2013-02-15
This paper deals with the formulation of a semi-intrusive (SI) method allowing the computation of statistics of linear and non linear PDEs solutions. This method shows to be very efficient to deal with probability density function of whatsoever form, long-term integration and discontinuities in stochastic space. Given a stochastic PDE where randomness is defined on Ω, starting from (i) a description of the solution in term of a space variables, (ii) a numerical scheme defined for any event ω∈Ω and (iii) a (family) of random variables that may be correlated, the solution is numerically described by its conditional expectancies of point values or cell averages and its evaluation constructed from the deterministic scheme. One of the tools is a tessellation of the random space as in finite volume methods for the space variables. Then, using these conditional expectancies and the geometrical description of the tessellation, a piecewise polynomial approximation in the random variables is computed using a reconstruction method that is standard for high order finite volume space, except that the measure is no longer the standard Lebesgue measure but the probability measure. This reconstruction is then used to formulate a scheme on the numerical approximation of the solution from the deterministic scheme. This new approach is said semi-intrusive because it requires only a limited amount of modification in a deterministic solver to quantify uncertainty on the state when the solver includes uncertain variables. The effectiveness of this method is illustrated for a modified version of Kraichnan–Orszag three-mode problem where a discontinuous pdf is associated to the stochastic variable, and for a nozzle flow with shocks. The results have been analyzed in terms of accuracy and probability measure flexibility. Finally, the importance of the probabilistic reconstruction in the stochastic space is shown up on an example where the exact solution is computable, the viscous
NASA Astrophysics Data System (ADS)
Abgrall, Rémi; Congedo, Pietro Marco
2013-02-01
This paper deals with the formulation of a semi-intrusive (SI) method allowing the computation of statistics of linear and non linear PDEs solutions. This method shows to be very efficient to deal with probability density function of whatsoever form, long-term integration and discontinuities in stochastic space. Given a stochastic PDE where randomness is defined on Ω, starting from (i) a description of the solution in term of a space variables, (ii) a numerical scheme defined for any event ω∈Ω and (iii) a (family) of random variables that may be correlated, the solution is numerically described by its conditional expectancies of point values or cell averages and its evaluation constructed from the deterministic scheme. One of the tools is a tessellation of the random space as in finite volume methods for the space variables. Then, using these conditional expectancies and the geometrical description of the tessellation, a piecewise polynomial approximation in the random variables is computed using a reconstruction method that is standard for high order finite volume space, except that the measure is no longer the standard Lebesgue measure but the probability measure. This reconstruction is then used to formulate a scheme on the numerical approximation of the solution from the deterministic scheme. This new approach is said semi-intrusive because it requires only a limited amount of modification in a deterministic solver to quantify uncertainty on the state when the solver includes uncertain variables. The effectiveness of this method is illustrated for a modified version of Kraichnan-Orszag three-mode problem where a discontinuous pdf is associated to the stochastic variable, and for a nozzle flow with shocks. The results have been analyzed in terms of accuracy and probability measure flexibility. Finally, the importance of the probabilistic reconstruction in the stochastic space is shown up on an example where the exact solution is computable, the viscous
Fluidelastic instability in a confined annular flow: An experimental and analytical approach
Porcher, G.; Langre, E. de
1996-12-01
Self excitation of slender structures under axial flow have been reported in a large variety of local flow configurations. This paper reports the result of a research program, both experimental and analytical, aimed at the result of the basic phenomena leading to such instabilities. A cylindrical body with a diffuser is put in a confined annular flow of water. A case of flutter is observed and analyzed with a classical potential flow method and with a friction based model. Closed-form solutions are proposed and the origin of the flutter instability is discussed. This is relevant for nuclear fuel studies.
NASA Astrophysics Data System (ADS)
Zhang, G. P.; Savenije, H. H. G.; Fenicia, F.; Pfister, L.
2006-02-01
A new domain, the macropore domain, for describing subsurface storm flow has been introduced to the Representative Elementary Watershed (REW) approach. The mass balance equations have been reformulated and the closure relations associated with subsurface storm flow have been developed. The model code, REWASH, has been revised accordingly. With the revised REWASH, a rainfall-runoff model has been built for the Hesperange catchment, a sub-catchment of the Alzette River Basin. This meso-scale catchment is characterised by fast catchment response to precipitation and subsurface storm flow is one of the dominant runoff generation processes. The model has been evaluated by a multi-criteria approach using both discharge and groundwater table data measured at various locations in the study site. It is demonstrated that subsurface storm flow contributes considerably to stream flow in the study area. Simulation results show that discharges measured along the main river course are well simulated and groundwater dynamics is well captured, suggesting that the model is a useful tool for catchment-scale hydrological analysis.
NASA Astrophysics Data System (ADS)
Zhang, G. P.; Savenije, H. H. G.; Fenicia, F.; Pfister, L.
2006-12-01
A new domain, the macropore domain describing subsurface storm flow, has been introduced to the Representative Elementary Watershed (REW) approach. The mass balance equations have been reformulated and the closure relations associated with subsurface storm flow have been developed. The model code, REWASH, has been revised accordingly. With the revised REWASH, a rainfall-runoff model has been built for the Hesperange catchment, a sub-catchment of the Alzette River Basin. This meso-scale catchment is characterised by fast catchment response to precipitation, and subsurface storm flow is one of the dominant runoff generation processes. The model has been evaluated by a multi-criteria approach using both discharge and groundwater table data measured at various locations in the study site. It is demonstrated that subsurface storm flow contributes considerably to stream flow in the study area. Simulation results show that discharges measured along the main river course are well simulated and groundwater dynamics is well captured, suggesting that the model is a useful tool for catchment-scale hydrological analysis.
Tutty, O.
2015-01-01
With the goal of providing the first example of application of a recently proposed method, thus demonstrating its ability to give results in principle, global stability of a version of the rotating Couette flow is examined. The flow depends on the Reynolds number and a parameter characterizing the magnitude of the Coriolis force. By converting the original Navier–Stokes equations to a finite-dimensional uncertain dynamical system using a partial Galerkin expansion, high-degree polynomial Lyapunov functionals were found by sum-of-squares of polynomials optimization. It is demonstrated that the proposed method allows obtaining the exact global stability limit for this flow in a range of values of the parameter characterizing the Coriolis force. Outside this range a lower bound for the global stability limit was obtained, which is still better than the energy stability limit. In the course of the study, several results meaningful in the context of the method used were also obtained. Overall, the results obtained demonstrate the applicability of the recently proposed approach to global stability of the fluid flows. To the best of our knowledge, it is the first case in which global stability of a fluid flow has been proved by a generic method for the value of a Reynolds number greater than that which could be achieved with the energy stability approach. PMID:26730219
NASA Technical Reports Server (NTRS)
Shih, Tsan-Hsing; Liu, Nan-Suey
2008-01-01
This paper describes an approach which aims at bridging the gap between the traditional Reynolds-averaged Navier-Stokes (RANS) approach and the traditional large eddy simulation (LES) approach. It has the characteristics of the very large eddy simulation (VLES) and we call this approach the partially-resolved numerical simulation (PRNS). Systematic simulations using the National Combustion Code (NCC) have been carried out for fully developed turbulent pipe flows at different Reynolds numbers to evaluate the PRNS approach. Also presented are the sample results of two demonstration cases: nonreacting flow in a single injector flame tube and reacting flow in a Lean Direct Injection (LDI) hydrogen combustor.
Topographic controls on overland flow generation in a forest - An ensemble tree approach
NASA Astrophysics Data System (ADS)
Loos, Martin; Elsenbeer, Helmut
2011-10-01
SummaryOverland flow is an important hydrological pathway in many forests of the humid tropics. Its generation is subject to topographic controls at differing spatial scales. Our objective was to identify such controls on the occurrence of overland flow in a lowland tropical rainforest. To this end, we installed 95 overland flow detectors (OFDs) in four nested subcatchments of the Lutzito catchment on Barro Colorado Island, Panama, and monitored the frequency of overland flow occurrence during 18 rainfall events at each OFD location temporal frequency. For each such location, we derived three non-digital terrain attributes and 17 digital ones, of which 15 were based on Digital Elevation Models (DEMs) of three different resolutions. These attributes then served as input into a Random Forest ensemble tree model to elucidate the importance and partial and joint dependencies of topographic controls for overland flow occurrence. Lutzito features a high median temporal frequency in overland flow occurrence of 0.421 among OFD locations. However, spatial temporal frequencies of overland flow occurrence vary strongly among these locations and the subcatchments of Lutzito catchment. This variability is best explained by (1) microtopography, (2) coarse terrain sloping and (3) various measures of distance-to-channel, with the contribution of all other terrain attributes being small. Microtopographic features such as concentrated flowlines and wash areas produce highest temporal frequencies, whereas the occurrence of overland flow drops sharply for flow distances and terrain sloping beyond certain threshold values. Our study contributes to understanding both the spatial controls on overland flow generation and the limitations of terrain attributes for the spatially explicit prediction of overland flow frequencies.
MODELING AIR FLOW DYNAMICS IN RADON MITIGATION SYSTEMS: A SIMPLIFIED APPROACH
The paper refines and extends an earlier study--relating to the design of optimal radon mitigation systems based on subslab depressurization-- that suggested that subslab air flow induced by a central suction point be treated as radial air flow through a porous bed contained betw...
NASA Astrophysics Data System (ADS)
Margaris, Konstantinos N.; Nepiyushchikh, Zhanna; Zawieja, David C.; Moore, James; Black, Richard A.
2016-02-01
We describe the development of an optical flow visualization method for resolving the flow velocity vector field in lymphatic vessels in vitro. The aim is to develop an experimental protocol for accurately estimating flow parameters, such as flow rate and shear stresses, with high spatial and temporal resolution. Previous studies in situ have relied on lymphocytes as tracers, but their low density resulted in a reduced spatial resolution whereas the assumption that the flow was fully developed in order to determine the flow parameters of interest may not be valid, especially in the vicinity of the valves, where the flow is undoubtedly more complex. To overcome these issues, we have applied the time-resolved microparticle image velocimetry (μ-PIV) technique, a well-established method that can provide increased spatial and temporal resolution that this transient flow demands. To that end, we have developed a custom light source, utilizing high-power light-emitting diodes, and associated control and image processing software. This paper reports the performance of the system and the results of a series of preliminary experiments performed on vessels isolated from rat mesenteries, demonstrating, for the first time, the successful application of the μ-PIV technique in these vessels.
NASA Astrophysics Data System (ADS)
Yang, Jun; Chu, Xuefeng
2015-04-01
Realistic modeling of discontinuous overland flow on irregular topographic surfaces has been proven to be a challenge. This study is aimed to develop a new modeling framework to simulate the discontinuous puddle-to-puddle (P2P) overland flow dynamics for infiltrating surfaces with various microtopographic characteristics. In the P2P model, puddles were integrated in a well-delineated, cascaded drainage system to facilitate explicit simulation of their dynamic behaviors and interactions. Overland flow and infiltration were respectively simulated by using the diffusion wave model and a modified Green-Ampt model for the DEM-derived flow drainage network that consisted of a series of puddle-based units (PBUs). The P2P model was tested by using a series of data from laboratory overland flow experiments for various microtopography, soil, and rainfall conditions. The modeling results indicated that the hierarchical relationships and microtopographic properties of puddles significantly affected their connectivity, filling-spilling dynamics, and the associated threshold flow. Surface microtopography and rainfall characteristics also exhibited strong influences on the spatio-temporal distributions of infiltration rates, runoff fluxes, and unsaturated flow. The model tests demonstrated its applicability in simulating microtopography-dominated overland flow on infiltrating surfaces.
The Current Status of Unsteady CFD Approaches for Aerodynamic Flow Control
NASA Technical Reports Server (NTRS)
Carpenter, Mark H.; Singer, Bart A.; Yamaleev, Nail; Vatsa, Veer N.; Viken, Sally A.; Atkins, Harold L.
2002-01-01
An overview of the current status of time dependent algorithms is presented. Special attention is given to algorithms used to predict fluid actuator flows, as well as other active and passive flow control devices. Capabilities for the next decade are predicted, and principal impediments to the progress of time-dependent algorithms are identified.
Margaris, Konstantinos N; Nepiyushchikh, Zhanna; Zawieja, David C; Moore, James; Black, Richard A
2016-02-01
We describe the development of an optical flow visualization method for resolving the flow velocity vector field in lymphatic vessels in vitro. The aim is to develop an experimental protocol for accurately estimating flow parameters, such as flow rate and shear stresses, with high spatial and temporal resolution. Previous studies in situ have relied on lymphocytes as tracers, but their low density resulted in a reduced spatial resolution whereas the assumption that the flow was fully developed in order to determine the flow parameters of interest may not be valid, especially in the vicinity of the valves, where the flow is undoubtedly more complex. To overcome these issues, we have applied the time-resolved microparticle image velocimetry (μ -PIV) technique, a well-established method that can provide increased spatial and temporal resolution that this transient flow demands. To that end, we have developed a custom light source, utilizing high-power light-emitting diodes, and associated control and image processing software. This paper reports the performance of the system and the results of a series of preliminary experiments performed on vessels isolated from rat mesenteries, demonstrating, for the first time, the successful application of the μ -PIV technique in these vessels. PMID:26830061
NASA Astrophysics Data System (ADS)
Szemis, J. M.; Dandy, G. C.; Maier, H. R.
2013-10-01
In regulated river systems, such as the River Murray in Australia, the efficient use of water to preserve and restore biota in the river, wetlands, and floodplains is of concern for water managers. Available management options include the timing of river flow releases and operation of wetland flow control structures. However, the optimal scheduling of these environmental flow management alternatives is a difficult task, since there are generally multiple wetlands and floodplains with a range of species, as well as a large number of management options that need to be considered. Consequently, this problem is a multiobjective optimization problem aimed at maximizing ecological benefit while minimizing water allocations within the infrastructure constraints of the system under consideration. This paper presents a multiobjective optimization framework, which is based on a multiobjective ant colony optimization approach, for developing optimal trade-offs between water allocation and ecological benefit. The framework is applied to a reach of the River Murray in South Australia. Two studies are formulated to assess the impact of (i) upstream system flow constraints and (ii) additional regulators on this trade-off. The results indicate that unless the system flow constraints are relaxed, there is limited additional ecological benefit as allocation increases. Furthermore the use of regulators can increase ecological benefits while using less water. The results illustrate the utility of the framework since the impact of flow control infrastructure on the trade-offs between water allocation and ecological benefit can be investigated, thereby providing valuable insight to managers.
NASA Technical Reports Server (NTRS)
Hafez, M.; Soliman, M.; White, S.
1992-01-01
A new formulation (including the choice of variables, their non-dimensionalization, and the form of the artificial viscosity) is proposed for the numerical solution of the full Navier-Stokes equations for compressible and incompressible flows with heat transfer. With the present approach, the same code can be used for constant as well as variable density flows. The changes of the density due to pressure and temperature variations are identified and it is shown that the low Mach number approximation is a special case. At zero Mach number, the density changes due to the temperature variation are accounted for, mainly through a body force term in the momentum equation. It is also shown that the Boussinesq approximation of the buoyancy effects in an incompressible flow is a special case. To demonstrate the new capability, three examples are tested. Flows in driven cavities with adiabatic and isothermal walls are simulated with the same code as well as incompressible and supersonic flows over a wall with and without a groove. Finally, viscous flow simulations of an oblique shock reflection from a flat plate are shown to be in good agreement with the solutions available in literature.
NASA Astrophysics Data System (ADS)
de Jalon Diego, Garcia; de Jalon Silvestre, Garcia; Tanago Marta, Gonzalez
2015-04-01
In the last decades there has been a growing concern about water environmental costs. 'Polluter should pay' has been a phrase repeated in numerous policy-making processes. Water abstraction for Irrigation, Hydropower or water supply for Domestic or Industrial porpoises alters natural flow regimes impacting severely fluvial Ecosystems. The objective of this paper is to develop an evaluation of the marginal environmental costs for flow regulation. This approach is based on the idea 'who regulates flows should pay' and the amount to be paid should be proportional on the intensity, duration and frequency of the resulting regulated flows. The methodology proposed includes three separated steps: (i) estimating the natural flow regime of a river segment through studying the hydrologic conditions before the river is affected by a determined anthropogenic impact, (ii) assessing the hydrologic alteration of the river segment according to the estimated natural flow regime, and (iii) calculating marginal environmental costs of water supply. The three different case studies where the methodology was applied were the Esla River (Spain), the Upper River Tyne (England) and the Marna River (Norway).
NASA Astrophysics Data System (ADS)
Kaspi, Y.; Davighi, J. E.; Galanti, E.; Hubbard, W. B.
2016-09-01
The upcoming Juno and Cassini gravity measurements of Jupiter and Saturn, respectively, will allow probing the internal dynamics of these planets through accurate analysis of their gravity spectra. To date, two general approaches have been suggested for relating the flow velocities and gravity fields. In the first, barotropic potential surface models, which naturally take into account the oblateness of the planet, are used to calculate the gravity field. However, barotropicity restricts the flows to be constant along cylinders parallel to the rotation axis. The second approach, calculated in the reference frame of the rotating planet, assumes that due to the large scale and rapid rotation of these planets, the winds are to leading order in geostrophic balance. Therefore, thermal wind balance relates the wind shear to the density gradients. While this approach can take into account any internal flow structure, it is limited to only calculating the dynamical gravity contributions, and has traditionally assumed spherical symmetry. This study comes to relate the two approaches both from a theoretical perspective, showing that they are analytically identical in the barotropic limit, and numerically, through systematically comparing the different model solutions for the gravity harmonics. For the barotropic potential surface models we employ two independent solution methods - the potential-theory and Maclaurin spheroid methods. We find that despite the sphericity assumption, in the barotropic limit the thermal wind solutions match well the barotropic oblate potential-surface solutions.
Tardiole Kuehne, Bruno; Estrella, Julio Cezar; Nunes, Luiz Henrique; Martins de Oliveira, Edvard; Hideo Nakamura, Luis; Gomes Ferreira, Carlos Henrique; Carlucci Santana, Regina Helena; Reiff-Marganiec, Stephan; Santana, Marcos José
2015-01-01
This paper proposes a system named AWSCS (Automatic Web Service Composition System) to evaluate different approaches for automatic composition of Web services, based on QoS parameters that are measured at execution time. The AWSCS is a system to implement different approaches for automatic composition of Web services and also to execute the resulting flows from these approaches. Aiming at demonstrating the results of this paper, a scenario was developed, where empirical flows were built to demonstrate the operation of AWSCS, since algorithms for automatic composition are not readily available to test. The results allow us to study the behaviour of running composite Web services, when flows with the same functionality but different problem-solving strategies were compared. Furthermore, we observed that the influence of the load applied on the running system as the type of load submitted to the system is an important factor to define which approach for the Web service composition can achieve the best performance in production. PMID:26068216
NASA Astrophysics Data System (ADS)
Koppol, Anantha Padmanabha Rao
Flows of viscoelastic polymeric fluids are of great fundamental and practical interest as polymeric materials for commodity and value-added products are processed typically in a fluid state. The nonlinear coupling between fluid motion and microstructure, which results in highly non-Newtonian theology, memory/relaxation and normal stress development or tension along streamlines, greatly complicates the analysis, design and control of such flows. This has posed tremendous challenges to researchers engaged in developing first principles models and simulations that can accurately and robustly predict the dynamical behavior of polymeric flows. Despite this, the past two decades have witnessed several significant advances towards accomplishing this goal. Yet a problem of fundamental and great pragmatic interest has defied solution to years of ardent research by several groups, namely the relationship between friction drag and flow rate in inertialess flows of highly elastic polymer solutions in complex kinematics flows. First principles-based solution of this long-standing problem in non-Newtonian fluid mechanics is the goal of this research. To achieve our objective, it is essential to develop the capability to perform large-scale multiscale simulations, which integrate continuum-level finite element solvers for the conservation of mass and momentum with fast integrators of stochastic differential equations that describe the evolution of polymer configuration. Hence, in this research we have focused our attention on development of a parallel, multiscale simulation algorithm that is capable of robustly and efficiently simulating complex kinematics flows of dilute polymeric solutions using the first principles based bead-spring chain description of the polymer molecules. The fidelity and computational efficiency of the algorithm has been demonstrated via three benchmark flow problems, namely, the plane Couette flow, the Poiseuille flow and the 4:1:4 axisymmetric
Sonenshein, R.S.
1995-01-01
A hydrogeologic approach that integrates the use of hydrogeologic and spatial tools aids in the identification of land uses that overlie ground- water flow paths and permits a better understanding of ground-water flow systems. A mathematical model was used to simulate the ground-water flow system in Broward County, particle-tracking software was used to determine flow paths leading to the monitor wells in Broward County, and a Geographic Information System was used to identify which land uses overlie the flow paths. A procedure using a geographic information system to evaluate the output from a ground-water flow model has been documented. The ground-water flow model was used to represent steady-state conditions during selected wet- and dry-season months, and an advective flow particle- tracking program was used to simulate the direction of ground-water flow in the aquifer system. Digital spatial data layers were created from the particle pathlines that lead to the vicinity of the open interval of selected wells in the Broward County ground-water quality monitoring network. Buffer zone data layers were created, surrounding the particle pathlines to represent the area of contribution to the water sampled from the monitor wells. Spatial data layers, combined with a land-use data layer, were used to identify the land uses that overlie the ground-water flow paths leading to the monitor wells. The simulation analysis was performed on five Broward County wells with different hydraulic parameters to determine the source of ground-water stress, determine selected particle pathlines, and identify land use in buffer zones in the vicinity of the wells. The flow paths that lead to the grid cells containing wells G-2355, G-2373, and G-2373A did not vary between the wet- and dry-season conditions. Changes in the area of contribution for wells G-2345X and G-2369 were attributed to variations in rainfall patterns, well-field pumpage, and surface-water management practices
NASA Astrophysics Data System (ADS)
Cronkite-Ratcliff, C.; Phelps, G. A.; Boucher, A.
2011-12-01
In many geologic settings, the pathways of groundwater flow are controlled by geologic heterogeneities which have complex geometries. Models of these geologic heterogeneities, and consequently, their effects on the simulated pathways of groundwater flow, are characterized by uncertainty. Multiple-point geostatistics, which uses a training image to represent complex geometric descriptions of geologic heterogeneity, provides a stochastic approach to the analysis of geologic uncertainty. Incorporating multiple-point geostatistics into numerical models provides a way to extend this analysis to the effects of geologic uncertainty on the results of flow simulations. We present two case studies to demonstrate the application of multiple-point geostatistics to numerical flow simulation in complex geologic settings with both static and dynamic conditioning data. Both cases involve the development of a training image from a complex geometric description of the geologic environment. Geologic heterogeneity is modeled stochastically by generating multiple equally-probable realizations, all consistent with the training image. Numerical flow simulation for each stochastic realization provides the basis for analyzing the effects of geologic uncertainty on simulated hydraulic response. The first case study is a hypothetical geologic scenario developed using data from the alluvial deposits in Yucca Flat, Nevada. The SNESIM algorithm is used to stochastically model geologic heterogeneity conditioned to the mapped surface geology as well as vertical drill-hole data. Numerical simulation of groundwater flow and contaminant transport through geologic models produces a distribution of hydraulic responses and contaminant concentration results. From this distribution of results, the probability of exceeding a given contaminant concentration threshold can be used as an indicator of uncertainty about the location of the contaminant plume boundary. The second case study considers a
Constraining mantle flow with seismic and geodynamic data: A joint approach
NASA Astrophysics Data System (ADS)
Simmons, Nathan A.; Forte, Alessandro M.; Grand, Stephen P.
2006-06-01
Understanding the style of convective flow occurring in the mantle is essential to understand the thermal and chemical evolution of Earth's interior as well as the forces driving plate tectonics. Models of mantle convection based on three-dimensional (3-D) seismic tomographic reconstructions have the potential to provide the most direct constraints on mantle flow. Seismic imaging of deep Earth structure has made great advances in recent years; however, it has not been possible to reach a consensus on the nature of convection in the mantle. Models of mantle flow based on tomography results have yielded variable conclusions largely because of the inherent non-uniqueness and differing degrees of resolution of seismic tomography models as well as the difficulty in determining flow directly from seismic images. Here we address this difficulty by simultaneously inverting global seismic and convection-related data sets. The seismic data consist of globally distributed shear body wave travel times including multi-bounce S-waves, shallow-turning triplicated phases, as well as core reflections and phases traversing the core (SKS and SKKS). Convection-related data sets include global free air gravity, tectonic plate divergence, and excess ellipticity of the core-mantle boundary. In addition, the convection-related constraint on dynamic surface topography is estimated on the basis of a recent global model of crustal heterogeneity. These convection-related observables are related to mantle density anomalies through instantaneous mantle flow calculations and linked to the seismic data via optimized density-velocity scaling relationships. Simultaneous inversion allows us to test various mantle flow hypotheses directly against the combined seismic and convection data sets, rather than considering flow predictions based solely on a seismically derived 3-D mantle model. In this study, we test four different mantle flow hypotheses, including whole-mantle flow and models with
Modelling isothermal bubbly-cap flows using two-group averaged bubble number density approach
NASA Astrophysics Data System (ADS)
Cheung, S. C. P.; Yeoh, G. H.; Tu, J. Y.
2012-09-01
Gas-liquid flows with wide range of bubble sizes are commonly encountered in many nuclear gas-liquid flow systems. In tracking the changes of gas volume fraction and bubble size distribution under complex flow conditions, numerical studies have been performed to predict the temporal and spatial evolution of two-phase geometrical structure caused by the effects of bubble interactions in gas-liquid flows. Within literatures, the development of most coalescence and break-up mechanisms were primarily focused on the interaction of spherical bubbles. Nevertheless, cap bubbles which are precursors to the formation of slug units in the slug flow regime with increasing volume fraction become ever more prevalent at high gas velocity conditions. It has been shown through many experiments that interaction behaviors between non-spherical bubbles in a liquid flow are remarkably different when compared to those of spherical bubbles. Based on the computational fluid dynamics (CFD) framework, a three-fluid model was solved, one set of conservation equations for the liquid phase while two sets of conservation equations for the gas phase with one being Group 1 spherical bubbles and the other depicting Group 2 cap bubbles. In this initial assessment, the bubble mechanistic models proposed by Hibiki and Ishii [1] have been adopted to describe the intra-group and inter-group interactions. The numerical predictions were evaluated against the experiment data of the TOPFLOW facility for vertical, upwards, airwater flows in a large pipe diameter [2].
A combined experimental-numerical approach for two-phase flow boiling in a minichannel
NASA Astrophysics Data System (ADS)
Hożejowska, Sylwia; Grabowski, Mirosław
2016-03-01
The paper addresses experimental and numerical modeling of the two-phase flows in an asymmetrically heated horizontal minichannel. Experimental measurements concerned flows of evaporating ethanol in a minichannel with rectangular cross section 1.8mm × 2 mm. In order to observe the flows, measuring system was designed and built. The system measured and recorded basic heat and flow parameters of flowing fluid, and the temperature of external surface of the heater by using infrared camera and recorded images of flow with high-speed camera. The second aim of the paper was to formulate appropriate flow boiling heat transfer model, which would minimises the use of experimentally determined constants. The procedure of calculating the temperature of the ethanol is coupled with concurrent process of determining the temperature distributions in the isolating foil and the heating surface. The two-dimensional temperature distributions in three subsequent domains were calculated with Trefftz method. Due to the Robin condition, heat transfer coefficient at the heating surface-ethanol interface was calculated based on the known temperature distributions of the foil and liquid. Additionally, the paper describes the relation between two sets of functions used in the calculation. Numerical calculations made by Trefftz method were performed with using experimental data.
NASA Astrophysics Data System (ADS)
Brown, S. R.; Kang, P. K.; Zheng, Y.; Fang, X.; Fehler, M. C.; Burns, D.; Juanes, R.
2013-12-01
Characterizing fractured geologic formations is essential in exploration geophysics, petroleum engineering, and in the assessment of deep geologic nuclear waste disposal. Traditionally, seismic interpretation and flow modeling have been performed independently, typically following a unidirectional workflow. Here, we present a methodology to characterize fractured geologic media by integrating flow and seismic data. The goal of our work is twofold: on one hand, reduce that uncertainty by incorporating dynamic flow measurements into the seismic interpretation; on the other, improve the predictability of groundwater flow and transport models by making joint use of seismic and flow data. The basic tenet of our proposed framework is that there is a strong dependence between fracture permeability (which drives the flow response) and fracture compliance (which drives the seismic response). This connection has long been recognized [1], and recent works have pointed to the potential of exploiting that connection [2-3]. By means of synthetic models, we show that: (1) owing to the strong (but highly uncertain) dependence of fracture permeability on fracture compliance, the modeled flow response in a fractured reservoir is highly sensitive to the geophysical interpretation; and (2) by incorporating flow data (well pressures and production curves) into the inversion workflow, we can simultaneously reduce the error in the seismic interpretation and improve predictions of the reservoir flow dynamics. [1] L. J. Pyrak-Nolte and J. P. Morris, Int. J. Rock. Mech. Min. 37, 245 (2000). [2] S. Brown and X. Fang, SEG Technical Program Expanded Abstracts , 1 (2012). [3] C. L. Petrovitch, L. J. Pyrak-Nolte, and D. D. Nolte, Geophys. Res. Lett. (2013).
A Renormalization-Group Approach of the Up-Scaling Problem of Flow in Heterogeneous Porous Media
NASA Astrophysics Data System (ADS)
noetinger, B.
2001-12-01
Powerful methods coming from statistical physics are becoming increasingly popular to get a faithful theoretical description of flow and transport in heterogeneous aquifers that are described by mean of geostatistics. However,in current practice people still use Monte Carlo simulations that are well suited to account for complex boundaries and flow patterns. Here, we present an approach intending to up-scale directly the geostatistical description rather than realization by realization as usual. It is based upon a renormalization group analysis close in spirit with previous works and P King and Jaekel and Vereecken. Using a so called "weak approximation"(Neuman and Orr) , we obtain differential equations driving the permeability variogram parameters as a function of the wave-vector cut-off smoothing the permeability maps. At the end of the process, in the isotropic case, the Landau Lifshitz Matheron conjecture is recovered. This conjecture appears thus as being a consequence of both renormalization approach and the weak approximation. The approach is currently being generalized to anisotropic media. These results can be used to perform cheaper Monte Carlo simulations at a coarser scale. P. King, The Use of Field Theoretic Methods for the Study of Flow in Heterogeneous Porous Medium", J. Phys. A.: Math. Gen. 20, pp3935-3947,1987 U. Jaekel and H. Vereecken, Renormalization Group Analysis of Macrodispersion in a Directed Random Flow, Water Resources Research,33,10,pp 2287-2299, 1997 Neuman, S.P. and Orr, S. "Prediction of Steady State Flow in Nonuniform Geologic Media by Conditional Moments: Exact non local Formalism, Effective Conductivities and Weak Approximation", Water Resources Research 29 (2)341-364 (1993) Noetinger, B. Computing the Effective Permeability of log-normal permeability fields using renormalization methods. C.R . Acad. Des Sciences,Sciences de la Terre et des Planètes, 331 353-357 (2000)
A unified approach to fluid-flow, geomechanical, and seismic modelling
NASA Astrophysics Data System (ADS)
Yarushina, Viktoriya; Minakov, Alexander
2016-04-01
The perturbations of pore pressure can generate seismicity. This is supported by observations from human activities that involve fluid injection into rocks at high pressure (hydraulic fracturing, CO2 storage, geothermal energy production) and natural examples such as volcanic earthquakes. Although the seismic signals that emerge during geotechnical operations are small both in amplitude and duration when compared to natural counterparts. A possible explanation for the earthquake source mechanism is based on a number of in situ stress measurements suggesting that the crustal rocks are close to its plastic yield limit. Hence, a rapid increase of the pore pressure decreases the effective normal stress, and, thus, can trigger seismic shear deformation. At the same time, little attention has been paid to the fact that the perturbation of fluid pressure itself represents an acoustic source. Moreover, non-double-couple source mechanisms are frequently reported from the analysis of microseismicity. A consistent formulation of the source mechanism describing microseismic events should include both a shear and isotropic component. Thus, improved understanding of the interaction between fluid flow and seismic deformation is needed. With this study we aim to increase the competence in integrating real-time microseismic monitoring with geomechanical modelling such that there is a feedback loop between monitored deformation and stress field modelling. We propose fully integrated seismic, geomechanical and reservoir modelling. Our mathematical formulation is based on fundamental set of force balance, mass balance, and constitutive poro-elastoplastic equations for two-phase media consisting of deformable solid rock frame and viscous fluid. We consider a simplified 1D modelling setup for consistent acoustic source and wave propagation in poro-elastoplastic media. In this formulation the seismic wave is generated due to local changes of the stress field and pore pressure induced by
Bryce, Steven M; Bernacki, Derek T; Bemis, Jeffrey C; Dertinger, Stephen D
2016-04-01
Several endpoints associated with cellular responses to DNA damage as well as overt cytotoxicity were multiplexed into a miniaturized, "add and read" type flow cytometric assay. Reagents included a detergent to liberate nuclei, RNase and propidium iodide to serve as a pan-DNA dye, fluorescent antibodies against γH2AX, phospho-histone H3, and p53, and fluorescent microspheres for absolute nuclei counts. The assay was applied to TK6 cells and 67 diverse reference chemicals that served as a training set. Exposure was for 24 hrs in 96-well plates, and unless precipitation or foreknowledge about cytotoxicity suggested otherwise, the highest concentration was 1 mM. At 4- and 24-hrs aliquots were removed and added to microtiter plates containing the reagent mix. Following a brief incubation period robotic sampling facilitated walk-away data acquisition. Univariate analyses identified biomarkers and time points that were valuable for classifying agents into one of three groups: clastogenic, aneugenic, or non-genotoxic. These mode of action predictions were optimized with a forward-stepping process that considered Wald test p-values, receiver operator characteristic curves, and pseudo R(2) values, among others. A particularly high performing multinomial logistic regression model was comprised of four factors: 4 hr γH2AX and phospho-histone H3 values, and 24 hr p53 and polyploidy values. For the training set chemicals, the four-factor model resulted in 94% concordance with our a priori classifications. Cross validation occurred via a leave-one-out approach, and in this case 91% concordance was observed. A test set of 17 chemicals that were not used to construct the model were evaluated, some of which utilized a short-term treatment in the presence of a metabolic activation system, and in 16 cases mode of action was correctly predicted. These initial results are encouraging as they suggest a machine learning strategy can be used to rapidly and reliably predict new chemicals
Collective flow in event-by-event partonic transport plus hydrodynamics hybrid approach
NASA Astrophysics Data System (ADS)
Bhalerao, Rajeev S.; Jaiswal, Amaresh; Pal, Subrata
2015-07-01
Complete evolution of the strongly interacting matter formed in ultrarelativistic heavy-ion collisions is studied within a coupled Boltzmann and relativistic viscous hydrodynamics approach. For the initial nonequilibrium evolution phase, we employ a multiphase transport (AMPT) model that explicitly includes event-by-event fluctuations in the number and positions of the participating nucleons as well as of the produced partons with subsequent parton transport. The ensuing near-equilibrium evolution of quark-gluon and hadronic matter is modeled within the (2 +1 ) -dimensional relativistic viscous hydrodynamics. We probe the role of parton dynamics in generating and maintaining the spatial anisotropy in the preequilibrium phase. Substantial spatial eccentricities ɛn are found to be generated in the event-by-event fluctuations in parton production from initial nucleon-nucleon collisions. For ultracentral heavy-ion collisions, the model is able to explain qualitatively the unexpected hierarchy of the harmonic flow coefficients vn(pT) (n =2 -6 ) observed at energies currently available at the CERN Large Hadron Collider (LHC). We find that the results for vn(pT) are rather insensitive to the variation (within a range) of the time of switchover from AMPT parton transport to hydrodynamic evolution. The usual Grad and the recently proposed Chapman-Enskog-like (nonequilibrium) single-particle distribution functions are found to give very similar results for vn(n =2 -4 ) . The model describes well both the BNL Relativistic Heavy Ion Collider and LHC data for vn(pT) at various centralities, with a constant shear viscosity to entropy density ratio of 0.08 and 0.12, respectively. The event-by-event distributions of v2 ,3 are in good agreement with the LHC data for midcentral collisions. The linear response relation vn=knɛn is found to be true for n =2 ,3 , except at large values of ɛn, where a larger value of kn is required, suggesting a small admixture of positive nonlinear
An analysis of the viscous flow through a compact radial turbine by the average passage approach
NASA Technical Reports Server (NTRS)
Heidmann, James D.; Beach, Timothy A.
1990-01-01
A steady, three-dimensional viscous average passage computer code is used to analyze the flow through a compact radial turbine rotor. The code models the flow as spatially periodic from blade passage to blade passage. Results from the code using varying computational models are compared with each other and with experimental data. These results include blade surface velocities and pressures, exit vorticity and entropy contour plots, shroud pressures, and spanwise exit total temperature, total pressure, and swirl distributions. The three computational models used are inviscid, viscous with no blade clearance, and viscous with blade clearance. It is found that modeling viscous effects improves correlation with experimental data, while modeling hub and tip clearances further improves some comparisons. Experimental results such as a local maximum of exit swirl, reduced exit total pressures at the walls, and exit total temperature magnitudes are explained by interpretation of the flow physics and computed secondary flows. Trends in the computed blade loading diagrams are similarly explained.
