Science.gov

Sample records for dynamic material flow

  1. Dynamic modelling of packaging material flow systems.

    PubMed

    Tsiliyannis, Christos A

    2005-04-01

    A dynamic model has been developed for reused and recycled packaging material flows. It allows a rigorous description of the flows and stocks during the transition to new targets imposed by legislation, product demand variations or even by variations in consumer discard behaviour. Given the annual reuse and recycle frequency and packaging lifetime, the model determines all packaging flows (e.g., consumption and reuse) and variables through which environmental policy is formulated, such as recycling, waste and reuse rates and it identifies the minimum number of variables to be surveyed for complete packaging flow monitoring. Simulation of the transition to the new flow conditions is given for flows of packaging materials in Greece, based on 1995--1998 field inventory and statistical data.

  2. Dynamic material flow modeling: an effort to calibrate and validate aluminum stocks and flows in Austria.

    PubMed

    Buchner, Hanno; Laner, David; Rechberger, Helmut; Fellner, Johann

    2015-05-05

    A calibrated and validated dynamic material flow model of Austrian aluminum (Al) stocks and flows between 1964 and 2012 was developed. Calibration and extensive plausibility testing was performed to illustrate how the quality of dynamic material flow analysis can be improved on the basis of the consideration of independent bottom-up estimates. According to the model, total Austrian in-use Al stocks reached a level of 360 kg/capita in 2012, with buildings (45%) and transport applications (32%) being the major in-use stocks. Old scrap generation (including export of end-of-life vehicles) amounted to 12.5 kg/capita in 2012, still being on the increase, while Al final demand has remained rather constant at around 25 kg/capita in the past few years. The application of global sensitivity analysis showed that only small parts of the total variance of old scrap generation could be explained by the variation of single parameters, emphasizing the need for comprehensive sensitivity analysis tools accounting for interaction between parameters and time-delay effects in dynamic material flow models. Overall, it was possible to generate a detailed understanding of the evolution of Al stocks and flows in Austria, including plausibility evaluations of the results. Such models constitute a reliable basis for evaluating future recycling potentials, in particular with respect to application-specific qualities of current and future national Al scrap generation and utilization.

  3. Modeling metal stocks and flows: a review of dynamic material flow analysis methods.

    PubMed

    Müller, Esther; Hilty, Lorenz M; Widmer, Rolf; Schluep, Mathias; Faulstich, Martin

    2014-02-18

    Dynamic material flow analysis (MFA) is a frequently used method to assess past, present, and future stocks and flows of metals in the anthroposphere. Over the past fifteen years, dynamic MFA has contributed to increased knowledge about the quantities, qualities, and locations of metal-containing goods. This article presents a literature review of the methodologies applied in 60 dynamic MFAs of metals. The review is based on a standardized model description format, the ODD (overview, design concepts, details) protocol. We focus on giving a comprehensive overview of modeling approaches and structure them according to essential aspects, such as their treatment of material dissipation, spatial dimension of flows, or data uncertainty. The reviewed literature features similar basic modeling principles but very diverse extrapolation methods. Basic principles include the calculation of outflows of the in-use stock based on inflow or stock data and a lifetime distribution function. For extrapolating stocks and flows, authors apply constant, linear, exponential, and logistic models or approaches based on socioeconomic variables, such as regression models or the intensity-of-use hypothesis. The consideration and treatment of further aspects, such as dissipation, spatial distribution, and data uncertainty, vary significantly and highly depends on the objectives of each study.

  4. Material Cycles and Chemicals: Dynamic Material Flow Analysis of Contaminants in Paper Recycling.

    PubMed

    Pivnenko, Kostyantyn; Laner, David; Astrup, Thomas F

    2016-11-15

    This study provides a systematic approach for assessment of contaminants in materials for recycling. Paper recycling is used as an illustrative example. Three selected chemicals, bisphenol A (BPA), diethylhexyl phthalate (DEHP) and mineral oil hydrocarbons (MOHs), are evaluated within the paper cycle. The approach combines static material flow analysis (MFA) with dynamic material and substance flow modeling. The results indicate that phasing out of chemicals is the most effective measure for reducing chemical contamination. However, this scenario was also associated with a considerable lag phase (between approximately one and three decades) before the presence of chemicals in paper products could be considered insignificant. While improved decontamination may appear to be an effective way of minimizing chemicals in products, this may also result in lower production yields. Optimized waste material source-segregation and collection was the least effective strategy for reducing chemical contamination, if the overall recycling rates should be maintained at the current level (approximately 70% for Europe). The study provides a consistent approach for evaluating contaminant levels in material cycles. The results clearly indicate that mass-based recycling targets are not sufficient to ensure high quality material recycling.

  5. Simulant-material experimental investigation of flow dynamics in the CRBR Upper-Core Structure

    SciTech Connect

    Wilhelm, D.; Starkovich, V.S.; Chapyak, E.J.

    1982-09-01

    The results of a simulant-material experimental investigation of flow dynamics in the Clinch River Breeder Reactor (CRBR) Upper Core Structure are described. The methodology used to design the experimental apparatus and select test conditions is detailed. Numerous comparisons between experimental data and SIMMER-II Code calculations are presented with both advantages and limitations of the SIMMER modeling features identified.

  6. Towards a dynamic assessment of raw materials criticality: linking agent-based demand--with material flow supply modelling approaches.

    PubMed

    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. Copyright © 2013 Elsevier B.V. All rights reserved.

  7. Dynamic analysis of global copper flows. Global stocks, postconsumer material flows, recycling indicators, and uncertainty evaluation.

    PubMed

    Glöser, Simon; Soulier, Marcel; Tercero Espinoza, Luis A

    2013-06-18

    We present a dynamic model of global copper stocks and flows which allows a detailed analysis of recycling efficiencies, copper stocks in use, and dissipated and landfilled copper. The model is based on historical mining and refined copper production data (1910-2010) enhanced by a unique data set of recent global semifinished goods production and copper end-use sectors provided by the copper industry. To enable the consistency of the simulated copper life cycle in terms of a closed mass balance, particularly the matching of recycled metal flows to reported historical annual production data, a method was developed to estimate the yearly global collection rates of end-of-life (postconsumer) scrap. Based on this method, we provide estimates of 8 different recycling indicators over time. The main indicator for the efficiency of global copper recycling from end-of-life (EoL) scrap--the EoL recycling rate--was estimated to be 45% on average, ± 5% (one standard deviation) due to uncertainty and variability over time in the period 2000-2010. As uncertainties of specific input data--mainly concerning assumptions on end-use lifetimes and their distribution--are high, a sensitivity analysis with regard to the effect of uncertainties in the input data on the calculated recycling indicators was performed. The sensitivity analysis included a stochastic (Monte Carlo) uncertainty evaluation with 10(5) simulation runs.

  8. Numerical investigations on flow dynamics of prismatic granular materials using the discrete element method

    NASA Astrophysics Data System (ADS)

    Hancock, W.; Weatherley, D.; Wruck, B.; Chitombo, G. P.

    2012-04-01

    The flow dynamics of granular materials is of broad interest in both the geosciences (e.g. landslides, fault zone evolution, and brecchia pipe formation) and many engineering disciplines (e.g chemical engineering, food sciences, pharmaceuticals and materials science). At the interface between natural and human-induced granular media flow, current underground mass-mining methods are trending towards the induced failure and subsequent gravitational flow of large volumes of broken rock, a method known as cave mining. Cave mining relies upon the undercutting of a large ore body, inducement of fragmentation of the rock and subsequent extraction of ore from below, via hopper-like outlets. Design of such mines currently relies upon a simplified kinematic theory of granular flow in hoppers, known as the ellipsoid theory of mass movement. This theory assumes that the zone of moving material grows as an ellipsoid above the outlet of the silo. The boundary of the movement zone is a shear band and internal to the movement zone, the granular material is assumed to have a uniformly high bulk porosity compared with surrounding stagnant regions. There is however, increasing anecdotal evidence and field measurements suggesting this theory fails to capture the full complexity of granular material flow within cave mines. Given the practical challenges obstructing direct measurement of movement both in laboratory experiments and in-situ, the Discrete Element Method (DEM [1]) is a popular alternative to investigate granular media flow. Small-scale DEM studies (c.f. [3] and references therein) have confirmed that movement within DEM silo flow models matches that predicted by ellipsoid theory, at least for mono-disperse granular material freely outflowing at a constant rate. A major draw-back of these small-scale DEM studies is that the initial bulk porosity of the simulated granular material is significantly higher than that of broken, prismatic rock. In this investigation, more

  9. Stability and dynamical properties of material flow systems on random networks

    NASA Astrophysics Data System (ADS)

    Anand, K.; Galla, T.

    2009-04-01

    The theory of complex networks and of disordered systems is used to study the stability and dynamical properties of a simple model of material flow networks defined on random graphs. In particular we address instabilities that are characteristic of flow networks in economic, ecological and biological systems. Based on results from random matrix theory, we work out the phase diagram of such systems defined on extensively connected random graphs, and study in detail how the choice of control policies and the network structure affects stability. We also present results for more complex topologies of the underlying graph, focussing on finitely connected Erdös-Réyni graphs, Small-World Networks and Barabási-Albert scale-free networks. Results indicate that variability of input-output matrix elements, and random structures of the underlying graph tend to make the system less stable, while fast price dynamics or strong responsiveness to stock accumulation promote stability.

  10. Quasi-dynamic Material Flow Analysis applied to the Austrian Phosphorus cycle

    NASA Astrophysics Data System (ADS)

    Zoboli, Ottavia; Rechberger, Helmut

    2013-04-01

    Phosphorus (P) is one of the key elements that sustain life on earth and that allow achieving the current high levels of food production worldwide. It is a non-renewable resource, without any existing substitute. Because of its current dissipative use by mankind and to its very slow geochemical cycle, this resource is rapidly depleting and it is strongly connected to the problem of ensuring food security. Moreover P is also associated to important environmental problems. Its extraction often generates hazardous wastes, while its accumulation in water bodies can lead to eutrophication, with consequent severe ecological damages. It is therefore necessary to analyze and understand in detail the system of P, in regard to its use and management, to identify the processes that should be targeted in order to reduce the overall consumption of this resource. This work aims at establishing a generic quasi-dynamic model, which describes the Austrian P-budget and which allows investigating the trends of P use in the past, but also selected future scenarios. Given the importance of P throughout the whole anthropogenic metabolism, the model is based on a comprehensive system that encompasses several economic sectors, from agriculture and animal husbandry to industry, consumption and waste and wastewater treatment. Furthermore it includes the hydrosphere, to assess the losses of P into water bodies, due to the importance of eutrophication problems. The methodology applied is Material Flow Analysis (MFA), which is a systemic approach to assess and balance the stocks and flows of a material within a system defined in space and time. Moreover the model is integrated in the software STAN, a freeware tailor-made for MFA. Particular attention is paid to the characteristics and the quality of the data, in order to include data uncertainty and error propagation in the dynamic balance.

  11. Investigation on the achievable flow length in injection moulding of polymeric materials with dynamic mould tempering.

    PubMed

    Meister, Steve; Drummer, Dietmar

    2013-01-01

    A variety of parts in microsystems technology are manufactured by injection moulding of polymeric materials. In Particular the high cooling velocity affects negatively the process and the resulting part properties. The scope of this paper is to investigate the influence on the reachable flow length in injection moulding of different polymeric materials. The results indicate that the mould temperature has less impact on the achievable flow length of the polymer melt as the injection pressure. A higher mould temperature leads only to a slight increase in flow length. In addition, a transcending of the glass or the crystallization temperature of polymeric materials with the mould temperature shows no effect on the achievable flow length of the material.

  12. Investigation on the Achievable Flow Length in Injection Moulding of Polymeric Materials with Dynamic Mould Tempering

    PubMed Central

    Drummer, Dietmar

    2013-01-01

    A variety of parts in microsystems technology are manufactured by injection moulding of polymeric materials. In Particular the high cooling velocity affects negatively the process and the resulting part properties. The scope of this paper is to investigate the influence on the reachable flow length in injection moulding of different polymeric materials. The results indicate that the mould temperature has less impact on the achievable flow length of the polymer melt as the injection pressure. A higher mould temperature leads only to a slight increase in flow length. In addition, a transcending of the glass or the crystallization temperature of polymeric materials with the mould temperature shows no effect on the achievable flow length of the material. PMID:23970840

  13. Dynamic power flow controllers

    DOEpatents

    Divan, Deepakraj M.; Prasai, Anish

    2017-03-07

    Dynamic power flow controllers are provided. A dynamic power flow controller may comprise a transformer and a power converter. The power converter is subject to low voltage stresses and not floated at line voltage. In addition, the power converter is rated at a fraction of the total power controlled. A dynamic power flow controller controls both the real and the reactive power flow between two AC sources having the same frequency. A dynamic power flow controller inserts a voltage with controllable magnitude and phase between two AC sources; thereby effecting control of active and reactive power flows between two AC sources.

  14. Tool design in friction stir processing: dynamic forces and material flow

    SciTech Connect

    D. E. Clark; K. S. Miller; C. R. Tolle

    2006-08-01

    Friction stir processing involves severe plastic flow within the material; the nature of this flow determines the final morphology of the weld, the resulting microstructures, and the presence or absence of defects such as internal cavities or "wormholes." The forces causing this plastic flow are a function of process parameters, including spindle speed, travel speed, and tool design and angle. Some of these forces are directly applied or a result of the mechanical constraints and compliance of the apparatus, while others are resolved forces resulting from an interaction of these applied forces and tool forces governed by processing parameters, and can be diminished or even reversed in sign with appropriate choices of process parameters. The present investigation is concerned mostly with the friction stir processing of 6061-T6 aluminum plates in a low-cost apparatus built from a commercial milling machine. A rotating dynamometer allows in-process measurement of actual spindle speed, torque, and forces in the x-, y-, and z-directions, as well as force control on these axes. Two main types of tool, both unthreaded, were used. The first had a pin about 4 mm in diameter and 4 mm in length, with a shoulder about 10 mm in diameter, and produced wormhole defects; the second, with a tapered pin about 5 mm long, a base diameter of about 6 mm, a tip diameter of about 4 mm, and a shoulder diameter (flat or dished) of about 19 mm, produced sound welds over a wide range of parameters.

  15. Materials Flow and Sustainability

    USGS Publications Warehouse

    Sznopek, John L.; Brown, William M.

    1998-01-01

    Materials extracted from the Earth are necessary to produce our most fundamental needs – food, clothing, and shelter. Materials are needed to maintain and improve our standard of living. Understanding the whole system of materials flow, from source to ultimate disposition, can help us better manage the use of natural resources and protect the environment.

  16. Lava Flow Dynamics

    NASA Technical Reports Server (NTRS)

    Taylor, G. Jeffrey

    1996-01-01

    This grant originally had four major tasks, all of which were addressed to varying extents during the course of the research: (1) Measure the fractal dimensions of lava flows as a function of topography, substrate, and rheology; (2) The nature of lava tube systems and their relation to flow fields; (3) A quantitative assessment of lava flow dynamics in light of the fractal nature of lava flow margins; and (4) Development and application of a new remote sensing tool based on fractal properties. During the course of the research, the project expanded to include the following projects: (1) A comparison of what we can-learn from remote sensing studies of lava flow morphology and from studies of samples of lava flows; (2) Study of a terrestrial analog of the nakhlites, one of the groups of meteorites from Mars; and (3) Study of the textures of Hawaiian basalts as an aid in understanding the dynamics (flow rates, inflation rates, thermal history) of flow interiors. In addition, during the first year an educational task (development and writing of a teacher's guide and activity set to accompany the lunar sample disk when it is sent to schools) was included.

  17. Segregation dynamics in debris flows

    NASA Astrophysics Data System (ADS)

    Hill, K. M.; Fei, M.

    2014-12-01

    Debris flows are massive flows consisting of mixtures of particles of different sizes and interstitial fluids such as water and mud. In sheared mixtures of different-sized (same density) particles, it is well known that larger particles tend to go up (toward the free surface), and the smaller particles, down, commonly referred to as the "Brazil-nut problem" or "kinetic sieving". When kinetic sieving fluxes are combined with advection in flows, they can give rise to a spectacular range of segregation patterns. These segregation / advection dynamics are recognized as playing a role in the coarsening of a debris flow front (its "snout") and the coarsening of the self-formed channel sides or levees. Since particle size distribution influences the flow dynamics including entrainment of bed materials, modeling segregation dynamics in debris flows is important for modeling the debris flows themselves. In sparser systems, the Brazil-nut segregation is well-modeled using kinetic theory applied to dissipative systems, where an underlying assumption involves random, uncorrelated collisions. In denser systems, where kinetic theory breaks down we have recently developed a new mixture model that demonstrates the segregation fluxes are driven by two effects associated with the kinetic stress or granular temperature (the kinetic energy associated with velocity fluctuations): (1) the difference between the partitioning of kinetic and contact stresses among the species in the mixture and (2) a kinetic stress gradient. Both model frameworks involve the temperature gradient as a driving force for segregation, but kinetic theory sends larger particles toward lower temperatures, and our mixture model sends larger particles away from lower temperatures. Which framework works under what conditions appears to depend on correlations in the flow such as those manifested in clusters and force chains. We discuss the application of each theoretical framework to representing segregation dynamics

  18. Dynamics of Granular Materials

    NASA Technical Reports Server (NTRS)

    Behringer, Robert P.

    1996-01-01

    Granular materials exhibit a rich variety of dynamical behavior, much of which is poorly understood. Fractal-like stress chains, convection, a variety of wave dynamics, including waves which resemble capillary waves, l/f noise, and fractional Brownian motion provide examples. Work beginning at Duke will focus on gravity driven convection, mixing and gravitational collapse. Although granular materials consist of collections of interacting particles, there are important differences between the dynamics of a collections of grains and the dynamics of a collections of molecules. In particular, the ergodic hypothesis is generally invalid for granular materials, so that ordinary statistical physics does not apply. In the absence of a steady energy input, granular materials undergo a rapid collapse which is strongly influenced by the presence of gravity. Fluctuations on laboratory scales in such quantities as the stress can be very large-as much as an order of magnitude greater than the mean.

  19. Biologically inspired dynamic material systems.

    PubMed

    Studart, André R

    2015-03-09

    Numerous examples of material systems that dynamically interact with and adapt to the surrounding environment are found in nature, from hair-based mechanoreceptors in animals to self-shaping seed dispersal units in plants to remodeling bone in vertebrates. Inspired by such fascinating biological structures, a wide range of synthetic material systems have been created to replicate the design concepts of dynamic natural architectures. Examples of biological structures and their man-made counterparts are herein revisited to illustrate how dynamic and adaptive responses emerge from the intimate microscale combination of building blocks with intrinsic nanoscale properties. By using top-down photolithographic methods and bottom-up assembly approaches, biologically inspired dynamic material systems have been created 1) to sense liquid flow with hair-inspired microelectromechanical systems, 2) to autonomously change shape by utilizing plantlike heterogeneous architectures, 3) to homeostatically influence the surrounding environment through self-regulating adaptive surfaces, and 4) to spatially concentrate chemical species by using synthetic microcompartments. The ever-increasing complexity and remarkable functionalities of such synthetic systems offer an encouraging perspective to the rich set of dynamic and adaptive properties that can potentially be implemented in future man-made material systems. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Assessment of the effects of the Japanese shift to lead-free solders and its impact on material substitution and environmental emissions by a dynamic material flow analysis.

    PubMed

    Fuse, Masaaki; Tsunemi, Kiyotaka

    2012-11-01

    Lead-free electronics has been extensively studied, whereas their adoption by society and their impact on material substitution and environmental emissions are not well understood. Through a material flow analysis (MFA), this paper explores the life cycle flows for solder-containing metals in Japan, which leads the world in the shift to lead-free solders in electronics. The results indicate that the shift has been progressing rapidly for a decade, and that substitutes for lead in solders, which include silver and copper, are still in the early life cycle stages. The results also show, however, that such substitution slows down during the late life cycle stages owing to long electronic product lifespans. This deceleration of material substitution in the solder life cycle may not only preclude a reduction in lead emissions to air but also accelerate an increase in silver emissions to air and water. As an effective measure against ongoing lead emissions, our scenario analysis suggests an aggressive recycling program for printed circuit boards that utilizes an existing recycling scheme. Copyright © 2012 Elsevier B.V. All rights reserved.

  1. Dynamic indentation hardness of materials

    NASA Astrophysics Data System (ADS)

    Koeppel, Brian James

    Indentation hardness is one of the simplest and most commonly used measures for quickly characterizing material response under static loads. Hardness may mean resistance to cutting to a machinist, resistance to wear to a tribologist, or a measure of flow stress to a design engineer. In this simple technique, a predetermined force is applied to an indenter for 5-30 seconds causing it to penetrate a specimen. By measuring the load and the indentation size, a hardness value is determined. However, the rate of deformation during indenter penetration is of the order of 10sp{-4}\\ ssp{-1}. In most practical applications, such as high speed machining or impact, material deforms at strain rates in excess of 10sp3{-}10sp5\\ ssp{-1}. At such high rates, it is well established that the plastic behavior of materials is considerably different from their static counterpart. For example, materials exhibit an increase in their yield stress, flow stress, fracture stress, and fracture toughness at high strain rates. Hence, the use of static hardness as an indicator of material response under dynamic loads may not be appropriate. Accordingly, a simple dynamic indentation hardness tester is developed for characterizing materials at strain rates similar to those encountered in realistic situations. The experimental technique uses elastic stress wave propagation phenomena in a slender rod. The technique is designed to deliver a single indentation load of 100-200 mus duration. Similar to static measurements, the dynamic hardness is determined from the measured load and indentation size. Hardness measurements on a range of metals have revealed that the dynamic hardness is consistently greater than the static hardness. The increase in hardness is strongly dependent on the crystal structure of the material. The observed trends in hardness are also found to be consistent with the yield and flow stresses of these materials under uniaxial compression. Therefore, it is suggested that the

  2. Earth materials and earth dynamics

    SciTech Connect

    Bennett, K; Shankland, T.

    2000-11-01

    In the project ''Earth Materials and Earth Dynamics'' we linked fundamental and exploratory, experimental, theoretical, and computational research programs to shed light on the current and past states of the dynamic Earth. Our objective was to combine different geological, geochemical, geophysical, and materials science analyses with numerical techniques to illuminate active processes in the Earth. These processes include fluid-rock interactions that form and modify the lithosphere, non-linear wave attenuations in rocks that drive plate tectonics and perturb the earth's surface, dynamic recrystallization of olivine that deforms the upper mantle, development of texture in high-pressure olivine polymorphs that create anisotropic velocity regions in the convecting upper mantle and transition zone, and the intense chemical reactions between the mantle and core. We measured physical properties such as texture and nonlinear elasticity, equation of states at simultaneous pressures and temperatures, magnetic spins and bonding, chemical permeability, and thermal-chemical feedback to better characterize earth materials. We artificially generated seismic waves, numerically modeled fluid flow and transport in rock systems and modified polycrystal plasticity theory to interpret measured physical properties and integrate them into our understanding of the Earth. This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL).

  3. Material Flows and Carbon Cycles

    NASA Astrophysics Data System (ADS)

    Worrell, E.

    2003-12-01

    The industrial sector emits almost 43 percent of the global anthropogenic carbon dioxide emissions to produce materials and products. Furthermore, energy is used to move materials and products and process the waste. Hence, a large amount of energy is consumed and CO2 is emitted to sustain our materials system. Until recently, studies investigating mitigation options focused on changes in the energy system. For industrial processes most studies evaluate how the current materials system can be maintained producing fewer greenhouse gas emissions. Three elements of a strategy to improve the long-term materials productivity are the reduction of dissipative uses of non-biodegradable materials, secondly, the re-design of products to use less material or design for re-use or recycling, and thirdly, develop more efficient technologies for material conversion and recycling. This will reduce or eliminate the need to extract virgin materials from the environment, and reduce CO2 emissions from the energy-intensive production processes. To assess measures to reduce materials consumption, fossil fuels consumption and CO2 emissions, detailed understanding of the material system is needed. The lifecycle of materials has to be investigated including all branches of industry with all the inputs and outputs. We start with a discussion of materials and the carbon cycle focusing on the contribution of materials to anthropogenic carbon flows. We discuss CO2 emissions from energy use in materials extraction and production, fossil (e.g. plastics) and biomass carbon (e.g. lumber, paper) used as feedstock of materials, and mineral sources (e.g. cement). We discuss opportunities to reduce CO2 emissions by improving the efficiency with which society uses materials through product design, material substitution, product reuse and material recycling.

  4. The Dynamics of Flowing Waters.

    ERIC Educational Resources Information Center

    Mattingly, Rosanna L.

    1987-01-01

    Describes a series of activities designed to help students understand the dynamics of flowing water. Includes investigations into determining water discharge, calculating variable velocities, utilizing flood formulas, graphing stream profiles, and learning about the water cycle. (TW)

  5. The Dynamics of Flowing Waters.

    ERIC Educational Resources Information Center

    Mattingly, Rosanna L.

    1987-01-01

    Describes a series of activities designed to help students understand the dynamics of flowing water. Includes investigations into determining water discharge, calculating variable velocities, utilizing flood formulas, graphing stream profiles, and learning about the water cycle. (TW)

  6. Lava crusts and flow dynamics

    NASA Technical Reports Server (NTRS)

    Kilburn, C. R. J.

    1993-01-01

    Lava flows can be considered as hot viscous cores within thinner, solidified crusts. Interaction between crust and core determines a flow's morphological and dynamical evolution. When the lava core dominates, flow advance approaches a steady state. When crusts are the limiting factor, advance is more irregular. These two conditions can be distinguished by a timescale ratio comparing rates of core deformation and crustal formation. Aa and budding pahoehoe lavas are used as examples of core- and crustal-dominated flows, respectively. A simple model describes the transition between pahoehoe and aa flow in terms of lava discharge rate, underlying slope, and either the thickness or velocity of the flow front. The model shows that aa morphologies are characterized by higher discharge rates and frontal velocities and yields good quantitative agreement with empirical relations distinguishing pahoehoe and aa emplacement on Hawaii.

  7. Dynamic compaction of granular materials

    PubMed Central

    Favrie, N.; Gavrilyuk, S.

    2013-01-01

    An Eulerian hyperbolic multiphase flow model for dynamic and irreversible compaction of granular materials is constructed. The reversible model is first constructed on the basis of the classical Hertz theory. The irreversible model is then derived in accordance with the following two basic principles. First, the entropy inequality is satisfied by the model. Second, the corresponding ‘intergranular stress’ coming from elastic energy owing to contact between grains decreases in time (the granular media behave as Maxwell-type materials). The irreversible model admits an equilibrium state corresponding to von Mises-type yield limit. The yield limit depends on the volume fraction of the solid. The sound velocity at the yield surface is smaller than that in the reversible model. The last one is smaller than the sound velocity in the irreversible model. Such an embedded model structure assures a thermodynamically correct formulation of the model of granular materials. The model is validated on quasi-static experiments on loading–unloading cycles. The experimentally observed hysteresis phenomena were numerically confirmed with a good accuracy by the proposed model. PMID:24353466

  8. Dynamics of electromechanical flow structures.

    NASA Technical Reports Server (NTRS)

    Jones, T. B., Jr.; Melcher, J. R.

    1973-01-01

    Free-surface gravity flows and capillary wicking provide examples of flow structures with fluid partially ducted at free surfaces by external forces. Wall-less electromechanical flow structures are developed which have a similar nature, but with polarization forces providing the orientation at free surfaces. Like their mechanical counterparts, these have the ability to ingest liquid or expel vapor through their walls. The structures consist of electrodes running in the flow direction z with slowly varying cross sections in a plane transverse to the flow. A formulation is given of the long-wave nonlinear (principal mode) dynamics, with use made of energy functions to represent a broad class of possible mechanical and electrical structure geometries.

  9. Mixing, segregation, and flow of granular materials

    NASA Astrophysics Data System (ADS)

    McCarthy, Joseph J.

    1998-11-01

    This dissertation addresses mixing, segregation, and flow of granular materials with the ultimate goal of providing fundamental understanding and tools for the rational design and optimization of mixing devices. In particular, the paradigm cases of a slowly rotated tumbler mixer and flow down an inclined plane are examined. Computational work, as well as supporting experiments, are used to probe both two and three dimensional systems. In the avalanching regime, the mixing and flow can be viewed either on a global-scale or a local-scale. On the global-scale, material is transported via avalanches whose gross motion can be well described by geometrical considerations. On the local-scale, the dynamics of the particle motion becomes important; particles follow complicated trajectories that are highly sensitive to differences in size/density/morphology. By decomposing the problem in this way, it is possible to study the implications of the geometry and dynamics separately and to add complexities in a controlled fashion. This methodology allows even seemingly difficult problems (i.e., mixing in non-convex geometries, and mixing of dissimilar particles) to be probed in a simple yet methodical way. In addition this technique provides predictions of optimal mixing conditions in an avalanching tumbler, a criterion for evaluating the effect of mixer shape, and mixing enhancement strategies for both two and three dimensional mixers. In the continuous regime, the flow can be divided into two regions: a rapid flow region of the cascading layer at the free surface, and a fixed bed region undergoing solid body rotation. A continuum-based description, in which averages are taken across the layer, generates quantitative predictions about the flow in the cascading layer and agrees well with experiment. Incorporating mixing through a diffusive flux (as well as constitutive expression for segregation) within the cascading layer allows for the determination of optimal mixing conditions

  10. Materials in the economy; material flows, scarcity, and the environment

    USGS Publications Warehouse

    Wagner, Lorie A.

    2002-01-01

    The importance of materials to the economy of the United States is described, including the levels of consumption and uses of materials. The paths (or flows) that materials take from extraction, through processing, to consumer products, and then final disposition are illustrated. Scarcity and environmental issues as they relate to the flow of materials are discussed. Examples for the three main themes of the report (material flows, scarcity, and the environment) are presented.

  11. Dynamic fracture of heterogeneous materials

    SciTech Connect

    Stout, M.G.; Liu, C.; Addessio, F.L.; Williams, T.O.; Bennett, J.G.; Haberman, K.S.; Asay, B.W.

    1998-12-31

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The objective of this project was to investigate the fundamental aspects of the process of dynamic fracture propagation in heterogeneous materials. The work focused on three important, but poorly understood, aspects of dynamic fracture for materials with a heterogeneous microstructure. These were: the appropriateness of using a single-parameter asymptotic analysis to describe dynamic crack-tip deformation fields, the temperature rises at the tip and on the flanks of a running crack, and the constitutive modeling of damage initiation and accumulation.

  12. MPD thrust chamber flow dynamics

    NASA Astrophysics Data System (ADS)

    1990-08-01

    Flow within the thrust chamber of a Magnetoplasmadynamic (MPD) arcjet is examined experimentally and modeled with a 2-D magnetohydrodynamic code. Two quasi-steady MPD thrusters are considered under the same input conditions of current (21 kA) and total mass flow rate (0.006 kg/s, argon + 1.5 percent hydrogen). The arcjets have the same basic design, consisting of a central cathode, 3.8 cm diameter and 5 cm long, separated from a coaxial anode of equal length by a uniform gap of 2.3 cm. Two different mass injection arrangements are used (100 percent at mid-radius, and 50 percent at the cathode base, with the remainder at mid-radius). A new spectroscopic analysis procedure is developed that allows distributions of radial speed, heavy particle temperature and turbulent speed to be extracted from chordal measurements of light emission by the two species in the plasma flow. Good qualitative (and reasonable quantitative) agreement exists with distributions calculated by the MHD code, indicating that flow within the thrust chamber expands from an electromagnetically pumped plasma base (vs a pumped jet off the cathode tip). The significant variation of internal flow dynamics with mass injector arrangement implies the need for extensive experimentally validated code modeling in order to evaluate the potential performance of MPD thrusters.

  13. Dynamic material modeling in hot forging

    SciTech Connect

    El-Gizawy, A.S. )

    1992-03-01

    A dynamic material model that characterized flow behavior in the workpiece under forging conditions was required to optimize the process and produce defect-free product at minimum cost. Constitutive equations describe the relationship between stress, strain rate, and temperature under forging conditions. Using aluminum alloy 7050, numerous deformation experiments were conducted to fully characterize constitutive equation variables. A thorough description of the experimental arrangement was provided. Flow data and efficiency data were assembled into a three-dimensional plot of temperature vs. strain rate vs. deformation efficiency to produce an efficiency map. The efficiency map provided the information required for optimization of forging process design. The results of dynamic modeling of the material were used in simulating the isothermal forging of a particular part. Recommendations concerning optimum preform design and processing conditions were reported.

  14. Fouling dynamics in suspension flows

    NASA Astrophysics Data System (ADS)

    Shakib-Manesh, A.; Åström, J. A.; Koponen, A.; Raiskinmäki, P.; Timonen, J.

    2002-09-01

    A particle suspension flowing in a channel in which fouling layers are allowed to form on the channel walls is investigated by numerical simulation. A two-dimensional phase diagram with at least four different behaviors is constructed. The fouling is modeled by attachment during collision with the deposits and by detachment caused by large enough hydrodynamic drag. For fixed total number of particles and small Reynolds numbers, the relevant parameters governing the fouling dynamics are the solid volume fraction of the suspension and the detachment drag force threshold. Below a critical curve in this 2D phase space only transient fouling takes place when the suspension is accelerated from rest by a pressure gradient. Above the fouling transition line, persistent fouling layers are formed via ballistic deposition for low and via homogeneous deposition for large solid volume fractions. Close to the fouling transition line, the flow path between the deposited layers meanders, while necking appears for increasing distance from the transition. Finally, another transition to a fully blocked flow path takes place. As determined by the estimated amount of deposited particles at saturation, both transitions seem to be discontinuous. Large fluctuations and long saturation times are typical of the dynamics of the system.

  15. Particle cage dynamics in flowing colloidal dispersions

    NASA Astrophysics Data System (ADS)

    Marenne, Stephanie; Morris, Jeffrey F.

    2016-11-01

    The idea of the particle in a suspension at rest being trapped in a cage formed by its neighbors, widely used to understand glassy suspensions, has been applied to freely flowing suspensions. Stokesian Dynamics, a discrete particle simulation, is used to simulate the flow of monodisperse colloidal hard sphere suspensions. The cage analogy is useful to study the nonlinear stress in the material during start-up of shear flow, where the neighbor cage deforms and breaks, and during oscillatory shear flow where, depending on the amplitude of oscillation, the particle is trapped inside the cage or escapes during the oscillation cycle. A precise statistical definition of the cage in terms of the nearest neighbor ring in the pair distribution function is developed. We examine the dependence of the cage dynamics on the volume fraction of particles and the Peclet number Pe , the ratio between shear and Brownian forces. Under flow, the cage is found to break at quite definite positions, and the structural distortion is found to be clearly related to the shear and normal stress response. The shear strain needed to break the neighbor cage depends on Pe as Brownian motion enhances the total deformation. A simple model captures the strain at the stress overshoot for start-up of steady shear.

  16. Bio-relevant dissolution testing of hard capsules prepared from different shell materials using the dynamic open flow through test apparatus.

    PubMed

    Garbacz, Grzegorz; Cadé, Dominique; Benameur, Hassan; Weitschies, Werner

    2014-06-16

    Current compendial dissolution and disintegrating testing is unable to mimic physiological conditions affecting gastric drug release from immediate release dosage forms. In order to obtain more realistic data, a novel test setup was developed that we term a 'dynamic open flow through test apparatus'. It is based on the previously described dissolution stress test device and attempts to simulate the intra-gastric dissolution conditions pertinent to immediate release dosage forms administered under fasting conditions with respect to flow rates, intra-gastric temperature profiles and gastric motility. The concept of the dynamic open flow through test apparatus has been tested using five different types of hard capsules: conventional hard gelatin capsules (HGC), three hypromellose based capsules (Vcaps, Vcaps Plus and DRcaps) and pullulan based capsules (Plantcaps). These were of different sizes but all contained 100mg caffeine in each formulation, adjusted to avoid buoyancy by addition of excipient. When the capsules were stressed in the apparatus under the dynamic flow conditions applying mild pressure simulating gastric motility, release from release from Vcaps Plus, Vcaps and Plantcaps capsules was very well comparable to HGC. Capsules are usually swallowed with cold water and the temperature dependency of release from gelatin was noted as a significant factor, since heat exchange in the stomach is slow. Copyright © 2013 Elsevier B.V. All rights reserved.

  17. Dynamic properties of ceramic materials

    SciTech Connect

    Grady, D.E.; Wise, J.L.

    1993-09-01

    Controlled impact methods have been employed to obtain dynamic response properties of armor materials. Experimental data have been obtained for high-strength ceramics. Continued analysis of time-resolved velocity interferometer measurements has produced systematic material-property data for Hugoniot and release response, initial and post-yield strength, pressure-induced phase transformation, and dynamic fracture strength. A new technique has been developed to measure hydrodynamic properties of ceramic through shock-wave experiments on metal-ceramic composites and data obtained for silicon carbide. Additional data on several titanium diboride ceramics and high-quality aluminum oxide ceramic have been acquired, and issues regarding the influence of microstructure on dynamic properties have emerged. Comparison of dynamic (Hugoniot elastic limit) strength and indentation hardness data has been performed and important correlations revealed. Innovative impact experiments on confined and unconfined alumina rods using axial and transverse VISAR diagnostics have been demonstrated which permit acquisition of multiaxial dynamic response data. Dynamic failure properties of a high-density aluminosilicate glass, similar in composition to the intergranular glassy phase of some aluminas, have been investigated with regard to yield, spall, and failure-wave propagation.

  18. The Digital Material: Molecular Dynamics

    NASA Astrophysics Data System (ADS)

    Bailey, Nicholas P.; Cretegny, Thierry; Dolgert, Andrew J.; Myers, Christopher R.; Schiøtz, Jakob; Sethna, James P.

    2001-03-01

    We announce the release of the molecular dynamics component of the Digital Material. The Digital Material is our multiscale modeling software infrastructure, designed for flexibility, extensibility, and for compatibility between simulations on disparate length scales. We illustrate how we use the high-level scripting language Python to control our low-level numerical kernals, and to interface them with standard visualization and data repository tools. Our use of design-patterns methodology leads us to decompose the MD simulation into a few weakly-coupled classes, such as AtomsMover, NeighborLocator, Potential, Constraint, and BoundaryConditions.

  19. Physical Properties of Various Materials Relevant to Granular Flow

    USDA-ARS?s Scientific Manuscript database

    Because of the ubiquitous nature of granular materials, ranging from natural avalanches to industrial storage and processing operations, interest in quantifying and predicting the dynamics of granular flow continues to increase. The objective of this study was to investigate various physical proper...

  20. Dynamics of assembly production flow

    NASA Astrophysics Data System (ADS)

    Ezaki, Takahiro; Yanagisawa, Daichi; Nishinari, Katsuhiro

    2015-06-01

    Despite recent developments in management theory, maintaining a manufacturing schedule remains difficult because of production delays and fluctuations in demand and supply of materials. The response of manufacturing systems to such disruptions to dynamic behavior has been rarely studied. To capture these responses, we investigate a process that models the assembly of parts into end products. The complete assembly process is represented by a directed tree, where the smallest parts are injected at leaves and the end products are removed at the root. A discrete assembly process, represented by a node on the network, integrates parts, which are then sent to the next downstream node as a single part. The model exhibits some intriguing phenomena, including overstock cascade, phase transition in terms of demand and supply fluctuations, nonmonotonic distribution of stockout in the network, and the formation of a stockout path and stockout chains. Surprisingly, these rich phenomena result from only the nature of distributed assembly processes. From a physical perspective, these phenomena provide insight into delay dynamics and inventory distributions in large-scale manufacturing systems.

  1. Autogenic dynamics of debris-flow fans

    NASA Astrophysics Data System (ADS)

    van den Berg, Wilco; de Haas, Tjalling; Braat, Lisanne; Kleinhans, Maarten

    2015-04-01

    Alluvial fans develop their semi-conical shape by cyclic avulsion of their geomorphologically active sector from a fixed fan apex. These cyclic avulsions have been attributed to both allogenic and autogenic forcings and processes. Autogenic dynamics have been extensively studied on fluvial fans through physical scale experiments, and are governed by cyclic alternations of aggradation by unconfined sheet flow, fanhead incision leading to channelized flow, channel backfilling and avulsion. On debris-flow fans, however, autogenic dynamics have not yet been directly observed. We experimentally created debris-flow fans under constant extrinsic forcings, and show that autogenic dynamics are a fundamental intrinsic process on debris-flow fans. We found that autogenic cycles on debris-flow fans are driven by sequences of backfilling, avulsion and channelization, similar to the cycles on fluvial fans. However, the processes that govern these sequences are unique for debris-flow fans, and differ fundamentally from the processes that govern autogenic dynamics on fluvial fans. We experimentally observed that backfilling commenced after the debris flows reached their maximum possible extent. The next debris flows then progressively became shorter, driven by feedbacks on fan morphology and flow-dynamics. The progressively decreasing debris-flow length caused in-channel sedimentation, which led to increasing channel overflow and wider debris flows. This reduced the impulse of the liquefied flow body to the flow front, which then further reduced flow velocity and runout length, and induced further in-channel sedimentation. This commenced a positive feedback wherein debris flows became increasingly short and wide, until the channel was completely filled and the apex cross-profile was plano-convex. At this point, there was no preferential transport direction by channelization, and the debris flows progressively avulsed towards the steepest, preferential, flow path. Simultaneously

  2. Single Polymer Dynamics under Large Amplitude Oscillatory Extensional (LAOE) Flow

    NASA Astrophysics Data System (ADS)

    Zhou, Yuecheng; Schroeder, Charles M.

    Over the past two decades, advances in fluorescence imaging and particle manipulation have enabled the direct observation of single polymer dynamics in model flows such as shear flow and planar extensional flow. The vast majority of single polymer studies, however, has focused on chain dynamics using simple transient step forcing functions. In order to study single polymer dynamics in non-idealized model flows, there is a clear need to implement more complicated transient flow forcing functions. In bulk rheology, large amplitude oscillatory shear (LAOS) was widely used to study the linear and nonlinear viscoelasticity of materials, but not yet been applied to molecular rheology. In this work, we directly probe single polymer dynamics using oscillatory extensional flow in precisely controlled microfluidic devices. We are able to generate large and small amplitude sinusoidal oscillatory extensional flow in a cross-slot microfluidic device while imaging the conformational dynamics of a single polymer trapped at the stagnation point. In this flow, polymer chains are stretched, squeezed, and rotated between extensional/compressional axes in a highly dynamic and transient manner. Using this technique, we studied the dynamics and coil-stretch transition of a single λ-DNA as a function of the Weissenberg number (Wi) and Deborah number (De). Moreover, we use Brownian dynamics simulation to map a wide range of Pipkin space for polymers from linear steady-state conditions to non-linear unsteady-states. Our results reveal a critical Wi at the coil-stretch transition that is function of the De in LAOE flow. Department of Materials Science and Engineering.

  3. Accretion Dynamics on Wet Granular Materials

    NASA Astrophysics Data System (ADS)

    Saingier, Guillaume; Sauret, Alban; Jop, Pierre

    2017-05-01

    Wet granular aggregates are common precursors of construction materials, food, and health care products. The physical mechanisms involved in the mixing of dry grains with a wet substrate are not well understood and difficult to control. Here, we study experimentally the accretion of dry grains on a wet granular substrate by measuring the growth dynamics of the wet aggregate. We show that this aggregate is fully saturated and its cohesion is ensured by the capillary depression at the air-liquid interface. The growth dynamics is controlled by the liquid fraction at the surface of the aggregate and exhibits two regimes. In the viscous regime, the growth dynamics is limited by the capillary-driven flow of liquid through the granular packing to the surface of the aggregate. In the capture regime, the capture probability depends on the availability of the liquid at the saturated interface, which is controlled by the hydrostatic depression in the material. We propose a model that rationalizes our observations and captures both dynamics based on the evolution of the capture probability with the hydrostatic depression.

  4. Material flows generated by pyromet copper smelting

    USGS Publications Warehouse

    Goonan, T.G.

    2005-01-01

    Copper production through smelting generates large volumes of material flows. As copper contained in ore becomes copper contained in concentrate to be fed into the smelting process, it leaves behind an altered landscape, sometimes mine waste, and always mill tailings. Copper concentrate, fluxing materials, fuels, oxygen, recyclables, scrap and water are inputs to the process. Dust (recycled), gases - containing carbon dioxide (CO2) (dissipated) and sulfur dioxide (SO2) (mostly collected, transformed and sold) and slag (discarded or sold) - are among the significant process outputs. This article reports estimates of the flows of these input/output materials for a particular set of smelters studied in some countries.

  5. Dynamic Behavior of Aircraft Materials

    DTIC Science & Technology

    1978-02-28

    and the materials and structures making up the system. Imposed on this are the system 16 w a, Ec d~ ci-. ~ 1 Z5 C ~ ~ I- ~C5 ClCf / -’-. w IS- ZEr 17 LI...mJidspan given by where P i cthelotiad and Ehis the modulus obtained from the load-time trace. Two of the specimens in this investigation were 16--ply...was undesirable. There are any number of analytic correlation studies that have been performed to show that using dynamic properties can make a

  6. Particle Dynamics in Tangential Flow Filtration

    NASA Astrophysics Data System (ADS)

    Garcia, Mike; Pennathur, Sumita

    2015-11-01

    Tangential Flow Filtration (TFF) is a rapid and efficient method for filtration and separation of solutions containing particles such as viruses, bacteria or cellular material. Enhancing the efficiency of TFF not only requires a detailed understanding of the individual mechanisms behind particle transport, but the interaction between these transport mechanisms and a porous wall. In this work, we numerically and experimentally explore how inertial migration is affected by the presence of a permeate flow through the porous walls of a microchannel in order to develop a platform for further studies of particle transport in a TFF device. Numerically, we use COMSOL multiphysics to model the large parameter space of permeate versus inertial forces. Experimentally, we develop a MEMS fabricated TFF device to confirm the results of the numerical model, where the permeate flow is controlled using multiple pumps and pressure transducers regulated by a feedback loop. Experimental and numerical results reveal interesting dynamics, including the competition between permeate and inertial forces and the consequences of this competition on particle trajectories and equilibrium location.

  7. Flow chemistry meets advanced functional materials.

    PubMed

    Myers, Rebecca M; Fitzpatrick, Daniel E; Turner, Richard M; Ley, Steven V

    2014-09-22

    Flow chemistry and continuous processing techniques are beginning to have a profound impact on the production of functional materials ranging from quantum dots, nanoparticles and metal organic frameworks to polymers and dyes. These techniques provide robust procedures which not only enable accurate control of the product material's properties but they are also ideally suited to conducting experiments on scale. The modular nature of flow and continuous processing equipment rapidly facilitates reaction optimisation and variation in function of the products. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Tethered DNA dynamics in shear flow.

    PubMed

    Zhang, Yu; Donev, Aleksandar; Weisgraber, Todd; Alder, Berni J; Graham, Michael D; de Pablo, Juan J

    2009-06-21

    We study the cyclic dynamics of a single polymer tethered to a hard wall in shear flow using Brownian dynamics, the lattice Boltzmann method, and a recent stochastic event-driven molecular dynamics algorithm. We focus on the dynamics of the free end (last bead) of the tethered chain and we examine the cross-correlation function and power spectral density of the chain extensions in the flow and gradient directions as a function of chain length N and dimensionless shear rate Wi. Extensive simulation results suggest a classical fluctuation-dissipation stochastic process and question the existence of periodicity of the cyclic dynamics, as previously claimed. We support our numerical findings with a simple analytical calculation for a harmonic dimer in shear flow.

  9. Dynamics of flexible fibers in shear flow

    SciTech Connect

    Słowicka, Agnieszka M.; Wajnryb, Eligiusz; Ekiel-Jeżewska, Maria L.

    2015-09-28

    Dynamics of flexible non-Brownian fibers in shear flow at low-Reynolds-number are analyzed numerically for a wide range of the ratios A of the fiber bending force to the viscous drag force. Initially, the fibers are aligned with the flow, and later they move in the plane perpendicular to the flow vorticity. A surprisingly rich spectrum of different modes is observed when the value of A is systematically changed, with sharp transitions between coiled and straightening out modes, period-doubling bifurcations from periodic to migrating solutions, irregular dynamics, and chaos.

  10. TORAC. Tornado-Induced Flow Material Transport

    SciTech Connect

    Andrae, R.W.; Gregory, W.S.; Martin, R.A.; Tang, P.K.

    1992-01-13

    TORAC models tornado-induced flows, pressures, and material transport within structures. Its use is directed toward nuclear fuel cycle facilities and their primary release pathway, the ventilation system. However, it is applicable to other structures and can model other airflow pathways within a facility. In a nuclear facility, this network system could include process cells, canyons, laboratory offices, corridors, and offgas systems. TORAC predicts flow through a network system that also includes ventilation system components such as filters, dampers, ducts, and blowers. These ventilation system components are connected to the rooms and corridors of the facility to form a complete network for moving air through the structure and, perhaps, maintaining pressure levels in certain areas. The material transport capability in TORAC is very basic and includes convection, depletion, entrainment, and filtration of material.

  11. Granular Material Flows with Interstitial Fluid Effects

    NASA Technical Reports Server (NTRS)

    Hunt, Melany L.; Brennen, Christopher E.

    2004-01-01

    The research focused on experimental measurements of the rheological properties of liquid-solid and granular flows. In these flows, the viscous effects of the interstitial fluid, the inertia of the fluid and particles, and the collisional interactions of the particles may all contribute to the flow mechanics. These multiphase flows include industrial problems such as coal slurry pipelines, hydraulic fracturing processes, fluidized beds, mining and milling operation, abrasive water jet machining, and polishing and surface erosion technologies. In addition, there are a wide range of geophysical flows such as debris flows, landslides and sediment transport. In extraterrestrial applications, the study of transport of particulate materials is fundamental to the mining and processing of lunar and Martian soils and the transport of atmospheric dust (National Research Council 2000). The recent images from Mars Global Surveyor spacecraft dramatically depict the complex sand and dust flows on Mars, including dune formation and dust avalanches on the slip-face of dune surfaces. These Aeolian features involve a complex interaction of the prevailing winds and deposition or erosion of the sediment layer; these features make a good test bed for the verification of global circulation models of the Martian atmosphere.

  12. Flow in porous metallic materials: a magnetic resonance imaging study.

    PubMed

    Xu, Shoujun; Harel, Elad; Michalak, David J; Crawford, Charles W; Budker, Dmitry; Pines, Alexander

    2008-11-01

    To visualize flow dynamics of analytes inside porous metallic materials with laser-detected magnetic resonance imaging (MRI). We examine the flow of nuclear-polarized water in a porous stainless steel cylinder. Laser-detected MRI utilizes a sensitive optical atomic magnetometer as the detector. Imaging was performed in a remote-detection mode: the encoding was conducted in the Earth's magnetic field, and detection is conducted downstream of the encoding location. Conventional MRI (7T) was also performed for comparison. Laser-detected MRI clearly showed MR images of water flowing through the sample, whereas conventional MRI provided no image. We demonstrated the viability of laser-detected MRI at low-field for studying porous metallic materials, extending MRI techniques to a new group of systems that is normally not accessible to conventional MRI. Copyright (c) 2008 Wiley-Liss, Inc.

  13. Dynamics of Sheared Granular Materials

    NASA Technical Reports Server (NTRS)

    Kondic, Lou; Utter, Brian; Behringer, Robert P.

    2002-01-01

    This work focuses on the properties of sheared granular materials near the jamming transition. The project currently involves two aspects. The first of these is an experiment that is a prototype for a planned ISS (International Space Station) flight. The second is discrete element simulations (DES) that can give insight into the behavior one might expect in a reduced-g environment. The experimental arrangement consists of an annular channel that contains the granular material. One surface, say the upper surface, rotates so as to shear the material contained in the annulus. The lower surface controls the mean density/mean stress on the sample through an actuator or other control system. A novel feature under development is the ability to 'thermalize' the layer, i.e. create a larger amount of random motion in the material, by using the actuating system to provide vibrations as well control the mean volume of the annulus. The stress states of the system are determined by transducers on the non-rotating wall. These measure both shear and normal components of the stress on different size scales. Here, the idea is to characterize the system as the density varies through values spanning dense almost solid to relatively mobile granular states. This transition regime encompasses the regime usually thought of as the glass transition, and/or the jamming transition. Motivation for this experiment springs from ideas of a granular glass transition, a related jamming transition, and from recent experiments. In particular, we note recent experiments carried out by our group to characterize this type of transition and also to demonstrate/ characterize fluctuations in slowly sheared systems. These experiments give key insights into what one might expect in near-zero g. In particular, they show that the compressibility of granular systems diverges at a transition or critical point. It is this divergence, coupled to gravity, that makes it extremely difficult if not impossible to

  14. Fluid dynamics: Water flows out of touch

    NASA Astrophysics Data System (ADS)

    Hof, Björn

    2017-01-01

    Superhydrophobic surfaces reduce the frictional drag between water and solid materials, but this effect is often temporary. The realization of sustained drag reduction has applications for water vehicles and pipeline flows.

  15. Flow graphs: interweaving dynamics and structure.

    PubMed

    Lambiotte, R; Sinatra, R; Delvenne, J-C; Evans, T S; Barahona, M; Latora, V

    2011-07-01

    The behavior of complex systems is determined not only by the topological organization of their interconnections but also by the dynamical processes taking place among their constituents. A faithful modeling of the dynamics is essential because different dynamical processes may be affected very differently by network topology. A full characterization of such systems thus requires a formalization that encompasses both aspects simultaneously, rather than relying only on the topological adjacency matrix. To achieve this, we introduce the concept of flow graphs, namely weighted networks where dynamical flows are embedded into the link weights. Flow graphs provide an integrated representation of the structure and dynamics of the system, which can then be analyzed with standard tools from network theory. Conversely, a structural network feature of our choice can also be used as the basis for the construction of a flow graph that will then encompass a dynamics biased by such a feature. We illustrate the ideas by focusing on the mathematical properties of generic linear processes on complex networks that can be represented as biased random walks and their dual consensus dynamics, and show how our framework improves our understanding of these processes.

  16. Information flow dynamics in the brain.

    PubMed

    Rabinovich, Mikhail I; Afraimovich, Valentin S; Bick, Christian; Varona, Pablo

    2012-03-01

    Timing and dynamics of information in the brain is a hot field in modern neuroscience. The analysis of the temporal evolution of brain information is crucially important for the understanding of higher cognitive mechanisms in normal and pathological states. From the perspective of information dynamics, in this review we discuss working memory capacity, language dynamics, goal-dependent behavior programming and other functions of brain activity. In contrast with the classical description of information theory, which is mostly algebraic, brain flow information dynamics deals with problems such as the stability/instability of information flows, their quality, the timing of sequential processing, the top-down cognitive control of perceptual information, and information creation. In this framework, different types of information flow instabilities correspond to different cognitive disorders. On the other hand, the robustness of cognitive activity is related to the control of the information flow stability. We discuss these problems using both experimental and theoretical approaches, and we argue that brain activity is better understood considering information flows in the phase space of the corresponding dynamical model. In particular, we show how theory helps to understand intriguing experimental results in this matter, and how recent knowledge inspires new theoretical formalisms that can be tested with modern experimental techniques.

  17. Information flow dynamics in the brain

    NASA Astrophysics Data System (ADS)

    Rabinovich, Mikhail I.; Afraimovich, Valentin S.; Bick, Christian; Varona, Pablo

    2012-03-01

    Timing and dynamics of information in the brain is a hot field in modern neuroscience. The analysis of the temporal evolution of brain information is crucially important for the understanding of higher cognitive mechanisms in normal and pathological states. From the perspective of information dynamics, in this review we discuss working memory capacity, language dynamics, goal-dependent behavior programming and other functions of brain activity. In contrast with the classical description of information theory, which is mostly algebraic, brain flow information dynamics deals with problems such as the stability/instability of information flows, their quality, the timing of sequential processing, the top-down cognitive control of perceptual information, and information creation. In this framework, different types of information flow instabilities correspond to different cognitive disorders. On the other hand, the robustness of cognitive activity is related to the control of the information flow stability. We discuss these problems using both experimental and theoretical approaches, and we argue that brain activity is better understood considering information flows in the phase space of the corresponding dynamical model. In particular, we show how theory helps to understand intriguing experimental results in this matter, and how recent knowledge inspires new theoretical formalisms that can be tested with modern experimental techniques.

  18. Material Flow During Friction Stir Welds

    NASA Technical Reports Server (NTRS)

    Guerra, M.; McClure, J. C.; Murr, L. E.; Nunes, A. C.; Munafo, Paul M. (Technical Monitor)

    2001-01-01

    The flow of metal during Friction Stir Welding is clarified using a faying surface tracer and a nib frozen in place during welding. It is shown that material is transported in two distinct streams or currents. One stream is a wiping of material from the advancing front side of the nib onto a plug of material that rotates and advances with the nib. The material undergoes a helical motion within the plug that both rotates and advances with the plug and descends in the wash of the threads on the nib and rises on the outer part of the plug. After one or more rotations, this material is sloughed off the plug in the wake of the tool primarily on the advancing side. The second stream of material is an entrainment of material from the retreating side of the nib that fills in between the sloughed off pieces from the advancing side. These two processes produce material with different mechanical properties and the strength of a weld should depend on the relative importance of the processes.

  19. Material Flow During Friction Stir Welds

    NASA Technical Reports Server (NTRS)

    Guerra, M.; McClure, J. C.; Murr, L. E.; Nunes, A. C.; Munafo, Paul M. (Technical Monitor)

    2001-01-01

    The flow of metal during Friction Stir Welding is clarified using a faying surface tracer and a nib frozen in place during welding. It is shown that material is transported in two distinct streams or currents. One stream is a wiping of material from the advancing front side of the nib onto a plug of material that rotates and advances with the nib. The material undergoes a helical motion within the plug that both rotates and advances with the plug and descends in the wash of the threads on the nib and rises on the outer part of the plug. After one or more rotations, this material is sloughed off the plug in the wake of the tool primarily on the advancing side. The second stream of material is an entrainment of material from the retreating side of the nib that fills in between the sloughed off pieces from the advancing side. These two processes produce material with different mechanical properties and the strength of a weld should depend on the relative importance of the processes.

  20. Gold recycling; a materials flow study

    USGS Publications Warehouse

    Amey, Earle B.

    2000-01-01

    This materials flow study includes a description of trends in consumption, loss, and recycling of gold-containing materials in the United States in 1998 in order to illustrate the extent to which gold is presently being recycled and to identify recycling trends. The quantity of gold recycled, as a percent of the apparent supply of gold, was estimated to be about 30 percent. Of the approximately 446 metric tons of gold refined in the United States in 1998, the fabricating and industrial use losses were 3 percent.

  1. Material Flow in Friction Stir Welds

    NASA Astrophysics Data System (ADS)

    Fonda, Richard; Reynolds, Anthony; Feng, C. R.; Knipling, Keith; Rowenhorst, David

    2013-01-01

    Friction stir welding generates periodic features within the weld. These "onion ring" features are associated with variations in both texture and the orientation of that texture along the length of the weld. Analysis of an AA2195 friction stir weld reveals the presence of periodic oscillations between the dominant B and overline{{B}} components of the ideal shear texture, suggesting a periodic reversal in the predominant shear orientation during welding that is inconsistent with current understandings of the friction stir welding process. Microstructural features present in the weld and machine force variations during welding indicate that these textures may arise from the oscillation of an off-centered tool. Such a tool oscillation can generate a periodic extrusion of material around the tool, giving rise to the observed flow features, machine force variations, and reversals of the local shear texture orientations. A new model of material flow during friction stir welding is proposed to explain the observed features.