Limits of the potential flow approach to the single-mode Rayleigh-Taylor problem.
Ramaprabhu, P; Dimonte, Guy; Young, Yuan-Nan; Calder, A C; Fryxell, B
2006-12-01
We report on the behavior of a single-wavelength Rayleigh-Taylor flow at late times. The calculations were performed in a long square duct (lambda x lambda x 8lambda), using four different numerical simulations. In contradiction with potential flow theories that predict a constant terminal velocity, the single-wavelength Rayleigh-Taylor problem exhibits late-time acceleration. The onset of acceleration occurs as the bubble penetration depth exceeds the diameter of bubbles, and is observed for low and moderate density differences. Based on our simulations, we provide a phenomenological description of the observed acceleration, and ascribe this behavior to the formation of Kelvin-Helmholtz vortices on the bubble-spike interface that diminish the friction drag, while the associated induced flow propels the bubbles forward. For large density ratios, the formation of secondary instabilities is suppressed, and the bubbles remain terminal consistent with potential flow models. PMID:17280149
NASA Astrophysics Data System (ADS)
de Castro, Marcelo Souza; Rodriguez, Oscar Mauricio Hernandez
2016-06-01
The study of the hydrodynamic stability of flow patterns is important in the design of equipment and pipelines for multiphase flows. The maintenance of a particular flow pattern becomes important in many applications, e.g., stratified flow pattern in heavy oil production avoiding the formation of emulsions because of the separation of phases and annular flow pattern in heat exchangers which increases the heat transfer coefficient. Flow maps are drawn to orientate engineers which flow pattern is present in a pipeline, for example. The ways how these flow maps are drawn have changed from totally experimental work, to phenomenological models, and then to stability analysis theories. In this work an experimental liquid-liquid flow map, with water and viscous oil as work fluids, drawn via subjective approach with high speed camera was used to compare to approaches of the same theory: the interfacial-tension-force model. This theory was used to drawn the wavy stratified flow pattern transition boundary. This paper presents a comparison between the two approaches of the interfacial-tension-force model for transition boundaries of liquid-liquid flow patterns: (i) solving the wave equation for the wave speed and using average values for wave number and wave speed; and (ii) solving the same equation for the wave number and then using a correlation for the wave speed. The results show that the second approach presents better results.
Computational approach to estimating the effects of blood properties on changes in intra-stent flow.
Benard, Nicolas; Perrault, Robert; Coisne, Damien
2006-08-01
In this study various blood rheological assumptions are numerically investigated for the hemodynamic properties of intra-stent flow. Non-newtonian blood properties have never been implemented in blood coronary stented flow investigation, although its effects appear essential for a correct estimation and distribution of wall shear stress (WSS) exerted by the fluid on the internal vessel surface. Our numerical model is based on a full 3D stent mesh. Rigid wall and stationary inflow conditions are applied. Newtonian behavior, non-newtonian model based on Carreau-Yasuda relation and a characteristic newtonian value defined with flow representative parameters are introduced in this research. Non-newtonian flow generates an alteration of near wall viscosity norms compared to newtonian. Maximal WSS values are located in the center part of stent pattern structure and minimal values are focused on the proximal stent wire surface. A flow rate increase emphasizes fluid perturbations, and generates a WSS rise except for interstrut area. Nevertheless, a local quantitative analysis discloses an underestimation of WSS for modelisation using a newtonian blood flow, with clinical consequence of overestimate restenosis risk area. Characteristic viscosity introduction appears to present a useful option compared to rheological modelisation based on experimental data, with computer time gain and relevant results for quantitative and qualitative WSS determination. PMID:16799830
NASA Astrophysics Data System (ADS)
Dalzell, B. J.; Gassman, P. W.; Kling, C.
2015-12-01
In the Minnesota River Basin, sediments originating from failing stream banks and bluffs account for the majority of the riverine load and contribute to water quality impairments in the Minnesota River as well as portions of the Mississippi River upstream of Lake Pepin. One approach for mitigating this problem may be targeted wetland restoration in Minnesota River Basin tributaries in order to reduce the magnitude and duration of peak flow events which contribute to bluff and stream bank failures. In order to determine effective arrangements and properties of wetlands to achieve peak flow reduction, we are employing a genetic algorithm approach coupled with a SWAT model of the Cottonwood River, a tributary of the Minnesota River. The genetic algorithm approach will evaluate combinations of basic wetland features as represented by SWAT: surface area, volume, contributing area, and hydraulic conductivity of the wetland bottom. These wetland parameters will be weighed against economic considerations associated with land use trade-offs in this agriculturally productive landscape. Preliminary results show that the SWAT model is capable of simulating daily hydrology very well and genetic algorithm evaluation of wetland scenarios is ongoing. Anticipated results will include (1) combinations of wetland parameters that are most effective for reducing peak flows, and (2) evaluation of economic trade-offs between wetland restoration, water quality, and agricultural productivity in the Cottonwood River watershed.
Marassi, V; Roda, B; Zattoni, A; Tanase, M; Reschiglian, P
2014-10-30
Monoclonal antibodies (mAbs) are promising reagents both for the manufacture of drug substances and for their employment as a drug themselves, but to be approved for utilization, according to FDA recommendations and WHO guidelines, they have to undergo verifications regarding their purity, stability and percentage of aggregates. Moreover, stability tests of lots have to be performed in order to verify molecular size distribution over time and lot-to-lot consistency. Recent works in literature have highlighted the need for suitable, sensitive and reliable complementary analytical techniques for the characterization of mAbs and quantification of aggregates. Size-exclusion chromatography (SEC) is the reference technique in the biopharmaceutical industry for its robustness, high performance and simple use; however it presents some limitations especially toward the separation and detection of aggregates with high molecular weight. On the other hand, flow field-flow fractionation (F4) in its miniaturized version (hollow fiber flow field-flow fractionation, HF5) shows comparable performances with interesting additional advantages: a broad size range, gentle separation mechanism with low dilution factor and higher sensitivity. To propose HF5 as a complementary technique for evaluating aggregates' content in mAbs samples, a comparative study of both SEC and HF5 performances has been made. In this work, SEC and HF5 were coupled with UV and multi-angle light scattering detection and employed first in separating standard samples of proteins mixture used as a sample model. Then, a screening of mobile phases and an evaluation of separation performances was performed on a therapeutic mAbs formulation, demonstrating the complementarities between SEC and HF5 and their possible use as a separative platform approach for the characterization and quality control of protein drugs. PMID:25468501
Free surface flow through rock-fill dams analyzed by FEM with level set approach
NASA Astrophysics Data System (ADS)
Sharif, N. H.; Wiberg, N.-E.; Levenstam, M.
A stabilized-finite element formulation is coupled with a level set technique for computations of incompressible non-linear flow with interfaces between two immiscible fluids. An interface capturing formulation (ICF) for non-linear, free surface, seepage flow in rock-fill dams is proposed. The formulation is derived for two- and three-dimensional flow within a fixed mesh domain. The resulting formulation is general and applicable for various steady and transient two-phase flow problems. FE-refinement is processed for the entire fixed mesh domains. A general solver is also reviewed for large and non-symmetric non-positive definite linear system of equations with the GMRES-update technique based on a Newton-iterative method. The computational procedure has been implemented in MATLAB. A comparison is performed between the 2-D computed test problem for coarse and refined meshes together with some proposed analytical solutions for nonlinear seepage flow with free surface in rock-fill dams. An expansion of the 2-D program code to a 3-D one for a rectangular rock-fill dam is also developed and simulated in MATLAB. The performance of the computations in 3-D is very promising and its opening the future for possible industrial applications using the same simple technique. Computations for a simple 3-D seepage flow problem with free surface in rock-fill dam are included in present paper. A general mesh generator and solver for large scale and complex 3-D flow problems in a real embankment dam is also under construction in C++.
NASA Astrophysics Data System (ADS)
Riasi, M. S.; Huang, G.; Montemagno, C.; Yeghiazarian, L.
2014-12-01
Micro-scale modeling of multiphase flow in porous media is critical to characterize porous materials. Several modeling techniques have been implemented to date, but none can be used as a general strategy for all porous media applications due to challenges presented by non-smooth high-curvature and deformable solid surfaces, and by a wide range of pore sizes and porosities. Finite approaches like the finite volume method require a high quality, problem-dependent mesh, while particle-based approaches like the lattice Boltzmann require too many particles to achieve a stable meaningful solution. Both come at a large computational cost. Other methods such as pore network modeling (PNM) have been developed to accelerate the solution process by simplifying the solution domain, but so far a unique and straightforward methodology to implement PNM is lacking. Pore topology method (PTM) is a new topologically consistent approach developed to simulate multiphase flow in porous media. The core of PTM is to reduce the complexity of the 3-D void space geometry by working with its medial surface as the solution domain. Medial surface is capable of capturing all the corners and surface curvatures in a porous structure, and therefore provides a topologically consistent representative geometry for porous structure. Despite the simplicity and low computational cost, PTM provides a fast and straightforward approach for micro-scale modeling of fluid flow in all types of porous media irrespective of their porosity and pore size distribution. In our previous work, we developed a non-iterative fast medial surface finder algorithm to determine a voxel-wide medial surface of the void space of porous media as well as a set of simple rules to determine the capillary pressure-saturation curves for a porous system assuming quasi-static two-phase flow with a planar w-nw interface. Our simulation results for a highly porous fibrous material and polygonal capillary tubes were in excellent agreement
NASA Astrophysics Data System (ADS)
Jomelli, Vincent; Pavlova, Irina; Eckert, Nicolas; Grancher, Delphine; Brunstein, Daniel
2015-12-01
How can debris flow occurrences be modelled at regional scale and take both environmental and climatic conditions into account? And, of the two, which has the most influence on debris flow activity? In this paper, we try to answer these questions with an innovative Bayesian hierarchical probabilistic model that simultaneously accounts for how debris flows respond to environmental and climatic variables. In it, full decomposition of space and time effects in occurrence probabilities is assumed, revealing an environmental and a climatic trend shared by all years/catchments, respectively, clearly distinguished from residual "random" effects. The resulting regional and annual occurrence probabilities evaluated as functions of the covariates make it possible to weight the respective contribution of the different terms and, more generally, to check the model performances at different spatio-temporal scales. After suitable validation, the model can be used to make predictions at undocumented sites and could be used in further studies for predictions under future climate conditions. Also, the Bayesian paradigm easily copes with missing data, thus making it possible to account for events that may have been missed during surveys. As a case study, we extract 124 debris flow event triggered between 1970 and 2005 in 27 catchments located in the French Alps from the French national natural hazard survey and model their variability of occurrence considering environmental and climatic predictors at the same time. We document the environmental characteristics of each debris flow catchment (morphometry, lithology, land cover, and the presence of permafrost). We also compute 15 climate variables including mean temperature and precipitation between May and October and the number of rainy days with daily cumulative rainfall greater than 10/15/20/25/30/40 mm day- 1. Application of our model shows that the combination of environmental and climatic predictors explained 77% of the overall
Kinetics-based phase change approach for VOF method applied to boiling flow
NASA Astrophysics Data System (ADS)
Cifani, Paolo; Geurts, Bernard; Kuerten, Hans
2014-11-01
Direct numerical simulations of boiling flows are performed to better understand the interaction of boiling phenomena with turbulence. The multiphase flow is simulated by solving a single set of equations for the whole flow field according to the one-fluid formulation, using a VOF interface capturing method. Interface terms, related to surface tension, interphase mass transfer and latent heat, are added at the phase boundary. The mass transfer rate across the interface is derived from kinetic theory and subsequently coupled with the continuum representation of the flow field. The numerical model was implemented in OpenFOAM and validated against 3 cases: evaporation of a spherical uniformly heated droplet, growth of a spherical bubble in a superheated liquid and two dimensional film boiling. The computational model will be used to investigate the change in turbulence intensity in a fully developed channel flow due to interaction with boiling heat and mass transfer. In particular, we will focus on the influence of the vapor bubble volume fraction on enhancing heat and mass transfer. Furthermore, we will investigate kinetic energy spectra in order to identify the dynamics associated with the wakes of vapor bubbles. Department of Applied Mathematics, 7500 AE Enschede, NL.
NASA Astrophysics Data System (ADS)
Liu, Zhongqiu; Li, Linmin; Qi, Fengsheng; Li, Baokuan; Jiang, Maofa; Tsukihashi, Fumitaka
2015-02-01
A population balance model based on the multiple-size-group (MUSIG) approach has been developed to investigate the polydispersed bubbly flow inside the slab continuous-casting mold and bubble behavior including volume fraction, breakup, coalescence, and size distribution. The Eulerian-Eulerian approach is used to describe the equations of motion of the two-phase flow. All the non-drag forces (lift force, virtual mass force, wall lubrication force, and turbulent dispersion force) and drag force are incorporated in this model. Sato and Sekiguchi model is used to account for the bubble-induced turbulence. Luo and Svendsen model and Prince and Blanch model are used to describe the bubbles breakup and coalescence behavior, respectively. A 1/4th water model of the slab continuous-casting mold was applied to investigate the distribution and size of bubbles by injecting air through a circumferential inlet chamber which was made of the specially-coated samples of mullite porous brick, which is used for the actual upper nozzle. Against experimental data, numerical results showed good agreement for the gas volume fraction and local bubble Sauter mean diameter. The bubble Sauter mean diameter in the upper recirculation zone decreases with increasing water flow rate and increases with increasing gas flow rate. The distribution of bubble Sauter mean diameter along the width direction of the upper mold increases first, and then gradually decreases from the SEN to the narrow wall. Close agreements between the predictions and measurements demonstrate the capability of the MUSIG model in modeling bubbly flow inside the continuous-casting mold.
NASA Astrophysics Data System (ADS)
Wagenbrenner, N. S.; Forthofer, J.; Butler, B.; Shannon, K.
2014-12-01
Near-surface wind predictions are important for a number of applications, including transport and dispersion, wind energy forecasting, and wildfire behavior. Researchers and forecasters would benefit from a wind model that could be readily applied to complex terrain for use in these various disciplines. Unfortunately, near-surface winds in complex terrain are not handled well by traditional modeling approaches. Numerical weather prediction models employ coarse horizontal resolutions which do not adequately resolve sub-grid terrain features important to the surface flow. Computational fluid dynamics (CFD) models are increasingly being applied to simulate atmospheric boundary layer (ABL) flows, especially in wind energy applications; however, the standard functionality provided in commercial CFD models is not suitable for ABL flows. Appropriate CFD modeling in the ABL requires modification of empirically-derived wall function parameters and boundary conditions to avoid erroneous streamwise gradients due to inconsistences between inlet profiles and specified boundary conditions. This work presents a new version of a near-surface wind model for complex terrain called WindNinja. The new version of WindNinja offers two options for flow simulations: 1) the native, fast-running mass-consistent method available in previous model versions and 2) a CFD approach based on the OpenFOAM modeling framework and optimized for ABL flows. The model is described and evaluations of predictions with surface wind data collected from two recent field campaigns in complex terrain are presented. A comparison of predictions from the native mass-consistent method and the new CFD method is also provided.
NASA Astrophysics Data System (ADS)
Liu, Zhongqiu; Li, Linmin; Qi, Fengsheng; Li, Baokuan; Jiang, Maofa; Tsukihashi, Fumitaka
2014-09-01
A population balance model based on the multiple-size-group (MUSIG) approach has been developed to investigate the polydispersed bubbly flow inside the slab continuous-casting mold and bubble behavior including volume fraction, breakup, coalescence, and size distribution. The Eulerian-Eulerian approach is used to describe the equations of motion of the two-phase flow. All the non-drag forces (lift force, virtual mass force, wall lubrication force, and turbulent dispersion force) and drag force are incorporated in this model. Sato and Sekiguchi model is used to account for the bubble-induced turbulence. Luo and Svendsen model and Prince and Blanch model are used to describe the bubbles breakup and coalescence behavior, respectively. A 1/4th water model of the slab continuous-casting mold was applied to investigate the distribution and size of bubbles by injecting air through a circumferential inlet chamber which was made of the specially-coated samples of mullite porous brick, which is used for the actual upper nozzle. Against experimental data, numerical results showed good agreement for the gas volume fraction and local bubble Sauter mean diameter. The bubble Sauter mean diameter in the upper recirculation zone decreases with increasing water flow rate and increases with increasing gas flow rate. The distribution of bubble Sauter mean diameter along the width direction of the upper mold increases first, and then gradually decreases from the SEN to the narrow wall. Close agreements between the predictions and measurements demonstrate the capability of the MUSIG model in modeling bubbly flow inside the continuous-casting mold.
Lagrangian approach to modeling unsteady gas-liquid flow in a well
NASA Astrophysics Data System (ADS)
Liapidevskii, V. Yu; Tikhonov, V.
2016-06-01
The purpose of this paper is to develop a numerical method of solving the problem of evolution of the finite gas volume that entered in a liquid flow at a set flow rate. The drift- flux model is used as gas-liquid mixture equations. The velocities of both phases, mixture and gas, are related by the Zuber-Findlay equation which coefficients depend on flow regime and gas void fraction. Lagrangian coordinates are used to simplify the initial equations. The numerical solution scheme is proposed. The numerical solution of the Riemann problem is verified by comparison with the exact self-similar solution. The model and numerical method efficiency is illustrated by examples of gas kick calculations in a vertical well.
A fully coupled porous flow and geomechanics model for fluid driven cracks: a peridynamics approach
NASA Astrophysics Data System (ADS)
Ouchi, Hisanao; Katiyar, Amit; York, Jason; Foster, John T.; Sharma, Mukul M.
2015-03-01
A state-based non-local peridynamic formulation is presented for simulating fluid driven fractures in an arbitrary heterogeneous poroelastic medium. A recently developed peridynamic formulation of porous flow has been coupled with the existing peridynamic formulation of solid and fracture mechanics resulting in a peridynamic model that for the first time simulates poroelasticity and fluid-driven fracture propagation. This coupling is achieved by modeling the role of pore pressure on the deformation of porous media and vice versa through porosity variation with medium deformation, pore pressure and total mean stress. The poroelastic model is verified by simulating the one-dimensional consolidation of fluid saturated rock. An additional porous flow equation with material permeability dependent on fracture width is solved to simulate fluid flow in the fractured region. Finally, single fluid-driven fracture propagation with a two-dimensional plane strain assumption is simulated and verified against the corresponding classical analytical solution.
Ötvös, Sándor B; Mándity, István M; Fülöp, Ferenc
2011-08-01
A simple and efficient flow-based technique is reported for the catalytic deuteration of several model nitrogen-containing heterocyclic compounds which are important building blocks of pharmacologically active materials. A continuous flow reactor was used in combination with on-demand pressure-controlled electrolytic D(2) production. The D(2) source was D(2)O, the consumption of which was very low. The experimental set-up allows the fine-tuning of pressure, temperature, and flow rate so as to determine the optimal conditions for the deuteration reactions. The described procedure lacks most of the drawbacks of the conventional batch deuteration techniques, and additionally is highly selective and reproducible. PMID:20842527
Flow rate estimation by optical coherence tomography using contrast dilution approach
NASA Astrophysics Data System (ADS)
Štohanzlová, Petra; Kolář, Radim
2015-07-01
This paper describes experiments and methodology for flow rate estimation using optical coherence tomography and dilution method in single fiber setup. The single fiber is created from custom made glass capillary and polypropylene hollow fiber. As a data source, measurements on single fiber phantom with continuous flow of carrier medium and bolus of Intralipid solution as a contrast agent were used using Thorlabs OCT OCS1300SS. The measured data were processed by methods of image processing, in order to precisely align the individual images in the sequence and extract dilution curves from the area inside the fiber. An experiment proved that optical coherence tomography can be used for flow rate estimation by the dilution method with precision around 7%.
NASA Astrophysics Data System (ADS)
Li, Shouju; Li, De; Cao, Lijuan; Shangguan, Zichang
2015-02-01
Particle flow code (PFC) is widely used to model deformation and stress states of rockfill materials. The accuracy of numerical modeling with PFC is dependent upon the model parameter values. How to accurately determine model parameters remains one of the main challenges. In order to determine model parameters of particle flow model of rockfill materials, some triaxial compression experiments are performed, and the inversion procedure of model parameters based on response surface method is proposed. Parameters of particle flow model of rockfill materials are determined according to the observed data in triaxial compression tests for rockfill materials. The investigation shows that the normal stiffness, tangent stiffness and friction coefficient of rockfill materials will slightly increase with increase of confining pressure in triaxial compression tests. The experiments in laboratory show that the proposed inversion procedure behaves higher computing efficiency and the forecasted stress-strain relations agree well with observed values.
Cooperativity flows and shear-bandings: a statistical field theory approach.
Benzi, R; Sbragaglia, M; Bernaschi, M; Succi, S; Toschi, F
2016-01-14
Cooperativity effects have been proposed to explain the non-local rheology in the dynamics of soft jammed systems. Based on the analysis of the free-energy model proposed by L. Bocquet, A. Colin and A. Ajdari, Phys. Rev. Lett., 2009, 103, 036001, we show that cooperativity effects resulting from the non-local nature of the fluidity (inverse viscosity) are intimately related to the emergence of shear-banding configurations. This connection materializes through the onset of inhomogeneous compact solutions (compactons), wherein the fluidity is confined to finite-support subregions of the flow and strictly zero elsewhere. The compacton coexistence with regions of zero fluidity ("non-flowing vacuum") is shown to be stabilized by the presence of mechanical noise, which ultimately shapes up the equilibrium distribution of the fluidity field, the latter acting as an order parameter for the flow-noflow transitions occurring in the material. PMID:26486875
An Approach to the Constrained Design of Natural Laminar Flow Airfoils
NASA Technical Reports Server (NTRS)
Green, Bradford E.
1997-01-01
A design method has been developed by which an airfoil with a substantial amount of natural laminar flow can be designed, while maintaining other aerodynamic and geometric constraints. After obtaining the initial airfoil's pressure distribution at the design lift coefficient using an Euler solver coupled with an integral turbulent boundary layer method, the calculations from a laminar boundary layer solver are used by a stability analysis code to obtain estimates of the transition location (using N-Factors) for the starting airfoil. A new design method then calculates a target pressure distribution that will increase the laminar flow toward the desired amount. An airfoil design method is then iteratively used to design an airfoil that possesses that target pressure distribution. The new airfoil's boundary layer stability characteristics are determined, and this iterative process continues until an airfoil is designed that meets the laminar flow requirement and as many of the other constraints as possible.
An approach to the constrained design of natural laminar flow airfoils
NASA Technical Reports Server (NTRS)
Green, Bradford Earl
1995-01-01
A design method has been developed by which an airfoil with a substantial amount of natural laminar flow can be designed, while maintaining other aerodynamic and geometric constraints. After obtaining the initial airfoil's pressure distribution at the design lift coefficient using an Euler solver coupled with an integml turbulent boundary layer method, the calculations from a laminar boundary layer solver are used by a stability analysis code to obtain estimates of the transition location (using N-Factors) for the starting airfoil. A new design method then calculates a target pressure distribution that will increase the larninar flow toward the desired amounl An airfoil design method is then iteratively used to design an airfoil that possesses that target pressure distribution. The new airfoil's boundary layer stability characteristics are determined, and this iterative process continues until an airfoil is designed that meets the laminar flow requirement and as many of the other constraints as possible.
Flow Visualization at Cryogenic Conditions Using a Modified Pressure Sensitive Paint Approach
NASA Technical Reports Server (NTRS)
Watkins, A. Neal; Goad, William K.; Obara, Clifford J.; Sprinkle, Danny R.; Campbell, Richard L.; Carter, Melissa B.; Pendergraft, Odis C., Jr.; Bell, James H.; Ingram, JoAnne L.; Oglesby, Donald M.
2005-01-01
A modification to the Pressure Sensitive Paint (PSP) method was used to visualize streamlines on a Blended Wing Body (BWB) model at full-scale flight Reynolds numbers. In order to achieve these conditions, the tests were carried out in the National Transonic Facility operating under cryogenic conditions in a nitrogen environment. Oxygen is required for conventional PSP measurements, and several tests have been successfully completed in nitrogen environments by injecting small amounts (typically < 3000 ppm) of oxygen into the flow. A similar technique was employed here, except that air was purged through pressure tap orifices already existent on the model surface, resulting in changes in the PSP wherever oxygen was present. The results agree quite well with predicted results obtained through computational fluid dynamics analysis (CFD), which show this to be a viable technique for visualizing flows without resorting to more invasive procedures such as oil flow or minitufts.
Bortolini, Olga; Cavazzini, Alberto; Giovannini, Pier Paolo; Greco, Roberto; Marchetti, Nicola; Massi, Alessandro; Pasti, Luisa
2013-06-10
The heterogeneous proline-catalyzed aldol reaction was investigated under continuous-flow conditions by means of a packed-bed microreactor. Reaction-progress kinetic analysis (RPKA) was used in combination with nonlinear chromatography for the interpretation, under synthetically relevant conditions, of important mechanistic aspects of the heterogeneous catalytic process at a molecular level. The information gathered by RPKA and nonlinear chromatography proved to be highly complementary and allowed for the assessment of optimal operating variables. In particular, the determination of the rate-determining step was pivotal for optimizing the feed composition. On the other hand, the competitive product inhibition was responsible for the unexpected decrease in the reaction yield following an apparently obvious variation in the feed composition. The study was facilitated by a suitable 2D instrumental arrangement for simultaneous flow reaction and online flow-injection analysis. PMID:23589216
NASA Astrophysics Data System (ADS)
Liu, X.
2013-12-01
In many natural and human-impacted rivers, the porous sediment beds are either fully or partially covered by large roughness elements, such as gravels and boulders. The existence of these large roughness elements, which are in direct contact with the turbulent river flow, changes the dynamics of mass and momentum transfer across the river bed. It also impacts the overall hydraulics in the river channel and over time, indirectly influences the geomorphological evolution of the system. Ideally, one should resolve each of these large roughness elements in a computational fluid model. This approach is apparently not feasible due to the prohibitive computational cost. Considering a typical river bed with armoring, the distribution of sediment sizes usually shows significant vertical variations. Computationally, it poses great challenge to resolve all the size scales. Similar multiscale problem exists in the much broader porous media flow field. To cope with this, we propose a hybrid computational approach where the large surface roughness elements are resolved using immersed boundary method and sediment layers below (usually finer) are modeled by adding extra drag terms in momentum equations. Large roughness elements are digitized using a 3D laser scanner. They are put into the computational domain using the collision detection and rigid body dynamics algorithms which guarantees realistic and physically-correct spatial arrangement of the surface elements. Simulation examples have shown the effectiveness of the hybrid approach which captures the effect of the surface roughness on the turbulent flow as well as the hyporheic flow pattern in and out of the bed.
Zhang, Z. F.; Khaleel, Raziuddin
2010-09-02
Various stochastic methods have been developed over the past two decades to estimate effective unsaturated hydraulic properties. We develop in this paper an alternative practical approach to estimate three-dimensional effective unsaturated hydraulic conductivity via a combined power-averaging and tensorial connectivity-tortuosity (PA-TCT) model. An application of the new approach to data collected at a field injection site suggests that the PA-TCT model provides 1) a reasonable framework for upscaling core-scale measurements and 2) an accurate simulation of moisture flow in a heterogeneous vadose zone. The heterogeneous media at the injection site is composed of multiple geologic units, each of which is represented by an anisotropic equivalent homogeneous medium (EHM). The directional effective hydraulic conductivity for each anisotropic EHM was determined by upscaling the laboratory-measured hydraulic properties with the combined PA-TCT approach. A larger difference between the power values in the horizontal and vertical directions indicates a larger macroscopic anisotropy in unsaturated hydraulic conductivity. A moment analysis was used to quantify the center of mass and the spread of the moisture content difference. Numerical simulations showed that, if the flow domain were treated as being isotropic, the vertical migration was significantly overestimated while the lateral movement was underestimated when compared to observations. To the contrary, if the media was treated as perfectly stratified, the lateral moisture movement was considerably overestimated while the vertical movement was underestimated. However, when the flow domain was modeled as being mildly anisotropic with the PA-TCT based parameters, the model can successfully predict the moisture flow and the simulated plume matched the observed moisture plume the best.
An Approach to Adaptive Correction Factors in Depth-Averaged Model for Debris Flows
NASA Astrophysics Data System (ADS)
Tai, Yih-Chin; Cheng, Chin-Kai; Lai, Guan-Cen
2016-04-01
In modeling the debris flows, the governing equations are often given in depth-averaged form, where scaling analysis is employed to reduce the complexity and expense in computation. As a result, the non-uniform distributions of the sediment concentration and velocity along the flow thickness bring the correction parameters into the equation system. Since the flows are generally not at steady state, these distributions vary dynamically, so that the values of the correction factors should not be given by constant values. With the concept of two-phase mixture, we revisit the depth-averaged balance equations, where four correction factors are present and inevitable in the resultant model equations if the distributions of the sediment concentration and velocity along the flow thickness are non-uniform. Through theoretical analysis and experimental investigation, we found that a piecewise-linear distribution for velocity and a linear distribution of sediment concentration in the immature debris flows (where the clear water exists) seem plausible. This assumption may significantly simplify the complicated determination of the correction factors. In the resultant model equations, the correcting parameters due to the non-uniform distributions are present, which are of significant impacts on the characteristic of the equation system, and play crucial roles in performing the numerical simulation. In this study, the values of these factors with respect to the corresponding profiles are investigated. By means of numerical examples, we shall illustrate their impacts on the flow behaviors, such as the concentration variation, the geometry of the deposit and the maximum run-out distance.
Huang, Qiu; Peng, Qiyu; Huang, Bin; Cheryauka, Arvi; Gullberg, Grant T.
2008-05-15
The measurement of flow obtained using continuous wave Doppler ultrasound is formulated as a directional projection of a flow vector field. When a continuous ultrasound wave bounces against a flowing particle, a signal is backscattered. This signal obtains a Doppler frequency shift proportional to the speed of the particle along the ultrasound beam. This occurs for each particle along the beam, giving rise to a Doppler velocity spectrum. The first moment of the spectrum provides the directional projection of the flow along theultrasound beam. Signals reflected from points further away from the detector will have lower amplitude than signals reflected from points closer to the detector. The effect is very much akin to that modeled by the attenuated Radon transform in emission computed tomography.A least-squares method was adopted to reconstruct a 2D vector field from directional projection measurements. Attenuated projections of only the longitudinal projections of the vector field were simulated. The components of the vector field were reconstructed using the gradient algorithm to minimize a least-squares criterion. This result was compared with the reconstruction of longitudinal projections of the vector field without attenuation. Ifattenuation is known, the algorithm was able to accurately reconstruct both components of the full vector field from only one set of directional projection measurements. A better reconstruction was obtained with attenuation than without attenuation implying that attenuation provides important information for the reconstruction of flow vector fields.This confirms previous work where we showed that knowledge of the attenuation distribution helps in the reconstruction of MRI diffusion tensor fields from fewer than the required measurements. In the application of ultrasound the attenuation distribution is obtained with pulse wave transmission computed tomography and flow information is obtained with continuous wave Doppler.
NASA Astrophysics Data System (ADS)
Huang, Rong-Hwa; Yang, Chang-Lin; Hsu, Chun-Ting
2015-12-01
Flow shop production system - compared to other economically important production systems - is popular in real manufacturing environments. This study focuses on the flow shop with multiprocessor scheduling problem (FSMP), and develops an improved particle swarm optimisation heuristic to solve it. Additionally, this study designs an integer programming model to perform effectiveness and robustness testing on the proposed heuristic. Experimental results demonstrate a 10% to 50% improvement in the effectiveness of the proposed heuristic in small-scale problem tests, and a 10% to 40% improvement in the robustness of the heuristic in large-scale problem tests, indicating extremely satisfactory performance.
NASA Astrophysics Data System (ADS)
Miller, Cass T.; Gray, William G.
2008-03-01
This work is the fourth in a series of papers on the thermodynamically constrained averaging theory (TCAT) approach for modeling flow and transport phenomena in multiscale porous medium systems. The general TCAT framework and the mathematical foundation presented in previous works are built upon by formulating macroscale models for conservation of mass, momentum, and energy, and the balance of entropy for a species in a phase volume, interface, and common curve. In addition, classical irreversible thermodynamic relations for species in entities are averaged from the microscale to the macroscale. Finally, we comment on alternative approaches that can be used to connect species and entity conservation equations to a constrained system entropy inequality, which is a key component of the TCAT approach. The formulations detailed in this work can be built upon to develop models for species transport and reactions in a variety of multiphase systems.
van Bussel, Frank C G; van Bussel, Bas C T; Hoeks, Arnold P G; Op 't Roodt, Jos; Henry, Ronald M A; Ferreira, Isabel; Vanmolkot, Floris H M; Schalkwijk, Casper G; Stehouwer, Coen D A; Reesink, Koen D
2015-01-01
Flow-mediated dilation is aimed at normalization of local wall shear stress under varying blood flow conditions. Blood flow velocity and vessel diameter are continuous and opposing influences that modulate wall shear stress. We derived an index FMDv to quantify wall shear stress normalization performance by flow-mediated dilation in the brachial artery. In 22 fasting presumed healthy men, we first assessed intra- and inter-session reproducibilities of two indices pFMDv and mFMDv, which consider the relative peak and relative mean hyperemic change in flow velocity, respectively. Second, utilizing oral glucose loading, we evaluated the tracking performance of both FMDv indices, in comparison with existing indices [i.e., the relative peak diameter increase (%FMD), the peak to baseline diameter ratio (Dpeak/Dbase), and the relative peak diameter increase normalized to the full area under the curve of blood flow velocity with hyperemia (FMD/shearAUC) or with area integrated to peak hyperemia (FMD/shearAUC_peak)]. Inter-session and intra-session reproducibilities for pFMDv, mFMDv and %FMD were comparable (intra-class correlation coefficients within 0.521-0.677 range). Both pFMDv and mFMDv showed more clearly a reduction after glucose loading (reduction of ~45%, p≤0.001) than the other indices (% given are relative reductions): %FMD (~11%, p≥0.074); Dpeak/Dbase (~11%, p≥0.074); FMD/shearAUC_peak (~20%, p≥0.016) and FMD/shearAUC (~38%, p≤0.038). Further analysis indicated that wall shear stress normalization under normal (fasting) conditions is already far from ideal (FMDv < 1), which (therefore) does not materially change with glucose loading. Our approach might be useful in intervention studies to detect intrinsic changes in shear stress normalization performance in conduit arteries. PMID:25693114
NASA Astrophysics Data System (ADS)
Saidi, M. S.; Rismanian, M.; Monjezi, M.; Zendehbad, M.; Fatehiboroujeni, S.
2014-06-01
Modeling the behavior of suspended particles in gaseous phase is important for diverse reasons; e.g. aerosol is usually the main subject of CFD simulations in clean rooms. Additionally, to determine the rate and sites of deposition of particles suspended in inhaled air, the motion of the particles should be predicted in lung airways. Meanwhile there are two basically different approaches to simulate the behavior of particles suspension, Lagrangian and Eulerian approaches. This study compares the results of these two approaches on simulating the same problem. An in-house particle tracking code was developed to simulate the motion of particles with Lagrangian approach. In order to simulate the same problem with Eulerian approach, the solution to the transport equation with appropriate initial and boundary conditions was used. In the first case study, diffusion of particles, initially positioned homogeneously on an infinite plane was modeled with both approaches and the results were compared and the mismatch between Lagrangian and Eulerian approaches was analyzed for different concentrations. In the second case study, airflow with parabolic velocity profile moving between two parallel plates was modeled with two approaches. The airflow initially contained a homogeneous suspension of particles and the plates were maintained at zero concentration. The concentration along the plates was compared between the two approaches and the differences in the performance of each approach were investigated, again for different initial concentrations. The overall results confirm that as particle concentration falls below a minimum amount, approximately 105 m-2, the results of the two approaches deviate considerably from each other and hence the Eulerian approach cannot be taken as an alternative for Lagrangian approach for low concentrations. For the third problem, we investigated the 3D particle flow in an expanding lung alveolus. It is shown that when the number of total released
Simulation of flow through nanochannels: a novel multi-scale approach
NASA Astrophysics Data System (ADS)
Jaeger, Frederike; Wray, Alex; Muller, Erich; Poesio, Pietro; Matar, Omar
2015-11-01
A novel method for the simulation of flow through nanochannels is proposed. We use molecular dynamics (MD) simulations to determine relations between the pressure, shear and bulk viscosities and the density, as well as the slip length for different fluid-wall combinations. These relations are then plugged into a steady, two-dimensional continuum-scale model that allows the simulation of a compressible (Lennard-Jones) fluid through channels. No restrictive assumptions are made on the nature of the fluid and its flow behaviour (e.g. fully-developed, parabolic velocity profiles for incompressible fluids). Direct comparisons between the MD and the continuum-scale predictions for the channel flow show good agreement. A major advantage of the proposed method is its computational efficiency, which allows for complex flow geometries to be studied whilst still retaining the accuracy of MD-based simulations. Furthermore, through the use of the statistical fluid associating theory (SAFT), more complex fluids can be modelled, providing a computational framework capable of representing realistic experimental set-ups. EPSRC through TSM-CDT (FJ), DPF (AWW), MEMPHIS (EP/K003976/1, OKM), MACIPH (EP/L020564/1, EAM, OKM); Royal Society International Exchange Scheme (PP, OKM).
URBAN WET-WEATHER FLOW MICROBIAL CONTAMINATION: HIGH-RATE TREATMENT APPROACHES
fThis presentation is on high-rate disinfection of wet-weather flow (WWF) and pretreatment processes of suspended solids to enhance the disinfection. A discussion of pretreatment processes and of the newest disinfection technologies used for WWF is included, along with the feasib...
Innovative Approaches for Urban Watershed Management Wet-Weather Flow Management and Control
The overall objective of this project was to identify innovative strategies for managing the effects of wet-weather flow (WWF) control and failing infrastructure in an urban setting. The intent was to establish areas where external information can benefit US Environmental Protec...
A MULTIPLE GRID APPROACH FOR OPEN CHANNEL FLOWS WITH STRONG SHOCKS. (R825200)
Explicit finite difference schemes are being widely used for modeling open channel flows accompanied with shocks. A characteristic feature of explicit schemes is the small time step, which is limited by the CFL stability condition. To overcome this limitation,...
A wall-function approach to incorporating Knudsen-layer effects in gas micro flow simulations.
Gallis, Michail A.; Lockerby, Duncan A.; Reese, Jason M.
2004-07-01
For gas flows in microfluidic configurations, the Knudsen layer close to the wall can comprise a substantial part of the entire flowfield and has a major effect on quantities such as the mass flow rate through micro devices. The Knudsen layer itself is characterized by a highly nonlinear relationship between the viscous stress and the strain rate of the gas, so even if the Navier-Stokes equations can be used to describe the core gas flow they are certainly inappropriate for the Knudsen layer itself. In this paper we propose a 'wall-function' model for the stress/strain rate relations in the Knudsen layer. The constitutive structure of the Knudsen layer has been derived from results from kinetic theory for isothermal shear flow over a planar surface. We investigate the ability of this simplified model to predict Knudsen-layer effects in a variety of configurations. We further propose a semi-empirical Knudsen-number correction to this wall function, based on high-accuracy DSMC results, to extend the predictive capabilities of the model to greater degrees of rarefaction.
Pipe Flow Simulation Software: A Team Approach to Solve an Engineering Education Problem.
ERIC Educational Resources Information Center
Engel, Renata S.; And Others
1996-01-01
A computer simulation program for use in the study of fluid mechanics is described. The package is an interactive tool to explore the fluid flow characteristics of a pipe system by manipulating the physical construction of the system. The motivation, software design requirements, and specific details on how its objectives were met are presented.…
NASA Astrophysics Data System (ADS)
Ma, C.; Bothe, D.
2013-01-01
A one-field model is derived from the sharp interface continuum mechanical balances for two-phase evaporative and thermocapillary flows. Emphasis is put on a clear distinction of the different velocities at the interface which appear due to phase transfer. The one-field model is solved numerically within a Finite Volume scheme and the interface is captured using an extended Volume of Fluid method, where the interface is reconstructed linearly with the PLIC technique. The numerical heat transfer is based on a two-scalar approach where two separate temperature fields are used for the temperature inside the two phases. This results in an accurate treatment of the interfacial heat transfer, specifically the interface temperature which is crucial numerically, both for evaporation and thermocapillarity. The method is validated for two-phase heat conduction, with analytical solution in case of no evaporation and with experimental measurement in case of incorporated evaporation effect. The method is applied to realistic cases dealing with non-uniformly heated thin liquid films, i.e. liquid films on (i) structured heated substrates and (ii) locally heated substrates. The numerical predictions in terms of flow pattern, surface deformation, temperature and velocity are compared with experiments conducted at the Université Libre de Bruxelles for (i) and at the Technische Universität Darmstadt for (ii). Qualitative agreement is achieved and shows the potential of this approach to simulate thermocapillary flows with dynamically deformable interfaces combined with evaporation.
NASA Astrophysics Data System (ADS)
Rodrigues, C. Veiga; Palma, J. M. L. M.; Rodrigues, Á. H.
2016-05-01
The atmospheric flow over a mountainous region has been simulated using a model-chain approach, whereby the flow in a larger region was simulated using a mesoscale model with three nesting levels, down to a 3-km horizontal resolution, within which a fourth nesting level was set with a microscale flow solver and a domain with varying horizontal resolution, around 300 m at the site of interest. Two periods in the summer (July) and autumn (November-December) 2005, each with a duration of two weeks, were selected to test the present approach. Two sites were chosen, comprising a total of seven meteorological masts with wind vanes and anemometers at two heights. The microscale solver improved the wind-speed prediction of the mesoscale model in 10 of the 14 anemometers and replicated the high wind speeds, which were under-predicted in the mesoscale model. The wind conditions in summer varied with the daily cycle, related to regional-scale sea breezes and their interaction with local circulations induced by the topography. Regarding the turbulence intensity, the predicted decay with wind-speed increase was in agreement with the measurements. This study shows the need of both models: the microscale model captures the details of the boundary-layer physics, which would not be possible without the boundary conditions provided by the mesoscale model.
Incomplete Mixing and Reactions - A Lagrangian Approach in a Pure Shear Flow
NASA Astrophysics Data System (ADS)
Paster, Amir; Bolster, Diogo; Aquino, Tomas
2015-04-01
Incomplete mixing of reactive solutes is well known to slow down reaction rates relative to what would be expected from assuming perfect mixing. As reactions progress in a system and deplete reactant concentrations, initial fluctuations in the concentrations of reactions can be amplified relative to mean background concentrations and lead to spatial segregation of reactants. As the system evolves, in the absence of sufficient mixing, this segregation will increase, leading to a persistence of incomplete mixing that fundamentally changes the effective rate at which overall reactions will progress. On the other hand, nonuniform fluid flows are known to affect mixing between interacting solutes. Thus a natural question arises: Can non-uniform flows sufficiently enhance mixing to suppress incomplete mixing effects, and if so, under what conditions? In this work we address this question by considering one of the simplest possible flows, a laminar pure shear flow, which is known to significantly enhance mixing relative to diffusion alone. To study this system we adapt a novel Lagrangian particle-based random walk method, originally designed to simulate reactions in purely diffusive systems, to the case of advection and diffusion in a shear flow. To interpret the results we develop a semi-analytical solution, by proposing a closure approximation that aims to capture the effect of incomplete mixing. The results obtained via the Lagrangian model and the semi-analytical solutions consistently highlight that if shear effects in the system are not sufficiently strong, incomplete mixing effects initially similar to purely diffusive systems will occur, slowing down the overall reaction rate. Then, at some later time, dependent on the strength of the shear, the system will return to behaving as if it were well-mixed, but represented by a reduced effective reaction rate. If shear effects are sufficiently strong, the incomplete mixing regime never emerges and the system can behave
Paleointensity results for 0 and 3 ka from Hawaiian lava flows: a new approach to sampling
NASA Astrophysics Data System (ADS)
Cromwell, G.; Tauxe, L.; Staudigel, H.; Ron, H.; Trusdell, F.
2011-12-01
Paleointensity data are typically generated from core samples drilled out of the massive parts of lava flows. During Thellier-Thellier type experiments, these massive samples suffer from very low success rates (~20%), as shown by failure to meet statistical criteria. Low success generally occurs for two reasons: 1) alteration of the sample during the heating process, and 2) multi-domain behavior of massive material. Moreover, recent studies of historical lava flows show that massive samples may not accurately reflect the intensity of the magnetic field even when they are successful (Valet et al., 2010). Alternatively, submarine basaltic glasses (SBG) produce high success rates (~80%) for Thellier-Thellier type experiments, likely due to near instantaneous cooling rates which produce single-domain magnetic grains. In addition, SBG have been proven to produce accurate records of the magnetic field (e.g., Pick and Tauxe, 1993). In this study we investigate the success of paleointensity experiments on subaerial quenched basalts from Hawaii in the quest for single domain, rapidly cooled subaerial analogs to SBG. We also examine the effects of grain size and cooling rate on the accuracy of paleointensity results. During March 2011, we collected samples from 31 dated lava flows (0-3360 BP), including the [historical] 1950 C.E. and 2010 C.E. flows. Each lava flow was additionally subsampled when unique cooling structures within the unit could be identified. Results from the 1950 and 2010 glasses accurately record the expected geomagnetic field strength. We will present results of a comprehensive data set of Hawaiian paleointensity focused on about the last 3 ka.
NASA Astrophysics Data System (ADS)
Benard, N.; Pons-Prats, J.; Periaux, J.; Bugeda, G.; Braud, P.; Bonnet, J. P.; Moreau, E.
2016-02-01
The potential benefits of active flow control are no more debated. Among many others applications, flow control provides an effective mean for manipulating turbulent separated flows. Here, a nonthermal surface plasma discharge (dielectric barrier discharge) is installed at the step corner of a backward-facing step ( U 0 = 15 m/s, Re h = 30,000, Re θ = 1650). Wall pressure sensors are used to estimate the reattaching location downstream of the step (objective function #1) and also to measure the wall pressure fluctuation coefficients (objective function #2). An autonomous multi-variable optimization by genetic algorithm is implemented in an experiment for optimizing simultaneously the voltage amplitude, the burst frequency and the duty cycle of the high-voltage signal producing the surface plasma discharge. The single-objective optimization problems concern alternatively the minimization of the objective function #1 and the maximization of the objective function #2. The present paper demonstrates that when coupled with the plasma actuator and the wall pressure sensors, the genetic algorithm can find the optimum forcing conditions in only a few generations. At the end of the iterative search process, the minimum reattaching position is achieved by forcing the flow at the shear layer mode where a large spreading rate is obtained by increasing the periodicity of the vortex street and by enhancing the vortex pairing process. The objective function #2 is maximized for an actuation at half the shear layer mode. In this specific forcing mode, time-resolved PIV shows that the vortex pairing is reduced and that the strong fluctuations of the wall pressure coefficients result from the periodic passages of flow structures whose size corresponds to the height of the step model.
A full-Bayesian approach to the inverse problem for steady-state groundwater flow and heat transport
NASA Astrophysics Data System (ADS)
Jiang, Yefang; Woodbury, Allan D.
2006-12-01
The full (hierarchal) Bayesian approach proposed by Woodbury & Ulrych and Jiang et al. is extended to the inverse problem for 2-D steady-state groundwater flow and heat transport. A stochastic conceptual framework for the heat flow and groundwater flow is adopted. A perturbation of both the groundwater flow and the advection-conduction heat transport equations leads to a linear formulation between heads, temperature and logarithm transmissivity [denoted as ln (T)]. A Bayesian updating procedure similar to that of Woodbury & Ulrych can then be performed. This new algorithm is examined against a generic example through simulations. The prior mean, variance and integral scales of ln (T) (hyperparameters) are treated as random variables and their pdfs are determined from maximum entropy considerations. It is also assumed that the statistical properties of the noise in the hydraulic head and temperature measurements are also uncertain. Uncertainties in all pertinent hyperparameters are removed by marginalization. It is found that the use of temperature measurements is showed to further improve the ln (T) estimates for the test case in comparison to the updated ln (T) field conditioned on ln (T) and head data; the addition of temperature data without hydraulic head data to the update also aids refinement of the ln (T) field compared to simply interpolating ln (T) data alone these results suggest that temperature measurements are a promising data source for site characterization for heterogeneous aquifer, which can be accomplished through the full-Bayesian methodology.
NASA Astrophysics Data System (ADS)
Winter, M. G.; Smith, J. T.; Fotopoulou, S.; Pitlakis, K.; Mavrouli, O.-C.; Corominas, J.; Argyroudis, S.
2012-04-01
The physical vulnerability of roads to debris flow is expressed through fragility functions that relate flow volume to damage probabilities. Fragility relationships are essential components of quantitative risk assessments (QRA) as they allow for the estimation of risk within a consequence-based framework. To the best of the Authors' knowledge this is the first time that fragility curves have been produced in order to provide the conditional probability for a road to be in, or to exceed, a certain damage state for a given debris flow volume. Preliminary assessments were undertaken by means of a detailed questionnaire. A total of 47 returns were received from experts in 17 countries: 32% academia, 51% the commercial sector and 17% governments. Fragility curves have been defined for three damage states (limited damage, serious damage and destroyed) for each of low speed and high speed roads in order to cover the typical characteristics of roads vulnerable to debris flow. The probability of any given damage state being met or exceeded by a debris flow of a given volume (10 to 100,000m3) was derived from the mean of the responses received. Inevitably there was a degree of scatter in the results and the treatment of such variation, or 'experimental errors', was crucial to understanding the data and to developing the fragility curves. Both qualitative and quantitative methods of arriving at these preliminary fragility curves were utilised. The nature of the data is such that unless all respondents return that value the average probability at the largest flow volume cannot reach unity; as a result the upper ends of each curve were forced to unity and in order to account for larger potential volumes manual extrapolation was undertaken to 1,000,000m3. In addition to an assessment of the probabilities of given damage states being exceeded respondents to the questionnaire were polled as to their level of experience and confidence in their ability to provide a valid and
Zimmerman, R.W.; Bodvarsson, G.S.
1990-01-01
Various analytical and numerical approaches are presented for the study of unsaturated flow processes in the vicinity of the Yucca Mountain, Nevada, the proposed site of an underground radioactive waste repository. Approximate analytical methods are used to study absorption of water from a saturated fracture into the adjacent rock. These solutions are incorporated into a numerical simulator as fracture/matrix interaction terms to treat problems such as flow along a fracture with transverse leakage into the matrix. An automatic fracture/matrix mesh generator is described; it allows for more efficient mesh generation for fractured/porous media, and consequently leads to large savings in computational time and cost. 21 refs., 6 figs.
A Bayesian Hierarchical Modeling Approach to Predicting Flow in Ungauged Basins
Recent innovative approaches to identifying and applying regression-based relationships between land use patterns (such as increasing impervious surface area and decreasing vegetative cover) and rainfall-runoff model parameters represent novel and promising improvements to predic...
A massively parallel computational approach to coupled thermoelastic/porous gas flow problems
NASA Technical Reports Server (NTRS)
Shia, David; Mcmanus, Hugh L.
1995-01-01
A new computational scheme for coupled thermoelastic/porous gas flow problems is presented. Heat transfer, gas flow, and dynamic thermoelastic governing equations are expressed in fully explicit form, and solved on a massively parallel computer. The transpiration cooling problem is used as an example problem. The numerical solutions have been verified by comparison to available analytical solutions. Transient temperature, pressure, and stress distributions have been obtained. Small spatial oscillations in pressure and stress have been observed, which would be impractical to predict with previously available schemes. Comparisons between serial and massively parallel versions of the scheme have also been made. The results indicate that for small scale problems the serial and parallel versions use practically the same amount of CPU time. However, as the problem size increases the parallel version becomes more efficient than the serial version.
The design/analysis of flows through turbomachinery: A viscous/inviscid approach
NASA Technical Reports Server (NTRS)
Miller, D. P.; Reddy, D. R.
1991-01-01
The development of a design/analysis flow solver at NASA Lewis Research Center is discussed. The solver is axisymmetric and can be run inviscidly with assumed or calculated blockages, or with the viscous terms computed. The blade forces for each blade row are computed from blade-to-blade solutions, correlated data or force model, or from a full three dimensional solution. Codes currently under development can be separated into three distinct elements: the turbomachinery interactive grid generator energy distribution restart code (TIGGERC), the interactive blade element geometry generator (IBEGG), and the viscous/inviscid multi-blade-row average passage flow solver (VIADAC). Several experimental test cases were run to validate the VIADAC code. The tests, representative of typical axial turbomachinery duct axisymmetric wind tunnel body problems, were conducted on an SR7 Spinner axisymmetric body, a NASA Rotor 67 Fan test bed, and a transonic boatail body. The results show the computations to be in good agreement with test data.
NASA Astrophysics Data System (ADS)
Abraham, Theodore P.
2011-11-01
Hypertrophic Cardiomyopathy (HCM) is the most common inherited heart disease and occurs in 1 in 500 persons worldwide regardless of race, age and gender. It is the most common cause of sudden death in the young and also causes heart failure and cardiac arrhythmias. The primary anatomic abnormality is thickening of certain walls, or sometimes global thickening of the left or right ventricle. The patterns of thickening along with increased ventricular stiffness lead to suboptimal ventricular filling and inefficient ejection of blood from the ventricle. Treatment for HCM can be medical or surgical. The choice of therapy is driven by the presence and severity of outflow obstruction. Flow analysis could provide sophisticated information about outflow and inflow ventricular dynamics. These flow dynamics features may enable better medical choices and provide information that would allow superior surgical planning. Associate Professor of Medicine & Director, Hypertrophic Cardiomyopathy Clinic
A Finite-Element Approach for Modeling Inviscid and Viscous Compressible Flows using Prismatic Grids
NASA Technical Reports Server (NTRS)
Pandya, S. A.; Hefez, M.
2000-01-01
The Galerkin finite-element method is used to solve the Euler and Navier-Stokes equations on prismatic meshes. It is shown that the prismatic grid is advantageous for correctly and efficiently capturing the boundary layers in high Reynolds number flows. It can be captured accurately because of the ability to cluster grid points normal to the body. The efficiency derives from the implicit treatment of the normal direction. To treat the normal direction implicitly, a semi-implicit Runge-Kutta time stepping scheme is developed. The semi-implicit algorithm is validated on simple geometries for inviscid and viscous flows and its convergence history is compared to that of the explicit Runge-Kutta scheme. The semi-implicit scheme is shown to be a factor of 3 to 4 faster in terms of CPU time to convergence.
A fast approach to designing airfoils from given pressure distribution in compressible flows
NASA Technical Reports Server (NTRS)
Daripa, Prabir
1987-01-01
A new inverse method for aerodynamic design of airfols is presented for subcritical flows. The pressure distribution in this method can be prescribed as a function of the arc length of the as-yet unknown body. This inverse problem is shown to be mathematically equivalent to solving only one nonlinear boundary value problem subject to known Dirichlet data on the boundary. The solution to this problem determines the airfoil, the freestream Mach number, and the upstream flow direction. The existence of a solution to a given pressure distribution is discussed. The method is easy to implement and extremely efficient. A series of results for which comparisons are made with the known airfoils is presented.
Learning Based Approach for Optimal Clustering of Distributed Program's Call Flow Graph
NASA Astrophysics Data System (ADS)
Abofathi, Yousef; Zarei, Bager; Parsa, Saeed
Optimal clustering of call flow graph for reaching maximum concurrency in execution of distributable components is one of the NP-Complete problems. Learning automatas (LAs) are search tools which are used for solving many NP-Complete problems. In this paper a learning based algorithm is proposed to optimal clustering of call flow graph and appropriate distributing of programs in network level. The algorithm uses learning feature of LAs to search in state space. It has been shown that the speed of reaching to solution increases remarkably using LA in search process, and it also prevents algorithm from being trapped in local minimums. Experimental results show the superiority of proposed algorithm over others.
NASA Astrophysics Data System (ADS)
Vrettas, M. D.; Fung, I. Y.
2014-12-01
The degree of carbon climate feedback by terrestrial ecosystems is intimately tied to the availability of moisture for photosynthesis, transpiration and decomposition. The vertical distribution of subsurface moisture and its accessibility for evapotranspiration is a key determinant of the fate of ecosystems and their feedback on the climate system. A time series of five years of high frequency (every 30 min) observations of water table at a research site in Northern California shows that the water tables, 18 meters below the surface, can respond in less than 8 hours to the first winter rains, suggesting very fast flow through micro-pores and fractured bedrock. Not quite as quickly as the water table rises after a heavy rain, the elevated water level recedes, contributing to down-slope flow and stream flow. The governing equation of our model uses the well-known Richards' equation, which is a non-linear PDE, derived by applying the continuity requirement to Darcy's law. The most crucial parameter of this PDE is the hydraulic conductivity K(θ), which describes the speed at which water can move in the underground. We specify a saturation profile as a function of depth (i.e. Ksat(z)) and allow K(θ) to vary not only with the soil moisture saturation but also include a stochastic component which mimics the effects of fracture flow and other naturally occurring heterogeneity, that is evident in the subsurface. A large number of Monte Carlo simulation are performed in order to identify optimal settings for the new model, as well as analyze the results of this new approach on the available data. Initial findings from this exploratory work are encouraging and the next steps include testing this new stochastic approach on data from other sites and also apply ensemble based data assimilation algorithms in order to estimate model parameters with the available measurements.
NASA Technical Reports Server (NTRS)
Liu, C. H.; Wong, T. C.; Kandil, O. A.
1988-01-01
The two-dimensional flow over a blunt leading-edge plate is simulated on the basis of an Euler/Navier-Stokes zonal scheme. The scheme uses an implicit upwind finite-volume scheme, which is based on the van Leer flux-vector splitting. It is shown that the Euler/Navier-Stokes zonal scheme with downstream boundary-layer compatibility conditions is accurate and efficient.
A 3-D Euler method for internal transonic flows computation with a multi-domain approach
NASA Astrophysics Data System (ADS)
Veuillot, J. P.; Meauze, G.
1985-05-01
The results of calculations of three dimensional viscous flow in two centrifugal compressor impellers and in two linear turbine cascades are considered and answers to thermodynamic questions are obtained. For the impellers, the calculations give the work and the losses, the total pressure ratio and the efficiency, and show where the inefficiency arises. The results for the turbines show the increase in loss within and downstream of the cascades and allow the buildup and decay of secondary kinetic energy to be followed.
Field, laboratory and numerical approaches to studying flow through mangrove pneumatophores
NASA Astrophysics Data System (ADS)
Chua, V. P.
2014-12-01
The circulation of water in riverine mangrove swamps is expected to be influenced by mangrove roots, which in turn affect the nutrients, pollutants and sediments transport in these systems. Field studies were carried out in mangrove areas along the coastline of Singapore where Avicennia marina and Sonneratia alba pneumatophore species are found. Geometrical properties, such as height, diameter and spatial density of the mangrove roots were assessed through the use of photogrammetric methods. Samples of these roots were harvested from mangrove swamps and their material properties, such as bending strength and Young's modulus were determined in the laboratory. It was found that the pneumatophores under hydrodynamic loadings in a mangrove environment could be regarded as fairly rigid. Artificial root models of pneumatophores were fabricated from downscaling based on field observations of mangroves. Flume experiments were performed and measurements of mean flow velocities, Reynolds stress and turbulent kinetic energy were made. The boundary layer formed over the vegetation patch is fully developed after x = 6 m with a linear mean velocity profile. High shear stresses and turbulent kinetic energy were observed at the interface between the top portion of the roots and the upper flow. The experimental data was employed to calibrate and validate three-dimensional simulations of flow in pneumatophores. The simulations were performed with the Delft3D-FLOW model, where the vegetation effect is introduced by adding a depth-distributed resistance force and modifying the k-ɛ turbulence model. The model-predicted profiles for mean velocity, turbulent kinetic energy and concentration were compared with experimental data. The model calibration is performed by adjusting the horizontal and vertical eddy viscosities and diffusivities. A skill assessment of the model is performed using statistical measures that include the Pearson correlation coefficient (r), the mean absolute error
Cold flow simulation of an internal combustion engine with vertical valves using layering approach
NASA Astrophysics Data System (ADS)
Martinas, G.; Cupsa, O. S.; Stan, L. C.; Arsenie, A.
2015-11-01
Complying with emission requirements and fuel consumption efficiency are the points which drive any development of internal combustion engine. Refinement of the process of combustion and mixture formation, together with in-cylinder flow refinement, is a requirement, valves and piston bowl and intake exhaust port design optimization is essential. In order to reduce the time for design optimization cycle it is used Computational Fluid Dynamics (CFD). Being time consuming and highly costly caring out of experiment using flow bench testing this methods start to become less utilized. Air motion inside the intake manifold is one of the important factors, which govern the engine performance and emission of multi-cylinder diesel engines. Any cold flow study on IC is targeting the process of identifying and improving the fluid flow inside the ports and the combustion chamber. This is only the base for an optimization process targeting to increase the volume of air accessing the combustion space and to increase the turbulence of the air at the end of the compression stage. One of the first conclusions will be that the valve diameter is a fine tradeoff between the need for a bigger diameter involving a greater mass of air filling the cylinder, and the need of a smaller diameter in order to reduce the blind zone. Here there is room for optimization studies. The relative pressure indicates a suction effect coming from the moving piston. The more the shape of the inlet port is smoother and the diameter of the piston is bigger, the aerodynamic resistance of the geometry will be smaller so that the difference of inlet port pressure and the pressure near to piston face will be smaller. Here again there is enough room for more optimization studies.
Biomimetic approaches for green tribology: from the lotus effect to blood flow control
NASA Astrophysics Data System (ADS)
Maani, Nazanin; Rayz, Vitaliy S.; Nosonovsky, Michael
2015-09-01
The research in Green tribology combines several areas including biomimetic tribomaterials and surfaces for controlled adhesion. Biomimetic surfaces mimic living nature and thus they are eco-friendly. The most famous biomimetic surface effect is the Lotus effect (reduction of water adhesion to a solid surface due to micro/nanostructuring of the solid surface). Several extensions of the Lotus effect have been discussed in the literature including the oleophobicity (repelling organic liquids such as oils), underwater oleophobicity to reduce fouling, and the shark skin effect (flow drag reduction due to specially oriented micro-riblets). Here we suggest a potentially important application of micro/nanostructured surfaces in the biomedical area: the micro/nanostructure controlled adhesion in blood flow. Blood is a suspension, and its adhesion properties are different from those of water and oil. For many cardiovascular applications, it is desirable to reduce stagnation and clotting of blood. Therefore, both the underwater oleophobicuity and shark-skin effect can be used. We discuss how computational fluid dynamics models can be used to investigate the structure-property relationships of surface pattern-controlled blood flow adhesion.
A first-order time-domain Green's function approach to supersonic unsteady flow
NASA Technical Reports Server (NTRS)
Freedman, M. I.; Tseng, K.
1985-01-01
A time-domain Green's Function Method for unsteady supersonic potential flow around complex aircraft configurations is presented. The focus is on the supersonic range wherein the linear potential flow assumption is valid. The Green's function method is employed in order to convert the potential-flow differential equation into an integral one. This integral equation is then discretized, in space through standard finite-element technique, and in time through finite-difference, to yield a linear algebraic system of equations relating the unknown potential to its prescribed co-normalwash (boundary condition) on the surface of the aircraft. The arbitrary complex aircraft configuration is discretized into hyperboloidal (twisted quadrilateral) panels. The potential and co-normalwash are assumed to vary linearly within each panel. Consistent with the spatial linear (first-order) finite-element approximations, the potential and co-normalwash are assumed to vary linearly in time. The long range goal of our research is to develop a comprehensive theory for unsteady supersonic potential aerodynamics which is capable of yielding accurate results even in the low supersonic (i.e., high transonic) range.
Modelling the Transport of Nanoparticles under Blood Flow using an Agent-based Approach
Fullstone, Gavin; Wood, Jonathan; Holcombe, Mike; Battaglia, Giuseppe
2015-01-01
Blood-mediated nanoparticle delivery is a new and growing field in the development of therapeutics and diagnostics. Nanoparticle properties such as size, shape and surface chemistry can be controlled to improve their performance in biological systems. This enables modulation of immune system interactions, blood clearance profile and interaction with target cells, thereby aiding effective delivery of cargo within cells or tissues. Their ability to target and enter tissues from the blood is highly dependent on their behaviour under blood flow. Here we have produced an agent-based model of nanoparticle behaviour under blood flow in capillaries. We demonstrate that red blood cells are highly important for effective nanoparticle distribution within capillaries. Furthermore, we use this model to demonstrate how nanoparticle size can selectively target tumour tissue over normal tissue. We demonstrate that the polydispersity of nanoparticle populations is an important consideration in achieving optimal specificity and to avoid off-target effects. In future this model could be used for informing new nanoparticle design and to predict general and specific uptake properties under blood flow. PMID:26058969
A flow cytometric approach to the study of crustacean cellular immunity
Cardenas, W.; Jenkins, J.A.; Dankert, J.R.
2000-01-01
Responses of hemocytes from the crayfish Procambarus zonangulus to stimulation by fungal cell walls (Zymosan A) were measured by flow cytometry. Changes in hemocyte physical characteristics were assessed flow cytometrically using forward- and sidescatter light parameters, and viability was measured by two-color fluorescent staining with calcein-AM and ethidium homodimer 1. The main effects of zymosan A on crayfish hemocytes were reduction in cell size and viability compared to control mixtures (hemocytes in buffer only). Adding diethyldithiocarbamic acid, an inhibitor of phenoloxidase, to hemocyte to zymosan mixtures delayed the time course of cell size reduction and cell death compared to zymosan-positive controls. The inclusion of trypsin inhibitor in reaction mixtures further delayed the reduction in hemocyte size and cell death, thereby indicating that a proteolytic cascade, along with prophenoloxidase activation, played a key role in generating signal molecules which mediate these cellular responses. In addition to traditional methods such as microscopy and protein chemistry, flow cytometry can provide a simple, reproducible, and sensitve method for evaluating invertebrate hemocyte responses to immunological stimuli.
Approaches to myosin modelling in a two-phase flow model for cell motility
NASA Astrophysics Data System (ADS)
Kimpton, L. S.; Whiteley, J. P.; Waters, S. L.; Oliver, J. M.
2016-04-01
A wide range of biological processes rely on the ability of cells to move through their environment. Mathematical models have been developed to improve our understanding of how cells achieve motion. Here we develop models that explicitly track the cell's distribution of myosin within a two-phase flow framework. Myosin is a small motor protein which is important for contracting the cell's actin cytoskeleton and enabling cell motion. The two phases represent the actin network and the cytosol in the cell. We start from a fairly general description of myosin kinetics, advection and diffusion in the two-phase flow framework, then identify a number of sub-limits of the model that may be relevant in practice, two of which we investigate further via linear stability analyses and numerical simulations. We demonstrate that myosin-driven contraction of the actin network destabilizes a stationary steady state leading to cell motion, but that rapid diffusion of myosin and rapid unbinding of myosin from the actin network are stabilizing. We use numerical simulation to investigate travelling-wave solutions relevant to a steadily gliding cell and we consider a reduction of the model in which the cell adheres strongly to the substrate on which it is crawling. This work demonstrates that a number of existing models for the effect of myosin on cell motility can be understood as different sub-limits of our two-phase flow model.
An improved parallel SPH approach to solve 3D transient generalized Newtonian free surface flows
NASA Astrophysics Data System (ADS)
Ren, Jinlian; Jiang, Tao; Lu, Weigang; Li, Gang
2016-08-01
In this paper, a corrected parallel smoothed particle hydrodynamics (C-SPH) method is proposed to simulate the 3D generalized Newtonian free surface flows with low Reynolds number, especially the 3D viscous jets buckling problems are investigated. The proposed C-SPH method is achieved by coupling an improved SPH method based on the incompressible condition with the traditional SPH (TSPH), that is, the improved SPH with diffusive term and first-order Kernel gradient correction scheme is used in the interior of the fluid domain, and the TSPH is used near the free surface. Thus the C-SPH method possesses the advantages of two methods. Meanwhile, an effective and convenient boundary treatment is presented to deal with 3D multiple-boundary problem, and the MPI parallelization technique with a dynamic cells neighbor particle searching method is considered to improve the computational efficiency. The validity and the merits of the C-SPH are first verified by solving several benchmarks and compared with other results. Then the viscous jet folding/coiling based on the Cross model is simulated by the C-SPH method and compared with other experimental or numerical results. Specially, the influences of macroscopic parameters on the flow are discussed. All the numerical results agree well with available data, and show that the C-SPH method has higher accuracy and better stability for solving 3D moving free surface flows over other particle methods.
Effects of modified pharmacologic stress approaches on hyperemic myocardial blood flow
Czernin, J.; Auerbach, M.; Sun, K.T.
1995-04-01
Pharmacologic stress testing with 0.56 mg/kg of intravenous dipyridamole is frequently used to noninvasively detect coronary artery disease (CAD). However, high-dose dipyridamole (0.80 mg/kg) or the combination of standard-dose dipyridamole (0.56 mg/kg) with the isometric handgrip maneuver might evoke a greater coronary hyperemic response. To evaluate the effect of modified pharmacologic stress tests, myocardial blood flow was quantified in 11 male subjects (mean age: 27 {plus_minus} 7 yr) during standard-dose dipyridamole (0.56 mg/kg), high-dose dipyridamole (0.80 mg/kg) and standard-dose dipyridamole combined with the isometric handgrip exercise using dynamic PET and a two-compartment model for {sup 13}N-ammonia. Systolic blood pressure, heart rate and rate pressure product remained unchanged from standard to high-dose dipyridamole but increased with the addition of the isometric handgrip. Myocardial blood flow was unchanged from standard to high-dose dipyridamole but was lower with the addition of the isometric handgrip. The hyperemic response induced by standard-dose dipyridamole cannot be further enhanced by high-dose dipyridamole. The addition of the isometric handgrip exercise results in a modest, but significant decline in hyperemic blood flow possibly due to increased extravascular resistive forces or an increase in a mediated coronary vasoconstriction associated with exercise. 31 refs., 2 figs., 1 tab.
NASA Astrophysics Data System (ADS)
von Larcher, Thomas; Blome, Therese; Klein, Rupert; Schneider, Reinhold; Wolf, Sebastian; Huber, Benjamin
2016-04-01
Handling high-dimensional data sets like they occur e.g. in turbulent flows or in multiscale behaviour of certain types in Geosciences are one of the big challenges in numerical analysis and scientific computing. A suitable solution is to represent those large data sets in an appropriate compact form. In this context, tensor product decomposition methods currently emerge as an important tool. One reason is that these methods often enable one to attack high-dimensional problems successfully, another that they allow for very compact representations of large data sets. We follow the novel Tensor-Train (TT) decomposition method to support the development of improved understanding of the multiscale behavior and the development of compact storage schemes for solutions of such problems. One long-term goal of the project is the construction of a self-consistent closure for Large Eddy Simulations (LES) of turbulent flows that explicitly exploits the tensor product approach's capability of capturing self-similar structures. Secondly, we focus on a mixed deterministic-stochastic subgrid scale modelling strategy currently under development for application in Finite Volume Large Eddy Simulation (LES) codes. Advanced methods of time series analysis for the databased construction of stochastic models with inherently non-stationary statistical properties and concepts of information theory based on a modified Akaike information criterion and on the Bayesian information criterion for the model discrimination are used to construct surrogate models for the non-resolved flux fluctuations. Vector-valued auto-regressive models with external influences form the basis for the modelling approach [1], [2], [4]. Here, we present the reconstruction capabilities of the two modeling approaches tested against 3D turbulent channel flow data computed by direct numerical simulation (DNS) for an incompressible, isothermal fluid at Reynolds number Reτ = 590 (computed by [3]). References [1] I
NASA Astrophysics Data System (ADS)
Goswami, M.; O'Connor, K. M.; Bhattarai, K. P.
2007-02-01
SummaryFlow simulation in ungauged catchments is presently regarded as one of the most challenging tasks in surface water hydrology. Many of the ungauged catchments are located in the headwaters of rivers in mountainous regions of the world having enormous potential for sustainable water resource development. However, due to inaccessibility, rugged and inhospitable terrain, and historical lack of foresight concerning the need to have these headwaters adequately gauged, their potential is not readily realizable. Many downstream sites also suffer from non-availability of site-specific data as even in countries having extensive networks of gauged stations data may not be available at sites where these are most needed. As predictive tools for water resources, water quality, natural hazard mitigation and water availability assessment are generally data-driven, the lack of adequate hydrometric records poses difficult problems for planners, engineers, managers, and stake-holders alike. In this study, a methodology is developed for flow simulation in ungauged catchments using a regionalisation and multi-model approach involving a suite of rainfall-runoff models and combination techniques. Daily observed hydrometeorological data for 12 French catchments are used for illustrating the procedures. Following a preliminary investigation of the regional homogeneity of that group of catchments, three regional flow simulation techniques are applied. Although all 12 catchments are gauged, initially each catchment is successively considered as being ungauged for the purpose of flow simulation in that catchment, their actual discharges being subsequently used for evaluating the performance of the flow estimation procedures for the catchment. The Nash-Sutcliffe efficiency index ( R2) is used for assessing and ranking the relative performances of the regionalisation-model couples to identify the most appropriate couple for the region. The final step of applying that couple to a truly
Essaid, H.I.
1986-01-01
A quasi-three dimensional finite difference model which simulates coupled, fresh water and salt water flow, separated by a sharp interface, is used to investigate the effects of storage characteristics, transmissivity, boundary conditions and anisotropy on the transient responses of such flow systems. The magnitude and duration of the departure of aquifer response from the behavior predicted using the Ghyben-Herzberg, one-fluid approach is a function of the ease with which flow can be induced in the salt water region. In many common hydrogeologic settings short-term fresh water head responses, and transitional responses between short-term and long-term, can only be realistically reproduced by including the effects of salt water flow on the dynamics of coastal flow systems. The coupled fresh water-salt water flow modeling approach is able to reproduce the observed annual fresh water head response of the Waialae aquifer of southeastern Oahu, Hawaii. ?? 1986.