  2. Shear flow behavior of a dynamically symmetric polymeric bicontinuous microemulsion

    NASA Astrophysics Data System (ADS)

    Zhou, Ning

    2005-03-01

    Soft materials with complex internal structure often exhibit fascinating rheological behavior. For example, under flow the poly (ethylethylene) (PEE)/poly(dimethyl siloxane) (PDMS)/PEE-PDMS polymeric bicontinuous microemulsion (BμE) showed shear-induced macrophase separation.^ 1 This was tentatively attributed to the extreme dynamical asymmetry of the two homopolymers, i.e., their viscosities differed by three orders of magnitude. To understand the role of the dynamic symmetry of a BμE when subjected to shear flow, we have developed a new ternary polymer blend system poly(butylene oxide) (PBO)/ poly(ethylenepropylene) (PEP)/PEP-PBO, which is dynamically almost symmetric. We will report on the shear flow behavior of this new BμE. Reference: [1] Krishnan et al. Phys. Rev. Lett. 2001, 87, 098301

  3. Energy and material flows of megacities.

    PubMed

    Kennedy, Christopher A; Stewart, Iain; Facchini, Angelo; Cersosimo, Igor; Mele, Renata; Chen, Bin; Uda, Mariko; Kansal, Arun; Chiu, Anthony; Kim, Kwi-Gon; Dubeux, Carolina; Lebre La Rovere, Emilio; Cunha, Bruno; Pincetl, Stephanie; Keirstead, James; Barles, Sabine; Pusaka, Semerdanta; Gunawan, Juniati; Adegbile, Michael; Nazariha, Mehrdad; Hoque, Shamsul; Marcotullio, Peter J; González Otharán, Florencia; Genena, Tarek; Ibrahim, Nadine; Farooqui, Rizwan; Cervantes, Gemma; Sahin, Ahmet Duran

    2015-05-12

    Understanding the drivers of energy and material flows of cities is important for addressing global environmental challenges. Accessing, sharing, and managing energy and material resources is particularly critical for megacities, which face enormous social stresses because of their sheer size and complexity. Here we quantify the energy and material flows through the world's 27 megacities with populations greater than 10 million people as of 2010. Collectively the resource flows through megacities are largely consistent with scaling laws established in the emerging science of cities. Correlations are established for electricity consumption, heating and industrial fuel use, ground transportation energy use, water consumption, waste generation, and steel production in terms of heating-degree-days, urban form, economic activity, and population growth. The results help identify megacities exhibiting high and low levels of consumption and those making efficient use of resources. The correlation between per capita electricity use and urbanized area per capita is shown to be a consequence of gross building floor area per capita, which is found to increase for lower-density cities. Many of the megacities are growing rapidly in population but are growing even faster in terms of gross domestic product (GDP) and energy use. In the decade from 2001-2011, electricity use and ground transportation fuel use in megacities grew at approximately half the rate of GDP growth.

  4. Energy and material flows of megacities

    PubMed Central

    Kennedy, Christopher A.; Stewart, Iain; Facchini, Angelo; Cersosimo, Igor; Mele, Renata; Chen, Bin; Uda, Mariko; Kansal, Arun; Chiu, Anthony; Kim, Kwi-gon; Dubeux, Carolina; Lebre La Rovere, Emilio; Cunha, Bruno; Pincetl, Stephanie; Keirstead, James; Barles, Sabine; Pusaka, Semerdanta; Gunawan, Juniati; Adegbile, Michael; Nazariha, Mehrdad; Hoque, Shamsul; Marcotullio, Peter J.; González Otharán, Florencia; Genena, Tarek; Ibrahim, Nadine; Farooqui, Rizwan; Cervantes, Gemma; Sahin, Ahmet Duran

    2015-01-01

    Understanding the drivers of energy and material flows of cities is important for addressing global environmental challenges. Accessing, sharing, and managing energy and material resources is particularly critical for megacities, which face enormous social stresses because of their sheer size and complexity. Here we quantify the energy and material flows through the world’s 27 megacities with populations greater than 10 million people as of 2010. Collectively the resource flows through megacities are largely consistent with scaling laws established in the emerging science of cities. Correlations are established for electricity consumption, heating and industrial fuel use, ground transportation energy use, water consumption, waste generation, and steel production in terms of heating-degree-days, urban form, economic activity, and population growth. The results help identify megacities exhibiting high and low levels of consumption and those making efficient use of resources. The correlation between per capita electricity use and urbanized area per capita is shown to be a consequence of gross building floor area per capita, which is found to increase for lower-density cities. Many of the megacities are growing rapidly in population but are growing even faster in terms of gross domestic product (GDP) and energy use. In the decade from 2001–2011, electricity use and ground transportation fuel use in megacities grew at approximately half the rate of GDP growth. PMID:25918371

  5. Flow and plasticity via nonequilibrium molecular dynamics

    SciTech Connect

    Hoover, W.G.

    1984-06-11

    The viscous flow of fluids and the plastic flow of solids, such as metals, are interesting from both the practical and the theoretical points of view. Atomistic molecular dynamics simulations provide a way of visualizing and understanding these flows in a detailed microscopic way. Simulations are necessarily carried out at relatively high rates of strain. For this reason they are ideally suited to the study of nonlinear flow phenomena: normal stresses induced by shear deformation, stress rotation, and the coupling of stress with heat flow, for instance. The simulations require appropriate boundary conditions, forces, and equations of motion. Newtonian mechanics is relatively inefficient for this simulation task. A modification, Nonequilibrium Molecular Dynamics, has been developed to simulate nonequilibrium flows. By now, many high-strain-rate rheological studies of flowing (viscous) fluids and (plastic) solids have been carried out. Here I describe the new methods used in the simulations and some results obtained in this way. A three-body shear-flow exercise is appended to make these ideas more concrete.

  6. Superelevation and overspill control secondary flow dynamics in submarine channels

    NASA Astrophysics Data System (ADS)

    Dorrell, R. M.; Darby, S. E.; Peakall, J.; Sumner, E. J.; Parsons, D. R.; Wynn, R. B.

    2013-08-01

    In subaerial and submarine meander bends, fluid flow travels downstream in a helical spiral, the structure of which is determined by centrifugal, hydrostatic, baroclinic, and Coriolis forces that together balance frictional stresses generated by the flow. The sense of rotation of this helical flow, and in particular, whether the near bed flow is directed toward the inner bank, e.g., "river-normal," or outer bank, e.g., "river-reversed," is crucial to the morphodynamic evolution of the channel. However, in recent years, there has been a debate over the river-normal or river-reversed nature of submarine flows. Herein, we develop a novel three-dimensional closure of secondary flow dynamics, incorporating downstream convective material transport, to cast new light on this debate. Specifically, we show that the presence of net radial material transport, arising from flow superelevation and overspill, exerts a key control on the near bed orientation of secondary flow in submarine meanders. Our analysis implies that river-reversed flows are likely to be much more prevalent throughout submarine-canyon fan systems than prior studies have indicated.

  7. DYNAMERS: dynamic polymers as self-healing materials.

    PubMed

    Roy, Nabarun; Bruchmann, Bernd; Lehn, Jean-Marie

    2015-06-07

    Importing self-repair or self-healing features into inert materials is of great relevance to material scientists, since it is expected to eliminate the necessity of replenishing a damaged material. Be it material chemistry or more specifically polymer chemistry, such materials have attracted the imagination of both material scientists and chemists. A stroll down the memory lane 70 years back, this might have sounded utopian. However with the current progress in supramolecular chemistry and the emergence of dynamic covalent and non-covalent chemistries, novel perspectives have been opened up to materials science towards the development of dynamic materials (DYNAMATS) and in particular dynamic polymers (DYNAMERS), with the ability to produce such species by custom made designs. Chemistry took giant strides to gain control over the structure and features of materials and, besides basic progress, to apply it for tailor-making matter for applications in our daily life. In that applied perspective, materials science plays a paramount role in shaping our present and in contributing to a sustainable future. The goal is to develop materials, which would be dynamic enough to carry out certain functions as effectively as in biological systems with, however, the freedom to recruit the powers of chemistry on a wider scale, without the limitation imposed by life. Material scientists and in particular polymer chemists may build on chemistry, physics and biology for bridging the gap to develop dynamic materials presenting a wide range of novel functionalities and to convert dreams into reality. In this current review we will focus on developments in the area of dynamic polymers, as a class of dynamic materials presenting self-healing features and, more generally, the ability to undergo adaptation under the effect of physical and/or chemical agents, and thus function as adaptive polymers or ADAPTAMERS.

  8. Disturbance Dynamics in Transitional and Turbulent Flows

    NASA Technical Reports Server (NTRS)

    Grosch, C. E.

    2001-01-01

    The dynamics of an ensemble of linear disturbances with a known probability distribution associated with the initial mode amplitudes are studied in boundary-layer flows through an analysis of the transport equations for the mean disturbance kinetic energy and disturbance energy dissipation rate. Effects of adverse and favorable pressure-gradients on the disturbance dynamics are also included in the analysis. Unlike the fully turbulent regime where nonlinear phase scrambling of the fluctuations affects the flow field in proximity to the wall, the laminar regime fluctuations studied here are influenced across the boundary layer by the solid boundary. In addition to the low Reynolds number, early stage transition regime, the dynamics of these disturbance fields can be related in some respects to the near-wall dynamics of the fully turbulent regime.

  9. Dynamic Fracture in Brittle Materials

    DTIC Science & Technology

    2006-02-01

    of hyperelastic material bodies are: the loss of strong ellipticity for hyperelastic materials characterized by the classical Fung strain energy...everyday life. Understanding the fracture behavior of such materials is of paramount importance. Many fiber reinforced composites utilize polymeric binders...and 2 III). The viscoelasticity is intended to model a polymeric binder matrix while the anisotropy models fiber orientation. 2 Accomplishments

  10. Local dynamic subgrid-scale models in channel flow

    NASA Technical Reports Server (NTRS)

    Cabot, William H.

    1994-01-01

    The dynamic subgrid-scale (SGS) model has given good results in the large-eddy simulation (LES) of homogeneous isotropic or shear flow, and in the LES of channel flow, using averaging in two or three homogeneous directions (the DA model). In order to simulate flows in general, complex geometries (with few or no homogeneous directions), the dynamic SGS model needs to be applied at a local level in a numerically stable way. Channel flow, which is inhomogeneous and wall-bounded flow in only one direction, provides a good initial test for local SGS models. Tests of the dynamic localization model were performed previously in channel flow using a pseudospectral code and good results were obtained. Numerical instability due to persistently negative eddy viscosity was avoided by either constraining the eddy viscosity to be positive or by limiting the time that eddy viscosities could remain negative by co-evolving the SGS kinetic energy (the DLk model). The DLk model, however, was too expensive to run in the pseudospectral code due to a large near-wall term in the auxiliary SGS kinetic energy (k) equation. One objective was then to implement the DLk model in a second-order central finite difference channel code, in which the auxiliary k equation could be integrated implicitly in time at great reduction in cost, and to assess its performance in comparison with the plane-averaged dynamic model or with no model at all, and with direct numerical simulation (DNS) and/or experimental data. Other local dynamic SGS models have been proposed recently, e.g., constrained dynamic models with random backscatter, and with eddy viscosity terms that are averaged in time over material path lines rather than in space. Another objective was to incorporate and test these models in channel flow.

  11. Patterns and dynamics in transitional shear flows

    NASA Astrophysics Data System (ADS)

    Tuckerman, Laurette

    2009-11-01

    One of the greatest mysteries in fluid dynamics is surely transition to turbulence. The classic shear flows -- channel, plane Couette and pipe flow -- while linearly stable, undergo sudden transition to 3D turbulence. In recent years, transition has been attacked with an arsenal of weapons from dynamical systems theory, such as low-dimensional chaos, unstable periodic orbits, heteroclinic connections, fractal basin boundaries. At the same time, 3D physical mechanisms such as streamwise vorticity and streaks have supplanted the 2D picture of linear instability long promoted by Squire's theorem. A striking recent discovery by experimentalists at CEA-Saclay is that large-aspect-ratio plane Couette flow near transition actually takes the form of a steady pattern of wide turbulent and laminar bands, with a fixed angle and wavelength. We have been able to reproduce these remarkable flows in numerical simulations of the Navier-Stokes equations. Simulations display a rich variety of variants of these patterns, including spatio-temporal intermittency, branching and travelling states, and localized states analogous to spots. Because similar patterns have since also been observed in Taylor-Couette, channel and pipe flow, it appears that they are inevitable intermediate states on the route from turbulent to laminar flow in large aspect-ratio shear flows. In addition to their intrinsic interest, these patterns provide clues to the transition to turbulence.

  12. Vesicle dynamics in shear and capillary flows

    NASA Astrophysics Data System (ADS)

    Noguchi, Hiroshi; Gompper, Gerhard

    2005-11-01

    The deformation of vesicles in flow is studied by a mesoscopic simulation technique, which combines multi-particle collision dynamics for the solvent with a dynamically triangulated surface model for the membrane. Shape transitions are investigated both in simple shear flows and in cylindrical capillary flows. We focus on reduced volumes, where the discocyte shape of fluid vesicles is stable, and the prolate shape is metastable. In simple shear flow at low membrane viscosity, the shear induces a transformation from discocyte to prolate with increasing shear rate, while at high membrane viscosity, the shear induces a transformation from prolate to discocyte, or tumbling motion accompanied by oscillations between these two morphologies. In capillary flow, at small flow velocities the symmetry axis of the discocyte is found not to be oriented perpendicular to the cylinder axis. With increasing flow velocity, a transition to a prolate shape occurs for fluid vesicles, while vesicles with shear-elastic membranes (like red blood cells) transform into a coaxial parachute-like shape.

  13. Dynamics of fluid mixing in separated flows

    NASA Astrophysics Data System (ADS)

    Leder, A.

    1991-05-01

    Separated flows at high Re (>103) are highly turbulent. In some situations the turbulence generation and mixing processes associated with flow separation are desirable, e.g., in heat exchangers or in many chemical engineering applications. In others, e.g., stalled airfoils, separation must be avoided as it causes loss in pressure and kinetic energy. To control the phenomenon effectively, physical mechanisms of flow separation and related aspects, such as the growth of flow instabilities in shear layers, the process of vortex formation, and the dynamics of fluid mixing in recirculating flow regions, must be understood. In many cases numerical procedures, e.g., Navier-Stokes calculations including k-ɛ turbulence modeling, fail to predict real physical mechanisms in separated flows.1,2 Separated flows in the lee of bluff bodies have been studied for many years.3,4 However, accurate measurements of the magnitude and direction of velocities and the magnitude of the terms of the Reynolds stress tensor have been restricted by the unsuitability of the hot-wire anemometer in recirculating flows. The development of the pulsed-wire anemometer, flying hot-wire anemometer, and laser-Doppler anemometry (LDA) allows more reliable measurements also in turbulent separated flows.5-8 The aim of this paper is to investigate the dynamics of undisturbed fluid mixing in separated regions of 2-D, incompressible flows with visualization techniques and LDA. Measurements were performed with a vertical flat plate model, mounted in a closed-circuit wind tunnel at low blockage ratio. Because of the noninvasive character, optical techniques like LDA are more suitable to analyze complex fluid motions than pulsed-wire and flying-wire anemometry. The LDA system used to investigate turbulent flow structures consists of a two-channel version operating in backscatter mode and a specifically developed phase detector to extract phase-averaged information from recorded measurement ensembles.9 Endplates

  14. Flow dynamics in a trough blowout

    NASA Astrophysics Data System (ADS)

    Hesp, Patrick A.

    1996-02-01

    The dynamics and geomorphological development of a trough blowout located at Fiona Beach in the Myall Lakes National Park in NSW, Australia are examined. Wind velocities and flow structure were measured utilising an array of miniature Rimco cup anemometers, Gill bi-vane and UVW instruments, and wind vanes. Flow measurements indicate that when the wind approaches the trough blowout parallel to the throat orientation, jets occur both in the deflation basin and along the erosional walls, relative flow deceleration and expansion occur up the depositional lobe, jets are formed over the depositional lobe crest accompanied by downwind flow separation on the leeward side of the lobe, and flow separation and the formation of corkscrew vortices occur over the crests of the erosional walls. Maximum erosion and transport occur up the deflation basin and onto the depositional lobe. Trough blowout morphologies are explained as a function of these flow patterns. When the wind approaches the blowout obliquely, the flow is steered considerably within the blowout. The degree and complexity of topographic steering is dependent on the blowout topography. The flow is usually extremely turbulent and large corkscrew vortices are common. The local topography of a blowout can be very important in determining flow patterns, overall sand transport and blowout evolutionary conditions and paths. Estimates of potential sand transport within the blowout may be up to two orders of magnitude lower than actual rates if remote wind data are used.

  15. Martian Mystery: Do Some Materials Flow Uphill?

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Some of the geological features of Mars defy conventional, or simple, explanations. A recent example is on the wall of a 72 kilometer-wide (45 mile-wide) impact crater in Promethei Terra. The crater (above left) is located at 39oS, 247oW. Its inner walls appear in low-resolution images to be deeply gullied.

    A high resolution Mars Orbiter Camera (MOC) image shows that each gully on the crater's inner wall contains a tongue of material that appears to have flowed (to best see this, click on the icon above right and examine the full image). Ridges and grooves that converge toward the center of each gully and show a pronounced curvature are oriented in a manner that seems to suggest that material has flowed from the top toward the bottom of the picture. This pattern is not unlike pouring pancake batter into a pan... the viscous fluid will form a steep, lobate margin and spread outward across the pan. The ridges and grooves seen in the image are also more reminiscent of the movement of material out and away from a place of confinement, as opposed to the types of features seen when they flow into a more confined area. Mud and lava-flows, and even some glaciers, for the most part behave in this manner. From these observations, and based solely on the appearance, one might conclude that the features formed by moving from the top of the image towards the bottom.

    But this is not the case! The material cannot have flowed from the top towards the bottom of the area seen in the high resolution image (above, right), because the crater floor (which is the lowest area in the image) is at the top of the picture. The location and correct orientation of the high resolution image is shown by a white box in the context frame on the left. Since gravity pulls the material in the gullies downhill not uphill the pattern of ridges and grooves found on these gully-filling materials is puzzling. An explanation may lie in the nature of the material (e.g., how viscous was

  16. Martian Mystery: Do Some Materials Flow Uphill?

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Some of the geological features of Mars defy conventional, or simple, explanations. A recent example is on the wall of a 72 kilometer-wide (45 mile-wide) impact crater in Promethei Terra. The crater (above left) is located at 39oS, 247oW. Its inner walls appear in low-resolution images to be deeply gullied.

    A high resolution Mars Orbiter Camera (MOC) image shows that each gully on the crater's inner wall contains a tongue of material that appears to have flowed (to best see this, click on the icon above right and examine the full image). Ridges and grooves that converge toward the center of each gully and show a pronounced curvature are oriented in a manner that seems to suggest that material has flowed from the top toward the bottom of the picture. This pattern is not unlike pouring pancake batter into a pan... the viscous fluid will form a steep, lobate margin and spread outward across the pan. The ridges and grooves seen in the image are also more reminiscent of the movement of material out and away from a place of confinement, as opposed to the types of features seen when they flow into a more confined area. Mud and lava-flows, and even some glaciers, for the most part behave in this manner. From these observations, and based solely on the appearance, one might conclude that the features formed by moving from the top of the image towards the bottom.

    But this is not the case! The material cannot have flowed from the top towards the bottom of the area seen in the high resolution image (above, right), because the crater floor (which is the lowest area in the image) is at the top of the picture. The location and correct orientation of the high resolution image is shown by a white box in the context frame on the left. Since gravity pulls the material in the gullies downhill not uphill the pattern of ridges and grooves found on these gully-filling materials is puzzling. An explanation may lie in the nature of the material (e.g., how viscous was

  17. Material Flows in an Active Nematic Liquid Crystal

    NASA Astrophysics Data System (ADS)

    Decamp, Stephen; Redner, Gabriel; Baskaran, Aparna; Hagan, Michael; Dogic, Zvonimir

    Active matter systems are composed of energy consuming constituent components which drive far-from-equilibrium dynamics. As such, active materials exhibit energetic states which would be unfavorable in passive, equilibrium materials. We study one such material; an active nematic liquid crystal which exists in a dynamical steady state where +/-1/2 defects are continuously generated and annihilated at a constant rate. The active nematic is composed of micron-sized microtubule filaments which are highly concentrated into a quasi-2D film that resides on an oil-water interface. Kinesin motor proteins drive inter-filament sliding which results in net extensile motion of the microtubule film. Notably, we find a mesophase in which motile +1/2 defects, acquire system-spanning orientational order. Currently, we are tracking material flows generated by the active stresses in the system to measure length scales at which energy is dissipated, and to measure the relation between internally generated flows and bend in the nematic field.

  18. Ultrafast Dynamics of Energetic Materials

    DTIC Science & Technology

    2014-01-23

    Fang, 2011, “The distribution of local enhancement factors in surface enhanced Raman-active substrates and the vibrational dynamics in the liquid phase...3. (invited) “Vibrational energy and molecular thermometers in liquids : Ultrafast IR- Raman spectroscopy”, Brandt C. Pein and Dana D. Dlott, To...simulation with experiment”. J. Phys. Chem. C, 115, pp. 9622–9628 (2011). 13. PhD. Thesis of Jeffrey A. Carter, 2011, “ Dynamics of molecular adsorbates

  19. Dynamic feature analysis in bidirectional pedestrian flows

    NASA Astrophysics Data System (ADS)

    Xiao-Xia, Yang; Winnie, Daamen; Serge, Paul Hoogendoorn; Hai-Rong, Dong; Xiu-Ming, Yao

    2016-02-01

    Analysis of dynamic features of pedestrian flows is one of the most exciting topics in pedestrian dynamics. This paper focuses on the effect of homogeneity and heterogeneity in three parameters of the social force model, namely desired velocity, reaction time, and body size, on the moving dynamics of bidirectional pedestrian flows in the corridors. The speed and its deviation in free flows are investigated. Simulation results show that the homogeneous higher desired speed which is less than a critical threshold, shorter reaction time or smaller body size results in higher speed of flows. The free dynamics is more sensitive to the heterogeneity in desired speed than that in reaction time or in body size. In particular, an inner lane formation is observed in normal lanes. Furthermore, the breakdown probability and the start time of breakdown are focused on. This study reveals that the sizes of homogeneous desired speed, reaction time or body size play more important roles in affecting the breakdown than the heterogeneities in these three parameters do. Project supported jointly by the National Natural Science Foundation of China (Grant No. 61233001) and the Fundamental Research Funds for Central Universities of China (Grant No. 2013JBZ007).

  20. Dynamics of microcapsules in oscillating shear flow

    NASA Astrophysics Data System (ADS)

    Zhao, Mengye; Bagchi, Prosenjit

    2011-11-01

    We present a three-dimensional numerical study on the dynamics of deformable capsules in sinusoidally oscillating shear flow. We consider capsules of spherical and oblate spheroid resting shapes. For spherical resting shapes, we find an identical deformation response during positive and negative vorticities. However, the deformation response becomes unequal and shows complex behavior for nonspherical resting shapes. The average elongation is higher in the retarding phase of the shear flow than in the accelerating phase. Primarily two types of dynamics are observed for nonspherical shapes: a clockwise/counter-clockwise swinging motion in response to the altering flow direction that occurs at both high and low values of shear rate amplitudes, and a continuous/unidirectional tumbling motion that occurs at intermediate values. The unidirectional tumbling motion occurs despite the fact that the time-average vorticity is zero. Such a tumbling motion is accompanied by a continuous tank-treading motion of the membrane in the opposite direction. We obtain phase diagram that shows existence of two critical shear rates and two oscillation frequencies. The unidirectional tumbling motion occurs in the intermediate range, and the clockwise/counter-clockwise swinging motion occurs otherwise. We also find that the dynamics is highly sensitive to the initial condition. A swinging is generally observed when the capsule is released aligned with the extensional or compressional axis of the shear flow, and a tumbling is observed otherwise. These results suggest the possibility of chaotic behavior of cells in time-dependent flows. We provide explanations of such complex dynamics by analyzing the coupling between the shape and angular oscillation and the imposed flow oscillation.

  1. Patterns and flow in frictional fluid dynamics

    PubMed Central

    Sandnes, B.; Flekkøy, E.G.; Knudsen, H.A.; Måløy, K.J.; See, H.

    2011-01-01

    Pattern-forming processes in simple fluids and suspensions have been studied extensively, and the basic displacement structures, similar to viscous fingers and fractals in capillary dominated flows, have been identified. However, the fundamental displacement morphologies in frictional fluids and granular mixtures have not been mapped out. Here we consider Coulomb friction and compressibility in the fluid dynamics, and discover surprising responses including highly intermittent flow and a transition to quasi-continuodynamics. Moreover, by varying the injection rate over several orders of magnitude, we characterize new dynamic modes ranging from stick-slip bubbles at low rate to destabilized viscous fingers at high rate. We classify the fluid dynamics into frictional and viscous regimes, and present a unified description of emerging morphologies in granular mixtures in the form of extended phase diagrams. PMID:21505444

  2. From connected pathway flow to ganglion dynamics

    NASA Astrophysics Data System (ADS)

    Rücker, M.; Berg, S.; Armstrong, R. T.; Georgiadis, A.; Ott, H.; Schwing, A.; Neiteler, R.; Brussee, N.; Makurat, A.; Leu, L.; Wolf, M.; Khan, F.; Enzmann, F.; Kersten, M.

    2015-05-01

    During imbibition, initially connected oil is displaced until it is trapped as immobile clusters. While initial and final states have been well described before, here we image the dynamic transient process in a sandstone rock using fast synchrotron-based X-ray computed microtomography. Wetting film swelling and subsequent snap off, at unusually high saturation, decreases nonwetting phase connectivity, which leads to nonwetting phase fragmentation into mobile ganglia, i.e., ganglion dynamics regime. We find that in addition to pressure-driven connected pathway flow, mass transfer in the oil phase also occurs by a sequence of correlated breakup and coalescence processes. For example, meniscus oscillations caused by snap-off events trigger coalescence of adjacent clusters. The ganglion dynamics occurs at the length scale of oil clusters and thus represents an intermediate flow regime between pore and Darcy scale that is so far dismissed in most upscaling attempts.

  3. Mixing dynamics of cutting and shuffling for granular materials

    NASA Astrophysics Data System (ADS)

    Lueptow, Richard M.; Zaman, Zafir; Yu, Mengqi; Park, Paul P.; Ottino, Julio M.; Umbanhowar, Paul B.

    2016-11-01

    Chaotic dynamics has been shown to play a major role in fluid mixing, but the study of its relevance to granular flows has only recently begun. We utilize a simple 3D geometry, a half-filled spherical tumbler rotated alternately by <= π /2 about two perpendicular horizontal axes, to develop a dynamical systems framework for granular mixing and non-mixing. In these systems, mixing can only occur during flow (from stretching due to shear and from collisional diffusion in the flowing layer) or by material separation intrinsic to the rotation protocol resulting from cutting and shuffling. In X-ray subsurface visualization experiments, surprisingly persistent (O(100) iterations) non-mixing elliptical regions and larger non-mixing barriers occur as predicted by both a continuum model and an idealized theoretical model (with an infinitely thin flowing layer) based on the mathematics of piece-wise isometries. In these models, the stretching in the flowing layer vanishes as the flowing layer thickness decreases to reveal the underlying skeleton of the mixing. This dynamical systems perspective provides insight into mixing and non-mixing phenomena unique to granular materials. Funded by NSF Grant CMMI-1435065.

  4. Flow-induced dynamics of carbon nanotubes.

    PubMed

    Chen, Chao; Xu, Zhiping

    2011-10-05

    The high aspect ratio and bending resilience of a carbon nanotube (CNT) enables it to have remarkable responses to fluid flow. The structural deformation and vibration of a CNT under fluid flow are discussed in this paper, closely tied to their applications in mechanosensing and energy harvesting. We perform molecular dynamics (MD) simulations and a theoretical analysis based on the elastic beam theory, and find that the performance of these applications is critically defined by thermal noise at low flow speeds and flow-induced elastic instabilities at high speeds. We provide a map of operating mechanisms as defined by the properties of both nanostructures and fluid. The results and understanding obtained here could shed some light on the design of nanomechanical devices operating in fluidic environments.

  5. FlowSim/FlowRisk: A code system for studying risk associated with material process flows

    SciTech Connect

    Kaufman, A.M.

    1993-10-01

    The need to study and assess life-cycle risks of Pu release by nuclear warheads during peace time lead to the development of a code suite which could model day to day operations involving nuclear weapons and calculate the associated risk involved in these proceedings. The life-cycle study called LIONSHARE is described in Reference 1. The code that models the flow is called FlowSim. The code that evaluates the associated risk is called FlowRisk. We shall concentrate here on the methodology used by FlowSim in modeling material flows. FlowRisk, mainly a postprocessor of FlowSim runs, will be dealt with in less detail.

  6. Using magma flow indicators to infer flow dynamics in sills

    NASA Astrophysics Data System (ADS)

    Hoyer, Lauren; Watkeys, Michael K.

    2017-03-01

    Fabrics from Anisotropy of Magnetic Susceptibility (AMS) analyses and Shape Preferred Orientation (SPO) of plagioclase are compared with field structures (such as bridge structures, intrusive steps and magma lobes) formed during magma intrusion in Jurassic sills. This is to constrain magma flow directions in the sills of the Karoo Igneous Province along the KwaZulu-Natal North Coast and to show how accurately certain structures predict a magma flow sense, thus improving the understanding of the Karoo sub-volcanic dynamics. The AMS fabrics are derived from magnetite grains and are well constrained, however the SPO results are commonly steeply inclined, poorly constrained and differ to the AMS fabrics. Both techniques resulted in asymmetrical fabrics. Successful relationships were established between the AMS fabric and the long axes of the magma flow indicators, implying adequate magma flow prediction. However, where numerous sill segments merge, either in the form of magma lobes or bridge structures, the coalescence process creates a new fabric between the segments preserving late-stage magma migration between the merged segments, overprinting the initial magma flow direction.

  7. Wind-Flow Dynamics Over a Vineyard

    NASA Astrophysics Data System (ADS)

    Chahine, Ali; Dupont, Sylvain; Sinfort, Carole; Brunet, Yves

    2014-06-01

    Wind-flow dynamics has been extensively studied over horizontally uniform canopies, but agricultural plantations structured in rows such as vineyards have received less attention. Here, the wind flow over a vineyard is studied in neutral stratification from both large-eddy simulation (LES) and in situ measurements. The impact of row structure on the wind dynamics is investigated over a range of wind directions from cross-row to down-row, and a typical range of row aspect ratio (row separation/height ratio). It is shown that the mean flow over a vineyard is similar to that observed in uniform canopies, especially for wind directions from cross-row to diagonal. For down-row winds, the mean flow exhibits noticeable spatial variability across each elementary row-gap pattern, as the wind is channeled in the inter-row. This spatial variability increases with the aspect ratio. With down-row winds the turbulent structures are also more intermittent and generate larger turbulent kinetic energy and momentum flux. The displacement height and roughness length of the vineyard vary with the aspect ratio in a way similar to their variation with canopy density in uniform canopies. Both parameters take smaller values in down-row wind flow, for which the canopy appears more open. The analysis of velocity spectra and autocorrelation functions shows that vineyard canopies share similar features to uniform canopies in terms of turbulent coherent structures, with only minor changes with wind direction.

  8. Dynamic Deformation Properties of Energetic Composite Materials

    DTIC Science & Technology

    2002-12-01

    the dynamic mechanical properties and detonation of energetic materials. It also included some preliminary data on the effect of particle size on the...study of the dynamic mechanical properties and detonation of energetic materials. It also included some preliminary data on the effect of particle size...qualitative only. 33 5. DEFLAGRATION-TO- DETONATION (DDT) STUDIES As part of an on-going programme to investigate the properties of ultrafine energetic

  9. Noisy Nonlinear Dynamics of Vesicles in Flow

    NASA Astrophysics Data System (ADS)

    Abreu, David; Seifert, Udo

    2013-06-01

    We present a model for the dynamics of fluid vesicles in linear flow which consistently includes thermal fluctuations and nonlinear coupling between different modes. At the transition between tank treading and tumbling, we predict a trembling motion which is at odds with the known deterministic motions and for which thermal noise is strongly amplified. In particular, highly asymmetric shapes are observed even though the deterministic flow only allows for axisymmetric ones. Our results explain quantitatively recent experimental observations [Levant and Steinberg, Phys. Rev. Lett. 109, 268103 (2012)PRLTAO0031-9007].

  10. Potential Flow Analysis of Dynamic Ground Effect

    NASA Technical Reports Server (NTRS)

    Feifel, W. M.

    1999-01-01

    Interpretation of some flight test data suggests the presence of a 'dynamic ground effect'. The lift of an aircraft approaching the ground depends on the rate of descent and is lower than the aircraft steady state lift at a same height above the ground. Such a lift deficiency under dynamic conditions could have a serious impact on the overall aircraft layout. For example, the increased pitch angle needed to compensate for the temporary loss in lift would reduce the tail strike margin or require an increase in landing gear length. Under HSR2 an effort is under way to clarify the dynamic ground effect issue using a multi-pronged approach. A dynamic ground effect test has been run in the NASA Langley 14x22 ft wind tunnel. Northup-Grumman is conducting time accurate CFD (Computational Fluid Dynamics) Euler analyses on the National Aerodynamic Simulator facility. Boeing has been using linear potential flow methodology which are thought to provide much needed insight in, physics of this very complex problem. The present report summarizes the results of these potential flow studies.

  11. Continuum modeling of cooperative traffic flow dynamics

    NASA Astrophysics Data System (ADS)

    Ngoduy, D.; Hoogendoorn, S. P.; Liu, R.

    2009-07-01

    This paper presents a continuum approach to model the dynamics of cooperative traffic flow. The cooperation is defined in our model in a way that the equipped vehicle can issue and receive a warning massage when there is downstream congestion. Upon receiving the warning massage, the (up-stream) equipped vehicle will adapt the current desired speed to the speed at the congested area in order to avoid sharp deceleration when approaching the congestion. To model the dynamics of such cooperative systems, a multi-class gas-kinetic theory is extended to capture the adaptation of the desired speed of the equipped vehicle to the speed at the downstream congested traffic. Numerical simulations are carried out to show the influence of the penetration rate of the equipped vehicles on traffic flow stability and capacity in a freeway.

  12. Flow dynamics of spheromaks in SSX

    NASA Astrophysics Data System (ADS)

    Brown, Michael; Cothran, Chris; Cohen, David; Horwitz, Jason; Chaplin, Vernon

    2006-10-01

    We report several new experimental results related to flow dynamics from single dipole-trapped spheromaks and spheromak merging studies at SSX. Local spheromak flow is studied with two Mach probes (r1<=ρi, r2>=ρi) calibrated by time-of-flight with a fast set of magnetic probes at the edge of the device. Both Mach probes feature six ion collectors housed in a boron nitride sheath. The larger Mach probe will ultimately be used in the MST reversed field pinch. Line averaged flow is measured by ion Doppler spectroscopy at the midplane. The SSX IDS instrument measures with 1 μs or better time resolution the width and Doppler shift of the CIII impurity (H plasma) 229.7 nm line to determine the temperature and line- averaged flow velocity. We find axial flows up to 100 km/s during formation of the dipole trapped spheromak. Flow returns at the wall to form a large vortex. We also measure Ti>=50 eV and Te>=20 eV during spheromak merging events after all plasma facing surfaces are cleaned with helium glow discharge conditioning. Te is measured with a 4-channel soft x-ray array. These studies are performed in the prolate 0.4 m diameter, L=0.6 m length copper flux conserver in SSX. The spheromaks are also characterized by a suite of magnetic probe arrays for magnetic structure B(r,t), and interferometry for ne.

  13. Rivulet dynamics at isothermal film flow

    NASA Astrophysics Data System (ADS)

    Bobylev, A. V.; Guzanov, V. V.; Kharlamov, S. M.; Kvon, A. Z.; Markovich, D. M.

    2017-08-01

    Averaged fields of thickness of an isothermal vertically flowing liquid film, obtained by the laserinduced fluorescence method, have been analyzed. The chosen minimum averaging time interval, at which the wave motion is completely averaged, allows one to observe rivulet dynamics in a transverse direction. It is found that short-lived rivulets, which are chains of no less than five to eight waves with similar transverse coordinates, are dominant structures on the film surface at Reynolds number Re > 50.

  14. Dynamics of Layers in Geophysical Flows

    NASA Astrophysics Data System (ADS)

    Hunt, J. C. R.; Galmiche, M.

    The atmosphere and ocean structure consists of horizontal regions with characteristic mean flows, waves and turbulence, separated from each other by semipermanent thin layers such as the tropopause or the thermocline. At the same time, within these regions, thin layers are continually appearing and dissipating such as clouds and fronts, which largely determine the weather. There are also sharp variations in the horizontal structure of flow and physical processes separated by thin layers with sloping or vertical boundaries (e.g. ozone hole and the intertropical convergence zone). We review here how the mechanisms of waves, wave-mean flow interactions, turbulence distortion, turbulence-wave transformation and Coriolis forces, determine the formation, location and dynamics of these layers. This review provides perspectives on current methods of calculating these critical regions in large-scale numerical models used for weather and ocean forecasting, and for climate prediction.

  15. Dynamics of Polymers in Colloidal Flows

    NASA Astrophysics Data System (ADS)

    Chen, Hsieh; Alexander-Katz, Alfredo

    2011-03-01

    This research is motivated by recent studies on the von Willebrand factor (vWF), a large multimeric protein that plays an essential role in the initial stages of blood clotting in blood vessels. Recent experiments substantiated the hypothesis that the vWF is activated by shear stress in blood flow that causes its shape to transform from a compact globule to an extended state, and biological function is obtained only in the extended state. Simple simulations (which only consider a single polymer in bulk shear flow) have successfully reproduced the observed dynamics of the vWF. However, a more refined model is still demanding for the better understanding of the behaviors of this biomolecule in the physiological environments. Here we refine the existing model by adding the drifting colloids into the flows to mimic the presence of the blood cells in the bloodstream. Preliminary result shows that colloids greatly influence the dynamics of the polymers. It is observed that the average extensions of polymers along and perpendicular to the shear flow direction are both increased with the presence of the colloids.

  16. Fluid dynamics of rivulet flow between plates

    NASA Astrophysics Data System (ADS)

    Drenckhan, W.; Ritacco, H.; Saint-Jalmes, A.; Saugey, A.; McGuinness, P.; van der Net, A.; Langevin, D.; Weaire, D.

    2007-10-01

    We present computational and experimental investigations into the fluid dynamics of a narrow stream of surfactant solutions, which descends under gravity between two narrowly spaced, vertical glass plates. Such a "rivulet" is bounded by two liquid/solid and two mobile liquid/gas interfaces, posing fluid dynamic problems of direct relevance to local fluid flow in liquid foams and recently reported meandering phenomena. The rivulet presents a system in which the coupling between the bulk flow and the rheological properties of the gas/liquid interface can be systematically investigated. In particular, it carries the promise of providing an alternative measuring technique for interfacial shear viscosities. We present finite element simulations in conjunction with experiments in order to describe the relationship between the rivulet geometry, the flow field, and the interfacial shear viscosities. We also report on the role of the boundary condition between the liquid-carrying channels (surface Plateau borders) and the thin soap film, which spans the two plates at low flow rates.

  17. Evolving Dynamics of the Supergranular Flow Field

    NASA Astrophysics Data System (ADS)

    De Rosa, M. L.; Lisle, J. P.; Toomre, J.

    2000-05-01

    We study several large (45-degree square) fields of supergranules for as long as they remain visible on the solar disk (about 6 days) to characterize the dynamics of the supergranular flow field and its interaction with surrounding photospheric magnetic field elements. These flow fields are determined by applying correlation tracking methods to time series of mesogranules seen in full-disk SOI-MDI velocity images. We have shown previously that mesogranules observed in this way are systematically advected by the larger scale supergranular flow field in which they are embedded. Applying correlation tracking methods to such time series yields the positions of the supergranular outflows quite well, even for locations close to disk center. These long-duration datasets contain several instances where individual supergranules are recognizable for time scales as long as 50 hours, though most cells persist for about 25 hours that is often quoted as a supergranular lifetime. Many supergranule merging and splitting events are observed, as well as other evolving flow patterns such as lanes of converging and diverging fluid. By comparing the flow fields with the corresponding images of magnetic fields, we confirm the result that small-scale photospheric magnetic field elements are quickly advected to the intercellular lanes to form a network between the supergranular outflows. In addition, we characterize the influence of larger-scale regions of magnetic flux, such as active regions, on the flow fields. Furthermore, we have measured even larger-scale flows by following the motions of the supergranules, but these flow fields contain a high noise component and are somewhat difficult to interpret. This research was supported by NASA through grants NAG 5-8133 and NAG 5-7996, and by NSF through grant ATM-9731676.

  18. Dynamics of individual polymers using microfluidic based microcurvilinear flow.

    PubMed

    Cheng, Chao-Min; Kim, Yongtae; Yang, Jui-Ming; Leuba, Sanford H; Leduc, Philip R

    2009-08-21

    Polymer dynamics play an important role in a diversity of fields including materials science, physics, biology and medicine. The spatiotemporal responses of individual molecules such as biopolymers have been critical to the development of new materials, the expanded understanding of cell structures including cytoskeletal dynamics, and DNA replication. The ability to probe single molecule dynamics however is often limited by the availability of small-scale technologies that can manipulate these systems to uncover highly intricate behaviors. Advances in micro- and nano-scale technologies have simultaneously provided us with valuable tools that can interface with these systems including methods such as microfluidics. Here, we report on the creation of micro-curvilinear flow through a small-scale fluidic approach, which we have been used to impose a flow-based high radial acceleration ( approximately 10(3) g) on individual flexible polymers. We were able to employ this microfluidic-based approach to adjust and control flow velocity and acceleration to observe real-time dynamics of fluorescently labeled lambda-phage DNA molecules in our device. This allowed us to impose mechanical stimulation including stretching and bending on single molecules in localized regimes through a simple and straightforward technology-based method. We found that the flexible DNA molecules exhibited multimodal responses including distinct conformations and controllable curvatures; these characteristics were directly related to both the elongation and bending dynamics dictated by their locations within the curvilinear flow. We analyzed the dynamics of these individual molecules to determine their elongation strain rates and curvatures ( approximately 0.09 microm(-1)) at different locations in this system to probe the individual polymer structural response. These results demonstrate our ability to create high radial acceleration flow and observe real-time dynamic responses applied directly to

  19. Dynamic properties of ceramic materials

    SciTech Connect

    Grady, D.E.

    1995-02-01

    The present study offers new data and analysis on the transient shock strength and equation-of-state properties of ceramics. Various dynamic data on nine high strength ceramics are provided with wave profile measurements, through velocity interferometry techniques, the principal observable. Compressive failure in the shock wave front, with emphasis on brittle versus ductile mechanisms of deformation, is examined in some detail. Extensive spall strength data are provided and related to the theoretical spall strength, and to energy-based theories of the spall process. Failure waves, as a mechanism of deformation in the transient shock process, are examined. Strength and equation-of-state analysis of shock data on silicon carbide, boron carbide, tungsten carbide, silicon dioxide and aluminum nitride is presented with particular emphasis on phase transition properties for the latter two. Wave profile measurements on selected ceramics are investigated for evidence of rate sensitive elastic precursor decay in the shock front failure process.

  20. Recent developments in dynamic testing of materials

    NASA Astrophysics Data System (ADS)

    Gilat, Amos; Seidt, Jeremy D.

    2015-09-01

    New techniques for dynamic characterization of materials that have been developed in the last three years (since the last DYMAT conference in 2012), and results from recent dynamic testing of Inconel 718 are presented. The first development is a dynamic punch test in which three dimensional Digital Image Correlation (DIC) is used to measure the deformation of the rear surface of a specimen as it being penetrated. The second experimental technique that is under development is a dynamic tension experiment in which full-field strain measurement with DIC and full-field temperature measurement are done simultaneously during the test.

  1. Microscale flow dynamics of ribbons and sheets.

    PubMed

    Montenegro-Johnson, Thomas D; Koens, Lyndon; Lauga, Eric

    2017-01-18

    Numerical study of the hydrodynamics of thin sheets and ribbons presents difficulties associated with resolving multiple length scales. To circumvent these difficulties, asymptotic methods have been developed to describe the dynamics of slender fibres and ribbons. However, such theories entail restrictions on the shapes that can be studied, and often break down in regions where standard boundary element methods are still impractical. In this paper we develop a regularised stokeslet method for ribbons and sheets in order to bridge the gap between asymptotic and boundary element methods. The method is validated against the analytical solution for plate ellipsoids, as well as the dynamics of ribbon helices and an experimental microswimmer. We then demonstrate the versatility of this method by calculating the flow around a double helix, and the swimming dynamics of a microscale "magic carpet".

  2. Flow dynamics of a pulsed planar expansion

    NASA Astrophysics Data System (ADS)

    Biennier, Ludovic; Benidar, Abdessamad; Salama, Farid

    2006-08-01

    Plasma expansion sources are popular in molecular spectroscopy and in astrochemistry because they generate cold radicals and ions in detectable amounts. The dynamics of a planar flow generated by a pulsed discharge slit nozzle (PDN) have been numerically investigated for a variety of carrier gases seeded with various molecular species. The determination of the bulk flow characteristics is key to a comprehensive modeling of the plasma that is produced in PDN sources. It is found that the flow is established and stabilized within 75 and 25 μs when Ar and He are used as carrier gases, respectively. The residence time in the inter-electrode active region is found to be considerably shorter with He than with Ar gas carrier. The detection signal observed upon injection of astrochemical species such as polycylic aromatic hydrocarbons (PAHs) in moderate amounts in the carrier gas exhibits a non linear relation with the initial PAH concentration in the reservoir which is governed by the temperature. The local temperature along the flow axis can be predicted from the initial conditions using the isentropic equation. However, the local pressure and density behavior diverge significantly from an isentropic flow. Finally, implications for the characteristics of the plasma expansion are discussed to help design future laboratory simulations.

  3. Flow dynamics in a swirl combustor*

    NASA Astrophysics Data System (ADS)

    Grinstein, Fernando F.; Young, Ted R.; Gutmark, Ephraim J.; Li, Guoqiang; Hsiao, George; Mongia, Hukam C.

    2002-07-01

    A hybrid simulation approach is used to investigate the flow patterns in an axisymmetric swirl combustor configuration. Effective inlet boundary conditions are based on velocity data from Reynolds-averaged Navier-Stokes or actual laboratory measurements at the outlet of a fuel-injector nozzle, and large eddy simulations are used to study the unsteady non-reactive swirl flow dynamics downstream. Case studies ranging from single-swirler to more complex triple-swirler nozzles are presented to emphasize the importance of initial inlet conditions on the behaviour of the swirling flow entering a sudden expansion area, including swirl and radial numbers, inlet length and characteristic velocity profiles. Swirl of sufficient strength produces an adverse pressure gradient which can promote flow reversal or vortex breakdown, and the coupling between swirl and sudden expansion instabilities depends on the relative length of the inlet. The flow is found to be very sensitive to the detailed nature of the velocity radial profiles. The critical challenge of specification of suitable inlet boundary conditions to emulate the turbulent conditions in the laboratory experiments is raised in this context.

  4. Dynamic material modeling in hot forging. Progress report 4

    SciTech Connect

    El-Gizawy, A.S.

    1992-03-01

    A dynamic material model that characterized flow behavior in the workpiece under forging conditions was required to optimize the process and produce defect-free product at minimum cost. Constitutive equations describe the relationship between stress, strain rate, and temperature under forging conditions. Using aluminum alloy 7050, numerous deformation experiments were conducted to fully characterize constitutive equation variables. A thorough description of the experimental arrangement was provided. Flow data and efficiency data were assembled into a three-dimensional plot of temperature vs. strain rate vs. deformation efficiency to produce an efficiency map. The efficiency map provided the information required for optimization of forging process design. The results of dynamic modeling of the material were used in simulating the isothermal forging of a particular part. Recommendations concerning optimum preform design and processing conditions were reported.

  5. Dynamic Multiscale Averaging (DMA) of Turbulent Flow

    SciTech Connect

    Richard W. Johnson

    2012-09-01

    A new approach called dynamic multiscale averaging (DMA) for computing the effects of turbulent flow is described. The new method encompasses multiple applications of temporal and spatial averaging, that is, multiscale operations. Initially, a direct numerical simulation (DNS) is performed for a relatively short time; it is envisioned that this short time should be long enough to capture several fluctuating time periods of the smallest scales. The flow field variables are subject to running time averaging during the DNS. After the relatively short time, the time-averaged variables are volume averaged onto a coarser grid. Both time and volume averaging of the describing equations generate correlations in the averaged equations. These correlations are computed from the flow field and added as source terms to the computation on the next coarser mesh. They represent coupling between the two adjacent scales. Since they are computed directly from first principles, there is no modeling involved. However, there is approximation involved in the coupling correlations as the flow field has been computed for only a relatively short time. After the time and spatial averaging operations are applied at a given stage, new computations are performed on the next coarser mesh using a larger time step. The process continues until the coarsest scale needed is reached. New correlations are created for each averaging procedure. The number of averaging operations needed is expected to be problem dependent. The new DMA approach is applied to a relatively low Reynolds number flow in a square duct segment. Time-averaged stream-wise velocity and vorticity contours from the DMA approach appear to be very similar to a full DNS for a similar flow reported in the literature. Expected symmetry for the final results is produced for the DMA method. The results obtained indicate that DMA holds significant potential in being able to accurately compute turbulent flow without modeling for practical

  6. Flow dynamics around downwelling submarine canyons

    NASA Astrophysics Data System (ADS)

    Spurgin, J. M.; Allen, S. E.

    2014-10-01

    Flow dynamics around a downwelling submarine canyon were analysed with the Massachusetts Institute of Technology general circulation model. Blanes Canyon (northwestern Mediterranean) was used for topographic and initial forcing conditions. Fourteen scenarios were modelled with varying forcing conditions. Rossby and Burger numbers were used to determine the significance of Coriolis acceleration and stratification (respectively) and their impacts on flow dynamics. A new non-dimensional parameter (χ) was introduced to determine the significance of vertical variations in stratification. Some simulations do see brief periods of upwards displacement of water during the 10-day model period; however, the presence of the submarine canyon is found to enhance downwards advection of density in all model scenarios. High Burger numbers lead to negative vorticity and a trapped anticyclonic eddy within the canyon, as well as an increased density anomaly. Low Burger numbers lead to positive vorticity, cyclonic circulation, and weaker density anomalies. Vertical variations in stratification affect zonal jet placement. Under the same forcing conditions, the zonal jet is pushed offshore in more uniformly stratified domains. The offshore jet location generates upwards density advection away from the canyon, while onshore jets generate downwards density advection everywhere within the model domain. Increasing Rossby values across the canyon axis, as well as decreasing Burger values, increase negative vertical flux at shelf break depth (150 m). Increasing Rossby numbers lead to stronger downwards advection of a passive tracer (nitrate), as well as stronger vorticity within the canyon. Results from previous studies are explained within this new dynamic framework.

  7. Flow dynamics around downwelling submarine canyons

    NASA Astrophysics Data System (ADS)

    Spurgin, J. M.; Allen, S. E.

    2014-05-01

    Flow dynamics around a downwelling submarine canyon were analysed with the Massachusetts Institute of Technology general circulation model. Blanes Canyon (Northwest Mediterranean) was used for topographic and initial forcing conditions. Fourteen scenarios were modelled with varying forcing conditions. Rossby number and Burger number were used to determine the significance of Coriolis acceleration and stratification (respectively) and their impacts on flow dynamics. A new non-dimensional parameter (χ) was introduced to determine the significance of vertical variations in stratification. Some simulations do see brief periods of upwards displacement of water during the 10 day model period, however, the presence of the submarine canyon is found to enhance downwards advection of density in all model scenarios. High Burger numbers lead to negative vorticity and a trapped anticyclonic eddy within the canyon, as well as an increased density anomaly. Low Burger numbers lead to positive vorticity, cyclonic circulation and weaker density anomalies. Vertical variations in stratification affect zonal jet placement. Under the same forcing conditions, the zonal jet is pushed offshore in more uniformly stratified domains. Offshore jet location generates upwards density advection away from the canyon, while onshore jets generate downwards density advection everywhere within the model domain. Increasing Rossby values across the canyon axis, as well as decreasing Burger values, increase negative vertical flux at shelf break depth (150 m). Increasing Rossby numbers lead to stronger downwards advection of a passive tracer (nitrate) as well as stronger vorticity within the canyon. Results from previous studies were explained within this new dynamic framework.

  8. Dynamic proliferation assessment in flow cytometry.

    PubMed

    Diermeier-Daucher, Simone; Brockhoff, Gero

    2010-09-01

    Dynamic proliferation assessment via flow cytometry is legitimately supposed to be the most powerful tool for recording cell cycle kinetics in-vitro. The preeminent feature is a single cell-based multi-informative analysis by temporal high-resolution. Flow cytometric approaches are based on labeling of proliferating cells via thymidine substitution by a base analog (e.g., 5-bromo-2'-deoxyuridine, BrdU) that is added to cell cultures either for a short period of time (pulse labeling) or continuously until cell harvesting. This unit describes the alternative use of the thymidine analog 5-ethynyl-2'-deoxyuridine (EdU) in place of BrdU for three different applications: (1) dynamic proliferation assessment by EdU pulse cell labeling; (2) the same approach as (1) but in combination with live/dead cell discrimination; and (3) dynamic cell cycle analysis based on continuous cell labeling with EdU and Hoechst fluorochrome quenching. In contrast to the detection of BrdU incorporation, EdU-positive cells can be identified by taking advantage of click chemistry, which facilitates a simplified and fast cell preparation. Further analysis options but also limitations of the utilization of EdU are discussed.

  9. Characterization of Concrete Material Flow During Projectile Penetration

    NASA Astrophysics Data System (ADS)

    Sobeski, Robert

    The Department of Defense (DoD) has an operational requirement to predict, quickly and accurately, the depth of penetration that a projectile can achieve for a given target and impact scenario. Fast-running analytical models can provide reliable predictions, but they often require the use of one or more dimensionless parameters that are derived from experimental data. These analytical models are continually evolving, and the dimensionless parameters are often adjusted to obtain new analytical models without a true understanding of the change in characteristics of material flow across targets of varying strength and projectile impact velocities. In this dissertation, the penetration of ogive-nose projectiles into concrete targets is investigated using finite element analyses. The Elastic-Plastic Impact Computation (EPIC) code is used to examine the velocity vector fields and their associated direction cosines for high and low-strength concrete target materials during projectile penetration. Two methodologies, referred as Normal Expansion Comparison Methodology (NECM) and Spherical Expansion Comparison Methodology (SECM), are developed in MATLAB to quantify the change in concrete material flow during this short-duration dynamic event. Improved velocity profiles are proposed for better characterization of cavity expansion stresses based on the application of NECM and SECM to EPIC outputs. Structural engineers and model developers working on improving the accuracy of current analytical concrete penetration models and potentially reducing their reliance on fitting parameters will benefit from the findings of this research.

  10. Modeling Tools Predict Flow in Fluid Dynamics

    NASA Technical Reports Server (NTRS)

    2010-01-01

    "Because rocket engines operate under extreme temperature and pressure, they present a unique challenge to designers who must test and simulate the technology. To this end, CRAFT Tech Inc., of Pipersville, Pennsylvania, won Small Business Innovation Research (SBIR) contracts from Marshall Space Flight Center to develop software to simulate cryogenic fluid flows and related phenomena. CRAFT Tech enhanced its CRUNCH CFD (computational fluid dynamics) software to simulate phenomena in various liquid propulsion components and systems. Today, both government and industry clients in the aerospace, utilities, and petrochemical industries use the software for analyzing existing systems as well as designing new ones."

  11. A study of temporal estaurine flow dynamics

    NASA Technical Reports Server (NTRS)

    Mairs, R. L.; Clark, D. K.

    1972-01-01

    Multispectral photography,infrared imagery, image enhancement, and oceanographic, radiometric, and meteorological data were used in the study of temporal estuarine flow dynamics, nearshore circulation, and the resulting dispersal of suspended and dissolved substances introduced from the continent. Repetitive multispectral photography, IR imagery, total radiance and irradiance, water surface temperatures, salinity, total suspended solids, visibility, current velocity, winds, dye implants, and high contrast image enhancement were used to observe and describe water mass boundaries in the nearshore zone and to attempt to establish on what repetitive scale these coastal features should be observed to better understand their behavior. Water mass variability patterns, seen naturally and with the use of dyes, along the North Carolina coast and in the Chesapeake Bay are being studied as synoptic data on the basic dynamics of circulation, flushing, and mixing in coastal waters.

  12. Dynamic flow reattachment on a rotating blade undergoing dynamic stall

    NASA Astrophysics Data System (ADS)

    Raghav, Vrishank; Komerath, Narayanan

    2016-11-01

    A 2-bladed rigid rotor undergoing retreating blade dynamic stall in a low-speed wind tunnel was used to study the 3-dimensional flow reattachment at the end of the dynamic stall cycle. Phase-locked stereoscopic Particle Image Velocimetry was used to capture the velocity field during reattachment. Continuing from prior studies on the inception and progression of 3-D rotating dynamic stall for this test case, phase-resolved, ensemble-averaged results are presented for different values of rotor advance ratio at varying spanwise stations along the blade. The results show the nominal reattachment getting delayed in rotor azimuth with higher advance ratio. At low advance ratio reattachment starts at the leading-edge and progresses towards the trailing-edge with vortex shedding transporting excess vorticity away from the leading-edge. At higher advance ratio, vortex shedding is not observed, instead the vortical structure shrinks in size while the flow close to the trailing-edge appears to reattach. At the higher advance ratio conditions, spanwise vorticity transport appears to be the mechanism to transport excess vorticity away from the leading-edge. The possible causes for a switch in mechanism of vorticity transport are also presented.

  13. Tribological Studies of Dynamic Thermal Seal Materials

    NASA Technical Reports Server (NTRS)

    DeMange, Jeffrey J.; Taylor, Shawn C.

    2016-01-01

    Thermal seals are required on high-speed vehicles in many dynamic applications such as variable inlets in propulsion systems and control surfaces. These seals, often referred to as dynamic thermal seals, must not only mitigate inboard heat transfer, but must also exhibit sufficient durability when scrubbed against mating surfaces. For high-temperature high-speed vehicle applications, the mating surfaces are often made from thermal protection system (TPS) materials, which are typically rougher and more abrasive than TPS materials used at lower temperatures. The high-temperature TPS materials used can include non-ablative (e.g., lightweight porous oxides, ceramic matrix composites) andor ablative systems (e.g., phenolic systems). Due to the increased need for durable high-temperature dynamic seals, researchers working with the NASA Glenn Research Center embarked on an effort to (a) characterize the tribological performance of state-of-the-art thermal seal materials against a variety of TPS materials and (b) develop approaches for improved wear resistance. Tests were conducted using a recently upgraded high-temperature tribometer to assess wear resistance for a variety of tribopairs under multiple conditions. This data will begin to frame the challenges of using these materials and eventually permit an improved ability to design and implement these critical TPS components.

  14. Measurements of granular flow dynamics with high speed digital images

    SciTech Connect

    Lee, J.

    1994-12-31

    The flow of granular materials is common to many industrial processes. This dissertation suggests and validates image processing algorithms applied to high speed digital images to measure the dynamics (velocity, temperature and volume fraction) of dry granular solids flowing down an inclined chute under the action of gravity. Glass and acrylic particles have been used as granular solids in the experiment. One technique utilizes block matching for spatially averaged velocity measurements of the glass particles. This technique is compared with the velocity measurement using an optic probe which is a conventional granular flow velocity measurement device. The other technique for measuring the velocities of individual acrylic particles is developed with correspondence using a Hopfield network. This technique first locates the positions of particles with pattern recognition techniques, followed by a clustering technique, which produces point patterns. Also, several techniques are compared for particle recognition: synthetic discriminant function (SDF), minimum average correlation energy (MACE) filter, modified minimum average correlation energy (MMACE) filter and variance normalized correlation. The author proposes an MMACE filter which improves generalization of the MACE filter by adjusting the amount of averaged spectrum of training images in the spectrum whitening stages of the MACE filter. Variance normalized correlation is applied to measure the velocity and temperature of flowing glass particles down the inclined chute. The measurements are taken for the steady and wavy flow and qualitatively compared with a theoretical model of granular flow.