NASA Astrophysics Data System (ADS)
Lin, Yi-Kuei; Yeh, Cheng-Ta
2013-03-01
Many real-life systems, such as computer systems, manufacturing systems and logistics systems, are modelled as stochastic-flow networks (SFNs) to evaluate network reliability. Here, network reliability, defined as the probability that the network successfully transmits d units of data/commodity from an origin to a destination, is a performance indicator of the systems. Network reliability maximization is a particular objective, but is costly for many system supervisors. This article solves the multi-objective problem of reliability maximization and cost minimization by finding the optimal component assignment for SFN, in which a set of multi-state components is ready to be assigned to the network. A two-stage approach integrating Non-dominated Sorting Genetic Algorithm II and simple additive weighting are proposed to solve this problem, where network reliability is evaluated in terms of minimal paths and recursive sum of disjoint products. Several practical examples related to computer networks are utilized to demonstrate the proposed approach.
NASA Technical Reports Server (NTRS)
Daywitt, J.; Kutler, P.; Anderson, D.
1977-01-01
The technique of floating shock fitting is adapted to the computation of the inviscid flowfield about circular cones in a supersonic free stream at angles of attack that exceed the cone half-angle. The resulting equations are applicable over the complete range of free-stream Mach numbers, angles of attack and cone half-angles for which the bow shock is attached. A finite difference algorithm is used to obtain the solution by an unsteady relaxation approach. The bow shock, embedded cross-flow shock, and vortical singularity in the leeward symmetry plane are treated as floating discontinuities in a fixed computational mesh. Where possible, the flowfield is partitioned into windward, shoulder, and leeward regions with each region computed separately to achieve maximum computational efficiency. An alternative shock fitting technique which treats the bow shock as a computational boundary is developed and compared with the floating-fitting approach. Several surface boundary condition schemes are also analyzed.
NASA Astrophysics Data System (ADS)
Jackson, A. S.; Rybak, I.; Helmig, R.; Gray, W. G.; Miller, C. T.
2012-06-01
This work is the ninth in a series of papers on the thermodynamically constrained averaging theory (TCAT) approach for modeling flow and transport phenomena in multiscale porous medium systems. A fundamental approach is developed to model the transition region between a two-fluid-phase porous medium system and a single-fluid-phase system, including species transport. A general model formulation is developed along with an entropy inequality to guide the specification of closure relations. The general model formulation and entropy inequality are then used to specify a closed system. The transition region model developed in this work is a generalization and extension of coupling conditions commonly used in sharp interface models. The theoretical framework has multiple areas of potential applicability including terrestrial-atmospheric contact zones, surface water-sediment interface zones, and industrial drying processes.
A regression approach to the analysis of serial peak flow among fuel oil ash exposed workers.
Hauser, R; Daskalakis, C; Christiani, D C
1996-10-01
We investigated the association between exposure to fuel oil ash and acute airway obstruction in 31 boilermakers and 31 utility workers during the overhaul of a large oil-fired boiler. Air flow was assessed with self-recorded serial peak expiratory flow rate measurements (PEFR) using a mini-Wright meter. Exposure to thoracic particulates with an aerodynamic diameter of 10 gm or smaller (PM10) was assessed using personal sampling devices and detailed work diaries. All subjects were male, with an average age of 43 yr, and an average of 18 yr at their current trade. Average PM10 exposure on work days was 2.75 mg/m3 for boilermakers and 0.57 mg/m3 for utility workers. Three daily PEFR measurements (start-of-shift, end-of-shift, and bed-time) were analyzed simultaneously, using Huber linear regression. After adjustment for job title, welder status, age, height, smoking, and weld-years, for each mg/m3 increase in PM10, the estimated decline in PEFR was 13.2 L/min (p = 0.008) for end-of-shift, 9.9 L/min (p = 0.045) for bed-time, and 6.6 L/min (p = 0.26) for start-of-shift of the following day. This decline of the exposure effect over the 24-h period that follows was statistically significant (p = 0.004). No other factors were found to significantly modify the effect of exposure. Our results suggest that occupational exposure to fuel oil ash is associated with significant acute decrements in peak flow. PMID:8887594
Pharmacological Approaches That Slow Lymphatic Flow As a Snakebite First Aid
van Helden, Dirk F.; Thomas, Paul A.; Dosen, Peter J.; Imtiaz, Mohammad S.; Laver, Derek R.; Isbister, Geoffrey K.
2014-01-01
Background This study examines the use of topical pharmacological agents as a snakebite first aid where slowing venom reaching the circulation prevents systemic toxicity. It is based on the fact that toxin molecules in most snake venoms are large molecules and generally first enter and traverse the lymphatic system before accessing the circulation. It follows on from a previous study where it was shown that topical application of a nitric oxide donor slowed lymph flow to a similar extent in humans and rats as well as increased the time to respiratory arrest for subcutaneous injection of an elapid venom (Pseudonaja textilis, Ptx; Eastern brown snake) into the hind feet of anaesthetized rats. Methodology/Principal Findings The effects of topical application of the L-type Ca2+ channel antagonist nifedipine and the local anesthetic lignocaine in inhibiting lymph flow and protecting against envenomation was examined in an anaesthetized rat model. The agents significantly increased dye-measured lymph transit times by 500% and 390% compared to controls and increased the time to respiratory arrest to foot injection of a lethal dose of Ptx venom by 60% and 40% respectively. The study also examined the effect of Ptx venom dose over the lethal range of 0.4 to 1.5 mg/kg finding a negative linear relationship between increase in venom dose and time to respiratory arrest. Conclusions/Significance The findings suggest that a range of agents that inhibit lymphatic flow could potentially be used as an adjunct treatment to pressure bandaging with immobilization (PBI) in snakebite first aid. This is important given that PBI (a snakebite first aid recommended by the Australian National Health and Medical research Council) is often incorrectly applied. The use of a local anesthetic would have the added advantage of reducing pain. PMID:24587472
Zaccariello, Lucio; Cremiato, Raffaele; Mastellone, Maria Laura
2015-10-01
The main role of a waste management plan is to define which is the combination of waste management strategies and method needed to collect and manage the waste in such a way to ensure a given set of targets is reached. Objectives have to be sustainable and realistic, consistent with the environmental policies and regulations and monitored to verify the progressive achievement of the given targets. To get the aim, the setting up and quantification of indicators can allow the measurement of efficiency of a waste management system. The quantification of efficiency indicators requires the developing of a material flow analysis over the system boundary, from waste collection to secondary materials selling, processing and disposal. The material flow analysis has been carried out with reference to a case study for which a reliable, time- and site-specific database was available. The material flow analysis allowed the evaluation of the amount of materials sent to recycling, to landfilling and to waste-to-energy, by highlighting that the sorting of residual waste can further increase the secondary materials amount. The utilisation of energy recovery to treat the low-grade waste allows the maximisation of waste diversion from landfill with a low production of hazardous ash. A preliminary economic balance has been carried out to define the gate fee of the waste management system that was in the range of 84-145 € t(-1) without including the separate collection cost. The cost of door-by-door separate collection, designed to ensure the collection of five separate streams, resulted in 250 € t(-1) ±30%. PMID:26253498
FISH-Flow: a quantitative molecular approach for describing mixed clade communities of Symbiodinium
NASA Astrophysics Data System (ADS)
McIlroy, S. E.; Smith, G. J.; Geller, J. B.
2014-03-01
Our understanding of reef corals and their fate in a changing climate is limited by our ability to monitor the diversity and abundance of the dinoflagellate endosymbionts that sustain them. This study combined two well-known methods in tandem: fluorescent in situ hybridization (FISH) for genotype-specific labeling of Symbiodinium and flow cytometry to quantify the abundance of each symbiont clade in a sample. This technique (FISH-Flow) was developed with cultured Symbiodinium representing four distinct clades (based on large subunit rDNA) and was used to distinguish and quantify these types with high efficiency and few false positives. This technique was also applied to freshly isolated symbionts of Orbicella faveolata and Orbicella annularis. Isolates from acutely bleached coral tissues had significantly lower labeling efficiency; however, isolates from healthy tissue had efficiencies comparable to cultured Symbiodinium trials. RNA degradation in bleaching samples may have interfered with labeling of cells. Nevertheless, we were able to determine that, with and without thermal stress, experimental columns of the coral O. annularis hosted a majority of clade B and B/C symbionts on the top and side of the coral column, respectively. We demonstrated that, for cultured Symbiodinium and Symbiodinium freshly isolated from healthy host tissues, the relative ratio of clades could be accurately determined for clades present at as low as 7 % relative abundance. While this method does not improve upon PCR-based techniques in identifying clades at background levels, FISH-Flow provides a high precision, flexible system for targeting, quantifying and isolating Symbiodinium genotypes of interest.
Enhancing Knowledge Flow in a Health Care Context: A Mobile Computing Approach
Souza, Diego Da Silva; de Lima, Patrícia Zudio; da Silveira, Pedro C; de Souza, Jano Moreira
2014-01-01
Background Advances in mobile computing and wireless communication have allowed people to interact and exchange knowledge almost anywhere. These technologies support Medicine 2.0, where the health knowledge flows among all involved people (eg, patients, caregivers, doctors, and patients’ relatives). Objective Our paper proposes a knowledge-sharing environment that takes advantage of mobile computing and contextual information to support knowledge sharing among participants within a health care community (ie, from patients to health professionals). This software environment enables knowledge exchange using peer-to-peer (P2P) mobile networks based on users’ profiles, and it facilitates face-to-face interactions among people with similar health interests, needs, or goals. Methods First, we reviewed and analyzed relevant scientific articles and software apps to determine the current state of knowledge flow within health care. Although no proposal was capable of addressing every aspect in the Medicine 2.0 paradigm, a list of requirements was compiled. Using this requirement list and our previous works, a knowledge-sharing environment was created integrating Mobile Exchange of Knowledge (MEK) and the Easy to Deploy Indoor Positioning System (EDIPS), and a twofold qualitative evaluation was performed. Second, we analyzed the efficiency and reliability of the knowledge that the integrated MEK-EDIPS tool provided to users according to their interest topics, and then performed a proof of concept with health professionals to determine the feasibility and usefulness of using this solution in a real-world scenario. Results . Using MEK, we reached 100% precision and 80% recall in the exchange of files within the peer-to-peer network. The mechanism that facilitated face-to-face interactions was evaluated by the difference between the location indicated by the EDIPS tool and the actual location of the people involved in the knowledge exchange. The average distance error was <6
NASA Technical Reports Server (NTRS)
Van Dalsem, W. R.; Steger, J. L.
1983-01-01
A new, fast, direct-inverse, finite-difference boundary-layer code has been developed and coupled with a full-potential transonic airfoil analysis code via new inviscid-viscous interaction algorithms. The resulting code has been used to calculate transonic separated flows. The results are in good agreement with Navier-Stokes calculations and experimental data. Solutions are obtained in considerably less computer time than Navier-Stokes solutions of equal resolution. Because efficient inviscid and viscous algorithms are used, it is expected this code will also compare favorably with other codes of its type as they become available.
NASA Astrophysics Data System (ADS)
Wu, D.; Qiu, Zhi P.
2011-05-01
Two non-probabilistic, set-theoretical methods for determining the energy flow between two structural multimodal systems coupled by a joint with uncertain parameters are presented. They are based on the theories of interval mathematics and convex models. The uncertain parameters of the joint are assumed to be a convex set, hyper-rectangle or ellipsoid. For both non-probabilistic methods, less prior information about the uncertain nature is required than that which is required concerning the probabilistic model. The properties of the standard interval arithmetic, the interval Taylor expansion, the convex models and the Monte Carlo Method solutions are investigated and compared.
Insect-Inspired Self-Motion Estimation with Dense Flow Fields—An Adaptive Matched Filter Approach
Strübbe, Simon; Stürzl, Wolfgang; Egelhaaf, Martin
2015-01-01
The control of self-motion is a basic, but complex task for both technical and biological systems. Various algorithms have been proposed that allow the estimation of self-motion from the optic flow on the eyes. We show that two apparently very different approaches to solve this task, one technically and one biologically inspired, can be transformed into each other under certain conditions. One estimator of self-motion is based on a matched filter approach; it has been developed to describe the function of motion sensitive cells in the fly brain. The other estimator, the Koenderink and van Doorn (KvD) algorithm, was derived analytically with a technical background. If the distances to the objects in the environment can be assumed to be known, the two estimators are linear and equivalent, but are expressed in different mathematical forms. However, for most situations it is unrealistic to assume that the distances are known. Therefore, the depth structure of the environment needs to be determined in parallel to the self-motion parameters and leads to a non-linear problem. It is shown that the standard least mean square approach that is used by the KvD algorithm leads to a biased estimator. We derive a modification of this algorithm in order to remove the bias and demonstrate its improved performance by means of numerical simulations. For self-motion estimation it is beneficial to have a spherical visual field, similar to many flying insects. We show that in this case the representation of the depth structure of the environment derived from the optic flow can be simplified. Based on this result, we develop an adaptive matched filter approach for systems with a nearly spherical visual field. Then only eight parameters about the environment have to be memorized and updated during self-motion. PMID:26308839
Xu, Tianfu; White, Stephen P.; Pruess, Karsten
1998-02-15
Pyrite (FeS{sub 2}) is one of the most common naturally occurring minerals that is present in many subsurface environments. It plays an important role in the genesis of enriched ore deposits through weathering reactions, is the most abundant sulfide mineral in many mine tailings, and is the primary source of acid drainage from mines and waste rock piles. The pyrite oxidation reaction serves as a prototype for oxidative weathering processes with broad significance for geoscientific, engineering, and environmental applications. Mathematical modeling of these processes is extremely challenging because aqueous concentrations of key species vary over an enormous range, oxygen inventory and supply are typically small in comparison to pyrite inventory, and chemical reactions are complex, involving kinetic control and microbial catalysis. We present the mathematical formulation of a general multi-phase advective-diffusive reactive transport model for redox processes. Two alternative implementations were made in the TOUGHREACT and TOUGH2-CHEM simulation codes which use sequential iteration and simultaneous solution, respectively. The simulators are applied to reactive consumption of pyrite in (1) saturated flow of oxidizing water, and (2) saturated-unsaturated flow in which oxygen transport occurs in both aqueous and gas phases. Geochemical evolutions predicted from different process models are compared, and issues of numerical accuracy and efficiency are discussed.
Control of laminar wake flows using the Sum-of-Squares approach
NASA Astrophysics Data System (ADS)
Lasagna, Davide; Tutty, Owen; Huang, Deqing; Chernyshenko, Sergei
2015-11-01
A novel feedback control design methodology for finite-dimensional, reduced-order models of incompressible turbulent fluid flows, aiming at reduction of long-time averages of key quantities, is presented. The key enabler is a recent advance in control design for systems with polynomial dynamics, i.e. the discovery that the Sum-of-Squares decomposition of a non-negative polynomial, or the construction of one of such functions, can be computed via semidefinite programming techniques. Firstly, the theoretical difficulties of treating long-time averages are relaxed by abstracting the analysis to upper bounds of such averages. Then, the problems of estimation and optimisation via control design of these bounds are conveniently reformulated into constructing suitable non-negative polynomial functions, using Sum-of-Squares programming techniques. To showcase the methodology, linear and nonlinear polynomial-type state-feedback controllers are designed to reduce the fluctuations kinetic energy in the wake of a circular cylinder at Re = 100 , using rotary oscillations. A compact, reduced-order Galerkin model of the actuated wake is first derived using Proper Orthogonal Decomposition. Controllers are then designed and implemented in direct numerical simulations of the flow.
NASA Astrophysics Data System (ADS)
Redapangu, Prasanna; Vanka, Pratap; Sahu, Kirti
2012-11-01
The pressure-driven displacement of two immiscible fluids in an inclined channel in the presence of viscosity and density gradients is investigated using a multiphase lattice Boltzmann approach. The effects of viscosity ratio, Atwood number, Froude number, capillary number and channel inclination are investigated through flow structures, front velocities and fluid displacement rates. Our results indicate that increasing viscosity ratio between the fluids decreases the displacement rate. We observe that increasing the viscosity ratio has a non-monotonic effect on the velocity of the leading front; however, the velocity of the trailing edge decreases with increasing the viscosity ratio. The displacement rate of the thin-layers formed at the later times of the displacement process increases with increasing the angle of inclination because of the increase in the intensity of the interfacial instabilities. Our results also predict the front velocity of the lock-exchange flow of two immiscible fluids in the exchange flow dominated regime. Department of Science and Technology, India.
Dynamic gas slippage: A unique dual-mechanism approach to the flow of gas in tight formations
Ertekin; King, G.R.; Schwerer, F.C.
1983-10-01
A mathematical formulation, applicable to both numerical simulation and transient well analysis, describing the flow of gas in very tight (k < 0.1 md) porous media has been developed. Unique to this formulation is the dual-mechanism transport of gas. In this formulation gas is assumed to be traveling under the influence of two fields: a concentration field and a pressure field. Transport through the concentration field is a Knudsen flow process and is modeled with Fick's Law of diffusion. Transport through the pressure field is a laminar process and is modeled with Darcy's law (inertial-turbulent effects are ignored). The combination of these two flow mechanisms rigorously yields a composition, pressure and saturation dependent slippage factor. The pressure dependence arises from treating the gas as a real gas. The dynamic slippage derived from this formulation is found to be most applicable in reservoirs with permeabilities less than or equal to 0.01 md. The results from this study indicate that in reservoirs of this type, differences between recoveries after ten years of production using the dynamic slip described in this paper and constant slip approaches were as great as 10% depending on the initial gas saturation. If an economic production rate is considered, differences as great as 30 can be expected.
Dynamic gas slippage: A unique dual-mechanism approach to the flow of gas in tight formations
Ertekin, T.; King, G.R.; Schwerer, F.C.
1986-02-01
A mathematical formulation, applicable to both numerical simulation and transient well analysis that describes the flow of gas in very tight porous media and includes a dual-mechanism transport of gas is developed. Gas is assumed to be traveling under the influence of a concentration field and a pressure field. Transport through the concentration field is a Knudsen flow process and is modeled with Fick's law of diffusion. Transport through the pressure field is a laminar process and is modeled with Darcy's law (inertial/turbulent effects are ignored). The combination of these two flow mechanisms rigorously yields a composition-, pressure-, and saturation-dependent slippage factor. The pressure dependence arises from treating the gas as a real gas. The derived dynamic slippage is most applicable in reservoirs with permeabilities less than or equal to0.01 md. The results indicate that in reservoirs of this type, differences between recoveries after 10 years of production with the dynamic-slip and constant-slip approaches were as great as 10%, depending on the initial gas saturation. If an economic production rate is considered, differences as great as 30% can be expected.
Knoeri, Christof; Wäger, Patrick A; Stamp, Anna; Althaus, Hans-Joerg; Weil, Marcel
2013-09-01
Emerging technologies such as information and communication-, photovoltaic- or battery technologies are expected to increase significantly the demand for scarce metals in the near future. The recently developed methods to evaluate the criticality of mineral raw materials typically provide a 'snapshot' of the criticality of a certain material at one point in time by using static indicators both for supply risk and for the impacts of supply restrictions. While allowing for insights into the mechanisms behind the criticality of raw materials, these methods cannot account for dynamic changes in products and/or activities over time. In this paper we propose a conceptual framework intended to overcome these limitations by including the dynamic interactions between different possible demand and supply configurations. The framework integrates an agent-based behaviour model, where demand emerges from individual agent decisions and interaction, into a dynamic material flow model, representing the materials' stocks and flows. Within the framework, the environmental implications of substitution decisions are evaluated by applying life-cycle assessment methodology. The approach makes a first step towards a dynamic criticality assessment and will enhance the understanding of industrial substitution decisions and environmental implications related to critical metals. We discuss the potential and limitation of such an approach in contrast to state-of-the-art methods and how it might lead to criticality assessments tailored to the specific circumstances of single industrial sectors or individual companies. PMID:23453658
A data-driven approach for modeling post-fire debris-flow volumes and their uncertainty
Friedel, M.J.
2011-01-01
This study demonstrates the novel application of genetic programming to evolve nonlinear post-fire debris-flow volume equations from variables associated with a data-driven conceptual model of the western United States. The search space is constrained using a multi-component objective function that simultaneously minimizes root-mean squared and unit errors for the evolution of fittest equations. An optimization technique is then used to estimate the limits of nonlinear prediction uncertainty associated with the debris-flow equations. In contrast to a published multiple linear regression three-variable equation, linking basin area with slopes greater or equal to 30 percent, burn severity characterized as area burned moderate plus high, and total storm rainfall, the data-driven approach discovers many nonlinear and several dimensionally consistent equations that are unbiased and have less prediction uncertainty. Of the nonlinear equations, the best performance (lowest prediction uncertainty) is achieved when using three variables: average basin slope, total burned area, and total storm rainfall. Further reduction in uncertainty is possible for the nonlinear equations when dimensional consistency is not a priority and by subsequently applying a gradient solver to the fittest solutions. The data-driven modeling approach can be applied to nonlinear multivariate problems in all fields of study. ?? 2011.
NASA Technical Reports Server (NTRS)
James, R. M.; Clark, R. W.
1979-01-01
An approach to the solution of matrix problems resulting from integral equations of mathematical physics is presented. Based on the inherent smoothness in such equations, the problem is reformulated using a set of orthogonal basis vectors, leading to an equivalent coefficient problem which can be of lower order without significantly impairing the accuracy of the solution. This approach was evaluated using a two-dimensional Neumann problem describing the inviscid, incompressible flow over an airfoil. Two different kinds of mode functions were investigated, namely eigenfunction series and Fourier series. The method using Fourier series was found preferable. It uses all of the coefficients from a Fast Fourier Transform algorithm in an approximate method which exploits the known structure of the transformed coefficient matrix and very promising results for the flow over a realistic airfoil are obtained. On the basis of the results presented here, an order of magnitude reduction in this computer time can be expected for such problems as compared with the time for a direct matrix solution.
NASA Astrophysics Data System (ADS)
Ganesh, Rajaraman; Charan, Harish
2016-07-01
Understanding vortical flows under external forcing in two dimensional (2D) fluids is a fundamental paradigm for structure formation in driven, dissipative systems. Considering Yukawa liquid as a prototype for strongly correlated or strongly coupled plasmas characterized by coupling strength (Γ, the ratio of average potential to kinetic energy per particle) and screening parameter (κ, ratio of mean inter-particle distance to shielding length), we address two important problems: 1. Onset of Rayleigh Benard convection cell (RBCC) in 2D Yukawa liquids subject to gravity and external temperature gradient 2. Onset of von Karman vortices in 2D Yukawa liquid under external pressure head, using large scale, first principles molecular dynamics simulations. For typical values of (Γ,κ), existence of a critical external temperature difference is demonstrated, beyond which RBCC are seen to set in. Beyond this critical external temperature difference, the strength of the maximum convective flow velocity is shown to exhibit a new, hitherto unsuspected linear relationship with external temperature difference and with a slope independent of (Γ,κ). The time taken for the transients to settle down to a steady state RBCC τ_s, is found to be maximum close to the above said critical external temperature difference and is seen to reduce with increasing external temperature difference. For the range of values of (Γ, κ) considered here, τ_s ≃ 10 000-20 000;ω^{-1}_{pd}, where ω_{pd} is dust plasma frequency. As Γ is increased to very high values, due to strong coupling effects, RBC cells are seen to be in a transient state without attaining a steady state for as long as 100 000;ω^{-1}_{pd}, even for a very high external temperature difference. In the second part, we address the existence of universal relation between Strouhal (St) and Rayleigh (Ry) numbers for Yukawa liquid using first principles based classical molecular dynamics. The flow past an obstacle is seen to indeed
NASA Astrophysics Data System (ADS)
Zhu, Jianting; Ogden, Fred L.; Lai, Wencong; Chen, Xiangfeng; Talbot, Cary A.
2016-04-01
Vadose zone flow problems are usually solved from the Richards equation. Solution to the Richards equation is generally challenging because the hydraulic conductivity and diffusivity in the equation are strongly non-linear functions of water content. The finite water-content method was proposed as an alternative general solution method of the vadose zone flow problem for infiltration, falling slugs, and vadose zone response to water table dynamics based on discretizing the water content domain into numerous bins instead of the traditional spatial discretization. In this study, we develop an improved approach to the original finite water-content method (referred to as TO method hereinafter) that better simulates diffusive effects but retains the robustness of the TO method. The approach treats advection and diffusion separately and considers diffusion on a bin by bin basis. After discretizing into water content bins, we treat the conductivity and diffusivity in individual bins as water content dependent constant evaluated at given water content corresponding to each bin. For each bin, we can solve the flow equations analytically since the hydraulic conductivity and diffusivity can be treated as a constant. We then develop solutions for each bin to determine the diffusive water amounts at each time step. The water amount ahead of the convective front for each bin is redistributed among water content bins to account for diffusive effects. The application of developed solution is straightforward only involving algebraic manipulations at each time step. The method can mainly improve water content profiles, but has no significant difference for the total infiltration rate and cumulative infiltration compared to the TO method. Although the method separately deals with advection and diffusion, it can account for the coupling effects of advection and diffusion reasonably well.
NASA Astrophysics Data System (ADS)
Segalini, Andrea; Ferrero, Anna Maria; Brighenti, Roberto
2013-04-01
A channelized debris flow is usually represented by a mixture of solid particles of various sizes and water, flowing along a laterally confined inclined channel-shaped region up to an unconfined area where it slow down its motion and spreads out into a flat-shaped mass. The study of these phenomena is very difficult due to their short duration and unpredictability, lack of historical data for a given basin and complexity of the involved mechanical phenomena. The post event surveys allow for the identification of some depositional features and provide indication about the maximum flow height; however they lack information about development of the phenomena with time. For this purpose the monitoring of recursive events has been carried out by several Authors. Most of the studies, aimed at the determination of the characteristic features of a debris flow, were carried out in artificial channels, where the main involved variables were measured and other where controlled during the tests; however, some uncertainties remained and other scaled models where developed to simulate the deposition mechanics as well as to analyze the transportation mechanics and the energy dissipation. The assessment of the mechanical behavior of the protection structures upon impact with the flow as well as the energy associated to it are necessary for the proper design of such structures that, in densely populated area, can avoid victims and limit the destructive effects of such a phenomenon. In this work a simplified structural model, developed by the Authors for the safety assessment of retention barrier against channelized debris flow, is presented and some parametric cases are interpreted through the proposed approach; this model is developed as a simplified and efficient tool to be used for the verification of the supporting cables and foundations of a flexible debris flow barrier. The present analytical and numerical-based approach has a different aim of a FEM model. The computational
The sensitivity of orographic precipitation to flow direction: An idealized modeling approach
NASA Astrophysics Data System (ADS)
Picard, Lee
A method is developed for forcing a full-physics, full-terrain model with an idealized, balanced atmosphere determined by an input sounding. The initialization technique is applied to investigate the sensitivity of orographic precipitation in Pacific Northwest terrain to wind direction under both barotropic and sheared flow conditions approximating an atmospheric river. The model results agree well with previous studies that considered typical conditions resulting in heavy precipitation, with the precipitation sensitivity to wind direction less than is estimated for similar deterministic cases. To explore the causes of sensitivity in the Olympic Mountains of western Washington State, additional experiments are carried out using modified terrain fields with smoothed or idealized Olympic Mountains, or with nearby orography removed. Model simulations suggest that the sensitivity of Olympic Mountain precipitation to wind direction is more strongly modulated by the presence of surrounding orography than by the specific Olympic geometry.
Chemical and biological activity in open flows: A dynamical system approach
NASA Astrophysics Data System (ADS)
Tél, Tamás; de Moura, Alessandro; Grebogi, Celso; Károlyi, György
2005-07-01
Chemical and biological processes often take place in fluid flows. Many of them, like environmental or microfluidical ones, generate filamentary patterns which have a fractal structure, due to the presence of chaos in the underlying advection dynamics. In such cases, hydrodynamical stirring strongly couples to the reactivity of the advected species: the outcome of the reaction is then typically different from that of the same reaction taking place in a well-mixed environment. Here we review recent progress in this field, which became possible due to the application of methods taken from dynamical system theory. We place special emphasis on the derivation of effective rate equations which contain singular terms expressing the fact that the reaction takes place on a moving fractal catalyst, on the unstable foliation of the reaction free advection dynamics.
Assessing the ecological status of plankton in Anjos Bay: a flow cytometry approach
NASA Astrophysics Data System (ADS)
Pereira, G. C.; de Figuiredo, A. R.; Jabor, P. M.; Ebecken, N. F. F.
2010-08-01
This aim of this paper is to assess the use of the heterotrophic/autotrophic ratio as an early indicator of trophic status as a part of development of a real time monitoring program at Anjos Bay, Rio de Janeiro, Brazil. An in-situ flow cytometer was used to quantify the abundances of phytoplankton and cyanobacteria, which were identified by chlorophyll and phycoerythrin autofluorescence, respectively. Heterotrophic prokaryotes and viruses were quantified by DNA-binding fluorochromes; merozooplankton larvae were collected by plankton net and quantified by stereomicroscopy. The temporal and spatial distributions of these variables were evaluated on the basis of weekly observations from August 2006 to September 2007. The heterotrophic/autotrophic ratio and the viral abundance were correlated with upwelling events and assume an apparently seasonal pattern. A possible control mechanism and influential factors are discussed, and it is concluded that this ecosystem is bottom-up controlled under eutrophic conditions and top-down controlled under oligotrophic conditions.
Kozak, Joanna; Wójtowicz, Marzena; Gawenda, Nadzieja; Kościelniak, Paweł
2011-06-15
An automatic sequential injection system, combining monosegmented flow analysis, sequential injection analysis and sequential injection titration is proposed for acidity determination. The system enables controllable sample dilution and generation of standards of required concentration in a monosegmented sequential injection manner, sequential injection titration of the prepared solutions, data collecting, and handling. It has been tested on spectrophotometric determination of acetic, citric and phosphoric acids with sodium hydroxide used as a titrant and phenolphthalein or thymolphthalein (in the case of phosphoric acid determination) as indicators. Accuracy better than |4.4|% (RE) and repeatability better than 2.9% (RSD) have been obtained. It has been applied to the determination of total acidity in vinegars and various soft drinks. The system provides low sample (less than 0.3 mL) consumption. On average, analysis of a sample takes several minutes. PMID:21641455
CFD approach to flow-induced vibrations of tandemly placed circular cylinders
NASA Astrophysics Data System (ADS)
Nishikawa, Naoki; Someya, Satoshi; Okamoto, Koji
2012-03-01
In the present study, we numerically examined the vibration characteristics of two cylinders which were placed tandemly in close vicinity of each other. The center-to-center pitch between the cylinders was four times the diameter of the cylinders. The cylinders were modeled as rigid bodies with two degrees-of-freedom in the simulation. The vibration frequencies of the cylinders were calculated, with the reduced velocity being varied. The vortex formation process was observed with regard to reduced velocity and structural damping. Also, the effects of the reduced velocity of the flow, the eigenfrequency of the cylinder, and the structural damping of the cylinder on the vibration response were discussed. A comparison was made between numerical results and the experimental ones obtained by means of the high-speed particle image velocimetry (Dynamic PIV) measurement.
NASA Astrophysics Data System (ADS)
Cybyk, Bohdan Zynowij
Accurate and affordable numerical methods play a vital role in the design and development of practical hypersonic vehicles. Existing analysis tools that provide aerothermodynamic properties for the high-altitude portion of a hypersonic vehicle's flight path are capable but expensive. This dissertation describes the development, validation, and application of a new tool aimed at expanding the practical analysis envelope of high Knudsen number flows. The present work is the first to combine the Direct Simulation Monte Carlo (DSMC) methodology with a Lagrangian data structure, the Monotonic Lagrangian Grid (MLG). The result is a numerical approach for transition regime flows that automatically adjusts grid resolution to time-varying densities in the flow. The DSMC method is a direct particle simulation technique widely used in predicting flows of dilute gases. The MLG algorithm combines an efficient tracking and sorting scheme with a monotonic data structure for indexing and storing physical attributes of the moving particles. Monotonicity features of the MLG ensure that particles close in physical space are stored in adjacent array locations so that particle interactions may be restricted to a 'template' of near neighbors. The MLG templates provide a time-varying grid network that automatically adapts to local number densities within the flowfield. The majority of MLG and DSMC logic is inherently parallel, enabling extremely efficient application on parallel computer architectures. Computational advantages and disadvantages of this new MLG-based implementation are demonstrated by a series of test problems. The effects of MLG sorting parameters on computational performance are investigated, and results from sensitivity studies on grid size and template size are presented. The combination of DSMC and MLG results in a new tool with several significant benefits, including an automatically adapting grid, improved prediction accuracy for a given grid size, and decreased
NASA Astrophysics Data System (ADS)
Ezzedine, S. M.
2009-12-01
Fractures and fracture networks are the principal pathways for transport of water and contaminants in groundwater systems, enhanced geothermal system fluids, migration of oil and gas, carbon dioxide leakage from carbon sequestration sites, and of radioactive and toxic industrial wastes from underground storage repositories. A major issue to overcome when characterizing a fractured reservoir is that of data limitation due to accessibility and affordability. Moreover, the ability to map discontinuities in the rock with available geological and geophysical tools tends to decrease particularly as the scale of the discontinuity goes down. Geological characterization data include measurements of fracture density, orientation, extent, and aperture, and are based on analysis of outcrops, borehole optical and acoustic televiewer logs, aerial photographs, and core samples, among other techniques. All of these measurements are taken at the field scale through a very sparse limited number of deep boreholes. These types of data are often reduced to probability distribution functions for predictive modeling and simulation in a stochastic framework such as a stochastic discrete fracture network. Stochastic discrete fracture network models enable, through Monte Carlo realizations and simulations, probabilistic assessment of flow and transport phenomena that are not adequately captured using continuum models. Despite the fundamental uncertainties inherited within the probabilistic reduction of the sparse data collected, very little work has been conducted on quantifying uncertainty on the reduced probabilistic distribution functions. In the current study, using nested Monte Carlo simulations, we present the impact of parameter uncertainties of the distribution functions of fracture density, orientation, aperture and size on the flow and transport using topological measures such as fracture connectivity, physical characteristics such as effective hydraulic conductivity tensors, and
NASA Astrophysics Data System (ADS)
Yuan, Feng; Gan, Zhaoming; Narayan, Ramesh; Sadowski, Aleksander; Bu, Defu; Bai, Xue-Ning
2015-05-01
Previous MHD simulations have shown that wind must exist in black hole hot accretion flows. In this paper, we continue our study by investigating the detailed properties of wind and the mechanism of wind production. For this aim, we make use of a 3D general relativistic MHD simulation of hot accretion flows around a Schwarzschild black hole. To distinguish real wind from turbulent outflows, we track the trajectories of the virtual Lagrangian particles from simulation data. We find two types of real outflows, i.e., a jet and a wind. The mass flux of wind is very significant, and its radial profile can be described by {{\\dot{M}}wind}≈ {{\\dot{M}}BH}≤ft( r/20 {{r}s} \\right), with {{\\dot{M}}BH} being the mass accretion rate at the black hole horizon and rs being the Schwarzschild radius. The poloidal wind speed almost remains constant once they are produced, but the flux-weighted wind speed roughly follows {{v}p,wind}(r)≈ 0.25{{v}k}(r), with vk(r) being the Keplerian speed at radius r. The mass flux of the jet is much lower, but the speed is much higher, {{v}p,jet} ˜ (0.3-0.4)c. Consequently, both the energy and momentum fluxes of the wind are much larger than those of the jet. The wind is produced and accelerated primarily by the combination of centrifugal force and magnetic pressure gradient, while the jet is mainly accelerated by the magnetic pressure gradient. Finally, we find that the wind production efficiency {{ɛ }wind}\\equiv {{\\dot{E}}wind}/{{\\dot{M}}BH}{{c}2}˜ 1/1000 is in good agreement with the value required from large-scale galaxy simulations with active galactic nucleus feedback.
NARX prediction of some rare chaotic flows: Recurrent fuzzy functions approach
NASA Astrophysics Data System (ADS)
Goudarzi, Sobhan; Jafari, Sajad; Moradi, Mohammad Hassan; Sprott, J. C.
2016-02-01
The nonlinear and dynamic accommodating capability of time domain models makes them a useful representation of chaotic time series for analysis, modeling and prediction. This paper is devoted to the modeling and prediction of chaotic time series with hidden attractors using a nonlinear autoregressive model with exogenous inputs (NARX) based on a novel recurrent fuzzy functions (RFFs) approach. Case studies of recently introduced chaotic systems with hidden attractors plus classical chaotic systems demonstrate that the proposed modeling methodology exhibits better prediction performance from different viewpoints (short term and long term) compared to some other existing methods.
Drag phenomena within a torque converter driven automotive transmission - laminar flow approach
NASA Astrophysics Data System (ADS)
Alexa, O.; Marinescu, M.; Olaru, Gh; Costache, D.; Ilie, C. O.; Vinturis, V.
2015-11-01
When discussing a torque converter driven, automotive transmission with respect to the vehicle's coasting mode, automotive engineers have to take into account the slip between the converter's propeller and turbine. If the turbine isn't locked to the propellers during coasting process, drag phenomena within the converter's fluid occur and they have to be properly assessed when computing the coasting process dynamics. The best way to make the needed evaluation is to have a separate torque converter and test it on a test bench, if the data provided by the manufacturer, in this respect, weren't available. But there are several issues that could baffle this action. Among them, one could find the lack of information from the manufacturer, missing (bankrupted) manufacturer, classified information, old (out of date) products and so on. An even more challenging situation consists in dealing with a military special vehicle. Actually, the vehicle that would be subjected to the following topic is a military tracked, heavy vehicle (MBT) with a planetary driveline, driven by its engine via a hydraulic torque converter. In the attempt to assess its’ coasting dynamic performances, we faced the problem of the reverse rotation of the torque converter that strongly influences the general drag of the vehicle's motion. Hence, this paper tries to provide a method to determine the transmission overall drag considering the torque converter as being its main contributor. The method is based on the experimental research our team has performed in the last several months. Using high-quality software and adjacent mathematics while assuming a certain sort of flow type within the torque converter, we aimed at determining the parameter of interest of the flow. The method can be successfully used for all type of hydrodynamic components of the transmission under the condition of developing the necessary experimental research. As far as the test were concerned, they were the typical ones designed
Predictions of axisymmetric free turbulent shear flows using a generalized eddy-viscosity approach
NASA Technical Reports Server (NTRS)
Morgenthaler, J. H.
1973-01-01
The generalized eddy viscosity approach is described and results are presented of test cases which show that predictions obtained by this approach are adequate for most engineering applications. Because of the importance of starting computations from the injection station where experimentally determined mean and turbulence parameters are rarely available, a very simple core model applicable to simple step-type (slug) profiles was developed. Agreement between predicted and experimental mean profiles was generally almost as good for calculations made by using this model throughout the core region and the transition model for all subsequent regions as predictions made by starting from experimental profiles in the transition region. The generalized eddy-viscosity model, which was developed in part through correlation of turbulence parameters, successfully predicted turbulent shear stress, turbulent intensity, and mean velocity profiles for a 0.040-inch-diameter microjet. Therefore, successful scaling by the model was demonstrated since data used in its development was for jet areas up to 90,000 times as large as the microjet and velocities only 1/20th as high.
Application of the multi distribution function lattice Boltzmann approach to thermal flows
NASA Astrophysics Data System (ADS)
Parmigiani, A.; Huber, C.; Chopard, B.; Latt, J.; Bachmann, O.
2009-04-01
Numerical methods able to model high Rayleigh ( Ra) and high Prandtl ( Pr) number thermal convection are important to study large-scale geophysical phenomena occuring in very viscous fluids such as magma chamber dynamics (104 < Pr < 107 and 107 < Ra < 1011). The important variable to quantify the thermal state of a convective fluid is a generalized dimensionless heat transfer coefficient (the Nusselt number) whose measure indicates the relative efficiency of the thermal convection. In this paper we test the ability of Multi-distribution Function approach (MDF) Thermal Lattice Boltzmann method to study the well-established scaling result for the Nusselt number ( Nu ∝ Ra 1/3) in Rayleigh Bénard convection for 104 ≤ Ra ≤ 109 and 101 ≤ Pr ≤ 104. We explore its main drawbacks in the range of Pr and Ra number under investigation: (1) high computational time N c required for the algorithm to converge and (2) high spatial accuracy needed to resolve the thickness of thermal plumes and both thermal and velocity boundary layer. We try to decrease the computational demands of the method using a multiscale approach based on the implicit dependence of the Pr number on the relaxation time, the spatial and temporal resolution characteristic of the MDF thermal model.
NASA Astrophysics Data System (ADS)
Popp, Andrea; Moeck, Christian; Radny, Dirk; Borer, Paul; Affolter, Annette; Epting, Jannis; Huggenberger, Peter; Auckenthaler, Adrian; Schirmer, Mario
2015-04-01
Drinking water supply in urban areas is challenging due to different kinds of water use and potential groundwater contamination. We investigate an area where drinking water production is close to different contaminated sites. The study site is characterized by a high complexity of the tectonic and geological setting with a gravel and a karstic aquifer. The two aquifers are partly connected, partly disconnected by an aquitard. To avoid drinking water contamination, artificial groundwater recharge with surface water into the gravel aquifer is used to create a hydraulic barrier between the contaminated sites and the water abstraction wells. Trace compounds, that were found in former times in the surface water but not nowadays, are still detected in the extracted drinking water. Different studies have been performed such as numerical modeling, intensive groundwater monitoring and investigation of drilling cores to get a differentiated overview of the distribution of the contaminants. Back-diffusion from the matrix due to changing hydraulic boundary was stated to be the reason for the actual distribution of the contaminants. In a first approach due to the lack of experimental data or evidence from field measurements, the permeabilities of the karstic aquifer were assumed as homogeneous. In our study, we seek to identify the flow and transport processes within the system including the fracture network in a combined approach of field work and 3D modeling with FEFLOW. During a field campaign we acquired water samples for the analysis of stable water isotopes as well as organic and inorganic compounds. Furthermore, tritium and helium samples were taken to estimate water ages and to determine the flow through the fracture networks. A combination of existing and recently obtained data was used to build and validate a 3D flow and transport model. The simulation of different scenarios such as the water flow for varying injection and extraction rates as well as particle
NASA Astrophysics Data System (ADS)
Amiri Delouei, A.; Nazari, M.; Kayhani, M. H.; Kang, S. K.; Succi, S.
2016-04-01
In the current study, a direct-forcing immersed boundary-non-Newtonian lattice Boltzmann method (IB-NLBM) is developed to investigate the sedimentation and interaction of particles in shear-thinning and shear-thickening fluids. In the proposed IB-NLBM, the non-linear mechanics of non-Newtonian particulate flows is detected by combination of the most desirable features of immersed boundary and lattice Boltzmann methods. The noticeable roles of non-Newtonian behavior on particle motion, settling velocity and generalized Reynolds number are investigated by simulating benchmark problem of one-particle sedimentation under the same generalized Archimedes number. The effects of extra force due to added accelerated mass are analyzed on the particle motion which have a significant impact on shear-thinning fluids. For the first time, the phenomena of interaction among the particles, such as Drafting, Kissing, and Tumbling in non-Newtonian fluids are investigated by simulation of two-particle sedimentation and twelve-particle sedimentation. The results show that increasing the shear-thickening behavior of fluid leads to a significant increase in the kissing time. Moreover, the transverse position of particles for shear-thinning fluids during the tumbling interval is different from Newtonian and the shear-thickening fluids. The present non-Newtonian particulate study can be applied in several industrial and scientific applications, like the non-Newtonian sedimentation behavior of particles in food industrial and biological fluids.
An Experimenting Field Approach for the Numerical Solution of Multiphase Flow in Porous Media.
Salama, Amgad; Sun, Shuyu; Bao, Kai
2016-03-01
In this work, we apply the experimenting pressure field technique to the problem of the flow of two or more immiscible phases in porous media. In this technique, a set of predefined pressure fields are introduced to the governing partial differential equations. This implies that the velocity vector field and the divergence at each cell of the solution mesh can be determined. However, since none of these fields is the true pressure field entailed by the boundary conditions and/or the source terms, the divergence at each cell will not be the correct one. Rather the residue which is the difference between the true divergence and the calculated one is obtained. These fields are designed such that these residuals are used to construct the matrix of coefficients of the pressure equation and the right-hand side. The experimenting pressure fields are generated in the solver routine and are fed to the different routines, which may be called physics routines, which return to the solver the elements of the matrix of coefficients. Therefore, this methodology separates the solver routines from the physics routines and therefore results in simpler, easy to construct, maintain, and update algorithms. PMID:26171913
NASA Technical Reports Server (NTRS)
Hong, M. S.; Carmichael, G. R.
1983-01-01
A flow-through chemical reactor model is developed to describe the mass transfer and chemical processes that atmospheric gases undergo in clouds. The model includes the simultaneous absorption of SO2, NH3, O3, NO(x), HNO3, CO2 and H2O2, the accompanying dissociation and oxidation reactions in cloud water, considers electrical neutrality, and includes qualitative parameterization of cloud microphysics. The model is used to assess the importance of the oxidation reactions H2O2-S(IV), O3-S(IV), and S(IV)-Mn(2+) catalysis, and the effects of cloud parameters such as drop size, rain intensity, liquid water content, and updraft velocity. Both precipitating and nonprecipitating clouds are studied. Model results predict sulfate production rates varying from 3 percent/hr to 230 percent/hr. The actual rate is highly dependent on the chemical composition of the uptake air and the physical conditions of the cloud. Model results also show that both the H2O2 and the O3 oxidation reactions can be significant.
Unstructured grid approach to numerical simulation of viscous flow around multielement airfoils
Sakovich, V.S.; Sorokin, A.M.
1996-12-31
The new direct action scheme is elaborated for approximation of two-dimensional Navier-Stokes equations on high cell aspect ratio (CAR) unstructured grids. This scheme employs the Voronoi cells as control volumes. For convective and viscous terms the scheme produces the conventional cross-type scheme on triangulated rectangular grids. The scheme approximates the additional integral representing the conservation of angular momentum. An accuracy of approximation of direct action scheme can be estimated by error functional specified at each grid point. This functional estimates the quality of unstructured grid for direct action scheme. The matrix dissipation is used for dumping odd-even instability of centered scheme. It combines the accuracy of upwind schemes with robustness and efficiency of centered ones. The construction of highly stretched Delaunay triangulations consists of two steps. At the first step nearly orthogonal structured high CAR grid is generated near bodies and wakes. At the second step this grid is smoothly continued inside the computational domain by incremental insertion technique. The calculation of turbulent viscous flows around single and multielement airfoils were performed by the presented method with Spalart-Allmaras one equation turbulence model incorporated in it.
Muller, M; Verhagen, J H
1988-10-21
1. A mathematical treatment of the flow inside the vertebrate labyrinth is given. The main difference to former theories (e.g. the "torsion pendulum" theory) is that the entire system formed by the three semicircular ducts, interconnected by the crus commune and the utriculus, is considered, instead of a single duct circuit. 2. The theory consists of a geometrical description of a labyrinth rotating in space, the solution of the continuity equation, determination of the initial velocities in all the ducts in a "cupulometry" experiment and derivation of the equation of motion (e.o.m.). 3. Equations for a system consisting of two ducts and for the classical single-duct system are special cases of the three-duct system. 4. Three different methods for the solution of the e.o.m. are described: an analytical one, a Runge-Kutta simulation and an "asymptotic" method. The last method includes approximations of the solution of the e.o.m. on a long and a short time scale. Its advantage is that it gives an insight based on rather manageable formulae. 5. The physiological basis of the presented theory, biological applications and verification are given in a separate paper (Muller & Verhagen, 1988). PMID:3255008
Development of a novel flow cytometric approach to evaluate fish sperm chromatin using fixed samples
Jenkins, Jill A.
2013-01-01
The integrity of the paternal DNA is essential for the accurate transmission of genetic information, yet fertilization is not inhibited by chromatin breakage. Some methods are available for the sensitive detection of DNA damage and can be applied in studies of environmental toxicology, carcinogenesis, aging, and assisted reproduction techniques in both clinical and experimental settings. Because semen samples obtained from remote locations undergo chromatin damage prior to laboratory assessment, the present study was undertaken to evaluate treatments for effective chromatin staining in the development of a DNA fragmentation assay using fixed milt from yellow perch (Perca flavescens). Similar to the sperm chromatin structure assay (SCSA), susceptibility of nuclear DNA to acid-induced denaturation was measured by flow cytometry (FCM). Use of 10% buffered formalin for milt fixation allowed easier peak discrimination than 4% paraformaldehyde. The effects of time and temperature of incubation in 0.08 N HCl were evaluated in order to determine the ideal conditions for promoting DNA decondensation and making strand breaks more available for staining and detection by FCM. The best results were obtained with incubation at 37°C for 1 minute, followed by cold propidium iodide staining for 30 minutes.
Dixon, Kenneth L; Lee, Patricia L; Flach, Gregory P
2008-05-01
A graded approach to flow and transport modeling has been used as a cost effective solution to evaluating potential groundwater risk in support of Deactivation and Decommissioning activities at the United States Department of Energy's Savannah River Site (SRS) in Aiken, South Carolina. This approach balances modeling complexity with potential risk and has been successfully used at SRS to reduce costs and accelerate schedule without compromising human health or the environment. The approach incorporates both simple spreadsheet calculations (i.e., screening models) and complex numerical modeling to evaluate the threat to human health posed by contaminants leaching from decommissioned concrete building slabs. Simple spreadsheet calculations were used to produce generic slab concentration limits for a suite of radiological and non-radiological contaminants for a chemical separations area at SRS. These limits, which are based upon the United States Environmental Protection Agency Soil Screening Guidance, were used to eliminate most building slabs from further risk assessment, thereby limiting the time and associated cost of the more rigorous assessment to higher risk facilities. Of the more than 58 facilities located in the area, to date only one slab has been found to have a contaminant concentration in excess of the area specific slab limit. For this slab, a more rigorous numerical modeling effort was undertaken which eliminated some of the simplifying and conservative assumptions inherent in the spreadsheet calculations. Results from the more sophisticated numerical model show that the remaining contaminant of concern would not likely impact groundwater above drinking water standards. PMID:18403957
NASA Astrophysics Data System (ADS)
Park, D. K.; Bae, G. O.; Joun, W.; Park, B. H.; Park, J.; Park, I.; Lee, K. K.
2015-12-01
The GWHP system uses a stable temperature of groundwater for cooling and heating in buildings and thus has been known as one of the most energy-saving and cost-efficient renewable energy techniques. A GWHP facility was installed at an island located at the confluence of North Han and South Han rivers, Korea. Because of well-developed alluvium, the aquifer is suitable for application of this system, extracting and injecting a large amount of groundwater. However, the numerical experiments under various operational conditions showed that it could be vulnerable to thermal interference due to the highly permeable gravel layer, as a preferential path of thermal plume migration, and limited space for well installation. Thus, regional groundwater flow must be an important factor of consideration for the efficient operation under these conditions but was found to be not simple in this site. While the groundwater level in this site totally depends on the river stage control of Paldang dam, the direction and velocity of the regional groundwater flow, observed using the colloidal borescope, have been changed hour by hour with the combined flows of both the rivers. During the pumping and injection tests, the water discharges in Cheongpyeong dam affected their respective results. Moreover, the measured NO3-N concentrations might imply the effect of agricultural activities around the facility on the groundwater quality along the regional flow. It is obvious that the extraction and injection of groundwater during the facility operation will affect the fate of the agricultural contaminants. Particularly, the gravel layer must also be a main path for contaminant migration. The simulations for contaminant transport during the facility operation showed that the operation strategy for only thermal efficiency could be unsafe and unstable in respect of groundwater quality. All these results concluded that the integrated approach on groundwater flow and heat/solute transport is necessary
Shiddiky, Muhammad J. A.; Vaidyanathan, Ramanathan; Rauf, Sakandar; Tay, Zhikai; Trau, Matt
2014-01-01
Early diagnosis of disease requires highly specific measurement of molecular biomarkers from femto to pico-molar concentrations in complex biological (e.g., serum, blood, etc.) samples to provide clinically useful information. While reaching this detection limit is challenging in itself, these samples contain numerous other non-target molecules, most of which have a tendency to adhere to solid surfaces via nonspecific interactions. Herein, we present an entirely new methodology to physically displace nonspecifically bound molecules from solid surfaces by utilizing a newly discovered “tuneable force”, induced by an applied alternating electric field, which occurs within few nanometers of an electrode surface. This methodology thus offers a unique ability to shear-off loosely bound molecules from the solid/liquid interface. Via this approach, we achieved a 5-fold reduction in nonspecific adsorption of non-target protein molecules and a 1000-fold enhancement for the specific capture of HER2 protein in human serum. PMID:24430114
Shiddiky, Muhammad J A; Vaidyanathan, Ramanathan; Rauf, Sakandar; Tay, Zhikai; Trau, Matt
2014-01-01
Early diagnosis of disease requires highly specific measurement of molecular biomarkers from femto to pico-molar concentrations in complex biological (e.g., serum, blood, etc.) samples to provide clinically useful information. While reaching this detection limit is challenging in itself, these samples contain numerous other non-target molecules, most of which have a tendency to adhere to solid surfaces via nonspecific interactions. Herein, we present an entirely new methodology to physically displace nonspecifically bound molecules from solid surfaces by utilizing a newly discovered "tuneable force", induced by an applied alternating electric field, which occurs within few nanometers of an electrode surface. This methodology thus offers a unique ability to shear-off loosely bound molecules from the solid/liquid interface. Via this approach, we achieved a 5-fold reduction in nonspecific adsorption of non-target protein molecules and a 1000-fold enhancement for the specific capture of HER2 protein in human serum. PMID:24430114
NASA Astrophysics Data System (ADS)
Shiddiky, Muhammad J. A.; Vaidyanathan, Ramanathan; Rauf, Sakandar; Tay, Zhikai; Trau, Matt
2014-01-01
Early diagnosis of disease requires highly specific measurement of molecular biomarkers from femto to pico-molar concentrations in complex biological (e.g., serum, blood, etc.) samples to provide clinically useful information. While reaching this detection limit is challenging in itself, these samples contain numerous other non-target molecules, most of which have a tendency to adhere to solid surfaces via nonspecific interactions. Herein, we present an entirely new methodology to physically displace nonspecifically bound molecules from solid surfaces by utilizing a newly discovered ``tuneable force'', induced by an applied alternating electric field, which occurs within few nanometers of an electrode surface. This methodology thus offers a unique ability to shear-off loosely bound molecules from the solid/liquid interface. Via this approach, we achieved a 5-fold reduction in nonspecific adsorption of non-target protein molecules and a 1000-fold enhancement for the specific capture of HER2 protein in human serum.
Time-Dependent Simulation of Incompressible Flow in a Turbopump Using Overset Grid Approach
NASA Technical Reports Server (NTRS)
Kiris, Cetin; Kwak, Dochan
2001-01-01
This paper reports the progress being made towards complete unsteady turbopump simulation capability by using overset grid systems. A computational model of a turbo-pump impeller is used as a test case for the performance evaluation of the MPI, hybrid MPI/Open-MP, and MLP versions of the INS3D code. Relative motion of the grid system for rotor-stator interaction was obtained by employing overset grid techniques. Unsteady computations for a turbo-pump, which contains 114 zones with 34.3 Million grid points, are performed on Origin 2000 systems at NASA Ames Research Center. The approach taken for these simulations, and the performance of the parallel versions of the code are presented.
A thermodynamic approach to link self-organization, preferential flow and rainfall-runoff behaviour
NASA Astrophysics Data System (ADS)
Zehe, E.; Ehret, U.; Blume, T.; Kleidon, A.; Scherer, U.; Westhoff, M.
2013-11-01
This study investigates whether a thermodynamically optimal hillslope structure can, if existent, serve as a first guess for uncalibrated predictions of rainfall-runoff. To this end we propose a thermodynamic framework to link rainfall-runoff processes and dynamics of potential energy, kinetic energy and capillary binding energy in catchments and hillslopes. The starting point is that hydraulic equilibrium in soil corresponds to local thermodynamic equilibrium (LTE), characterized by a local maximum entropy/minimum of free energy of soil water. Deviations from LTE occur either due to evaporative losses, which increase absolute values of negative capillary binding energy of soil water and reduce its potential energy, or due to infiltration of rainfall, which increases potential energy of soil water and reduces the strength of capillary binding energy. The amplitude and relaxation time of these deviations depend on climate, vegetation, soil hydraulic functions, topography and density of macropores. Based on this framework we analysed the free energy balance of hillslopes within numerical experiments that perturbed model structures with respect to the surface density of macropores. These model structures have been previously shown to allow successful long-term simulations of the water balances of the Weiherbach and the Malalcahuello catchments, which are located in distinctly different pedological and climatic settings. Our findings offer a new perspective on different functions of preferential flow paths depending on the pedological setting. Free energy dynamics of soil water in the cohesive soils of the Weiherbach is dominated by dynamics of capillary binding energy. Macropores act as dissipative wetting structures by enlarging water flows against steep gradients in soil water potential after long dry spells. This implies accelerated depletion of these gradients and faster relaxation back towards LTE. We found two local optima in macropore density that maximize
Taylor, Caz M; Laughlin, Andrew J; Hall, Richard J
2016-05-01
Declines in migratory species have been linked to anthropogenic climate change through phenological mismatch, which arises due to asynchronies between the timing of life-history events (such as migration) and the phenology of available resources. Long-distance migratory species may be particularly vulnerable to phenological change in their breeding ranges, since the timing of migration departure is based on environmental cues at distant non-breeding sites. Migrants may, however, be able to adjust migration speed en route to the breeding grounds, and thus, ability of migrants to update their timing of migration may depend critically on stopover frequency during migration; however, understanding how migratory strategy influences population dynamics is hindered by a lack of predictive models explicitly linking habitat quality to demography and movement patterns throughout the migratory cycle. Here, we present a novel modelling framework, the Migratory Flow Network (MFN), in which the seasonally varying attractiveness of breeding, winter and stopover regions drives the direction and timing of migration based on a simple general flux law. We use the MFN to investigate how populations respond to shifts in breeding site phenology based on their frequency of stopover and ability to detect and adapt to these changes. With perfect knowledge of advancing phenology, 'jump' migrants (low-frequency stopover) require more adaptation for populations to recover than 'hop' and 'skip' (high or medium frequency stopover) migrants. If adaptation depends on proximity, hop and skip migrants' populations can recover but jump migrants cannot adjust and decline severely. These results highlight the importance of understanding migratory strategies and maintaining high-quality stopover habitat to buffer migratory populations from climate-induced mismatch. We discuss how MFNs could be applied to diverse migratory taxa and highlight the potential of MFNs as a tool for exploring how migrants
NASA Astrophysics Data System (ADS)
Kemner, K. M.; Boyanov, M.; Flynn, T. M.; O'Loughlin, E. J.; Antonopoulos, D. A.; Kelly, S.; Skinner, K.; Mishra, B.; Brooks, S. C.; Watson, D. B.; Wu, W. M.
2015-12-01
FeIII- and SO42--reducing microorganisms and the mineral phases they produce have profound implications for many processes in aquatic and terrestrial systems. In addition, many of these microbially-catalysed geochemical transformations are highly dependent upon introduction of reactants via advective and diffusive hydrological transport. We have characterized microbial communities from a set of static microcosms to test the effect of ethanol diffusion and sulfate concentration on UVI-contaminated sediment. The spatial distribution, valence states, and speciation of both U and Fe were monitored in situ throughout the experiment by synchrotron x-ray absorption spectroscopy, in parallel with solution measurements of pH and the concentrations of sulfate, ethanol, and organic acids. After reaction initiation, a ~1-cm thick layer of sediment near the sediment-water (S-W) interface became visibly dark. Fe XANES spectra of the layer were consistent with the formation of FeS. Over the 4 year duration of the experiment, U LIII-edge XANES indicated reduction of U, first in the dark layer and then throughout the sediment. Next, the microcosms were disassembled and samples were taken from the overlying water and different sediment regions. We extracted DNA and characterized the microbial community by sequencing 16S rRNA gene amplicons with the Illumina MiSeq platform and found that the community evolved from its originally homogeneous composition, becoming significantly spatially heterogeneous. We have also developed an x-ray accessible column to probe elemental transformations as they occur along the flow path in a porous medium with the purpose of refining reactive transport models (RTMs) that describe coupled physical and biogeochemical processes in environmental systems. The elemental distribution dynamics and the RTMs of the redox driven processes within them will be presented.
Tracing carbon flow through coral reef food webs using a compound-specific stable isotope approach.
McMahon, Kelton W; Thorrold, Simon R; Houghton, Leah A; Berumen, Michael L
2016-03-01
Coral reefs support spectacularly productive and diverse communities in tropical and sub-tropical waters throughout the world's oceans. Debate continues, however, on the degree to which reef biomass is supported by new water column production, benthic primary production, and recycled detrital carbon (C). We coupled compound-specific stable C isotope ratio (δ(13)C) analyses with Bayesian mixing models to quantify C flow from primary producers to coral reef fishes across multiple feeding guilds and trophic positions in the Red Sea. Analyses of reef fishes with putative diets composed primarily of zooplankton (Amblyglyphidodon indicus), benthic macroalgae (Stegastes nigricans), reef-associated detritus (Ctenochaetus striatus), and coral tissue (Chaetodon trifascialis) confirmed that δ(13)C values of essential amino acids from all baseline C sources were both isotopically diagnostic and accurately recorded in consumer tissues. While all four source end-members contributed to the production of coral reef fishes in our study, a single-source end-member often dominated dietary C assimilation of a given species, even for highly mobile, generalist top predators. Microbially reworked detritus was an important secondary C source for most species. Seascape configuration played an important role in structuring resource utilization patterns. For instance, Lutjanus ehrenbergii showed a significant shift from a benthic macroalgal food web on shelf reefs (71 ± 13 % of dietary C) to a phytoplankton-based food web (72 ± 11 %) on oceanic reefs. Our work provides insights into the roles that diverse C sources play in the structure and function of coral reef ecosystems and illustrates a powerful fingerprinting method to develop and test nutritional frameworks for understanding resource utilization. PMID:26590916
Beloglazova, N V; Shmelin, P S; Eremin, S A
2016-03-01
Three kinds of immunoassays for the determination of gentamicin in milk samples were developed and validated. First, a fast and easily-performed fluorescence polarization immunoassay was used for characterization of the employed polyclonal antibody. The calculated Kaff were (1.9±0.4)×10(9)М(-1) and (6.0±0.2)×10(6)М(-1) for the high- and low-affinity fractions respectively. The assay was characterized with a good sensitivity, the limit of detection being 5μgkg(-1). Two different kinds of detection labels, i.e. colloidal gold (CG) and quantum dots (QDs), were evaluated for use in lateral-flow format with respect to rapid visual on-site testing. The cut-off levels for both qualitative formats were selected based on the maximum level for gentamicin in milk established by the European Commission, 100μgkg(-1), resulting in a 10μgkg(-1) cut-off considering sample dilution. The intra-laboratory validation was performed with sterilized milk samples artificially spiked with gentamicin at concentrations less than, equal to, and greater than the cut-off level. It was shown that milk products could be analyzed without any sample preparation, except for dilution with the buffer solution. The rates of false-positive and false-negative results were below 5% for both labels. The different developed immunoassays were tested towards gentamicin determination in artificially-spiked and naturally contaminated milk samples. PMID:26717834
NASA Technical Reports Server (NTRS)
Sheng, Chunhua; Hyams, Daniel G.; Sreenivas, Kidambi; Gaither, J. Adam; Marcum, David L.; Whitfield, David L.
2000-01-01
A multiblock unstructured grid approach is presented for solving three-dimensional incompressible inviscid and viscous turbulent flows about complete configurations. The artificial compressibility form of the governing equations is solved by a node-based, finite volume implicit scheme which uses a backward Euler time discretization. Point Gauss-Seidel relaxations are used to solve the linear system of equations at each time step. This work employs a multiblock strategy to the solution procedure, which greatly improves the efficiency of the algorithm by significantly reducing the memory requirements by a factor of 5 over the single-grid algorithm while maintaining a similar convergence behavior. The numerical accuracy of solutions is assessed by comparing with the experimental data for a submarine with stem appendages and a high-lift configuration.
NASA Astrophysics Data System (ADS)
Brieva, Jorge; Moya-Albor, Ernesto; Escalante-Ramírez, Boris
2015-01-01
The left ventricle (LV) segmentation plays an important role in a subsequent process for the functional analysis of the LV. Typical segmentation of the endocardium wall in the ventricle excludes papillary muscles which leads to an incorrect measure of the ejected volume in the LV. In this paper we present a new variational strategy using a 2D level set framework that includes a local term for enhancing the low contrast structures and a 2D shape model. The shape model in the level set method is propagated to all image sequences corresponding to the cardiac cycles through the optical flow approach using the Hermite transform. To evaluate our strategy we use the Dice index and the Hausdorff distance to compare the segmentation results with the manual segmentation carried out by the physician.
New Approach to Study the Ignition Processes of Organic Coal-Water Fuels in an Oxidizer Flow
NASA Astrophysics Data System (ADS)
Valiullin, T. R.; Dmitrienko, M. A.; Strizhak, P. A.
2016-02-01
To converge the conditions of organic water-coal fuel composition combustion in the typical power equipment we developed a new approach and installed an experimental setup, eliminating the traditional fixing the fuel droplets on the thermocouples or rods. Specialized cone-shaped chamber was used to implement the process of lingering of organic water-coal fuel droplets. Necessary and sufficient conditions for the lingering of organic water-coal fuel droplets were established. We determined the parameters of the system (droplet size of 0.4-0.6 mm, temperatures 823-903 K and the velocity of the oxidizer flow 1.5-6 m/s) at which the droplets were consistently ignited in the process of lingering. Minimum temperatures and ignition delay times of organic water-coal fuel droplets based on brown coal, used motor, turbine, transformer oils, kerosene, gasoline and water were defined.
González-Rodríguez, J; Pérez-Juan, P; Luque de Castro, M D
2002-01-01
A simultaneous and fast method for the determination of total polyphenol index (t.p.i.) and total anthocyan index (t.a.i.) has been developed by a flow injection approach and a diode array spectrophotometer for monitoring at 280 and 520 nm, respectively. Linear ranges were obtained from 20 to 70 index units and from 20 to 500 mg l(-1) for the t.p.i. and t.a.i., respectively. The results provided by the proposed method agree with those obtained using the polyphenol index at 280 nm and the Ribereau-Gayon method for the determination of total anthocyans. The sample throughout was 25-30 samples per hour. Analytical features such as repeatability, reproducibility and detection and quantification limits as well as the results of a robustness study based on the Steiner-Younden procedure are also given. PMID:18968479
Gallis, Michail A.; Bond, Ryan Bomar; Torczynski, John Robert
2010-06-01
A recently proposed approach for the Direct Simulation Monte Carlo (DSMC) method to calculate chemical-reaction rates is assessed for high-temperature atmospheric species. The new DSMC model reproduces measured equilibrium reaction rates without using any macroscopic reaction-rate information. Since it uses only molecular properties, the new model is inherently able to predict reaction rates for arbitrary non-equilibrium conditions. DSMC non-equilibrium reaction rates are compared to Park's phenomenological nonequilibrium reaction-rate model, the predominant model for hypersonic-flow-field calculations. For near-equilibrium conditions, Park's model is in good agreement with the DSMC-calculated reaction rates. For far-from-equilibrium conditions, corresponding to a typical shock layer, significant differences can be found. The DSMC predictions are also found to be in very good agreement with measured and calculated non-equilibrium reaction rates, offering strong evidence that this is a viable and reliable technique to predict chemical reaction rates.
Hu, Kun; Lo, Men-Tzung; Peng, Chung-Kang; Liu, Yanhui; Novak, Vera
2012-01-01
Cerebral autoregulation (CA) is an important vascular control mechanism responsible for relatively stable cerebral blood flow despite changes of systemic blood pressure (BP). Impaired CA may leave brain tissue unprotected against potentially harmful effects of BP fluctuations. It is generally accepted that CA is less effective or even inactive at frequencies >∼0.1 Hz. Without any physiological foundation, this concept is based on studies that quantified the coupling between BP and cerebral blood flow velocity (BFV) using transfer function analysis. This traditional analysis assumes stationary oscillations with constant amplitude and period, and may be unreliable or even invalid for analysis of nonstationary BP and BFV signals. In this study we propose a novel computational tool for CA assessment that is based on nonlinear dynamic theory without the assumption of stationary signals. Using this method, we studied BP and BFV recordings collected from 39 patients with chronic ischemic infarctions and 40 age-matched non-stroke subjects during baseline resting conditions. The active CA function in non-stroke subjects was associated with an advanced phase in BFV oscillations compared to BP oscillations at frequencies from ∼0.02 to 0.38 Hz. The phase shift was reduced in stroke patients even at > = 6 months after stroke, and the reduction was consistent at all tested frequencies and in both stroke and non-stroke hemispheres. These results provide strong evidence that CA may be active in a much wider frequency region than previously believed and that the altered multiscale CA in different vascular territories following stroke may have important clinical implications for post-stroke recovery. Moreover, the stroke effects on multiscale cerebral blood flow regulation could not be detected by transfer function analysis, suggesting that nonlinear approaches without the assumption of stationarity are more sensitive for the assessment of the coupling of nonstationary
Srinivasan, V.; Vafai, K.; Christensen, R.N. )
1994-08-01
An innovative approach was opted for modeling the flow and heat transfer through spirally fluted tubes. The model divided the flow domain into two regions. The flutes were modeled as a porous substrate with direction-dependent permeabilities. This enabled modeling the swirl component in the fluted tube. The properties of the porous substrate such as its thickness, porosity, and ratio of the direction-dependent permeabilities were obtained from the geometry of the fluted tube. Experimental data on laminar Nusselt numbers and friction factors for different types of fluted tubes representing a broad range of flute geometry were available. Experimental data from a few of the tubes tested were used to propose a relationship between the permeability of the porous substrate and the flute parameters, particularly the flute spacing. The governing equations were discretized using the Finite Element Method. The model was verified and applied to the other tubes in the test matrix. Very good agreement was found between the numerical predictions and the experimental data. 20 refs., 13 figs., 4 tabs.
Micro reactor integrated μ-PEM fuel cell system: a feed connector and flow field free approach
NASA Astrophysics Data System (ADS)
Balakrishnan, A.; Mueller, C.; Reinecke, H.
2013-12-01
A system level microreactor concept for hydrogen generation with Sodium Borohydride (NaBH4) is demonstrated. The uniqueness of the system is the transport and distribution feature of fuel (hydrogen) to the anode of the fuel cell without any external feed connectors and flow fields. The approach here is to use palladium film instead of feed connectors and the flow fields; palladium's property to adsorb and desorb the hydrogen at ambient and elevated condition. The proof of concept is demonstrated with a polymethyl methacrylate (PMMA) based complete system integration which includes microreactor, palladium transport layer and the self-breathing polymer electrolyte membrane (PEM) fuel cell. The hydrolysis of NaBH4 was carried out in the presence of platinum supported by nickel (NiPt). The prototype functionality is tested with NaBH4 chemical hydride. The characterization of the integrated palladium layer and fuel cell is tested with constant and switching load. The presented integrated fuel cell is observed to have a maximum power output and current of 60 mW and 280 mA respectively.
NASA Astrophysics Data System (ADS)
Chou, F. N.-F.; Wu, C.-W.
2014-05-01
This paper presents a method to establish the objective function of a network flow programming model for simulating river-reservoir system operations and associated water allocation, with an emphasis on situations when the links other than demand or storage have to be assigned with nonzero cost coefficients. The method preserves the priorities defined by rule curves of reservoir, operational preferences for conveying water, allocation of storage among multiple reservoirs, and transbasin water diversions. Path enumeration analysis transforms these water allocation rules into linear constraints that can be solved to determine link cost coefficients. An approach to prune the original system into a reduced network is proposed to establish the precise constraints of nonzero cost coefficients, which can then be efficiently solved. The cost coefficients for the water allocation in the Feitsui and Shihmen reservoirs' joint operating system of northern Taiwan was adequately assigned by the proposed method. This case study demonstrates how practitioners can correctly utilize network-flow-based models to allocate water supply throughout complex systems that are subject to strict operating rules.
NASA Astrophysics Data System (ADS)
Chou, F. N.-F.; Wu, C.-W.
2013-12-01
This paper presents a method to establish the objective function of a network flow programming model for simulating river/reservoir system operations and associated water allocation, with an emphasis on situations when the links other than demand or storage have to be assigned with nonzero cost coefficients. The method preserves the priorities defined by rule curves of reservoir, operational preferences for conveying water, allocation of storage among multiple reservoirs, and trans-basin water diversions. Path enumeration analysis transforms these water allocation rules into linear constraints that can be solved to determine link cost coefficients. An approach to prune the original system into a reduced network is proposed to establish the precise constraints of nonzero cost coefficients which can then be efficiently solved. The cost coefficients for the water allocation in the Feitsui and Shihmen Reservoirs joint operating system of northern Taiwan was adequately assigned by the proposed method. This case study demonstrates how practitioners can correctly utilize network-flow-based models to allocate water supply throughout complex systems that are subject to strict operating rules.