  15. Visualization of vortical flows in computational fluid dynamics

    NASA Astrophysics Data System (ADS)

    Volkov, K. N.; Emel'yanov, V. N.; Teterina, I. V.; Yakovchuk, M. S.

    2017-08-01

    The concepts and methods of the visual representation of fluid dynamics computations of vortical flows are studied. Approaches to the visualization of vortical flows based on the use of various definitions of a vortex and various tests for its identification are discussed. Examples of the visual representation of solutions to some fluid dynamics problems related to the computation of vortical flows in jets, channels, and cavities and of the computation of separated flows occurring in flows around bodies of various shapes are discussed.

  16. Experiments showing dynamics of materials interfaces

    SciTech Connect

    Benjamin, R.F.

    1997-02-01

    The discipline of materials science and engineering often involves understanding and controlling properties of interfaces. The authors address the challenge of educating students about properties of interfaces, particularly dynamic properties and effects of unstable interfaces. A series of simple, inexpensive, hands-on activities about fluid interfaces provides students with a testbed to develop intuition about interface dynamics. The experiments highlight the essential role of initial interfacial perturbations in determining the dynamic response of the interface. The experiments produce dramatic, unexpected effects when initial perturbations are controlled and inhibited. These activities help students to develop insight about unstable interfaces that can be applied to analogous problems in materials science and engineering. The lessons examine ``Rayleigh-Taylor instability,`` an interfacial instability that occurs when a higher-density fluid is above a lower-density fluid.

  17. Blood flow dynamics in heart failure

    NASA Technical Reports Server (NTRS)

    Shoemaker, J. K.; Naylor, H. L.; Hogeman, C. S.; Sinoway, L. I.

    1999-01-01

    BACKGROUND: Exercise intolerance in heart failure (HF) may be due to inadequate vasodilation, augmented vasoconstriction, and/or altered muscle metabolic responses that lead to fatigue. METHODS AND RESULTS: Vascular and metabolic responses to rhythmic forearm exercise were tested in 9 HF patients and 9 control subjects (CTL) during 2 protocols designed to examine the effect of HF on the time course of oxygen delivery versus uptake (protocol 1) and on vasoconstriction during exercise with 50 mm Hg pressure about the forearm to evoke a metaboreflex (protocol 2). In protocol 1, venous lactate and H+ were greater at 4 minutes of exercise in HF versus CTL (P<0.05) despite similar blood flow and oxygen uptake responses. In protocol 2, mean arterial pressure increased similarly in each group during ischemic exercise. In CTL, forearm blood flow and vascular conductance were similar at the end of ischemic and ambient exercise. In HF, forearm blood flow and vascular conductance were reduced during ischemic exercise compared with the ambient trial. CONCLUSIONS: Intrinsic differences in skeletal muscle metabolism, not vasodilatory dynamics, must account for the augmented glycolytic metabolic responses to moderate-intensity exercise in class II and III HF. The inability to increase forearm vascular conductance during ischemic handgrip exercise, despite a normal pressor response, suggests that enhanced vasoconstriction of strenuously exercising skeletal muscle contributes to exertional fatigue in HF.

  18. Blood flow dynamics in heart failure

    NASA Technical Reports Server (NTRS)

    Shoemaker, J. K.; Naylor, H. L.; Hogeman, C. S.; Sinoway, L. I.

    1999-01-01

    BACKGROUND: Exercise intolerance in heart failure (HF) may be due to inadequate vasodilation, augmented vasoconstriction, and/or altered muscle metabolic responses that lead to fatigue. METHODS AND RESULTS: Vascular and metabolic responses to rhythmic forearm exercise were tested in 9 HF patients and 9 control subjects (CTL) during 2 protocols designed to examine the effect of HF on the time course of oxygen delivery versus uptake (protocol 1) and on vasoconstriction during exercise with 50 mm Hg pressure about the forearm to evoke a metaboreflex (protocol 2). In protocol 1, venous lactate and H+ were greater at 4 minutes of exercise in HF versus CTL (P<0.05) despite similar blood flow and oxygen uptake responses. In protocol 2, mean arterial pressure increased similarly in each group during ischemic exercise. In CTL, forearm blood flow and vascular conductance were similar at the end of ischemic and ambient exercise. In HF, forearm blood flow and vascular conductance were reduced during ischemic exercise compared with the ambient trial. CONCLUSIONS: Intrinsic differences in skeletal muscle metabolism, not vasodilatory dynamics, must account for the augmented glycolytic metabolic responses to moderate-intensity exercise in class II and III HF. The inability to increase forearm vascular conductance during ischemic handgrip exercise, despite a normal pressor response, suggests that enhanced vasoconstriction of strenuously exercising skeletal muscle contributes to exertional fatigue in HF.

  19. Blood flow dynamics in the snake spectacle.

    PubMed

    van Doorn, Kevin; Sivak, Jacob G

    2013-11-15

    The eyes of snakes are shielded beneath a layer of transparent integument referred to as the 'reptilian spectacle'. Well adapted to vision by virtue of its optical transparency, it nevertheless retains one characteristic of the integument that would otherwise prove detrimental to vision: its vascularity. Given the potential consequence of spectacle blood vessels on visual clarity, one might expect adaptations to have evolved that mitigate their negative impact. Earlier research demonstrated an adaptation to their spatial layout in only one species to reduce the vessels' density in the region serving the foveal and binocular visual fields. Here, we present a study of spectacle blood flow dynamics and provide evidence of a mechanism to mitigate the spectacle blood vessels' deleterious effect on vision by regulation of blood flow through them. It was found that when snakes are at rest and undisturbed, spectacle vessels undergo cycles of dilation and constriction, such that the majority of the time the vessels are fully constricted, effectively removing them from the visual field. When snakes are presented with a visual threat, spectacle vessels constrict and remain constricted for longer periods than occur during the resting cycles, thus guaranteeing the best possible visual capabilities in times of need. Finally, during the snakes' renewal phase when they are generating a new stratum corneum, the resting cycle is abolished, spectacle vessels remain dilated and blood flow remains strong and continuous. The significance of these findings in terms of the visual capabilities and physiology of snakes is discussed.

  20. Parametric Flow Visualization of Dynamic Roughness Effects

    NASA Astrophysics Data System (ADS)

    Jakkali, Vinay

    The ever growing need in the aircraft industry to enhance the performance of a flight vehicle has led to active areas of research which focus on the control of the local boundary layer by both passive and active methods. An effective flow control mechanism can improve the performance of a flight vehicle in various ways, one of which is eliminating boundary layer separation. To be effective the mechanism not only needs to control the boundary layer as desired, but also use less energy than the resulting energy savings. In this study, the effectiveness of an active flow control technique known as dynamic roughness (DR) has been explored to eliminate the laminar separation bubble near the leading edge and also to eliminate the stall on a NACA 0012 airfoil wing. As opposed to static roughness, dynamic roughness utilizes small time-dependent deforming elements or humps with displacement amplitudes that are on the order of the local boundary layer height to energize the local boundary layer. DR is primarily characterized by the maximum amplitude and operating frequency. A flow visualization study was conducted on a 2D NACA 0012 airfoil model at different angles of attack, and also varying the Reynolds number and DR actuation frequency with fixed maximum DR amplitude. The experimental results from this study suggests that DR is an effective method of reattaching a totally separated boundary layer. In addition, this study discusses some of the fundamental physics behind the working of DR and proposes some non-dimensional terms that may help to explain the driving force behind the mechanism.

  1. The behavior of a macroscopic granular material in vortex flow

    NASA Astrophysics Data System (ADS)

    Nishikawa, Asami

    A granular material is defined as a collection of discrete particles such as powder and grain. Granular materials display a large number of complex behaviors. In this project, the behavior of macroscopic granular materials under tornado-like vortex airflow, with varying airflow velocity, was observed and studied. The experimental system was composed of a 9.20-cm inner diameter acrylic pipe with a metal mesh bottom holding the particles, a PVC duct, and an airflow source controlled by a variable auto-transformer, and a power-meter. A fixed fan blade was attached to the duct's inner wall to create a tornado-like vortex airflow from straight flow. As the airflow velocity was increased gradually, the behavior of a set of same-diameter granular materials was observed. The observed behaviors were classified into six phases based on the macroscopic mechanical dynamics. Through this project, we gained insights on the significant parameters for a computer simulation of a similar system by Heath Rice [5]. Comparing computationally and experimentally observed phase diagrams, we can see similar structure. The experimental observations showed the effect of initial arrangement of particles on the phase transitions.

  2. Flow enhancement in nanotubes of different materials and lengths.

    PubMed

    Ritos, Konstantinos; Mattia, Davide; Calabrò, Francesco; Reese, Jason M

    2014-01-07

    The high water flow rates observed in carbon nanotubes (CNTs) have previously been attributed to the unfavorable energetic interaction between the liquid and the graphitic walls of the CNTs. This paper reports molecular dynamics simulations of water flow in carbon, boron nitride, and silicon carbide nanotubes that show the effect of the solid-liquid interactions on the fluid flow. Alongside an analytical model, these results show that the flow enhancement depends on the tube's geometric characteristics and the solid-liquid interactions.

  3. Flow enhancement in nanotubes of different materials and lengths

    SciTech Connect

    Ritos, Konstantinos; Mattia, Davide; Calabrò, Francesco; Reese, Jason M.

    2014-01-07

    The high water flow rates observed in carbon nanotubes (CNTs) have previously been attributed to the unfavorable energetic interaction between the liquid and the graphitic walls of the CNTs. This paper reports molecular dynamics simulations of water flow in carbon, boron nitride, and silicon carbide nanotubes that show the effect of the solid-liquid interactions on the fluid flow. Alongside an analytical model, these results show that the flow enhancement depends on the tube's geometric characteristics and the solid-liquid interactions.

  4. Fluid flow dynamics under location uncertainty

    NASA Astrophysics Data System (ADS)

    Mémin, Etienne

    2014-03-01

    We present a derivation of a stochastic model of Navier Stokes equations that relies on a decomposition of the velocity fields into a differentiable drift component and a time uncorrelated uncertainty random term. This type of decomposition is reminiscent in spirit to the classical Reynolds decomposition. However, the random velocity fluctuations considered here are not differentiable with respect to time, and they must be handled through stochastic calculus. The dynamics associated with the differentiable drift component is derived from a stochastic version of the Reynolds transport theorem. It includes in its general form an uncertainty dependent "subgrid" bulk formula that cannot be immediately related to the usual Boussinesq eddy viscosity assumption constructed from thermal molecular agitation analogy. This formulation, emerging from uncertainties on the fluid parcels location, explains with another viewpoint some subgrid eddy diffusion models currently used in computational fluid dynamics or in geophysical sciences and paves the way for new large-scales flow modelling. We finally describe an applications of our formalism to the derivation of stochastic versions of the Shallow water equations or to the definition of reduced order dynamical systems.

  5. Toward sustainable material usage: evaluating the importance of market motivated agency in modeling material flows.

    PubMed

    Gaustad, Gabrielle; Olivetti, Elsa; Kirchain, Randolph

    2011-05-01

    Increasing recycling will be a key strategy for moving toward sustainable materials usage. There are many barriers to increasing recycling, including quality issues in the scrap stream. Repeated recycling can compound this problem through the accumulation of tramp elements over time. This paper explores the importance of capturing recycler decision-making in accurately modeling accumulation and the value of technologies intended to mitigate it. A method was developed combining dynamic material flow analysis with allocation of those materials into production portfolios using blending models. Using this methodology, three scrap allocation methods were explored in the context of a case study of aluminum use: scrap pooling, pseudoclosed loop, and market-based. Results from this case analysis suggest that market-driven decisions and upgrading technologies can partially mitigate the negative impact of accumulation on scrap utilization, thereby increasing scrap use and reducing greenhouse gas emissions. A market-based allocation method for modeling material flows suggests a higher value for upgrading strategies compared to a pseudoclosed loop or pooling allocation method for the scenarios explored.

  6. Erosion and flow of hydrophobic granular materials

    NASA Astrophysics Data System (ADS)

    Utter, Brian; Benns, Thomas; Foltz, Benjamin; Mahler, Joseph

    2015-03-01

    We experimentally investigate submerged granular flows of hydrophobic and hydrophilic grains both in a rotating drum geometry and under erosion by a surface water flow. While slurry and suspension flows are common in nature and industry, effects of surface chemistry on flow behavior have received relatively little attention. In the rotating drum, we use varying concentrations of hydrophobic and hydrophilic grains of sand submerged in water rotated at a constant angular velocity. Sequential images of the resulting avalanches are taken and analyzed. High concentrations of hydrophobic grains result in an effectively cohesive interaction between the grains forming aggregates, with aggregate size and repose angle increasing with hydrophobic concentration. However, the formation and nature of the aggregates depends significantly on the presence of air in the system. We present results from a related experiment on erosion by a surface water flow designed to characterize the effects of heterogeneous granular surfaces on channelization and erosion.

  7. Erosion and flow of hydrophobic granular materials

    NASA Astrophysics Data System (ADS)

    Utter, Brian; Benns, Thomas; Mahler, Joseph

    2013-11-01

    We experimentally investigate submerged granular flows of hydrophobic and hydrophilic grains both in a rotating drum geometry and under erosion by a surface water flow. While slurry and suspension flows are common in nature and industry, effects of surface chemistry on flow behavior have received relatively little attention. In the rotating drum , we use varying concentrations of hydrophobic and hydrophilic grains of sand submerged in water rotated at a constant angular velocity. Sequential images of the resulting avalanches are taken and analyzed. High concentrations of hydrophobic grains result in an effectively cohesive interaction between the grains forming aggregates, with aggregate size and repose angle increasing with hydrophobic concentration. However, the formation and nature of the aggregates depends significantly on the presence of air in the system. We present results from a related experiment on erosion by a surface water flow designed to characterize the effects of heterogeneous granular surfaces on channelization and erosion. Supported by NSF CBET Award 1067598.

  8. High Speed Dynamics in Brittle Materials

    NASA Astrophysics Data System (ADS)

    Hiermaier, Stefan

    2015-06-01

    Brittle Materials under High Speed and Shock loading provide a continuous challenge in experimental physics, analysis and numerical modelling, and consequently for engineering design. The dependence of damage and fracture processes on material-inherent length and time scales, the influence of defects, rate-dependent material properties and inertia effects on different scales make their understanding a true multi-scale problem. In addition, it is not uncommon that materials show a transition from ductile to brittle behavior when the loading rate is increased. A particular case is spallation, a brittle tensile failure induced by the interaction of stress waves leading to a sudden change from compressive to tensile loading states that can be invoked in various materials. This contribution highlights typical phenomena occurring when brittle materials are exposed to high loading rates in applications such as blast and impact on protective structures, or meteorite impact on geological materials. A short review on experimental methods that are used for dynamic characterization of brittle materials will be given. A close interaction of experimental analysis and numerical simulation has turned out to be very helpful in analyzing experimental results. For this purpose, adequate numerical methods are required. Cohesive zone models are one possible method for the analysis of brittle failure as long as some degree of tension is present. Their recent successful application for meso-mechanical simulations of concrete in Hopkinson-type spallation tests provides new insight into the dynamic failure process. Failure under compressive loading is a particular challenge for numerical simulations as it involves crushing of material which in turn influences stress states in other parts of a structure. On a continuum scale, it can be modeled using more or less complex plasticity models combined with failure surfaces, as will be demonstrated for ceramics. Models which take microstructural

  9. Dynamics of a fluid flow on Mars: Lava or mud?

    NASA Astrophysics Data System (ADS)

    Wilson, Lionel; Mouginis-Mark, Peter J.

    2014-05-01

    A distinctive flow deposit southwest of Cerberus Fossae on Mars is analyzed. The flow source is a ∼20 m deep, ∼12 × 1.5 km wide depression within a yardang associated with the Medusae Fossae Formation. The flow traveled for ∼40 km following topographic lows to leave a deposit on average 3-4 km wide. The surface morphology of the deposit suggests that it was produced by the emplacement of a fluid flowing in a laminar fashion and possessing a finite yield strength. We use topographic data from a digital elevation model (DEM) to model the dynamics of the motion and infer that the fluid had a Bingham rheology with a plastic viscosity of ∼1 Pa s and a yield strength of ∼185 Pa. Although the low viscosity is consistent with the properties of komatiite-like lava, the combination of values of viscosity and yield strength, as well as the surface morphology of the flow, suggests that this was a mud flow. Comparison with published experimental data implies a solids content close to 60% by volume and a grain size dominated by silt-size particles. Comparison of the ∼1.5 km3 deposit volume with the ∼0.03 km3 volume of the source depression implies that ∼98% of the flow material was derived from depth in the crust. There are similarities between the deposit studied here, which we infer to be mud, and other flow deposits on Mars currently widely held to be lavas. This suggests that a re-appraisal of many of these deposits is now in order.

  10. Fluid dynamics of unsteady separated flow. I - Bodies of revolution

    NASA Technical Reports Server (NTRS)

    Ericsson, L. E.; Reding, J. P.

    1986-01-01

    An analytic method is described that uses static experimental data to predict the separated flow effect on rigid and elastic aerospace-vehicle dynamics. Spike-induced flow separation, nose-induced flow separation, shock-induced flow separation, and base flow effects are studied. It is observed that the time lag occurring before a change of flow conditions causes a statically stabilizing load to produce negative aerodynanamic damping and an unstabilizing load causes a positive aerodynamic damping. The time-lagged quasi-steady theory predictions are compared with dynamic experimental results and good correlation exists for a large variety of vehicle geometries and types of flow separation.

  11. Dynamic Flow Management Problems in Air Transportation

    NASA Technical Reports Server (NTRS)

    Patterson, Sarah Stock

    1997-01-01

    In 1995, over six hundred thousand licensed pilots flew nearly thirty-five million flights into over eighteen thousand U.S. airports, logging more than 519 billion passenger miles. Since demand for air travel has increased by more than 50% in the last decade while capacity has stagnated, congestion is a problem of undeniable practical significance. In this thesis, we will develop optimization techniques that reduce the impact of congestion on the national airspace. We start by determining the optimal release times for flights into the airspace and the optimal speed adjustment while airborne taking into account the capacitated airspace. This is called the Air Traffic Flow Management Problem (TFMP). We address the complexity, showing that it is NP-hard. We build an integer programming formulation that is quite strong as some of the proposed inequalities are facet defining for the convex hull of solutions. For practical problems, the solutions of the LP relaxation of the TFMP are very often integral. In essence, we reduce the problem to efficiently solving large scale linear programming problems. Thus, the computation times are reasonably small for large scale, practical problems involving thousands of flights. Next, we address the problem of determining how to reroute aircraft in the airspace system when faced with dynamically changing weather conditions. This is called the Air Traffic Flow Management Rerouting Problem (TFMRP) We present an integrated mathematical programming approach for the TFMRP, which utilizes several methodologies, in order to minimize delay costs. In order to address the high dimensionality, we present an aggregate model, in which we formulate the TFMRP as a multicommodity, integer, dynamic network flow problem with certain side constraints. Using Lagrangian relaxation, we generate aggregate flows that are decomposed into a collection of flight paths using a randomized rounding heuristic. This collection of paths is used in a packing integer

  12. Quantitative flow analysis of swimming dynamics with coherent Lagrangian vortices.

    PubMed

    Huhn, F; van Rees, W M; Gazzola, M; Rossinelli, D; Haller, G; Koumoutsakos, P

    2015-08-01

    Undulatory swimmers flex their bodies to displace water, and in turn, the flow feeds back into the dynamics of the swimmer. At moderate Reynolds number, the resulting flow structures are characterized by unsteady separation and alternating vortices in the wake. We use the flow field from simulations of a two-dimensional, incompressible viscous flow of an undulatory, self-propelled swimmer and detect the coherent Lagrangian vortices in the wake to dissect the driving momentum transfer mechanisms. The detected material vortex boundary encloses a Lagrangian control volume that serves to track back the vortex fluid and record its circulation and momentum history. We consider two swimming modes: the C-start escape and steady anguilliform swimming. The backward advection of the coherent Lagrangian vortices elucidates the geometry of the vorticity field and allows for monitoring the gain and decay of circulation and momentum transfer in the flow field. For steady swimming, momentum oscillations of the fish can largely be attributed to the momentum exchange with the vortex fluid. For the C-start, an additionally defined jet fluid region turns out to balance the high momentum change of the fish during the rapid start.

  13. Quantitative flow analysis of swimming dynamics with coherent Lagrangian vortices

    NASA Astrophysics Data System (ADS)

    Huhn, F.; van Rees, W. M.; Gazzola, M.; Rossinelli, D.; Haller, G.; Koumoutsakos, P.

    2015-08-01

    Undulatory swimmers flex their bodies to displace water, and in turn, the flow feeds back into the dynamics of the swimmer. At moderate Reynolds number, the resulting flow structures are characterized by unsteady separation and alternating vortices in the wake. We use the flow field from simulations of a two-dimensional, incompressible viscous flow of an undulatory, self-propelled swimmer and detect the coherent Lagrangian vortices in the wake to dissect the driving momentum transfer mechanisms. The detected material vortex boundary encloses a Lagrangian control volume that serves to track back the vortex fluid and record its circulation and momentum history. We consider two swimming modes: the C-start escape and steady anguilliform swimming. The backward advection of the coherent Lagrangian vortices elucidates the geometry of the vorticity field and allows for monitoring the gain and decay of circulation and momentum transfer in the flow field. For steady swimming, momentum oscillations of the fish can largely be attributed to the momentum exchange with the vortex fluid. For the C-start, an additionally defined jet fluid region turns out to balance the high momentum change of the fish during the rapid start.

  14. Influence of surface clinker on the crustal structures and dynamics of 'a'ā lava flows

    NASA Astrophysics Data System (ADS)

    Applegarth, L. J.; James, M. R.; van Wyk de Vries, B.; Pinkerton, H.

    2010-07-01

    Surface structures on 'a'ā and blocky lavas reflect the internal flow dynamics during emplacement and also influence the dynamics of developing flows. To investigate the effects of brittle, clinkery 'a'ā flow crusts on flow dynamics and surface structures, we conducted sand and silicone laboratory experiments that simulated the advance of lava into a preexisting channelized flow with a surface crust. Experiments carried out with relatively thin crusts produced apparently ductile surface deformation structures, while thick crusts behaved dominantly in a brittle manner. Increased crustal thickness led to increased strength under compression but favored more disruption under tension, as the flow core welled up through tensile fractures, entraining crustal material. At lava flow fronts, upwelling and entrainment would increase heat losses by radiation and advection, respectively, resulting in a positive-feedback cooling loop. Fracturing caused heterogeneous crustal distribution near the flow front, which resulted in lobate flow advance, despite the absence of the viscoelastic layer that has previously been inferred as the primary control on flow advance and lobe formation. We therefore conclude that the influence of a purely brittle crust on the dynamics and surface morphologies of lava flows is more significant than often thought. All of the surface structures produced in the experiments have been observed on lavas or glaciers and many also on landslides and debris flows, suggesting the results can assist in the understanding of a range of natural flows.

  15. Dynamic failure in two-phase materials

    SciTech Connect

    Fensin, S. J.; Walker, E. K.; Cerreta, E. K.; Trujillo, C. P.; Martinez, D. T.; Gray, G. T.

    2015-12-21

    Previous experimental research has shown that microstructural features such as interfaces, inclusions, vacancies, and heterogeneities can all act as voidnucleation sites. However, it is not well understood how important these interfaces are to damage evolution and failure as a function of the surrounding parentmaterials. In this work, we present results on three different polycrystallinematerials: (1) Cu, (2) Cu-24 wt. %Ag, and (3) Cu-15 wt. %Nb which were studied to probe the influence of bi-metal interfaces onvoidnucleation and growth. These materials were chosen due to the range of difference in structure and bulk properties between the two phases. The initial results suggest that when there are significant differences between the bulk properties (for example: stacking fault energy, melting temperature, etc.) the type of interface between the two parent materials does not principally control the damage nucleation and growth process. Rather, it is the “weaker” material that dictates the dynamic spall strength of the overall two-phase material.

  16. Optical dynamic deformation measurements at translucent materials.

    PubMed

    Philipp, Katrin; Koukourakis, Nektarios; Kuschmierz, Robert; Leithold, Christoph; Fischer, Andreas; Czarske, Jürgen

    2015-02-15

    Due to their high stiffness-to-weight ratio, glass fiber-reinforced polymers are an attractive material for rotors, e.g., in the aerospace industry. A fundamental understanding of the material behavior requires non-contact, in-situ dynamic deformation measurements. The high surface speeds and particularly the translucence of the material limit the usability of conventional optical measurement techniques. We demonstrate that the laser Doppler distance sensor provides a powerful and reliable tool for monitoring radial expansion at fast rotating translucent materials. We find that backscattering in material volume does not lead to secondary signals as surface scattering results in degradation of the measurement volume inside the translucent medium. This ensures that the acquired signal contains information of the rotor surface only, as long as the sample surface is rough enough. Dynamic deformation measurements of fast-rotating fiber-reinforced polymer composite rotors with surface speeds of more than 300 m/s underline the potential of the laser Doppler sensor.

  17. Turbulence dynamics in unsteady atmospheric flows

    NASA Astrophysics Data System (ADS)

    Momen, Mostafa; Bou-Zeid, Elie

    2016-11-01

    Unsteady pressure-gradient forcing in geophysical flows challenges the quasi-steady state assumption, and can strongly impact the mean wind and higher-order turbulence statistics. Under such conditions, it is essential to understand when turbulence is in quasi-equilibrium, and what are the implications of unsteadiness on flow characteristics. The present study focuses on the unsteady atmospheric boundary layer (ABL) where pressure gradient, Coriolis, buoyancy, and friction forces interact. We perform a suite of LES with variable pressure-gradient. The results indicate that the dynamics are mainly controlled by the relative magnitudes of three time scales: Tinertial, Tturbulence, and Tforcing. It is shown that when Tf Tt , the turbulence is no longer in a quasi-equilibrium state due to highly complex mean-turbulence interactions; consequently, the log-law and turbulence closures are no longer valid in these conditions. However, for longer and, surprisingly, for shorter forcing times, quasi-equilibrium is maintained. Varying the pressure gradient in the presence of surface buoyancy fluxes primarily influences the buoyant destruction in the stable ABLs, while under unstable conditions it mainly influences the transport terms. NSF-PDM under AGS-10266362. Cooperative Institute for Climate Science, NOAA-Princeton University under NA08OAR4320752. Simulations performed at NCAR, and Della server at Princeton University.

  18. Fluid flow dynamics in MAS systems

    NASA Astrophysics Data System (ADS)

    Wilhelm, Dirk; Purea, Armin; Engelke, Frank

    2015-08-01

    The turbine system and the radial bearing of a high performance magic angle spinning (MAS) probe with 1.3 mm-rotor diameter has been analyzed for spinning rates up to 67 kHz. We focused mainly on the fluid flow properties of the MAS system. Therefore, computational fluid dynamics (CFD) simulations and fluid measurements of the turbine and the radial bearings have been performed. CFD simulation and measurement results of the 1.3 mm-MAS rotor system show relatively low efficiency (about 25%) compared to standard turbo machines outside the realm of MAS. However, in particular, MAS turbines are mainly optimized for speed and stability instead of efficiency. We have compared MAS systems for rotor diameter of 1.3-7 mm converted to dimensionless values with classical turbomachinery systems showing that the operation parameters (rotor diameter, inlet mass flow, spinning rate) are in the favorable range. This dimensionless analysis also supports radial turbines for low speed MAS probes and diagonal turbines for high speed MAS probes. Consequently, a change from Pelton type MAS turbines to diagonal turbines might be worth considering for high speed applications. CFD simulations of the radial bearings have been compared with basic theoretical values proposing considerably smaller frictional loss values. The discrepancies might be due to the simple linear flow profile employed for the theoretical model. Frictional losses generated inside the radial bearings result in undesired heat-up of the rotor. The rotor surface temperature distribution computed by CFD simulations show a large temperature gradient over the rotor.

  19. Fluid flow dynamics in MAS systems.

    PubMed

    Wilhelm, Dirk; Purea, Armin; Engelke, Frank

    2015-08-01

    The turbine system and the radial bearing of a high performance magic angle spinning (MAS) probe with 1.3mm-rotor diameter has been analyzed for spinning rates up to 67kHz. We focused mainly on the fluid flow properties of the MAS system. Therefore, computational fluid dynamics (CFD) simulations and fluid measurements of the turbine and the radial bearings have been performed. CFD simulation and measurement results of the 1.3mm-MAS rotor system show relatively low efficiency (about 25%) compared to standard turbo machines outside the realm of MAS. However, in particular, MAS turbines are mainly optimized for speed and stability instead of efficiency. We have compared MAS systems for rotor diameter of 1.3-7mm converted to dimensionless values with classical turbomachinery systems showing that the operation parameters (rotor diameter, inlet mass flow, spinning rate) are in the favorable range. This dimensionless analysis also supports radial turbines for low speed MAS probes and diagonal turbines for high speed MAS probes. Consequently, a change from Pelton type MAS turbines to diagonal turbines might be worth considering for high speed applications. CFD simulations of the radial bearings have been compared with basic theoretical values proposing considerably smaller frictional loss values. The discrepancies might be due to the simple linear flow profile employed for the theoretical model. Frictional losses generated inside the radial bearings result in undesired heat-up of the rotor. The rotor surface temperature distribution computed by CFD simulations show a large temperature gradient over the rotor. Copyright © 2015 Elsevier Inc. All rights reserved.

  20. Nonlinear Dynamics of Structures with Material Degradation

    NASA Astrophysics Data System (ADS)

    Soltani, P.; Wagg, D. J.; Pinna, C.; Whear, R.; Briody, C.

    2016-09-01

    Structures usually experience deterioration during their working life. Oxidation, corrosion, UV exposure, and thermo-mechanical fatigue are some of the most well-known mechanisms that cause degradation. The phenomenon gradually changes structural properties and dynamic behaviour over their lifetime, and can be more problematic and challenging in the presence of nonlinearity. In this paper, we study how the dynamic behaviour of a nonlinear system changes as the thermal environment causes certain parameters to vary. To this end, a nonlinear lumped mass modal model is considered and defined under harmonic external force. Temperature dependent material functions, formulated from empirical test data, are added into the model. Using these functions, bifurcation parameters are defined and the corresponding nonlinear responses are observed by numerical continuation. A comparison between the results gives a preliminary insight into how temperature induced properties affects the dynamic response and highlights changes in stability conditions of the structure.

  1. Dynamic Magnetic Field Applications for Materials Processing

    NASA Technical Reports Server (NTRS)

    Mazuruk, K.; Grugel, Richard N.; Motakef, S.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Magnetic fields, variable in time and space, can be used to control convection in electrically conducting melts. Flow induced by these fields has been found to be beneficial for crystal growth applications. It allows increased crystal growth rates, and improves homogeneity and quality. Particularly beneficial is the natural convection damping capability of alternating magnetic fields. One well-known example is the rotating magnetic field (RMF) configuration. RMF induces liquid motion consisting of a swirling basic flow and a meridional secondary flow. In addition to crystal growth applications, RMF can also be used for mixing non-homogeneous melts in continuous metal castings. These applied aspects have stimulated increasing research on RMF-induced fluid dynamics. A novel type of magnetic field configuration consisting of an axisymmetric magnetostatic wave, designated the traveling magnetic field (TMF), has been recently proposed. It induces a basic flow in the form of a single vortex. TMF may find use in crystal growth techniques such as the vertical Bridgman (VB), float zone (FZ), and the traveling heater method. In this review, both methods, RMF and TMF are presented. Our recent theoretical and experimental results include such topics as localized TMF, natural convection dumping using TMF in a vertical Bridgman configuration, the traveling heater method, and the Lorentz force induced by TMF as a function of frequency. Experimentally, alloy mixing results, with and without applied TMF, will be presented. Finally, advantages of the traveling magnetic field, in comparison to the more mature rotating magnetic field method, will be discussed.

  2. Dynamic Magnetic Field Applications for Materials Processing

    NASA Technical Reports Server (NTRS)

    Mazuruk, K.; Grugel, Richard N.; Motakef, S.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Magnetic fields, variable in time and space, can be used to control convection in electrically conducting melts. Flow induced by these fields has been found to be beneficial for crystal growth applications. It allows increased crystal growth rates, and improves homogeneity and quality. Particularly beneficial is the natural convection damping capability of alternating magnetic fields. One well-known example is the rotating magnetic field (RMF) configuration. RMF induces liquid motion consisting of a swirling basic flow and a meridional secondary flow. In addition to crystal growth applications, RMF can also be used for mixing non-homogeneous melts in continuous metal castings. These applied aspects have stimulated increasing research on RMF-induced fluid dynamics. A novel type of magnetic field configuration consisting of an axisymmetric magnetostatic wave, designated the traveling magnetic field (TMF), has been recently proposed. It induces a basic flow in the form of a single vortex. TMF may find use in crystal growth techniques such as the vertical Bridgman (VB), float zone (FZ), and the traveling heater method. In this review, both methods, RMF and TMF are presented. Our recent theoretical and experimental results include such topics as localized TMF, natural convection dumping using TMF in a vertical Bridgman configuration, the traveling heater method, and the Lorentz force induced by TMF as a function of frequency. Experimentally, alloy mixing results, with and without applied TMF, will be presented. Finally, advantages of the traveling magnetic field, in comparison to the more mature rotating magnetic field method, will be discussed.

  3. Entrainment of granular substrate by pyroclastic flows: an experimental study and its implications for flow dynamics

    NASA Astrophysics Data System (ADS)

    Roche, O.; Niño, Y.; Mangeney, A.; Brand, B. D.; Valentine, G. A.

    2012-12-01

    Pyroclastic flows deposits may contain lithics entrained from an unconsolidated granular substrate on which the flows emplaced. In order to address this issue, analog experiments on dense gas-particle flows propagating on a horizontal granular layer were carried out to elucidate the entrainment mechanisms and to infer the dynamics of pyroclastic flows. The experimental flows were generated from the release of gas-fluidized columns of fine (80 μm) particles in a horizontal channel whose base was made of an unconsolidated granular layer. The flows consisted of a fluidized air-particles mixture, and the small hydraulic permeability of the material allowed for long-lived high interstitial pore fluid pressure during emplacement. Basal pore pressure measurements in preliminary experiments involving a rigid substrate revealed that the sliding head of the flows generated a dynamic underpressure (relative to atmosphere) proportional to the square of the front velocity. As such underpressure at the flow base was likely to promote an upward pressure gradient that could cause uplift of particles of a granular substrate, we did a theoretical analysis in order to determine the critical underpressure and the corresponding flow velocity (Uc) at which uplift could occur. This analysis showed that Uc~(dρpg/Cρ)1/2 for spherical particles, where d and ρp are the particle diameter and density, respectively, C is an empirical constant, and is ρ is the bulk flow density. It was validated with experiments on flows propagating on 3 cm-thick substrates of steel beads of diameter d=1.6 mm. The beads were first dragged horizontally individually due to basal shear, and onset of uplift did occur at Uc~0.9 m/s. The beads uplifted were incorporated within the flow base, to a height that increased up to 6-8 mm at flow velocities up to 2.5-3 m/s, and were entrained over distances of several tens of cm representing a significant part of the flow runout. The flow deposits hence had a well

  4. On Inverting the Heat Flow with Engineering Materials

    NASA Astrophysics Data System (ADS)

    Zhou, Li

    2016-02-01

    Transformation thermodynamics enriches our understanding of heat flow and makes it possible to manipulate the heat flow at will, like shielding, concentrating and inverting. The inverting of heat flow is the extreme one, which has not been studied specifically yet. In this study we firstly inverted the heat flow by transformation thermodynamics and provided the formula for the transformed thermal conductivity. Finite element simulations were conducted to realize the steady and non-steady inverting of heat flow, based on the eccentric-semi-ring structures with natural materials. To do the inverting of heat flow, a simple "L"-shape conductive structure was proposed and verified with an infrared camera. It is concluded that inverting heat flow can be done by both complex engineering materials and some simple structures.

  5. Global nuclear material flow/control model

    SciTech Connect

    Dreicer, J.S.; Rutherford, D.S.; Fasel, P.K.; Riese, J.M.

    1997-10-01

    This is the final report of a two-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The nuclear danger can be reduced by a system for global management, protection, control, and accounting as part of an international regime for nuclear materials. The development of an international fissile material management and control regime requires conceptual research supported by an analytical and modeling tool which treats the nuclear fuel cycle as a complete system. The prototype model developed visually represents the fundamental data, information, and capabilities related to the nuclear fuel cycle in a framework supportive of national or an international perspective. This includes an assessment of the global distribution of military and civilian fissile material inventories, a representation of the proliferation pertinent physical processes, facility specific geographic identification, and the capability to estimate resource requirements for the management and control of nuclear material. The model establishes the foundation for evaluating the global production, disposition, and safeguards and security requirements for fissile nuclear material and supports the development of other pertinent algorithmic capabilities necessary to undertake further global nuclear material related studies.

  6. IR DIAGNOSTICS FOR DYNAMIC FAILURE OF MATERIALS

    SciTech Connect

    McElfresh, M; DeTeresa, S

    2006-02-13

    This project explores the thermodynamics of dynamic deformation and failure of materials using high-speed spatially-resolved infrared (IR) measurements of temperature. During deformation mechanical work is converted to different forms of energy depending on the deformation processes. For example, it can be dissipated as heat in purely plastic deformation, stored as strain energy in dislocations in metals and in oriented polymeric molecular structures, and expended during the generation of new surfaces during damage and fracture. The problem of how this work is converted into these various forms is not well understood. In fact, there exists a controversy for the relatively simple case regarding the amount of work dissipated as heat during uniform plastic deformation. The goals of this work are to develop dynamic IR temperature measurement techniques and then apply them to gain a better understanding of the dynamic failure processes in both metals and polymeric composite materials. The experimental results will be compared against predictions of existing constitutive models and guide the development of higher fidelity models if needed.

  7. Flow Dynamics in the Cozumel Channel

    NASA Astrophysics Data System (ADS)

    Gabriela, C.; Candela, J.; Ochoa, J.; Badan, A.; Sheinbaum, J.

    2001-12-01

    The Cozumel Channel is a narrow passage (15 km wide by 50 km long and 400 m deep) about 70 km southwest of the Yucatan Channel in the Caribbean Sea. It is bounded by the Yucatan Peninsula on the west and the Cozumel Island on the east. There are no known reports about the physical oceanography of this channel, although its dyna-mics should be closely linked to the Yucatan Current in its approach to the Yucatan Channel. This study is mostly about the dynamic balance in the Cozumel Channel using currents, sea level, meteorological and hydrographic observations, collected over a 5 month period between December 1996 and May 1997. The momentum balance across the channel shows periods when it is mainly geostrophic, and other periods where large ageostrophic fluctuations occur. These ageostrophic fluctuations have velocities on the order of 1 m/s and last longer than a week. Other terms in the across-channel momentum equation are estimated to explain this ageostrophy; in particular, the non-turbulent advective terms are found to be the most likely source. The local rate of change and wind stress are confidently dismissed in the ageostrophic behavior, also the Reynolds stresses seem to contribute insignificantly. A mean transport of about 5 Sv towards the Gulf of Mexico is estimated for this period, although with a high degree of variability: a minimum of approximately 1.2 Sv around mid-January and a maximum of 7.5 at the beginning of May. An additional set of current observations collected between October 2000 and June 2001, that comprise data from both Cozumel and Yucatan Channels, indicate the correlation of flow fluctuations in both channels.

  8. Optical techniques for determining dynamic material properties

    SciTech Connect

    Paisley, D.L.; Stahl, D.B.

    1996-12-31

    Miniature plates are laser-launched with a 10-Joule Nd:YAG for one-dimensional (1-D) impacts on to target materials much like gas gun experiments and explosive plane wave plate launch. By making the experiments small, flyer plates (3 mm diameter x 50 micron thick) and targets (10 mm diameter x 200 micron thick), 1-D impact experiments can be performed in a standard laser-optical laboratory with minimum confinement and collateral damage. The laser-launched plates do not require the traditional sabot on gas guns nor the explosives needed for explosive planewave lenses, and as a result are much more amenable to a wide variety of materials and applications. Because of the small size very high pressure gradients can be generated with relative ease. The high pressure gradients result in very high strains and strain rates that are not easily generated by other experimental methods. The small size and short shock duration (1 - 20 ns) are ideal for dynamically measuring bond strengths of micron-thick coatings. Experimental techniques, equipment, and dynamic material results are reported.

  9. Theoretical and computational dynamics of a compressible flow

    NASA Technical Reports Server (NTRS)

    Pai, Shih-I; Luo, Shijun

    1991-01-01

    An introduction to the theoretical and computational fluid dynamics of a compressible fluid is presented. The general topics addressed include: thermodynamics and physical properties of compressible fluids; 1D flow of an inviscid compressible fluid; shock waves; fundamental equations of the dynamics of a compressible inviscid non-heat-conducting and radiating fluid, method of small perturbations, linearized theory; 2D subsonic steady potential flow; hodograph and rheograph methods, exact solutions of 2D insentropic steady flow equations, 2D steady transonic and hypersonic flows, method of characteristics, linearized theory of 3D potential flow, nonlinear theory of 3D compressibe flow, anisentropic (rotational) flow of inviscid compressible fluid, electromagnetogasdynamics, multiphase flows, flows of a compressible fluid with transport phenomena.

  10. Flow Dynamics and HSPC Homing in Bone Marrow Microvessels.

    PubMed

    Bixel, M Gabriele; Kusumbe, Anjali P; Ramasamy, Saravana K; Sivaraj, Kishor K; Butz, Stefan; Vestweber, Dietmar; Adams, Ralf H

    2017-02-14

    Measurements of flow velocities at the level of individual arterial vessels and sinusoidal capillaries are crucial for understanding the dynamics of hematopoietic stem and progenitor cell homing in the bone marrow vasculature. We have developed two complementary intravital two-photon imaging approaches to determine blood flow dynamics and velocities in multiple vessel segments by capturing the motion of red blood cells. High-resolution spatiotemporal measurements through a cranial window to determine short-time dynamics of flowing blood cells and repetitive centerline scans were used to obtain a detailed flow-profile map with hemodynamic parameters. In addition, we observed the homing of individual hematopoietic stem and progenitor cells and obtained detailed information on their homing behavior. With our imaging setup, we determined flow patterns at cellular resolution, blood flow velocities and wall shear stress in small arterial vessels and highly branched sinusoidal capillaries, and the cellular dynamics of hematopoietic stem and progenitor cell homing.

  11. Flow of granular materials down an inclined plane

    SciTech Connect

    Gudhe, R.; Rajagopal, K.R.; Massoudi, M.; Chi, R.

    1993-05-01

    The mechanics of flowing granular materials such as coal, sand, fossil-fuel energy recovery, metal ores, etc., and their flow characteristics have received considerable attention in recent years because it has relevance to several technological problems. In a number of instances these materials are also heated prior to processing, or cooled after processing. The governing equations for the flow of granular materials taking into account the heat transfer mechanism are derived using the continuum model proposed by Rajagopal and Massoudi (1990). For a fully developed flow of granular materials down an inclined plane, these equations reduce to a system of coupled ordinary differential equations. The resulting boundary value problem is solved numerically and the results are presented. For a special case, it is possible to obtain an analytic solution; this is given in the Appendix A of this report.

  12. Wigner flow reveals topological order in quantum phase space dynamics.

    PubMed

    Steuernagel, Ole; Kakofengitis, Dimitris; Ritter, Georg

    2013-01-18

    The behavior of classical mechanical systems is characterized by their phase portraits, the collections of their trajectories. Heisenberg's uncertainty principle precludes the existence of sharply defined trajectories, which is why traditionally only the time evolution of wave functions is studied in quantum dynamics. These studies are quite insensitive to the underlying structure of quantum phase space dynamics. We identify the flow that is the quantum analog of classical particle flow along phase portrait lines. It reveals hidden features of quantum dynamics and extra complexity. Being constrained by conserved flow winding numbers, it also reveals fundamental topological order in quantum dynamics that has so far gone unnoticed.

  13. Evolution of a natural debris flow: In situ measurements of flow dynamics, video imagery, and terrestrial laser scanning

    USGS Publications Warehouse

    McCoy, S.W.; Kean, J.W.; Coe, J.A.; Staley, D.M.; Wasklewicz, T.A.; Tucker, G.E.

    2010-01-01

    Many theoretical and laboratory studies have been undertaken to understand debris-flow processes and their associated hazards. However, complete and quantitative data sets from natural debris flows needed for confirmation of these results are limited. We used a novel combination of in situ measurements of debris-flow dynamics, video imagery, and pre- and postflow 2-cm-resolution digital terrain models to study a natural debris-flow event. Our field data constrain the initial and final reach morphology and key flow dynamics. The observed event consisted of multiple surges, each with clear variation of flow properties along the length of the surge. Steep, highly resistant, surge fronts of coarse-grained material without measurable pore-fluid pressure were pushed along by relatively fine-grained and water-rich tails that had a wide range of pore-fluid pressures (some two times greater than hydrostatic). Surges with larger nonequilibrium pore-fluid pressures had longer travel distances. A wide range of travel distances from different surges of similar size indicates that dynamic flow properties are of equal or greater importance than channel properties in determining where a particular surge will stop. Progressive vertical accretion of multiple surges generated the total thickness of mapped debris-flow deposits; nevertheless, deposits had massive, vertically unstratified sedimentological textures. ?? 2010 Geological Society of America.

  14. Isotope specific arbitrary material flow meter

    DOEpatents

    Barty, Christopher P. J.; Post, John C.; Jones, Edwin

    2016-10-25

    A laser-based mono-energetic gamma-ray source is used to provide non-destructive and non-intrusive, quantitative determination of the absolute amount of a specific isotope contained within pipe as part of a moving fluid or quasi-fluid material stream.

  15. Information systems for material flow management in construction processes

    NASA Astrophysics Data System (ADS)

    Mesároš, P.; Mandičák, T.

    2015-01-01

    The article describes the options for the management of material flows in the construction process. Management and resource planning is one of the key factors influencing the effectiveness of construction project. It is very difficult to set these flows correctly. The current period offers several options and tools to do this. Information systems and their modules can be used just for the management of materials in the construction process.

  16. Dynamics of Deformable Active Particles under External Flow Field

    NASA Astrophysics Data System (ADS)

    Tarama, Mitsusuke

    2017-10-01

    In most practical situations, active particles are affected by their environment, for example, by a chemical concentration gradient, light intensity, gravity, or confinement. In particular, the effect of an external flow field is important for particles swimming in a solvent fluid. For deformable active particles such as self-propelled liquid droplets and active vesicles, as well as microorganisms such as euglenas and neutrophils, a general description has been developed by focusing on shape deformation. In this review, we present our recent studies concerning the dynamics of a single active deformable particle under an external flow field. First, a set of model equations of active deformable particles including the effect of a general external flow is introduced. Then, the dynamics under two specific flow profiles is discussed: a linear shear flow, as the simplest example, and a swirl flow. In the latter case, the scattering dynamics of the active deformable particles by the swirl flow is also considered.

  17. Computational Unsteady Flow Dynamics: Oscillating Flow About a Circular Cylinder

    DTIC Science & Technology

    1991-12-01

    that the calculations can be carried out only for short times (less than two cycles of flow oscillation) with a non-super computer. Murashige , Hinatsu...Flow Round a Circu- lar Cylinder," Computers &Fluids, Vol. 12, No. 4, pp. 255-280. 6. Murashige , S., Hinatsu, M., and Kinoshita, T, 1989, "Direct

  18. Transient Heat and Material Flow Modeling of Friction Stir Processing of Magnesium Alloy using Threaded Tool

    SciTech Connect

    Yu, Zhenzhen; Zhang, Wei; Choo, Hahn; Feng, Zhili

    2012-01-01

    A three-dimensional transient computational fluid dynamics (CFD) model was developed to investigate the material flow and heat transfer during friction stir processing (FSP) in an AZ31B magnesium alloy. The material was assumed to be a non-Newtonian viscoplastic fluid, and the Zener-Hollomon parameter was used to describe the dependence of material viscosity on temperature and strain rate. The material constants used in the constitutive equation were determined experimentally from compression tests of the AZ31B Mg alloy under a wide range of strain rates and temperatures. A dynamic mesh method, combining both Lagrangian and Eulerian formulations, was used to capture the material flow induced by the movement of the threaded tool pin. Massless inert particles were embedded in the simulation domain to track the detailed history of material flow. The actual FSP was also carried out on a wrought Mg plate where temperature profiles were recorded by embedding thermocouples. The predicted transient temperature history was found to be consistent with that measured during FSP. Finally, the influence of the thread on the simulated results of thermal history and material flow was studied by comparing two models: one with threaded pin and the other with smooth pin surface.

  19. Dynamic failure in two-phase materials

    DOE PAGES

    Fensin, S. J.; Walker, E. K.; Cerreta, E. K.; ...

    2015-12-21

    Previous experimental research has shown that microstructural features such as interfaces, inclusions, vacancies, and heterogeneities can all act as voidnucleation sites. However, it is not well understood how important these interfaces are to damage evolution and failure as a function of the surrounding parentmaterials. In this work, we present results on three different polycrystallinematerials: (1) Cu, (2) Cu-24 wt. %Ag, and (3) Cu-15 wt. %Nb which were studied to probe the influence of bi-metal interfaces onvoidnucleation and growth. These materials were chosen due to the range of difference in structure and bulk properties between the two phases. The initial resultsmore » suggest that when there are significant differences between the bulk properties (for example: stacking fault energy, melting temperature, etc.) the type of interface between the two parent materials does not principally control the damage nucleation and growth process. Rather, it is the “weaker” material that dictates the dynamic spall strength of the overall two-phase material.« less

  20. Dynamic Behavior of Engineered Lattice Materials

    PubMed Central

    Hawreliak, J. A.; Lind, J.; Maddox, B.; Barham, M.; Messner, M.; Barton, N.; Jensen, B. J.; Kumar, M.

    2016-01-01

    Additive manufacturing (AM) is enabling the fabrication of materials with engineered lattice structures at the micron scale. These mesoscopic structures fall between the length scale associated with the organization of atoms and the scale at which macroscopic structures are constructed. Dynamic compression experiments were performed to study the emergence of behavior owing to the lattice periodicity in AM materials on length scales that approach a single unit cell. For the lattice structures, both bend and stretch dominated, elastic deflection of the structure was observed ahead of the compaction of the lattice, while no elastic deformation was observed to precede the compaction in a stochastic, random structure. The material showed lattice characteristics in the elastic response of the material, while the compaction was consistent with a model for compression of porous media. The experimental observations made on arrays of 4 × 4 × 6 lattice unit cells show excellent agreement with elastic wave velocity calculations for an infinite periodic lattice, as determined by Bloch wave analysis, and finite element simulations. PMID:27321697

  1. A dynamic plug flow reactor model for a vanadium redox flow battery cell

    NASA Astrophysics Data System (ADS)

    Li, Yifeng; Skyllas-Kazacos, Maria; Bao, Jie

    2016-04-01

    A dynamic plug flow reactor model for a single cell VRB system is developed based on material balance, and the Nernst equation is employed to calculate cell voltage with consideration of activation and concentration overpotentials. Simulation studies were conducted under various conditions to investigate the effects of several key operation variables including electrolyte flow rate, upper SOC limit and input current magnitude on the cell charging performance. The results show that all three variables have a great impact on performance, particularly on the possibility of gassing during charging at high SOCs or inadequate flow rates. Simulations were also carried out to study the effects of electrolyte imbalance during long term charging and discharging cycling. The results show the minimum electrolyte flow rate needed for operation within a particular SOC range in order to avoid gassing side reactions during charging. The model also allows scheduling of partial electrolyte remixing operations to restore capacity and also avoid possible gassing side reactions during charging. Simulation results also suggest the proper placement for cell voltage monitoring and highlight potential problems associated with setting the upper charging cut-off limit based on the inlet SOC calculated from the open-circuit cell voltage measurement.

  2. Sediment Transport Dynamics and Bedform Evolution During Unsteady Flows

    NASA Astrophysics Data System (ADS)

    Hu, H.; Parsons, D. R.; Ockelford, A.; Hardy, R. J.; Ashworth, P. J.; Best, J.

    2016-12-01

    Dunes are ubiquitous features in sand bed rivers and estuaries, and their formation, growth and kinematics play a dominant role in boundary flow structure, flow resistance and sediment transport processes. However, bedform evolution and dynamics during the rising/falling limb of a flood wave remain poorly understood. Herein, we report on a series of flume experiments, undertaken at the University of Hull's Total Environment Simulator flume/wave tank facility, with imposed flow variations and different hydrographs: i) a sudden (shock) change, ii) a fast flood wave and iii) a slow flood wave. Our analysis shows that, because of changes of sediment transport mechanisms with discharge, the sediment flux rather than bedform migration rate is a more appropriate parameter to relate to transport stage. This is particularly the case during bedload transport dominated periods at lower flow discharge, where a strong power law relationship was detected. In terms of varying processes across the hydrograph limbs, bedform evolution during the rising limb is dominated not only by bedform amalgamation but also by the washing out of smaller-scale bedforms. Furthermore, bedform growth is independent of the rising rate of the hydrograph limb, while evolution of bedform decay is affected by the rate of discharge decrease. This results in an anticlockwise hysteresis between transport stage and total flux was found in fast wave experiment, indicating a significant role of the change in sediment transport mechanisms on bedform evolution. Moreover, analysis on the variation of deformation fraction (F, ratio of the deformation flux to the total bed material flux) suggests that net degradation of the bed enhances bedform deformation and leads to a higher F ( 0.65). This work extends our knowledge on how dunes generate and develop under variable flows and has begun to explore how variations in transport stage can be coupled with the variation in sediment transport mechanisms, and/or sediment

  3. Application of porous materials for laminar flow control

    NASA Technical Reports Server (NTRS)

    Pearce, W. E.

    1978-01-01

    Fairly smooth porous materials were elected for study Doweave; Fibermetal; Dynapore; and perforated titanium sheet. Factors examined include: surface smoothness; suction characteristics; porosity; surface impact resistance; and strain compatibility. A laminar flow control suction glove arrangement was identified with material combinations compatible with thermal expansion and structural strain.

  4. Gravity flow instability of viscoplastic materials: The ketchup drip

    NASA Astrophysics Data System (ADS)

    Coussot, P.; Gaulard, F.

    2005-09-01

    In contrast with simple liquids such as water, milk, honey, which easily flow as a continuous jet when poured from a vessel, pasty materials such as mayonnaise, mustard, ketchup, puree, etc., fall by fits and starts in a wide range of flow rates. This may, for example, be observed when ketchup or mayonnaise is pushed from a tube at a sufficient height over a plate: although surface tension effects are generally negligible because of its high viscosity the material drops as successive droplets of more or less similar size (except at large flow rates). Here we demonstrate that this effect is a kind of flow instability which develops when the weight of material becomes larger than a force due to its yield stress, namely a critical stress below which it cannot flow steadily. Furthermore, we show that depending on the exact material behavior surprising phenomena may be observed: the size of the droplet may remain constant or even decrease (for thixotropic materials) as the flow rate increases. This approach, for example, provides tools for controlling the shape of droplets in cooking and the size of extrudates in food and mineral industries.

  5. Characterizing He II flow through porous materials using counterflow data

    NASA Technical Reports Server (NTRS)

    Maddocks, J. R.; Van Sciver, S. W.

    1991-01-01

    An empirical extension of the two-fluid model is used to characterize He II flow through porous materials. It is shown that four empirical parameters are necessary to describe the pressure and temperature differences induced by He II flow through a porous sample. The three parameters required to determine pressure differences are measured in counterflow and found to compare favorably with those for isothermal flow. The fourth parameter, the Gorter-Mellink constant, differs substantially from smooth tube values. It is concluded that parameter values determined from counterflow can be used to predict pressure and temperature differences in a variety of flows to an accuracy of about +/- 20 percent.

  6. Characterizing He II flow through porous materials using counterflow data

    NASA Technical Reports Server (NTRS)

    Maddocks, J. R.; Van Sciver, S. W.

    1991-01-01

    An empirical extension of the two-fluid model is used to characterize He II flow through porous materials. It is shown that four empirical parameters are necessary to describe the pressure and temperature differences induced by He II flow through a porous sample. The three parameters required to determine pressure differences are measured in counterflow and found to compare favorably with those for isothermal flow. The fourth parameter, the Gorter-Mellink constant, differs substantially from smooth tube values. It is concluded that parameter values determined from counterflow can be used to predict pressure and temperature differences in a variety of flows to an accuracy of about +/- 20 percent.

  7. A model of material flow during friction stir welding

    SciTech Connect

    Hamilton, Carter Dymek, Stanislaw; Blicharski, Marek

    2008-09-15

    Tin plated 6061-T6 aluminum extrusions were friction stir welded in a 90 deg. butt-weld configuration. A banded microstructure of interleaved layers of particle-rich and particle-poor material comprised the weld nugget. Scanning and transmission electron microscopy revealed the strong presence of tin within the particle-rich bands, but TEM foils taken from the TMAZ, HAZ and base material showed no indication of Sn-containing phases. Since tin is limited to the surface of the pre-weld extrusions, surface material flowed into the nugget region, forming the particle-rich bands. Similarly, the particle-poor bands with no tin originated from within the thickness of the extrusions. A model of material flow during friction stir welding is proposed for which the weld nugget forms as surface material extrudes from the retreating side into a plasticized zone surrounding the FSW pin. The extruded column buckles between the extrusion force driving the material into the zone and the drag force of the in-situ material resisting its entry. A banded microstructure of interleaved surface material and in-situ material, therefore, develops. The model successfully describes several of the experimentally observed weld characteristics, but the model is limited to specific conditions of material flow and assumptions regarding steady-state.

  8. DYNAMIC MODELING STRATEGY FOR FLOW REGIME TRANSITION IN GAS-LIQUID TWO-PHASE FLOWS

    SciTech Connect

    X. Wang; X. Sun; H. Zhao

    2011-09-01

    In modeling gas-liquid two-phase flows, the concept of flow regime has been used to characterize the global interfacial structure of the flows. Nearly all constitutive relations that provide closures to the interfacial transfers in two-phase flow models, such as the two-fluid model, are often flow regime dependent. Currently, the determination of the flow regimes is primarily based on flow regime maps or transition criteria, which are developed for steady-state, fully-developed flows and widely applied in nuclear reactor system safety analysis codes, such as RELAP5. As two-phase flows are observed to be dynamic in nature (fully-developed two-phase flows generally do not exist in real applications), it is of importance to model the flow regime transition dynamically for more accurate predictions of two-phase flows. The present work aims to develop a dynamic modeling strategy for determining flow regimes in gas-liquid two-phase flows through the introduction of interfacial area transport equations (IATEs) within the framework of a two-fluid model. The IATE is a transport equation that models the interfacial area concentration by considering the creation and destruction of the interfacial area, such as the fluid particle (bubble or liquid droplet) disintegration, boiling and evaporation; and fluid particle coalescence and condensation, respectively. For the flow regimes beyond bubbly flows, a two-group IATE has been proposed, in which bubbles are divided into two groups based on their size and shape (which are correlated), namely small bubbles and large bubbles. A preliminary approach to dynamically identifying the flow regimes is provided, in which discriminators are based on the predicted information, such as the void fraction and interfacial area concentration of small bubble and large bubble groups. This method is expected to be applied to computer codes to improve their predictive capabilities of gas-liquid two-phase flows, in particular for the applications in

  9. Flux flow and flux dynamics in high-Tc superconductors

    NASA Technical Reports Server (NTRS)

    Bennett, L. H.; Turchinskaya, M.; Swartzendruber, L. J.; Roitburd, A.; Lundy, D.; Ritter, J.; Kaiser, D. L.