Sladitschek, Hanna L; Neveu, Pierre A
2015-01-01
The continuous improvement of imaging technologies has driven the development of sophisticated reporters to monitor biological processes. Such constructs should ideally be assembled in a flexible enough way to allow for their optimization. Here we describe a highly reliable cloning method to efficiently assemble constructs for imaging or flow cytometry applications in mammalian cell culture systems. We bioinformatically identified a list of restriction enzymes whose sites are rarely found in human and mouse cDNA libraries. From the best candidates, we chose an enzyme combination (MluI, XhoI and SalI: MXS) that enables iterative chaining of individual building blocks. The ligation scar resulting from the compatible XhoI- and SalI-sticky ends can be translated and hence enables easy in-frame cloning of coding sequences. The robustness of the MXS-chaining approach was validated by assembling constructs up to 20 kb long and comprising up to 34 individual building blocks. By assessing the success rate of 400 ligation reactions, we determined cloning efficiency to be 90% on average. Large polycistronic constructs for single-cell imaging or flow cytometry applications were generated to demonstrate the versatility of the MXS-chaining approach. We devised several constructs that fluorescently label subcellular structures, an adapted version of FUCCI (fluorescent, ubiquitination-based cell cycle indicator) optimized to visualize cell cycle progression in mouse embryonic stem cells and an array of artificial promoters enabling dosage of doxycyline-inducible transgene expression. We made publicly available through the Addgene repository a comprehensive set of MXS-building blocks comprising custom vectors, a set of fluorescent proteins, constitutive promoters, polyadenylation signals, selection cassettes and tools for inducible gene expression. Finally, detailed guidelines describe how to chain together prebuilt MXS-building blocks and how to generate new customized MXS
Moya, Claudio E; Raiber, Matthias; Taulis, Mauricio; Cox, Malcolm E
2015-03-01
The Galilee and Eromanga basins are sub-basins of the Great Artesian Basin (GAB). In this study, a multivariate statistical approach (hierarchical cluster analysis, principal component analysis and factor analysis) is carried out to identify hydrochemical patterns and assess the processes that control hydrochemical evolution within key aquifers of the GAB in these basins. The results of the hydrochemical assessment are integrated into a 3D geological model (previously developed) to support the analysis of spatial patterns of hydrochemistry, and to identify the hydrochemical and hydrological processes that control hydrochemical variability. In this area of the GAB, the hydrochemical evolution of groundwater is dominated by evapotranspiration near the recharge area resulting in a dominance of the Na-Cl water types. This is shown conceptually using two selected cross-sections which represent discrete groundwater flow paths from the recharge areas to the deeper parts of the basins. With increasing distance from the recharge area, a shift towards a dominance of carbonate (e.g. Na-HCO3 water type) has been observed. The assessment of hydrochemical changes along groundwater flow paths highlights how aquifers are separated in some areas, and how mixing between groundwater from different aquifers occurs elsewhere controlled by geological structures, including between GAB aquifers and coal bearing strata of the Galilee Basin. The results of this study suggest that distinct hydrochemical differences can be observed within the previously defined Early Cretaceous-Jurassic aquifer sequence of the GAB. A revision of the two previously recognised hydrochemical sequences is being proposed, resulting in three hydrochemical sequences based on systematic differences in hydrochemistry, salinity and dominant hydrochemical processes. The integrated approach presented in this study which combines different complementary multivariate statistical techniques with a detailed assessment of the
A computer vision approach to rare cell in vivo fluorescence flow cytometry
Markovic, Stacey; Li, Binlong; Pera, Vivian; Sznaier, Mario; Camps, Octavia; Niedre, Mark
2014-01-01
Non-invasive enumeration of rare circulating cell populations in small animals is of great importance in many areas of biomedical research. In this work we describe a macroscopic fluorescence imaging system and automated computer vision algorithm that allows in vivo detection, enumeration and tracking of circulating fluorescently-labeled cells from multiple large blood vessels in the ear of a mouse. This imaging system uses a 660 nm laser and a high sensitivity electron-multiplied charge coupled device camera (EMCCD) to acquire fluorescence image sequences from relatively large (~5 × 5 mm2) imaging areas. The primary technical challenge was developing an automated method for identifying and tracking rare cell events in image sequences with substantial autofluorescence and noise content. To achieve this, we developed a two-step image analysis algorithm that first identified cell candidates in individual frames, and then merged cell candidates into tracks by dynamic analysis of image sequences. The second step was critical since it allowed rejection of >97% of false positive cell counts. Overall, our computer vision IVFC (CV-IVFC) approach allows single-cell detection sensitivity at estimated concentrations of 20 cells per mL of peripheral blood. In addition to simple enumeration, the technique recovers the cell’s trajectory, which in the future could be used to automatically identify, for example, in vivo homing and docking events. PMID:24273157
Simulations of singularity dynamics in liquid crystal flows: A C finite element approach
Lin Ping . E-mail: matlinp@nus.edu.sg; Liu Chun . E-mail: liu@math.psu.edu
2006-06-10
In this paper, we present a C finite element method for a 2a hydrodynamic liquid crystal model which is simpler than existing C {sup 1} element methods and mixed element formulation. The energy law is formally justified and the energy decay is used as a validation tool for our numerical computation. A splitting method combined with only a few fixed point iteration for the penalty term of the director field is applied to reduce the size of the stiffness matrix and to keep the stiffness matrix time-independent. The latter avoids solving a linear system at every time step and largely reduces the computational time, especially when direct linear system solvers are used. Our approach is verified by comparing its computational results with those obtained by C {sup 1} elements and by mixed formulation. Through numerical experiments of a few other splittings and explicit-implicit strategies, we recommend a fast and reliable algorithm for this model. A number of examples are computed to demonstrate the algorithm.
A New Approach to Sap Flow Measurement Using 3D Printed Gauges and Open-source Electronics
NASA Astrophysics Data System (ADS)
Ham, J. M.; Miner, G. L.; Kluitenberg, G. J.
2015-12-01
A new type of sap flow gauge was developed to measure transpiration from herbaceous plants using a modified heat pulse technique. Gauges were fabricated using 3D-printing technology and low-cost electronics to keep the materials cost under $20 (U.S.) per sensor. Each gauge consisted of small-diameter needle probes fastened to a 3D-printed frame. One needle contained a resistance heater to provide a 6 to 8 second heat pulse while the other probes measured the resultant temperature increase at two distances from the heat source. The data acquisition system for the gauges was built from a low-cost Arduino microcontroller. The system read the gauges every 10 minutes and stored the results on a SD card. Different numerical techniques were evaluated for estimating sap velocity from the heat pulse data - including analytical solutions and parameter estimation approaches . Prototype gauges were tested in the greenhouse on containerized corn and sunflower. Sap velocities measured by the gauges were compared to independent gravimetric measurements of whole plant transpiration. Results showed the system could measure daily transpiration to within 3% of the gravimetric measurements. Excellent agreement was observed when two gauges were attached the same stem. Accuracy was not affected by rapidly changing transpiration rates observed under partly cloudy conditions. The gauge-based estimates of stem thermal properties suggested the system may also detect the onset of water stress. A field study showed the gauges could run for 1 to 2 weeks on a small battery pack. Sap flow measurements on multiple corn stems were scaled up by population to estimate field-scale transpiration. During full canopy cover, excellent agreement was observed between the scaled-up sap flow measurements and reference crop evapotranspiration calculated from weather data. Data also showed promise as a way to estimate real-time canopy resistance required for model verification and development. Given the low
NASA Astrophysics Data System (ADS)
Pasquariello, Vito; Hammerl, Georg; Örley, Felix; Hickel, Stefan; Danowski, Caroline; Popp, Alexander; Wall, Wolfgang A.; Adams, Nikolaus A.
2016-02-01
We present a loosely coupled approach for the solution of fluid-structure interaction problems between a compressible flow and a deformable structure. The method is based on staggered Dirichlet-Neumann partitioning. The interface motion in the Eulerian frame is accounted for by a conservative cut-cell Immersed Boundary method. The present approach enables sub-cell resolution by considering individual cut-elements within a single fluid cell, which guarantees an accurate representation of the time-varying solid interface. The cut-cell procedure inevitably leads to non-matching interfaces, demanding for a special treatment. A Mortar method is chosen in order to obtain a conservative and consistent load transfer. We validate our method by investigating two-dimensional test cases comprising a shock-loaded rigid cylinder and a deformable panel. Moreover, the aeroelastic instability of a thin plate structure is studied with a focus on the prediction of flutter onset. Finally, we propose a three-dimensional fluid-structure interaction test case of a flexible inflated thin shell interacting with a shock wave involving large and complex structural deformations.
NASA Astrophysics Data System (ADS)
Mohaghegh, Fazlolah; Udaykumar, H. S.
2015-11-01
The aim of this study is to find a proper method for the simulation of blood as a particulate flow. Since the blood cell density is almost the same as plasma, the high added mass effect necessitates implementation of a strongly coupled FSI method in the numerical simulation. Therefore, three different FSI approaches are compared, two Smoothed Profile Methods (SPM) with one and two projection steps as diffuse interface approaches and the Sharp Interface Method (SIM). Stable FSI computations can be achieved by using sub-iterations within each time step, i.e. by updating the fluid and structure and their boundary conditions at each time step multiple times to reach a desired tolerance as the convergence criteria. Various cases were used to benchmark the methods, including particles motion in a channel and particles sedimentation. The results show that the number of sub-iterations plays a key role in the efficiency. While use of SPM with two projection steps has the most expensive sub-iteration process, it has the best efficiency as it requires the lowest number of sub-iterations within each time step. Moreover, the method is more stable than SIM and the SPM with one projection. SIM is faster than SPM with one projection and it has better stability. PhD Candidate-Department of Mechanical Engineering.
Campbell, Lesley G.; Lee, David; Shukla, Kruti; Waite, Thomas A.; Bartsch, Detlef
2016-01-01
Premise of the study: Agricultural practices routinely create opportunities for crops to hybridize with wild relatives, leading to crop gene introgression into wild genomes. Conservationists typically worry this introgression could lead to genetic homogenization of wild populations, over and above the central concern of transgene escape. Alternatively, viewing introgression as analogous to species invasion, we suggest that increased genetic diversity may likewise be an undesirable outcome. Methods: Here, we compare the sensitivity of conventional population genetic metrics with species diversity indices as indicators of the impact of gene flow on genetic diversity. We illustrate this novel approach using multilocus genotype data (12 allozyme loci) from 10 wild (Beta vulgaris subsp. maritima) and eight putative crop–wild hybrid beet populations (B. vulgaris subsp. vulgaris × B. vulgaris subsp. maritima) scattered throughout Europe. Results: Conventional population genetic metrics mostly failed to detect shifts in genetic composition of putative hybrid populations. By contrast, species diversity indices unambiguously revealed increased genetic diversity in putative hybrid populations. Discussion: We encourage other workers to explore the utility of our more sensitive approach for risk assessment prior to the release of transgenic crops, with a view toward widespread adoption of our method in studies aimed at detecting allelic invasion. PMID:27011898
Dixon, K; Patricia Lee, P; Gregory Flach, G
2007-06-07
A graded approach to flow and transport modeling has been used as a cost effective solution to evaluating potential groundwater risk in support of Deactivation and Decommissioning activities at the United States Department of Energy's Savannah River Site. This approach incorporates both simple spreadsheet calculations and complex numerical modeling to evaluate the threat to human health posed by contaminants leaching from decommissioned concrete building slabs. Simple spread sheet calculations were used to produce generic slab concentration limits for a suite of radiological and non-radiological contaminants for a chemical separations area at Savannah River Site. These limits, which are based upon the United States Environmental Protection Agency Soil Screening guidance, were used to eliminate most building slabs from further risk assessment. Of the more than 58 facilities located in the area, to date only one slab has been found to have a contaminant concentration in excess of the area specific slab limit. For this slab, a more rigorous numerical modeling effort was undertaken reducing the conservatisms inherent in the spreadsheet calculations. Using the more sophisticated numerical model, it was possible to show that the remaining contaminant of concern would not likely impact groundwater above drinking water standards.
Rajagopal, K.R.
1993-11-01
In the previous report the linearized stability results for the flow of granular materials down an inclined plane, modeled by a constitutive theory based on the kinetic theory approach were presented. In this report, the authors derive the governing equations for the flow of granular materials down an inclined plane, modeled by the constitutive theory proposed by Boyle and Massoudi (1990). The governing equations obtained will be solved numerically to obtain the basic solutions.
NASA Astrophysics Data System (ADS)
Cooper, Frances J.; van Soest, Matthijs C.; Hodges, Kip V.
2011-07-01
Simple numerical models suggest that many basaltic lava flows should sufficiently heat the sediments beneath them to reset (U-Th)/He systematics in detrital zircon and apatite. This result suggests a useful way to date such flows when more conventional geochronological approaches are either impractical or yield specious results. We present here a test of this method on sediments interstratified with basalt flows of the Taos Plateau Volcanic Field of New Mexico. Nineteen zircons and apatites from two samples of baked sand collected from the uppermost 2 cm of a fluvial channel beneath a flow of the Upper Member of the Servilleta Basalt yielded an apparent age of 3.487 ± 0.047 Ma (2 SE confidence level), within the range of all published 40Ar/39Ar dates for other flows in the Upper Member (2.81-3.72 Ma) and statistically indistinguishable from the 40Ar/39Ar dates for basal flows of the Upper Member with which the studied flow is broadly correlative (3.61 ± 0.13 Ma). Given the high yield of 4He from U and Th decay, this technique may be especially useful for dating Pleistocene basalt flows. Detailed studies of the variation of (U-Th)/He detrital mineral dates in sedimentary substrates, combined with thermal modeling, may be a valuable tool for physical volcanologists who wish to explore the temporal and spatial evolution of individual flows and lava fields.
NASA Astrophysics Data System (ADS)
Zhang, Xiaolei; Buta, Ronald J.
2015-01-01
Using the potential-density phase shift approach developed by the present authors in earlier publications, we estimate the magnitude of radial mass accretion/excretion rates across the disks of six nearby spiral galaxies (NGC 628, NGC 3351, NGC 3627, NGC 4321, NGC 4736, and NGC 5194) having a range of Hubble types. Our goal is to examine these rates in the context of bulge building and secular morphological evolution along the Hubble sequence. Stellar surface density maps of the sample galaxies are derived from SINGS 3.6 μm and SDSS i-band images using colors as an indicator of mass-to-light ratios. Corresponding molecular and atomic gas surface densities are derived from published CO (1-0) and HI interferometric observations of the BIMA SONG, THINGS, and VIVA surveys. The mass flow rate calculations utilize a volume-type torque integral to calculate the angular momentum exchange rate between the basic state disk matter and what we assume to be density wave modes in the observed galaxies. This volume-type integral contains the contributions from both the gravitational surface torque couple and the advective surface torque couple at the nonlinear, quasi-steady state of the wave modes, in sharp contrast to its behavior in the linear regime, where it contains only the contribution from the gravitational surface torque couple used by Lynden-Bell & Kalnajs in 1972. The potential-density phase shift approach yields angular momentum transport rates several times higher than those estimated using the Lynden-Bell and Kalnajs approach. And unlike Lynden-Bell and Kalnajs, whose approach predicts zero mass redistribution across the majority of the disk surface (apart from the isolated locations of wave-particle resonances) for quasi-steady waves, the current approach leads to predictions of significant mass redistribution induced by the quasi-steady density wave modes, enough for the morphological types of disks to evolve substantially within its lifetime. This difference
Paces, James B.; Nichols, Paul J.; Neymark, Leonid A.; Rajaram, Harihar
2013-01-01
Groundwater flow through fractured felsic tuffs and lavas at the Nevada National Security Site represents the most likely mechanism for transport of radionuclides away from underground nuclear tests at Pahute Mesa. To help evaluate fracture flow and matrix–water exchange, we have determined U-series isotopic compositions on more than 40 drill core samples from 5 boreholes that represent discrete fracture surfaces, breccia zones, and interiors of unfractured core. The U-series approach relies on the disruption of radioactive secular equilibrium between isotopes in the uranium-series decay chain due to preferential mobilization of 234U relative to 238U, and U relative to Th. Samples from discrete fractures were obtained by milling fracture surfaces containing thin secondary mineral coatings of clays, silica, Fe–Mn oxyhydroxides, and zeolite. Intact core interiors and breccia fragments were sampled in bulk. In addition, profiles of rock matrix extending 15 to 44 mm away from several fractures that show evidence of recent flow were analyzed to investigate the extent of fracture/matrix water exchange. Samples of rock matrix have 234U/238U and 230Th/238U activity ratios (AR) closest to radioactive secular equilibrium indicating only small amounts of groundwater penetrated unfractured matrix. Greater U mobility was observed in welded-tuff matrix with elevated porosity and in zeolitized bedded tuff. Samples of brecciated core were also in secular equilibrium implying a lack of long-range hydraulic connectivity in these cases. Samples of discrete fracture surfaces typically, but not always, were in radioactive disequilibrium. Many fractures had isotopic compositions plotting near the 230Th-234U 1:1 line indicating a steady-state balance between U input and removal along with radioactive decay. Numerical simulations of U-series isotope evolution indicate that 0.5 to 1 million years are required to reach steady-state compositions. Once attained, disequilibrium 234U/238U
Schwalm, Donelle; Epps, Clinton W; Rodhouse, Thomas J; Monahan, William B; Castillo, Jessica A; Ray, Chris; Jeffress, Mackenzie R
2016-04-01
Ecological niche theory holds that species distributions are shaped by a large and complex suite of interacting factors. Species distribution models (SDMs) are increasingly used to describe species' niches and predict the effects of future environmental change, including climate change. Currently, SDMs often fail to capture the complexity of species' niches, resulting in predictions that are generally limited to climate-occupancy interactions. Here, we explore the potential impact of climate change on the American pika using a replicated place-based approach that incorporates climate, gene flow, habitat configuration, and microhabitat complexity into SDMs. Using contemporary presence-absence data from occupancy surveys, genetic data to infer connectivity between habitat patches, and 21 environmental niche variables, we built separate SDMs for pika populations inhabiting eight US National Park Service units representing the habitat and climatic breadth of the species across the western United States. We then predicted occurrence probability under current (1981-2010) and three future time periods (out to 2100). Occurrence probabilities and the relative importance of predictor variables varied widely among study areas, revealing important local-scale differences in the realized niche of the American pika. This variation resulted in diverse and - in some cases - highly divergent future potential occupancy patterns for pikas, ranging from complete extirpation in some study areas to stable occupancy patterns in others. Habitat composition and connectivity, which are rarely incorporated in SDM projections, were influential in predicting pika occupancy in all study areas and frequently outranked climate variables. Our findings illustrate the importance of a place-based approach to species distribution modeling that includes fine-scale factors when assessing current and future climate impacts on species' distributions, especially when predictions are intended to manage and
Heitmuller, Franklin T; Raphelt, Nolan
2012-07-15
Instream-flow scientists embrace streamflow as the master variable driving aquatic and riparian ecosystems, and that natural flow variability is imperative for river conservation and restoration efforts. Sediment transport, which is critical for maintenance of physical habitats in rivers and floodplains, has received less direct attention from instream-flow practitioners. This article serves to highlight the roles of sediment-transport evaluations in modifying or verifying instream-flow prescriptions based on hydrology alone. Two examples of sediment-transport evaluations are discussed in relation to the Texas Senate Bill 3 Environmental Flows allocation process, a mandate to "develop environmental flow analyses and a recommended flow regime" that "maintain(s) the viability of the state's streams, rivers, and bay and estuary systems" using "reasonably available science". The first example provides an evaluation of effective discharge of suspended-sediment load of the lower Brazos River. The magnitude and frequency of effective discharge occurs between typical high-flow pulses and overbank flows, indicating that hydrologic and physical processes are not optimally coupled in some flow-regime models. The second example utilizes the Hydrology-Based Environmental Flow Regime (HEFR) model to prescribe instream flows for the lower Sabine River, and compares modeled bed-material loads for observed and HEFR-prescribed flow regimes. Results indicate that annual water and sediment yields are greatly reduced for the modeled flow regime. It should be noted, however, that different input variables to the HEFR model would have resulted in different computations of water and sediment yields, reinforcing that instream-flow practitioners should exercise great caution when applying rule-of-thumb procedures to generate flow prescriptions. PMID:22425877
Simulation of a Wall-Bounded Flow using a Hybrid LES/RAS Approach with Turbulence Recycling
NASA Technical Reports Server (NTRS)
Quinlan, Jesse R.; Mcdaniel, James; Baurle, Robert A.
2012-01-01
Simulations of a supersonic recessed-cavity flow are performed using a hybrid large-eddy/ Reynolds-averaged simulation approach utilizing an inflow turbulence recycling procedure and hybridized inviscid flux scheme. Calorically perfect air enters the three-dimensional domain at a free stream Mach number of 2.92. Simulations are performed to assess grid sensitivity of the solution, efficacy of the turbulence recycling, and effect of the shock sensor used with the hybridized inviscid flux scheme. Analysis of the turbulent boundary layer upstream of the rearward-facing step for each case indicates excellent agreement with theoretical predictions. Mean velocity and pressure results are compared to Reynolds-averaged simulations and experimental data for each case, and these comparisons indicate good agreement on the finest grid. Simulations are repeated on a coarsened grid, and results indicate strong grid density sensitivity. The effect of turbulence recycling on the solution is illustrated by performing coarse grid simulations with and without inflow turbulence recycling. Two shock sensors, one of Ducros and one of Larsson, are assessed for use with the hybridized inviscid flux reconstruction scheme.
Salvador, Carlos Eduardo M; Pieber, Bartholomäus; Neu, Philipp M; Torvisco, Ana; Kleber Z Andrade, Carlos; Kappe, C Oliver
2015-05-01
The development of a continuous flow multistep strategy for the synthesis of linear peptoids and their subsequent macrocyclization via Click chemistry is described. The central transformation of this process is an Ugi four-component reaction generating the peptidomimetic core structure. In order to avoid exposure to the often toxic and malodorous isocyanide building blocks, the continuous approach was telescoped by the dehydration of the corresponding formamide. In a concurrent operation, the highly energetic azide moiety required for the subsequent intramolecular copper-catalyzed azide-alkyne cycloaddition (Click reaction) was installed by nucleophilic substitution from a bromide precursor. All steps yielding to the linear core structures can be conveniently coupled without the need for purification steps resulting in a single process generating the desired peptidomimetics in good to excellent yields within a 25 min reaction time. The following macrocyclization was realized in a coil reactor made of copper without any additional additive. A careful process intensification study demonstrated that this transformation occurs quantitatively within 25 min at 140 °C. Depending on the resulting ring strain, either a dimeric or a monomeric form of the cyclic product was obtained. PMID:25842982
NASA Astrophysics Data System (ADS)
Valizadeh, Ziba; Shams, Mehrzad
2016-08-01
A numerical scheme for simulating the subcooled flow boiling of water and water-based nanofluids was developed. At first, subcooled flow boiling of water was simulated by the Eulerian multiphase scheme. Then the simulation results were compared with previous experimental data and a good agreement was observed. In the next step, subcooled flow boiling of water-based nanofluid was modeled. In the previous studies in this field, the nanofluid assumed as a homogeneous liquid and the two-phase scheme was used to simulate its boiling. In the present study, a new scheme was used to model the nanofluid boiling. In this scheme, to model the nanofluid flow boiling, three phases, water, vapor and nanoparticles were considered. The Eulerian-Eulerian approach was used for modeling water-vapor interphase and Eulerian-Lagrangian scheme was selected to observe water-nanoparticle interphase behavior. The results from the nanofluid boiling modeling were validated with an experimental investigation. The results of the present work and experimental data were consistent. The addition of 0.0935 % volume fraction of nanoparticles in pure liquid boiling flow increases the vapor volume fraction at the outlet almost by 40.7 %. The results show the three-phase model is a good approach to simulate the nanofluid boiling flow.
Ploskey, Gene R.; Johnson, Gary E.; Weiland, Mark A.; Khan, Fenton; Mueller, Robert P.; Serkowski, John A.; Rakowski, Cynthia L.; Hedgepeth, J.; Skalski, John R.; Ebberts, Blaine D.; Klatte, Bernard A.
2006-08-04
The objective of this study was to estimate and compare fate probabilities for juvenile salmon approaching two surface flow outlets (SFOs) to identify effective design characteristics. The SFOs differed principally in forebay location, depth, discharge, and water velocity over a sharp-crested weir. Both outlets were about 20 ft wide. The 22-ft deep Bonneville Powerhouse 2 Corner Collector (B2CC) was located in the southwest corner of the forebay and passed 5,000 ft3/s of water at normal-pool elevation. In contrast, The Dalles Dam ice and trash sluiceway outlet above Main Unit 1-3 (TDITC) was not located in a forebay corner, was only 7-ft deep, and discharged about 933 ft3/s at normal-pool elevation. The linear velocity of water over the weir was about 15 ft/s at the B2CC and 5 ft/s at the TDITC. We used a Dual-Frequency Identification Sonar (DIDSON) to record movements of fish within about 65 ft of the B2CC and within 35 ft of the TDITC. We actively tracked fish by manually adjusting pan and tilt rotator angles to keep targets in view. Contrary to expectations, active tracking did not provide a predominance of long tracks that clearly indicated fish fate because most tracks were incomplete. Active tracking did increase error in fish-position estimation, which complicated data processing, so we plan to sample multiple fixed zones in the future. The probability of fish entering each SFO was estimated by a Markov chain analysis, which did not require complete fish tracks. At the B2CC, we tracked 7,943 juvenile salmonids and most of them entered the B2CC. Fish moving south 40 to 60 ft upstream of the dam face were more likely to enter the eddy at the south end of the powerhouse than to enter the B2CC. At the TDITC, we tracked 2,821 smolts. Fish movement was complex with active swimming toward and away from the entrance. The high entrance probability zone (EPZ), where over 90% of tracked fish entered the SFO, extended 32 ft out at the B2CC and only 8 ft out at the TDITC
NASA Astrophysics Data System (ADS)
Benage, M. C.; Dufek, J.; Geist, D.; Harpp, K. S.
2011-12-01
simulations in concert with detailed measurements of these flows from both up flow and down flow from the transformation to document the process of dense to dilute flow transition. The field characterization includes mapping of the flows, grain size analysis, documenting flow direction indicators, comminution rounding, thermal proxies for air entrainment, and bed form documentation. We used a three-dimensional, multiphase (Eulerian-Eulerian-Lagrangian, EEL) modeling approach to describe size sorting, concentration gradients, and stresses in these evolving flows using the topography of the near Chambo River crossing (Dufek and Bergantz, 2007). The numerical models reveal extensive entrainment in the surge-generating phase of the flow, and secondary plume generation as fine ash in transported by hot gases higher into the atmosphere. Granular waves develop in the confined channels of the dense flow resulting bed shear stress perturbations. These granular instabilities and entrainment result in pulsing conditions in the surge, accounting for much of the unsteady behavior that results in fluctuations in grain size and bed form in the surge deposits.
NASA Astrophysics Data System (ADS)
Mayo, Alan L.; Himes, Scott A.; Tingey, David G.
2013-12-01
Thermal springs in the Idaho batholith (USA) discharge at discrete locations along a 50+ km reach of the Middle Fork of the Boise River (MFBR). Recharge water flows through Basin and Range extension fractures where it is heated by the geothermal gradient and ultimately discharges from the damage zone of the trans-Challis faults located near the bottom of the MFBR. Stable isotopes of water, 14C groundwater ages, fracture and fault orientations, fracture volume changes due to chemical evolution, and recharge area calculations suggest that the thermal springs issue from individual hydrothermal systems and that they are self-organizing. Water evolves chemically along flow paths, dissolving feldspars and precipitating secondary minerals. Secondary minerals accumulate in less-efficient fractures and are flushed from the more efficient ones. Flow-area calculations using heat-flow, exponential decay-of-porosity, and curve-intersection methods show that many of the thermal systems extend beyond their immediate topographic watershed, and that some capture water from adjacent watersheds. Geochemical/flow feedback loops that provide a mechanism for self-organization are modeled using PHREEQC, and positive and negative fracture volume changes are calculated. Criteria for identifying self-organizing granitoid thermal groundwater systems are suggested.
NASA Astrophysics Data System (ADS)
Chen, Gujun; He, Shengping; Li, Yugang; Guo, Yintao; Wang, Qian
2016-02-01
In the present work, a mathematical model was developed to understand the multiphase flow behavior in a Rheinsahl-Heraeus (RH) reactor by using the Euler-Euler approach, and the effects of initial bubble diameter, nonequilibrium expansion of bubble caused by sudden thermal effect and sharp pressure drop, and various interphase forces were considered and clarified. The simulation results of mixing time, liquid circulation rate, and local liquid velocity in RH agree well with the measured results. The result indicates that the initial bubble diameter has a weak impact on the multiphase flow but that the bubble expansion has a tremendous impact on it for an actual RH. Meanwhile, the drag force and turbulent dispersion force strongly influence the multiphase flow, whereas the lift force and virtual mass force only have negligible influence on it. Furthermore, the turbulent dispersion force should be responsible for reasonable prediction of multiphase flow behavior in the RH reactor.
Li, Na; Richoux, Romain; Perruchot, Marie-Hélène; Boutinaud, Marion; Mayol, Jean-François; Gagnaire, Valérie
2015-01-01
Flow cytometry has been used as a routine method to count somatic cells in milk, and to ascertain udder health and milk quality. However, few studies investigate the viability of somatic cells and even fewer at a subpopulation level to follow up how the cells can resist to various stresses that can be encountered during technological processes. To address this issue, a flow cytometry approach was used to simultaneously identify cell types of bovine milk using cell-specific antibodies and to measure the cell viability among the identified subpopulations by using a live/dead cell viability kit. Confirmation of the cell viability was performed by using conventional microscopy. Different physico-chemical treatments were carried out on standardized cell samples, such as heat treatment, various centrifugation rates and storage in milk or in PBS pH 7.4 for three days. Cytometry gating strategy was developed by using blood cell samples stored at 4°C in PBS and milk cell samples heat-treated at 80°C for 30 min as a control for the maximum (95.9%) and minimum (0.7%) values of cell viability respectively. Cell viability in the initial samples was 39.5% for all cells and varied for each cell population from 26.7% for PMNs, to 32.6% for macrophages, and 58.3% for lymphocytes. Regarding the physico-chemical treatments applied, somatic cells did not sustain heat treatment at 60°C and 80°C in contrast to changes in centrifugation rates, for which only the higher level, i.e. 5000×g led to a cell viability decrease, down to 9.4%, but no significant changes within the cell subpopulation distribution were observed. Finally, the somatic cells were better preserved in milk after 72h storage, in particular PMNs, that maintained a viability of 34.0 ± 2.9% compared to 4.9±1.9% in PBS, while there was almost no changes for macrophages (41.7 ± 5.7% in milk vs 31.2 ± 2.4% in PBS) and lymphocytes (25.3 ± 3.0% in milk vs 11.4 ± 3.1% in PBS). This study provides a new array to better
NASA Technical Reports Server (NTRS)
Rudy, D. H.; Bushnell, D. M.
1973-01-01
Prandtl's basic mixing length model was used to compute 22 test cases on free turbulent shear flows. The calculations employed appropriate algebraic length scale equations and single values of mixing length constant for planar and axisymmetric flows, respectively. Good agreement with data was obtained except for flows, such as supersonic free shear layers, where large sustained sensitivity changes occur. The inability to predict the more gradual mixing in these flows is tentatively ascribed to the presence of a significant turbulence-induced transverse static pressure gradient which is neglected in conventional solution procedures. Some type of an equation for length scale development was found to be necessary for successful computation of highly nonsimilar flow regions such as jet or wake development from thick wall flows.
NASA Astrophysics Data System (ADS)
Tutolo, B. M.; Luhmann, A. J.; Kong, X.; Seyfried, W. E.; Saar, M. O.
2012-12-01
the experimental system. Significantly, the application of these rate laws to feldspathic systems requires accurate thermodynamic data for primary and secondary aluminum-bearing minerals and aqueous species, particularly when modeling the transition from far-from-equilibrium to near-equilibrium rates as the experiment progresses. Overall, the reactive transport modeling approach presented here strengthens predictions of subsurface response to CO2 injection by integrating advanced characterization methods, accurate thermodynamic and kinetic data, and properly scaled geochemical and physical flow models.
NASA Astrophysics Data System (ADS)
Hardy, R. J.; Best, J.; Parsons, D. R.; Keevil, G.; Rosser, N.
2009-12-01
Turbulence in gravel-bed rivers (GBR’s) is not a simple random field: visualisation and multipoint measurements show it is possible to decompose complex, multi-scaled, quasi-random flow fields into elementary organized structures which posses both spatial and temporal coherence. These coherent flow structures (CFS’s) are generated through topographic forcing of the typically shallow flow over the detailed micro-topography of the gravel bed. However, we currently have little understanding of the kinematic (size, scaling, shape, vorticity & energy) & dynamic (origin, stability, growth, genesis & contribution to averages) characteristics of theses CFS’s, which are central to improving our understanding of turbulent flow, the contribution of CFS’s to fluid mixing, bed shear stress and hence sediment transport. This lack of process understanding of turbulence in GBR’s stems from two fundamental shortcomings: i) previous studies have used Eulerian time series to quantitatively determine processes, which may be interpolated to examine the whole flow field, rather than studying the complete instantaneous holistic flow field; and ii) whole flow field visualization provides a qualitative Lagrangian viewpoint but very little quantitative information. Here, we demonstrate a novel turbulence mapping technique using a combined digital Particle Image Velocimetry and planar Laser-Induced Fluorescence technique to allow a combined Lagrangian-Eulerian approach to understand both the kinematic and dynamic properties coherent flow structures over a gravel bed in a flume. The results demonstrate the dynamic interplay between fluid within individual identifiable coherent flow structures and the structure themselves as the fluid advects over the bed.
A simple and rapid one-step continuous-flow synthesis route has been developed for the preparation of chromene derivatives from the reaction of aromatic aldehydes, α-cyanomethylene compounds and naphthols. In this contribution, a one-step continuous-flow protocol in a continuous ...
NASA Astrophysics Data System (ADS)
Bhowmik, Moumita; Bera, Premananda
The influence of curvature parameter on fully developed mixed convective flow in a vertical annulus filled with porous medium under local thermal non-equilibrium (LTNE) state has been addressed here. Since the curvature parameter (C) describes the size of the enclosure, therefore the main emphasize is given to understand its impact on other controlling parameters. Based on computational results, C has a significant impact on both heat transfer rate as well as flow profiles for stably stratified flow. It has a tendency to reduce the magnitude of the maximum velocity. It is also observed that depending on other parameters, increment in C may have tendency to make the velocity profile free from back flow. The heat transfer rate is obtained maximum at a small value of C which is independent of media permeability and converges asymptotically on increasing C. At the end, the linear stability analysis based on normal mode technique has been used to verify the results obtained from basic flow study. Overall, from both basic flow as well as linear stability results, it is found that increment in C makes the flow profile smooth which means C has tendency to stabilize the flow.
Choi, Dongwhi; Lee, Donghyeon; Sung Kim, Dong
2015-01-01
In this study, we first suggest a simple approach to characterize configuration of gas-aqueous liquid two–phase flow based on discrete solid-liquid contact electrification, which is a newly defined concept as a sequential process of solid-liquid contact and successive detachment of the contact liquid from the solid surface. This approach exhibits several advantages such as simple operation, precise measurement, and cost-effectiveness. By using electric potential that is spontaneously generated by discrete solid–liquid contact electrification, the configurations of the gas-aqueous liquid two-phase flow such as size of a gas slug and flow rate are precisely characterized. According to the experimental and numerical analyses on parameters that affect electric potential, gas slugs have been verified to behave similarly to point electric charges when the measuring point of the electric potential is far enough from the gas slug. In addition, the configuration of the gas-aqueous liquid two-phase microfluidic system with multiple gas slugs is also characterized by using the presented approach. For a proof-of-concept demonstration of using the proposed approach in a self-triggered sensor, a gas slug detector with a counter system is developed to show its practicality and applicability. PMID:26462437
Incompressible laminar flow through hollow fibers: a general study by means of a two-scale approach
NASA Astrophysics Data System (ADS)
Borsi, Iacopo; Farina, Angiolo; Fasano, Antonio
2011-08-01
We study the laminar flow of an incompressible Newtonian fluid in a hollow fiber, whose walls are porous. We write the Navier-Stokes equations for the flow in the inner channel and Darcy's law for the flow in the fiber, coupling them by means of the Beavers-Joseph condition which accounts for the (possible) slip at the membrane surface. Then, we introduce a small parameter {\\varepsilon ≪ 1} (the ratio between the radius and the length of the fiber) and expand all relevant quantities in powers of ɛ. Averaging over the fiber cross section, we find the velocity profiles for the longitudinal flow and for the cross-flow, and eventually, we determine the explicit expression of the permeability of the system. This work is also preliminary to the study of more complex systems comprising a large number of identical fibers (e.g., ultrafiltration modules and dialysis).