    1991-01-01

    Because high temperature superconductors, including BYCO and BSSCO, are type 2 superconductors with relatively low H(sub c 1) values and high H(sub c 2) values, they will be in a critical state for many of their applications. In the critical state, with the applied field between H(sub c 1) and H(sub c 2), flux lines have penetrated the material and can form a flux lattice and can be pinned by structural defects, chemical inhomogeneities, and impurities. A detailed knowledge of how flux penetrates the material and its behavior under the influence of applied fields and current flow, and the effect of material processing on these properties, is required in order to apply, and to improve the properties of these superconductors. When the applied field is changed rapidly, the time dependence of flux change can be divided into three regions, an initial region which occurs very rapidly, a second region in which the magnetization has a 1n(t) behavior, and a saturation region at very long times. A critical field is defined for depinning, H(sub c,p) as that field at which the hysteresis loop changes from irreversible to reversible. As a function of temperature, it is found that H(sub c,p) is well described by a power law with an exponent between 1.5 and 2.5. The behavior of H(sub c,p) for various materials and its relationship to flux flow and flux dynamics are discussed.

  10. Benchmarking computational fluid dynamics models for lava flow simulation

    NASA Astrophysics Data System (ADS)

    Dietterich, Hannah; Lev, Einat; Chen, Jiangzhi

    2016-04-01

    Numerical simulations of lava flow emplacement are valuable for assessing lava flow hazards, forecasting active flows, interpreting past eruptions, and understanding the controls on lava flow behavior. Existing lava flow models vary in simplifying assumptions, physics, dimensionality, and the degree to which they have been validated against analytical solutions, experiments, and natural observations. In order to assess existing models and guide the development of new codes, we conduct a benchmarking study of computational fluid dynamics models for lava flow emplacement, including VolcFlow, OpenFOAM, FLOW-3D, and COMSOL. Using the new benchmark scenarios defined in Cordonnier et al. (Geol Soc SP, 2015) as a guide, we model viscous, cooling, and solidifying flows over horizontal and sloping surfaces, topographic obstacles, and digital elevation models of natural topography. We compare model results to analytical theory, analogue and molten basalt experiments, and measurements from natural lava flows. Overall, the models accurately simulate viscous flow with some variability in flow thickness where flows intersect obstacles. OpenFOAM, COMSOL, and FLOW-3D can each reproduce experimental measurements of cooling viscous flows, and FLOW-3D simulations with temperature-dependent rheology match results from molten basalt experiments. We can apply these models to reconstruct past lava flows in Hawai'i and Saudi Arabia using parameters assembled from morphology, textural analysis, and eruption observations as natural test cases. Our study highlights the strengths and weaknesses of each code, including accuracy and computational costs, and provides insights regarding code selection.

  11. Optical Window Materials For Hypersonic Flow

    NASA Astrophysics Data System (ADS)

    Au, Robert H.

    1989-09-01

    Optical window materials were investigated for infrared sensor systems used in observing ground targets from a hypersonic-glide vehicle. The equilibrium temperature of the window in the glide region depends on the emissivity and varied between 1,370 and 2,250 K. The high temperatures showed that a protective cover over the window is required during the entire glide region of the trajectory. Ejection of the window cover at 70-kft altitude in the terminal region was assumed, resulting in maximum window temperatures of 565 K and 592 K for magnesium oxide and diamond windows, respectively, both 0.8-in thick. The window temperatures for germanium and sapphire were also calculated. Thermal shock, thermal expansion, the effects of the window radiation on the infrared detectors and methods to reduce the hot window problem were examined.

  12. Comminution of Ceramic Materials Under High-Shear Dynamic Compaction

    NASA Astrophysics Data System (ADS)

    Homel, Michael; Loiseau, Jason; Higgins, Andrew; Herbold, Eric; Hogan, Jamie

    The post-failure ``granular flow'' response of high-strength lightweight ceramics has important implications on the materials' effectiveness for ballistic protection. We study the dynamic compaction and shear flow of ceramic fragments and powders using computational and experimental analysis of a collapsing thick-walled cylinder geometry. Using newly developed tools for mesoscale simulation of brittle materials, we study the effect of fracture, comminution, shear-enhanced dilatation, and frictional contact on the continuum compaction response. Simulations are directly validated through particle Doppler velocimetry measurements at the inner surface of the cylindrical powder bed. We characterize the size distribution and morphologies of the initial and compacted material fragments to both validate the computational model and to elucidate the dominant failure processes. A portion of this work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344. Lawrence Livermore National Security, LLC. LLNL-ABS-678862.

  13. Dendritic Growth with Fluid Flow for Pure Materials

    NASA Technical Reports Server (NTRS)

    Jeong, Jun-Ho; Dantzig, Jonathan A.; Goldenfeld, Nigel

    2003-01-01

    We have developed a three-dimensional, adaptive, parallel finite element code to examine solidification of pure materials under conditions of forced flow. We have examined the effect of undercooling, surface tension anisotropy and imposed flow velocity on the growth. The flow significantly alters the growth process, producing dendrites that grow faster, and with greater tip curvature, into the flow. The selection constant decreases slightly with flow velocity in our calculations. The results of the calculations agree well with the transport solution of Saville and Beaghton at high undercooling and high anisotropy. At low undercooling, significant deviations are found. We attribute this difference to the influence of other parts of the dendrite, removed from the tip, on the flow field.

  14. Fundamental Study of Material Flow in Friction Stir Welds

    NASA Technical Reports Server (NTRS)

    Reynolds, Anthony P.

    1999-01-01

    The presented research project consists of two major parts. First, the material flow in solid-state, friction stir, butt-welds as been investigated using a marker insert technique. Changes in material flow due to welding parameter as well as tool geometry variations have been examined for different materials. The method provides a semi-quantitative, three-dimensional view of the material transport in the welded zone. Second, a FSW process model has been developed. The fully coupled model is based on fluid mechanics; the solid-state material transport during welding is treated as a laminar, viscous flow of a non-Newtonian fluid past a rotating circular cylinder. The heat necessary for the material softening is generated by deformation of the material. As a first step, a two-dimensional model, which contains only the pin of the FSW tool, has been created to test the suitability of the modeling approach and to perform parametric studies of the boundary conditions. The material flow visualization experiments agree very well with the predicted flow field. Accordingly, material within the pin diameter is transported only in the rotation direction around the pin. Due to the simplifying assumptions inherent in the 2-D model, other experimental data such as forces on the pin, torque, and weld energy cannot be directly used for validation. However, the 2-D model predicts the same trends as shown in the experiments. The model also predicts a deviation from the "normal" material flow at certain combinations of welding parameters, suggesting a possible mechanism for the occurrence of some typical FSW defects. The next step has been the development of a three-dimensional process model. The simplified FSW tool has been designed as a flat shoulder rotating on the top of the workpiece and a rotating, cylindrical pin, which extends throughout the total height of the flow domain. The thermal boundary conditions at the tool and at the contact area to the backing plate have been varied

  15. Efficient material flow in mixed model assembly lines.

    PubMed

    Alnahhal, Mohammed; Noche, Bernd

    2013-01-01

    In this study, material flow from decentralized supermarkets to stations in mixed model assembly lines using tow (tugger) trains is investigated. Train routing, scheduling, and loading problems are investigated in parallel to minimize the number of trains, variability in loading and in routes lengths, and line-side inventory holding costs. The general framework for solving these problems in parallel contains analytical equations, Dynamic Programming (DP), and Mixed Integer Programming (MIP). Matlab in conjunction with LP-solve software was used to formulate the problem. An example was presented to explain the idea. Results which were obtained in very short CPU time showed the effect of using time buffer among routes on the feasible space and on the optimal solution. Results also showed the effect of the objective, concerning reducing the variability in loading, on the results of routing, scheduling, and loading. Moreover, results showed the importance of considering the maximum line-side inventory beside the capacity of the train in the same time in finding the optimal solution.

  16. A hydrodynamic model for granular material flows including segregation effects

    NASA Astrophysics Data System (ADS)

    Gilberg, Dominik; Klar, Axel; Steiner, Konrad

    2017-06-01

    The simulation of granular flows including segregation effects in large industrial processes using particle methods is accurate, but very time-consuming. To overcome the long computation times a macroscopic model is a natural choice. Therefore, we couple a mixture theory based segregation model to a hydrodynamic model of Navier-Stokes-type, describing the flow behavior of the granular material. The granular flow model is a hybrid model derived from kinetic theory and a soil mechanical approach to cover the regime of fast dilute flow, as well as slow dense flow, where the density of the granular material is close to the maximum packing density. Originally, the segregation model has been formulated by Thornton and Gray for idealized avalanches. It is modified and adapted to be in the preferred form for the coupling. In the final coupled model the segregation process depends on the local state of the granular system. On the other hand, the granular system changes as differently mixed regions of the granular material differ i.e. in the packing density. For the modeling process the focus lies on dry granular material flows of two particle types differing only in size but can be easily extended to arbitrary granular mixtures of different particle size and density. To solve the coupled system a finite volume approach is used. To test the model the rotational mixing of small and large particles in a tumbler is simulated.

  17. Dynamics of High Pressure Reacting Shear Flows

    DTIC Science & Technology

    2013-12-17

    and supercritical acoustic-jet interactions to reacting flow in a canonical coaxial shear flow configuration – Emphasis on the flame holding region...unlimited. PA#13554 11 Coaxial Jets Initial...PA#13554 12 Forced Coaxial Jets 1. Transverse Acoustic mode from chamber

  18. Linking environmental flows to sediment dynamics

    Treesearch

    Diego García de Jalón; Martina Bussettini; Massimo Rinaldi; Gordon Grant; Nikolai Friberg; Ian G. Cowx; Fernando Magdaleno; Tom Buijse

    2016-01-01

    This is a policy discussion paper aimed at addressing possible alternative approaches for environmental flows (e-Flows) assessment and identification within the context of best strategies for fluvial restoration. We focus on dammed rivers in Mediterranean regions. Fluvial species and their ecological integrity are the result of their evolutionary adaptation to river...

  19. MPD (magnetoplasmadynamic) thrust chamber flow dynamics

    NASA Astrophysics Data System (ADS)

    1987-09-01

    Performance characteristics of Magnetoplasmadynamic (MPD) arcjets depend on proper matching of electromagnetic and fluid mechanical constraints within the thrust chamber. Experimental measurements of internal flow conditions during MPD arcjet operation are needed to guide development of flow models and to assess the validity of theoretical predictions. Efforts are continuing in a corporative effort to apply an array of diagnostic techniques including time-, space-, and spectrally-resolved photography to examine MPD arcjet internal flows. Experimental elucidation of the internal flow structure is used to develop predictive models for optimal geometries and operating parameters. Probes have been used to map the current and voltage distributions within uniform height and flared annular channels. This work is concerned with the effect of thruster channel variations on the current conduction regions of the MPD internal flow. Other aspects of the internal flow structure that have been modeled involve the transition of the input mass flow from neutral gas to electrically-conducting plasma. Scale sizes for the transition region were estimated in terms of the electrical and thermodynamic properties of the propellant gas (e.g., argon). These estimates indicate that the electrical conductivity of the flow can be established in distances that are small compared to the characteristic dimension for current conduction near the entrance to the arcjet thrust chamber.

  20. Electromagnetic valve for controlling the flow of molten, magnetic material

    DOEpatents

    Richter, Tomas

    1998-01-01

    An electromagnetic valve for controlling the flow of molten, magnetic material is provided, which comprises an induction coil for generating a magnetic field in response to an applied alternating electrical current, a housing, and a refractory composite nozzle. The nozzle is comprised of an inner sleeve composed of an erosion resistant refractory material (e.g., a zirconia ceramic) through which molten, magnetic metal flows, a refractory outer shell, and an intermediate compressible refractory material, e.g., unset, high alumina, thermosetting mortar. The compressible refractory material is sandwiched between the inner sleeve and outer shell, and absorbs differential expansion stresses that develop within the nozzle due to extreme thermal gradients. The sandwiched layer of compressible refractory material prevents destructive cracks from developing in the refractory outer shell.

  1. Electromagnetic valve for controlling the flow of molten, magnetic material

    DOEpatents

    Richter, T.

    1998-06-16

    An electromagnetic valve for controlling the flow of molten, magnetic material is provided, which comprises an induction coil for generating a magnetic field in response to an applied alternating electrical current, a housing, and a refractory composite nozzle. The nozzle is comprised of an inner sleeve composed of an erosion resistant refractory material (e.g., a zirconia ceramic) through which molten, magnetic metal flows, a refractory outer shell, and an intermediate compressible refractory material, e.g., unset, high alumina, thermosetting mortar. The compressible refractory material is sandwiched between the inner sleeve and outer shell, and absorbs differential expansion stresses that develop within the nozzle due to extreme thermal gradients. The sandwiched layer of compressible refractory material prevents destructive cracks from developing in the refractory outer shell. 5 figs.

  2. Blending liquid into a flowing dry granular material

    NASA Astrophysics Data System (ADS)

    Saingier, Guillaume; Sauret, Alban; Jop, Pierre

    2017-06-01

    We study experimentally the growth dynamics of a horizontal wet granular aggregate produced by accretion when a dry granular jet impacts a wet substrate. The tomographic imaging demonstrates that the wet aggregate is fully saturated and its cohesion is related to the capillary suction due to the pressure drop at the liquid/air interface. We highlight that the accretion process is characterized by two different growth dynamics depending on the hydrostatic depression in the material. At low depression, the growth dynamics exibits a "diffusive" regime whereas the dynamics becomes linear for higher depressions. A competition between the viscous displacement of the fluid into the granular material and the sticking dynamics is proposed to understand the transition in the growth velocity.

  3. Toward a dynamical understanding of planetary-scale flow regimes.

    NASA Astrophysics Data System (ADS)

    Marshall, J.; Molteni, F.

    1993-06-01

    A strategy for diagnosing and interpreting flow regimes that is firmly rooted in dynamical theory is presented and applied to the study of observed and modeled planetary-scale regimes of the wintertime circulation in the Northern Hemisphere.

  4. Inductive heating with magnetic materials inside flow reactors.

    PubMed

    Ceylan, Sascha; Coutable, Ludovic; Wegner, Jens; Kirschning, Andreas

    2011-02-07

    Superparamagnetic nanoparticles coated with silica gel or alternatively steel beads are new fixed-bed materials for flow reactors that efficiently heat reaction mixtures in an inductive field under flow conditions. The scope and limitations of these novel heating materials are investigated in comparison with conventional and microwave heating. The results suggest that inductive heating can be compared to microwave heating with respect to rate acceleration. It is also demonstrated that a very large diversity of different reactions can be performed under flow conditions by using inductively heated flow reactors. These include transfer hydrogenations, heterocyclic condensations, pericyclic reactions, organometallic reactions, multicomponent reactions, reductive cyclizations, homogeneous and heterogeneous transition-metal catalysis. Silica-coated iron oxide nanoparticles are stable under many chemical conditions and the silica shell could be utilized for further functionalization with Pd nanoparticles, rendering catalytically active heatable iron oxide particles. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Spin Dynamics in Novel Materials Systems

    NASA Astrophysics Data System (ADS)

    Yu, Howard

    Spintronics and organic electronics are fields that have made considerable advances in recent years, both in fundamental research and in applications. Organic materials have a number of attractive properties that enable them to complement applications traditionally fulfilled by inorganic materials, while spintronics seeks to take advantage of the spin degree of freedom to produce new applications. My research is aimed at combining these two fields to develop organic materials for spintronics use. My thesis is divided into three primary projects centered around an organic-based semiconducting ferrimagnet, vanadium tetracyanoethylene. First, we investigated the transport characteristics of a hybrid organic-inorganic heterostructure. Semiconductors form the basis of the electronics industry, and there has been considerable effort put forward to develop organic semiconductors for applications like organic light-emitting diodes and organic thin film transistors. Working with hybrid organic-inorganic semiconductor device structures allows us to potentially take advantage of the infrastructure that has already been developed for silicon and other inorganic semiconductors. This could potentially pave the way for a new class of active hybrid devices with multifunctional behavior. Second, we investigated the magnetic resonance characteristics of V[TCNE]x, in multiple measurement schemes and exploring the effect of temperature, frequency, and chemical tuning. Recently, the spintronics community has shifted focus from static electrical spin injection to various dynamic processes, such as spin pumping and thermal effects. Spin pumping in particular is an intriguing way to generate pure spin currents via magnetic resonance that has attracted a high degree of interest, with the FMR linewidth being an important metric for spin injection. Furthermore, we can potentially use these measurements to probe the magnetic properties as we change the physical properties of the materials by

  6. How particle shape affects the flow through granular materials.

    PubMed

    Nemati Hayati, Ali; Ahmadi, Mohammad Mehdi; Mohammadi, Soheil

    2012-03-01

    Flow through the pores of granular materials has many instances in practice. Therefore, it is interesting to realize how some parameters, such as the shape of the particles affect the passing flow. Following the recent mathematical theory proposed by the authors, this paper deals with the issue of how tortuosity and permeability are influenced by the particle shape. Comparison of the results with the experimental data reveals the competency of the theory in predicting the impact of particle geometry.

  7. Applying flow chemistry: methods, materials, and multistep synthesis.

    PubMed

    McQuade, D Tyler; Seeberger, Peter H

    2013-07-05

    The synthesis of complex molecules requires control over both chemical reactivity and reaction conditions. While reactivity drives the majority of chemical discovery, advances in reaction condition control have accelerated method development/discovery. Recent tools include automated synthesizers and flow reactors. In this Synopsis, we describe how flow reactors have enabled chemical advances in our groups in the areas of single-stage reactions, materials synthesis, and multistep reactions. In each section, we detail the lessons learned and propose future directions.

  8. Fluid mechanics of dynamic stall. I - Unsteady flow concepts

    NASA Technical Reports Server (NTRS)

    Ericsson, L. E.; Reding, J. P.

    1988-01-01

    Advanced military aircraft 'supermaneuverability' requirements entail the sustained operation of airfoils at stalled flow conditions. The present work addresses the effects of separated flow on vehicle dynamics; an analytic method is presented which employs static experimental data to predict the separated flow effect on incompressible unsteady aerodynamics. The key parameters in the analytic relationship between steady and nonsteady aerodynamics are the time-lag before a change of flow conditions can affect the separation-induced aerodynamic loads, the accelerated flow effect, and the moving wall effect.

  9. Steady flow through a constricted cylinder by multiparticle collision dynamics.

    PubMed

    Bedkihal, Salil; Kumaradas, J Carl; Rohlf, Katrin

    2013-10-01

    The flow characterization of blood through healthy and diseased flow geometries is of interest to researchers and clinicians alike, as it may allow for early detection, and monitoring, of cardiovascular disease. In this paper, we use a numerically efficient particle-based flow model called multiparticle collision dynamics (MPC for short) to study the effect of compressibility and slip of flow of a Newtonian fluid through a cylinder with a local constriction. We use a cumulative averaging method to compare our MPC results to the finite-element solution of the incompressible no-slip Navier-Stokes equations in the same geometry. We concentrate on low Reynolds number flows [[Formula: see text

  10. Importance of considering intraborehole flow in solute transport modeling under highly dynamic flow conditions

    SciTech Connect

    Ma, Rui; Zheng, Chunmiao; Tonkin, Matthew J.; Zachara, John M.

    2011-04-01

    Correct interpretation of tracer test data is critical for understanding transport processes in the subsurface. This task can be greatly complicated by the presence of intraborehole flows in a highly dynamic flow environment. At a new tracer test site (Hanford IFRC) a dynamic flow field created by changes in the stage of the adjacent Columbia River, coupled with a heterogeneous hydraulic conductivity distribution, leads to considerable variations in vertical hydraulic gradients. These variations, in turn, create intraborehole flows in fully-screened (6.5 m) observation wells with frequently alternating upward and downward movement. This phenomenon, in conjunction with a highly permeable aquifer formation and small horizontal hydraulic gradients, makes modeling analysis and model calibration a formidable challenge. Groundwater head data alone were insufficient to define the flow model boundary conditions, and the movement of the tracer was highly sensitive to the dynamics of the flow field. This study shows that model calibration can be significantly improved by explicitly considering (a) dynamic flow model boundary conditions and (b) intraborehole flow. The findings from this study underscore the difficulties in interpreting tracer tests and understanding solute transport under highly dynamic flow conditions.

  11. Importance of considering intraborehole flow in solute transport modeling under highly dynamic flow conditions.

    PubMed

    Ma, Rui; Zheng, Chunmiao; Tonkin, Matt; Zachara, John M

    2011-04-01

    Correct interpretation of tracer test data is critical for understanding transport processes in the subsurface. This task can be greatly complicated by the presence of intraborehole flows in a highly dynamic flow environment. At a new tracer test site (Hanford IFRC) a dynamic flow field created by changes in the stage of the adjacent Columbia River, coupled with a heterogeneous hydraulic conductivity distribution, leads to considerable variations in vertical hydraulic gradients. These variations, in turn, create intraborehole flows in fully-screened (6.5m) observation wells with frequently alternating upward and downward movement. This phenomenon, in conjunction with a highly permeable aquifer formation and small horizontal hydraulic gradients, makes modeling analysis and model calibration a formidable challenge. Groundwater head data alone were insufficient to define the flow model boundary conditions, and the movement of the tracer was highly sensitive to the dynamics of the flow field. This study shows that model calibration can be significantly improved by explicitly considering (a) dynamic flow model boundary conditions and (b) intraborehole flow. The findings from this study underscore the difficulties in interpreting tracer tests and understanding solute transport under highly dynamic flow conditions.

  12. MPD (Magnetoplasmadynamic) Thrust Chamber Flow Dynamics.

    DTIC Science & Technology

    1987-09-29

    magnetoplasmadynamic, arcjet 𔄃 ABSTRACT (Continue on reverse if necessary and identify by block number)I h The performance characteristics of MPD arcjets ...conditions during MPD arcjet operation are needed to guide development of flow models and to assess the validity of theoretical predictions. Efforts...techniques including time-, space-, and spectrally-resolved photography, to examine MPD arcjet internal flows. Experimental elucidation of the internal I

  13. Nebkha flow dynamics and shadow dune formation

    NASA Astrophysics Data System (ADS)

    Hesp, Patrick A.; Smyth, Thomas A. G.

    2017-04-01

    In this study, wind flow is simulated via CFD over five 'nebkha' dune forms that range in shape from a cone, to a hemisphere (approximately) and to a dome in order to examine the structure of the wake zone formed downwind and the effect on the leeward flow separation zone and shadow dune formation. Dune height was fixed at 0.5 m while the nebkha diameter increased in 0.25 m increments from 0.5 m to 1.5 m and aspect ratio (h/D) from 1.0 to 0.3. The mean flow comprises an upwind region of reduced velocity which expands as nebkha width increases, high velocity marginal wings, and paired counter-rotating reversing vortices leeward of the nebkha. The point at which flow separation occurs moves further downwind as the nebkha diameter increases. The core regions of the reversing vortices are situated further downwind behind the smaller nebkha than in the case of the larger nebkha. These factors in combination allow for higher velocity perturbations (TKE) and narrower wake behind the smaller nebkha, and the suppression of downwind wake development in the case of the increasingly larger nebkha. Shadow dune length increases as nebkha width increases for lower incident velocity flow and is barely affected by nebkha width at higher flows. The extent of the leeward separation or wake zone, and hence shadow dune length, more strongly varies as a function of wind velocity.

  14. Granular Flow and Dynamics of Lunar Simulants in Excavating Implements

    NASA Technical Reports Server (NTRS)

    Agui, Juan H.; Wilkinson, R. Allen

    2010-01-01

    The exploration of the lunar surface will rely on properly designed excavation equipment for surface preparations and for collection of lunar regolith in In-Situ Resource Utilization (ISRU) processes. Performance efficiency, i.e minimizing loading forces while maximizing material collection, and mass and volume reductions are major design goals. The NASA Glenn Research Center has embarked on an experimental program to determine the flow characteristics and dynamic forces produced by excavation operations using various excavator bucket designs. A new large scale soil bin facility, 2.27 m x 5.94 m x 0.76 m (nominally 8 ft. x 20 ft. x 27 in.) in size, capable of accommodating moderately large test implements was used for the simulations of lunar operations. The soil bin is filled with GRC-3simulant (a mixture of industrial sands and silt with a particle size distribution and the bulk mechanical (shear) strength representative of an average of lunar regolith from different regions) and uses motorized horizontal rails and a vertical actuator to drive the implement through the lunar simulant soil. A six-axis load cell and encoders provide well resolved measurements of the three dimensional forces and torques and motion of the bucket. In addition, simultaneous video allows for the analysis of the flow behavior and structure formation of the regolith during excavation. The data may be useful in anchoring soil mechanic models and to provide engineering data for design consideration.

  15. Fluid Dynamics Prize Talk: The Reactive Flow of Ideas

    NASA Astrophysics Data System (ADS)

    Oran, Elaine

    2013-11-01

    This presentation describes the evolution of our understanding of several key ideas in reactive flow from Ignorance to Discovery to Application and then again, to Ignorance. These key ideas describe the interactions of shock waves and turbulence with reaction fronts, and explain mechanisms for dynamic changes in the fundamental nature of the flow. They explain how flames undergo transitions from small ignition sources to turbulent flames to detonations, and how these energetic reactions waves may decay and die. Applications of the key ideas have been used to explain phenomena ranging from supernova explosions to catastrophic accidents in chemical plants. They have also helped to develop strategies for ensuring safety when we deal with energetic materials, and to create engines for high-speed flight. Now, however, we are at a turning point: By combining experimental observations with the most recent results of theory, advances in computational algorithms, and the ability to do large-scale numerical simulations, discrepancies arise that challenge well-established equations and approaches, both fluid and chemical. And so we must now ask: What is the origin of these discrepancies? What do we do next? With many thanks to friends and colleagues, and to NRL, ONR, AFOSR, and NASA for their support.

  16. Granular Flow and Dynamics of Lunar Simulants in Excavating Implements

    NASA Technical Reports Server (NTRS)

    Agui, Juan H.; Wilkinson, R. Allen

    2010-01-01

    The exploration of the lunar surface will rely on properly designed excavation equipment for surface preparations and for collection of lunar regolith in In-Situ Resource Utilization (ISRU) processes. Performance efficiency, i.e minimizing loading forces while maximizing material collection, and mass and volume reductions are major design goals. The NASA Glenn Research Center has embarked on an experimental program to determine the flow characteristics and dynamic forces produced by excavation operations using various excavator bucket designs. A new large scale soil bin facility, 2.27 m x 5.94 m x 0.76 m (nominally 8 ft. x 20 ft. x 27 in.) in size, capable of accommodating moderately large test implements was used for the simulations of lunar operations. The soil bin is filled with GRC-3simulant (a mixture of industrial sands and silt with a particle size distribution and the bulk mechanical (shear) strength representative of an average of lunar regolith from different regions) and uses motorized horizontal rails and a vertical actuator to drive the implement through the lunar simulant soil. A six-axis load cell and encoders provide well resolved measurements of the three dimensional forces and torques and motion of the bucket. In addition, simultaneous video allows for the analysis of the flow behavior and structure formation of the regolith during excavation. The data may be useful in anchoring soil mechanic models and to provide engineering data for design consideration.

  17. Upper mantle flow and lithospheric dynamics beneath the Eurasian region

    NASA Astrophysics Data System (ADS)

    Zhang, G.; Jiang, G.; Jia, Z.; Gao, R.; Fu, R.

    2010-12-01

    Evidence from seismic tomography, geothermal and short wavelength geoid anomalies reveals the existence of small-scale convective systems in the upper mantle, with scales ranging from 500 km to 700 km. It is reasonable to suggest that these small-scale convective systems probably control the regional tectonic structure and the dynamical processes of the lithosphere. Here we have calculated the patterns of small-scale convection in the upper mantle for the Eurasian region (20°E~170°E,15°N~75°N), using the anomaly of isostatic gravity. The results show that the regional lithospheric tectonics is strongly correlated with the upper mantle flow in the Eurasian region. Two intensive convective belts against the weak background convection can be recognized from convection patterns in this region: Alpine-Himalayan collision belt and West Pacific island arc-underthrust belt. Alpine-Himalayan belt is caused by the collision between the northern plate (Eurasian plate) and the southern plates (African plate and Indian plate). West Pacific island arc-underthrust belt is caused by the subduction of the Pacific plate beneath the Eurasian plate. Both of them are also seismotectonic belts. The collision and the subduction are two important geological events occurred since Mesozoic era and Cenozoic era in the Eurasian region. Therefore, the mantle flows may be one of the main driving forces of two events. In addition, most plate boundaries in this region can be recognized and the characteristics of upper mantle convection are different completely between the Eurasian plate and the plates around it (African plate, Arabian plate, Indian plate, Philippine Sea plate and Pacific plate). Main structures and geodynamic characteristics of the Eurasian can also be explained by our model results. The Tibet plateau is located in the intensive convective belt. Around the belt, the upwelling materials push the lithosphere to lift unitarily and form the plateau. Towards the north of the Tibet

  18. An ultrasonic flowmeter for measuring dynamic liquid flow

    NASA Technical Reports Server (NTRS)

    Carpini, T. D.; Monteith, J. H.

    1978-01-01

    A novel oscillating pipe system was developed to provide dynamic calibration wherein small sinusoidal signals with amplitudes of 0.5 to 10% of the steady-state flow were added to the steady-state flow by oscillating the flowmeter relative to the fixed pipes in the flow system. Excellent agreement was obtained between the dynamic velocities derived from an accelerometer mounted on the oscillating pipe system and those sensed by the flowmeter at frequencies of 7, 19, and 30 Hz. Also described were the signal processing techniques used to retrieve the small sinusoidal signals which were obscured by the fluid turbulence.

  19. Lava flow materials in the Tharsis region of Mars

    NASA Technical Reports Server (NTRS)

    Schaber, G. G.; Horstman, K. C.; Dial, A. L., Jr.

    1978-01-01

    Lava-flow materials in the Tharsis region of Mars were studied from moderate-resolution (100-280 m/pixel) Viking Orbiter imagery. Individual eruptive sequences were recognized primarily by stratigraphic relations, density of superimposed impact craters, flow morphology, flow trend, and variations in surface albedo. Nine detailed maps of lava flows based on delineation of flow scarps were compiled for a total area of 7.25 million sq km. Two thirds of this area was covered by mappable flows representing at least 14 distinct eruptive sequences. Assuming a rate of crater production twice that of the moon, the observed range of superimposed crater densities (90 to 3200 craters at least 1 km in diameter per sq km) indicates an age range of 100 m.y. to several billion years for these flows. The youngest lavas are associated with flood lavas filling the depression surrounding the Olympus Mons shield. Flow thicknesses range from less than 5 meters to 20 meters on steeper shield slopes (0.5 to 4.5 deg) and from 20 to 65 meters on relatively flat (less than 0.5 deg slope) terrain.

  20. Lava flow materials in the Tharsis region of Mars

    NASA Technical Reports Server (NTRS)

    Schaber, G. G.; Horstman, K. C.; Dial, A. L., Jr.

    1978-01-01

    Lava-flow materials in the Tharsis region of Mars were studied from moderate-resolution (100-280 m/pixel) Viking Orbiter imagery. Individual eruptive sequences were recognized primarily by stratigraphic relations, density of superimposed impact craters, flow morphology, flow trend, and variations in surface albedo. Nine detailed maps of lava flows based on delineation of flow scarps were compiled for a total area of 7.25 million sq km. Two thirds of this area was covered by mappable flows representing at least 14 distinct eruptive sequences. Assuming a rate of crater production twice that of the moon, the observed range of superimposed crater densities (90 to 3200 craters at least 1 km in diameter per sq km) indicates an age range of 100 m.y. to several billion years for these flows. The youngest lavas are associated with flood lavas filling the depression surrounding the Olympus Mons shield. Flow thicknesses range from less than 5 meters to 20 meters on steeper shield slopes (0.5 to 4.5 deg) and from 20 to 65 meters on relatively flat (less than 0.5 deg slope) terrain.

  1. Flow Visualization of Dynamic Stall on an Oscillating Airfoil

    DTIC Science & Technology

    1989-09-01

    Dynamic Stall; Dynamic lift, ’Unsteady lift; Helicopter retreating blade stall; Oscillating airfoil ; Flow visualization,’Schlieren method ;k ez.S-,’ .0...the degree of MASTER OF SCIENCE IN AERONAUTICAL ENGINEERING from the NAVAL POSTGRADUATE SCHOOL September 1989 Author...and moment behavior is quite different from the static stall associated with fixed-wing airfoils . Helicopter retreating blade stall is a dynamic

  2. Simulation of size segregation in granular flow with material point method

    NASA Astrophysics Data System (ADS)

    Fei, Minglong; Sun, Qicheng; Hill, Kimberly; Zhou, Gordon G. D.

    2017-06-01

    Segregation is common in granular flows consisting of mixtures of particles differing in size or density. In gravity-driven flows, both gradients in total pressure (induced by gravity) and gradients in velocity fluctuation fields (often associated with shear rate gradients) work together to govern the evolution of segregation. Since the local shear rate and velocity fluctuations are dependent on the local concentration of the components, understanding the co-evolution of segregation and flow is critical for understanding and predicting flows where there can be a variety of particle sizes and densities, such as in nature and industry. Kinetic theory has proven to be a robust framework for predicting this simultaneous evolution but has a limit in its applicability to dense systems where collisions are highly correlated. In this paper, we introduce a model that captures the coevolution of these evolving dynamics for high density gravity driven granular mixtures. For the segregation dynamics we use a recently developed mixture theory (Fan & Hill 2011, New J. Phys; Hill & Tan 2014, J. Fluid Mech.) which captures the combined effects of gravity and fluctuation fields on segregation evolution in high density granular flows. For the mixture flow dynamics, we use a recently proposed viscous-elastic-plastic constitutive model, which can describe the multi-state behaviors of granular materials, i.e. the granular solid, granular liquid and granular gas mechanical states (Fei et al. 2016, Powder Technol.). The platform we use for implementing this model is a modified Material Point Method (MPM), and we use discrete element method simulations of gravity-driven flow in an inclined channel to demonstrate that this new MPM model can predict the final segregation distribution as well as flow velocity profile well. We then discuss ongoing work where we are using this platform to test the effectiveness of particular segregation models under different boundary conditions.

  3. Computational Analysis of Material Flow During Friction Stir Welding of AA5059 Aluminum Alloys

    NASA Astrophysics Data System (ADS)

    Grujicic, M.; Arakere, G.; Pandurangan, B.; Ochterbeck, J. M.; Yen, C.-F.; Cheeseman, B. A.; Reynolds, A. P.; Sutton, M. A.

    2012-09-01

    Workpiece material flow and stirring/mixing during the friction stir welding (FSW) process are investigated computationally. Within the numerical model of the FSW process, the FSW tool is treated as a Lagrangian component while the workpiece material is treated as an Eulerian component. The employed coupled Eulerian/Lagrangian computational analysis of the welding process was of a two-way thermo-mechanical character (i.e., frictional-sliding/plastic-work dissipation is taken to act as a heat source in the thermal-energy balance equation) while temperature is allowed to affect mechanical aspects of the model through temperature-dependent material properties. The workpiece material (AA5059, solid-solution strengthened and strain-hardened aluminum alloy) is represented using a modified version of the classical Johnson-Cook model (within which the strain-hardening term is augmented to take into account for the effect of dynamic recrystallization) while the FSW tool material (AISI H13 tool steel) is modeled as an isotropic linear-elastic material. Within the analysis, the effects of some of the FSW key process parameters are investigated (e.g., weld pitch, tool tilt-angle, and the tool pin-size). The results pertaining to the material flow during FSW are compared with their experimental counterparts. It is found that, for the most part, experimentally observed material-flow characteristics are reproduced within the current FSW-process model.

  4. Dynamics and Control of Turbulent Shear Flows

    DTIC Science & Technology

    1989-05-01

    Significant Results A. Mathematical theory of channel flows. This is a joint research with Professor J. G. Heywood of the University of British Columbia. We...supported by URI contract). J. G. Heywood , Professor, University of British Columbia, consultant. I I I I I I I I I I I 37 Ii I AIAA-88-0134 l The...VISCOUS FLOW PAST PLANE DOMAINS WITH I NIONCOMPACT BOUNDARIES I gJ. G. Heywood Department of Mathematics 3 University of British Columbia I 3 S. S

  5. Controlling shockwave dynamics using architecture in periodic porous materials

    NASA Astrophysics Data System (ADS)

    Branch, Brittany; Ionita, Axinte; Clements, Bradford E.; Montgomery, David S.; Jensen, Brian J.; Patterson, Brian; Schmalzer, Andrew; Mueller, Alexander; Dattelbaum, Dana M.

    2017-04-01

    Additive manufacturing (AM) is an attractive approach for the design and fabrication of structures capable of achieving controlled mechanical response of the underlying deformation mechanisms. While there are numerous examples illustrating how the quasi-static mechanical responses of polymer foams have been tailored by additive manufacturing, there is limited understanding of the response of these materials under shockwave compression. Dynamic compression experiments coupled with time-resolved X-ray imaging were performed to obtain insights into the in situ evolution of shockwave coupling to porous, periodic polymer foams. We further demonstrate shock wave modulation or "spatially graded-flow" in shock-driven experiments via the spatial control of layer symmetries afforded by additive manufacturing techniques at the micron scale.

  6. Inhomogeneous shear flows in soft jammed materials with tunable attractive forces.

    PubMed

    Chaudhuri, Pinaki; Berthier, Ludovic; Bocquet, Lydéric

    2012-02-01

    We perform molecular dynamics simulations to characterize the occurrence of inhomogeneous shear flows in soft jammed materials. We use rough walls to impose a simple shear flow and study the athermal motion of jammed assemblies of soft particles in two spatial dimensions, both for purely repulsive interactions and in the presence of an additional short-range attraction of varying strength. In steady state, pronounced flow inhomogeneities emerge for all systems when the shear rate becomes small. Deviations from linear flow are stronger in magnitude and become very long lived when the strength of the attraction increases, but differ from permanent shear bands. Flow inhomogeneities occur in a stress window bounded by the dynamic and static yield stress values. Attractive forces enhance the flow heterogeneities because they accelerate stress relaxation, thus effectively moving the system closer to the yield stress regime where inhomogeneities are most pronounced. The present scenario for understanding the effect of particle adhesion on shear localization, which is based on detailed molecular dynamics simulations with realistic particle interactions, differs qualitatively from previous qualitative explanations and ad hoc theoretical modeling.

  7. Pattern Dynamics in Taylor Vortex Flow with Double Hourglass Geometry

    NASA Astrophysics Data System (ADS)

    Wiener, Richard; Olsen, Thomas

    2005-11-01

    In previous investigations ootnotetextWiener et al., Phys. Rev. E 55, 5489 (1997) & Phys. Rev. Lett. 83, 2340 (1999) we have demonstrated experimentally that Taylor vortex flow in an hourglass geometry undergoes a period-doubling cascade to chaotic pattern dynamics that can be controlled by proportional feedback with small perturbations. The hourglass geometry creates a spatial ramp in the Reynolds number. This results in a region of supercritical vortex flow between regions of subcritical structureless flow that provide the pattern with soft boundaries that allow for persistent dynamics. For a range of reduced Reynolds numbers, the Taylor vortex pattern exhibits persistent dynamics consisting of drifting and stretching vortices punctuated with phase slips. Each phase slip corresponds to the generation of a new vortex pair. We are currently investigating the phase dynamics of Tayor vortex flow with a double hourglass geometry which consists of two regions of supercritical flow in which phase slips occur, separated by a narrow region of subcritical flow. Initial results indicate that at some reduced Reynolds numbers there is synchronization between the vortex dynamics in the two regions, both in the temporal occurrence of the phase slips as well as the drift directions of the vortices.

  8. Sample Preheating Capability for Dynamic Material Studies*

    NASA Astrophysics Data System (ADS)

    Wise, J.; Dalton, D.; Hickman, R.; Kaufman, M.; Leffler, S.; Jones, M.; Lynch, J.; Bowers, A.

    2013-06-01

    Coordinated analysis, design, software development, hardware fabrication, and testing activities have yielded a new control system and experimental load design for dynamic material studies on specimens heated to temperatures exceeding 650°C prior to high-rate compression on a pulsed-power (e.g., Z machine) or gun platform. A proportional integral derivative controller supplies power for up to 16 resistive cartridge heaters mounted in a load assembly containing one or more test samples. The electrical output from this LabVIEW-based controller to each heater is continuously adjusted using feedback from thermocouples embedded in the load and in each heater. Experiments confirm steady temperature regulation to within +/-2°C of the selected set point, as well as adequate surge protection from built-in electromagnetic pulse isolation circuitry. ANSYS thermomechanical simulations have guided the refinement of load design to minimize sample temperature gradients and thermal distortion. Improved thin-film coatings for the sample/window interface are being developed to ensure the viability of velocity interferometry measurements on preheated samples. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000;

  9. Influence of cooling on lava-flow dynamics

    NASA Astrophysics Data System (ADS)

    Stasiuk, Mark V.; Jaupart, Claude; Stephen, R.; Sparks, J.

    1993-04-01

    Experiments have been carried out to determine the effects of cooling on the flow of fluids with strongly temperature dependent viscosity. Radial viscous-gravity currents of warm glucose syrup were erupted at constant rate into a flat tank filled with a cold aqueous solution. Cold, viscous fluid accumulates at the leading edge, altering the flow shape and thickness and slowing the spreading. The flows attain constant internal temperature distributions and bulk viscosities. The value of the bulk viscosity depends on the Péclet number, which reflects the advective and diffusive heat transport properties of the flow, the flow skin viscosity, which reflects cooling, and the eruption viscosity. Our results explain why most lava flows have bulk viscosities much higher than the lava eruption viscosity. The results can be applied to understanding dynamic lava features such as flow-front thickening, front avalanches, and welded basal breccias.

  10. On the Thermal Model of Transverse Flow of Unidirectional Materials

    NASA Technical Reports Server (NTRS)

    Tai, Hsiang

    2002-01-01

    The thermal model for transverse heat flow of having single filament in a unit cell is extended. In this model, we proposed that two circular filaments in a unit cell of square packing array and obtained the transverse thermal conductivity of an unidirectional material.

  11. Dynamic-Active Flow Control - Phase I

    DTIC Science & Technology

    2006-10-18

    Section, 4: Plenum Chamber, 5: Rear Observation Window, 6: Return Pipework , 7: Filtration Isolation Valve, 8: AC Motor and Centrifugal Pump, 10: Return... Pipework (pressure side), 11: Filtration Circuit. A large settling chamber existed upstream of the test section. The pump flow was introduced

  12. Dynamics of annular two-phase flow

    NASA Astrophysics Data System (ADS)

    Sawant, Pravin Hanamantrao

    A basic understanding of various hydrodynamic phenomena in annular two-phase is essential to develop mechanistic model for the prediction dryout. The major objective of this investigation was to perform experimental and theoretical analysis of the important hydrodynamic phenomena such as droplet entrainment, droplet deposition, and liquid film interfacial waves in vertical annular two-phase flow. Towards this end, adiabatic air-water and organic fluid (Freon-113) annular flow experiments have been conducted in 1 cm diameter test sections at pressures up to 6 and 8.5 bar, respectively. The organic fluid experiments simulated high pressure steam-water conditions representative of dryout in the Advanced Boiling Water Reactor (ABWR). A liquid film extraction method was applied for the measurement of entrainment fraction, droplet entrainment rate, and droplet deposition rate. Instantaneous liquid film thickness was measured in the air-water experiments using ring shaped conductance probes and properties of interfacial waves were estimated from the statistical analysis of the film thickness measurement. Detailed analysis of the experimental data revealed several inadequacies of the existing annular flow correlations available for the predictions of entrainment fraction, droplet entrainment rate, and droplet deposition rate including their inability to predict the limiting conditions observed under high gas phase velocity. Based on the detailed analysis of the air-water data, a new, non-dimensional and explicit correlation was developed for the prediction of entrainment fraction. The new correlation accounted for the existence of an upper limit on entrainment fraction as well as for the existence of critical liquid and gas velocities below which no entrainment is possible. Additionally, an improved correlation was proposed for the estimation of minimum liquid film flow rate at the maximum entrainment fraction. The newly developed entrainment fraction correlation

  13. Disturbance Dynamics in Transitional and Turbulent Flows

    NASA Technical Reports Server (NTRS)

    Grosch, Chester E.

    1999-01-01

    In order to expand the predictive capability of single-point turbulence closure models to account for the early-stage transition regime, a methodology for the formulation and calibration of model equations for the ensemble-averaged disturbance kinetic energy and energy dissipation rate is presented. First the decay of laminar disturbances and turbulence in mean shear-free flows is studied. In laminar flows, such disturbances are linear superpositions of modes governed by the Orr-Sommerfeld equation. In turbulent flows, disturbances are described through transport equations for representative mean quantities. The link between a description based on a deterministic evolution equation and a probability based mean transport equation is established. Because an uncertainty in initial conditions exists in the laminar as well as the turbulent regime, a probability distribution must be defined even in the laminar case. Using this probability distribution, it is shown that the exponential decay of the linear modes in the laminar regime can be related to a power law decay of both the (ensemble) mean disturbance kinetic energy and the dissipation rate. The evolution of these mean disturbance quantities is then described by transport equations similar to those for the corresponding turbulent decaying flow. Second, homogeneous shear flow, where disturbances can be described by rapid distortion theory (RDT), is studied. The relationship between RDT and linear stability theory is exploited in order to obtain a closed set of modeled equations. The linear disturbance equations are solved directly so that the numerical simulation yields a database from which the closure coefficients in the ensemble-averaged disturbance equations can be determined.

  14. Analysis of Material Flow in Screw Extrusion of Aluminum

    SciTech Connect

    Haugen, Bjoern; Oernskar, Magnus; Welo, Torgeir; Wideroee, Fredrik

    2010-06-15

    Screw extrusion of aluminum is a new process for production of aluminum profiles. The commercial potential could be large. Little experimental and numerical work has been done with respect to this process.The material flow of hot aluminum in a screw extruder has been analyzed using finite element formulations for the non-Newtonian Navier-Stokes equations. Aluminum material properties are modeled using the Zener-Holloman material model. Effects of stick-slip conditions are investigated with respect to pressure build up and mixing quality of the extrusion process.The numerical results are compared with physical experiments using an experimental screw extruder.

  15. Robust optimal control of material flows in demand-driven supply networks

    NASA Astrophysics Data System (ADS)

    Laumanns, Marco; Lefeber, Erjen

    2006-04-01

    We develop a model based on stochastic discrete-time controlled dynamical systems in order to derive optimal policies for controlling the material flow in supply networks. Each node in the network is described as a transducer such that the dynamics of the material and information flows within the entire network can be expressed by a system of first-order difference equations, where some inputs to the system act as external disturbances. We apply methods from constrained robust optimal control to compute the explicit control law as a function of the current state. For the numerical examples considered, these control laws correspond to certain classes of optimal ordering policies from inventory management while avoiding, however, any a priori assumptions about the general form of the policy.

  16. Discharge effects on gas flow dynamics in a plasma jet

    NASA Astrophysics Data System (ADS)

    Xian, Yu Bin; Hasnain Qaisrani, M.; Yue, Yuan Fu; Lu, Xin Pei

    2016-10-01

    Plasma is used as a flow visualization method to display the gas flow of a plasma jet. Using this method, it is found that a discharge in a plasma jet promotes the transition of the gas flow to turbulence. A discharge at intermediate frequency (˜6 kHz in this paper) has a stronger influence on the gas flow than that at lower or higher frequencies. Also, a higher discharge voltage enhances the transition of the gas flow to turbulence. Analysis reveals that pressure modulation induced both by the periodically directed movement of ionized helium and Ohmic heating on the gas flow plays an important role in inducing the transition of the helium flow regime. In addition, since the modulations induced by the high- and low-frequency discharges are determined by the frequency-selective effect, only intermediate-frequency (˜6 kHz) discharges effectively cause the helium flow transition from the laminar to the turbulent flow. Moreover, a discharge with a higher applied voltage makes a stronger impact on the helium flow because it generates stronger modulations. These conclusions are useful in designing cold plasma jets and plasma torches. Moreover, the relationship between the discharge parameters and the gas flow dynamics is a useful reference on active flow control with plasma actuators.

  17. Dynamic importance of unsteady effects in glottal flow aerodynamics

    NASA Astrophysics Data System (ADS)

    Krane, Michael; Peltier, Joel; Medvitz, Richard

    2008-11-01

    Finite element computations of flow through a constriction are used to illuminate the role of unsteady flow dynamics in glottal flow and voice production. Unsteady computations were performed for a series of prescribed idealized vocal fold wall motions over reduced frequencies f*=0, 0.04 and 0.08, which correspond to quasi-steady, adult male and adult female speaking voices, respectively. Glottal resistance and estimates of the relative magnitudes of the various terms of the integral momentum equation are presented. Results suggest that glottal flow is inherently unsteady.

  18. The very local Hubble flow: Computer simulations of dynamical history

    NASA Astrophysics Data System (ADS)

    Chernin, A. D.; Karachentsev, I. D.; Valtonen, M. J.; Dolgachev, V. P.; Domozhilova, L. M.; Makarov, D. I.

    2004-02-01

    The phenomenon of the very local (≤3 Mpc) Hubble flow is studied on the basis of the data of recent precision observations. A set of computer simulations is performed to trace the trajectories of the flow galaxies back in time to the epoch of the formation of the Local Group. It is found that the ``initial conditions'' of the flow are drastically different from the linear velocity-distance relation. The simulations enable one also to recognize the major trends of the flow evolution and identify the dynamical role of universal antigravity produced by the cosmic vacuum.

  19. The Steady Flow Resistance of Perforated Sheet Materials in High Speed Grazing Flows

    NASA Technical Reports Server (NTRS)

    Syed, Asif A.; Yu, Jia; Kwan, H. W.; Chien, E.; Jones, Michael G. (Technical Monitor)

    2002-01-01

    A study was conducted to determine the effects of high speed grazing air flow on the acoustic resistance of perforated sheet materials used in the construction of acoustically absorptive liners placed in commercial aircraft engine nacelles. Since DC flow resistance of porous sheet materials is known to be a major component of the acoustic resistance of sound suppression liners, the DC flow resistance of a set of perforated face-sheets and linear 'wiremesh' face-sheets was measured in a flow duct apparatus (up to Mach 0.8). Samples were fabricated to cover typical variations in perforated face-sheet parameters, such as hole diameter, porosity and sheet thickness, as well as those due to different manufacturing processes. The DC flow resistance data from perforated sheets were found to correlate strongly with the grazing flow Mach number and the face-sheet porosity. The data also show correlation against the boundary layer displacement thickness to hole-diameter ratio. The increase in resistance with grazing flow for punched aluminum sheets is in good agreement with published results up to Mach 0.4, but is significantly larger than expected above Mach 0.4. Finally, the tests demonstrated that there is a significant increase in the resistance of linear 'wiremesh' type face-sheet materials.

  20. Code System to Calculate Tornado-Induced Flow Material Transport.

    SciTech Connect

    ANDRAE, R. W.

    1999-11-18

    Version: 00 TORAC models tornado-induced flows, pressures, and material transport within structures. Its use is directed toward nuclear fuel cycle facilities and their primary release pathway, the ventilation system. However, it is applicable to other structures and can model other airflow pathways within a facility. In a nuclear facility, this network system could include process cells, canyons, laboratory offices, corridors, and offgas systems. TORAC predicts flow through a network system that also includes ventilation system components such as filters, dampers, ducts, and blowers. These ventilation system components are connected to the rooms and corridors of the facility to form a complete network for moving air through the structure and, perhaps, maintaining pressure levels in certain areas. The material transport capability in TORAC is very basic and includes convection, depletion, entrainment, and filtration of material.

  1. Distinguishing features of flow in heterogeneous porous media: 4, Is a more general dynamic description required

    SciTech Connect

    Nelson, R.W.

    1990-11-01

    Groundwater theory that applies to only homogeneous systems is often too restricted to adequately solve actual groundwater pollution problems. For adequate solutions, the more general theory for heterogeneous porous systems is needed. However, the present dynamic and kinematic descriptions in heterogeneous materials have evolved largely from the restricted and less general homogeneous theory. These descriptions are inadequate because they fail to account for all the energy dissipation in the system. The basic distinguishing dynamic feature of heterogeneous flow theory from the less general homogeneous-based theory is the macroscopic rotational flow component. Specifically, existence of rotational flow components and their independence from the translational flow components are the necessary and sufficient conditions that completely differentiate between the complex lamellar heterogeneous flow theory and the simpler lamellar flow of homogeneous theory. This paper proposes a more general dynamic form of the flow equation to include the added rotational dissipation that is missing from the present Darcian description of flow in heterogeneous media. 31 refs.

  2. Active dynamics of tissue shear flow

    NASA Astrophysics Data System (ADS)

    Popović, Marko; Nandi, Amitabha; Merkel, Matthias; Etournay, Raphaël; Eaton, Suzanne; Jülicher, Frank; Salbreux, Guillaume

    2017-03-01

    We present a hydrodynamic theory to describe shear flows in developing epithelial tissues. We introduce hydrodynamic fields corresponding to state properties of constituent cells as well as a contribution to overall tissue shear flow due to rearrangements in cell network topology. We then construct a generic linear constitutive equation for the shear rate due to topological rearrangements and we investigate a novel rheological behaviour resulting from memory effects in the tissue. We identify two distinct active cellular processes: generation of active stress in the tissue, and actively driven topological rearrangements. We find that these two active processes can produce distinct cellular and tissue shape changes, depending on boundary conditions applied on the tissue. Our findings have consequences for the understanding of tissue morphogenesis during development.

  3. Zonal flow dynamics in the double tearing mode with antisymmetric shear flows

    SciTech Connect

    Mao, Aohua; Li, Jiquan; Liu, Jinyuan; Kishimoto, Yasuaki

    2014-05-15

    The generation dynamics and the structural characteristics of zonal flows are investigated in the double tearing mode (DTM) with antisymmetric shear flows. Two kinds of zonal flow oscillations are revealed based on reduced resistive magnetohydrodynamics simulations, which depend on the shear flow amplitudes corresponding to different DTM eigen mode states, elaborated by Mao et al. [Phys. Plasmas 20, 022114 (2013)]. For the weak shear flows below an amplitude threshold, v{sub c}, at which two DTM eigen states with antisymmetric or symmetric magnetic island structure are degenerated, the zonal flows grow oscillatorily in the Rutherford regime during the nonlinear evolution of the DTMs. It is identified that the oscillation mechanism results from the nonlinear interaction between the distorted islands and the zonal flows through the modification of shear flows. However, for the medium shear flows above v{sub c} but below the critical threshold of the Kelvin-Helmholtz instability, an oscillatory growing zonal flow occurs in the linear phase of the DTM evolution. It is demonstrated that the zonal flow oscillation originates from the three-wave mode coupling or a modulation instability pumped by two DTM eigen modes with the same frequency but opposite propagating direction. With the shear flows increasing, the amplitude of zonal flow oscillation increases first and then decreases, whilst the oscillation frequency as twice of the Doppler frequency shift increases. Furthermore, impacts of the oscillatory zonal flows on the nonlinear evolution of DTM islands and the global reconnection are also discussed briefly.

  4. A material with electrically tunable strength and flow stress.

    PubMed

    Jin, Hai-Jun; Weissmüller, Jörg

    2011-06-03

    The selection of a structural material requires a compromise between strength and ductility. The material properties will then be set by the choice of alloy composition and microstructure during synthesis and processing, although the requirements may change during service life. Materials design strategies that allow for a recoverable tuning of the mechanical properties would thus be desirable, either in response to external control signals or in the form of a spontaneous adaptation, for instance in self-healing. We have designed a material that has a hybrid nanostructure consisting of a strong metal backbone that is interpenetrated by an electrolyte as the second component. By polarizing the internal interface via an applied electric potential, we accomplish fast and repeatable tuning of yield strength, flow stress, and ductility. The concept allows the user to select, for instance, a soft and ductile state for processing and a high-strength state for service as a structural material.

  5. Horizontal mantle flow controls subduction dynamics.

    PubMed

    Ficini, E; Dal Zilio, L; Doglioni, C; Gerya, T V

    2017-08-08

    It is generally accepted that subduction is driven by downgoing-plate negative buoyancy. Yet plate age -the main control on buoyancy- exhibits little correlation with most of the present-day subduction velocities and slab dips. "West"-directed subduction zones are on average steeper (~65°) than "East"-directed (~27°). Also, a "westerly"-directed net rotation of the lithosphere relative to the mantle has been detected in the hotspot reference frame. Thus, the existence of an "easterly"-directed horizontal mantle wind could explain this subduction asymmetry, favouring steepening or lifting of slab dip angles. Here we test this hypothesis using high-resolution two-dimensional numerical thermomechanical models of oceanic plate subduction interacting with a mantle flow. Results show that when subduction polarity is opposite to that of the mantle flow, the descending slab dips subvertically and the hinge retreats, thus leading to the development of a back-arc basin. In contrast, concordance between mantle flow and subduction polarity results in shallow dipping subduction, hinge advance and pronounced topography of the overriding plate, regardless of their age-dependent negative buoyancy. Our results are consistent with seismicity data and tomographic images of subduction zones. Thus, our models may explain why subduction asymmetry is a common feature of convergent margins on Earth.

  6. Gas bubble dynamics in soft materials.

    PubMed

    Solano-Altamirano, J M; Malcolm, John D; Goldman, Saul

    2015-01-07

    Epstein and Plesset's seminal work on the rate of gas bubble dissolution and growth in a simple liquid is generalized to render it applicable to a gas bubble embedded in a soft elastic solid. Both the underlying diffusion equation and the expression for the gas bubble pressure were modified to allow for the non-zero shear modulus of the medium. The extension of the diffusion equation results in a trivial shift (by an additive constant) in the value of the diffusion coefficient, and does not change the form of the rate equations. But the use of a generalized Young-Laplace equation for the bubble pressure resulted in significant differences on the dynamics of bubble dissolution and growth, relative to an inviscid liquid medium. Depending on whether the salient parameters (solute concentration, initial bubble radius, surface tension, and shear modulus) lead to bubble growth or dissolution, the effect of allowing for a non-zero shear modulus in the generalized Young-Laplace equation is to speed up the rate of bubble growth, or to reduce the rate of bubble dissolution, respectively. The relation to previous work on visco-elastic materials is discussed, as is the connection of this work to the problem of Decompression Sickness (specifically, "the bends"). Examples of tissues to which our expressions can be applied are provided. Also, a new phenomenon is predicted whereby, for some parameter values, a bubble can be metastable and persist for long times, or it may grow, when embedded in a homogeneous under-saturated soft elastic medium.

  7. Embrittlement and Flow Localization in Reactor Structural Materials

    SciTech Connect

    Xianglin Wu; Xiao Pan; James Stubbins

    2006-10-06

    Many reactor components and structural members are made from metal alloys due, in large part, to their strength and ability to resist brittle fracture by plastic deformation. However, brittle fracture can occur when structural material cannot undergo extensive, or even limited, plastic deformation due to irradiation exposure. Certain irradiation conditions lead to the development of a damage microstructure where plastic flow is limited to very small volumes or regions of material, as opposed to the general plastic flow in unexposed materials. This process is referred to as flow localization or plastic instability. The true stress at the onset of necking is a constant regardless of the irradiation level. It is called 'critical stress' and this critical stress has strong temperature dependence. Interrupted tensile testes of 316L SS have been performed to investigate the microstructure evolution and competing mechanism between mechanic twinning and planar slip which are believed to be the controlling mechanism for flow localization. Deformation twinning is the major contribution of strain hardening and good ductility for low temperatures, and the activation of twinning system is determined by the critical twinning stress. Phases transform and texture analyses are also discussed in this study. Finite element analysis is carried out to complement the microstructural analysis and for the prediction of materaials performance with and without stress concentration and irradiation.

  8. Computation of free-molecular flow in nuclear materials

    NASA Astrophysics Data System (ADS)

    Casella, Andrew M.; Loyalka, Sudarshan K.; Hanson, Brady D.

    2009-11-01

    Generally, the transport of gases and vapors in nuclear materials is adequately described by the diffusion equation with an effective diffusion coefficient. There are instances however, in which the flow pathway can be so restrictive that the diffusion description has limitations. In general, molecular transport is governed by intermolecular forces and collisions (interactions between multiple gas/vapor molecules) and by molecule-surface interactions. However, if nano-scale pathways exist within these materials, as has been suggested, then molecular transport can be characterized as being in the free-molecular flow regime where intermolecular interactions can be ignored and flow is determined entirely by molecule-surface collisions. Our purpose in this investigation is to focus on free-molecular transport in fine capillaries of a range of shapes and to explore the effect of geometry on this transport. We have employed Monte Carlo techniques in our calculations, and for simple geometries we have benchmarked our results against some analytical and previously available results. We have used Mathematica ® which has exceptional built-in symbolic and graphical capabilities, permitting easy handling of complicated geometries and good visualization of the results. Our computations provide insights into the role of geometry in molecular transport in nuclear materials with narrow pathways for flows, and also will be useful in guiding computations that include intermolecular collisions and more realistic gas-surface collision operators.

  9. Reutilisation-extended material flows and circular economy in China.

    PubMed

    Li, Nan; Zhang, Tianzhu; Liang, Sai

    2013-06-01

    Circular economy (CE), with its basic principle of Reduce, Reuse, and Recycle, has been determined as the key strategy for the national development plan by the Chinese government. Given the economy-wide material flow analysis (EW-MFA) that leaves the inner flow of resource reutilisation unidentified, the reutilisation-extended EW-MFA is first introduced to evaluate and analyse the material input, solid waste generation, and reutilisation simultaneously. The total amount of comprehensive reutilisation (CR) is divided into three sub-flows, namely, reutilisation, recycle, and reuse. Thus, this model is used to investigate the resource CR in China from 2000 to 2010. China's total amount of CR and its sub-flows, as well as the CR rate, remain to have a general upward trend. By the year 2010, about 60% of the overall solid waste generation had already been reutilised, and more than 20% of the total resource requirement was reutilised resource. Moreover, the growth patterns of the CR sub flows show different characteristics. Interpretations of resource reutilisation-related laws and regulations of CE and the corresponding policy suggestions are proposed based on the results. Copyright © 2013 Elsevier Ltd. All rights reserved.

  10. Angular dynamics of small crystals in viscous flow

    NASA Astrophysics Data System (ADS)

    Fries, J.; Einarsson, J.; Mehlig, B.

    2017-01-01

    The angular dynamics of a very small ellipsoidal particle in a viscous flow decouples from its translational dynamics and the particle angular velocity is given by Jeffery's theory. It is known that cuboid particles share these properties. In the literature a special case is most frequently discussed, namely that of axisymmetric particles with a continuous rotation symmetry. Here we compute the angular dynamics of crystals that possess a discrete rotation symmetry and certain mirror symmetries but do not have a continuous rotation symmetry. We give examples of such particles that nevertheless obey Jeffery's theory. However, there are other examples where the angular dynamics is determined by a more general equation of motion.

  11. Internet traffic load balancing using dynamic hashing with flow volume

    NASA Astrophysics Data System (ADS)

    Jo, Ju-Yeon; Kim, Yoohwan; Chao, H. Jonathan; Merat, Francis L.

    2002-07-01

    Sending IP packets over multiple parallel links is in extensive use in today's Internet and its use is growing due to its scalability, reliability and cost-effectiveness. To maximize the efficiency of parallel links, load balancing is necessary among the links, but it may cause the problem of packet reordering. Since packet reordering impairs TCP performance, it is important to reduce the amount of reordering. Hashing offers a simple solution to keep the packet order by sending a flow over a unique link, but static hashing does not guarantee an even distribution of the traffic amount among the links, which could lead to packet loss under heavy load. Dynamic hashing offers some degree of load balancing but suffers from load fluctuations and excessive packet reordering. To overcome these shortcomings, we have enhanced the dynamic hashing algorithm to utilize the flow volume information in order to reassign only the appropriate flows. This new method, called dynamic hashing with flow volume (DHFV), eliminates unnecessary flow reassignments of small flows and achieves load balancing very quickly without load fluctuation by accurately predicting the amount of transferred load between the links. In this paper we provide the general framework of DHFV and address the challenges in implementing DHFV. We then introduce two algorithms of DHFV with different flow selection strategies and show their performances through simulation.

  12. Multiphase imaging of gas flow in a nanoporous material usingremote detection NMR

    SciTech Connect

    Harel, Elad; Granwehr, Josef; Seeley, Juliette A.; Pines, Alex

    2005-10-03

    Pore structure and connectivity determine how microstructured materials perform in applications such as catalysis, fluid storage and transport, filtering, or as reactors. We report a model study on silica aerogel using a recently introduced time-of-flight (TOF) magnetic resonance imaging technique to characterize the flow field and elucidate the effects of heterogeneities in the pore structure on gas flow and dispersion with Xe-129 as the gas-phase sensor. The observed chemical shift allows the separate visualization of unrestricted xenon and xenon confined in the pores of the aerogel. The asymmetrical nature of the dispersion pattern alludes to the existence of a stationary and a flow regime in the aerogel. An exchange time constant is determined to characterize the gas transfer between them. As a general methodology, this technique provides new insights into the dynamics of flow in porous media where multiple phases or chemical species may be present.

  13. Eight energy and material flow characteristics of urban ecosystems.

    PubMed

    Bai, Xuemei

    2016-11-01

    Recent decades have seen an expanding literature exploring urban energy and material flows, loosely branded as urban metabolism analysis. However, this has occurred largely in parallel to the mainstream studies of cities as ecosystems. This paper aims to conceptually bridge these two distinctive fields of research, by (a) identifying the common aspects between them; (b) identifying key characteristics of urban ecosystems that can be derived from energy and material flow analysis, namely energy and material budget and pathways; flow intensity; energy and material efficiency; rate of resource depletion, accumulation and transformation; self-sufficiency or external dependency; intra-system heterogeneity; intersystem and temporal variation; and regulating mechanism and governing capacity. I argue that significant ecological insight can be, or has the potential to be, drawn from the rich and rapidly growing empirical findings of urban metabolism studies to understand the behaviour of cities as human-dominated, complex systems. A closer intellectual linkage and cross pollination between urban metabolism and urban ecosystem studies will advance our scientific understanding and better inform urban policy and management practices.

  14. Multimillion atom molecular dynamics simulations of glasses and ceramic materials

    NASA Astrophysics Data System (ADS)

    Vashishta, Priya; Kalia, Rajiv K.; Nakano, Aiichiro

    1999-11-01

    Molecular dynamics simulations are a powerful tool for studying physical and chemical phenomena in materials. In these lectures we shall review the molecular dynamics method and its implementation on parallel computer architectures. Using the molecular dynamics method we will study a number of materials in different ranges of density, temperature, and uniaxial strain. These include structural correlations in silica glass under pressure, crack propagation in silicon nitride films, sintering of silicon nitride nanoclusters, consolidation of nanophase materials, and dynamic fracture. Multimillion atom simulations of oxidation of aluminum nanoclusters and nanoindentation in silicon nitride will also be discussed.

  15. Landslide on Valles Marineris: morphology and flow dynamics

    NASA Astrophysics Data System (ADS)

    Sato, H.; Kurita, K.; Baratoux, D.; Pinet, P.

    2008-09-01

    Introduction: Valles Marineris is known as a place of numerous and well preserved landslides on Mars. In comparison with terrestrial landslides, martian landslides are distinctive in their size and morphology. As a consequence of the topography of the canyon, the averaged drop height of these landslides is about 6.5 km and the averaged volume is about 102~4 km3[1], which is 2~3 orders of magnitude larger than terrestrial ones, at the exception of marine landslides[2]. As for the morphology, clear levees with longitudinal lineations are typical features of martian landslides, whereas surfaces of the terrestrial mass movements are dominated by a rather chaotic topography with, in some cases, the occurrence of transverse ridges. The characteristics of the deposits should reflect the dynamics of the emplacement and the subsurface material properties. In particular, there is a longstanding debate about the relation between the long run-out length and the existence of subsurface volatiles (water ice, clathrates, ground water) [1,3,4,5,6,7]. The motivation of our research is the fact that material properties are expected to be deduced from the morphology of the deposits and the knowledge of the flow dynamics. Then, the characteristics of subsurface materials partially collapsed as mass movements could be documented as a function of time, considering the age of each landslide. In this study, we focus on the longitudinal grooves which are found on the surface of landslide deposits at Valles Marineris (Fig.1). This pattern is a typical feature in the martian landslides[3], and extremely rarely observed in the terrestrial mass movements. The origin is not well clarified, but it seems strong relation with the flow style or physical property of transported materials. With the objective to determine the condition of formation of the lineations, the geometric characteristics (volume, surface, thickness, run-out length) of lineated and non-lineated landslides are compared. Then

  16. Dynamic flow control strategies of vehicle SCR Urea Dosing System

    NASA Astrophysics Data System (ADS)

    Lin, Wei; Zhang, Youtong; Asif, Malik

    2015-03-01

    Selective Catalyst Reduction(SCR) Urea Dosing System(UDS) directly affects the system accuracy and the dynamic response performance of a vehicle. However, the UDS dynamic response is hard to keep up with the changes of the engine's operating conditions. That will lead to low NO X conversion efficiency or NH3 slip. In order to optimize the injection accuracy and the response speed of the UDS in dynamic conditions, an advanced control strategy based on an air-assisted volumetric UDS is presented. It covers the methods of flow compensation and switching working conditions. The strategy is authenticated on an UDS and tested in different dynamic conditions. The result shows that the control strategy discussed results in higher dynamic accuracy and faster dynamic response speed of UDS. The inject deviation range is improved from being between -8% and 10% to -4% and 2% and became more stable than before, and the dynamic response time was shortened from 200 ms to 150 ms. The ETC cycle result shows that after using the new strategy the NH3 emission is reduced by 60%, and the NO X emission remains almost unchanged. The trade-off between NO X conversion efficiency and NH3 slip is mitigated. The studied flow compensation and switching working conditions can improve the dynamic performance of the UDS significantly and make the UDS dynamic response keep up with the changes of the engine's operating conditions quickly.

  17. Nonlinear Dynamic Properties of Layered Composite Materials

    SciTech Connect

    Andrianov, Igor V.; Topol, Heiko; Weichert, Dieter; Danishevs'kyy, Vladyslav V.

    2010-09-30

    We present an application of the asymptotic homogenization method to study wave propagation in a one-dimensional composite material consisting of a matrix material and coated inclusions. Physical nonlinearity is taken into account by considering the composite's components as a Murnaghan material, structural nonlinearity is caused by the bonding condition between the components.

  18. Field Flumes to Floodplains: Revealing the Influence of Flow Dynamics in Structuring Aquatic Ecosystems

    NASA Astrophysics Data System (ADS)

    Harvey, J. W.

    2011-12-01

    Decades of research has demonstrated the role of flood pulses in energy flow and nutrient cycling in large rivers. However, the study of hydroecology in small to medium size channels has often focused on static processes occurring during steady channel baseflow. Yet storm dynamics and their ecological effects are key issues for land managers responding to accelerating land use change in urban and agricultural areas, grazing lands, and in forested watersheds. As a means to understand the role of variable flows, researchers are increasingly moving towards study designs that explicitly address natural or experimentally altered flows in streams, or manipulation of flow in controlled "stair step" of experimental discharges in smaller field flumes. Studies often focus on both dissolved and fine particulate materials, their redistribution by stormflow, and physical effects of bedform migration and expansion and contraction of surface-water storage and hyporheic zones. In this framework investigators are seeking not only to identify the factors causing "hot spots" of biogeochemical transformation in streams, but also the "hot moments" related to flow variation and its interactions with geomorphic, sediment, and solute dynamics. Examples illustrating these advancements come from studies of flash floods from urban areas and their effects of solute and sediment dynamics in a 2nd order stream, nitrogen cycling and floodplain dynamics in a 5th order river, and longer term co-evolution of pulsed flow hydraulics, geomorphic form, and sediment and nutrient retention in two contrasting river and wetland corridors in the southwestern U.S. and southern Florida.

  19. Lattice fluid dynamics from perfect discretizations of continuum flows

    SciTech Connect

    Katz, E.; Wiese, U.

    1998-11-01

    We use renormalization group methods to derive equations of motion for large scale variables in fluid dynamics. The large scale variables are averages of the underlying continuum variables over cubic volumes and naturally exist on a lattice. The resulting lattice dynamics represents a perfect discretization of continuum physics, i.e., grid artifacts are completely eliminated. Perfect equations of motion are derived for static, slow flows of incompressible, viscous fluids. For Hagen-Poiseuille flow in a channel with a square cross section the equations reduce to a perfect discretization of the Poisson equation for the velocity field with Dirichlet boundary conditions. The perfect large scale Poisson equation is used in a numerical simulation and is shown to represent the continuum flow exactly. For nonsquare cross sections one can use a numerical iterative procedure to derive flow equations that are approximately perfect. {copyright} {ital 1998} {ital The American Physical Society}

  20. Flow in the well: computational fluid dynamics is essential in flow chamber construction

    PubMed Central

    Franke, Jörg; Frank, Wolfram; Schroten, Horst

    2007-01-01

    A perfusion system was developed to generate well defined flow conditions within a well of a standard multidish. Human vein endothelial cells were cultured under flow conditions and cell response was analyzed by microscopy. Endothelial cells became elongated and spindle shaped. As demonstrated by computational fluid dynamics (CFD), cells were cultured under well defined but time varying shear stress conditions. A damper system was introduced which reduced pulsatile flow when using volumetric pumps. The flow and the wall shear stress distribution were analyzed by CFD for the steady and unsteady flow field. Usage of the volumetric pump caused variations of the wall shear stresses despite the controlled fluid environment and introduction of a damper system. Therefore the use of CFD analysis and experimental validation is critical in developing flow chambers and studying cell response to shear stress. The system presented gives an effortless flow chamber setup within a 6-well standard multidish. PMID:19002993

  1. Flow in the well: computational fluid dynamics is essential in flow chamber construction.

    PubMed

    Vogel, Markus; Franke, Jörg; Frank, Wolfram; Schroten, Horst

    2007-09-01

    A perfusion system was developed to generate well defined flow conditions within a well of a standard multidish. Human vein endothelial cells were cultured under flow conditions and cell response was analyzed by microscopy. Endothelial cells became elongated and spindle shaped. As demonstrated by computational fluid dynamics (CFD), cells were cultured under well defined but time varying shear stress conditions. A damper system was introduced which reduced pulsatile flow when using volumetric pumps. The flow and the wall shear stress distribution were analyzed by CFD for the steady and unsteady flow field. Usage of the volumetric pump caused variations of the wall shear stresses despite the controlled fluid environment and introduction of a damper system. Therefore the use of CFD analysis and experimental validation is critical in developing flow chambers and studying cell response to shear stress. The system presented gives an effortless flow chamber setup within a 6-well standard multidish.

  2. Full dynamics of a red blood cell in shear flow.

    PubMed

    Dupire, Jules; Socol, Marius; Viallat, Annie

    2012-12-18

    At the cellular scale, blood fluidity and mass transport depend on the dynamics of red blood cells in blood flow, specifically on their deformation and orientation. These dynamics are governed by cellular rheological properties, such as internal viscosity and cytoskeleton elasticity. In diseases in which cell rheology is altered genetically or by parasitic invasion or by changes in the microenvironment, blood flow may be severely impaired. The nonlinear interplay between cell rheology and flow may generate complex dynamics, which remain largely unexplored experimentally. Under simple shear flow, only two motions, "tumbling" and "tank-treading," have been described experimentally and relate to cell mechanics. Here, we elucidate the full dynamics of red blood cells in shear flow by coupling two videomicroscopy approaches providing multidirectional pictures of cells, and we analyze the mechanical origin of the observed dynamics. We show that contrary to common belief, when red blood cells flip into the flow, their orientation is determined by the shear rate. We discuss the "rolling" motion, similar to a rolling wheel. This motion, which permits the cells to avoid energetically costly deformations, is a true signature of the cytoskeleton elasticity. We highlight a hysteresis cycle and two transient dynamics driven by the shear rate: an intermittent regime during the "tank-treading-to-flipping" transition and a Frisbee-like "spinning" regime during the "rolling-to-tank-treading" transition. Finally, we reveal that the biconcave red cell shape is highly stable under moderate shear stresses, and we interpret this result in terms of stress-free shape and elastic buckling.

  3. Effects of the Basal Boundary on Debris-flow Dynamics

    NASA Astrophysics Data System (ADS)

    Iverson, R. M.; Logan, M.; Lahusen, R. G.; Berti, M.

    2006-12-01

    Data aggregated from 37 large-scale experiments reveal some counterintuitive effects of bed roughness on debris-flow dynamics. In each experiment 10 m3 of water-saturated sand and gravel, mixed with 1 to 12% silt and clay by dry weight, was abruptly released from a gate at the head of a 2-m wide, 1.2-m deep, 82.5-m long rectangular flume inclined 31° throughout most of its length and adjoined to a gently sloping, planar runout surface at its toe. The flume's basal boundary consisted of either a smooth, planar concrete surface or a concrete surface roughened with a grid of conical bumps. Tilt-table tests with dry debris-flow sediment showed that this roughness imparted a basal friction angle of 38°, comparable to the sediment's internal friction angle of 38-42°, whereas the smooth-bed friction angle was 28°. About 20 electronic sensors installed in the flume yielded data on flow speeds and depths as well as basal stresses and pore pressures. Behavior observed in all experiments included development of steep, unsaturated, coarse-grained debris-flow snouts and tapering, liquefied, fine-grained tails. Flows on the rough bed were typically about 50% thicker and 20% slower than flows on the smooth bed, although the rough bed caused snout steepening that enabled flow fronts to move faster than expected, given the increased bed friction. Moreover, flows on rough beds ran out further than flows on smooth beds owing to enhanced grain-size segregation and lateral levee formation. With the rough bed, measured basal stresses and pore pressures differed little from values expected from static gravitational loading of partially liquefied debris. With the smooth bed, however, measured basal stresses and pore pressures were nearly twice as large as expected values. This anomaly resulted from flow disturbance at the upstream lips of steel plates in which sensors were mounted. The lips produced barely visible ripples in otherwise smooth flow surfaces, yet sufficed to generate

  4. Fluid dynamics aspects of miniaturized axial-flow blood pump.

    PubMed

    Kang, Can; Huang, Qifeng; Li, Yunxiao

    2014-01-01

    Rotary blood pump (RBP) is a kind of crucial ventricular assist device (VAD) and its advantages have been evidenced and acknowledged in recent years. Among the factors that influence the operation performance and the durability of various rotary blood pumps, medium property and the flow features in pump's flow passages are conceivably significant. The major concern in this paper is the fluid dynamics aspects of such a kind of miniaturized pump. More specifically, the structural features of axial-flow blood pump and corresponding flow features are analyzed in detail. The narrow flow passage between blade tips and pump casing and the rotor-stator interaction (RSI) zone may exert a negative effect on the shear stress distribution in the blood flow. Numerical techniques are briefly introduced in view of their contribution to facilitating the optimal design of blood pump and the visualization of shear stress distribution and multiphase flow analysis. Additionally, with the development of flow measurement techniques, the high-resolution, effective and non-intrusive flow measurement techniques catering to the measurement of the flows inside rotary blood pumps are highly anticipated.

  5. Material development for laminar flow control wing panels

    NASA Technical Reports Server (NTRS)

    Meade, L. E.

    1977-01-01

    The absence of suitable porous materials or techniques for the economic perforation of surface materials has previously restricted the design of laminar flow control (LFC) wing panels to a consideration of mechanically slotted LFC surfaces. A description is presented of a program which has been conducted to exploit recent advances in materials and manufacturing technology for the fabrication of reliable porous or perforated LFC surface panels compatible with the requirements of subsonic transport aircraft. Attention is given to LFC design criteria, surface materials, surface concepts, the use of microporous composites, perforated composites, and perforated metal. The described program was successful in that fabrication processes were developed for producing predictable perforated panels both of composite and of metal.

  6. Material development for laminar flow control wing panels

    NASA Technical Reports Server (NTRS)

    Meade, L. E.

    1977-01-01

    The absence of suitable porous materials or techniques for the economic perforation of surface materials has previously restricted the design of laminar flow control (LFC) wing panels to a consideration of mechanically slotted LFC surfaces. A description is presented of a program which has been conducted to exploit recent advances in materials and manufacturing technology for the fabrication of reliable porous or perforated LFC surface panels compatible with the requirements of subsonic transport aircraft. Attention is given to LFC design criteria, surface materials, surface concepts, the use of microporous composites, perforated composites, and perforated metal. The described program was successful in that fabrication processes were developed for producing predictable perforated panels both of composite and of metal.

  7. Vortex dynamics in nonlinear free surface flows

    NASA Astrophysics Data System (ADS)

    Curtis, Christopher W.; Kalisch, Henrik

    2017-03-01

    The two-dimensional motion of point vortices in an inviscid fluid with a free surface and an impenetrable bed is investigated. The work is based on forming a closed system of equations for surface variables and vortex positions using a variant of the Ablowitz, Fokas, and Musslimani formulation [M. J. Ablowitz, A. S. Fokas, and Z. H. Musslimani, J. Fluid Mech. 562, 313-343 (2006)] of the water-wave free-surface problem. The equations are approximated with a dealiased spectral method making use of a high-order approximation of the Dirichlet-Neumann operator and a high-order time-stepping scheme. Numerical simulations reveal that the combination of vortex motion and solid bottom boundary yields interesting dynamics not seen in the case of vortex motion in an infinitely deep fluid. In particular, strong deformations of the free surface, including non-symmetric surface profiles and regions of large energy concentration, are observed. Our simulations also uncover a rich variety of vortex trajectories including orbiting and nearly parallel patterns of motion. The dynamics of the free surface and of the point vortices are strongly influenced by the initial placement and polarity of the vortices. The method put forward here is flexible enough to handle a large number of vortices and may easily be extended to include the effects of varying bathymetry, stratification, and background shear currents.

  8. Research on regulating technique of material flow for 2-person and 30-day integrated CELSS test

    NASA Astrophysics Data System (ADS)

    Guo, Shuangsheng; Dong, Wenping; Ai, Weidang; Feng, Hongqi; Tang, Yongkang; Huang, Zhide; Shen, Yunze; Ren, Jin; Qin, Lifeng; Zeng, Gu; Zhang, Lihong; Zhu, Jingtao; Fei, Jinxue; Xu, Guoxin

    2014-07-01

    A man-plant integration test was processed using the CELSS integration experiment platform in which 4 kinds of plants were grown (Lactuca sativa L var. Dasusheng, L. sativa L var. Youmaicai, Gynura bicolor and Cichorium endivia L) to exchange material with 2 persons in order to research the dynamic changing laws and balanced regulation of air and water between man and plant in an inclosed system. In the test the material flow was measured so that the dynamically changing laws and balanced regulation of air and water between man and plant in the closed system were mostly mastered. The material closure degree of air, water and food reached 100%, 90% and 13.9% respectively with the whole system closure degree up to 95.1%. Meanwhile, it was proved that a 13.5 m2 planting area could meet the demand of one person for O2 in the system, and the energy efficiency ratio of which reached 59.56 g/(kW m2 day). The material flow dynamic balance-regulating technology was initially mastered between man and plant through the test. The interaction was realized among man, plant and environment in the closed system, which is of great significance to the advancement of long-term manned environment control and life support technology for China.

  9. Dielectric Barrier Plasma Dynamics for Active Control of Separated Flows

    DTIC Science & Technology

    2006-01-01

    flow of neutrals , altering the dynamics of the inertial and adverse pressure gradient terms to eliminate the separation bubble. Since the neutral density...from charged particles to the neutrals results in an ener- gized near-wall flow, facilitating the elimination of a separa- tion bubble. Several...attack. A self-consistent model utilizing motion of electrons, ions, and neutrals is employed to couple the electric force field to the momentum of the

  10. Identification of internal flow dynamics in two experimental catchments

    USGS Publications Warehouse

    Hansen, D.P.; Jakeman, A.J.; Kendall, C.; Weizu, G.

    1997-01-01

    Identification of the internal flow dynamics in catchments is difficult because of the lack of information in precipitation -stream discharge time series alone. Two experimental catchments, Hydrohill and Nandadish, near Nanjing in China, have been set up to monitor internal flows reaching the catchment stream at various depths, from the surface runoff to the bedrock. With analysis of the precipitation against these internal discharges, it is possible to quantify the time constants and volumes associated with various flowpaths in both catchments.

  11. Fluid Dynamic Mechanisms and Interactions within Separated Flows

    DTIC Science & Technology

    1993-08-01

    for this research has I been Dr. Thomas L. Doligalski, Chief, Fluid Dynamics Branch, Engineering and Environmental Sciences Division. The authors of...KOOIO, with Thomas L. gation of the Effects of a Base Cavity on the Near-Wake Flowfiel od a Body at Subsonic and Transonic Speeds," Department of...F.. Quincey , V. G., and Callinan, J., "Experiments on Flow." ARC R&M No. 3323. March 1962. Two-Dimensional Base Flow at Subsonic and Transonic Speeds

  12. Mineralogy of Deposit Material from Debris Flows, a Case Study

    NASA Astrophysics Data System (ADS)

    Bardou, E.; Petrova, S.; Favre-Boivin, F.; Boivin, P.

    2003-04-01

    Extended survey on debris flow deposits show a wide variety of morphology, from well defined boundaries with smooth surface (muddy debris flow) to vague boundaries with rough surface (granular debris flow). To explain these differences we investigated the morphological and mineralogical properties of some fresh debris flow deposits. Due to the wide influence of fine components on rheological properties, particular attention was given to characterization of these components. Debris flow deposits from 4 different watersheds where sampled and analysed. Mechanical analysis was performed using laser grain size analysis. Clay fraction was extracted and analysed using X-ray diffraction (XRD). Critical Coagulation Curves (CCC) of extracted clays where established for a large range of Sodium Adsorption Ratio (SAR) and Total Electrolyte Concentration (TEC) and where compared. The grains size distribution shows significant differences between the different kind of deposit, mainly on the fine fraction (clays and silts). This figures the importance of the fine content of the whole mass on the mechanical behaviour. XRD analysis show sharp differences between the extracted clays. Two of the deposits contain a high proportion of smectites, which are well known to be far much dispersive than the other clays identified (mainly illite, chlorite and vermiculite). CCC determinations are in good agreement with XRD results. The clays with appreciable amount of smectite have much higher CCC values than others. This means that these clays will disperse more easily, and will induce lower shear strength of materials as previously demonstrated in literature. Moreover, it is suspected that a major proportion of the more dispersive clay was leached during deposition. The results of the mineralogical analysis and the deposit shape can be correlated. This could be a valuable tool for risk assessment in watershed prone to debris flows. Therefore, it is suggested that more attention should be given

  13. Flapping dynamics of an inverted flag in a uniform flow

    NASA Astrophysics Data System (ADS)

    Ryu, Jaeha; Park, Sung Goon; Kim, Boyoung; Sung, Hyung Jin

    2015-11-01

    Much research in recent years has focused on the flow dynamics of flexible structures in a uniform flow and particularly on the flow dynamics related to energy harvesting systems. An energy harvesting system comprising piezoelectric patches attached to the surface of a flexible structure can convert the energy stored in solid deformations into an electric current that powers a purely resistive output circuit. Recently, an inverted flag which has the freely moving leading edge and the clamped trailing edge was suggested. The inverted flag improved the amount of strain energy that was converted into the flag deformations from the surrounding fluid. In this study, the flapping dynamics of an inverted flag in a uniform flow were simulated using the immersed boundary method. The flapping dynamics of and vortical structures around the inverted flag were examined in terms of the bending rigidity and the Reynolds number. The strain energy of the inverted flag and the proportion of the strain energy of the inverted flag to the kinetic energy of the flow were considered as an indicator of the energy harvesting system efficiency.

  14. Nonlinear dynamics of tube arrays in cross flow

    SciTech Connect

    Chen, S.S.; Cai, Y.; Zhu, S.

    1994-04-01

    Fluidelastic instability of loosely supported tube arrays was studied analytically and experimentally. This is one of the important practical problems of autonomous fluid-structure systems with many interesting motions. Both fluid-damping and fluid-stiffness controlled instabilities were investigated. Depending on the system parameter, the dynamic response of the tubes includes periodic, quasiperiodic, and chaotic motions. The analytical model is based on the unsteady flow theory, which can predict the nonlinear dynamics of tube arrays in cross flow. For fluid-damping controlled instability, analytical results and experimental data agree reasonably well. This study was applied to heat exchangers.

  15. Multiscale modelling of plastic flow localization in irradiated materials

    NASA Astrophysics Data System (ADS)

    Diaz de la Rubia, Tomas; Zbib, Hussein M.; Khraishi, Tariq A.; Wirth, Brian D.; Victoria, Max; Caturla, Maria Jose

    2000-08-01

    The irradiation of metals by energetic particles causes significant degradation of the mechanical properties, most notably an increased yield stress and decreased ductility, often accompanied by plastic flow localization. Such effects limit the lifetime of pressure vessels in nuclear power plants, and constrain the choice of materials for fusion-based alternative energy sources. Although these phenomena have been known for many years, the underlying fundamental mechanisms and their relation to the irradiation field have not been clearly demonstrated. Here we use three-dimensional multiscale simulations of irradiated metals to reveal the mechanisms underlying plastic flow localization in defect-free channels. We observe dislocation pinning by irradiation-induced clusters of defects, subsequent unpinning as defects are absorbed by the dislocations, and cross-slip of the latter as the stress is increased. The width of the plastic flow channels is limited by the interaction among opposing dislocation dipole segments and the remaining defect clusters.

  16. Complex Dynamics of Compound Vesicles in Linear Flow

    NASA Astrophysics Data System (ADS)

    Levant, Michael; Steinberg, Victor

    2014-04-01

    We report first experimental observations of dynamics of compound vesicles in linear flow realized in a microfluidic four-roll mill. We show that while a compound vesicle undergoes the same main tank-treading, trembling (TR), and tumbling regimes, its dynamics are far richer and more complex than that of unilamellar vesicles. A new swinging motion of the inner vesicle is found in TR in accord with simulations. The inner and outer vesicles can exist simultaneously in different dynamical regimes and can undergo either synchronized or unsynchronized motions depending on the filling factor. A compound vesicle can be used as a physical model to study white blood cell dynamics in flow similar to a unilamellar vesicle used successfully to model anucleate cells.

  17. Angular dynamics of small crystals in viscous flows

    NASA Astrophysics Data System (ADS)

    Fries, Johan; Einarsson, Jonas; Mehlig, Bernhard

    2016-11-01

    The angular dynamics of a very small ellipsoidal particle in a viscous flow decouples from its translational dynamics, and the particle angular velocity is given by Jeffery's theory. It is known that cuboid particles share these properties. In the literature a special case is most frequently discussed, that of axisymmetric particles, with a continuous rotational symmetry. Here we compute the angular dynamics of crystals that possess a discrete rotational symmetry and certain mirror symmetries, but that do not have a continuous rotational symmetry. We give examples of such particles that nevertheless obey Jeffery's theory. But there are other examples where the angular dynamics is determined by a more general equation of motion. Vetenskapsrådet [Grant Number 2013-3992], Formas [Grant Number 2014-585], "Bottlenecks for particle growth in turbulent aerosols" from the Knut and Alice Wallenberg Foundation, Dnr. KAW 2014.0048, MPNS COST Action MP1305 "Flowing matter".

  18. Redistribution of energy flow in a material due to damping.

    PubMed

    Li, Xin; Pierce, Donna M; Arnoldus, Henk F

    2011-02-01

    The field lines of energy flow of the radiation emitted by a linear dipole in free space are straight lines, running radially outward from the source. When the dipole is embedded in a medium, the field lines are curves when the imaginary part of the relative permittivity is finite. It is shown that due to the damping in the material all radiation is emitted in directions perpendicular to the dipole axis, whereas for a dipole in free space the radiation is emitted in all directions except along the dipole axis. It is also shown that some field lines in the near field form semiloops. Energy flowing along these semiloops is absorbed by the material and does not contribute to the radiative power in the far field.

  19. Field-Flow Fractionation of Carbon Nanotubes and Related Materials

    SciTech Connect

    John P. Selegue

    2011-11-17

    During the grant period, we carried out FFF studies of carbonaceous soot, single-walled and multi-walled carbon nanotubes, carbon nano-onions and polyoxometallates. FFF alone does not provide enough information to fully characterize samples, so our suite of characterization techniques grew to include light scattering (especially Photon Correlation Spectroscopy), scanning and transmission electron microscopy, thermogravimetric analysis and spectroscopic methods. We developed convenient techniques to deposit and examine minute FFF fractions by electron microscopy. In collaboration with Arthur Cammers (University of Kentucky), we used Flow Field-Flow Fractionation (Fl-FFF) to monitor the solution-phase growth of keplerates, a class of polyoxometallate (POM) nanoparticles. We monitored the evolution of Mo-POM nanostructures over the course of weeks by by using flow field-flow fractionation and corroborated the nanoparticle structures by using transmission electron microscopy (TEM). Total molybdenum in the solution and precipitate phases was monitored by using inductively coupled plasma analyses, and total Mo-POM concentration by following the UV-visible spectra of the solution phase. We observe crystallization-driven formation of (Mo132) keplerate and solution phase-driven evolution of structurally related nanoscopic species (3-60 nm). FFF analyses of other classes of materials were less successful. Attempts to analyze platelets of layered materials, including exfoliated graphite (graphene) and TaS2 and MoS2, were disappointing. We were not able to optimize flow conditions for the layered materials. The metal sulfides react with the aqueous carrier liquid and settle out of suspension quickly because of their high density.

  20. Stochastic dynamics of particles trapped in turbulent flows

    NASA Astrophysics Data System (ADS)

    Machicoane, N.; López-Caballero, M.; Fiabane, L.; Pinton, J.-F.; Bourgoin, M.; Burguete, J.; Volk, R.

    2016-02-01

    The long-time dynamics of large particles trapped in two nonhomogeneous turbulent shear flows is studied experimentally. Both flows present a common feature, a shear region that separates two colliding circulations, but with different spatial symmetries and temporal behaviors. Because large particles are less and less sensitive to flow fluctuations as their size increases, we observe the emergence of a slow dynamics corresponding to back-and-forth motions between two attractors, and a super-slow regime synchronized with flow reversals when they exist. Such dynamics is substantially reproduced by a one-dimensional stochastic model of an overdamped particle trapped in a two-well potential, forced by a colored noise. An extended model is also proposed that reproduces observed dynamics and trapping without potential barrier: the key ingredient is the ratio between the time scales of the noise correlation and the particle dynamics. A total agreement with experiments requires the introduction of spatially nonhomogeneous fluctuations and a suited confinement strength.

  1. Dynamic deformability of sickle red blood cells in microphysiological flow.

    PubMed

    Alapan, Y; Matsuyama, Y; Little, J A; Gurkan, U A

    2016-06-01

    In sickle cell disease (SCD), hemoglobin molecules polymerize intracellularly and lead to a cascade of events resulting in decreased deformability and increased adhesion of red blood cells (RBCs). Decreased deformability and increased adhesion of sickle RBCs lead to blood vessel occlusion (vaso-occlusion) in SCD patients. Here, we present a microfluidic approach integrated with a cell dimensioning algorithm to analyze dynamic deformability of adhered RBC at the single-cell level in controlled microphysiological flow. We measured and compared dynamic deformability and adhesion of healthy hemoglobin A (HbA) and homozygous sickle hemoglobin (HbS) containing RBCs in blood samples obtained from 24 subjects. We introduce a new parameter to assess deformability of RBCs: the dynamic deformability index (DDI), which is defined as the time-dependent change of the cell's aspect ratio in response to fluid flow shear stress. Our results show that DDI of HbS-containing RBCs were significantly lower compared to that of HbA-containing RBCs. Moreover, we observed subpopulations of HbS containing RBCs in terms of their dynamic deformability characteristics: deformable and non-deformable RBCs. Then, we tested blood samples from SCD patients and analyzed RBC adhesion and deformability at physiological and above physiological flow shear stresses. We observed significantly greater number of adhered non-deformable sickle RBCs than deformable sickle RBCs at flow shear stresses well above the physiological range, suggesting an interplay between dynamic deformability and increased adhesion of RBCs in vaso-occlusive events.

  2. Extensional channel flow revisited: a dynamical systems perspective

    NASA Astrophysics Data System (ADS)

    Marques, Francisco; Meseguer, Alvaro; Mellibovsky, Fernando; Weidman, Patrick D.

    2017-06-01

    Extensional self-similar flows in a channel are explored numerically for arbitrary stretching-shrinking rates of the confining parallel walls. The present analysis embraces time integrations, and continuations of steady and periodic solutions unfolded in the parameter space. Previous studies focused on the analysis of branches of steady solutions for particular stretching-shrinking rates, although recent studies focused also on the dynamical aspects of the problems. We have adopted a dynamical systems perspective, analysing the instabilities and bifurcations the base state undergoes when increasing the Reynolds number. It has been found that the base state becomes unstable for small Reynolds numbers, and a transitional region including complex dynamics takes place at intermediate Reynolds numbers, depending on the wall acceleration values. The base flow instabilities are constitutive parts of different codimension-two bifurcations that control the dynamics in parameter space. For large Reynolds numbers, the restriction to self-similarity results in simple flows with no realistic behaviour, but the flows obtained in the transition region can be a valuable tool for the understanding of the dynamics of realistic Navier-Stokes solutions.

  3. Stochastic dynamics of particles trapped in turbulent flows.

    PubMed

    Machicoane, N; López-Caballero, M; Fiabane, L; Pinton, J-F; Bourgoin, M; Burguete, J; Volk, R

    2016-02-01

    The long-time dynamics of large particles trapped in two nonhomogeneous turbulent shear flows is studied experimentally. Both flows present a common feature, a shear region that separates two colliding circulations, but with different spatial symmetries and temporal behaviors. Because large particles are less and less sensitive to flow fluctuations as their size increases, we observe the emergence of a slow dynamics corresponding to back-and-forth motions between two attractors, and a super-slow regime synchronized with flow reversals when they exist. Such dynamics is substantially reproduced by a one-dimensional stochastic model of an overdamped particle trapped in a two-well potential, forced by a colored noise. An extended model is also proposed that reproduces observed dynamics and trapping without potential barrier: the key ingredient is the ratio between the time scales of the noise correlation and the particle dynamics. A total agreement with experiments requires the introduction of spatially nonhomogeneous fluctuations and a suited confinement strength.

  4. Dynamics of blood flow in a microfluidic ladder network

    NASA Astrophysics Data System (ADS)

    Maddala, Jeevan; Zilberman-Rudenko, Jevgenia; McCarty, Owen

    The dynamics of a complex mixture of cells and proteins, such as blood, in perturbed shear flow remains ill-defined. Microfluidics is a promising technology for improving the understanding of blood flow under complex conditions of shear; as found in stent implants and in tortuous blood vessels. We model the fluid dynamics of blood flow in a microfluidic ladder network with dimensions mimicking venules. Interaction of blood cells was modeled using multiagent framework, where cells of different diameters were treated as spheres. This model served as the basis for predicting transition regions, collision pathways, re-circulation zones and residence times of cells dependent on their diameters and device architecture. Based on these insights from the model, we were able to predict the clot formation configurations at various locations in the device. These predictions were supported by the experiments using whole blood. To facilitate platelet aggregation, the devices were coated with fibrillar collagen and tissue factor. Blood was perfused through the microfluidic device for 9 min at a physiologically relevant venous shear rate of 600 s-1. Using fluorescent microscopy, we observed flow transitions near the channel intersections and at the areas of blood flow obstruction, which promoted larger thrombus formation. This study of integrating model predictions with experimental design, aids in defining the dynamics of blood flow in microvasculature and in development of novel biomedical devices.

  5. Chaotic dynamics of red blood cells in oscillating shear flow

    NASA Astrophysics Data System (ADS)

    Bagchi, Prosenjit; Cordasco, Daniel

    2015-11-01

    A 3D computational study of deformable red blood cells in dilute suspension and subject to sinusoidally oscillating shear flow is considered. It is observed that the cell exhibits either a periodic motion or a chaotic motion. In the periodic motion, the cell reverses its orientation either about the flow direction or about the flow gradient, depending on the initial conditions. In certain parameter range, the initial conditions are forgotten and the cells become entrained in the same sequence of horizontal reversals. The chaotic dynamics is characterized by a nonperiodic sequence of horizontal and vertical reversals, and swings. The study provides the first conclusive evidence of the chaotic dynamics of fully deformable cells in oscillating flow using a deterministic numerical model without the introduction of any stochastic noise. An analysis of the chaotic dynamics shows that chaos is only possible in certain frequency bands when the cell membrane can rotate by a certain amount allowing the cells to swing near the maximum shear rate. We make a novel observation that the occurrence of the vertical or horizontal reversal depends only on whether a critical angle, that is independent of the flow frequency, is exceeded at the instant of flow reversal.

  6. Study of Polyurethane Foaming Dynamics Using a Heat Flow Meter

    NASA Astrophysics Data System (ADS)

    Koniorczyk, P.; Trzyna, M.; Zmywaczyk, J.; Zygmunt, B.; Preiskorn, M.

    2017-05-01

    This work presents the results of the study concerning the effects of fillers addition on the heat flux density \\dot{q}( t ) of foaming of polyurethane-polystyrene porous composite (PSUR) and describes the dynamics of this process during the first 600 s. This foaming process resulted in obtaining porous materials that were based on HFC 365/225 blown rigid polyurethane foam (PUR) matrix, which contained thermoplastic expandable polystyrene (EPS) beads as the filler. In PSUR composites, the EPS beads were expanded after being heated to a temperature above the glass transition temperature of EPS and vaporing gas incorporated inside, by using the heat of exothermic reaction of polyol with isocyanate. From the start (t=0) to the end of the PSUR composite foaming process (t=tk), \\dot{q}( t ) was measured with the use of the heat flow meter. For the purpose of the study two PUR systems were selected: one with high and one with low heat density of foaming process q. EPS beads were selected from the same manufacturer with large and small diameter. The mass fraction of EPS in PSUR foam varied during the measurements. Additionally, a study of volume fractions of expanded EPS phase in PSUR foams as a function of mass fractions of EPS was conducted. In order to verify effects of the EPS addition on the heat flux density during PSUR foaming process, the thermal conductivity measurements were taken.

  7. Dynamics of generalized Gaussian polymeric structures in random layered flows.

    PubMed

    Katyal, Divya; Kant, Rama

    2015-04-01

    We develop a formalism for the dynamics of a flexible branched polymer with arbitrary topology in the presence of random flows. This is achieved by employing the generalized Gaussian structure (GGS) approach and the Matheron-de Marsily model for the random layered flow. The expression for the average square displacement (ASD) of the center of mass of the GGS is obtained in such flow. The averaging is done over both the thermal noise and the external random flow. Although the formalism is valid for branched polymers with various complex topologies, we mainly focus here on the dynamics of the flexible star and dendrimer. We analyze the effect of the topology (the number and length of branches for stars and the number of generations for dendrimers) on the dynamics under the influence of external flow, which is characterized by their root-mean-square velocity, persistence flow length, and flow exponent α. Our analysis shows two anomalous power-law regimes, viz., subdiffusive (intermediate-time polymer stretching and flow-induced diffusion) and superdiffusive (long-time flow-induced diffusion). The influence of the topology of the GGS is unraveled in the intermediate-time regime, while the long-time regime is only weakly dependent on the topology of the polymer. With the decrease in the value of α, the magnitude of the ASD decreases, while the temporal exponent of the ASD increases in both the time regimes. Also there is an increase in both the magnitude of the ASD and the crossover time (from the subdiffusive to the superdiffusive regime) with an increase in the total mass of the polymeric structure.

  8. Dynamics of generalized Gaussian polymeric structures in random layered flows

    NASA Astrophysics Data System (ADS)

    Katyal, Divya; Kant, Rama

    2015-04-01

    We develop a formalism for the dynamics of a flexible branched polymer with arbitrary topology in the presence of random flows. This is achieved by employing the generalized Gaussian structure (GGS) approach and the Matheron-de Marsily model for the random layered flow. The expression for the average square displacement (ASD) of the center of mass of the GGS is obtained in such flow. The averaging is done over both the thermal noise and the external random flow. Although the formalism is valid for branched polymers with various complex topologies, we mainly focus here on the dynamics of the flexible star and dendrimer. We analyze the effect of the topology (the number and length of branches for stars and the number of generations for dendrimers) on the dynamics under the influence of external flow, which is characterized by their root-mean-square velocity, persistence flow length, and flow exponent α . Our analysis shows two anomalous power-law regimes, viz., subdiffusive (intermediate-time polymer stretching and flow-induced diffusion) and superdiffusive (long-time flow-induced diffusion). The influence of the topology of the GGS is unraveled in the intermediate-time regime, while the long-time regime is only weakly dependent on the topology of the polymer. With the decrease in the value of α , the magnitude of the ASD decreases, while the temporal exponent of the ASD increases in both the time regimes. Also there is an increase in both the magnitude of the ASD and the crossover time (from the subdiffusive to the superdiffusive regime) with an increase in the total mass of the polymeric structure.

  9. Dynamics of a fluid flow on Mars: lava or mud?

    NASA Astrophysics Data System (ADS)

    Wilson, L.; Mouginis-Mark, P. J.

    2013-12-01

    We have identified an enigmatic flow in S.W. Cerberus Fossae, Mars. The flow originates from an almost circular pit within a remnant of a yardang at 0.58 degrees N, 155.28 degrees E, within the lower unit of the Medusae Fossae Formation. The flow is ~42 km long and 0.5 to 2.0 km wide. The surface textures of the resulting deposit show that the material flowed in such a way that the various deformation patterns on its surface were generally preserved as it moved, only being distorted or disrupted when the flow encountered major topographic obstacles or was forced to make rapid changes of direction. This observation of a stiff, generally undeformed surface layer overlying a relatively mobile base suggests that, while it was moving, the fluid material flowed in a laminar, and possibly non-Newtonian, fashion. The least-complicated non-Newtonian fluids are Bingham plastics. On this basis we use measurements of flow width, length, thickness and substrate slope obtained from images, a DEM constructed from stereo pairs of Context Camera (CTX) images, and Mars Orbiter Laser Altimeter (MOLA) altimetry points to deduce the rheological properties of the fluid, treating it as both a Newtonian and a Bingham material for comparison. The Newtonian option requires the fluid to have a viscosity close to 100 Pa s and to have flowed everywhere in a turbulent fashion. The Bingham option requires laminar flow, a plastic viscosity close to 1 Pa s, and a yield strength of ~185 Pa. We compare these parameters values with those of various environmental fluids on Earth in an attempt to narrow the range of possible materials forming the martian flow. A mafic to ultramafic lava would fit the Newtonian option but the required turbulence does not seem consistent with the surface textures. The Bingham option satisfies the morphological constraint of laminar motion if the material is a mud flow consisting of ~40% water and ~60% silt-sized silicate solids. Elsewhere on Mars, deposits with similar

  10. Unsteady fluid flow in smart material actuated fluid pumps

    NASA Astrophysics Data System (ADS)

    John, Shaju; Cadou, Christopher

    2005-05-01

    Smart materials' ability to deliver large block forces in a small package while operating at high frequencies makes them extremely attractive for converting electrical to mechanical power. This has led to the development of hybrid actuators consisting of co-located smart material actuated pumps and hydraulic cylinders that are connected by a set of fast-acting valves. The overall success of the hybrid concept hinges on the effectiveness of the coupling between the smart material and the fluid. This, in turn, is strongly dependent on the resistance to fluid flow in the device. This paper presents results from three-dimensional unsteady simulations of fluid flow in the pumping chamber of a prototype hybrid actuator powered by a piezo-electric stack. The results show that the forces associated with moving the fluid into and out of the pumping chamber already exceed 10% of the piezo stack blocked force at relatively low frequencies ~120 Hz and approach 40% of the blocked force at 800 Hz. This reduces the amplitude of the piston motion in such a way that the volume flow rate remains approximately constant above operating frequencies of 500 Hz while the efficiency of the pump decreases rapidly.

  11. Material flow-based economic assessment of landfill mining processes.

    PubMed

    Kieckhäfer, Karsten; Breitenstein, Anna; Spengler, Thomas S

    2017-02-01

    This paper provides an economic assessment of alternative processes for landfill mining compared to landfill aftercare with the goal of assisting landfill operators with the decision to choose between the two alternatives. A material flow-based assessment approach is developed and applied to a landfill in Germany. In addition to landfill aftercare, six alternative landfill mining processes are considered. These range from simple approaches where most of the material is incinerated or landfilled again to sophisticated technology combinations that allow for recovering highly differentiated products such as metals, plastics, glass, recycling sand, and gravel. For the alternatives, the net present value of all relevant cash flows associated with plant installation and operation, supply, recycling, and disposal of material flows, recovery of land and landfill airspace, as well as landfill closure and aftercare is computed with an extensive sensitivity analyses. The economic performance of landfill mining processes is found to be significantly influenced by the prices of thermal treatment (waste incineration as well as refuse-derived fuels incineration plant) and recovered land or airspace. The results indicate that the simple process alternatives have the highest economic potential, which contradicts the aim of recovering most of the resources. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. Modelling of Time-Variant Flows Using Vortex Dynamics.

    DTIC Science & Technology

    1987-02-01

    Like Euler methods, these methods are based on inviscid flow but they can be used in viscous-inviscid coupling schemes in combination with boundary layer...strategies between viscous solutions and vortex dynamics simu- lation is in progress. 5, R E F E R E N C E S [I) LEONHARD , A. Vortex Method for Flow...Simulation J. of Comp. Phys. 37,289-335 ( 1980 [2] LEONHARD , A. Computing Three-Dimensional Incompressible Flows with Vortex Elements Ann. Rev. Fluid Mech

  13. A mesoscopic simulation of material ---Advances in Dissipative particle dynamics research

    NASA Astrophysics Data System (ADS)

    Xue, Zhaolin

    2017-09-01

    A mesoscopic simulation of material --Dissipative particle dynamics(DPD), as the bond between macroscopic and microscopic simulation, had been increasingly draw attention in the research of soft matters, including the flowing condition and the morphological structure. The method of DPD simulation had been applied extensively in the fields of soft matters such as biomacromolecule and the flows of polymers since the DPD simulation has an advantage in time and space scale. In this article, the origin, the theoretical model and the development of dissipative particle dynamics are introduced at first. Subsequently, the advances in the simulation of complex fluids and polymers are reviewed. Finally, the future development and application are concluded.

  14. Dynamical weakening of pyroclastic flows by mechanical vibrations

    NASA Astrophysics Data System (ADS)

    Valverde, Jose Manuel; Soria-Hoyo, Carlos; Roche, Olivier

    2017-06-01

    Dynamical weakening of dense granular flows plays a critical role on diverse geological events such as seismic faulting and landslides. A common feature of these processes is the development of fluid-solid relative flows that could lead to fluidization by hydrodynamic viscous stresses. Volcanic ash landslides (pyroclastic flows) are characterized by their high mobility often attributed to fluidization of the usually fine and/or low-density particles by their interaction with the entrapped gas. However, the physical mechanism that might drive sustained fluidization of these dense granular flows over extraordinarily long runout distances is elusive. The behavior of volcanic ash in a slowly rotating drum subjected to mechanical vibrations shown in this work suggests that fluid-particle relative oscillations in dense granular flows present in volcanic eruption events can promote pore gas pressure at reduced shear rates as to sustain fluidization.

  15. Dynamics of intrinsic axial flows in unsheared, uniform magnetic fields

    SciTech Connect

    Li, J. C.; Diamond, P. H.; Xu, X. Q.; Tynan, G. R.

    2016-05-15

    A simple model for the generation and amplification of intrinsic axial flow in a linear device, controlled shear decorrelation experiment, is proposed. This model proposes and builds upon a novel dynamical symmetry breaking mechanism, using a simple theory of drift wave turbulence in the presence of axial flow shear. This mechanism does not require complex magnetic field structure, such as shear, and thus is also applicable to intrinsic rotation generation in tokamaks at weak or zero magnetic shear, as well as to linear devices. This mechanism is essentially the self-amplification of the mean axial flow profile, i.e., a modulational instability. Hence, the flow development is a form of negative viscosity phenomenon. Unlike conventional mechanisms where the residual stress produces an intrinsic torque, in this dynamical symmetry breaking scheme, the residual stress induces a negative increment to the ambient turbulent viscosity. The axial flow shear is then amplified by this negative viscosity increment. The resulting mean axial flow profile is calculated and discussed by analogy with the problem of turbulent pipe flow. For tokamaks, the negative viscosity is not needed to generate intrinsic rotation. However, toroidal rotation profile gradient is enhanced by the negative increment in turbulent viscosity.

  16. Dynamics of intrinsic axial flows in unsheared, uniform magnetic fields

    NASA Astrophysics Data System (ADS)

    Li, J. C.; Diamond, P. H.; Xu, X. Q.; Tynan, G. R.

    2016-05-01

    A simple model for the generation and amplification of intrinsic axial flow in a linear device, controlled shear decorrelation experiment, is proposed. This model proposes and builds upon a novel dynamical symmetry breaking mechanism, using a simple theory of drift wave turbulence in the presence of axial flow shear. This mechanism does not require complex magnetic field structure, such as shear, and thus is also applicable to intrinsic rotation generation in tokamaks at weak or zero magnetic shear, as well as to linear devices. This mechanism is essentially the self-amplification of the mean axial flow profile, i.e., a modulational instability. Hence, the flow development is a form of negative viscosity phenomenon. Unlike conventional mechanisms where the residual stress produces an intrinsic torque, in this dynamical symmetry breaking scheme, the residual stress induces a negative increment to the ambient turbulent viscosity. The axial flow shear is then amplified by this negative viscosity increment. The resulting mean axial flow profile is calculated and discussed by analogy with the problem of turbulent pipe flow. For tokamaks, the negative viscosity is not needed to generate intrinsic rotation. However, toroidal rotation profile gradient is enhanced by the negative increment in turbulent viscosity.

  17. Sediment dynamics in an overland flow-prone forest catchment

    NASA Astrophysics Data System (ADS)

    Zimmermann, Alexander; Elsenbeer, Helmut

    2010-05-01

    Vegetation controls erosion in many respects, and it is assumed that forest cover is an effective control. Currently, most literature on erosion processes in forest ecosystems support this impression and estimates of sediment export from forested catchments serve as benchmarks to evaluate erosion processes under different land uses. Where soil properties favor near-surface flow paths, however, vegetation may not mitigate surface erosion. In the forested portion of the Panama Canal watershed overland flow is widespread and occurs frequently, and indications of active sediment transport are hard to overlook. In this area we selected a 9.7 ha catchment for a high-resolution study of suspended sediment dynamics. We equipped five nested catchments to elucidate sources, drivers, magnitude and timing of suspended sediment export by continuous monitoring of overland flow and stream flow and by simultaneous, event-based sediment sampling. The support program included monitoring throughfall, splash erosion, overland-flow connectivity and a survey of infiltrability, permeability, and aggregate stability. This dataset allowed a comprehensive view on erosion processes. We found that overland flow controls the suspended-sediment dynamics in channels. Particularly, rainfalls of high intensity at the end of the rainy season have a superior impact on the overall sediment export. During these events, overland flow occurs catchment-wide up to the divide and so does erosion. With our contribution we seek to provide evidence that forest cover and large sediment yields are no contradiction in terms even in the absence of mass movements.

  18. Modeling of the Bosphorus exchange flow dynamics

    NASA Astrophysics Data System (ADS)

    Sözer, Adil; Özsoy, Emin

    2017-04-01

    The fundamental hydrodynamic behavior of the Bosphorus Strait is investigated through a numerical modeling study using alternative configurations of idealized or realistic geometry. Strait geometry and basin stratification conditions allow for hydraulic controls and are ideally suited to support the maximal-exchange regime, which determines the rate of exchange of waters originating from the adjacent Black and Mediterranean Seas for a given net transport. Steady-state hydraulic controls are demonstrated by densimetric Froude number calculations under layered flow approximations when corrections are applied to account for high velocity shears typically observed in the Bosphorus. Analyses of the model results reveal many observed features of the strait, including critical transitions at hydraulic controls and dissipation by turbulence and hydraulic jumps. It is found that the solution depends on initialization, especially with respect to the basin initial conditions. Significant differences between the controlled maximal-exchange and drowned solutions suggest that a detailed modeling implementation involving coupling with adjacent basins needs to take full account of the Bosphorus Strait in terms of the physical processes to be resolved.

  19. Modeling of the Bosphorus exchange flow dynamics

    NASA Astrophysics Data System (ADS)

    Sözer, Adil; Özsoy, Emin

    2017-01-01

    The fundamental hydrodynamic behavior of the Bosphorus Strait is investigated through a numerical modeling study using alternative configurations of idealized or realistic geometry. Strait geometry and basin stratification conditions allow for hydraulic controls and are ideally suited to support the maximal-exchange regime, which determines the rate of exchange of waters originating from the adjacent Black and Mediterranean Seas for a given net transport. Steady-state hydraulic controls are demonstrated by densimetric Froude number calculations under layered flow approximations when corrections are applied to account for high velocity shears typically observed in the Bosphorus. Analyses of the model results reveal many observed features of the strait, including critical transitions at hydraulic controls and dissipation by turbulence and hydraulic jumps. It is found that the solution depends on initialization, especially with respect to the basin initial conditions. Significant differences between the controlled maximal-exchange and drowned solutions suggest that a detailed modeling implementation involving coupling with adjacent basins needs to take full account of the Bosphorus Strait in terms of the physical processes to be resolved.

  20. Improving flow distribution in influent channels using computational fluid dynamics.

    PubMed

    Park, No-Suk; Yoon, Sukmin; Jeong, Woochang; Lee, Seungjae

    2016-10-01

    Although the flow distribution in an influent channel where the inflow is split into each treatment process in a wastewater treatment plant greatly affects the efficiency of the process, and a weir is the typical structure for the flow distribution, to the authors' knowledge, there is a paucity of research on the flow distribution in an open channel with a weir. In this study, the influent channel of a real-scale wastewater treatment plant was used, installing a suppressed rectangular weir that has a horizontal crest to cross the full channel width. The flow distribution in the influent channel was analyzed using a validated computational fluid dynamics model to investigate (1) the comparison of single-phase and two-phase simulation, (2) the improved procedure of the prototype channel, and (3) the effect of the inflow rate on flow distribution. The results show that two-phase simulation is more reliable due to the description of the free-surface fluctuations. It should first be considered for improving flow distribution to prevent a short-circuit flow, and the difference in the kinetic energy with the inflow rate makes flow distribution trends different. The authors believe that this case study is helpful for improving flow distribution in an influent channel.

  1. Study of melt flow dynamics and influence on quality for CO2 laser fusion cutting

    NASA Astrophysics Data System (ADS)

    Riveiro, A.; Quintero, F.; Lusquiños, F.; Comesaña, R.; Pou, J.

    2011-04-01

    The understanding of melt flow dynamics during fusion laser cutting is still a topic of great importance because this determines the quality characteristics of the processed workpiece. Despite the complexity of the experimental study of the physical processes involved in this technique, fusion laser cutting can be visualized during the processing of glass because this material absorbs the laser radiation provided by a CO2 laser but shows transparency to visible radiation. Then, we present in this work the results of the study of the melt flow dynamics during laser cutting of glass. Under different experimental conditions, the dynamics of the cutting front and its complete geometry (front wall inclination), and the evolution of the melt along the cut edge were analysed using a high-speed video camera to study the process. A phenomenon concerning the plasma plume formed during the process was observed, which has not been previously reported in the literature. This can displace the normal shock wave (MSD) commonly formed in the inlet kerf and can affect the assist gas flow into the kerf. On the other hand, the analysis of the recorded images allowed the determination of not only the amount of molten material along the cut edge but also the direction and velocity of the melt. Relevant processing parameters affecting the flow of molten material were assessed. These results were used as a basis to explain the different processes involved in the generation of dross, a typical imperfection appearing in laser cutting.