Martins, S A; Daily, W D; Ramirez, A L
2002-01-31
used to solve for the electrical conductivity distribution in the region bounded by the electrode arrays. Groundwater movement resulting from a leak or surface spill will produce measurable conductivity changes that have been imaged using ERT or EIT. The kind of laboratory scale experiments supported by this work will help us to better understand the connection between imaged conductivity anomalies and the groundwater or contaminant flow that causes them. This work will also help to demonstrate the feasibility or value of doing lab experiments in imaging that can be applied to interpreting field-scale experiments. A secondary objective of this study was to initiate a collaboration with researchers at the Rensselaer Polytechnic Institute (RPI; Troyl NY) who are also participants in the newly created NSF Center for Subsurface Imaging and Sensing Systems (CenSSIS) which is managed in part by RPI. During the course of this study C.R. Carrigan and W. Daily visited the electromagnetic imaging lab at RPI to initiate discussions on subsurface imaging technology with Professors David Isaacson, Jon Newell, Gary Salunier and their research graduate students. A major goal of CenSSIS is to promote collaborations among researchers with imaging backgrounds in different disciplines (geosciences, biomedical, civil engineering and biomedical) that will lead to new solutions of common subsurface imaging problems. The geophysical test section constructed for this study included electrode arrays that resemble biomedical array distributions. Comparing images of the same target produced with the 4-array geophysical approach and with the biomedical imaging approach will help us to better understand differences and advantages that are characteristic of the two imaging methods. Our initial interactions with the researchers at RPI concluded that this was a viable problem to consider. The support for this subsequent research will come from a 3-year Office of Basic Energy Sciences (BES) proposal
NASA Astrophysics Data System (ADS)
Ergun, Sule
In the case of a postulated loss of coolant accident (LOCA) in a nuclear reactor, an accurate prediction of clad temperature is needed to determine the safety margins. The large break LOCA analyses can be divided in to three time periods. These periods are blowdown, refill and reflood. During the blowdown and reflood phases of the LOCA, when the local void fraction is greater than 80% and the wall is at a temperature above minimum film boiling temperature (Tmin), heat is transferred from the fuel rod to a continuous vapor flow with dispersed droplets. The high void fraction mixture of droplets and vapor provide cooling to prevent the clad temperature from exceeding the safety limit. The heat transfer process for high void fraction mixture is called dispersed flow film boiling (DFFB). This thesis has been modeled DFFB in the reflood phase of a LOCA in a pressurized water reactor (PWR) rod bundle. In this study, the modifications and modification requirements for the COBRA-TF code to obtain a five field Eulerian - Eulerian modeling for two-phase DFFB is described. COBRA-TF is a best estimate code developed for the rod bundle analysis and has four fields, namely, vapor, entrained drop and continuous liquid film. COBRA-TF has a detailed reflood package which takes effect of spacer grids on heat transfer into account. This study has a detailed description of code's solution scheme and the models used for dispersed flow film boiling. The dispersed flow film boiling heat transfer model of the COBRA-TF code has been modified by adding a small droplet field to the code as the fifth field. The effect of smaller, thermally more active droplets on heat, mass and momentum transfer during DFFB has been modeled. Since the large drop break up due to spacer grids is one of the reasons for small droplet generation, the spacer grid models of the COBRA-TF have been revised and modified. In addition to small droplet generation, the spacer grid rewet is an important aspect of heat
NASA Astrophysics Data System (ADS)
Ijiri, Yuji; Saegusa, Hiromitsu; Sawada, Atsushi; Ono, Makoto; Watanabe, Kunio; Karasaki, Kenzi; Doughty, Christine; Shimo, Michito; Fumimura, Kenichi
2009-01-01
Qualitative evaluation of the effects of uncertainties originating from scenario development, modeling approaches, and parameter values is an important subject in the area of safety assessment for high-level nuclear waste disposal sites. In this study, regional-scale groundwater flow analyses for the Tono area, Japan were conducted using three continuous models designed to handle heterogeneous porous media. We evaluated the simulation results to quantitatively analyze uncertainties originating from modeling approaches. We found that porous media heterogeneity is the main factor which causes uncertainties. We also found that uncertainties originating from modeling approaches greatly depend on the types of hydrological structures and heterogeneity of hydraulic conductivity values in the domain assigned by modelers. Uncertainties originating from modeling approaches decrease as the amount of labor and time spent increase, and iterations between investigation and analyses increases.
Ijiri, Yuji; Saegusa, Hiromitsu; Sawada, Atsushi; Ono, Makoto; Watanabe, Kunio; Karasaki, Kenzi; Doughty, Christine; Shimo, Michito; Fumimura, Kenichi
2009-01-26
Qualitative evaluation of the effects of uncertainties originating from scenario development, modeling approaches, and parameter values is an important subject in the area of safety assessment for high-level nuclear waste disposal sites. In this study, regional-scale groundwater flow analyses for the Tono area, Japan were conducted using three continuous models designed to handle heterogeneous porous media. We evaluated the simulation results to quantitatively analyze uncertainties originating from modeling approaches. We found that porous media heterogeneity is the main factor which causes uncertainties. We also found that uncertainties originating from modeling approaches greatly depend on the types of hydrological structures and heterogeneity of hydraulic conductivity values in the domain assigned by modelers. Uncertainties originating from modeling approaches decrease as the amount of labor and time spent increase, and iterations between investigation and analyses increases. PMID:19064302
NASA Astrophysics Data System (ADS)
Gray, William G.; Miller, Cass T.
2009-05-01
This work is the fifth in a series of papers on the thermodynamically constrained averaging theory (TCAT) approach for modeling flow and transport phenomena in multiscale porous medium systems. The general TCAT framework and the mathematical foundation presented in previous works are used to develop models that describe species transport and single-fluid-phase flow through a porous medium system in varying physical regimes. Classical irreversible thermodynamics formulations for species in fluids, solids, and interfaces are developed. Two different approaches are presented, one that makes use of a momentum equation for each entity along with constitutive relations for species diffusion and dispersion, and a second approach that makes use of a momentum equation for each species in an entity. The alternative models are developed by relying upon different approaches to constrain an entropy inequality using mass, momentum, and energy conservation equations. The resultant constrained entropy inequality is simplified and used to guide the development of closed models. Specific instances of dilute and non-dilute systems are examined and compared to alternative formulation approaches.
NASA Astrophysics Data System (ADS)
Carling, Paul; Kleinhans, Maarten; Leyland, Julian; Besozzi, Louison; Duranton, Pierre; Trieu, Hai; Teske, Roy
2014-05-01
Understanding of flow resistance of forested floodplains is essential for floodplain flow routing and floodplain reforestation projects. Although the flow resistance of grass-lined channels is well-known, flow retention due to flow-blocking by trees is poorly understood. Flow behaviour through tree-filled channels or over forested floodplain surfaces has largely been addressed using laboratory studies of artificial surfaces and vegetation. Herein we take advantage of a broad, shallow earthen experimental outdoor channel with headwater and tailwater controls. The channel was disused and left undisturbed for more than 20 years. During this time period, small deciduous trees and a soil cover of grass, herbs and leaf-litter established naturally. We measured flow resistance and fluid retention in fifteen controlled water discharge experiments for the following conditions: (a) natural cover of herbs and trees; (b) trees only and; (c) earthen channel only. In the b-experiments the herbaceous groundcover was first removed carefully and in the c-experiments the trees were first cut flush with the earthen channel floor. Rhodamine-B dye was used to tag the flow and the resultant fluorescence of water samples were systematically assayed through time at two stations along the length of the channel. Dilution-curve data were analysed within the Aggregated Dead Zone (ADZ) framework to yield bulk flow parameters including dispersion, fluid retention and flow resistance parameters after the procedure of Richardson & Carling (2006). The primary response of the bulk flow to vegetation removal was an increase in bulk velocity, with depth and wetted width decreasing imperceptibly at the resolution of measurement. An overall reduction in flow resistance and retention occurred as discharge increased in all experiments and flow retention. Retentiveness was more prominent during low flow and for all three experimental conditions tended to converge on a constant low value for high
NASA Astrophysics Data System (ADS)
Blahut, J.; Luna, B. Quan; Akbas, S. O.; van Westen, C. J.
2009-04-01
On Sunday morning of 13th July 2008, after more than two days of intense rainfall, several debris and mud flows were released in the central part of Valtellina valley between Morbegno and Berbenno. One of the largest debris flows occurred in Selvetta, a fraction of Colorina municipality. The debris flow event was reconstructed after extensive field work and interviews with local inhabitants and civil protection teams. At first several rock blocks about 2 m3 in size fell down from the direction of the torrent. The blocks were followed by a wave of debris and mud that immediately destroyed one building and caused damage to other nine houses. A stream flow following the debris flow consisting of fine mud with high water content that partially washed away the accumulation of deposits from the debris phase could also be distinguished. Geomorphologic investigations allowed identification of five main sections of the flow: 1) the proper scarp; 2) path in the forested area; 3) path on the alpine meadows; 4) accelerating section; 5) accumulation area. The initiation area of the flow is situated at 1760 m. a.s.l. (1480 m above the deposition zone) in a coniferous forest. The proper scarp consisted of an area of approximately 20 m2 in size, and a height of about 0.8 m. The final volume of the debris was estimated by field mapping to be between 12 000 and 15 000 m3. It was observed that erosion and entrainment played an important role in the development of the debris flow. The Selvetta event was modelled with the FLO2D program. FLO2D is an Eulerian formulation with a finite differences numerical scheme that requires the specification of an input hydrograph. The internal stresses are isotropic and the basal shear stresses are calculated using a quadratic model. Entrainment was modeled at each section of the flow, and different hydrographs were produced in agreement with the behavior of the debris flow during its course. The significance of calculated values of pressure and
NASA Astrophysics Data System (ADS)
Lyons, Oisín F. P.; Quinn, Cian; Persoons, Tim; Murray, Darina B.
2012-11-01
This paper presents research in the area of heat transfer and fluid dynamics in an impinging atomizing air/water mist jet. Time averaged and fluctuating local surface heat transfer results obtained by microfoil and hot film sensors are correlated with flow field measurements of droplet diameter and velocity obtained by shadowgraph imaging and droplet tracking velocimetry. This paper seeks to understand the linkage between the atomization process in the nozzle, the two-phase flow dynamics and the surface heat transfer characteristics.
A microfluorometric method for quantifying RNA and DNA in terrestrial insects
Kyle, M.; Watts, T.; Schade, J.; Elser, J.J.
2003-01-01
Evidence is accumulating for a mechanistic linkage between body phosphorus content and growth and reproduction of individual organisms, due in part to variation in allocation of resources to ribosomal RNA. Testing this connection requires reliable methods of quantifying the nucleic acid content of individual organisms. Although methods for quantifying nucleic acids are available for a wide array of organisms, adaptation of such methods for study of insects has been neglected. Sensitive stains and high throughput fluorometric measurements are now available that substantially improve past methodologies. Here we present methods for the extraction and quantification of insect RNA and DNA based on the use of N-lauroylsarcosine and sonication for extraction, the nucleases RNase and DNase, and the use of microplate fluorescent assays to quantify nucleic acids as percent of body weight in insects. We illustrate the method using Drosophila and curculionid weevils. PMID:15841218
NASA Astrophysics Data System (ADS)
Krueger, Jiem; Leue, Martin; Heinze, Stefanie; Bachmann, Jörg
2016-04-01
During unsaturated water conditions, water flow occurs in the soil mainly by water film flow and depends on moisture content and pore surface properties. More attention is attributed to coatings enclosing soil particles and thus may affect wetting properties as well as hydraulic soil functions. Particle coatings are most likely responsible for many adsorption processes and are expected to favor local heterogeneous microstructure with enhanced biological activity. Many of the effects described cannot be detected on the basis of conventional soil column experiments, which were usually made to study soil hydraulic processes or surface - soil solution exchange processes. The general objective of this study was to develop a new field sampling method to unravel heterogeneous flow processes on small scales in an undisturbed soil under controlled lab conditions. This will be done by using modified flow cells (Plexiglas). Beside the measurements within a flow cell as breakthrough curves, the developed technique has several additional advantages in contrast to common columns or existing flow chamber/cell designs. The direct modification from the sampling frame to the flow cell provides the advantage to combine several analyses. The new technique enables to cut up to 5 thin undisturbed soil slices (quasi-replicates) down to 10 and/or 5 mm. Relative large particles, for instance, may limit this sampling method. The large observation area of up to 150 cm2 allows the characterization of particle surface properties in a high spatial resolution within an undisturbed soil sample. This sampling technique, as shown in our study, has the opportunity to link soil wetting hydraulic and several particle surface properties to spatial soil heterogeneities. This was shown with tracer experiments, small-scale contact angle measurements and analyses of the spatial distribution of functional groups of soil organic matter via DRIFT mapping.
NASA Astrophysics Data System (ADS)
Goushcha, Oleg
In the present work we demonstrate the feasibility to harness energy from fluid flows by using piezoelectric generators. These ac-coupled devices convert fluid kinetic energy, which otherwise would be wasted, into electrical energy. The available power density in a flowing fluid is proportional to the cube of its velocity and if it is properly harvested can be used for continuously powering very small electronic devices or can be rectified and stored for intermittent use. A key quantity in these applications which affects the performance is the forcing which the fluid exerts on the harvesters. An analytical solution is presented for the Pressure Poisson Equation (PPE) that uses Particle Image Velocimetry (PIV) field data to find the pressure in a flow domain and to calculate the pressure and therefore the force exerted by the fluid on the solid surface. The solution provides a favorable method of calculating pressure field from PIV data as it eliminates the need to compute higher order derivatives of velocity on the domain that are present in viscous terms as well as eliminates the need to integrate Navier-Stokes equations to find the pressure along the boundaries of interest. The solution is validated against a theoretical solution for a pressure distribution inside a tornado-like vortex; pressure solutions obtained by derivative momentum transform method for a vortex flow and some experimental results for the pressure distribution inside a turbulent boundary layer. Several experiments were carried out in which pressure was calculated using PPE: i) a discrete vortex passing over a simple cantilever beam harvester ii) a simple cantilever harvester placed in the boundary layer iii) a self-excited harvester placed in the free stream flow. In a discrete vortex experiment, the self-propelled vortex is passed over the cantilever beam. The pressure distribution and the net force of the beam are calculated by solving PPE as the vortex passes over the beam. In a boundary
NASA Astrophysics Data System (ADS)
Chang, Tsang-Jung; Wang, Chia-Ho; Chen, Albert S.
2015-05-01
In this study, we developed a novel approach to simulate dynamic flow interactions between storm sewers and overland surface for different land covers in urban areas. The proposed approach couples the one-dimensional (1D) sewer flow model (SFM) and the two-dimensional (2D) overland flow model (OFM) with different techniques depending on the land cover type of the study areas. For roads, pavements, plazas, and so forth where rainfall becomes surface runoff before entering the sewer system, the rainfall-runoff process is simulated directly in the 2D OFM, and the runoff is drained to the sewer network via inlets, which is regarded as the input to 1D SFM. For green areas on which rainfall falls into the permeable ground surface and the generated direct runoff traverses terrain, the deduction rate is applied to the rainfall for reflecting the soil infiltration in the 2D OFM. For flat building roofs with drainage facilities allowing rainfall to drain directly from the roof to sewer networks, the rainfall-runoff process is simulated using the hydrological module in the 1D SFM where no rainfall is applied to these areas in the 2D OFM. The 1D SFM is used for hydraulic simulations in the sewer network. Where the flow in the drainage network exceeds its capacity, a surcharge occurs and water may spill onto the ground surface if the pressure head in a manhole exceeds the ground elevation. The overflow discharge from the sewer system is calculated by the 1D SFM and considered a point source in the 2D OFM. The overland flow will return into the sewer network when it reaches an inlet that connects to an un-surcharged manhole. In this case, the inlet is considered as a point sink in the 2D OFM and an inflow to a manhole in the 1D SFM. The proposed approach was compared to other five urban flood modelling techniques with four rainfall events that had previously recorded inundation areas. The merits and drawbacks of each modelling technique were compared and discussed. Based on the
NASA Astrophysics Data System (ADS)
Jäger, Paul; Zitek, Andreas
2010-05-01
Currently the EU-Water Framework Directive (WFD) represents the driving force behind the assessment for rehabilitation and conservation of aquatic resources throughout Europe. Hydropower production, often considered as "green energy", in the past has put significant pressures on river systems like fragmentation by weirs, impoundment, hydropeaking and water abstraction. Due to the limited availability of data for determining ecologically acceptable flow for rivers at water abstraction sites, a special monitoring program was conducted in the federal state of Salzburg in Austria from 2006 to 2009. Water abstraction sites at 19 hydropower plants, mostly within the trout region of the River Salzach catchment, were assessed in detail with regard to the effect of water abstraction on fish and macrozoobenthos. Based on a detailed assessment of the specific local hydro-morphological and biological situations, the validity of natural low flow criteria (Absolute Minimum Flow - AMF, the lowest daily average flow ever measured and Mean Annual Daily Low Flow - MADLF) as starting points for the determination of an ecologically acceptable flow was tested. It was assessed, if a good ecological status in accordance with the EU-WFD can be maintained at natural AMF. Additionally it was tested, if important habitat parameters describing connectivity, river type specific flow variability and river type specific habitats are maintained at this discharge. Habitat modelling was applied in some situations. Hydraulic results showed that at AMF the highest flow velocity classes were lost in most situations. When AMF was significantly undercut, flow velocities between 0,0 - 0,4 m/s became dominant, describing the loss of the river type specific flow character, leading to a loss of river type specific flow variability and habitats and increased sedimentation of fines. Furthermore limits for parameters describing connectivity for fish like maximum depth at the pessimum profile and minimum flow
Esralew, R.A.
2009-01-01
Multiple-regression analysis was used to develop equations for estimating annual and seasonal flow-duration statistics at ungaged streams in and near Oklahoma that are not substantially affected by human alteration. Ordinary least-squares and left-censored (Tobit) multiple-regression techniques were used to develop equations that relate these statistics, from continuous streamflow data at gaged locations with 10 or more years of record, to physical and climatic basin characteristics. Separate equations were developed to estimate these statistics for stations within similar hydrologic and geologic regions. Use of separate regressions by region substantially improved the accuracy of the estimate for streams in eastern and central Oklahoma when compared with estimating equations developed for the entire State, especially for regressions estimating lower flow duration values. For all regions, the equations were more reliable for estimating higher flow duration values. The accuracy of regressions for estimating flow duration statistics in western Oklahoma was very poor, especially for lower flow duration values. ?? 2009 ASCE.
Esralew, Rachel A.
2009-01-01
Multiple-regression analysis was used to develop equations for estimating annual and seasonal flow-duration statistics at ungaged streams in and near Oklahoma that are not substantially affected by human alteration. Ordinary least-squares and left-censored (Tobit) multiple-regression techniques were used to develop equations that relate these statistics, from continuous streamflow data at gaged locations with 10 or more years of record, to physical and climatic basin characteristics. Separate equations were developed to estimate these statistics for stations within similar hydrologic and geologic regions. Use of separate regressions by region substantially improved the accuracy of the estimate for streams in eastern and central Oklahoma when compared with estimating equations developed for the entire State, especially for regressions estimating lower flow duration values. For all regions, the equations were more reliable for estimating higher flow duration values. The accuracy of regressions for estimating flow duration statistics in western Oklahoma was very poor, especially for lower flow duration values.
Dynamic gas slippage: a unique dual-mechanism approach to the flow of gas in tight formations
Ertekin, T.; King, G.R.; Schwerer, F.C.
1983-01-01
A mathematical formulation, applicable to both numeric simulation and transient well analysis, describing the flow of gas in very tight porous media has been developed. Unique to this formulation is the dual- mechanism transport of gas. In this formulation, gas is assumed to be traveling under the influence of 2 fields: a concentration field and a pressure field. Transport through the concentration field is a Knudsen flow process and is modeled with Fick's Law of diffusion. Transport through the pressure field is a laminar process and is modeled with Darcy's Law (inertial-turbulent effects are ignored). The combination of these 2 flow mechanisms rigorously yields a composition, pressure, and saturation dependent slippage factor. 21 references.
Laser-induced fluorescence of flowing samples as an approach to single-molecule detection in liquids
Dovichi, N.J.; Martin, J.C.; Jett, J.H.; Trkula, M.; Keller, R.A.
1984-03-01
A flow cytometer system was used to detect aqueous rhodamine 6G by laser-induced fluorescence. Best results were obtained with careful spectral and spatial filtering. At the detection limit, the probability of a rhodamine 6G molecule being present in the detector's probed volume of 11 pL is about 0.6 . With a flow rate of 0.42 ..mu..L/s, a detection limit of 8.9 x 10/sup -14/ M was obtained for a 1-s time constant. At the detection limit, 18 ag or 22,000 molecules of rhodamine 6G flowed through the probed volume during the signal integration period. Signal linearity extends over greater than 5 orders of magnitude limited only by saturation of the detection electronics at high concentration. The results presented here allow a projection to single-molecule detection with reasonable improvements to the apparatus. 25 references, 5 figures, 7 tables.
NASA Astrophysics Data System (ADS)
Choudhary, B. K.; Christopher, J.
2016-06-01
The comparative tensile flow and work-hardening behavior of P9 steel in two different product forms, normalized and tempered plate and thick section tube plate forging, and P91 steel were investigated in the framework of the dislocation dynamics based Estrin-Mecking (E-M) one-internal-variable approach. The analysis indicated that the flow behavior of P9 and P91 steels was adequately described by the E-M approach in a wide range of temperatures. It was suggested that dislocation dense martensite lath/cell boundaries and precipitates together act as effective barriers to dislocation motion in P9 and P91 steels. At room and intermediate temperatures, the evolution of the internal-state variable, i.e., the dislocation density with plastic strain, exhibited insignificant variations with respect to temperature. At high temperatures, a rapid evolution of dislocation density with plastic strain toward saturation with increasing temperature was observed. The softer P9 steel tube plate forging exhibited higher work hardening in terms of larger gains in the dislocation density and flow stress contribution from dislocations than the P9 steel plate and P91 steel at temperatures ranging from 300 K to 873 K (27 °C to 600 °C). The evaluation of activation energy suggests that the deformation is controlled by cross-slip of dislocations at room and intermediate temperatures, and climb of dislocations at high temperatures. The relative influence of initial microstructure on flow and work-hardening parameters associated with the E-M approach was discussed in the three temperature regimes displayed by P9 and P91 steels.
NASA Astrophysics Data System (ADS)
Yoshikawa, S.; Yanagawa, A.; Khajuria, A.; Sui, P.; Iwasaki, Y.; Hirano, K.; Mahendran, R.; Koirala, S.; Hirabayashi, Y.; Yoshimura, C.; Kanae, S.
2013-06-01
Changes in river discharge due to human activities and climate change would affect the sustainability of freshwater ecosystem. In order to globally assess the future status of freshwater ecosystem under regime shifts in river discharge, global-scale hydrological simulations need to be connected with a model to estimate the soundness of freshwater ecosystem. However, the explicit combination of those two on a global scale is still in its infancy. A couple of statistical models are introduced here to link flow regimes to fish species richness (FSR): one based on a linear relationship between FSR and mean river discharge, and the other based on a relationship between FSR and ecologically relevant flow indices involving other several flow characteristics as well as mean river discharge. The former one has been sometimes used in global simulation studies, but the latter one is newly introduced here in the context of global simulation. These statistical models for estimating FSR were combined with a set of global river discharge simulations to evaluate the potential impact of flow alterations due to climate change on FSR changes. Generally, future reductions in FSR by the latter method are larger and much more scattered rather than by the former method. In arid regions, both models provide reductions in FSR because mean discharge is projected to decrease from past to future, although the magnitude of reduction in FSR is different. On the other hand, large reductions in FSR only by the latter model are detected in heavy-snow regions due to the increases of mean discharge and frequency of low and high flows. Although we need further research to conclude which is more relevant, this study demonstrates that the new model could show a considerably different behavior in assessing the global impact of flow alteration on freshwater ecosystem change.
NASA Astrophysics Data System (ADS)
Yoshikawa, S.; Yanagawa, A.; Iwasaki, Y.; Sui, P.; Koirala, S.; Hirano, K.; Khajuria, A.; Mahendran, R.; Hirabayashi, Y.; Yoshimura, C.; Kanae, S.
2014-02-01
Changes in river discharge due to human activities and climate change would affect the sustainability of freshwater ecosystems. To globally assess how changes in river discharge will affect the future status of freshwater ecosystems, global-scale hydrological simulations need to be connected with a model to estimate the durability of freshwater ecosystems. However, the development of this specific modelling combination for the global scale is still in its infancy. In this study, two statistical methods are introduced to link flow regimes to fish species richness (FSR): one is based on a linear relationship between FSR and mean river discharge (hereafter, FSR-MAD method), and the other is based on a multi-linear relationship between FSR and ecologically relevant flow indices involving several other flow characteristics and mean river discharge (FSR-FLVAR method). The FSR-MAD method has been used previously in global simulation studies. The FSR-FLVAR method is newly introduced here. These statistical methods for estimating FSR were combined with a set of global river discharge simulations to evaluate the potential impact of climate-change-induced flow alterations on FSR changes. Generally, future reductions in FSR with the FSR-FLVAR method are greater and much more scattered than with the FSR-MAD method. In arid regions, both methods indicate reductions in FSR because mean discharge is projected to decrease from past to future, although the magnitude of reductions in FSR is different between the two methods. In contrast, in heavy-snow regions a large reduction in FSR is shown by the FSR-FLVAR method due to increases in the frequency of low and high flows. Although further research is clearly needed to conclude which method is more appropriate, this study demonstrates that the FSR-FLVAR method could produce considerably different results when assessing the global role of flow alterations in changing freshwater ecosystems.
Ardagh, Michael
2015-08-21
It is essential we manage the capacity of our hospitals so that acute demand can be accommodated without developing queues for care and backlogs of work. This paper presents a comprehensive model for improving patient flow in our hospitals by attending carefully to both the demand and capacity states of the hospital and maximising efficient flow of our acute patient journeys. The model includes attention to the patient journey as the central focus, with an overarching governance structure and an underpinning sophisticated operations structure. PMID:26367513
Bulychev, Alexander A; Alova, Anna V; Rubin, Andrey B
2013-06-01
Emerging evidence suggests that cytoplasmic streaming can regulate the plasma-membrane H(+) transport and photosynthetic electron flow. Microfluorometric and surface pH measurements on Chara corallina internodes revealed the transmission of photoinduced signals by the cytoplasmic flow for a distance of few millimeters from the site of stimulus application. When a 30-s pulse of bright light was locally applied, the downstream cell regions responded with either release or enhancement of non-photochemical quenching of chlorophyll fluorescence, depending on the background irradiance of the analyzed cell area. Under dim background irradiance (<20 μmol m(-2) s(-1)), the arrival of the distant signal from the brightly illuminated 400-μm-wide zone elevated the maximal fluorescence F m (') in the analyzed downstream area, whereas at higher background irradiances it induced strong quenching of F m (') . At intermediate irradiances the increase and decrease in F m (') appeared as two successive waves. The transition between the F m (') responses of opposite polarities occurred at a narrow threshold range of irradiances. This indicates that inevitable slight variations in irradiance at the bottom chloroplast layer combined with the cyclosis-transmitted signals may contribute to the formation of a photosynthetic activity pattern. The rapid cyclosis-mediated release of non-photochemical quenching, unlike the delayed response of opposite polarity, was associated with opening of H(+) (OH(-))-conducting plasma membrane channels, as evidenced by the concurrent alkaline pH shift on the cell surface. It is proposed that the initial increase in F m (') after application of a distant photostimulus is determined, among other factors, by the wave of alkaline cytoplasmic pH. PMID:23467782
ERIC Educational Resources Information Center
Lloyd, Rebecca
2015-01-01
Background: Physical Education (PE) programmes are expanding to include alternative activities yet what is missing is a conceptual model that facilitates how the learning process may be understood and assessed beyond the dominant sport-technique paradigm. Purpose: The purpose of this article was to feature the emergence of a Function-to-Flow (F2F)…
This report documents initial efforts to identify innovative strategies for managing the effects of wet-weather flow in an urban setting. It served as a communication tool and a starting point for discussion with experts. As such, the document is a compilation of literature rev...
ERIC Educational Resources Information Center
Brickner, Daniel R.; McCombs, Gary B.
2004-01-01
In this article, the authors provide an instructional resource for presenting the indirect method of the statement of cash flows (SCF) in an introductory financial accounting course. The authors focus primarily on presenting a comprehensive example that illustrates the "why" of SCF preparation and show how journal entries and T-accounts can be…
Doyle, Jessica M.; Gleeson, Tom; Manning, Andrew H.; Mayer, K. Ulrich
2015-01-01
Environmental tracers provide information on groundwater age, recharge conditions, and flow processes which can be helpful for evaluating groundwater sustainability and vulnerability. Dissolved noble gas data have proven particularly useful in mountainous terrain because they can be used to determine recharge elevation. However, tracer-derived recharge elevations have not been utilized as calibration targets for numerical groundwater flow models. Herein, we constrain and calibrate a regional groundwater flow model with noble-gas-derived recharge elevations for the first time. Tritium and noble gas tracer results improved the site conceptual model by identifying a previously uncertain contribution of mountain block recharge from the Coast Mountains to an alluvial coastal aquifer in humid southwestern British Columbia. The revised conceptual model was integrated into a three-dimensional numerical groundwater flow model and calibrated to hydraulic head data in addition to recharge elevations estimated from noble gas recharge temperatures. Recharge elevations proved to be imperative for constraining hydraulic conductivity, recharge location, and bedrock geometry, and thus minimizing model nonuniqueness. Results indicate that 45% of recharge to the aquifer is mountain block recharge. A similar match between measured and modeled heads was achieved in a second numerical model that excludes the mountain block (no mountain block recharge), demonstrating that hydraulic head data alone are incapable of quantifying mountain block recharge. This result has significant implications for understanding and managing source water protection in recharge areas, potential effects of climate change, the overall water budget, and ultimately ensuring groundwater sustainability.
NASA Astrophysics Data System (ADS)
Elkadiri, R.; Sultan, M.; Nurmemet, I.; Al Harbi, H.; Youssef, A.; Elbayoumi, T.; Zabramwi, Y.; Alzahrani, S.; Bahamil, A.
2014-12-01
We developed methodologies that heavily rely on observations extracted from a wide-range of remote sensing data sets (TRMM, Landsat ETM, ENVISAT, ERS, SPOT, Orbview, GeoEye) to develop a warning system for rainfall-induced debris flows in the Jazan province in the Red Sea Hills. The developed warning system integrates static controlling factors and dynamic triggering factors. The algorithm couples a susceptibility map with a rainfall I-D curve, both are developed using readily available remote sensing datasets. The static susceptibility map was constructed as follows: (1) an inventory was compiled for debris flows identified from high spatial resolution datasets and field verified; (2) 10 topographical and land cover predisposing factors (i.e. slope angle, slope aspect, normalized difference vegetation index, topographical position index, stream power index, flow accumulation, distance to drainage line, soil weathering index, elevation and topographic wetness index) were generated; (3) an artificial neural network model (ANN) was constructed, optimized and validated; (4) a debris-flow susceptibility map was generated using the ANN model and refined (using differential backscatter coefficient radar images). The rainfall threshold curve was derived as follows: (1) a spatial database was generated to host temporal co-registered and radiometrically and atmospherically corrected Landsat images; (2) temporal change detection images were generated for pairs of successively acquired Landsat images and criteria were established to identify "the change" related to debris flows, (3) the duration and intensity of the precipitation event that caused each of the identified debris flow events was assumed to be that of the most intense event within the investigated period; and (4) the I-D curve was extracted using data (intensity and duration of precipitation) for the inventoried events. Our findings include: (1) the spatial controlling factors with the highest predictive power of
NASA Astrophysics Data System (ADS)
Wang, Jiajia; Ward, Steven N.; Xiao, Lili
2015-06-01
Flow-like landslides are rapidly moving fluid-solid mixtures that can cause significant destruction along paths that run far from their original sources. Existing models for run out prediction and motion simulation of flow-like landslides have many limitations. In this paper, we develop a new method named `Tsunami Squares' to simulate the generation, propagation and stoppage of flow-like landslides based on conservation of volume and momentum. Landslide materials in the new method form divisible squares that are displaced, then further fractured. The squares move under the influence of gravity-driven acceleration and suffer decelerations due to basal and dynamic frictions. Distinctively, this method takes into account solid and fluid mechanics, particle interactions and flow regime transitions. We apply this approach to simulate the 1982 El Picacho landslide in San Salvador, capital city of El Salvador. Landslide products from Tsunami Squares such as run out distance, velocities, erosion and deposition depths and impacted area agree well with field investigated and eyewitness data.
NASA Astrophysics Data System (ADS)
Goguitchaichvili, Avto; Caccavari, Ana; Calvo-Rathert, Manuel; Morales, Juan; Solano, Miguel Cervantes; Vashakidze, Goga; Huaiyu, He; Vegas, Néstor
2016-08-01
We report 28 successful Thellier type absolute geomagnetic paleointensity determinations from a Pleistocene lava sequence composed of 39 successive flows in the Djavakheti Highland (Lesser Caucasus, Georgia). Additionally, multispecimen technique provided the estimation of geomagnetic field strength for 12 independent cooling units. Paleointensity studies were performed using both Thellier type double heating and multispecimen techniques. Samples selection was mainly based on uni-vectorial remanent magnetization, thermal stability and domain size of the samples. Flow-mean Thellier paleointensity values range from 16.3 ± 5.2 to 71.0 ± 0.3 μT, while intensities obtained using multispecimen approach vary from17.2 ± 2.3 to 69.3 ± 7.9 μT. One of the flows is located near a possible discontinuity in the sequence and yields a rather low Thellier absolute intensity (16.3 ± 5.2) suggesting a transitional regime and the onset of the Matuyama-Olduvai polarity transition, which does not appear on the directional record. Multispecimen paleointensities from the same flow, however, yield higher, close to present day values which makes untenable the hypothesis of occurrence of transitional field. Thus the whole sequence was emplaced in a short time between the Olduvai chron and 1.73 ± 0.03 Ma, as suggested by available radiometric and paleomagnetic data (Caccavari et al., 2014).
NASA Astrophysics Data System (ADS)
Yoshikawa, Sayaka; Yanagawa, Aki; Iwasaki, Yuichi; Sui, Pengzhe; Koirala, Sujan; Khajuria, Anupam; Hirano, Kazunari; Mahendran, Roobavannan; Hirabayashi, Yukiko; Yoshimura, Chihiro; Kanae, Shinjiro
2014-05-01
Changes in river discharge due to human activities and climate change would affect the sustainability of freshwater ecosystems. To globally assess how changes in river discharge will affect the future status of freshwater ecosystems, global-scale hydrological simulations need to be connected with a model to estimate the durability of freshwater ecosystems. However, the development of this specific modelling combination for the global scale is still in its infancy. In this study, two statistical methods are introduced to link flow regimes to fish species richness (FSR): one is based on a linear relationship between FSR and mean river discharge (hereafter, FSR-MAD method), and the other is based on a multi-linear relationship between FSR and ecologically relevant flow indices involving several other flow characteristics and mean river discharge (FSR-FLVAR method). The FSR-MAD method has been used previously in global simulation studies. The FSR-FLVAR method is newly introduced here. These statistical methods for estimating FSR were combined with a set of state-of-art global river discharge simulations using latest outputs of 11 coupled atmosphere-ocean general circulation models to evaluate the potential impact of climate- change-induced flow alterations on FSR changes. Generally, future reductions in FSR with the FSR-FLVAR method are greater and much more scattered than those with the FSR-MAD method. In arid regions, both methods indicate reductions in FSR because mean discharge is projected to decrease in the future, although the magnitude of reductions in FSR is different between the two methods. In contrast, in heavy-snow regions a large reduction in FSR is shown by the FSR-FLVAR method due to increases in the frequency of low and high flows. Although we cannot determine only by this study which this prediction is more reliable, it can be argued that efforts to take plural ecologically relevant flow indices into account would lead to more appropriate methods for
Chung, H.K.
1981-01-01
The signal flow graph application to the analysis of multiphoton interactions has been developed in this study. It is shown that the Schroedinger equation for the multiphoton interactions can be represented as signal flow graphs in the semiclassical limit. A few examples are given to illustrate the construction, manipulation and application of the graphs. Also, the generation of temporally short far infrared pulses and their evolution in time and space have been examined experimentally and theoretically. It is shown that the far infrared pulsewidth can be as short as one-half the pump pulsewidth which is already shorter than the molecular relaxation times. In particular, the far infrared pulse energy is found to be scaled in z as e..sqrt..gz, contrary to the Beer's law growth, e/sup gz/.
Belwin Edward, J; Rajasekar, N; Sathiyasekar, K; Senthilnathan, N; Sarjila, R
2013-09-01
Obtaining optimal power flow solution is a strenuous task for any power system engineer. The inclusion of FACTS devices in the power system network adds to its complexity. The dual objective of OPF with fuel cost minimization along with FACTS device location for IEEE 30 bus is considered and solved using proposed Enhanced Bacterial Foraging algorithm (EBFA). The conventional Bacterial Foraging Algorithm (BFA) has the difficulty of optimal parameter selection. Hence, in this paper, BFA is enhanced by including Nelder-Mead (NM) algorithm for better performance. A MATLAB code for EBFA is developed and the problem of optimal power flow with inclusion of FACTS devices is solved. After several run with different initial values, it is found that the inclusion of FACTS devices such as SVC and TCSC in the network reduces the generation cost along with increased voltage stability limits. It is also observed that, the proposed algorithm requires lesser computational time compared to earlier proposed algorithms. PMID:23759251
NASA Astrophysics Data System (ADS)
Buono, Armand C.
The numerical method presented in this study attempts to predict the mean, non-uniform flow field upstream of a propeller partially immersed in a thick turbulent boundary layer with an actuator disk using CFD based on RANS in ANSYS FLUENT. Three different configurations, involving an infinitely thin actuator disk in the freestream (Configuration 1), an actuator disk near a wall with a turbulent boundary layer (Configuration 2), and an actuator disk with a hub near a wall with a turbulent boundary layer (Configuration 3), were analyzed for a variety of advance ratios ranging from J = 0.48 to J =1.44. CFD results are shown to be in agreement with previous works and validated with experimental data of reverse flow occurring within the boundary layer above the flat plate upstream of a rotor in the Virginia Tech's Stability Wind Tunnel facility. Results from Configuration 3 will be used in future aero-acoustic computations.
NASA Astrophysics Data System (ADS)
Jha, B. K.; Sani, I.
2015-02-01
This paper investigates the role of induced magnetic field on a transient natural convection flow of an electrically conducting, incompressible and viscous fluid in a vertical channel formed by two infinite vertical parallel plates. The transient flow formation inside the channel is due to sudden asymmetric heating of channel walls. The time dependent momentum, energy and magnetic induction equations are solved semi-analytically using the Laplace transform technique along with the Riemann-sum approximation method. The solutions obtained are validated by comparisons with the closed form solutions obtained for the steady states which have been derived separately and also by the implicit finite difference method. Graphical results for the temperature, velocity, induced magnetic field, current density, and skin-friction based on the semi-analytical solutions are presented and discussed.