  2. Material flow analysis of used personal computers in Japan.

    PubMed

    Yoshida, Aya; Tasaki, Tomohiro; Terazono, Atsushi

    2009-05-01

    Most personal computers (PCs) are discarded by consumers after the data files have been moved to a new PC. Therefore, a used PC collection scheme should be created that does not depend on the distribution route of new PCs. In Japan, manufacturers' voluntary take-back recycling schemes were established in 2001 (for business PCs) and 2003 (for household PCs). At the same time, the export of used PCs from Japan increased, affecting the domestic PC reuse market. These regulatory and economic conditions would have changed the flow of used PCs. In this paper, we developed a method of minimizing the errors in estimating the material flow of used PCs. The method's features include utilization of both input and output flow data and elimination of subjective estimation as much as possible. Flow rate data from existing surveys were used for estimating the flow of used PCs in Japan for fiscal years (FY) 2000, 2001, and 2004. The results show that 3.92 million and 4.88 million used PCs were discarded in FY 2000 and 2001, respectively. Approximately two-thirds of the discarded PCs were disposed of or recycled within the country, one-fourth was reused within the country, and 8% were exported. In FY 2004, 7.47 million used PCs were discarded. The ratio of domestic disposal and recycling decreased to 37% in FY 2004, whereas the domestic reuse and export ratios increased to 37% and 26%, respectively. Flows from businesses to retailers in FY 2004 increased dramatically, which led to increased domestic reuse. An increase in the flow of used PCs from lease and rental companies to secondhand shops has led to increased exports. Results of interviews with members of PC reuse companies were and trade statistics were used to verify the results of our estimation of domestic reuse and export of used PCs.

  3. Experimental characterization of energetic material dynamics for multiphase blast simulation.

    SciTech Connect

    Beresh, Steven Jay; Wagner, Justin L.; Kearney, Sean Patrick; Wright, Elton K.; Baer, Melvin R.; Pruett, Brian Owen Matthew

    2011-09-01

    Currently there is a substantial lack of data for interactions of shock waves with particle fields having volume fractions residing between the dilute and granular regimes, which creates one of the largest sources of uncertainty in the simulation of energetic material detonation. To close this gap, a novel Multiphase Shock Tube has been constructed to drive a planar shock wave into a dense gas-solid field of particles. A nearly spatially isotropic field of particles is generated in the test section by a gravity-fed method that results in a spanwise curtain of spherical 100-micron particles having a volume fraction of about 19%. Interactions with incident shock Mach numbers of 1.66, 1.92, and 2.02 were achieved. High-speed schlieren imaging simultaneous with high-frequency wall pressure measurements are used to reveal the complex wave structure associated with the interaction. Following incident shock impingement, transmitted and reflected shocks are observed, which lead to differences in particle drag across the streamwise dimension of the curtain. Shortly thereafter, the particle field begins to propagate downstream and spread. For all three Mach numbers tested, the energy and momentum fluxes in the induced flow far downstream are reduced about 30-40% by the presence of the particle field. X-Ray diagnostics have been developed to penetrate the opacity of the flow, revealing the concentrations throughout the particle field as it expands and spreads downstream with time. Furthermore, an X-Ray particle tracking velocimetry diagnostic has been demonstrated to be feasible for this flow, which can be used to follow the trajectory of tracer particles seeded into the curtain. Additional experiments on single spherical particles accelerated behind an incident shock wave have shown that elevated particle drag coefficients can be attributed to increased compressibility rather than flow unsteadiness, clarifying confusing results from the historical database of shock tube

  4. Design considerations for pulsed-flow comprehensive two-dimensional GC: dynamic flow model approach.

    PubMed

    Harvey, Paul McA; Shellie, Robert A; Haddad, Paul R

    2010-04-01

    A dynamic flow model, which maps carrier gas pressures and carrier gas flow rates through the first dimension separation column, the modulator sample loop, and the second dimension separation column(s) in a pulsed-flow modulation comprehensive two-dimensional gas chromatography (PFM-GCxGC) system is described. The dynamic flow model assists design of a PFM-GCxGC modulator and leads to rapid determination of pneumatic conditions, timing parameters, and the dimensions of the separation columns and connecting tubing used to construct the PFM-GCxGC system. Three significant innovations are introduced in this manuscript, which were all uncovered by using the dynamic flow model. A symmetric flow path modulator improves baseline stability, appropriate selection of the flow restrictors in the first dimension column assembly provides a generally more stable and robust system, and these restrictors increase the modulation period flexibility of the PFM-GCxGC system. The flexibility of a PFM-GCxGC system resulting from these innovations is illustrated using the same modulation interface to analyze Special Antarctic Blend (SAB) diesel using 3 s and 9 s modulation periods.

  5. Incompressible material point method for free surface flow

    NASA Astrophysics Data System (ADS)

    Zhang, Fan; Zhang, Xiong; Sze, Kam Yim; Lian, Yanping; Liu, Yan

    2017-02-01

    To overcome the shortcomings of the weakly compressible material point method (WCMPM) for modeling the free surface flow problems, an incompressible material point method (iMPM) is proposed based on operator splitting technique which splits the solution of momentum equation into two steps. An intermediate velocity field is first obtained by solving the momentum equations ignoring the pressure gradient term, and then the intermediate velocity field is corrected by the pressure term to obtain a divergence-free velocity field. A level set function which represents the signed distance to free surface is used to track the free surface and apply the pressure boundary conditions. Moreover, an hourglass damping is introduced to suppress the spurious velocity modes which are caused by the discretization of the cell center velocity divergence from the grid vertexes velocities when solving pressure Poisson equations. Numerical examples including dam break, oscillation of a cubic liquid drop and a droplet impact into deep pool show that the proposed incompressible material point method is much more accurate and efficient than the weakly compressible material point method in solving free surface flow problems.

  6. Nonlinear Dynamics of a Microswimmer in Poiseuille Flow

    NASA Astrophysics Data System (ADS)

    Zöttl, Andreas; Stark, Holger

    2012-05-01

    We study the three-dimensional dynamics of a spherical microswimmer in cylindrical Poiseuille flow which can be mapped onto a Hamiltonian system. Swinging and tumbling trajectories are identified. In 2D they are equivalent to oscillating and circling solutions of a mathematical pendulum. Hydrodynamic interactions between the swimmer and confining channel walls lead to dissipative dynamics and result in stable trajectories, different for pullers and pushers. We demonstrate this behavior in the dipole approximation of the swimmer and with simulations using the method of multiparticle collision dynamics.

  7. Nonlinear dynamics of a microswimmer in Poiseuille flow.

    PubMed

    Zöttl, Andreas; Stark, Holger

    2012-05-25

    We study the three-dimensional dynamics of a spherical microswimmer in cylindrical Poiseuille flow which can be mapped onto a Hamiltonian system. Swinging and tumbling trajectories are identified. In 2D they are equivalent to oscillating and circling solutions of a mathematical pendulum. Hydrodynamic interactions between the swimmer and confining channel walls lead to dissipative dynamics and result in stable trajectories, different for pullers and pushers. We demonstrate this behavior in the dipole approximation of the swimmer and with simulations using the method of multiparticle collision dynamics.

  8. Dynamic characterization of permeabilities and flows in microchannels.

    PubMed

    Castro, M; Bravo-Gutiérrez, M E; Hernández-Machado, A; Poiré, E Corvera

    2008-11-28

    We make an analytical study of the nonsteady flow of Newtonian fluids in microchannels. We consider the slip boundary condition at the solid walls with Navier hypothesis and calculate the dynamic permeability, which gives the system's response to dynamic pressure gradients. We find a scaling relation in the absence of slip that is broken in its presence. We discuss how this might be useful to experimentally determine--by means of microparticle image velocimetry technology--whether slip exists or not in a system, the value of the slip length, and the validity of Navier hypothesis in dynamic situations.

  9. Intraoperative Analysis of Flow Dynamics in Arteriovenous Composite Y Grafts

    PubMed Central

    Lobo Filho, Heraldo Guedis; Lobo Filho, José Glauco; Pimentel, Matheus Duarte; Silva, Bruno Gadelha Bezerra; de Souza, Camylla Santos; Montenegro, Marília Leitão; Leitão, Maria Cláudia de Azevedo; Jamacuru, Francisco Vagnaldo Fechine

    2016-01-01

    Objective Composite graft of left internal thoracic artery and great saphenous vein in revascularization of the left coronary system is a technique well described in literature. The aim of this study is to analyze blood flow dynamics in this configuration of composite graft especially in what concerns left internal thoracic artery's adaptability and influence of great saphenous vein segment on left internal thoracic artery's flow. Methods Revascularization of left coronary system with composite graft, with left internal thoracic artery revascularizing the anterior interventricular artery and a great saphenous vein segment, anastomosed to the left internal thoracic artery, revascularizing another branch of the left coronary system, was performed in 23 patients. Blood flow was evaluated by transit time flowmetry in all segments of the composite graft (left internal thoracic artery proximal segment, left internal thoracic artery distal segment and great saphenous vein segment). Measures were performed in baseline condition and after dobutamine-induced stress, without and with non-traumatic temporary clamping of the distal segments of the composite graft. Results Pharmacological stress resulted in increase of blood flow values in the analyzed segments (P<0.05). Non-traumatic temporary clamping of great saphenous vein segment did not result in statistically significant changes in the flow of left internal thoracic artery distal segment, both in baseline condition and under pharmacological stress. Similarly, non-traumatic temporary clamping of left internal thoracic artery distal segment did not result in statistically significant changes in great saphenous vein segment flow. Conclusion Composite grafts with left internal thoracic artery and great saphenous vein for revascularization of left coronary system, resulted in blood flow dynamics with physiological adaptability, both at rest and after pharmacological stress, according to demand. Presence of great saphenous vein

  10. Polymer-based micro flow sensor for dynamical flow measurements in hydraulic systems

    NASA Astrophysics Data System (ADS)

    Ahrens, R.; Festa, M.

    2010-06-01

    In this paper we present a micro flow sensor from a polymer for dynamical flow measurements in hydraulic systems. The flow sensor is based on the thermal anemometric principle and consists of two micro-structured housing shells from polysulfone (PSU) which form a small fluidic channel with a cross-section of 580 µm × 400 µm. In between there is a thin polyimide membrane supporting three gold track structures forming an electrical heater and two resistive thermometers which allows the detection of the flow direction, too. The complete sensor is inserted into the hydraulic system, but only a small bypass flow is directed through the fluidic channel by means of a special splitting system. Due to its small heat capacity, the sensor is suitable to detect flow pulsations up to about 1200 Hz which allows the sensor to be used for the condition monitoring or preventive maintenance of hydraulic systems.

  11. Can the flow dynamics of debris flows be identified from seismic data?

    NASA Astrophysics Data System (ADS)

    Kean, J. W.; Coe, J. A.; Smith, J. B.; Coviello, V.; McCoy, S. W.

    2014-12-01

    There is growing interest in the use of seismic and acoustic data to interpret a variety of geomorphic processes including landslides and debris flows. This measurement technique is attractive because a broad area can be monitored from a safe distance, unlike more direct methods of instrumentation, which are restricted to known flow paths and are vulnerable to damage by the flow. Previous work has shown that measurements of ground vibrations are capable of detecting the timing, speed, and location of landslides and debris flows. A remaining question is whether or not additional flow properties, such as basal stress, impact force, or flow magnitude can be inferred reliably from seismic data. This question has been difficult to answer, because detailed, independent measurements of flow dynamics are lacking. Here, we explore characteristics of debris-flow induced ground vibrations using new data from the Chalk Cliffs monitoring site in central Colorado. Monitoring included a heavily instrumented cross-section consisting of two tri-axial geophones to record ground vibrations (at 333 Hz), a small, 225 cm2 force plate to record basal impact forces (at 333 Hz), a laser distance meter to record flow stage over the plate (at 10 Hz), and a high definition camera to record flow dynamics (at 24 Hz). One geophone (A) was mounted on a boulder partially buried in colluvium; the other (B) was mounted directly to weathered bedrock typical of the site. This combination of instrumentation allowed us to compare the spectral response of different geophone installations to independently measured flow depth and basal impact force. We also compared the response of the geophones to surges that flowed over a sediment-covered bed (40-cm thick) to surges that flowed over a bare bedrock channel. Preliminary results showed that site conditions have a large effect on recorded debris-flow vibrations. The seismic signature of debris flow was very different between the geophones, with geophone B

  12. Material handling robot system for flow-through storage applications

    NASA Astrophysics Data System (ADS)

    Dill, James F.; Candiloro, Brian; Downer, James; Wiesman, Richard; Fallin, Larry; Smith, Ron

    1999-01-01

    This paper describes the design, development and planned implementation of a system of mobile robots for use in flow through storage applications. The robots are being designed with on-board embedded controls so that they can perform their tasks as semi-autonomous workers distributed within a centrally controlled network. On the storage input side, boxes will be identified by bar-codes and placed into preassigned flow through bins. On the shipping side, orders will be forwarded to the robots from a central order processing station and boxes will be picked from designated storage bins following proper sequencing to permit direct loading into trucks for shipping. Because of the need to maintain high system availability, a distributed control strategy has been selected. When completed, the system will permit robots to be dynamically reassigned responsibilities if an individual unit fails. On-board health diagnostics and condition monitoring will be used to maintain high reliability of the units.

  13. Bubbly flow model for the dynamic characteristics of cavitating pumps

    NASA Technical Reports Server (NTRS)

    Brennen, C.

    1978-01-01

    The recent experimental transfer matrices obtained by Ng and Brennen (1978) for some axial flow pumps revealed some dynamic characteristics which were unaccounted for by any existing theoretical analysis; their visual observations suggested that the bubbly cavitating flow in the blade passages could be responsible for these effects. A theoretical model of the dynamic response of this bubbly blade-passage flow is described in the present paper. Void-fraction fluctuations in this flow result not only from pressure fluctuations but also because the fluctuating angle of attack causes fluctuations in the rate of production of bubbles near the leading edge. The latter causes kinematic waves which interact through the boundary conditions with the dynamic waves caused by pressure fluctuation. The resulting theoretical transfer functions which results are in good qualitative agreement with the experiments; with appropriate choices of two parameters good quantitative agreement is also obtained. The theoretical model also provides one possible explanation of the observation that the pump changes from an essentially passive dynamic element in the absence of cavitation to a progressively more active element as the extent of cavitation increases.

  14. Particle hopping vs. fluid-dynamical models for traffic flow

    SciTech Connect

    Nagel, K.

    1995-12-31

    Although particle hopping models have been introduced into traffic science in the 19509, their systematic use has only started recently. Two reasons for this are, that they are advantageous on modem computers, and that recent theoretical developments allow analytical understanding of their properties and therefore more confidence for their use. In principle, particle hopping models fit between microscopic models for driving and fluiddynamical models for traffic flow. In this sense, they also help closing the conceptual gap between these two. This paper shows connections between particle hopping models and traffic flow theory. It shows that the hydrodynamical limits of certain particle hopping models correspond to the Lighthill-Whitham theory for traffic flow, and that only slightly more complex particle hopping models produce already the correct traffic jam dynamics, consistent with recent fluid-dynamical models for traffic flow. By doing so, this paper establishes that, on the macroscopic level, particle hopping models are at least as good as fluid-dynamical models. Yet, particle hopping models have at least two advantages over fluid-dynamical models: they straightforwardly allow microscopic simulations, and they include stochasticity.

  15. Bubbly flow model for the dynamic characteristics of cavitating pumps

    NASA Technical Reports Server (NTRS)

    Brennen, C.

    1978-01-01

    The recent experimental transfer matrices obtained by Ng and Brennen (1978) for some axial flow pumps revealed some dynamic characteristics which were unaccounted for by any existing theoretical analysis; their visual observations suggested that the bubbly cavitating flow in the blade passages could be responsible for these effects. A theoretical model of the dynamic response of this bubbly blade-passage flow is described in the present paper. Void-fraction fluctuations in this flow result not only from pressure fluctuations but also because the fluctuating angle of attack causes fluctuations in the rate of production of bubbles near the leading edge. The latter causes kinematic waves which interact through the boundary conditions with the dynamic waves caused by pressure fluctuation. The resulting theoretical transfer functions which results are in good qualitative agreement with the experiments; with appropriate choices of two parameters good quantitative agreement is also obtained. The theoretical model also provides one possible explanation of the observation that the pump changes from an essentially passive dynamic element in the absence of cavitation to a progressively more active element as the extent of cavitation increases.

  16. Translanguaging as Dynamic Activity Flows in CLIL Classrooms

    ERIC Educational Resources Information Center

    Lin, Angel M. Y.; He, Peichang

    2017-01-01

    In this article, the role of translanguaging in facilitating content and language integrated learning (CLIL) is examined in connection with the notion of academic language across the curriculum in multilingual contexts. Ethnographic naturalistic observations and interviews were conducted to analyse translanguaging in the dynamic flow of…

  17. Simulation, modeling and dynamical analysis of multibody flows

    NASA Astrophysics Data System (ADS)

    Blackmore, Denis; Rosato, Anthony; Sen, Surajit; Wu, Hao

    2017-04-01

    Recent particulate flow research using a discrete element simulation-dynamical systems approach is described. The simulation code used is very efficient and the mathematical model is an integro-partial differential equation. Examples are presented to show the effectiveness of the approach.

  18. Dynamic Young's moduli of space materials at low temperatures

    NASA Astrophysics Data System (ADS)

    Zhang, Z.; Zhao, L. Z.; Tu, Z. H.; Zhang, P. Q.

    Using vibration analysis methods, the dynamic mechanical properties of space materials at low temperatures (from 4.2 to 300 K) are studied in this paper. System identification techniques in the time domain are used to identify the dynamic parameters of the space materials Ti-5Al-2.5Sn extra-low-interstitial (ELI) alloy and Al-2.5Li-1.3Cu-0.9Mg-0.13Zr (Al-Li) alloy. The dynamic Young's moduli of these materials are calculated using the basic natural frequencies at different temperatures.

  19. Dynamic Mode Decomposition of Flow Around Interacting Barchan Dunes

    NASA Astrophysics Data System (ADS)

    Bristow, Nathaniel; Blois, Gianluca; Kim, Taehoon; Schmid, Peter; Best, Jim; Christensen, Kenneth

    2015-11-01

    Barchan dunes are crescentic bedforms located in environments with unidirectional flow and limited sediment supply, including deserts, river beds and the craters of Mars. The evolution of, and interactions between, barchans are highly dynamic, involving feedback mechanisms between the fluid flow, morphological change and sediment transport. A series of experiments were undertaken to discretely simulate the collision of a smaller barchan with a larger, downstream one using fixed bedform models, each experiment representing a successive snapshot in the dune collision process. These experiments thus capture the turbulent flow over fixed-bed morphologies that correlate with rapid morphological change and high rates of sediment transport using time-resolved PIV in the wall-parallel plane. The use of a Refractive Index Matching (RIM) flow facility allows for the light to pass through the model, capturing areas which are otherwise obscured, such as around the horns of the dune and the sheltered region behind the crest. Dynamic Mode Decomposition is used to identify the most dominant modes contributing to flow dynamics in each collision stage.

  20. Molecular dynamics study of tethered polymers in shear flow.

    PubMed

    Gratton, Y; Slater, G W

    2005-08-01

    Single macromolecules can now be isolated and characterized experimentally using techniques such as optical tweezers and videomicroscopy. An interesting and important single-molecule problem is that of the dynamics of a polymer chain tethered to a solid surface and subjected to a shear flow. An experimental study of such a system was reported by Doyle et al. (Phys. Rev. Lett. 84, 4769 (2000)), and their results showed a surprising recirculating motion of the DNA chain. We explore this problem using molecular dynamics computer simulations with explicit hydrodynamic interactions. The dynamical properties of a Freely Jointed Chain (FJC) with Finitely Extensible Nonlinear Elastic (FENE) links are examined in similar conditions (i.e., confined between two surfaces and in the presence of a Poiseuille flow). We see the remarkable cyclic polymer motion observed experimentally, and we show that a simple cross-correlation function can be used to measure the corresponding period of motion. We also propose a new empirical equation relating the magnitude of the shear flow to the amount of chain deformation, an equation that appears to apply for both weak and strong flows. Finally, we report on packing effects near the molecularly flat wall, an associated chain-sticking phenomenon, and the impact of the chain hydrodynamic drag on the local fluid flow.

  1. Macro material flow modeling for analyzing solid waste management options

    SciTech Connect

    Holter, G.M.; Pennock, K.A.; Shaver, S.R.

    1993-06-01

    A Macro Material Flow Modeling (MMFM) concept and approach are being adopted to develop a predictive modeling capability. This capability is intended to provide part of the basis for evaluating potential impacts from various solid waste management system configurations and operating scenarios, as well as evaluating the impacts of various policies on solid waste quantities and compositions. The MMFM capability, as part of a broader Solid Waste Initiative at Pacific Northwest Laboratory, is intended to provide an increased understanding of solid waste as a disposal, energy, and resource problem on a national and global scale, particularly over the long term. This model is a macro-level simulation of the flows of the various materials through the solid waste management system, and also through the associated materials production and use system. Inclusion of materials production and use within the modeling context allows a systems approach to be used, providing a much more complete understanding of the origins of the solid waste materials and also of possible options for materials recovery and reuse than if a more traditional ``end-of-pipe`` view of solid waste is adopted. The MMFM is expected to be useful in evaluating longer-term, broader-ranging solid waste impacts than are traditionally evaluated by decision-makers involved in implementing solutions to local or regional solid waste management problems. This paper discusses the types of questions of interest in evaluating long-term, broad-range impacts from solid waste. It then identifies the basic needs for predictive modeling capabilities like the MMFM, and provides a basic description of the conceptual framework for the model and the associated data. Status of the MMFM implementation is also discussed.

  2. Macro material flow modeling for analyzing solid waste management options

    SciTech Connect

    Holter, G.M.; Pennock, K.A.; Shaver, S.R.

    1993-06-01

    A Macro Material Flow Modeling (MMFM) concept and approach are being adopted to develop a predictive modeling capability. This capability is intended to provide part of the basis for evaluating potential impacts from various solid waste management system configurations and operating scenarios, as well as evaluating the impacts of various policies on solid waste quantities and compositions. The MMFM capability, as part of a broader Solid Waste Initiative at Pacific Northwest Laboratory, is intended to provide an increased understanding of solid waste as a disposal, energy, and resource problem on a national and global scale, particularly over the long term. This model is a macro-level simulation of the flows of the various materials through the solid waste management system, and also through the associated materials production and use system. Inclusion of materials production and use within the modeling context allows a systems approach to be used, providing a much more complete understanding of the origins of the solid waste materials and also of possible options for materials recovery and reuse than if a more traditional end-of-pipe'' view of solid waste is adopted. The MMFM is expected to be useful in evaluating longer-term, broader-ranging solid waste impacts than are traditionally evaluated by decision-makers involved in implementing solutions to local or regional solid waste management problems. This paper discusses the types of questions of interest in evaluating long-term, broad-range impacts from solid waste. It then identifies the basic needs for predictive modeling capabilities like the MMFM, and provides a basic description of the conceptual framework for the model and the associated data. Status of the MMFM implementation is also discussed.

  3. Lobe dynamics and homoclinic tangles in atmospheric flows

    NASA Astrophysics Data System (ADS)

    Naik, S.; Ross, S. D.

    2012-12-01

    In recent years, dynamical system theorists have been developing methods to study structures that govern the dynamics of atmospheric and oceanic flows. The primary concern for these flows are the finite time nature and the arbitrary time dependence in contrast to classical dynamical systems. Recent work on 2D quasi-horizontal approximations of atmospheric motion have demonstrated that there are aperiodic, finite-time analogs of homoclinic tangles and lobe dynamics, e.g., around hurricane boundaries. The tools used have been coherent structure boundaries based on ridges of the finite-time Lyapunov exponent (FTLE) field calculated from integrated particle trajectories. There are some ambiguities in the FTLE-based approach which suggests other methods should be attempted. In this work, we apply methods based on Lagrangian descriptors (due to Mancho and co-workers) to locate distinguished hyperbolic trajectories (DHTs) and generate corresponding finite-time stable and unstable manifolds to study lobe dynamics, as applied to atmospheric flow as well as fluid experiments. We compare the Lagrangian descriptor approach with the FTLE-based approach.

  4. Granular crystals: Nonlinear dynamics meets materials engineering

    DOE PAGES

    Porter, Mason A.; Kevrekidis, Panayotis G.; Daraio, Chiara

    2015-11-01

    In this article, the freedom to choose the size, stiffness, and spatial distribution of macroscopic particles in a lattice makes granular crystals easily tailored building blocks for shock-absorbing materials, sound-focusing devices, acoustic switches, and other exotica.

  5. Flow dynamics of bank-attached instream structures

    NASA Astrophysics Data System (ADS)

    Kang, Seokkoo

    2016-04-01

    Numerical simulations and experiments for flow past a bank-attached vane, a widely-used instream structure for stream restoration, are carried out to study the turbulent flow dynamics occurring around the structure. In the numerical simulation, the details of the natural rocks that constitute the vane are directly resolved by employing the recently developed computational fluid dynamics model of Kang et al. (2011). The time-averaged flowfield is shown to be in good agreement with the results of laboratory measurements. Analysis of the simulated flow shows that there exist two counter-rotating secondary flows cells downstream of the vane, one of which is located near the center of the channel and the other is located near the corner between the channel bed and the sidewall to which the vane is attached. The formation of the two counter-rotating secondary flow cells is shown to be linked to the plunging of the mean three-dimensional streamlines originating upstream of the vane onto a point downstream of the vane positioned on the lower part of the sidewall. The laboratory experiment also reveals the existence of such flow structures.

  6. Material flow data for numerical simulation of powder injection molding

    NASA Astrophysics Data System (ADS)

    Duretek, I.; Holzer, C.

    2017-01-01

    The powder injection molding (PIM) process is a cost efficient and important net-shape manufacturing process that is not completely understood. For the application of simulation programs for the powder injection molding process, apart from suitable physical models, exact material data and in particular knowledge of the flow behavior are essential in order to get precise numerical results. The flow processes of highly filled polymers are complex. Occurring effects are very hard to separate, like shear flow with yield stress, wall slip, elastic effects, etc. Furthermore, the occurrence of phase separation due to the multi-phase composition of compounds is quite probable. In this work, the flow behavior of a 316L stainless steel feedstock for powder injection molding was investigated. Additionally, the influence of pre-shearing on the flow behavior of PIM-feedstocks under practical conditions was examined and evaluated by a special PIM injection molding machine rheometer. In order to have a better understanding of key factors of PIM during the injection step, 3D non-isothermal numerical simulations were conducted with a commercial injection molding simulation software using experimental feedstock properties. The simulation results were compared with the experimental results. The mold filling studies amply illustrate the effect of mold temperature on the filling behavior during the mold filling stage. Moreover, the rheological measurements showed that at low shear rates no zero shear viscosity was observed, but instead the viscosity further increased strongly. This flow behavior could be described with the Cross-WLF approach with Herschel-Bulkley extension very well.

  7. Thermal/chemical stability of ceramic cross flow filter materials

    SciTech Connect

    Alvin, M.A.; Bahovchin, D.M.; Lippert, T.E.; Tressler, R.E.; McNerney, K.B.

    1992-01-01

    Westinghouse has undertaken a two phase program to determine possible long-term, high temperature influence that advanced coal-based power system environments may have on the stability of the ceramic cross flow filter elements. During the past year, we have principally focused our efforts on developing an understanding of the stability of the alumina/mullite filter material at high temperature (i.e., 870, 980, and 1100[degrees]C) under oxidizing conditions which contain gas phase alkali species. The alumina/mullite cross flow liter material that has consistently been used throughout the flow-through gas phase alkali testing segment of this program, consists of mullite rods or needles that are embedded within an amorphous phase which contains corundum (Al[sub 2]O[sub 3]) and anorthite (CaAl[sub 2]Si[sub 2]O[sub 8]). Due to the rapid cooling rate that was used to produce the alumina/mullite filter disc material from high fire, the matrix consists of 59.6 wt% mullite, 30.5 wt% amorphous, 5.1 wt% anorthite, and 4.8 wt% alumina. The relatively low, as-fabricated, hot strength of this material (841[plus minus]259 psi at 870[degrees]C) is a direct result of the high amorphous content which softens at temperatures of 870[degrees]C. Load versus deflection curves as a function of temperature indicate that this material is relatively brittle up to temperatures of 600[degrees]C. Both a loss of strength, as well as plastic deformation of the matrix occurs at [approximately]700[degrees]C. If cross flow filters are manufactured from an alumina/mullite matrix that contains an [approximately]30.5 wt% amorphous content, we suspect that the plastic nature of the glass phase could potentially serve as a substrate for fines collection during initial filter operation at 700[degrees]C. Similarly the plastic nature could potentially cause deformation of the liter under load.

  8. Thermal/chemical stability of ceramic cross flow filter materials

    SciTech Connect

    Alvin, M.A.; Bahovchin, D.M.; Lippert, T.E.; Tressler, R.E.; McNerney, K.B.

    1992-11-01

    Westinghouse has undertaken a two phase program to determine possible long-term, high temperature influence that advanced coal-based power system environments may have on the stability of the ceramic cross flow filter elements. During the past year, we have principally focused our efforts on developing an understanding of the stability of the alumina/mullite filter material at high temperature (i.e., 870, 980, and 1100{degrees}C) under oxidizing conditions which contain gas phase alkali species. The alumina/mullite cross flow liter material that has consistently been used throughout the flow-through gas phase alkali testing segment of this program, consists of mullite rods or needles that are embedded within an amorphous phase which contains corundum (Al{sub 2}O{sub 3}) and anorthite (CaAl{sub 2}Si{sub 2}O{sub 8}). Due to the rapid cooling rate that was used to produce the alumina/mullite filter disc material from high fire, the matrix consists of 59.6 wt% mullite, 30.5 wt% amorphous, 5.1 wt% anorthite, and 4.8 wt% alumina. The relatively low, as-fabricated, hot strength of this material (841{plus_minus}259 psi at 870{degrees}C) is a direct result of the high amorphous content which softens at temperatures of 870{degrees}C. Load versus deflection curves as a function of temperature indicate that this material is relatively brittle up to temperatures of 600{degrees}C. Both a loss of strength, as well as plastic deformation of the matrix occurs at {approximately}700{degrees}C. If cross flow filters are manufactured from an alumina/mullite matrix that contains an {approximately}30.5 wt% amorphous content, we suspect that the plastic nature of the glass phase could potentially serve as a substrate for fines collection during initial filter operation at 700{degrees}C. Similarly the plastic nature could potentially cause deformation of the liter under load.

  9. Upper-Mantle Flow Driven Dynamic Topography in Eastern Anatolia

    NASA Astrophysics Data System (ADS)

    Sengul Uluocak, Ebru; Pysklywec, Russell; Eken, Tuna; Hakan Gogus, Oguz

    2016-04-01

    Eastern Anatolia is characterized by 2 km plateau uplift -in the last 10 Myrs-, high surface heat flow distribution, shallow Curie-point depth, anomalous gravity field. Seismological observations indicate relatively high Pn and Sn attenuation and significant low seismic velocity anomalies in the region. Moreover, the surface geology is associated predominantly with volcanic rocks in which melt production through mantle upwelling (following lithospheric delamination) has been suggested. It has been long known that the topographic loading in the region cannot be supported by crustal thickness (~45 km) based on the principle of Airy isostasy. Recent global geodynamic studies carried out for evaluating the post-collisional processes imply that there is an explicit dynamic uplift in Eastern Anatolia and its adjacent regions. In this study we investigate the instantaneous dynamic topography driven by 3-D upper-mantle flow in Eastern Anatolia. For this purpose we conducted numerous thermo-mechanical models using a 2-D Arbitrary Lagrangian Eulerian (ALE) finite element method. The available P-wave tomography data extracted along 10 profiles were used to obtain depth-dependent density anomalies in the region. We present resulting dynamic topography maps and estimated 3D mantle flow velocity vectors along these 2-D cross sections for each profile. The residual topography based on crustal thickness and observed topography was calculated and compared with other independent datasets concerning geological deformation and dynamic topography predictions. The results indicate an upper mantle driven dynamic uplift correlated with the under-compensated characteristic in Eastern Anatolia. We discuss our results combined with 3D mantle flow by considering seismic anisotropy studies in the region. Initial results indicate that high dynamic uplift and the localized low Pn velocities in concurrence with Pn anisotropy structures show nearly spatial coherence in Eastern Anatolia.

  10. A dilation-driven vortex flow in sheared granular materials explains a rheometric anomaly.

    PubMed

    Krishnaraj, K P; Nott, Prabhu R

    2016-02-11

    Granular flows occur widely in nature and industry, yet a continuum description that captures their important features is yet not at hand. Recent experiments on granular materials sheared in a cylindrical Couette device revealed a puzzling anomaly, wherein all components of the stress rise nearly exponentially with depth. Here we show, using particle dynamics simulations and imaging experiments, that the stress anomaly arises from a remarkable vortex flow. For the entire range of fill heights explored, we observe a single toroidal vortex that spans the entire Couette cell and whose sense is opposite to the uppermost Taylor vortex in a fluid. We show that the vortex is driven by a combination of shear-induced dilation, a phenomenon that has no analogue in fluids, and gravity flow. Dilatancy is an important feature of granular mechanics, but not adequately incorporated in existing models.

  11. A dilation-driven vortex flow in sheared granular materials explains a rheometric anomaly

    PubMed Central

    Krishnaraj, K. P.; Nott, Prabhu R.

    2016-01-01

    Granular flows occur widely in nature and industry, yet a continuum description that captures their important features is yet not at hand. Recent experiments on granular materials sheared in a cylindrical Couette device revealed a puzzling anomaly, wherein all components of the stress rise nearly exponentially with depth. Here we show, using particle dynamics simulations and imaging experiments, that the stress anomaly arises from a remarkable vortex flow. For the entire range of fill heights explored, we observe a single toroidal vortex that spans the entire Couette cell and whose sense is opposite to the uppermost Taylor vortex in a fluid. We show that the vortex is driven by a combination of shear-induced dilation, a phenomenon that has no analogue in fluids, and gravity flow. Dilatancy is an important feature of granular mechanics, but not adequately incorporated in existing models. PMID:26864086

  12. Characterizing He 2 flow through porous materials using counterflow data

    NASA Technical Reports Server (NTRS)

    Vansciver, Steven W.; Maddocks, J. R.

    1991-01-01

    Proposed space applications, such as the cooling of infrared and x ray telescopes, have generated substantial interest in the behavior of He(2) flowing in porous materials. For design purposes, classical porous media correlations and room temperature data are often used to obtain order of magnitude estimates of expected pressure drops, while the attendant temperature differences are either ignored or estimated using smooth tube correlations. A more accurate alternative to this procedure is suggested by an empirical extension of the two fluid models. It is shown that four empirical parameters are necessary to describe the pressure and temperature differences induced by He(2) flow through a porous sample. The three parameters required to determine pressure differences are measured in counterflow and found to compare favorably with those for isothermal flow. The fourth parameter, the Gorter-Mellink constant, differs substantially from smooth tube values. It is concluded that parameter values determined from counterflow can be used to predict pressure and temperature differences in a variety of flows to an accuracy of about + or - 20 percent.

  13. Characterizing He II flow through porous materials using counterflow data

    NASA Technical Reports Server (NTRS)

    Maddocks, J. R., Jr.; Vansciver, Steven W.

    1990-01-01

    Proposed space applications, such as the cooling of infrared and x ray telescopes, have generated substantial interest in the behavior of He II flowing in porous materials. For design purposes, classical porous media correlations and room temperature data are often used to obtain order of magnitude estimates of expected pressure drops, while the attendant temperature differences are either ignored or estimated using smooth tube correlations. A more accurate alternative to this procedure is suggested by an empirical extension of the two fluid model. It is shown that four empirical parameters are necessary to describe the pressure and temperature differences induced by He II flow through a porous sample. The three parameters required to determine pressure differences are measured in counterflow and found to compare favorably with those for isothermal flow. The fourth parameter, the Gorter-Mellink constant, differs substantially from smooth tube values. It is concluded that parameter values determined from counterflow can be used to predict pressure and temperature differences in a variety of flows to an accuracy of about + or - 20 pct.

  14. Flow-induced compaction of soft poroelastic materials

    NASA Astrophysics Data System (ADS)

    Nijjer, Japinder S.; Hewitt, Duncan R.; Worster, M. Grae; Neufeld, Jerome A.

    2016-11-01

    Fluid flows through poroelastic materials can result in solid deformation driven by the distribution of viscous shear stresses. The porosity and permeability of the solid matrix is altered spatially through a non-trivial coupling to the fluid flow. This behaviour is studied experimentally by examining fluid flow through a packing of soft hydrogel spheres driven by an imposed pressure head. The pressure head is varied, and, for each pressure, the steady-state mass flux and solid deformation are measured. For large pressure gradients, the fluid flow is found to decrease the permeability in such a way as to produce a flux that is independent of the applied pressure gradient. Measurements of the internal deformation, obtained by particle tracking, show that the medium compacts non-uniformly, with the porosity being lower at the outlet compared to the inlet. Intriguingly, we find a reproducible hysteresis of the poroelastic deformation between increasing and decreasing increments of the applied pressure head. The experimental results are compared to a simple one-dimensional model that accounts for non-linear elasticity of the solid and non-constant permeability.

  15. Grow with the Flow: A Dynamic Tale of Blood Clot Formation

    NASA Astrophysics Data System (ADS)

    Leiderman, Karin; Fogelson, Aaron

    2008-11-01

    The body heals injured blood vessels and prevents bleeding by clotting the blood. Clots are primarily made of blood-borne cells and a fibrous material that is assembled at the site of injury in flowing blood. Clot composition and structure change with local chemistry and fluid dynamics, which in turn alter the flow. To better understand this fluid-structure coupling, we have created a mathematical model to simulate the formation of a blood clot in a dynamic fluid environment. The growing clot is represented as a mixed porous medium whose permeability is dependent on the coagulation chemistry within it. The flow field resulting from a clot with specific calculated permeability and size can then be recovered by solving the Navier-Stokes equations with an added friction term. We report on how this complex fluid-structure interaction affects the limiting factor(s) of blood clot growth.

  16. Ultrafast dynamic ellipsometry and spectroscopies of laser shocked materials

    SciTech Connect

    Mcgrane, Shawn David; Bolme, Cindy B; Whitley, Von H; Moore, David S

    2010-01-01

    Ultrafast ellipsometry and transient absorption spectroscopies are used to measure material dynamics under extreme conditions of temperature, pressure, and volumetric compression induced by shock wave loading with a chirped, spectrally clipped shock drive pulse.

  17. Dynamic behavior of particulate/porous energetic materials

    NASA Astrophysics Data System (ADS)

    Nesterenko, Vitali F.; Chiu, Po-Hsun; Braithwaite, C. H.; Collins, Adam; Williamson, David Martin; Olney, Karl L.; Benson, David; McKenzie, Francesca

    2012-03-01

    Dynamic behavior of particulate/porous energetic materials in a broad range of dynamic conditions (low velocity impact and explosively driven expansion of rings) is discussed. Samples of these materials were fabricated using Cold Isostatic Pressing and Hot Isostatic Pressing with and without vacuum encapsulation. The current interest in these materials is due to the combination of their high strength and output of energy under critical conditions of mechanical deformation. They may exhibit high compressive and tensile strength with the ability to undergo bulk distributed fracture resulting in small size reactive fragments. The mechanical properties of these materials and the fragment sizes produced by fracturing are highly sensitive to mesostructure. For example, the dynamic strength of Al-W composites with fine W particles is significantly larger than the strength of composites with coarse W particles at the same porosity. The morphology of W inclusions had a strong effect on the dynamic strength and fracture pattern. Experimental results are compared with numerical data.

  18. Dynamic brittle material response based on a continuum damage model

    SciTech Connect

    Chen, E.P.

    1994-12-31

    The response of brittle materials to dynamic loads was studied in this investigation based on a continuum damage model. Damage mechanism was selected to be interaction and growth of subscale cracks. Briefly, the cracks are activated by bulk tension and the density of activated cracks are described by a Weibull statistical distribution. The moduli of a cracked solid derived by Budiansky and O`Connell are then used to represent the global material degradation due to subscale cracking. This continuum damage model was originally developed to study rock fragmentation and was modified in the present study to improve on the post-limit structural response. The model was implemented into a transient dynamic explicit finite element code PRONTO 2D and then used for a numerical study involving the sudden stretching of a plate with a centrally located hole. Numerical results characterizing the dynamic responses of the material were presented. The effect of damage on dynamic material behavior was discussed.

  19. Importance of material matching in the calibration of asymmetric flow field-flow fractionation: material specificity and nanoparticle surface coating effects on retention time

    NASA Astrophysics Data System (ADS)

    Qu, Haiou; Quevedo, Ivan R.; Linder, Sean W.; Fong, Andrew; Mudalige, Thilak K.

    2016-10-01

    Asymmetric flow field-flow fractionation (AF4) coupled with dynamic light scattering or multiangle light scattering detectors is a promising technique for the size-based separation of colloidal particles (nano- and submicron scale) and the online determination of the particle size of the separated fractions in aqueous suspensions. In most cases, the applications of these detectors are problematic due to the material-specific properties of the analyte that results in erroneous calculations, and as an alternative, different nanoparticle size standards are required to properly calibrate the size-based retention in AF4. The availability of nanoparticle size standards in different materials is limited, and this deviation from ideal conditions of retention is mainly due to material-specific and particle coating-specific membrane-particle interactions. Here, we present an experimental method on the applicability of polystyrene nanoparticles (PS NP) as standard for AF4 calibration and compare with gold nanoparticle (Au NP) standards having different nominal sizes and surface functionalities.

  20. Simulations of ductile flow in brittle material processing

    SciTech Connect

    Luh, M.H.; Strenkowski, J.S.

    1988-12-01

    Research is continuing on the effects of thermal properties of the cutting tool and workpiece on the overall temperature distribution. Using an Eulerian finite element model, diamond and steel tools cutting aluminum have been simulated at various, speeds, and depths of cut. The relative magnitude of the thermal conductivity of the tool and the workpiece is believed to be a primary factor in the resulting temperature distribution in the workpiece. This effect is demonstrated in the change of maximum surface temperatures for diamond on aluminum vs. steel on aluminum. As a preliminary step toward the study of ductile flow in brittle materials, the relative thermal conductivities of diamond on polycarbonate is simulated. In this case, the maximum temperature shifts from the rake face of the tool to the surface of the machined workpiece, thus promoting ductile flow in the workpiece surface.

  1. A new dynamic model for heterogeneous traffic flow

    NASA Astrophysics Data System (ADS)

    Tang, T. Q.; Huang, H. J.; Zhao, S. G.; Shang, H. Y.

    2009-06-01

    Based on the property of heterogeneous traffic flow, we in this Letter present a new car-following model. Applying the relationship between the micro and macro variables, a new dynamic model for heterogeneous traffic flow is obtained. The fundamental diagram and the jam density of the heterogeneous traffic flow consisting of bus and car are studied under three different conditions: (1) without any restrictions, (2) under the action of the traffic control policy that restrains some private cars and (3) using bus to replace the private cars restrained by the traffic control policy. The numerical results show that our model can describe some qualitative properties of the heterogeneous traffic flow consisting of bus and car, which verifies that our model is reasonable.

  2. Dynamics of plasma blobs in a shear flow.

    PubMed

    Diallo, A; Fasoli, A; Furno, I; Labit, B; Podestà, M; Theiler, C

    2008-09-12

    The global dynamic of plasma blobs in a shear flow is investigated in a simple magnetized torus using the spatial Fourier harmonics (k-space) framework. Direct experimental evidence of a linear drift in k space of the density fluctuation energy synchronized with blob events is presented. During this drift, an increase of the fluctuation energy and a production of the kinetic energy associated with blobs are observed. The energy source of the blob is analyzed using an advection-dissipation-type equation that includes blob-flow exchange energy, linear drift in k space, nonlinear processes, and viscous dissipations. We show that blobs tap their energy from the dominant ExB vertical background flow during the linear drift stage. The exchange of energy is unidirectional as there is no evidence that blobs return energy to the flow.

  3. Dynamics of Plasma Blobs in a Shear Flow

    SciTech Connect

    Diallo, A.; Fasoli, A.; Furno, I.; Labit, B.; Podesta, M.; Theiler, C.

    2008-09-12

    The global dynamic of plasma blobs in a shear flow is investigated in a simple magnetized torus using the spatial Fourier harmonics (k-space) framework. Direct experimental evidence of a linear drift in k space of the density fluctuation energy synchronized with blob events is presented. During this drift, an increase of the fluctuation energy and a production of the kinetic energy associated with blobs are observed. The energy source of the blob is analyzed using an advection-dissipation-type equation that includes blob-flow exchange energy, linear drift in k space, nonlinear processes, and viscous dissipations. We show that blobs tap their energy from the dominant ExB vertical background flow during the linear drift stage. The exchange of energy is unidirectional as there is no evidence that blobs return energy to the flow.

  4. Graphics and flow visualization in computational fluid dynamics

    NASA Technical Reports Server (NTRS)

    Buning, P. G.; Steger, J. L.

    1985-01-01

    Techniques for displaying two- and three-dimensional flowfield solutions are described. Several methods of illustrating flow structure are addressed including particle tracing, simulated oil flow, and shock finding. These are incorporated into an interactive graphics program for CFD flowfields, called PLOT3D. Emphasis is made on the difficulty in visualizing three-dimensional flow features, and the importance of color, fast 3D image manipulation, and dynamic movie play-back in displaying such flows. The need for advanced algorithms to identify shock waves, vortices, and separation lines is pointed out. It is likely that the supercomputer will be needed for this process because of the size of 3D and/or unsteady CFD databases.

  5. Three-Dimensional Visualization of Material Flow During Friction Stir Welding of Steel and Aluminum

    NASA Astrophysics Data System (ADS)

    Morisada, Yoshiaki; Imaizumi, Takuya; Fujii, Hidetoshi; Matsushita, Muneo; Ikeda, Rinsei

    2014-11-01

    Material flow is a key phenomenon to obtain sound joints by friction stir welding (FSW), and it is highly dependent of the welded material. It is well known that the optimal FSW condition depends on the welded material. However, the material flow during FSW has not been totally clarified in spite of many researches. Especially, the material flow of steel during FSW is still unclear. It seems difficult to understand the material flow by the traditional method such as the tracer method or observation of the microstructure in the stir zone. Therefore, in this study, the material flow of steel was three dimensionally visualized by x-ray radiography using two pairs of x-ray transmission real-time imaging systems, and was then compared with the material flow of aluminum. The result revealed the effect of the welded material on the material flow during FSW.

  6. Visualization of water flow during filtration using flat filtration materials

    NASA Astrophysics Data System (ADS)

    Bílek, Petr; Šidlof, Petr; Hrůza, Jakub

    2012-04-01

    Filtration materials are very important elements of some industrial appliances. Water filtration is a separation of solid materials from fluid. Solid particles are captured on the frontal area of the filtration textile and only liquid passes through it. It is important to know the filtration process in a detailed way to be able to develop filtration materials. Visualization of filtration process enables a better view of the filtration. This method also enables to determine efficiency and homogeneity of filtration using image analysis. For this purpose, a new waterfiltration measuring setup was proposed and constructed. Filtration material is mounted into the optically transparent place in the setup. Laser sheet is directed into this place as in the case of Particle Image Velocimetry measuring method. Monochrome and sensitive camera records the light scattered by seeding particles in water. The seeding particles passing through the filter serve for measuring filtration efficiency, and also for visualization of filtration process. Filtration setup enables to measure also the pressure drop and a flow. The signals are processed by National Instruments compactDAQ system and UMA software. Microfibrous and nanofibrous filtration materials are tested by this measuring method. In the case of nanofibrous filtration, appropriate size of seeding particles is needed to be used to perform a process of filtration.

  7. Dynamic Deformation Properties of Energetic Composite Materials

    DTIC Science & Technology

    2005-04-01

    references are provided for further reading. Materials The materials that have been used are ultrafine PETN and RDX prepared by a proprietary method by ICI...density of the loose powder on delivery is ~15 % of the theoretical maximum density (TMD). The ultrafine HNS that was used was HNS IV as supplied by...ultrafine PETN . A - Point at which initiation takes place; B - Detonation wave travelling at 5.6 ± 0.3 mm ms-1. 37 Figure 1.31. Negative streak

  8. Creep and flow of glasses: strain response linked to the spatial distribution of dynamical heterogeneities

    PubMed Central

    Sentjabrskaja, T.; Chaudhuri, P.; Hermes, M.; Poon, W. C. K.; Horbach, J.; Egelhaaf, S. U.; Laurati, M.

    2015-01-01

    Mechanical properties are of central importance to materials sciences, in particular if they depend on external stimuli. Here we investigate the rheological response of amorphous solids, namely colloidal glasses, to external forces. Using confocal microscopy and computer simulations, we establish a quantitative link between the macroscopic creep response and the microscopic single-particle dynamics. We observe dynamical heterogeneities, namely regions of enhanced mobility, which remain localized in the creep regime, but grow for applied stresses leading to steady flow. These different behaviors are also reflected in the average particle dynamics, quantified by the mean squared displacement of the individual particles, and the fraction of active regions. Both microscopic quantities are found to be proportional to the macroscopic strain, despite the non-equilibrium and non-linear conditions during creep and the transient regime prior to steady flow. PMID:26153523

  9. Dynamic Failure of Materials: A Review

    DTIC Science & Technology

    2010-08-01

    Investigation of the Rupture of a Plexiglass Plate by Means of an Optical Method Involving High Speed Filming of the Shadows Originating Around Holes...Neville Mott (3) proposed a theoretical framework that includes inertial effects during the rapid crack growth phase. At high crack speeds , Mott... high speeds in high -energy events where other crack modes are prohibited by confinement. 14 Dynamic brittle fracture has a rich history and a

  10. Single file dynamics in soft materials.

    PubMed

    Taloni, Alessandro; Flomenbom, Ophir; Castañeda-Priego, Ramón; Marchesoni, Fabio

    2017-02-08

    The term single file (SF) dynamics refers to the motion of an assembly of particles through a channel with cross-sections comparable to the particles' diameter. Single file diffusion (SFD) is then the diffusion of a tagged particle in a single file, i.e., under the condition that particle passing is not allowed. SFD accounts for a large variety of processes in nature, including diffusion of colloids in synthetic and natural channels, biological motors along molecular chains, electrons in proteins and liquid helium, ions through membranes, just to mention a few examples. Albeit introduced in 1965s, over the last decade the classical notion of SF dynamics has been generalised to account for a more realistic modelling of the particle properties, file geometry, particle-particle and channel-particle interactions, which paves the way to remarkable applications of the SF model, for instance, in the technology of bio-integrated nanodevices. We provide here a comprehensive review of the recent advances in the theory of SF dynamics with the purpose of spurring further experimental work.

  11. Dynamics of prolate spheroidal elastic particles in confined shear flow.

    PubMed

    Villone, M M; D'Avino, G; Hulsen, M A; Maffettone, P L

    2015-12-01

    We investigate through numerical simulations the dynamics of a neo-Hookean elastic prolate spheroid suspended in a Newtonian fluid under shear flow. Both initial orientations of the particle within and outside the shear plane and both unbounded and confined flow geometries are considered. In unbounded flow, when the particle starts on the shear plane, two stable regimes of motion are found, i.e., trembling, where the particle shape periodically elongates and compresses in the shear plane and the angle between its major semiaxis and the flow direction oscillates around a positive mean value, and tumbling, where the particle shape periodically changes and its major axis performs complete revolutions around the vorticity axis. When the particle is initially oriented out of the shear plane, more complex dynamics arise. Geometric confinement of the particle between the moving walls also influences its deformation and regime of motion. In addition, when the particle is initially located in an asymmetric position with respect to the moving walls, particle lateral migration is detected. The effects on the particle dynamics of the geometric and physical parameters that rule the system are investigated.

  12. Dynamic strength properties of permeable fibrous materials

    SciTech Connect

    Ivanchuk, A.A.; Karpinos, D.M.; Kondrat'ev, Yu.V.; Nezhentsev, Yu.I.; Rutkovskii, A.E.; Bikernieks, V.Ya.; Peterson, O.O.; Pekhovich, V.A.

    1986-11-01

    The authors assess the porosity and fracture properties of porous samples of molybdenum, tungsten, and steel-Kh18N9T through a variety of mechanical tests including impact, bend, and notch. They study the interplay and interdependence of these properties in view of looking for materials suited for processes of transpiration cooling and sound and vibration damping.

  13. Comment on "Flow of wet granular materials: A numerical study"

    NASA Astrophysics Data System (ADS)

    Chareyre, Bruno

    2017-07-01

    The effective stress model of Khamseh et al., Phys. Rev. E 92, 022201 (2015), 10.1103/PhysRevE.92.022201 is in semiquantitative agreement with the shear stress in simulated steady state flow of a wet granular material. Nonetheless, the predictions are increasingly biased at low normal pressure. The approximation of the capillary stress by a spherical tensor in this model is a sufficient cause of the prediction errors, as shown in this Comment. The re-examination reveals an excellent agreement between the data and the effective stress expression formerly introduced for similar systems, further validating a yet unexplained empirical result.

  14. Granular Dilatancy and its Effect on Debris-flow Dynamics

    NASA Astrophysics Data System (ADS)

    Iverson, R. M.; George, D. L.

    2012-12-01

    Landslides and debris flows commonly exhibit the effects of variable granular dilatancy, but incorporation of these effects in predictive models of debris-flow dynamics has been lacking. We have developed a depth-averaged model of debris-flow initiation and motion that includes the effects of variable dilatancy without stipulating its influence on rheology. Instead, the apparent rheology of Coulomb-frictional debris evolves during coupled evolution of the grain concentration m, basal pore-fluid pressure, flow thickness, and flow velocity. The dilatancy angle ψ plays an intermediary role in this evolution and obeys the simple relationship tan ψ = m-meq, where meq is the grain concentration in equilibrium with the ambient stress state and flow rate. Results of recent stress-controlled rheometric experiments by Boyer et al. (DOI: 10.1103/PhysRevLett.107.188301) provide our basis for estimating meq. Relaxation of m toward meq, coupled with evolution of pore pressure, allows our model to simulate a smooth transition from static limiting equilibrium of slopes to disequilibrium flow dynamics. Use of variable friction coefficients or dam-break initial conditions is unnecessary. We have evaluated predictions of our model in three ways: (1) by examining physical implications of exact solutions of simplified model equations, (2) by comparing numerical solutions with results of controlled experiments at the USGS debris-flow flume, and (3) by comparing numerical predictions with the behavior of a large (~50 million m3) debris flow that occurred at Mt. Meager, British Columbia, in 2010. Model predictions depend mostly on initial conditions, flow-path topography, and the value of a single dimensionless parameter that represents the ratio of two key timescales. One timescale governs downslope, gravity-driven motion of debris, and the other governs pore-pressure diffusion. Values of these timescales are readily calculated from source-area geometry and standard geotechnical

  15. Dissipative particle dynamics modeling of blood flow in arterial bifurcations

    NASA Astrophysics Data System (ADS)

    Li, Xuejin; Lykov, Kirill; Pivkin, Igor V.; Karniadakis, George Em

    2013-11-01

    The motion of a suspension of red blood cells (RBCs) flowing in bifurcations is investigated using both low-dimensional RBC (LD-RBC) and multiscale RBC (MS-RBC) models based on dissipative particle dynamics (DPD). The blood flow is first simulated in a symmetric geometry between the diverging and converging channels to satisfy the periodic flow assumption along the flow direction. The results show that the flowrate ratio of the daughter channels and the feed hematocrit level has considerable influence on blood-plasma separation. We also propose a new method to model the inflow and outflow boundaries for the blood flow simulations: the inflow at the inlet is duplicated from a fully developed flow generated by DPD fluid with periodic boundary conditions; the outflow in two adjacent regions near the outlet is controlled by adaptive forces to keep the flowrate and velocity gradient equal, while the particles leaving the microfluidic channel at the outlet at each time step are removed from the system. The simulation results of the developing flow match analytical solutions from continuum theory. Plasma skimming and the all-or-nothing phenomenon of RBCs in bifurcation have been investigated in the simulations. The simulation results are consistent with previous experimental results and theoretical predictions. This work is supported by the NIH Grant R01HL094270.

  16. Dynamics of an inverted flexible plate in a uniform flow

    NASA Astrophysics Data System (ADS)

    Tang, Chao; Liu, Nan-Sheng; Lu, Xi-Yun

    2015-07-01

    The dynamics of an inverted flexible plate with a free leading-edge and a fixed trailing-edge in a uniform flow has been studied numerically by an immersed boundary-lattice Boltzmann method for the fluid flow and a finite element method for the plate deformation. Mechanisms underlying the dynamics of the fluid-plate system are elucidated systematically. A series of distinct states of the plate deformation and motion are identified and can be described as straight, flapping, deflected, deflected-flapping, and asymmetric-flapping states. Which state to occur depends mainly on the bending stiffness and aspect ratio of the plate. The forces exerted on the plate and the elastic strain energy of the plate are analyzed. It is found that the flapping state can improve the conversion of fluid kinetic energy to elastic strain energy. In addition, the effects of the mass ratio of the plate and the fluid, the Reynolds number, and the angle of attack of the uniform flow on the dynamics and the elastic strain energy of flexible plate are also investigated in detail. The vortical structures around the plate are given to discuss the connection of the evolution of vortices with the plate deformation and motion. The results obtained in this study provide physical insight into the understanding of the mechanisms on the dynamics of the fluid-plate system.

  17. Mantle Flow Pattern and Dynamic Topography beneath the Eastern US

    NASA Astrophysics Data System (ADS)

    Liu, S.; King, S. D.; Adam, C. M.; Long, M. D.; Benoit, M. H.; Kirby, E.

    2015-12-01

    The complex tectonic history of the eastern US over the past billion years includes episodes of subduction and rifting associated with two complete cycles of supercontinent assembly and breakup. Both the previous global tomography models (S40RTS, SAVANI, TX2011, GyPSuM, SMEAN) and the analysis of the shear-wave splitting from the broadband seismic stations find a distinct coast-to-inland differentiation pattern in the lithosphere and upper mantle. The Mid-Atlantic Geophysical Integrative Collaboration (MAGIC) includes a dense linear seismic array from the Atlantic coast of Virginia to the western boarder of Ohio, crossing several different tectonic zones. To derive the regional mantle flow pattern along with its surface expression such as dynamic topography and aid the interpretation of the seismic observations, we are building a new geodynamic model based on ASPECT (Advanced Solver for Problems in Earth CovecTion) that uses buoyancy derived from seismic tomography along with realistic lithosphere and sub-lithosphere structure. At present, we use S40RTS and SAVANI tomography models together with the temperature-dependent viscosity to compute the mantle flow and dynamic topography. Beneath the eastern US, the upper mantle flow in our model is primarily parallel to the trend of the Appalachian belt, which is broadly consistent with the direction of the local shear-wave splitting. The dynamic topography results exhibit a coast-to-inland magnitude differentiation along the MAGIC seismic deployment. The numerical tests also show that both the magnitude and pattern of the dynamic topography are quite sensitive to the density perturbation and rigidity of the lithosphere/sub-lithosphere. Our future work involves using other tomography and viscosity models to obtain the mantle flow pattern as well as the resulting dynamic topography and geoid.

  18. Effects of polymer retention on dynamics of single phase flow

    NASA Astrophysics Data System (ADS)

    Parsa, Shima; Weitz, David

    2014-11-01

    We study the effect of adsorption of polymer solution on dynamics of a single phase flow in a model porous medium. We use confocal microscopy to fully visualize the flow of fluid in 3D micromodel of porous media. Polymer flooding is known to be an effective method for enhanced oil recovery. However, the physical mechanism is not clearly understood. We study the effect of polymer retention on the dynamics of single phase flow using particle image velocimetery. The distribution of velocities in the medium changes greatly after flow of high concentrations of polymer through the medium. Comparing the magnitude of velocities before and after the polymer flow, we observe reduction of accessible pores to the fluid at similar injection rates. Independent measurement of the permeability of the medium confirms the decrease in the porosity. Measurements of the retention of polymer in porous media shows a weak dependence on the hydrodynamic radius of the polymer. In these experiments, the viscoelastic behavior of the polymer is isolated from velocity measurements.

  19. Water Flow in Karst Aquifer Considering Dynamically Variable Saturation Conduit

    NASA Astrophysics Data System (ADS)

    Tan, Chaoqun; Hu, Bill X.

    2017-04-01

    The karst system is generally conceptualized as dual-porosity system, which is characterized by low conductivity and high storage continuum matrix and high conductivity and quick flow conduit networks. And so far, a common numerical model for simulating flow in karst aquifer is MODFLOW2005-CFP, which is released by USGS in 2008. However, the steady-state approach for conduit flow in CFP is physically impractical when simulating very dynamic hydraulics with variable saturation conduit. So, we adopt the method proposed by Reimann et al. (2011) to improve current model, in which Saint-Venant equations are used to model the flow in conduit. Considering the actual background that the conduit is very big and varies along flow path and the Dirichlet boundary varies with rainfall in our study area in Southwest China, we further investigate the influence of conduit diameter and outflow boundary on numerical model. And we also analyze the hydraulic process in multi-precipitation events. We find that the numerical model here corresponds well with CFP for saturated conduit, and it could depict the interaction between matrix and conduit during very dynamic hydraulics pretty well compare with CFP.

  20. Three-dimensional flow dynamics of an active submarine channel

    NASA Astrophysics Data System (ADS)

    Sumner, E. J.; Dorrell, R. M.; Peakall, J.; Darby, S. E.; Parsons, D. R.; Wynn, R.

    2012-12-01

    Field scale submarine channel gravity currents are notoriously difficult to measure and thus directly investigate due to their inaccessible location and infrequent nature, which is compounded by present sea-level high-stand. An exception to this is the almost continuous density-driven current that results from the inflow of saline Mediterranean water, via the Bosporus strait, into the Black Sea. This flow has carved a sinuous channel system in water depths of 70 to 120 m. The relatively shallow depths of the channel and the continuous nature of this current provide a rare opportunity to study three-dimensional flow dynamics and the interaction of the flow with a seafloor channel network. Thus, it provides a rare analogue for channelized dilute sediment-laden turbidity currents. Sediment erosion, transport and deposition within submarine channel bends is primarily controlled by the magnitude and direction of near bed flow. Flow around channel bends is characterized by a helical or spiralling structure. In rivers this helical flow is characterized by near-surface fluid moving toward the outer bank and near-bed fluid moving toward the inner bank. Following fierce debate over the last decade, it is now accepted that helical flow in submarine channel bends can display a variety of complex structures. Most importantly for understanding sediment transport, near bed flow can be directed towards the outer bank, which is in the opposite sense to in a river. The next challenge is to understand what the exact controls on the orientation of helical flow cells within submarine flows are, and their spatial evolution around bends. We present data from the Black Sea showing how the three-dimensional velocity and density of a submarine gravity current evolves at multiple cross sections as the flow travels around a bend. We use this data to calculate the magnitude, relative importance and interaction of centrifugal, coriolis and pressure gradients in controlling the structure of

  1. Anomalous flow behavior in nanochannels: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Murad, Sohail; Luo, Lin; Chu, Liang-Yin

    2010-06-01

    We report molecular dynamics simulations of flow of water in nanochannels with a range of surface wettability characteristics (hydrophobic to strongly hydrophilic) and driving forces (pressures). Our results show apparently anomalous behavior. At low pressures, the rate is higher in nanochannels with hydrophilic surfaces than that with hydrophobic surfaces; however, with high pressure driven flow we observe opposite trends. This apparently anomalous behavior can be explained on the basis of molecular thermodynamics and fluid mechanics considerations. Understanding such behavior is important in many nanofluidic devices such as nanoreactors, nanosensors, and nanochips that are increasingly being designed and used.

  2. Computational Methods for Analyzing Fluid Flow Dynamics from Digital Imagery

    SciTech Connect

    Luttman, A.

    2012-03-30

    The main goal (long term) of this work is to perform computational dynamics analysis and quantify uncertainty from vector fields computed directly from measured data. Global analysis based on observed spatiotemporal evolution is performed by objective function based on expected physics and informed scientific priors, variational optimization to compute vector fields from measured data, and transport analysis proceeding with observations and priors. A mathematical formulation for computing flow fields is set up for computing the minimizer for the problem. An application to oceanic flow based on sea surface temperature is presented.

  3. Dynamics of poloidal flows in enhanced reverse shear bifurcation

    SciTech Connect

    Srinivasan, R.; Avinash, K.

    2005-07-15

    A simple reduced enhanced reverse shear (RERS) model is constructed to study the dynamics of poloidal flows during the ERS transition. This model predicts that a reversal of poloidal flow shear occurs just prior to the transition, as seen in experiment [R. E. Bell et al., Phys. Rev. Lett. 81, 1429 (1998)]. This transition front propagates until the radial location where the safety factor (q) is minimum and becomes locked there due to insufficient input power to overcome the threshold requirement for the bifurcation. This study also reveals that there can be many routes to ERS transition depending upon various tunable parameters.

  4. Compaction dynamics of crunchy granular material

    NASA Astrophysics Data System (ADS)

    Guillard, François; Golshan, Pouya; Shen, Luming; Valdès, Julio R.; Einav, Itai

    2017-06-01

    Compaction of brittle porous material leads to a wide variety of densification patterns. Static compaction bands occurs naturally in rocks or bones, and have important consequences in industry for the manufacturing of powder tablets or metallic foams for example. Recently, oscillatory compaction bands have been observed in brittle porous media like snow or cereals. We will discuss the great variety of densification patterns arising during the compaction of puffed rice, including erratic compaction at low velocity, one or several travelling compaction bands at medium velocity and homogeneous compaction at larger velocity. The conditions of existence of each pattern are studied thanks to a numerical spring lattice model undergoing breakage and is mapped to the phase diagram of the patterns based on dimensionless characteristic quantities. This also allows to rationalise the evolution of the compaction behaviour during a single test. Finally, the localisation of compaction bands is linked to the strain rate sensitivity of the material.

  5. Simultaneous dynamic electrical and structural measurements of functional materials

    NASA Astrophysics Data System (ADS)

    Vecchini, C.; Thompson, P.; Stewart, M.; Muñiz-Piniella, A.; McMitchell, S. R. C.; Wooldridge, J.; Lepadatu, S.; Bouchenoire, L.; Brown, S.; Wermeille, D.; Bikondoa, O.; Lucas, C. A.; Hase, T. P. A.; Lesourd, M.; Dontsov, D.; Cain, M. G.

    2015-10-01

    A new materials characterization system developed at the XMaS beamline, located at the European Synchrotron Radiation Facility in France, is presented. We show that this new capability allows to measure the atomic structural evolution (crystallography) of piezoelectric materials whilst simultaneously measuring the overall strain characteristics and electrical response to dynamically (ac) applied external stimuli.

  6. A continuum theory for modeling the dynamics of crystalline materials.

    PubMed

    Xiong, Liming; Chen, Youping; Lee, James D

    2009-02-01

    This paper introduces a multiscale field theory for modeling and simulation of the dynamics of crystalline materials. The atomistic formulation of a multiscale field theory is briefly introduced. Its applicability is discussed. A few application examples, including phonon dispersion relations of ferroelectric materials BiScO3 and MgO nano dot under compression are presented.

  7. Simultaneous dynamic electrical and structural measurements of functional materials

    SciTech Connect

    Vecchini, C.; Stewart, M.; Muñiz-Piniella, A.; Wooldridge, J.; Thompson, P.; McMitchell, S. R. C.; Bouchenoire, L.; Brown, S.; Wermeille, D.; Lucas, C. A.; Lepadatu, S.; Bikondoa, O.; Hase, T. P. A.; Lesourd, M.; Dontsov, D.; Cain, M. G.

    2015-10-15

    A new materials characterization system developed at the XMaS beamline, located at the European Synchrotron Radiation Facility in France, is presented. We show that this new capability allows to measure the atomic structural evolution (crystallography) of piezoelectric materials whilst simultaneously measuring the overall strain characteristics and electrical response to dynamically (ac) applied external stimuli.

  8. Regional material flow accounting and environmental pressures: the Spanish case.

    PubMed

    Sastre, Sergio; Carpintero, Óscar; Lomas, Pedro L

    2015-02-17

    This paper explores potential contributions of regional material flow accounting to the characterization of environmental pressures. With this aim, patterns of material extraction, trade, consumption, and productivity for the Spanish regions were studied within the 1996-2010 period. The main methodological variation as compared to whole-country based approaches is the inclusion of interregional trade, which can be separately assessed from the international exchanges. Each region was additionally profiled regarding its commercial exchanges with the rest of the regions and the rest of the world and the related environmental pressures. Given its magnitude, interregional trade is a significant source of environmental pressure. Most of the exchanges occur across regions and different extractive and trading patterns also arise at this scale. These differences are particularly great for construction minerals, which in Spain represent the largest share of extracted and consumed materials but do not cover long distances, so their impact is visible mainly at the regional level. During the housing bubble, economic growth did not improve material productivity.

  9. Computational fluid dynamics analysis of salivary flow and its effect on sialolithogenesis

    PubMed Central

    Zhu, P; Lin, Y; Lin, H; Xu, Y; Zheng, QY; Han, Y

    2014-01-01

    OBJECTIVE Sialolithiasis is a common disease caused by intraductal stones, formed by reduction in salivary flow, salivary stagnation, and metabolic events. We used computational fluid dynamics to investigate changes in salivary flow field around parotid stones of different shapes. MATERIALS AND METHODS Three-dimensional configurations of the Stensen’s duct were reconstructed from computed tomography sialographic images. Fluid dynamics modeling was used to analyze the salivary flow field around stones under unstimulated and stimulated conditions. RESULTS The majority of sialoliths were oval-shaped (59/98), followed by irregular (24/98) and round (15/98). Salivary velocity was significantly higher around streamlined stones, compared with round (P = 0.013) and oval (P = 0.025) types. Changes in salivary flow field around sialoliths were found to affect the pattern of mineral deposition in saliva. The area of low velocity around the round stone was double the size observed around the streamlined stone during the unstimulated state, whereas in the stimulated state, local vortexes were formed on the downstream side of round and oval stones. CONCLUSIONS Salivary flow field around sialoliths plays an important role in the progression of multicentric stones, and analysis of the salivary dynamics during sialolithiasis may provide deeper understandings of the condition and aid in developing successful treatment strategies. PMID:24164693

  10. Translational versus rotational energy flow in water solvation dynamics

    NASA Astrophysics Data System (ADS)

    Rey, Rossend; Hynes, James T.

    2017-09-01

    Early molecular dynamics simulations discovered an important asymmetry in the speed of water solvation dynamics for charge extinction and charge creation for an immersed solute, a feature representing a first demonstration of the breakdown of linear response theory. The molecular level mechanism of this asymmetry is examined here via a novel energy flux theoretical approach coupled to geometric probes. The results identify the effect as arising from the translational motions of the solute-hydrating water molecules rather than their rotational/librational motions, even though the latter are more rapid and dominate the energy flow.

  11. Dual exposure interferometry. [gas dynamics and flow visualization

    NASA Technical Reports Server (NTRS)

    Smeets, G.; George, A.

    1982-01-01

    The application of dual exposure differential interferometry to gas dynamics and flow visualization is discussed. A differential interferometer with Wallaston prisms can produce two complementary interference fringe systems, depending on the polarization of the incident light. If these two systems are superimposed on a film, with one exposure during a phenomenon, the other before or after, the phenomenon will appear on a uniform background. By regulating the interferometer to infinite fringe distance, a resolution limit of approximately lambda/500 can be obtained in the quantitative analysis of weak phase objects. This method was successfully applied to gas dynamic investigations.

  12. Meeting on flows of granular materials in complex geometries

    SciTech Connect

    Passman, S.L.; Fukushima, E.; Evans, R.E.

    1994-11-01

    The International Energy Agency Fossil Fuel Multiphase Flow Sciences Agreement has been in effect since 1986. The traditional mechanism for the effort has been information exchange, effected by the inclusion of scientists in annual Executive committee meetings, by exchange of reports and papers, and by visits of scientists to one another`s institutions. In a sequence of informal meetings and at the 1993 Executive committee meeting, held in Pittsburgh, US in March 1994, it was decided that more intensive interactions could be productive. A candidate for such interactions would be specific projects. Each of these would be initiated through a meeting of scientists in which feasibility of the particular project was decided, followed by relatively intense international co-operation in which the work would be done. This is a report of the first of these meetings. Official or unofficial representatives from Canada, italy, japan, mexico, the United Kingdom, and the US met in Albuquerque, New Mexico, US, to consider the subject Flows of Granular Materials in Complex Geometries. Representatives of several other countries expressed interest but were unable to attend this meeting. Sixteen lectures were given on aspects of this topic. It was decided that a co-operative effort was desirable and possible. The most likely candidate for the area of study would be flows in bins and hoppers. Each of the countries wishing to co-operate will pursue funding for its effort. This report contains extended abstracts of the sixteen presentations and a transcription of the final discussion.

  13. Dynamics of AHL mediated quorum sensing under flow and non-flow conditions

    NASA Astrophysics Data System (ADS)

    Meyer, Andrea; Megerle, Judith A.; Kuttler, Christina; Müller, Johannes; Aguilar, Claudio; Eberl, Leo; Hense, Burkhard A.; Rädler, Joachim O.

    2012-04-01

    Quorum sensing (QS) describes the capability of microbes to communicate with each other by the aid of small molecules. Here we investigate the dynamics of QS-regulated gene expression induced by acylhomoserine lactones (AHLs) in Pseudomonas putida IsoF containing a green fluorescent protein-based AHL reporter. The fluorescence time course of individual colonies is monitored following the external addition of a defined AHL concentration to cells which had previously reached the QS-inactive state in AHL-free medium. Using a microfluidic setup the experiment is performed both under flow and non-flow conditions. We find that without supplying external AHL gene expression is induced without flow while flow suppresses the induction. Both without and with flow, at a low AHL concentration the fluorescence onset is significantly delayed while fluorescence starts to increase directly upon the addition of AHL at a high concentration. The differences between no flow and flow can be accounted for using a two-compartment model. This indicates AHL accumulation in a volume which is not affected by the flow. The experiments furthermore show significant cell-to-cell and colony-to-colony variability which is discussed in the context of a compartmentalized QS mechanism.

  14. Modeling granular material flows: The angle of repose, fluidization and the cliff collapse problem

    NASA Astrophysics Data System (ADS)

    Holsapple, Keith A.

    2013-07-01

    I discuss theories of granular material flows, with application to granular flows on the earth and planets. There are two goals. First, there is a lingering belief of some that the standard continuum plasticity Mohr-Coulomb and/or Drucker-Prager models are not adequate for many large-scale granular flow problems. The stated reason for those beliefs is the fact that the final slopes of the run-outs in collapse, landslide problems, and large-scale cratering are well below the angle of repose of the material. That observation, combined with the supposition that in those models flow cannot occur with slopes less than the angle of repose, has led to a number of researchers suggesting a need for lubrication or fluidization mechanisms and modeling. That issue is investigated in detail and shown to be false. A complete analysis of slope failures according to the Mohr-Coulomb model is presented, with special attention to the relations between the angle of repose and slope failures. It is shown that slope failure can occur for slope angles both larger than and smaller than the angle of repose. Second, to study the details of landslide run-outs, finite-difference continuum code simulations of the prototypical cliff collapse problem, using the classical plasticity models, are presented, analyzed and compared to experiments. Although devoid of any additional fluidization models, those simulations match experiments in the literature extremely well. The dynamics of this problem introduces additional important features relating to the run-out and final slope angles. The vertical free surface begins to fall at the initial 90° and flow continues to a final slope less than 10°. The detail in the calculation is examined to show why flow persists at slope angles that appear to be less than the angle of repose. The motions include regions of solid-like, fluid-like, and gas-like flows without invoking any additional models.

  15. Flow Simulations of The Dynamics of a Perturbed Solid-Body Rotation Flow

    NASA Astrophysics Data System (ADS)

    Wang, Shixiao; Feng, Chunjuan; Liu, Feng; Rusak, Zvi

    2016-11-01

    DNS is conducted to study the 3-D flow dynamics of a base solid-body rotation flow with a uniform axial velocity in a finite-length pipe. The simulation results describe the neutral stability line in response to either axisymmetric or 3-dimensional perturbations in a diagram of Reynolds number (Re , based on inlet axial velocity and pipe radius) versus the incoming flow swirl ratio (ω). This line is in good agreement with the neutral stability line recently predicted by the linear stability theory of Wang et al. (2016). The Wang & Rusak (1996) axisymmetric instability mechanism and evolution to an axisymmetric breakdown state is recovered in the simulations at certain operational conditions in terms of Re and ω. However, at other operational conditions there exists a dominant, 3-dimensional spiral type of instability mode that agrees with the linear stability theory of Wang et al. (2016). The growth of this mode leads to a spiral type of flow roll-up that subsequently nonlinearly saturates on a rotating spiral type of vortex breakdown. The computed time history of the velocity components at a certain point in the flow is used to describe 3-dimensional phase portraits of the flow global dynamics and its long-term behavior.

  16. Performance and Flow Dynamics Studies of Polymeric Optofluidic SERS Sensors

    NASA Astrophysics Data System (ADS)

    Uusitalo, S.; Hiltunen, J.; Karioja, P.; Siitonen, S.; Kontturi, V.; Myllylä, R.; Kinnunen, M.; Meglinski, I.

    2015-09-01

    We present a polymer-based optofluidic surface enhanced Raman scattering chip for biomolecule detection, serving as a disposable sensor choice with cost-effective production. The SERS substrate is fabricated by using industrial roll-to-roll UV-nanoimprinting equipment and integrated with adhesive-based polymeric microfluidics. The functioning of the SERS detection on-chip is confirmed and the effect of the polymer lid on the obtainable Raman spectra is analysed. Rhodamine 6G is used as a model analyte to demonstrate continuous flow measurements on a planar SERS substrate in a microchannel. The relation between the temporal response of the sensors and sample flow dynamics is studied with varied flow velocities, using SERS and fluorescence detection. The response time of the surface-dependent SERS signal is longer than the response time of the fluorescence signal of the bulk flow. This observation revealed the effect of convection on the temporal SERS responses at 25 μl/min to 1000 µl/min flow velocities. The diffusion of analyte molecules from the bulk concentration into the sensing surface induces about a 40-second lag time in the SERS detection. This lag time, and its rising trend with slower flow velocities, has to be taken into account in future trials of the optofluidic SERS sensor, with active analyte binding on the sensing surface.

  17. Dynamical structure of magnetized dissipative accretion flow around black holes

    NASA Astrophysics Data System (ADS)

    Sarkar, Biplob; Das, Santabrata

    2016-09-01

    We study the global structure of optically thin, advection dominated, magnetized accretion flow around black holes. We consider the magnetic field to be turbulent in nature and dominated by the toroidal component. With this, we obtain the complete set of accretion solutions for dissipative flows where bremsstrahlung process is regarded as the dominant cooling mechanism. We show that rotating magnetized accretion flow experiences virtual barrier around black hole due to centrifugal repulsion that can trigger the discontinuous transition of the flow variables in the form of shock waves. We examine the properties of the shock waves and find that the dynamics of the post-shock corona (PSC) is controlled by the flow parameters, namely viscosity, cooling rate and strength of the magnetic field, respectively. We separate the effective region of the parameter space for standing shock and observe that shock can form for wide range of flow parameters. We obtain the critical viscosity parameter that allows global accretion solutions including shocks. We estimate the energy dissipation at the PSC from where a part of the accreting matter can deflect as outflows and jets. We compare the maximum energy that could be extracted from the PSC and the observed radio luminosity values for several supermassive black hole sources and the observational implications of our present analysis are discussed.

  18. Fluid dynamic mechanisms and interactions within separated flows

    NASA Astrophysics Data System (ADS)

    Dutton, J. C.; Addy, A. L.

    1990-02-01

    The significant results of a joint research effort investigating the fundamental fluid dynamic mechanisms and interactions within high-speed separated flows are presented in detail. The results have obtained through analytical and numerical approaches, but with primary emphasis on experimental investigations of missile and projectile base flow-related configurations. The objectives of the research program focus on understanding the component mechanisms and interactions which establish and maintain high-speed separated flow regions. The analytical and numerical efforts have centered on unsteady plume-wall interactions in rocket launch tubes and on predictions of the effects of base bleed on transonic and supersonic base flowfields. The experimental efforts have considered the development and use of a state-of-the-art two component laser Doppler velocimeter (LDV) system for experiments with planar, two-dimensional, small-scale models in supersonic flows. The LDV experiments have yielded high quality, well documented mean and turbulence velocity data for a variety of high-speed separated flows including initial shear layer development, recompression/reattachment processes for two supersonic shear layers, oblique shock wave/turbulent boundary layer interactions in a compression corner, and two-stream, supersonic, near-wake flow behind a finite-thickness base.

  19. Dynamics of Laboratory Astrophysical Jets with Magnetized Helical Flows

    NASA Astrophysics Data System (ADS)

    von der Linden, Jens; You, Setthivoine

    2014-10-01

    A triple electrode planar plasma gun (MOCHI LabJet) designed to study the dynamics of magnetized helical flows in plasma jets provides boundary conditions and dimensionless numbers relevant to astrophysical jets. The goal is to observe the effect of current and flow profiles on the collimation and stability of jets to address the questions: why are jets collimated and long? How are jet irregularities related to plasma instabilities? The current and azimuthal flow profiles of the jets are tailored by biasing the electrodes at different potentials. High-speed camera images, high-resolution Ḃ probe measurements, and 3D vector tomography of plasma flows will map a stability space for varying current and flow profiles. An analytical stability space is derived with Newcomb's variational analysis applied to collimated magnetic flux tubes with skin and core currents. Two numerical stability spaces are also computed by integrating the Euler-Lagrange equation and applying a shooting method to the ideal MHD eigenvalue problem. The eigenvalue problem is generalized to include azimuthal flows and computed with a monotonicity condition for minimizing the required scanning of the complex eigenvalue space. This work was sponsored in part by the US DOE Grant DE-SC0010340.

  20. Validation of Computational Fluid Dynamics Simulations for Realistic Flows (Preprint)

    DTIC Science & Technology

    2007-12-01

    these calculations, the reference length is the vortex core radius, the reference flow conditions are the free stream conditions with the Mach number M...currently valid OMB control number . PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT DATE (DD-MM-YYYY) 2. REPORT TYPE 3. DATES COVERED...From - To) 11-10-2007 Technical Paper & Briefing Charts 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Validation of Computational Fluid Dynamics

  1. Laser Velocimetry Measurements of Oscillating Airfoil Dynamic Stall Flow Field

    DTIC Science & Technology

    1991-06-01

    Velocimetry Measurements of Oscillating Airfoil Dynamic Stall Flow Field By M.S.Chandrasekharal Navy-NASA Joint Institute of Aeronautics and Fluid Mechanics ...tunnel of the Fluid Mechanics Laboratory(FML) angle information. The other could be used for the at NASA Ames Research Center (ARC). It is one of...were on throat is always kept choked so that no disturbances a different traverse mechanism , but this was driven as can propagate upstream into the

  2. A simple delay model for two-phase flow dynamics

    SciTech Connect

    Clausse, A.; Delmastro, D.F.; Juanico`, L.E.

    1995-09-01

    A model based in delay equations for density-wave oscillations is presented. High Froude numbers and moderate ones were considered. The equations were numerically analyzed and compared with more sophisticated models. The influence of the gravity term was studied. Different kinds of behavior were found, particularly sub-critical and super-critical Hopf bifurcations. Moreover the present approach can be used to better understand the complicated dynamics of boiling flows systems.

  3. Diabetes augments in vivo microvascular blood flow dynamics after stroke.

    PubMed

    Tennant, Kelly A; Brown, Craig E

    2013-12-04

    Stroke usually affects people with underlying medical conditions. In particular, diabetics are significantly more likely to have a stroke and the prognosis for recovery is poor. Because diabetes is associated with degenerative changes in the vasculature of many organs, we sought to determine how hyperglycemia affects blood flow dynamics after an ischemic stroke. Longitudinal in vivo two-photon imaging was used to track microvessels before and after photothrombotic stroke in a diabetic mouse model. Chronic hyperglycemia exacerbated acute (3-7 d) ischemia-induced increases in blood flow velocity, vessel lumen diameter, and red blood cell flux in peri-infarct regions. These changes in blood flow dynamics were most evident in superficial blood vessels within 500 μm from the infarct, rather than deeper or more distant cortical regions. Long-term imaging of diabetic mice not subjected to stroke indicated that these acute stroke-related changes in vascular function could not be attributed to complications from hyperglycemia alone. Treating diabetic mice with insulin immediately after stroke resulted in less severe alterations in blood flow within the first 7 d of recovery, but had more variable results at later time points. Analysis of microvessel branching patterns revealed that stroke led to a pruning of microvessels in peri-infarct cortex, with very few instances of sprouting. These results indicate that chronic hyperglycemia significantly affects the vascular response to ischemic stroke and that insulin only partially mitigates these changes. The combination of these acute and chronic alterations in blood flow dynamics could underlie diabetes-related deficits in cortical plasticity and stroke recovery.

  4. Calculational investigation of impact cratering dynamics - Early time material motions

    NASA Technical Reports Server (NTRS)

    Thomsen, J. M.; Austin, M. G.; Ruhl, S. F.; Schultz, P. H.; Orphal, D. L.

    1979-01-01

    Early time two-dimensional finite difference calculations of laboratory-scale hypervelocity (6 km/sec) impact of 0.3 g spherical 2024 aluminum projectiles into homogeneous plasticene clay targets were performed and the resulting material motions analyzed. Results show that the initial jetting of vaporized target material is qualitatively similar to experimental observation. The velocity flow field developed within the target is shown to have features quite similar to those found in calculations of near-surface explosion cratering. Specific application of Maxwell's analytic Z-Model (developed to interpret the flow fields of near-surface explosion cratering calculations), shows that this model can be used to describe the flow fields resulting from the impact cratering calculations, provided that the flow field center is located beneath the target surface, and that application of the model is made late enough in time that most of the projectile momentum has been dissipated.

  5. Hydro-dynamic damping theory in flowing water

    NASA Astrophysics Data System (ADS)

    Monette, C.; Nennemann, B.; Seeley, C.; Coutu, A.; Marmont, H.

    2014-03-01

    Fluid-structure interaction (FSI) has a major impact on the dynamic response of the structural components of hydroelectric turbines. On mid-head to high-head Francis runners, the rotor-stator interaction (RSI) phenomenon always has to be considered carefully during the design phase to avoid operational issues later on. The RSI dynamic response amplitudes are driven by three main factors: (1) pressure forcing amplitudes, (2) excitation frequencies in relation to natural frequencies and (3) damping. The prediction of the two first factors has been largely documented in the literature. However, the prediction of fluid damping has received less attention in spite of being critical when the runner is close to resonance. Experimental damping measurements in flowing water on hydrofoils were presented previously. Those results showed that the hydro-dynamic damping increased linearly with the flow. This paper presents development and validation of a mathematical model, based on momentum exchange, to predict damping due to fluid structure interaction in flowing water. The model is implemented as an analytical procedure for simple structures, such as cantilever beams, but is also implemented in more general ways using three different approaches for more complex structures such as runner blades: a finite element procedure, a CFD modal work based approach and a CFD 1DOF approach. The mathematical model and all three implementation approaches are shown to agree well with experimental results.

  6. Dynamic modes of red blood cells in oscillatory shear flow.

    PubMed

    Noguchi, Hiroshi

    2010-06-01

    The dynamics of red blood cells (RBCs) in oscillatory shear flow was studied using differential equations of three variables: a shape parameter, the inclination angle θ, and phase angle ϕ of the membrane rotation. In steady shear flow, three types of dynamics occur depending on the shear rate and viscosity ratio. (i) tank-treading (TT): ϕ rotates while the shape and θ oscillate. (ii) tumbling (TB): θ rotates while the shape and ϕ oscillate. (iii) intermediate motion: both ϕ and θ rotate synchronously or intermittently. In oscillatory shear flow, RBCs show various dynamics based on these three motions. For a low shear frequency with zero mean shear rate, a limit-cycle oscillation occurs, based on the TT or TB rotation at a high or low shear amplitude, respectively. This TT-based oscillation well explains recent experiments. In the middle shear amplitude, RBCs show an intermittent or synchronized oscillation. As shear frequency increases, the vesicle oscillation becomes delayed with respect to the shear oscillation. At a high frequency, multiple limit-cycle oscillations coexist. The thermal fluctuations can induce transitions between two orbits at very low shear amplitudes. For a high mean shear rate with small shear oscillation, the shape and θ oscillate in the TT motion but only one attractor exists even at high shear frequencies. The measurement of these oscillatory modes is a promising tool for quantifying the viscoelasticity of RBCs, synthetic capsules, and lipid vesicles.

  7. Dynamic modes of red blood cells in oscillatory shear flow

    NASA Astrophysics Data System (ADS)

    Noguchi, Hiroshi

    2010-06-01

    The dynamics of red blood cells (RBCs) in oscillatory shear flow was studied using differential equations of three variables: a shape parameter, the inclination angle θ , and phase angle ϕ of the membrane rotation. In steady shear flow, three types of dynamics occur depending on the shear rate and viscosity ratio. (i) tank-treading (TT): ϕ rotates while the shape and θ oscillate. (ii) tumbling (TB): θ rotates while the shape and ϕ oscillate. (iii) intermediate motion: both ϕ and θ rotate synchronously or intermittently. In oscillatory shear flow, RBCs show various dynamics based on these three motions. For a low shear frequency with zero mean shear rate, a limit-cycle oscillation occurs, based on the TT or TB rotation at a high or low shear amplitude, respectively. This TT-based oscillation well explains recent experiments. In the middle shear amplitude, RBCs show an intermittent or synchronized oscillation. As shear frequency increases, the vesicle oscillation becomes delayed with respect to the shear oscillation. At a high frequency, multiple limit-cycle oscillations coexist. The thermal fluctuations can induce transitions between two orbits at very low shear amplitudes. For a high mean shear rate with small shear oscillation, the shape and θ oscillate in the TT motion but only one attractor exists even at high shear frequencies. The measurement of these oscillatory modes is a promising tool for quantifying the viscoelasticity of RBCs, synthetic capsules, and lipid vesicles.

  8. Distortion and flow of nematics simulated by dissipative particle dynamics.

    PubMed

    Zhao, Tongyang; Wang, Xiaogong

    2014-05-14

    In this study, we simulated distortion and flow of nematics by dissipative particle dynamics (DPD). The nematics were modeled by a binary mixture that contained rigid rods composed of DPD particles as mesogenic units and normal DPD particles as solvent. Elastic distortions were investigated by monitoring director orientation in space under influences of boundary anchoring and external fields. Static distortion demonstrated by the simulation is consistent with the prediction of Frank elastic theory. Spatial distortion profile of the director was examined to obtain static elastic constants. Rotational motions of the director under influence of the external field were simulated to understand the dynamic process. The rules revealed by the simulation are in a good agreement with those obtained from dynamical experiments and classical theories for nematics. Three Miesowicz viscosities were obtained by using external fields to hold the orientation of the rods in shear flows. The simulation showed that the Miesowicz viscosities have the order of ηc > ηa > ηb and the rotational viscosity γ1 is about two orders larger than the Miesowicz viscosity ηb. The DPD simulation correctly reproduced the non-monotonic concentration dependence of viscosity, which is a unique property of lyotropic nematic fluids. By comparing simulation results with classical theories for nematics and experiments, the DPD nematic fluids are proved to be a valid model to investigate the distortion and flow of lyotropic nematics.

  9. A note on the theory of fast money flow dynamics

    NASA Astrophysics Data System (ADS)

    Sokolov, A.; Kieu, T.; Melatos, A.

    2010-08-01

    The gauge theory of arbitrage was introduced by Ilinski in [K. Ilinski, preprint arXiv:hep-th/9710148 (1997)] and applied to fast money flows in [A. Ilinskaia, K. Ilinski, preprint arXiv:cond-mat/9902044 (1999); K. Ilinski, Physics of finance: gauge modelling in non-equilibrium pricing (Wiley, 2001)]. The theory of fast money flow dynamics attempts to model the evolution of currency exchange rates and stock prices on short, e.g. intra-day, time scales. It has been used to explain some of the heuristic trading rules, known as technical analysis, that are used by professional traders in the equity and foreign exchange markets. A critique of some of the underlying assumptions of the gauge theory of arbitrage was presented by Sornette in [D. Sornette, Int. J. Mod. Phys. C 9, 505 (1998)]. In this paper, we present a critique of the theory of fast money flow dynamics, which was not examined by Sornette. We demonstrate that the choice of the input parameters used in [K. Ilinski, Physics of finance: gauge modelling in non-equilibrium pricing (Wiley, 2001)] results in sinusoidal oscillations of the exchange rate, in conflict with the results presented in [K. Ilinski, Physics of finance: gauge modelling in non-equilibrium pricing (Wiley, 2001)]. We also find that the dynamics predicted by the theory are generally unstable in most realistic situations, with the exchange rate tending to zero or infinity exponentially.

  10. Flow Dynamics of Contrast Dispersion in the Aorta

    NASA Astrophysics Data System (ADS)

    Eslami, Parastou; Seo, Jung-Hee; Chen, Marcus; Mittal, Rajat

    2016-11-01

    The time profile of the contrast concentration or arterial input function (AIF) has many fundamental clinical implications and is of importance for many imaging modalities and diagnosis such as MR perfusion, CT perfusion and CT angiography (CTA). Contrast dispersion in CTA has been utilized to develop a novel method- Transluminal Attenuation Flow Encoding (TAFE)- to estimate coronary blood flow (CBF). However, in clinical practice, AIF is only available in the descending aorta and is used as a surrogate of the AIF at the coronary ostium. In this work we use patient specific computational models of the complete aorta to investigate the fluid dynamics of contrast dispersion in the aorta. The simulation employs a realistic kinematic model of the aortic valve and the dispersion patterns are correlated with the complex dynamics of the pulsatile flow in the curved aorta. The simulations allow us to determine the implications of using the descending aorta AIF as a surrogate for the AIF at the coronary ostium. PE is supported by the NIH Individual Partnership Program. -/abstract- Category: 4.7.1: Biological fluid dynamics: Physiological - Cardiovasc This work was done at Johns Hopkins University.

  11. Flow path and travel time dynamics in a lowland catchment.

    NASA Astrophysics Data System (ADS)

    van der Velde, Ype; de Rooij, Gerrit

    2016-04-01

    The distribution of time it takes water from the moment of precipitation to reach the catchment outlet is widely used as a characteristic for catchment flow path contributions, catchment vulnerability to pollution spreading and pollutant loads from catchments to downstream waters. However, this distribution tends to vary in time driven by variability in precipitation and evapotranspiration. Catchment scale mixing of water controls how dynamics in rainfall and evapotranspiration are translated into dynamics of travel time distributions. In this presentation we use the concept of StorAge selection (SAS) functions, that quantify catchment scale mixing of water, to describe chloride and nitrate flow. We will show how SAS functions relate to the topography and subsurface and how they are effective in describing nitrate and chloride transport. The presented analyses will combine unique datasets of high-frequency discharge and water quality concentrations with conceptual models of water flow and solute transport. Remarkable findings are the large contrasts in travel times between lowland and sloping catchments and the strong relationship between evapotranspiration and stream water nutrient concentration dynamics.

  12. Dynamics of vorticity defects in layered stratified shear flows

    NASA Astrophysics Data System (ADS)

    Caulfield, C. P.; Roy, A.; Balmforth, N. J.

    2011-11-01

    Layered stratified flows, where relatively deep regions of weak stratification are separated by thinner interfacial layers of substantially stronger density gradient are commonly observed in nature. If such flows are subjected to vertical shear, it is well-known that a wide range of qualitatively different instabilities may develop. For example, the three-layer, two interface case is susceptible to a ``Taylor'' instability which, although superficially similar to the classic Kelvin-Helmholtz instability, is actually qualitatively different in its growth mechanism. The investigation of the nonlinear dynamics of this instability, and to a lesser extent the single-interface ``Holmboe'' instability, has proved difficult, as the need to resolve the associated sharp density gradients places heavy demands on the required numerical resolutions for simulation. However, we show that it is possible to gain insight into the key nonlinear dynamics of such layered stratified shear flows by generalizing a reduced matched asymptotic ``vorticity defect'' model (N. J. Balmforth et al. J. Fluid Mech. 333, 197 [1997]) to include the dynamical effects of density variations. We particularly focus on investigating the finite amplitude structure of the saturated primary Taylor instability, and the properties of the secondary instabilities to which Taylor and Holmboe instabilities are susceptible.

  13. The dynamics of semiflexible actin filaments in simple shear flow

    NASA Astrophysics Data System (ADS)

    Liu, Yanan; Lindner, Anke; Du Roure, Olivia

    2016-11-01

    The rheological properties of complex fluids made of particles in a suspended fluid depend on the behavior of microscopic particles in flow. A first step to understand this link is to investigate the individual particle dynamics in simple shear flows. A rigid rod will perform so-called Jeffery orbits, however when the rod becomes flexible and Brownian, the behavior in terms of deformation and migration is still to be fully understood. We chose here to address this situation by studying experimentally the behavior of semiflexible polymers. We use actin filaments and combine fluorescent labeling techniques, microfluidic devices to carry out controlled systematical experiments. Different dynamics are observed as a function of the elasto-viscous number, comparing viscous forces to elastic restoring forces ζ = (8 πηγ˙L4) / (LpkB T) . The bending modulus of the actin filaments is given by its persistence length Lp = 17 +/- 1 μm . When increasing the elasto-visous number we subsequently observe tumbling, buckling, and bending under flow. Those observations seem to be in good agreement with recent numerical simulations. At the same time, actin filaments fluctuate due to Brownian motion and these fluctuations can modify the individual dynamics of actin filaments. ERC PaDy No.682367.

  14. Diode laser absorption sensors for gas-dynamic and combustion flows.

    PubMed

    Allen, M G

    1998-04-01

    Recent advances in room-temperature, near-IR and visible diode laser sources for tele-communication, high-speed computer networks, and optical data storage applications are enabling a new generation of gas-dynamic and combustion-flow sensors based on laser absorption spectroscopy. In addition to conventional species concentration and density measurements, spectroscopic techniques for temperature, velocity, pressure and mass flux have been demonstrated in laboratory, industrial and technical flows. Combined with fibreoptic distribution networks and ultrasensitive detection strategies, compact and portable sensors are now appearing for a variety of applications. In many cases, the superior spectroscopic quality of the new laser sources compared with earlier cryogenic, mid-IR devices is allowing increased sensitivity of trace species measurements, high-precision spectroscopy of major gas constituents, and stable, autonomous measurement systems. The purpose of this article is to review recent progress in this field and suggest likely directions for future research and development. The various laser-source technologies are briefly reviewed as they relate to sensor applications. Basic theory for laser absorption measurements of gas-dynamic properties is reviewed and special detection strategies for the weak near-IR and visible absorption spectra are described. Typical sensor configurations are described and compared for various application scenarios, ranging from laboratory research to automated field and airborne packages. Recent applications of gas-dynamic sensors for air flows and fluxes of trace atmospheric species are presented. Applications of gas-dynamic and combustion sensors to research and development of high-speed flows aeropropulsion engines, and combustion emissions monitoring are presented in detail, along with emerging flow control systems based on these new sensors. Finally, technology in nonlinear frequency conversion, UV laser materials, room

  15. Diode laser absorption sensors for gas-dynamic and combustion flows

    NASA Technical Reports Server (NTRS)

    Allen, M. G.

    1998-01-01

    Recent advances in room-temperature, near-IR and visible diode laser sources for tele-communication, high-speed computer networks, and optical data storage applications are enabling a new generation of gas-dynamic and combustion-flow sensors based on laser absorption spectroscopy. In addition to conventional species concentration and density measurements, spectroscopic techniques for temperature, velocity, pressure and mass flux have been demonstrated in laboratory, industrial and technical flows. Combined with fibreoptic distribution networks and ultrasensitive detection strategies, compact and portable sensors are now appearing for a variety of applications. In many cases, the superior spectroscopic quality of the new laser sources compared with earlier cryogenic, mid-IR devices is allowing increased sensitivity of trace species measurements, high-precision spectroscopy of major gas constituents, and stable, autonomous measurement systems. The purpose of this article is to review recent progress in this field and suggest likely directions for future research and development. The various laser-source technologies are briefly reviewed as they relate to sensor applications. Basic theory for laser absorption measurements of gas-dynamic properties is reviewed and special detection strategies for the weak near-IR and visible absorption spectra are described. Typical sensor configurations are described and compared for various application scenarios, ranging from laboratory research to automated field and airborne packages. Recent applications of gas-dynamic sensors for air flows and fluxes of trace atmospheric species are presented. Applications of gas-dynamic and combustion sensors to research and development of high-speed flows aeropropulsion engines, and combustion emissions monitoring are presented in detail, along with emerging flow control systems based on these new sensors. Finally, technology in nonlinear frequency conversion, UV laser materials, room

  16. Diode laser absorption sensors for gas-dynamic and combustion flows

    NASA Technical Reports Server (NTRS)

    Allen, M. G.

    1998-01-01

    Recent advances in room-temperature, near-IR and visible diode laser sources for tele-communication, high-speed computer networks, and optical data storage applications are enabling a new generation of gas-dynamic and combustion-flow sensors based on laser absorption spectroscopy. In addition to conventional species concentration and density measurements, spectroscopic techniques for temperature, velocity, pressure and mass flux have been demonstrated in laboratory, industrial and technical flows. Combined with fibreoptic distribution networks and ultrasensitive detection strategies, compact and portable sensors are now appearing for a variety of applications. In many cases, the superior spectroscopic quality of the new laser sources compared with earlier cryogenic, mid-IR devices is allowing increased sensitivity of trace species measurements, high-precision spectroscopy of major gas constituents, and stable, autonomous measurement systems. The purpose of this article is to review recent progress in this field and suggest likely directions for future research and development. The various laser-source technologies are briefly reviewed as they relate to sensor applications. Basic theory for laser absorption measurements of gas-dynamic properties is reviewed and special detection strategies for the weak near-IR and visible absorption spectra are described. Typical sensor configurations are described and compared for various application scenarios, ranging from laboratory research to automated field and airborne packages. Recent applications of gas-dynamic sensors for air flows and fluxes of trace atmospheric species are presented. Applications of gas-dynamic and combustion sensors to research and development of high-speed flows aeropropulsion engines, and combustion emissions monitoring are presented in detail, along with emerging flow control systems based on these new sensors. Finally, technology in nonlinear frequency conversion, UV laser materials, room

  17. Dynamic continuum pedestrian flow model with memory effect.

    PubMed

    Xia, Yinhua; Wong, S C; Shu, Chi-Wang

    2009-06-01

    In this paper, we develop a macroscopic model for pedestrian flow using the dynamic continuum modeling approach. We consider a two-dimensional walking facility that is represented as a continuum within which pedestrians can move freely in any direction. A pedestrian chooses a route based on his or her memory of the shortest path to the desired destination when the facility is empty and, at the same time, tries to avoid high densities. In this model, pedestrian flow is governed by a two-dimensional conservation law, and a general speed-flow-density relationship is considered. The model equation is solved numerically using the discontinuous Galerkin method, and a numerical example is employed to demonstrate both the model and the effectiveness of the numerical method.

  18. Drops subjected to surface acoustic waves: flow dynamics

    NASA Astrophysics Data System (ADS)

    Brunet, Philippe; Baudoin, Michael; Bou Matar, Olivier; Dynamique Des Systèmes Hors Equilibre Team; Aiman-Films Team

    2012-11-01

    Ultrasonic acoustic waves of frequency beyond the MHz are known to induce streaming flow in fluids that can be suitable to perform elementary operations in microfluidics systems. One of the currently appealing geometry is that of a sessile drop subjected to surface acoustic waves (SAW). Such Rayleigh waves produce non-trival actuation in the drop leading to internal flow, drop displacement, free-surface oscillations and atomization. We recently carried out experiments and numerical simulations that allowed to better understand the underlying physical mechanisms that couple acoustic propagation and fluid actuation. We varied the frequency and amplitude of actuation, as well as the properties of the fluid, and we measured the effects of these parameters on the dynamics of the flow. We compared these results to finite-elements numerical simulations.

  19. Fluid dynamics of unsteady separated flow. II - Lifting surfaces

    NASA Technical Reports Server (NTRS)

    Ericsson, L. E.; Reding, J. P.

    1987-01-01

    An analytic method is described which uses static experimental data to predict the separated flow effect on rigid and elastic vehicle dynamics. Key parameters in the analytic relationship between steady and nonsteady aerodynamics are: the time lag occurring before a change of flow conditions can affect the separation-induced aerodynamic loads; the accelerated flow effect (i.e., the pressure gradient lag relative to the static aerodynamic characteristics); and the moving wall effect (i.e., the effect of the nonsteady boundary condition at the vehicle surface). Using the existing experimental data base, an analytic theory is formulated that can predict the separation-induced unsteady aerodynamics if the static characteristics are known from theory or experiment. Reference is made to increased-maneuverability advanced aircraft and to Space Shuttle Orbiter aerodynamics.

  20. Flow dynamics of dacite lava flow - AMS, microstructure and porosity case study

    NASA Astrophysics Data System (ADS)

    Závada, Prokop; Kusbach, Vladimír; Machek, Matěj; Staněk, Martin; Špičák, Aleš

    2017-04-01

    Pyroclastic flows derived from flow frontal collapse of highly viscous "block lavas" formed by andesite or dacite belong to the most serious volcano-related hazards for surrounding populations. The threat results from abrupt transition of lava flow from ductile flow to gravitational failure of the front, which exposes their overpressurized interior and triggers devastating pyroclastic flows. The goal of the study is to quantify the microfabrics and dynamic porosity in a lava flow to constrain the cavitation process (development and coalescence of dynamic porosity). Pleistocene dacite flow body situated on the slope of Middle Sister Volcano (OR, USA) was studied by means of field-based structural analysis, anisotropy of magnetic susceptibility (AMS), microstructural analysis and mercury injection porosimetry (MIP). The 500 m exposure of the flow is associated with a vertical feeding dyke at the beginning of the flow, 40 m upslope. The flow shows occasional layers, 5-15 cm thick, marked by evenly spaced and up to 10 cm long, lenticular to sigmoidal cracks often developed in the vicinity of the clasts/phenocrysts. These cracks frequently dip against the slope of the flow and show 15-50° difference with the layering. At the feeding dyke, highly oblate magnetic fabric shows subvertical foliations with horizontal lineations oriented parallel to the dyke walls. Middle part of the flow revealed highly prolate fabrics with subhorizontal magnetic foliations and lineations parallel to the flow direction. At the downslope limit of the flow, magnetic foliations are perpendicular to the flow direction. The dynamic porosity was studied in detail on larger sample from the central part of the flow. The sample contains three layers with different density of porosity and average crack length. All the cracks were oriented about 45° to the layer boundaries and alignment of the groundmass crystals. MIP data revealed total connected porosities between 11 and 15 %. Throat

  1. Flow Transformation in Pyroclastic Density Currents: Entrainment and Granular Dynamics during the 2006 eruption of Tungurahua

    NASA Astrophysics Data System (ADS)

    Dufek, J.; Benage, M. C.; Geist, D.; Harpp, K. S.

    2013-12-01

    Pyroclastic density currents are ground hugging flows composed of hot gases, fragments of juvenile magmatic material, and entrained clasts from the conduit or the edifice over which the flows have traveled. The interior of these flows are opaque to observation due to their large ash content, but recent investigations have highlighted that there are likely strong gradients in particle concentration and segregation of particle sizes in these particle-laden gravity currents. Pyroclastic density currents refer to a broad range of phenomena from dense flows in which the dynamics are dominated by frictional interaction between particles (dense granular flows), to gas fluidized flows, to dilute flows dominated by particle-gas turbulent interaction. However, abrupt flow transformation (e.g. from dense to dilute pyroclastic density currents) can arise due to energy exchange across multiple length scales and phases, and understanding these flow transformations is important in delineating the entrainment and erosion history of these flows, interpretations of their deposits, and in better understanding the hazards they present. During the 2006 eruption of Tungurahua, Ecuador numerous, dense pyroclastic density currents descended the volcano as result of boiling-over or low column collapse eruptions. The deposits of these flows typically have pronounced snouts and levees, and are often dominated by large, clasts (meter scale in some locations). There is an exceptional observational record of these flows and their deposits, permitting detailed field constraints of their dynamics. A particularly interesting set of flows occurred on Aug. 17, 2006 during the paroxysmal phase of the eruption that descended the slope of the volcano, filled in the river channel of the Chambo river, removing much of the larger clasts from the flow, and resulting in a dilute ';surge' that transported finer material across the channel and uphill forming dune features on the opposite bank of the river. We

  2. Dynamics of temporal variations in phonatory flow1

    PubMed Central

    Krane, Michael H.; Barry, Michael; Wei, Timothy

    2010-01-01

    This paper addresses the dynamic relevance of time variations of phonatory airflow, commonly neglected under the quasisteady phonatory flow assumption. In contrast to previous efforts, which relied on direct measurement of glottal impedance, this work uses spatially and temporally resolved measurements of the velocity field to estimate the unsteady and convective acceleration terms in the unsteady Bernoulli equation. Theoretical considerations suggest that phonatory flow is inherently unsteady when two related conditions apply: (1) that the unsteady and convective accelerations are commensurate, and (2) that the inertia of the glottal jet is non-negligible. Acceleration waveforms, computed from experimental data, show that unsteady and convective accelerations to be the same order of magnitude, throughout the cycle, and that the jet flow contributes significantly to the unsteady acceleration. In the middle of the cycle, however, jet inertia is negligible because the convective and unsteady accelerations nearly offset one another in the jet region. These results, consistent with previous findings treating quasisteady phonatory flow, emphasize that unsteady acceleration cannot be neglected during the final stages of the phonation cycle, during which voice sound power and spectral content are largely determined. Furthermore, glottal jet dynamics must be included in any model of phonatory airflow. PMID:20649231

  3. Slow dynamics at Re =108 in turbulent Helium flows

    NASA Astrophysics Data System (ADS)

    Burguete, Javier; Roche, Philippe; Rousset, Bernard

    2014-11-01

    The presence of slow dynamics is a recurrent feature of many turbulent flows. This behaviour can be created by instabilities of the mean flow or by other mechanisms. In this work we analyze the behavior of a highly turbulent flow (maximum Reynolds number Re =108 , with a Reynolds based on the Taylor microscale Reλ = 2000). The experimental cell consists on a closed cavity filled with liquid Helium (330 liters) close to the lambda point (between 1.8 and 2.5 K) where two inhomogeneous and strongly turbulent flows collide in a thin region. The cylindrical cavity has a diameter of 78cm and two impellers rotate in opposite directions with rotation frequencies up to 2 Hz. The distance between the propellers is 70 cm. Different experimental runs have been performed, both in the normal and superfluid phases. We have performed velocity measurements using home-made Pitot tubes. Here we would like to present preliminary results on this configuration. The analysis of the data series reveals that below the injection frequencies there are different dynamical regimes with time scales two orders of magnitude below the injection scale. We acknowledge support from the EuHIT network and the SHREK Collaboration.

  4. Dynamic Mode Decomposition Bio-Markers for Left Ventricle Flow

    NASA Astrophysics Data System (ADS)

    Borja, Maria; Martinez-Legazpi, Pablo; Benito, Yolanda; Yotti, Raquel; Fernandez-Aviles, Francisco; Bermejo, Javier; Del Alamo, Juan C.

    2016-11-01

    Dynamic mode decomposition (DMD) is a tool used in the fluid community to extract a set of modes that describe the underling fluid dynamics in a set of flow fields generated experimentally or by numerical simulations. Despite advances in medical imaging, characterization of some cardiac dysfunctions has remained a challenge and diagnosis is often subjective. This study presents a novel DMD method to objectively characterize left ventricular (LV) flow in healthy volunteers and patients with dilated cardiomyopathy (DCM) and hypertrophic cardiomyopathy (HCM). Our approach is based on assessing temporal evolution dependent mode structures from two-dimensional velocity fields, obtained experimentally using echocardiographic color Doppler velocimetry, and defined with a common unit normal moving LV coordinate system. Using the mode structures as a basis, we reconstruct the flow field, determine the key contributing modes, and obtain a reduce order model. Using 20 healthy volunteers, 20 DCM patients and 20 HCM patients, our results show quantitative and qualitative differences between healthy and in the DCM and HCM patients. This study suggests that temporal evolution dependent modes can be used as bio-markers to asses in-vivo LV flow.

  5. Nonlinear dynamics in eccentric Taylor-Couette-Poiseuille flow

    NASA Astrophysics Data System (ADS)

    Pier, Benoît; Caulfield, C. P.

    2015-11-01

    The flow in the gap between two parallel but eccentric cylinders and driven by an axial pressure gradient and inner cylinder rotation is characterized by two geometrical parameters (radius ratio and eccentricity) and two dynamic parameters (axial and azimuthal Reynolds numbers). Such a theoretical configuration is a model for the flow between drill string and wellbore in the hydrocarbon drilling industry. The linear convective and absolute instability properties have been systematically derived in a recent study [Leclercq, Pier & Scott, J. Fluid Mech. 2013 and 2014]. Here we address the nonlinear dynamics resulting after saturation of exponentially growing small-amplitude perturbations. By using direct numerical simulations, a range of finite-amplitude states are found and characterized: nonlinear traveling waves (an eccentric counterpart of Taylor vortices, associated with constant hydrodynamic loading on the inner cylinder), modulated nonlinear waves (with time-periodic torque and flow rate) and more irregular states. In the nonlinear regime, the hydrodynamic forces are found to depart significantly from those prevailing for the base flow, even in situations of weak linear instability.

  6. Dynamics of model blood cells in shear flow

    NASA Astrophysics Data System (ADS)

    Podgorski, Thomas; Callens, Natacha; Minetti, Christophe; Coupier, Gwennou; Dubois, Frank; Misbah, Chaouqi

    The dynamics of a vesicle suspension in shear flow was investigated by digital holographic microscopy [1] in parabolic flights and in the MASER 11 sounding rocket. Vesicles are lipid membranes which mimic the mechanical behaviour of cells, such as red blood cells in flow. In a simple shear flow between parallel walls, a lift force of purely viscous origin pushes vesicles away from walls. Our parabolic flight experiments [2] reveal that the lift velocity in a dilute suspen-sion is well described by theoretical predictions by Olla. As vesicles gather near the center of the flow chamber due to lift forces from both walls, one expects hydrodynamic interactions of pairs of vesicles to result in shear induced diffusion in the suspension. The BIOMICS experi-ment in the MASER 11 sounding rocket revealed a complex spatial structure of a polydisperse vesicle suspension due to the interplay between lift forces from the walls and hydrodynamic interactions. These phenomena have a strong impact on the structure and rheology of blood in small vessels, and a precise knowledge of the dynamics of migration and diffusion of soft particles in flow can lead to alternative ways to separate and sort blood cells. 1. Dubois, F., Schockaert, C., Callens, N., Yourrassowsky, C., "Focus plane detection criteria in digital holography microscopy by amplitude analysis", Opt. Express, Vol. 14, pp 5895-5908, 2006 2. Callens, N., Minetti, C., Coupier, G., Mader, M.-A., Dubois, F., Misbah, C., Podgorski, T., "Hydrodynamics lift of vesicles under shear flow in microgravity", Europhys. Lett., Vol. 83, p. 24002, 2008

  7. Studies of shock induced flows in strengthless materials on Pegasus

    SciTech Connect

    Oro, D.M.; Fulton, R.D.; Stokes, J.; Guzik, J.A.; Adams, P.J.; Morgan, D.; Platts, D.; Obst, A.W.; Fell, M.

    1998-12-31

    Experiments on the Pegasus II pulsed power facility at Los Alamos are being conducted to study the evolution and flow of strengthless materials as a result of being shocked. Of particular interest is vorticity and mixing that is induced in the materials by a shock-wave passing through a non-uniform boundary. The experiments provide an important benchmark for hydrodynamic codes, and are a precursor to experiments planned on Atlas in which the materials will be pre-ionized before being shocked. For these experiments, flash radiography is used to image the position of the target boundaries at specific times. In these experiments 3 radiographs along target radii and 2 radiographs along the target axis are taken at independent times. The central cavity of the target is imaged with visible framing cameras. The Xe in this cavity radiates when shocked, and therefore the shape and timing of the shock front in the Xe can be determined from the images. Other diagnostics employed for this work include electric and magnetic field probes that are used to determine the current through the liner and when the liner impacts the target. Both the 1-d magnetohydrodynamics code RAVEN, and the 2-d/3-d adaptive grid eulerian code RAGE are used for pre-shot calculations. In this talk the authors will discuss the motivation for these experiments, compare calculations with radiographs and visible images and discuss future experiments on Pegasus and Atlas.

  8. Enhanced transport of materials into enamel nanopores via electrokinetic flow.

    PubMed

    Gan, H Y; Sousa, F B; Carlo, H L; Maciel, P P; Macena, M S; Han, J

    2015-04-01

    The ability to infiltrate various molecules and resins into dental enamel is highly desirable in dentistry, yet transporting materials into dental enamel is limited by the nanometric scale of their pores. Materials that cannot be infiltrated into enamel by diffusion/capillarity are often considered molecules with sizes above a critical threshold, which are often considered to be larger than the pores of enamel. We challenge this notion by reporting the use of electrokinetic flow to transport solutions with molecules with sizes above a critical threshold-namely, an aqueous solution with a high refractive index (Thoulet's solution) and a curable fluid resin infiltrant (without acid etching)-deep into the normal enamel layer. Volume infiltration by Thoulet's solution is increased by 5- to 6-fold, and resin infiltration depths as large as 600 to 2,000 µm were achieved, in contrast to ~10 µm resulting from diffusion/capillarity. Incubation with demineralization solution for 192 h resulted in significant demineralization at noninfiltrated histologic points but not at resin infiltrated. These results open new avenues for the transport of materials in dental enamel.

  9. Calculational investigation of impact cratering dynamics - Material motions during the crater growth period

    NASA Technical Reports Server (NTRS)

    Austin, M. G.; Thomsen, J. M.; Ruhl, S. F.; Orphal, D. L.; Schultz, P. H.

    1980-01-01

    The considered investigation was conducted in connection with studies which are to provide a better understanding of the detailed dynamics of impact cratering processes. Such an understanding is vital for a comprehension of planetary surfaces. The investigation is the continuation of a study of impact dynamics in a uniform, nongeologic material at impact velocities achievable in laboratory-scale experiments conducted by Thomsen et al. (1979). A calculation of a 6 km/sec impact of a 0.3 g spherical 2024 aluminum projectile into low strength (50 kPa) homogeneous plasticene clay has been continued from 18 microseconds to past 600 microseconds. The cratering flow field, defined as the material flow field in the target beyond the transient cavity but well behind the outgoing shock wave, has been analyzed in detail to see how applicable the Maxwell Z-Model, developed from analysis of near-surface explosion cratering calculations, is to impact cratering

  10. Calculational investigation of impact cratering dynamics - Material motions during the crater growth period

    NASA Technical Reports Server (NTRS)

    Austin, M. G.; Thomsen, J. M.; Ruhl, S. F.; Orphal, D. L.; Schultz, P. H.