NASA Astrophysics Data System (ADS)
Shao, Xuefeng; Li, Xiangdong; Wang, Rongshun
2016-04-01
An average bubble number density (ABND) model was formulated and numerically resolved for the subcooled flow boiling of liquid nitrogen. The effects of bubble coalescence and breakup were taken into account. Some new closure correlations describing bubble nucleation and departure on the heating surface were selected as well. For the purpose of comparison, flow boiling of liquid nitrogen was also numerically simulated using a modified two-fluid model. The results show that the simulations performed by using the ABND model achieve encouraging improvement in accuracy in predicting heat flux and wall temperature of a vertical tube. Moreover, the influence of the bubble coalescence and breakup is shown to be great on predicting overall pressure beyond the transition point.
Podichetty, Jagdeep T; Bhaskar, Prasana R; Singarapu, Kumar; Madihally, Sundararajan V
2015-02-01
In this study, the distribution of oxygen and glucose was evaluated along with consumption by hepatocytes using three different approaches. The methods include (i) Computational Fluid Dynamics (CFD) simulation, (ii) residence time distribution (RTD) analysis using a step-input coupled with segregation model or dispersion model, and (iii) experimentally determined consumption by HepG2 cells in an open-loop. Chitosan-gelatin (CG) scaffolds prepared by freeze-drying and polycaprolactone (PCL) scaffolds prepared by salt leaching technique were utilized for RTD analyses. The scaffold characteristics were used in CFD simulations i.e. Brinkman's equation for flow through porous medium, structural mechanics for fluid induced scaffold deformation, and advection-diffusion equation coupled with Michaelis-Menten rate equations for nutrient consumption. With the assumption that each hepatocyte behaves like a micro-batch reactor within the scaffold, segregation model was combined with RTD to determine exit concentration. A flow rate of 1 mL/min was used in the bioreactor seeded with 0.6 × 10(6) HepG2 cells/cm(3) on CG scaffolds and oxygen consumption was measured using two flow-through electrodes located at the inlet and outlet. Glucose in the spent growth medium was also analyzed. RTD results showed distribution of nutrients to depend on the surface characteristics of scaffolds. Comparisons of outlet oxygen concentrations between the simulation results, and experimental results showed good agreement with the dispersion model. Outlet oxygen concentrations from segregation model predictions were lower. Doubling the cell density showed a need for increasing the flow rate in CFD simulations. This integrated approach provide a useful strategy in designing bioreactors and monitoring tissue regeneration. PMID:25116006
Brountzos, Elias N. Ptohis, Nikolaos; Grammenou-Pomoni, Maria; Panagiotou, Irini; Kelekis, Dimitrios; Gouliamos, Athanasios Kelekis, Nikolaos
2009-05-15
We present a 28-year-old man with a large symptomatic arteriovenous fistula (AVF) treated with embolization using the Amplatzer vascular plug (AVP). Although embolization may be considered the first-line therapy in the treatment of AVFs, there is an inherent high risk of migration of the embolic agents into the venous and pulmonary circulations. This case is illustrative of the ease and safety of using this device in high-flow renal AVFs.
Pribush, A; Meiselman, H J; Meyerstein, D; Meyerstein, N
2000-01-01
A method based on dielectric properties of dispersed systems was applied to investigate the kinetics of RBC aggregation and the break-up of the aggregates. Experimentally, this method consists of measuring the capacitance at a frequency in the beginning of the beta-dispersion. Two experimental protocols were used to investigate the aggregation process. In the first case, blood samples were fully dispersed and then the flow was decreased or stopped to promote RBC aggregation. It was found that the initial phases of RBC aggregation are not affected by the shear rate. This finding indicates that RBC aggregation is a slow coagulation process. In the second case, RBCs aggregated under flow conditions at different shear rates and after the capacitance reached plateau levels, the flow was ceased. The steady-state capacitance of the quiescent blood and the kinetics of RBC aggregation after stoppage of shearing depend on the prior shear rate. To clarify the reasons for this effect, the kinetics of the disaggregation process was studied. In these experiments, time courses of the capacitance were recorded under different flow conditions and then a higher shear stress was applied to break up RBC aggregates. It was found that the kinetics of the disaggregation process depend on both the prior and current shear stresses. Results obtained in this study and their analysis show that the kinetics of RBC aggregation in stasis consists of two consecutive phases: At the onset, red blood cells interact face-to-face to form linear aggregates and then, after an accumulation of an appropriate concentration of these aggregates, branched rouleaux are formed via reactions of ends of the linear rouleaux with sides of other rouleaux (face-to-side interactions). Branching points are broken by low shear stresses whereas dispersion of the linear rouleaux requires significantly higher energy. PMID:11204548
NASA Astrophysics Data System (ADS)
Carrière, Simon D.; Chalikakis, Konstantinos; Danquigny, Charles; Davi, Hendrik; Mazzilli, Naomi; Ollivier, Chloé; Emblanch, Christophe
2016-05-01
Some portions of the porous rock matrix in the karst unsaturated zone (UZ) can contain large volumes of water and play a major role in water flow regulation. The essential results are presented of a local-scale study conducted in 2011 and 2012 above the Low Noise Underground Laboratory (LSBB - Laboratoire Souterrain à Bas Bruit) at Rustrel, southeastern France. Previous research revealed the geological structure and water-related features of the study site and illustrated the feasibility of specific hydrogeophysical measurements. In this study, the focus is on hydrodynamics at the seasonal and event timescales. Magnetic resonance sounding (MRS) measured a high water content (more than 10 %) in a large volume of rock. This large volume of water cannot be stored in fractures and conduits within the UZ. MRS was also used to measure the seasonal variation of water stored in the karst UZ. A process-based model was developed to simulate the effect of vegetation on groundwater recharge dynamics. In addition, electrical resistivity tomography (ERT) monitoring was used to assess preferential water pathways during a rain event. This study demonstrates the major influence of water flow within the porous rock matrix on the UZ hydrogeological functioning at both the local (LSBB) and regional (Fontaine de Vaucluse) scales. By taking into account the role of the porous matrix in water flow regulation, these findings may significantly improve karst groundwater hydrodynamic modelling, exploitation, and sustainable management.
NASA Astrophysics Data System (ADS)
Ovaysi, S.; Piri, M.
2009-12-01
We present a three-dimensional fully dynamic parallel particle-based model for direct pore-level simulation of incompressible viscous fluid flow in disordered porous media. The model was developed from scratch and is capable of simulating flow directly in three-dimensional high-resolution microtomography images of naturally occurring or man-made porous systems. It reads the images as input where the position of the solid walls are given. The entire medium, i.e., solid and fluid, is then discretized using particles. The model is based on Moving Particle Semi-implicit (MPS) technique. We modify this technique in order to improve its stability. The model handles highly irregular fluid-solid boundaries effectively. It takes into account viscous pressure drop in addition to the gravity forces. It conserves mass and can automatically detect any false connectivity with fluid particles in the neighboring pores and throats. It includes a sophisticated algorithm to automatically split and merge particles to maintain hydraulic connectivity of extremely narrow conduits. Furthermore, it uses novel methods to handle particle inconsistencies and open boundaries. To handle the computational load, we present a fully parallel version of the model that runs on distributed memory computer clusters and exhibits excellent scalability. The model is used to simulate unsteady-state flow problems under different conditions starting from straight noncircular capillary tubes with different cross-sectional shapes, i.e., circular/elliptical, square/rectangular and triangular cross-sections. We compare the predicted dimensionless hydraulic conductances with the data available in the literature and observe an excellent agreement. We then test the scalability of our parallel model with two samples of an artificial sandstone, samples A and B, with different volumes and different distributions (non-uniform and uniform) of solid particles among the processors. An excellent linear scalability is
NASA Astrophysics Data System (ADS)
Lods, Gerard; Gouze, Philippe
2004-11-01
The identification of the hydraulic characteristics and transport properties of fractured reservoirs requires the development of specific models that account for (i) the medium heterogeneity, e.g. the presence of major conductive fractures that delimit capacitive matrix blocks, with weakly open, dead end or isolated fractures , and (ii) for the geometrical arrangement of the major conductive fractures network, which dominates the flow at the scale of the well tests. Well Tests in Fractured Media (WTFM) software takes into account these two main features by combining radial flow generalized to fractional dimension, with the theory of double-porosity, including diffusivity in the second porosity, transient inter-porosity flow and inter-porosity skin effect, and with leakance. The implementation of this nD model, with n fractional, extends usefully the domain of application of the usual 1D/2D/3D double-porosity/leakance models for a large range of connection levels of fracture networks. Although the fractures geometry and properties are not considered one by one, or by directional families, they are taken into account by averaged properties and by the impact that the whole network has on the hydrodynamic behaviour. The accuracy of the coupled transient behaviours analysis is augmented by taking into account wellbore storage and skin effects. All together, the use of these different options allows matching a wide range of pumping test curves, characteristics of distinctive behaviours, with a limited number of parameters. Distinctive well test experiments, in both sedimentary and crystalline rocks, are presented for enlightening how the pertinent use of the model options improves predictions.
NASA Astrophysics Data System (ADS)
Pribulick, C. E.; Maxwell, R. M.; Williams, K. H.; Carroll, R. W. H.
2014-12-01
Prediction of environmental response to global climate change is paramount for regions that rely upon snowpack for their dominant water supply. Temperature increases are anticipated to be greater at higher elevations perturbing hydrologic systems that provide water to millions of downstream users. In this study, the relationships between large-scale climatic change and the corresponding small-scale hydrologic processes of mountainous terrain are investigated in the East River headwaters catchment near Gothic, CO. This catchment is emblematic of many others within the upper Colorado River Basin and covers an area of 250 square kilometers, has a topographic relief of 1420 meters, an average elevation of 3266 meters and has varying stream characteristics. This site allows for the examination of the varying effect of climate-induced changes on the hydrologic response of three different characteristic components of the catchment: a steep high-energy mountain system, a medium-grade lower-energy system and a low-grade low-energy meandering floodplain. To capture the surface and subsurface heterogeneity of this headwaters system the basin has been modeled at a 10-meter resolution using ParFlow, a parallel, integrated hydrologic model. Driven by meteorological forcing, ParFlow is able to capture land surface processes and represents surface and subsurface interactions through saturated and variably saturated heterogeneous flow. Data from Digital Elevation Models (DEMs), land cover, permeability, geologic and soil maps, and on-site meteorological stations, were prepared, analyzed and input into ParFlow as layers with a grid size comprised of 1403 by 1685 cells to best represent the small-scale, high resolution model domain. Water table depth, soil moisture, soil temperature, snowpack, runoff and local energy budget values provide useful insight into the catchments response to the Intergovernmental Panel on Climate Change (IPCC) temperature projections. In the near term
NASA Astrophysics Data System (ADS)
Mitchell, N. A.; Gran, K. B.; Cho, S. J.; Dalzell, B. J.; Kumarasamy, K.
2015-12-01
A combination of factors including climate change, land clearing, and artificial drainage have increased many agricultural regions' stream flows and rates at which channel banks and bluffs are eroded. Increasing erosion rates within the Minnesota River Basin have contributed to higher sediment-loading rates, excess turbidity levels, and increases in sedimentation rates in Lake Pepin further downstream. Water storage sites (e.g., wetlands) have been discussed as a means to address these issues. This study uses the Soil and Water Assessment Tool (SWAT) to assess a range of water retention site (WRS) implementation scenarios in the Le Sueur watershed in south-central Minnesota, a subwatershed of the Minnesota River Basin. Sediment loading from bluffs was assessed through an empirical relationship developed from gauging data. Sites were delineated as topographic depressions with specific land uses, minimum areas (3000 m2), and high compound topographic index values. Contributing areas for the WRS were manually measured and used with different site characteristics to create 210 initial WRS scenarios. A generalized relationship between WRS area and contributing area was identified from measurements, and this relationship was used with different site characteristics (e.g., depth, hydraulic conductivity (K), and placement) to create 225 generalized WRS scenarios. Reductions in peak flow volumes and sediment-loading rates are generally maximized by placing site with high K values in the upper half of the watershed. High K values allow sites to lose more water through seepage, emptying their storages between precipitation events and preventing frequent overflowing. Reductions in peak flow volumes and sediment-loading rates also level off at high WRS extents due to the decreasing frequencies of high-magnitude events. The generalized WRS scenarios were also used to create a simplified empirical model capable of generating peak flows and sediment-loading rates from near
NASA Astrophysics Data System (ADS)
Hu, Mengsu; Wang, Yuan; Rutqvist, Jonny
2015-06-01
One major challenge in modeling groundwater flow within heterogeneous geological media is that of modeling arbitrarily oriented or intersected boundaries and inner material interfaces. The Numerical Manifold Method (NMM) has recently emerged as a promising method for such modeling, in its ability to handle boundaries, its flexibility in constructing physical cover functions (continuous or with gradient jump), its meshing efficiency with a fixed mathematical mesh (covers), its convenience for enhancing approximation precision, and its integration precision, achieved by simplex integration. In this paper, we report on developing and comparing two new approaches for boundary constraints using the NMM, namely a continuous approach with jump functions and a discontinuous approach with Lagrange multipliers. In the discontinuous Lagrange multiplier method (LMM), the material interfaces are regarded as discontinuities which divide mathematical covers into different physical covers. We define and derive stringent forms of Lagrange multipliers to link the divided physical covers, thus satisfying the continuity requirement of the refraction law. In the continuous Jump Function Method (JFM), the material interfaces are regarded as inner interfaces contained within physical covers. We briefly define jump terms to represent the discontinuity of the head gradient across an interface to satisfy the refraction law. We then make a theoretical comparison between the two approaches in terms of global degrees of freedom, treatment of multiple material interfaces, treatment of small area, treatment of moving interfaces, the feasibility of coupling with mechanical analysis and applicability to other numerical methods. The newly derived boundary-constraint approaches are coded into a NMM model for groundwater flow analysis, and tested for precision and efficiency on different simulation examples. We first test the LMM for a Dirichlet boundary and then test both LMM and JFM for an
Zhang, Keni; Moridis, G.J.; Wu, Y.-S.; Pruess, K.
2008-07-01
Simulation of the system behavior of hydrate-bearing geologic media involves solving fully coupled mass- and heat-balance equations. In this study, we develop a domain decomposition approach for large-scale gas hydrate simulations with coarse-granularity parallel computation. This approach partitions a simulation domain into small subdomains. The full model domain, consisting of discrete subdomains, is still simulated simultaneously by using multiple processes/processors. Each processor is dedicated to following tasks of the partitioned subdomain: updating thermophysical properties, assembling mass- and energy-balance equations, solving linear equation systems, and performing various other local computations. The linearized equation systems are solved in parallel with a parallel linear solver, using an efficient interprocess communication scheme. This new domain decomposition approach has been implemented into the TOUGH+HYDRATE code and has demonstrated excellent speedup and good scalability. In this paper, we will demonstrate applications for the new approach in simulating field-scale models for gas production from gas-hydrate deposits.
ERIC Educational Resources Information Center
Flynn, Alison B.; Ogilvie, William W.
2015-01-01
A significant redesign of the introductory organic chemistry curriculum at the authors' institution is described. There are two aspects that differ greatly from a typical functional group approach. First, organic reaction mechanisms and the electron-pushing formalism are taught before students have learned a single reaction. The conservation of…
Haro, A.; Castro-Santos, T.; Noreika, J.; Odeh, M.
2004-01-01
The ability to traverse barriers of high-velocity flow limits the distributions of many diadromous and other migratory fish species, yet very few data exist that quantify this ability. We provide a detailed analysis of sprint swimming ability of six migratory fish species (American shad (Alosa sapidissima), alewife (Alosa pseudoharengus), blueback herring (Alosa aestivalis), striped bass (Morone saxatilis), walleye (Stizostedion vitreum), and white sucker (Catostomus commersoni)) against controlled water velocities of 1.5-4.5 m??s-1 in a large, open-channel flume. Performance was strictly voluntary: no coercive incentives were used to motivate fish to sprint. We used these data to generate models of maximum distance traversed, taking into account effects of flow velocity, body length, and temperature. Although the maximum distance traversed decreased with increasing velocity, the magnitude of this effect varied among species. Other covariate effects were likewise variable, with divergent effects of temperature and nonuniform length effects. These effects do not account for all of the variability in performance, however, and behavioral traits may account for observed interspecific differences. We propose the models be used to develop criteria for fish passage structures, culverts, and breached dams.
Sánchez-López, V; Fernández-Romero, J M; Gómez-Hens, A
2009-07-10
A method for the evaluation of liposome size populations using sucrose density gradient centrifugation coupled with a continuous flow system is presented. Liposomes, prepared using different methods (rapid solvent evaporation, rehydration, and detergent removal) and modified by assaying several procedures (shaking, sonication and extrusion) were evaluated according to the type of liposome, size and polydispersity. The preparation of liposomes was carried out in the presence of the fluorophor cresyl violet. Extracts of the liposomes were homogenised and centrifuged at 20,073 x g at 4 degrees C for 30 min using sucrose density gradient centrifugation programmes, which provide efficient liposome separation in different sizes. The results of the separation procedure were tested by aspiration of the extracts into a continuous flow system in which the liposomes were disrupted by the continuous mixing with a Triton X-100 solution, prior to their translation to the detector. The luminescence provided by the liberation of the encapsulated fluorophor indicates the distribution of liposomes in each density gradient stage. Three zones were obtained: zone alpha, containing giant unilamellar and multivesicular vesicles, zone beta, with large and medium size liposomes, and zone gamma, which contained small size liposomes. The precision of the separation zones obtained, expressed as RSD%, was lower than 5.6% in all instances. The method provides a relative rapid way to evaluate the liposome polydispersity and size after using conventional methods of synthesis and mechanical modifications. PMID:19481634
Lim, Lam Ghai; Pao, William K. S.; Hamid, Nor Hisham; Tang, Tong Boon
2016-01-01
A 360° twisted helical capacitance sensor was developed for holdup measurement in horizontal two-phase stratified flow. Instead of suppressing nonlinear response, the sensor was optimized in such a way that a ‘sine-like’ function was displayed on top of the linear function. This concept of design had been implemented and verified in both software and hardware. A good agreement was achieved between the finite element model of proposed design and the approximation model (pure sinusoidal function), with a maximum difference of ±1.2%. In addition, the design parameters of the sensor were analysed and investigated. It was found that the error in symmetry of the sinusoidal function could be minimized by adjusting the pitch of helix. The experiments of air-water and oil-water stratified flows were carried out and validated the sinusoidal relationship with a maximum difference of ±1.2% and ±1.3% for the range of water holdup from 0.15 to 0.85. The proposed design concept therefore may pose a promising alternative for the optimization of capacitance sensor design. PMID:27384567
NASA Astrophysics Data System (ADS)
Hartley, Lee; Joyce, Steven
2013-09-01
The Swedish Nuclear Fuel and Waste Management Company (SKB) has in 2011 finalized a safety assessment project, SR-Site, with the objective to assess the long term safety of a final repository for spent nuclear fuel at Forsmark in Northern Uppland of Sweden. Prior to the safety assessment, comprehensive site investigations were conducted at the Forsmark site to build understanding and characterize the site. An essential part of the site investigations were to describe hydrological properties and characteristics of the site and use this to assess the groundwater pathway. The geological structural context of the crystalline bedrock at Forsmark implied a fracture network concept was the natural description for interpreting site data and assessing the groundwater pathway. Of primary importance to the description of the fracture system was the assignment of down-borehole flow-logging measurements to individual fractures identified by imaging techniques, providing the basis to relate hydrogeological characteristics such as anisotropy and heterogeneity to the geological structural framework. Also, the key input quantities to the assessment of long-term safety can be closely related to the derived fracture flow-rate distributions. Key success factors for this project were to develop and test strategies for modeling methodologies, as described in this paper, from an early stage, hand-in-hand with the planning and phased acquisition of site data as well as successive safety assessments.
Soliz, J G; Acebo, H L
2001-01-01
The aim of this study is to apply a parsimonious hydrologic model to the Itxina karstic aquifer that can predict changes in discharge resulting from variable inputs (recharge). The Itxina Aquifer was divided into four cells corresponding to different recharge areas. Each cell was treated as a tank to characterize the conditions within the cell. In the model, when the reservoir boundaries coincide with the position of the siphons, the signal simulated is sensitive to input pulses of the recharge. This supports the hypothesis that the siphons are the controlling mechanism in the flow system of the aquifer. The good agreement between predicted and measured discharges demonstrates the ability of the model to simulate the flow in the Itxina Aquifer. These results demonstrated that the hydraulic conductivity increases downstream within the aquifer. The hydraulic conductivities obtained by calibration varied between 4.2 x 10(-3) m/s upstream of the aquifer, 6.0 x 10(-2) m/s in the central region, and 9.5 x 10(-1) m/s in the lower region of the aquifer. These values seem reasonable because the underground features in the principal caves show that the density of caves increases downstream in the Itxina Aquifer. The simple representation of the system produced results comparable to traditional ground water models with fewer data requirements and calibration parameters. PMID:11340998
Lim, Lam Ghai; Pao, William K S; Hamid, Nor Hisham; Tang, Tong Boon
2016-01-01
A 360° twisted helical capacitance sensor was developed for holdup measurement in horizontal two-phase stratified flow. Instead of suppressing nonlinear response, the sensor was optimized in such a way that a 'sine-like' function was displayed on top of the linear function. This concept of design had been implemented and verified in both software and hardware. A good agreement was achieved between the finite element model of proposed design and the approximation model (pure sinusoidal function), with a maximum difference of ±1.2%. In addition, the design parameters of the sensor were analysed and investigated. It was found that the error in symmetry of the sinusoidal function could be minimized by adjusting the pitch of helix. The experiments of air-water and oil-water stratified flows were carried out and validated the sinusoidal relationship with a maximum difference of ±1.2% and ±1.3% for the range of water holdup from 0.15 to 0.85. The proposed design concept therefore may pose a promising alternative for the optimization of capacitance sensor design. PMID:27384567
NASA Astrophysics Data System (ADS)
Kulikov, Igor; Vorobyov, Eduard
2016-07-01
An approach for constructing a low-dissipation numerical method is described. The method is based on a combination of the operator-splitting method, Godunov method, and piecewise-parabolic method on the local stencil. Numerical method was tested on a standard suite of hydrodynamic test problems. In addition, the performance of the method is demonstrated on a global test problem showing the development of a spiral structure in a gravitationally unstable gaseous galactic disk.
NASA Astrophysics Data System (ADS)
Alireza Shirvanian, Pezhman; Calo, Joseph M.
2002-08-01
The application of a continuum (Eulerian) formulation to modeling a spouted bed electrolytic reactor (SBER), requires appropriate boundary conditions at the conical bottom cathode where the bed particles are transported back to the draft tube for re-entrainment. A kinetic theory approach, including rolling resistance, particle collisions, and friction between particles and with the inclined surface, was used to address this problem. The resultant formulation is cast into appropriate boundary conditions for the continuum model.
NASA Astrophysics Data System (ADS)
Amjad, Hussain; Syed Tauseef, Mohyud-Din; Taqi, Ahmed Cheema
2012-11-01
Analytic and numerical techniques are presented to analyze the influence of temperature and wall slip conditions on the unsteady flow and heat transfer via viscous fluid squeezed between two parallel disks in the presence of an applied magnetic field. The governing partial differential equations for momentum and heat transfer are reduced to a system of coupled nonlinear ordinary differential equations using similarity transformations. The homotopy analysis method (HAM) is then utilized to find explicit series solution of the resulting problem. The convergence of the obtained solution is carefully analyzed. To check the reliability of the method the same problem is also solved by using the shooting method and an excellent agreement is observed between the two sets of results. Influence of various parameters of practical importance on the velocity and temperature profiles is studied and portrayed graphically. Values of skin friction coefficient and local Nusselt number are tabulated by assigning different values to various emerging parameters.
NASA Astrophysics Data System (ADS)
Ghasemi, Seiyed E.; Hatami, M.; Hatami, J.; Sahebi, S. A. R.; Ganji, D. D.
2016-02-01
In this paper, flow analysis for a non-Newtonian third grade blood in coronary and femoral arteries is simulated numerically. Blood is considered as the third grade non-Newtonian fluid under periodic body acceleration motion and pulsatile pressure gradient. Differential Quadrature Method (DQM) and Crank Nicholson Method (CNM) are used to solve the Partial Differential Equation (PDE) governing equation by which a good agreement between them was observed in the results. The influences of some physical parameters such as amplitude, lead angle and body acceleration frequency on non-dimensional velocity and profiles are considered. For instance, the results show that increasing the amplitude, Ag, and reducing the lead angle of body acceleration, ϕ, make higher velocity profiles in the center line of both arteries.
NASA Astrophysics Data System (ADS)
Hasan, Raisul
2016-07-01
In this research paper firstly theoretical analysis and design of the porous matrix for filtration and selection of associated liquid (highly viscous and low viscous liquid) is carried out. Hence, porosity of the bed has been found out followed by a detailed CFD analysis of the flow to identify displacement structure (fingering: due to the nonlinear interactions among viscous, capillary and gravitational forces). Moreover, an experiment will be with synthetic porous medium consists of a single layer of glass beads which are then positioned homogeneously or non-homogeneously between two Perspex sheets and then fluid displacement structure/fingering will be photographed. Then the effort will be made to validate results with the experiment based photograph and then the CFD model will be extended to microgravity condition KEYWORDS: CFD, Fingering, microgravity, Non-homogeneously, Capillary .
Gallis, Michael A; Bond, Ryan B; Torczynski, John R
2009-09-28
Recently proposed molecular-level chemistry models that predict equilibrium and nonequilibrium reaction rates using only kinetic theory and fundamental molecular properties (i.e., no macroscopic reaction-rate information) are investigated for chemical reactions occurring in upper-atmosphere hypersonic flows. The new models are in good agreement with the measured Arrhenius rates for near-equilibrium conditions and with both measured rates and other theoretical models for far-from-equilibrium conditions. Additionally, the new models are applied to representative combustion and ionization reactions and are in good agreement with available measurements and theoretical models. Thus, molecular-level chemistry modeling provides an accurate method for predicting equilibrium and nonequilibrium chemical-reaction rates in gases. PMID:19791885
A kinetic-theory approach for computing chemical-reaction rates in upper-atmosphere hypersonic flows
NASA Astrophysics Data System (ADS)
Gallis, Michael A.; Bond, Ryan B.; Torczynski, John R.
2009-09-01
Recently proposed molecular-level chemistry models that predict equilibrium and nonequilibrium reaction rates using only kinetic theory and fundamental molecular properties (i.e., no macroscopic reaction-rate information) are investigated for chemical reactions occurring in upper-atmosphere hypersonic flows. The new models are in good agreement with the measured Arrhenius rates for near-equilibrium conditions and with both measured rates and other theoretical models for far-from-equilibrium conditions. Additionally, the new models are applied to representative combustion and ionization reactions and are in good agreement with available measurements and theoretical models. Thus, molecular-level chemistry modeling provides an accurate method for predicting equilibrium and nonequilibrium chemical-reaction rates in gases.
NASA Astrophysics Data System (ADS)
Pai, H.; Sivakumaran, K.; Villamizar, S. R.; Flanagan, J.; Guo, Q.; Harmon, T. C.
2013-12-01
Balancing ecosystem health in water-scarce, agriculturally dominated river basins remains a challenge. In dry water years, maintaining conditions for restored and sustained indigenous fish populations (a frequently used indicator for ecosystem health) is particularly challenging. Competing human demands include urban and agricultural water supplies, hydropower, and flood control. In many semi-arid regions, increasing drought intensity and frequency under future climate scenarios will combine with population increases to water scarcity. The goal of this work is to better understand how reservoir releases affect fish habitat and overall river aquatic ecosystem quality. Models integrating a diverse array of physical and biological processes and system state are used to forecast the river ecosystem response to changing drivers. We propose a distributed parameter-based Habitat Suitability Index (HSI) approach for assessing fish habitat quality. Our river ecosystem HSI maps are based on a combination of the following: (1) In situ data describing stream flow and water quality conditions; (2) Spatial observations, including surveyed cross-sections, aerial imagery and digital elevation maps (DEM) of the river and its riparian corridor; and (3) Simulated spatially distributed water depths, flow velocities, and temperatures estimated from 1D and 2D river flow and temperature models (HEC-RAS and CE-QUAL-W2, respectively). With respect to (2), image processing schemes are used to classify and map key habitat features, namely riparian edge and shallow underwater vegetation. HSI maps can be modified temporally to address specific life cycle requirements of indicator fish species. Results are presented for several reaches associated with the San Joaquin River Restoration Project, focusing on several components of the Chinook salmon life cycle. HSI maps and interpretations are presented in the context of a range of prescribed reservoir release hydrographs linked to California water
Neset, Tina-Simone Schmid; Singer, Heinz; Longrée, Philipp; Bader, Hans-Peter; Scheidegger, Ruth; Wittmer, Anita; Andersson, Jafet Clas Martin
2010-07-15
This paper explores the potential of combining substance-flow modelling with water and wastewater sampling to trace consumption-related substances emitted through the urban wastewater. The method is exemplified on sucralose. Sucralose is a chemical sweetener that is 600 times sweeter than sucrose and has been on the European market since 2004. As a food additive, sucralose has recently increased in usage in a number of foods, such as soft drinks, dairy products, candy and several dietary products. In a field campaign, sucralose concentrations were measured in the inflow and outflow of the local wastewater treatment plant in Linköping, Sweden, as well as upstream and downstream of the receiving stream and in Lake Roxen. This allows the loads emitted from the city to be estimated. A method consisting of solid-phase extraction followed by liquid chromatography and high resolution mass spectrometry was used to quantify the sucralose in the collected surface and wastewater samples. To identify and quantify the sucralose sources, a consumption analysis of households including small business enterprises was conducted as well as an estimation of the emissions from the local food industry. The application of a simple model including uncertainty and sensitivity analysis indicates that at present not one large source but rather several small sources contribute to the load coming from households, small business enterprises and industry. This is in contrast to the consumption pattern seen two years earlier, which was dominated by one product. The inflow to the wastewater treatment plant decreased significantly from other measurements made two years earlier. The study shows that the combination of substance-flow modelling with the analysis of the loads to the receiving waters helps us to understand consumption-related emissions. PMID:20447681
Wei, Hua-Liang; Zheng, Ying; Pan, Yi; Coca, Daniel; Li, Liang-Min; Mayhew, J E W; Billings, Stephen A
2009-06-01
It is well known that there is a dynamic relationship between cerebral blood flow (CBF) and cerebral blood volume (CBV). With increasing applications of functional MRI, where the blood oxygen-level-dependent signals are recorded, the understanding and accurate modeling of the hemodynamic relationship between CBF and CBV becomes increasingly important. This study presents an empirical and data-based modeling framework for model identification from CBF and CBV experimental data. It is shown that the relationship between the changes in CBF and CBV can be described using a parsimonious autoregressive with exogenous input model structure. It is observed that neither the ordinary least-squares (LS) method nor the classical total least-squares (TLS) method can produce accurate estimates from the original noisy CBF and CBV data. A regularized total least-squares (RTLS) method is thus introduced and extended to solve such an error-in-the-variables problem. Quantitative results show that the RTLS method works very well on the noisy CBF and CBV data. Finally, a combination of RTLS with a filtering method can lead to a parsimonious but very effective model that can characterize the relationship between the changes in CBF and CBV. PMID:19174333
NASA Astrophysics Data System (ADS)
Fan, Y.; Collet, M.; Ichchou, M.; Li, L.; Bareille, O.; Dimitrijevic, Z.
2016-01-01
This paper presents a rapid and accurate numerical tool for the energy flow evaluation in a periodic substructure from the near-field to the far-field domain. Here we suppose that the near-field part contains a point source characterized by the injected power in the structure. The near-field part is then modeled by Finite Element Method (FEM) while the periodic structure and the far-field part are regarded as waveguides and modeled by an enhanced Wave and Finite Element Method (WFEM). Enhancements are made on the eigenvalue scheme, the condensation of the unit cell and the consideration of a reduced wave basis. Efforts are made to adapt substructures modeled by different strategies in a multi-scale manner such that the final matrices dimensions of the built-up structure are largely reduced. The method is then validated numerically and theoretically. An application is presented, where a structural dynamical system coupled with periodic resistive piezoelectric shunts is discussed.
Langemann, Timo; Mayr, Ulrike Beate; Meitz, Andrea; Lubitz, Werner; Herwig, Christoph
2016-01-01
Flow cytometry (FCM) is a tool for the analysis of single-cell properties in a cell suspension. In this contribution, we present an improved FCM method for the assessment of E-lysis in Enterobacteriaceae. The result of the E-lysis process is empty bacterial envelopes-called bacterial ghosts (BGs)-that constitute potential products in the pharmaceutical field. BGs have reduced light scattering properties when compared with intact cells. In combination with viability information obtained from staining samples with the membrane potential-sensitive fluorescent dye bis-(1,3-dibutylarbituric acid) trimethine oxonol (DiBAC4(3)), the presented method allows to differentiate between populations of viable cells, dead cells, and BGs. Using a second fluorescent dye RH414 as a membrane marker, non-cellular background was excluded from the data which greatly improved the quality of the results. Using true volumetric absolute counting, the FCM data correlated well with cell count data obtained from colony-forming units (CFU) for viable populations. Applicability of the method to several Enterobacteriaceae (different Escherichia coli strains, Salmonella typhimurium, Shigella flexneri 2a) could be shown. The method was validated as a resilient process analytical technology (PAT) tool for the assessment of E-lysis and for particle counting during 20-l batch processes for the production of Escherichia coli Nissle 1917 BGs. PMID:26521248
NASA Astrophysics Data System (ADS)
Terashima, Hiroshi; Kawai, Soshi; Koshi, Mitsuo
2011-11-01
We present a formulation for high-order simulations of compressible multicomponent flows using a sixth-order compact differencing scheme and a localized artificial diffusivity. The formulation is designed to satisfy both of pressure and temperature equilibriums at fluid interfaces by introducing additional two equations to the Euler equations. In order to deal with sharp initial condition of density, a localized artificial diffusivity term is introduced to the mass conservation equation. Several one-dimensional problems such as advection of contact and material interfaces and a shock tube problems demonstrate that the present method maintains the pressure and temperature equilibriums and also satisfies the mass conservation property. The localized artificial diffusivity for the mass conservation equation enables to start computations even with severe one-point jump condition, effectively reducing numerical wiggles at the fluid interfaces. Comparisons with a conventional full conservative formulation present the superiority of the present method for preventing spurious pressure/velocity/temperature oscillations at the fluid interfaces. Two-dimensional problems such as the Richtmyer-Meshkov instability demonstrate its multidimensional applicability.
Asgher, Muhammad; Yaqoob, Mohammad; Nabi, Abdul; Siddiqi, Abdul Rauf
2014-01-01
Rose Bengal photosensitized flow injection chemiluminescence method is reported using luminol-Cu(II) for the determination of vitamins A and C in pharmaceutical formulations. The reaction is based on the enhancement effect of analyte in the production of anion radicals of Rose Bengal (RB•−) which rapidly interact with dissolved oxygen and generate superoxide anions radicals (O2•−) and hydrogen peroxide (H2O2). Highly reactive hydroxyl radicals (•OH) were produced via dismutation of H2O2 by catalyst (Cu2+). The generated superoxide anions radicals and hydroxyl radicals thus oxidize luminol in alkaline medium to generate strong chemiluminescence. The limit of detection (3s of the blank, n = 6) of vitamins A and C and RB was found to be 0.008, 0.005, and 0.05 μg mL−1, respectively. The sample throughput of 70 h−1 for vitamins A and C and 30 h−1 for RB was found. Calibration curve was linear in the range of 0.05–15, 0.01–20, and 0.1–50 μg mL−1 for vitamins A and C and RB, respectively, with relative standard deviations (RSDs; n = 3) in the range 1.6–3.6%. The method was successfully applied to pharmaceutical formulations and the results obtained were in good agreement with the labeled values. PMID:25614739
NASA Astrophysics Data System (ADS)
Bashtani, Farzad; Maini, Brij; Kantzas, Apostolos
2016-08-01
3D random networks are constructed in order to represent the tight Mesaverde formation which is located in north Wyoming, USA. The porous-space is represented by pore bodies of different shapes and sizes which are connected to each other by pore throats of varying length and diameter. Pore bodies are randomly distributed in space and their connectivity varies based on the connectivity number distribution which is used in order to generate the network. Network representations are then validated using publicly available mercury porosimetry experiments. The network modeling software solves the fundamental equations of two-phase immiscible flow incorporating wettability and contact angle variability. Quasi-static displacement is assumed. Single phase macroscopic properties (porosity, permeability) are calculated and whenever possible are compared to experimental data. Using this information drainage and imbibition capillary pressure, and relative permeability curves are predicted and (whenever possible) compared to experimental data. The calculated information is grouped and compared to available literature information on typical behavior of tight formations. Capillary pressure curve for primary drainage process is predicted and compared to experimental mercury porosimetry in order to validate the virtual porous media by history matching. Relative permeability curves are also calculated and presented.