    1980-01-01

    The considered investigation was conducted in connection with studies which are to provide a better understanding of the detailed dynamics of impact cratering processes. Such an understanding is vital for a comprehension of planetary surfaces. The investigation is the continuation of a study of impact dynamics in a uniform, nongeologic material at impact velocities achievable in laboratory-scale experiments conducted by Thomsen et al. (1979). A calculation of a 6 km/sec impact of a 0.3 g spherical 2024 aluminum projectile into low strength (50 kPa) homogeneous plasticene clay has been continued from 18 microseconds to past 600 microseconds. The cratering flow field, defined as the material flow field in the target beyond the transient cavity but well behind the outgoing shock wave, has been analyzed in detail to see how applicable the Maxwell Z-Model, developed from analysis of near-surface explosion cratering calculations, is to impact cratering

  11. A restricted nonlinear-dynamics model for turbulent channel flows

    NASA Astrophysics Data System (ADS)

    Lozano-Durán, Adrián; Jiménez, Javier; Farrell, Brian F.; Ioannou, Petros J.; Nikolaidis, Marios A.; Constantinou, Navid C.

    2014-11-01

    The dynamics of the formation of very-large scale structure in turbulent plane Poiseuille flow is studied by restricting the nonlinearity in the Navier-Stokes (NS) equations to interactions between the streamwise-averaged flow and perturbations. Using comparisons with DNS, we show that this restricted nonlinear dynamics (RNL) supports essentially realistic turbulence at Reτ = 900 , despite the naturally occurring severe reduction in the set of streamwise wavenumbers supporting the turbulence. Using statistical diagnostics we verify that there are similar self-sustaining processes (SSP) underlying turbulence in the RNL and in the NS dynamics, separate manifestations of which operate in the buffer and outer layers. In the buffer layer, the SSP supports the familiar roll-streak mechanism of wall-bounded turbulence, while the outer-layer streaks in the RNL are probably the streamwise elongated structures referred to as VLSI. It is argued that the formation of the roll-streak structure is a universal mechanism that can be fruitfully studied in the minimal dynamics of RNL. Funded by Multiflow project of the ERC, Navid Constantinou acknowledges the support of the Alexander S. Onassis Public Benefit Foundation. Brian Farrell was supported by NSF AGS-1246929.

  12. Flow dynamics and energy efficiency of flow in the left ventricle during myocardial infarction.

    PubMed

    Vasudevan, Vivek; Low, Adriel Jia Jun; Annamalai, Sarayu Parimal; Sampath, Smita; Poh, Kian Keong; Totman, Teresa; Mazlan, Muhammad; Croft, Grace; Richards, A Mark; de Kleijn, Dominique P V; Chin, Chih-Liang; Yap, Choon Hwai

    2017-03-31

    Cardiovascular disease is a leading cause of death worldwide, where myocardial infarction (MI) is a major category. After infarction, the heart has difficulty providing sufficient energy for circulation, and thus, understanding the heart's energy efficiency is important. We induced MI in a porcine animal model via circumflex ligation and acquired multiple-slice cine magnetic resonance (MR) images in a longitudinal manner-before infarction, and 1 week (acute) and 4 weeks (chronic) after infarction. Computational fluid dynamic simulations were performed based on MR images to obtain detailed fluid dynamics and energy dynamics of the left ventricles. Results showed that energy efficiency flow through the heart decreased at the acute time point. Since the heart was observed to experience changes in heart rate, stroke volume and chamber size over the two post-infarction time points, simulations were performed to test the effect of each of the three parameters. Increasing heart rate and stroke volume were found to significantly decrease flow energy efficiency, but the effect of chamber size was inconsistent. Strong complex interplay was observed between the three parameters, necessitating the use of non-dimensional parameterization to characterize flow energy efficiency. The ratio of Reynolds to Strouhal number, which is a form of Womersley number, was found to be the most effective non-dimensional parameter to represent energy efficiency of flow in the heart. We believe that this non-dimensional number can be computed for clinical cases via ultrasound and hypothesize that it can serve as a biomarker for clinical evaluations.

  13. Avalanches dynamics in reaction fronts in disordered flows.

    PubMed

    Chevalier, T; Dubey, A K; Atis, S; Rosso, A; Salin, D; Talon, L

    2017-04-01

    We report on numerical studies of avalanches of an autocatalytic reaction front in a porous medium. The front propagation is controlled by an adverse flow resulting in upstream, static, or downstream regimes. In an earlier study focusing on front shape, we identified three different universality classes associated with this system by following the front dynamics experimentally and numerically. Here, using numerical simulations in the vicinity of the second-order transition, we identify an avalanche dynamics characterized by power-law distributions of avalanche sizes, durations, and lateral extensions. The related exponents agree well with the quenched-Kardar-Parisi-Zhang theory, which describes the front dynamics. However, the geometry of the propagating front differs slightly from that of the theoretical one. We show that this discrepancy can be understood in terms of the nonquasistatic correction induced by the finite front velocity.

  14. Regularization of hidden dynamics in piecewise smooth flows

    NASA Astrophysics Data System (ADS)

    Novaes, Douglas D.; Jeffrey, Mike R.

    2015-11-01

    This paper studies the equivalence between differentiable and non-differentiable dynamics in Rn. Filippov's theory of discontinuous differential equations allows us to find flow solutions of dynamical systems whose vector fields undergo switches at thresholds in phase space. The canonical convex combination at the discontinuity is only the linear part of a nonlinear combination that more fully explores Filippov's most general problem: the differential inclusion. Here we show how recent work relating discontinuous systems to singular limits of continuous (or regularized) systems extends to nonlinear combinations. We show that if sliding occurs in a discontinuous systems, there exists a differentiable slow-fast system with equivalent slow invariant dynamics. We also show the corresponding result for the pinching method, a converse to regularization which approximates a smooth system by a discontinuous one.

  15. Managing Critical Materials with a Technology-Specific Stocks and Flows Model

    PubMed Central

    2013-01-01

    The transition to low carbon infrastructure systems required to meet climate change mitigation targets will involve an unprecedented roll-out of technologies reliant upon materials not previously widespread in infrastructure. Many of these materials (including lithium and rare earth metals) are at risk of supply disruption. To ensure the future sustainability and resilience of infrastructure, circular economy policies must be crafted to manage these critical materials effectively. These policies can only be effective if supported by an understanding of the material demands of infrastructure transition and what reuse and recycling options are possible given the future availability of end-of-life stocks. This Article presents a novel, enhanced stocks and flows model for the dynamic assessment of material demands resulting from infrastructure transitions. By including a hierarchical, nested description of infrastructure technologies, their components, and the materials they contain, this model can be used to quantify the effectiveness of recovery at both a technology remanufacturing and reuse level and a material recycling level. The model’s potential is demonstrated on a case study on the roll-out of electric vehicles in the UK forecast by UK Department of Energy and Climate Change scenarios. The results suggest policy action should be taken to ensure Li-ion battery recycling infrastructure is in place by 2025 and NdFeB motor magnets should be designed for reuse. This could result in a reduction in primary demand for lithium of 40% and neodymium of 70%. PMID:24328245

  16. Managing critical materials with a technology-specific stocks and flows model.

    PubMed

    Busch, Jonathan; Steinberger, Julia K; Dawson, David A; Purnell, Phil; Roelich, Katy

    2014-01-21

    The transition to low carbon infrastructure systems required to meet climate change mitigation targets will involve an unprecedented roll-out of technologies reliant upon materials not previously widespread in infrastructure. Many of these materials (including lithium and rare earth metals) are at risk of supply disruption. To ensure the future sustainability and resilience of infrastructure, circular economy policies must be crafted to manage these critical materials effectively. These policies can only be effective if supported by an understanding of the material demands of infrastructure transition and what reuse and recycling options are possible given the future availability of end-of-life stocks. This Article presents a novel, enhanced stocks and flows model for the dynamic assessment of material demands resulting from infrastructure transitions. By including a hierarchical, nested description of infrastructure technologies, their components, and the materials they contain, this model can be used to quantify the effectiveness of recovery at both a technology remanufacturing and reuse level and a material recycling level. The model's potential is demonstrated on a case study on the roll-out of electric vehicles in the UK forecast by UK Department of Energy and Climate Change scenarios. The results suggest policy action should be taken to ensure Li-ion battery recycling infrastructure is in place by 2025 and NdFeB motor magnets should be designed for reuse. This could result in a reduction in primary demand for lithium of 40% and neodymium of 70%.

  17. Petrologic and Dynamic Importance of Flow Banding in Obsidian Lavas

    NASA Astrophysics Data System (ADS)

    Castro, J. M.; Dingwell, D. B.; Nichols, A.; Hess, K.

    2004-12-01

    One of the intriguing characteristics of effusive obsidians is the abundance of flow banding, or micrometer to centimeter-scale variations in microlite concentration. As these features arise from degassing, crystallization, and deformation processes, flow bands must contain important information regarding the chemical and physical evolution of obsidian magmas. Relatively little is known about the origin of this feature, and information on the relative rheologic properties of microlite-rich and poor bands is currently unavailable. In this paper, we present: 1) textural measurements on microlitic flow bands, 2) H2O concentrations, and 3) calorimetric measurements on flow bands of variable microlite content from several late Holocene obsidian flows. The goals are to better understand the mechanism of flow band formation and how these bands affect flow rheology and emplacement dynamics. Flow banded obsidians from Obsidian Dome (OD), Big Glass Mountain (BGM), and Big Obsidian Flow (BOF), are the focus of this study. Petrographic analysis shows that all obsidians contain microlites of pyroxene, feldspar, and oxide. However, the relative abundances of these phases vary dramatically within particular samples and between analyzed suites. Flow bands are therefore classified as 1) modal, wherein adjacent bands have the same mineral assemblage but contain different volume fractions, size distributions, and/or number densities of constituent phases, or 2) mineralogic, wherein adjacent bands differ by virtue of their constituent mineral assemblages. Banding in obsidians from both OD and BOF is dominantly modal, although rare bands display mineralogic differences defined by the presence or absence of plagioclase microlites. BGM obsidians tend to be modal in character, containing pyroxene microlites whose size and number densities vary across bands. Crystal size distributions measured on BGM obsidians reveal significant differences in the size and shape of microlite populations

  18. Visualization of bacterial flagella dynamics in a viscous shear flow

    NASA Astrophysics Data System (ADS)

    Ali, Jamel; Kim, Minjun

    2016-11-01

    We report on the dynamics of tethered bacterial flagella in an applied viscous shear flow and analyze their behavior using image processing. Flagellin proteins were repolymerized into flagellar filaments functionalized with biotin at their proximal end, and allowed to self-assemble within a micro channel coated with streptavidin. It was observed that all attached flagellar filaments aligned with the steady shear flow of various polymeric solutions. Furthermore it was observed that many of the filaments were stretched, and at elevated flow rates began to undergo polymorphic transformations, which were initiated at one end of the flagellum. When undergoing a change to a different helical form the flagellum was observed to transform to an oppositely handed helix, as to counteract the viscous torque imparted by the shear flow. It was also observed that some flagellar filaments did not undergo polymorphic transformations, but rotated about their helical axis. The rate of this rotation appears to be a function of the applied flow rate. These results expand on previous experimental work and aid in the development of a novel platform that harnesses the autonomic response of a 'forest' of bacterial flagella for engineering applications. This work was funded by NSF Grant CMMI-1000255, KEIT MOTIE Grant No. 10052980, and with Government support under and awarded by DoD, Air Force Office of Scientific Research, National Defense Science and Engineering Graduate (NDSEG) Fellowship, 32 CFR 168a.

  19. Droplet sizes, dynamics and deposition in vertical annular flow

    SciTech Connect

    Lopes, J C.B.; Dukler, A E

    1985-10-01

    The role of droplets in vertical upwards annular flow is investigated, focusing on the droplet size distributions, dynamics, and deposition phenomena. An experimental program was performed based on a new laser optical technique developed in these laboratories and implemented here for annular flow. This permitted the simultaneous measurement of droplet size, axial and radial velocity. The dependence of droplet size distributions on flow conditions is analyzed. The Upper-Log Normal function proves to be a good model for the size distribution. The mechanism controlling the maximum stable drop size was found to result from the interaction of the pressure fluctuations of the turbulent flow of the gas core with the droplet. The average axial droplet velocity showed a weak dependence on gas rates. This can be explained once the droplet size distribution and droplet size-velocity relationship are analyzed simultaneously. The surprising result from the droplet conditional analysis is that larger droplet travel faster than smaller ones. This dependence cannot be explained if the drag curves used do not take into account the high levels of turbulence present in the gas core in annular flow. If these are considered, then interesting new situations of multiplicity and stability of droplet terminal velocities are encountered. Also, the observed size-velocity relationship can be explained. A droplet deposition is formulated based on the particle inertia control. This permitted the calculation of rates of drop deposition directly from the droplet size and velocities data.

  20. Connecting exact coherent states to turbulent dynamics in channel flow

    NASA Astrophysics Data System (ADS)

    Park, Jae Sung; Graham, Michael D.

    2015-11-01

    The discovery of nonlinear traveling wave solutions to the Navier-Stokes equations or exact coherent states has greatly advanced the understanding of the nature of turbulent shear flows. These solutions are unstable saddle points in state space, while the time evolution of a turbulent flow is a dynamical trajectory wandering around them. In this regard, it is of interest to investigate how closely the turbulent trajectories approach these invariant states. Here, we present connections between turbulent trajectories and one intriguing solution family in channel flow. A state space visualization of turbulent trajectories is presented in a three-dimensional space. The lifetime of the trajectories is well represented by closeness to two distinct solutions resembling in many ways the active and hibernating phases of minimal channel turbulence (Xi & Graham PRL 2010). The connections are then examined by comparing mean profiles and flow structures. More importantly, the connections are confirmed by calculating the L2 distance between the trajectories and the traveling waves. Lastly, paths of an intermittent bursting phenomenon are identified in state space and the relationship between bursting paths and the traveling waves or hibernating turbulence is further discussed. This work was supported by the Air Force Office of Scientific Research through grant FA9550-15-1-0062 (Flow Interactions and Control Program).

  1. Deconvolution of reacting-flow dynamics using proper orthogonal and dynamic mode decompositions

    NASA Astrophysics Data System (ADS)

    Roy, Sukesh; Hua, Jia-Chen; Barnhill, Will; Gunaratne, Gemunu H.; Gord, James R.

    2015-01-01

    Analytical and computational studies of reacting flows are extremely challenging due in part to nonlinearities of the underlying system of equations and long-range coupling mediated by heat and pressure fluctuations. However, many dynamical features of the flow can be inferred through low-order models if the flow constituents (e.g., eddies or vortices) and their symmetries, as well as the interactions among constituents, are established. Modal decompositions of high-frequency, high-resolution imaging, such as measurements of species-concentration fields through planar laser-induced florescence and of velocity fields through particle-image velocimetry, are the first step in the process. A methodology is introduced for deducing the flow constituents and their dynamics following modal decomposition. Proper orthogonal (POD) and dynamic mode (DMD) decompositions of two classes of problems are performed and their strengths compared. The first problem involves a cellular state generated in a flat circular flame front through symmetry breaking. The state contains two rings of cells that rotate clockwise at different rates. Both POD and DMD can be used to deconvolve the state into the two rings. In POD the contribution of each mode to the flow is quantified using the energy. Each DMD mode can be associated with an energy as well as a unique complex growth rate. Dynamic modes with the same spatial symmetry but different growth rates are found to be combined into a single POD mode. Thus, a flow can be approximated by a smaller number of POD modes. On the other hand, DMD provides a more detailed resolution of the dynamics. Two classes of reacting flows behind symmetric bluff bodies are also analyzed. In the first, symmetric pairs of vortices are released periodically from the two ends of the bluff body. The second flow contains von Karman vortices also, with a vortex being shed from one end of the bluff body followed by a second shedding from the opposite end. The way in which

  2. Deconvolution of reacting-flow dynamics using proper orthogonal and dynamic mode decompositions.

    PubMed

    Roy, Sukesh; Hua, Jia-Chen; Barnhill, Will; Gunaratne, Gemunu H; Gord, James R

    2015-01-01

    Analytical and computational studies of reacting flows are extremely challenging due in part to nonlinearities of the underlying system of equations and long-range coupling mediated by heat and pressure fluctuations. However, many dynamical features of the flow can be inferred through low-order models if the flow constituents (e.g., eddies or vortices) and their symmetries, as well as the interactions among constituents, are established. Modal decompositions of high-frequency, high-resolution imaging, such as measurements of species-concentration fields through planar laser-induced florescence and of velocity fields through particle-image velocimetry, are the first step in the process. A methodology is introduced for deducing the flow constituents and their dynamics following modal decomposition. Proper orthogonal (POD) and dynamic mode (DMD) decompositions of two classes of problems are performed and their strengths compared. The first problem involves a cellular state generated in a flat circular flame front through symmetry breaking. The state contains two rings of cells that rotate clockwise at different rates. Both POD and DMD can be used to deconvolve the state into the two rings. In POD the contribution of each mode to the flow is quantified using the energy. Each DMD mode can be associated with an energy as well as a unique complex growth rate. Dynamic modes with the same spatial symmetry but different growth rates are found to be combined into a single POD mode. Thus, a flow can be approximated by a smaller number of POD modes. On the other hand, DMD provides a more detailed resolution of the dynamics. Two classes of reacting flows behind symmetric bluff bodies are also analyzed. In the first, symmetric pairs of vortices are released periodically from the two ends of the bluff body. The second flow contains von Karman vortices also, with a vortex being shed from one end of the bluff body followed by a second shedding from the opposite end. The way in which

  3. Open problems in active chaotic flows: Competition between chaos and order in granular materials.

    PubMed

    Ottino, J. M.; Khakhar, D. V.

    2002-06-01

    There are many systems where interaction among the elementary building blocks-no matter how well understood-does not even give a glimpse of the behavior of the global system itself. Characteristic for these systems is the ability to display structure without any external organizing principle being applied. They self-organize as a consequence of synthesis and collective phenomena and the behavior cannot be understood in terms of the systems' constitutive elements alone. A simple example is flowing granular materials, i.e., systems composed of particles or grains. How the grains interact with each other is reasonably well understood; as to how particles move, the governing law is Newton's second law. There are no surprises at this level. However, when the particles are many and the material is vibrated or tumbled, surprising behavior emerges. Systems self-organize in complex patterns that cannot be deduced from the behavior of the particles alone. Self-organization is often the result of competing effects; flowing granular matter displays both mixing and segregation. Small differences in either size or density lead to flow-induced segregation and order; similar to fluids, noncohesive granular materials can display chaotic mixing and disorder. Competition gives rise to a wealth of experimental outcomes. Equilibrium structures, obtained experimentally in quasi-two-dimensional systems, display organization in the presence of disorder, and are captured by a continuum flow model incorporating collisional diffusion and density-driven segregation. Several open issues remain to be addressed. These include analysis of segregating chaotic systems from a dynamical systems viewpoint, and understanding three-dimensional systems and wet granular systems (slurries). General aspects of the competition between chaos-enhanced mixing and properties-induced de-mixing go beyond granular materials and may offer a paradigm for other kinds of physical systems. (c) 2002 American Institute of

  4. Material Flow during Friction Stir Welding of HSLA 65 Steel

    NASA Astrophysics Data System (ADS)

    Young, John; Field, David; Nelson, Tracy

    2013-07-01

    Material flow during friction stir welding of HSLA-65 steel was investigated by crystallographic texture analysis. During the welding process, the steel deforms primarily by local shear deformation in the austenite phase and then transforms upon cooling. Texture data from three weld specimens were compared to theoretical textures calculated using ideal Euler angles for shear in face centered cubic (FCC) structures transformed by the Kurdjumov-Sacks (KS) relationship. These theoretical textures show similarities to the experimental textures. Texture data from the weld specimens revealed a rotation of the shear direction corresponding to the tangent of the weld tool on both the area directly under the weld tool shoulder and weld cross sections. In addition, texture data showed that while the shear plane of the area under the weld tool shoulder remained constant, the shear plane of the weld cross sections is influenced by the weld tool pin.

  5. Improved expanding ring technique for determining dynamic material properties.

    PubMed

    Liang, M Z; Li, X Y; Qin, J G; Lu, F Y

    2013-06-01

    An improved expanding ring experimental technique has been described to determine dynamic material properties under conditions approximating uniform one-dimensional tensile loading. There are mainly explosive expanding ring technique and electromagnetic expanding ring technique currently, for which exist many limitations in practical applications. The work reported herein is an attempt to overcome this difficulty by lateral efficiency loading produced by projectile, made of low-density material, impacting the same material filling. The lateral efficiency loading is a convenient and effective method, which allows materials to be in uniform uniaxial stress conditions at a high stress rate. The procedure is illustrated by experiments performed on 1100-0 aluminum rings.

  6. Ultrafast dynamic ellipsometry and spectroscopy of laser shocked materials

    SciTech Connect

    Bolme, Cynthia A; Mc Grane, Shawn D; Dang, Nhan C; Whitley, Von H; Moore, David S.

    2011-01-20

    Ultrafast dynamic ellipsometry is used to measure the material motion and changes in the optical refractive index of laser shock compressed materials. This diagnostic has shown us that the ultrafast laser driven shocks are the same as shocks on longer timescales and larger length scales. We have added spectroscopic diagnostics of infrared absorption, ultra-violet - visible transient absorption, and femtosecond stimulated Raman scattering to begin probing the initiation chemistry that occurs in shock reactive materials. We have also used the femtosecond stimulated Raman scattering to measure the vibrational temperature of materials using the Stokes gain to anti-Stokes loss ratio.

  7. On the dynamics of shallow gravel bed flow

    NASA Astrophysics Data System (ADS)

    Mohajeri, Seyed Hossein; Righetti, Maurizio; Wharton, Geraldene; Gurnell, Angela

    2013-04-01

    Flow dynamics on a gravel bed is a popular research subject because of environmental implications and especially in the presence of sediment transport. However, some features of flow dynamics on gravel beds are not completely understood and many questions remain open, especially in the context of the turbulence structure of the flow field and sediment transport. Due to the low submergence characteristics of the flow, the dynamics of the turbulent flow field, especially at the bed region, cannot be regarded as a classical boundary roughness problem, sensu Nikuradse (Nezu and Nakagawa, 1993) due to the strong spatial and temporal variation of the flow field. Over the past decade, in order to properly take into account the spatial heterogeneity, spatial averaging of time averaged values have become common. Besides,recently a trend to understand the role of gravel bed statistical properties, such as structure function of the bed elevation, on the statistics of the near-bed flow has been proposed. Although much research considers gravel beds by spatial averaging and research has been conducted on the effects of bed characteristics on near bed flow and sediment transport, only a few studies consider both together. In the present study, the results of 2D PIV measurement coupled with high accurate measurement of the gravel bed characteristics and the turbulence properties of the low submergence gravel bed flow as related to the bed properties are presented. The double averaging method was used in the analysis. Furthermore, in order to have a better insight into the dynamics of transport processes at the bed, a simple quadrant analysis, based on the Lu and Willmarth method, was implemented (Lu and Willmarth, 1973). Finally, the turbulent integral length scale was calculated both near and far from the gravel bed. The time and double averaged results show an agreement with the previous studies. Moreover, the result of quadrant analysis shows the sweep is dominant between

  8. Dynamic behaviour of multilamellar vesicles under Poiseuille flow.

    PubMed

    Pommella, A; Donnarumma, D; Caserta, S; Guido, S

    2017-09-27

    Surfactant solutions exhibit multilamellar surfactant vesicles (MLVs) under flow conditions and in concentration ranges which are found in a large number of industrial applications. MLVs are typically formed from a lamellar phase and play an important role in determining the rheological properties of surfactant solutions. Despite the wide literature on the collective dynamics of flowing MLVs, investigations into the flow behavior of single MLVs are scarce. In this work, we investigate a concentrated aqueous solution of linear alkylbenzene sulfonic acid (HLAS), characterized by MLVs dispersed in an isotropic micellar phase. Rheological tests show that the HLAS solution is a shear-thinning fluid with a power law index dependent on the shear rate. Pressure-driven shear flow of the HLAS solution in glass capillaries is investigated using high-speed video microscopy and image analysis. The so obtained velocity profiles provide evidence for a power-law fluid behaviour of the HLAS solution and images show a flow-focusing effect of the lamellar phase in the central core of the capillary. The flow behavior of individual MLVs shows analogies with that of unilamellar vesicles and emulsion droplets. Deformed MLVs exhibit typical shapes of unilamellar vesicles, such as parachute and bullet-like. Furthermore, MLV velocity follows the classical Hetsroni theory for droplets provided that the power law shear dependent viscosity of the HLAS solution is taken into account. The results of this work are relevant for the processing of surfactant-based systems in which the final properties depend on the flow-induced morphology, such as cosmetic formulations and food products.

  9. Cavitation erosion prediction based on analysis of flow dynamics and impact load spectra

    NASA Astrophysics Data System (ADS)

    Mihatsch, Michael S.; Schmidt, Steffen J.; Adams, Nikolaus A.

    2015-10-01

    Cavitation erosion is the consequence of repeated collapse-induced high pressure-loads on a material surface. The present paper assesses the prediction of impact load spectra of cavitating flows, i.e., the rate and intensity distribution of collapse events based on a detailed analysis of flow dynamics. Data are obtained from a numerical simulation which employs a density-based finite volume method, taking into account the compressibility of both phases, and resolves collapse-induced pressure waves. To determine the spectrum of collapse events in the fluid domain, we detect and quantify the collapse of isolated vapor structures. As reference configuration we consider the expansion of a liquid into a radially divergent gap which exhibits unsteady sheet and cloud cavitation. Analysis of simulation data shows that global cavitation dynamics and dominant flow events are well resolved, even though the spatial resolution is too coarse to resolve individual vapor bubbles. The inviscid flow model recovers increasingly fine-scale vapor structures and collapses with increasing resolution. We demonstrate that frequency and intensity of these collapse events scale with grid resolution. Scaling laws based on two reference lengths are introduced for this purpose. We show that upon applying these laws impact load spectra recorded on experimental and numerical pressure sensors agree with each other. Furthermore, correlation between experimental pitting rates and collapse-event rates is found. Locations of high maximum wall pressures and high densities of collapse events near walls obtained numerically agree well with areas of erosion damage in the experiment. The investigation shows that impact load spectra of cavitating flows can be inferred from flow data that captures the main vapor structures and wave dynamics without the need for resolving all flow scales.

  10. Cavitation erosion prediction based on analysis of flow dynamics and impact load spectra

    SciTech Connect

    Mihatsch, Michael S. Schmidt, Steffen J.; Adams, Nikolaus A.

    2015-10-15

    Cavitation erosion is the consequence of repeated collapse-induced high pressure-loads on a material surface. The present paper assesses the prediction of impact load spectra of cavitating flows, i.e., the rate and intensity distribution of collapse events based on a detailed analysis of flow dynamics. Data are obtained from a numerical simulation which employs a density-based finite volume method, taking into account the compressibility of both phases, and resolves collapse-induced pressure waves. To determine the spectrum of collapse events in the fluid domain, we detect and quantify the collapse of isolated vapor structures. As reference configuration we consider the expansion of a liquid into a radially divergent gap which exhibits unsteady sheet and cloud cavitation. Analysis of simulation data shows that global cavitation dynamics and dominant flow events are well resolved, even though the spatial resolution is too coarse to resolve individual vapor bubbles. The inviscid flow model recovers increasingly fine-scale vapor structures and collapses with increasing resolution. We demonstrate that frequency and intensity of these collapse events scale with grid resolution. Scaling laws based on two reference lengths are introduced for this purpose. We show that upon applying these laws impact load spectra recorded on experimental and numerical pressure sensors agree with each other. Furthermore, correlation between experimental pitting rates and collapse-event rates is found. Locations of high maximum wall pressures and high densities of collapse events near walls obtained numerically agree well with areas of erosion damage in the experiment. The investigation shows that impact load spectra of cavitating flows can be inferred from flow data that captures the main vapor structures and wave dynamics without the need for resolving all flow scales.

  11. A material flow of lithium batteries in Taiwan.

    PubMed

    Chang, T C; You, S J; Yu, B S; Yao, K F

    2009-04-30

    Li batteries, including secondary and cylindrical/button primary Li batteries, are used worldwide in computers, communications and consumer electronics products. However, there are several dangerous issues that occur during the manufacture, shipping, and storage of Li batteries. This study analyzes the material flow of lithium batteries and their valuable heavy metals in Taiwan for the year 2006 by material flow analysis. According to data from the Taiwan Environmental Protection Administration, Taiwan External Trade Development Council, Bureau of Foreign Trade, Directorate General of Customs, and the Li batteries manufactures/importers/exporters. It was found that 2,952,696 kg of Li batteries was input into Taiwan for the year 2006, including 2,256,501 kg of imported Li batteries and 696,195 kg of stock Li batteries in 2005. In addition, 1,113,867 and 572,215 kg of Li batteries was domestically produced and sold abroad, revealing that 3,494,348 kg of different types of Li batteries was sold in Taiwan. Of these domestically sold batteries, 504,663 and 146,557 kg were treated domestically and abroad. Thus, a total of 2,843,128 kg of Li batteries was stored by individual/industry users or illegally disposed. In addition, it was also observed that 2,120,682 kg of heavy metals contained in Li batteries, including Ni, Co, Al, Cu and Ni, was accumulated in Taiwan, with a recycled value of 38.8 million USD. These results suggest that these heavy metals should be recovered by suitable collection, recycling and reuse procedures.

  12. Flow injection spectrophotometric determination of boron in ceramic materials.

    PubMed

    Sanchez-Ramos, S; Medina-Hernández, M J; Sagrado, S

    1998-03-01

    A flow injection spectrophotometric method for the determination of boron in ceramic materials is described. The method is based on spectrophotometric measurement of the decrease in the pH produced by the reaction between boric acid and mannitol in the presence of an acid-base indicator. A bichannel FI (flow injection) manifold in which the sample solutions were injected into deionized water (at pH 5.4) and the stream was later merged with the reagent stream (a mannitol solution containing 1x10(-4) mol l(-1) bromocresol green at pH 5.4), was used. Transient signals were monitored at 616 nm. A theoretical model which describes the dependence between the absorbance values and boric acid concentration is presented. The model predicts a non linear dependence between the absorbance or increment in absorbance and the boric acid concentration. In contrast, the model predicts a linear dependence between the inverse of the absorbance values and the boric acid concentration. The calibration graphs (1/A vs mug ml(-1) B(2)O(3)) were linear over the range 1-30 mug ml(-1) of B(2)O(3). The relative standard deviations were 0.7 and 0.4% for 4 and 8 mug ml(-1) of B(2)O(3), respectively. The limit of detection was 0.02 mug ml(-1) of B(2)O(3) (3sigma criterium). The method was used to determine boron in nine ceramic materials with very different nominal boron compositions. The results were compared with those obtained using a potentiometric titration method as reference method. No significant differences (at 95% probability level) were found between the proposed and reference methods. The method is rapid, reliable, precise and free of interferences.

  13. Structure and Dynamics of a Model Discotic Organic Conducting Material

    NASA Astrophysics Data System (ADS)

    Zbiri, Mohamed; Haverkate, Lucas A.; Kearley, Gordon J.; Johnson, Mark R.; Mulder, Fokko M.

    2016-10-01

    Organic conducting materials exhibit promising functionalities, inducing hence a keen interest due to their potential use as a next generation photoconverters. However, unlike the more expensive inorganic analogues, the underlying properties that give rise to these advantages also cause organic materials to be inherently inefficient as photovoltaics. Understanding their properties at the microscopic level is a major step towards an efficient and targeted design. We probed the morphological and dynamical aspects of a model organic discotic liquid crystal material hexakis(n-hexyloxy)triphenylene (HAT6) by using neutron-based diffraction and quasielastic scattering techniques to gain deeper insights into structure and dynamics. The neutron measurements are accompanied, in a synergistic way, by molecular dynamics simulations for the sake of the analysis and interpretation of the observations

  14. Material and Energy Flows in the Production of Cathode and Anode Materials for Lithium Ion Batteries

    SciTech Connect

    Dunn, Jennifer B.; James, Christine; Gaines, Linda; Gallagher, Kevin; Dai, Qiang; Kelly, Jarod C.

    2015-09-01

    The Greenhouse gases, Regulated Emissions and Energy use in Transportation (GREET) model has been expanded to include four new cathode materials that can be used in the analysis of battery-powered vehicles: lithium nickel cobalt manganese oxide (LiNi0.4Co0.2Mn0.4O2 [NMC]), lithium iron phosphate (LiFePO4 [LFP]), lithium cobalt oxide (LiCoO2 [LCO]), and an advanced lithium cathode (0.5Li2MnO3∙0.5LiNi0.44Co0.25Mn0.31O2 [LMR-NMC]). In GREET, these cathode materials are incorporated into batteries with graphite anodes. In the case of the LMR-NMC cathode, the anode is either graphite or a graphite-silicon blend. Lithium metal is also an emerging anode material. This report documents the material and energy flows of producing each of these cathode and anode materials from raw material extraction through the preparation stage. For some cathode materials, we considered solid state and hydrothermal preparation methods. Further, we used Argonne National Laboratory’s Battery Performance and Cost (BatPaC) model to determine battery composition (e.g., masses of cathode, anode, electrolyte, housing materials) when different cathode materials were used in the battery. Our analysis concluded that cobalt- and nickel-containing compounds are the most energy intensive to produce.

  15. Getting Out Of A Tight Spot: Physics Of Flow Through Porous Materials

    NASA Astrophysics Data System (ADS)

    Datta, Sujit Sankar

    We study the physics of flow through porous materials in two different ways: by directly visualizing flow through a model three-dimensional (3D) porous medium, and by investigating the deformability of fluid-filled microcapsules having porous shells. In the first part of this thesis, we develop an experimental approach to directly visualize fluid flow through a 3D porous medium. We use this to investigate drainage, the displacement of a wetting fluid from a porous medium by a non-wetting fluid, as well as secondary imbibition, the subsequent displacement of the non-wetting fluid by the wetting fluid. We characterize the intricate morphologies of the non-wetting fluid ganglia left trapped within the pore space, and show how the ganglia configurations vary with the wetting fluid flow rate. We then visualize the spatial fluctuations in the fluid flow, both for single- and multi-phase flow. We use our measurements to quantify the strong variability in the flow velocities, as well as the pore-scale correlations in the flow. Finally, we use our experimental approach to study the simultaneous flow of both a wetting and a non-wetting fluid through a porous medium, and elucidate the flow instabilities that arise for sufficiently large flow rates. In the second part of this thesis, we study the mechanical properties of porous spherical microcapsules. We first introduce emulsions, and describe how their rheology depends on the microscopic interactions between the drops comprising them. We then study the formation and buckling of one class of microcapsule -- nanoparticle-coated emulsion drops. We also use double emulsions, drops within drops, as templates to form another class of microcapsule -- drops coated with thin, porous, polymer shells. We investigate how, under sufficient osmotic pressure, these microcapsules buckle, and show how the inhomogeneity in the shell structure can guide the folding pathway taken by a microcapsule as it buckles. Finally, we study the expansion

  16. Dynamics of Diffusion Flames in von Karman Swirling Flows Studied

    NASA Technical Reports Server (NTRS)

    Nayagam, Vedha; Williams, Forman A.

    2002-01-01

    Von Karman swirling flow is generated by the viscous pumping action of a solid disk spinning in a quiescent fluid media. When this spinning disk is ignited in an oxidizing environment, a flat diffusion flame is established adjacent to the disk, embedded in the boundary layer (see the preceding illustration). For this geometry, the conservation equations reduce to a system of ordinary differential equations, enabling researchers to carry out detailed theoretical models to study the effects of varying strain on the dynamics of diffusion flames. Experimentally, the spinning disk burner provides an ideal configuration to precisely control the strain rates over a wide range. Our original motivation at the NASA Glenn Research Center to study these flames arose from a need to understand the flammability characteristics of solid fuels in microgravity where slow, subbuoyant flows can exist, producing very small strain rates. In a recent work (ref. 1), we showed that the flammability boundaries are wider and the minimum oxygen index (below which flames cannot be sustained) is lower for the von Karman flow configuration in comparison to a stagnation-point flow. Adding a small forced convection to the swirling flow pushes the flame into regions of higher strain and, thereby, decreases the range of flammable strain rates. Experiments using downward facing, polymethylmethacrylate (PMMA) disks spinning in air revealed that, close to the extinction boundaries, the flat diffusion flame breaks up into rotating spiral flames (refs. 2 and 3). Remarkably, the dynamics of these spiral flame edges exhibit a number of similarities to spirals observed in biological systems, such as the electric pulses in cardiac muscles and the aggregation of slime-mold amoeba. The tail of the spiral rotates rigidly while the tip executes a compound, meandering motion sometimes observed in Belousov-Zhabotinskii reactions.

  17. Dynamic Characterization and Modeling of Potting Materials for Electronics Assemblies

    NASA Astrophysics Data System (ADS)

    Joshi, Vasant; Lee, Gilbert; Santiago, Jaime

    2015-06-01

    Prediction of survivability of encapsulated electronic components subject to impact relies on accurate modeling. Both static and dynamic characterization of encapsulation material is needed to generate a robust material model. Current focus is on potting materials to mitigate high rate loading on impact. In this effort, encapsulation scheme consists of layers of polymeric material Sylgard 184 and Triggerbond Epoxy-20-3001. Experiments conducted for characterization of materials include conventional tension and compression tests, Hopkinson bar, dynamic material analyzer (DMA) and a non-conventional accelerometer based resonance tests for obtaining high frequency data. For an ideal material, data can be fitted to Williams-Landel-Ferry (WLF) model. A new temperature-time shift (TTS) macro was written to compare idealized temperature shift factor (WLF model) with experimental incremental shift factors. Deviations can be observed by comparison of experimental data with the model fit to determine the actual material behavior. Similarly, another macro written for obtaining Ogden model parameter from Hopkinson Bar tests indicates deviations from experimental high strain rate data. In this paper, experimental results for different materials used for mitigating impact, and ways to combine data from resonance, DMA and Hopkinson bar together with modeling refinements will be presented.

  18. Wake flow control using a dynamically controlled wind turbine

    NASA Astrophysics Data System (ADS)

    Castillo, Ricardo; Wang, Yeqin; Pol, Suhas; Swift, Andy; Hussain, Fazle; Westergaard, Carsten; Texas Tech University Team

    2016-11-01

    A wind tunnel based "Hyper Accelerated Wind Farm Kinematic-Control Simulator" (HAWKS) is being built at Texas Tech University to emulate controlled wind turbine flow physics. The HAWKS model turbine has pitch, yaw and speed control which is operated in real model time, similar to that of an equivalent full scale turbine. Also, similar to that of a full scale wind turbine, the controls are developed in a Matlab Simulink environment. The current diagnostic system consists of power, rotor position, rotor speed measurements and PIV wake characterization with four cameras. The setup allows up to 7D downstream of the rotor to be mapped. The purpose of HAWKS is to simulate control strategies at turnaround times much faster than CFD and full scale testing. The fundamental building blocks of the simulator have been tested, and demonstrate wake steering for both static and dynamic turbine actuation. Parameters which have been studied are yaw, rotor speed and combinations hereof. The measured wake deflections for static yaw cases are in agreement with previously reported research implying general applicability of the HAWKS platform for the purpose of manipulating the wake. In this presentation the general results will be introduced followed by an analysis of the wake turbulence and coherent structures when comparing static and dynamic flow cases. The outcome of such studies could ultimately support effective wind farm wake flow control strategies. Texas Emerging Technology Fund (ETF).

  19. River flow regimes and vegetation dynamics along a river transect

    NASA Astrophysics Data System (ADS)

    Doulatyari, Behnam; Basso, Stefano; Schirmer, Mario; Botter, Gianluca

    2014-11-01

    Ecohydrological processes occurring within fluvial landscapes are strongly affected by natural streamflow variability. In this work the patterns of vegetation biomass in two rivers characterized by contrasting flow regimes were investigated by means of a comprehensive stochastic model which explicitly couples catchment-scale hydroclimatic processes, morphologic attributes of the river transect and in-stream bio-ecological features. The hydrologic forcing is characterized by the probability distribution (pdf) of streamflows and stages resulting from stochastic precipitation dynamics, rainfall-runoff transformation and reach scale morphologic attributes. The model proved able to reproduce the observed pdf of river flows and stages, as well as the pattern of exposure/inundation along the river transect in both regimes. Our results suggest that in persistent regimes characterized by reduced streamflow variability, mean vegetation biomass is chiefly controlled by the pattern of groundwater availability along the transect, leading to a marked transition between aquatic and terrestrial environments. Conversely, erratic regimes ensure wider aquatic-terrestrial zones in which optimal elevation ranges for species with different sensitivity to flooding and access to groundwater are separated. Patterns of mean biomass in erratic regimes were found to be more sensitive to changes in the underlying hydroclimatic conditions, notwithstanding the reduced responsiveness of the corresponding flow regimes. The framework developed highlights the important role played by streamflow regimes in shaping riverine environments, and may eventually contribute to identifying the influence of landscape, climate and morphologic features on in-stream ecological dynamics.

  20. Extensional Flow-Induced Dynamic Phase Transitions in Isotactic Polypropylene.

    PubMed

    Ju, Jianzhu; Wang, Zhen; Su, Fengmei; Ji, Youxin; Yang, Haoran; Chang, Jiarui; Ali, Sarmad; Li, Xiangyang; Li, Liangbin

    2016-09-01

    With a combination of fast extension rheometer and in situ synchrotron radiation ultra-fast small- and wide-angle X-ray scattering, flow-induced crystallization (FIC) of isotactic polypropylene (iPP) is studied at temperatures below and above the melting point of α crystals (Tmα). A flow phase diagram of iPP is constructed in strain rate-temperature space, composing of melt, non-crystalline shish, α and α&β coexistence regions, based on which the kinetic and dynamic competitions among these four phases are discussed. Above Tmα , imposing strong flow reverses thermodynamic stabilities of the disordered melt and the ordered phases, leading to the occurrence of FIC of β and α crystals as a dynamic phase transition. Either increasing temperature or stain rate favors the competiveness of the metastable β over the stable α crystals, which is attributed to kinetic rate rather than thermodynamic stability. The violent competitions among four phases near the boundary of crystal-melt may frustrate crystallization and result in the non-crystalline shish winning out.

  1. Grain-level simulation of dynamic failure in ceramic materials

    NASA Astrophysics Data System (ADS)

    Maiti, Spandan

    2002-04-01

    Advanced ceramic materials are finding increasing use in different adverse mechanical and chemical situations due to their good mechanical properties, corrosion resistance and thermal stability. Their wider use is however impeded by their brittleness, especially in applications involving dynamic loads, in which dynamic fracture and fragmentation events are often observed. Most of the research aimed at the understanding of dynamic crack initiation and propagation mechanisms in this class of materials do not take into account the inherent granular microstructure of ceramics. In this project, we develop a grain-based finite element scheme that allows for the mesoscale study of a range of dynamic failure events in granular media, including propagation and branching of inter-granular cracks and fragmentation. The scheme relies on Voronoi tessellation to generate the granular microstructure and on a 2-D explicit cohesive/volumetric finite element (CVFE) scheme to simulate the constitutive and failure response of the material under dynamic loads. A non-linear kinematics description is used in our analysis to account for the possible large deformations and/or rotations of the grains during the fracture event. A viscoplastic update algorithm is also introduced to model problems (such as dynamic indentation and grinding) for which localized plasticity plays a key role. The numerical scheme finally relies on robust contact search and enforcement algorithms to capture the complex contact events between fracture surfaces, between individual grains and between the impactor/tool and the ceramic specimen. To demonstrate the capabilities and versatility of the grain-based CVFE code, we investigate four dynamic fracture problems. The first one is concerned with the propagation of dynamic intergranular cracks under mode I loading, with special emphasis on the effect of the microstructure on the branching instability of the crack motion. The second problem is that of dynamic fracture

  2. Vertical Wellbore Flow Monitoring for Assessing Spatial and Temporal Flow Relationships with a Dynamic River Boundary

    SciTech Connect

    Newcomer, Darrell R.; Bjornstad, Bruce N.; Vermeul, Vincent R.

    2010-10-01

    A useful tool for identifying the temporal and spatial ambient wellbore flow relationships near a dynamic river boundary is to continuously monitor ambient vertical wellbore flow with an electromagnetic borehole flowmeter (EBF). This is important because the presence of the wellbore can result in significant mixing or exchange of groundwater vertically across the aquifer. Mixing or exchanging groundwater within the well-screen section can have significant impacts on the distribution of contaminants within the aquifer and adverse effects on the representativeness of groundwater samples collected from the monitoring well. EBF monitoring data collected from long, fully screened wells at Hanford’s 300-Area Integrated Field Research Challenge (IFRC) site, located ~260 to 290 m from the Columbia River, demonstrate that ambient vertical wellbore flow exhibits both a positive (direct) and inverse temporal relationship with periodic river-stage fluctuations over short distances. The ambient flow monitoring wells fully penetrate a highly transmissive unconfined aquifer that consists of unconsolidated coarse sediments of the Hanford formation. The spatial distribution of ambient vertical wellbore flows across the IFRC’s ~2,200 m2 well-field size indicates two general regions of inverse ambient wellbore flow behavior. The western region of the IFRC site is characterized by ambient vertical wellbore flows that are positively related to river-stage fluctuations. In contrast, the eastern region of the site exhibits ambient wellbore flows that are inversely related to river-stage fluctuations. The cause of this opposite relationship between ambient wellbore flows and river-stage changes is not completely understood; however, the positive relationships appear to be associated with high-energy Hanford formation flood deposits. These flood deposits have a well-defined northwest-southeast trend and are believed to coincide with a local paleochannel. This local paleochannel bisects

  3. Dynamics of monocytes flowing in a model pulmonary capillary bed

    NASA Astrophysics Data System (ADS)

    Viallat, Annie; Dupire, Jules; Adhesion and Inflammation lab Team

    2012-11-01

    The dynamics of blood cells in the pulmonary bed is an issue for tissue perfusion and host defense. The capillary segments in the lungs are smaller than the size of leukocytes so that most of them change their shape to enter and travel through a capillary pathway. During inflammation, changes in the cytoskeleton of leukocytes may stiffen them, resulting in their massive stop and sequestration within lung capillaries. However, due to difficulties of in vivo studies, little is known about the dynamics of leukocytes in the microcirculation and about the coupling between cellular rheology, capillary geometry and flow. We report the dynamics of monocytes (THP-1 cell line) flowing under constant pressure drop in a periodic network of capillaries that mimics the capillary bed. The analysis of cell entrance in the first segment allows the estimation of effective cellular elasticity, viscosity and cortical tension. Cells then present an unsteady regime, with a non-periodic trajectory, a stretching of their average shape and an increase of their velocity. This regime is interpreted from a parameter equivalent to the Deborah number of the system. Finally, a periodic regime is reached with alternatively left and right turns at capillary bifurcations. The reduced cell velocity is governed by an effective friction coefficient between the cell and the capillary walls. Both transient and final regimes depend on cell deformability, as shown by modifying the cortical actin of the cytoskeleton. This work has been supported by the French Research. National Agency (ANR) under reference ChipCellTrap.

  4. Dynamically Scaled Glottal Flow Through Symmetrically Oscillating Vocal Fold Models

    NASA Astrophysics Data System (ADS)

    Halvorson, Lori; Baitinger, Andrew; Sherman, Erica; Krane, Michael; Zhang, Lucy; Wei, Timothy

    2011-11-01

    Experimental results derived from DPIV measurements in a scaled up dynamic human vocal fold model are presented. The 10x scale vocal fold model is a new design that incorporates key features of vocal fold oscillatory motion. This includes coupling of down/upstream rocking as well as the oscillatory open/close motions. Experiments were dynamically scaled to examine a range of frequencies, 100 - 200 Hz, corresponding to the male and female voice. By using water as the working fluid, very high resolution, both spatial and temporal resolution, was achieved. Time resolved movies of flow through symmetrically oscillating vocal folds will be presented. Both individual realizations as well as phase-averaged data will be shown. Key features, such as randomness and development time of the Coanda effect, vortex shedding, and volume flow rate data will be shown. In this talk, effects associated with paralysis of one vocal fold will be discussed. This talk provides the baseline fluid dynamics for the vocal fold paralysis study presented in Sherman, et al. Supported by the NIH.

  5. Unbounded dynamics in dissipative flows: Rössler model.

    PubMed

    Barrio, Roberto; Blesa, Fernando; Serrano, Sergio

    2014-06-01

    Transient chaos and unbounded dynamics are two outstanding phenomena that dominate in chaotic systems with large regions of positive and negative divergences. Here, we investigate the mechanism that leads the unbounded dynamics to be the dominant behavior in a dissipative flow. We describe in detail the particular case of boundary crisis related to the generation of unbounded dynamics. The mechanism of the creation of this crisis in flows is related to the existence of an unstable focus-node (or a saddle-focus) equilibrium point and the crossing of a chaotic invariant set of the system with the weak-(un)stable manifold of the equilibrium point. This behavior is illustrated in the well-known Rössler model. The numerical analysis of the system combines different techniques as chaos indicators, the numerical computation of the bounded regions, and bifurcation analysis. For large values of the parameters, the system is studied by means of Fenichel's theory, providing formulas for computing the slow manifold which influences the evolution of the first stages of the orbit.

  6. Unbounded dynamics in dissipative flows: Rössler model

    SciTech Connect

    Barrio, Roberto Serrano, Sergio; Blesa, Fernando

    2014-06-15

    Transient chaos and unbounded dynamics are two outstanding phenomena that dominate in chaotic systems with large regions of positive and negative divergences. Here, we investigate the mechanism that leads the unbounded dynamics to be the dominant behavior in a dissipative flow. We describe in detail the particular case of boundary crisis related to the generation of unbounded dynamics. The mechanism of the creation of this crisis in flows is related to the existence of an unstable focus-node (or a saddle-focus) equilibrium point and the crossing of a chaotic invariant set of the system with the weak-(un)stable manifold of the equilibrium point. This behavior is illustrated in the well-known Rössler model. The numerical analysis of the system combines different techniques as chaos indicators, the numerical computation of the bounded regions, and bifurcation analysis. For large values of the parameters, the system is studied by means of Fenichel's theory, providing formulas for computing the slow manifold which influences the evolution of the first stages of the orbit.

  7. Unbounded dynamics in dissipative flows: Rössler model

    SciTech Connect

    Barrio, Roberto Serrano, Sergio; Blesa, Fernando

    2014-06-15

    Transient chaos and unbounded dynamics are two outstanding phenomena that dominate in chaotic systems with large regions of positive and negative divergences. Here, we investigate the mechanism that leads the unbounded dynamics to be the dominant behavior in a dissipative flow. We describe in detail the particular case of boundary crisis related to the generation of unbounded dynamics. The mechanism of the creation of this crisis in flows is related to the existence of an unstable focus-node (or a saddle-focus) equilibrium point and the crossing of a chaotic invariant set of the system with the weak-(un)stable manifold of the equilibrium point. This behavior is illustrated in the well-known Rössler model. The numerical analysis of the system combines different techniques as chaos indicators, the numerical computation of the bounded regions, and bifurcation analysis. For large values of the parameters, the system is studied by means of Fenichel's theory, providing formulas for computing the slow manifold which influences the evolution of the first stages of the orbit.

  8. Dynamics of nonspherical compound capsules in simple shear flow

    NASA Astrophysics Data System (ADS)

    Luo, Zheng Yuan; Bai, Bo Feng

    2016-10-01

    The dynamics of an initially ellipsoidal compound capsule in a simple shear flow is investigated numerically using a three-dimensional front-tracking finite-difference model. Membrane bending resistance is included based on Helfrich's energy function besides the resistances against shear deformation and area dilatation governed by the constitutive law of Skalak et al. In this paper, we focus specifically on how the presence of a spherical inner capsule and its size affects the characteristics and transition of various dynamical states of nonspherical compound capsules (i.e., the outer capsule). Significant differences in the dynamical characteristics are observed between compound capsules and homogeneous capsules in both qualitative and quantitative terms. We find the transition from swinging to tumbling can occur at vanishing viscosity mismatch through increasing the inner capsule size alone to a critical value regardless of the initial shape of the nonspherical compound capsule (i.e., prolate or oblate). Besides, for compound capsules with viscosity mismatch, the critical viscosity ratio for the swinging-to-tumbling transition remarkably decreases by increasing the inner capsule size. It is thus concluded that the inner capsule size is a key governing parameter of compound capsule dynamics apart from the capillary number, aspect ratio, and viscosity ratio that have been long identified for homogeneous capsules. Further, we discuss the mechanisms underlying the effects of the inner capsule on the compound capsule dynamics from the viewpoint of the effective viscosity of internal fluid and find that the effects of the inner capsule on compound capsule dynamics are qualitatively similar to that of increasing the internal viscosity on homogeneous capsule dynamics. However, in quantitative terms, the compound capsule cannot be viewed as a homogeneous capsule with higher viscosity as obvious inhomogeneity in fluid stress distribution is induced by the inner membrane.

  9. Material and Energy Flows in the Production of Cathode and Anode Materials for Lithium Ion Batteries

    SciTech Connect

    Dunn, Jennifer B.; James, Christine; Gaines, Linda G.; Gallagher, Kevin

    2014-09-30

    The Greenhouse gases, Regulated Emissions and Energy use in Transportation (GREET) model has been expanded to include four new cathode materials that can be used in the analysis of battery-powered vehicles: lithium nickel cobalt manganese oxide (LiNi0.4Co0.2Mn0.4O2 [NMC]), lithium iron phosphate (LiFePO4 [LFP]), lithium cobalt oxide (LiCoO2 [LCO]), and an advanced lithium cathode (0.5Li2MnO3∙0.5LiNi0.44Co0.25Mn0.31O2 [LMR-NMC]). In GREET, these cathode materials are incorporated into batteries with graphite anodes. In the case of the LMR-NMC cathode, the anode is either graphite or a graphite-silicon blend. This report documents the material and energy flows of producing each of these cathode and anode materials from raw material extraction through the preparation stage. For some cathode materials, we considered solid state and hydrothermal preparation methods. Further, we used Argonne National Laboratory’s Battery Performance and Cost (BatPaC) model to determine battery composition (e.g., masses of cathode, anode, electrolyte, housing materials) when different cathode materials were used in the battery. Our analysis concluded that cobalt- and nickel-containing compounds are the most energy intensive to produce.

  10. Optical studies of dynamical processes in disordered materials

    SciTech Connect

    Yen, W.M.

    1990-12-01

    Our research continues to focus on the study of the structure and the dynamic behavior of insulating solids which can be activated optically. We have been particularly interested in the physical processes which produce relaxation and energy transfer in the optical excited states. Our studies have been based principally on optical laser spectroscopic techniques which reveal a more detailed view of the materials of interest and which will ultimately lead to the development of more efficient optoelectronic materials. 13 refs.

  11. Simulation of dynamic material response with the PAGOSA code

    SciTech Connect

    Holian, K.S.; Adams, T.F.

    1993-08-01

    The 3D Eulerian PAGOSA hydrocode is being run on the massively parallel Connection Machine (CM) to simulate the response of materials to dynamic loading, such as by high explosives or high velocity impact. The code has a variety of equation of state forms, plastic yield models, and fracture and fragmentation models. The numerical algorithms in PAGOSA and the implementation of material models are discussed briefly.

  12. Dynamic Power Flow Controller: Compact Dynamic Phase Angle Regulators for Transmission Power Routing

    SciTech Connect

    2012-01-03

    GENI Project: Varentec is developing compact, low-cost transmission power controllers with fractional power rating for controlling power flow on transmission networks. The technology will enhance grid operations through improved use of current assets and by dramatically reducing the number of transmission lines that have to be built to meet increasing contributions of renewable energy sources like wind and solar. The proposed transmission controllers would allow for the dynamic control of voltage and power flow, improving the grid’s ability to dispatch power in real time to the places where it is most needed. The controllers would work as fail-safe devices whereby the grid would be restored to its present operating state in the event of a controller malfunction instead of failing outright. The ability to affordably and dynamically control power flow with adequate fail-safe switchgear could open up new competitive energy markets which are not possible under the current regulatory structure and technology base.

  13. A numerical model for dynamic crustal-scale fluid flow

    NASA Astrophysics Data System (ADS)

    Sachau, Till; Bons, Paul; Gomez-Rivas, Enrique; Koehn, Daniel

    2015-04-01

    Fluid flow in the crust is often envisaged and modeled as continuous, yet minimal flow, which occurs over large geological times. This is a suitable approximation for flow as long as it is solely controlled by the matrix permeability of rocks, which in turn is controlled by viscous compaction of the pore space. However, strong evidence (hydrothermal veins and ore deposits) exists that a significant part of fluid flow in the crust occurs strongly localized in both space and time, controlled by the opening and sealing of hydrofractures. We developed, tested and applied a novel computer code, which considers this dynamic behavior and couples it with steady, Darcian flow controlled by the matrix permeability. In this dual-porosity model, fractures open depending on the fluid pressure relative to the solid pressure. Fractures form when matrix permeability is insufficient to accommodate fluid flow resulting from compaction, decompression (Staude et al. 2009) or metamorphic dehydration reactions (Weisheit et al. 2013). Open fractures can close when the contained fluid either seeps into the matrix or escapes by fracture propagation: mobile hydrofractures (Bons, 2001). In the model, closing and sealing of fractures is controlled by a time-dependent viscous law, which is based on the effective stress and on either Newtonian or non-Newtonian viscosity. Our simulations indicate that the bulk of crustal fluid flow in the middle to lower upper crust is intermittent, highly self-organized, and occurs as mobile hydrofractures. This is due to the low matrix porosity and permeability, combined with a low matrix viscosity and, hence, fast sealing of fractures. Stable fracture networks, generated by fluid overpressure, are restricted to the uppermost crust. Semi-stable fracture networks can develop in an intermediate zone, if a critical overpressure is reached. Flow rates in mobile hydrofractures exceed those in the matrix porosity and fracture networks by orders of magnitude

  14. Dynamic Modelling of Erosion and Deposition Processes in Debris Flows With Application to Real Debris Flow Events in Switzerland

    NASA Astrophysics Data System (ADS)

    Deubelbeiss, Y.; McArdell, B. W.; Graf, C.

    2011-12-01

    The dynamics of a debris flow can be significantly influenced by erosion and deposition processes during an event because volume changes have a strong influence on flow properties such as flow velocity, flow heights and runout distances. It is therefore worth exploring how to include these processes in numerical models, which are used for hazard assessment and mitigation measure planning. However, it is still under debate, what mechanism drives the erosion of material at the base of a debris flow. There are different processes attributed to erosion: it has been proposed that erosion correlates with the stresses due to granular interactions at the front, which in turn strongly depend on particle size or it may be related to basal shear forces. Because it is expected that larger flow heights result in larger stresses one can additionally hypothesize that there is a correlation between erosion rate and flow height. To test different erosion laws in a numerical model and its influence on the flow behavior we implement different relationships and compare simulation results with field data. Herefore, we use the numerical model, RAMMS (Christen et al., 2010), employing the Voellmy-fluid friction law. While it has already been shown that a correlation of erosion with velocity does not lead to a satisfying result (too high entrainment in the tail) a correlation with flow height combined with velocity (momentum) has been successfully applied to ice-avalanches. Currently, we are testing the momentum-driven and for comparison we reconsider the simple velocity-driven erosion rate. However, these laws do not consider processes on a smaller scale such as particle fluctuations resulting in energy production, which might play an important role. Therefore, we additionally consider an erosion model that has potential to draw new insights on the erosion process in debris flows. The model is based on an extended Voellmy model, which additionally employs an equation, which is a measure

  15. Scoping Future Policy Dynamics in Raw Materials Through Scenarios Testing

    NASA Astrophysics Data System (ADS)

    Correia, Vitor; Keane, Christopher; Sturm, Flavius; Schimpf, Sven; Bodo, Balazs

    2017-04-01

    The International Raw Materials Observatory (INTRAW) project is working towards a sustainable future for the European Union in access to raw materials, from an availability, economical, and environmental framework. One of the major exercises for the INTRAW project is the evaluation of potential future scenarios for 2050 to frame economic, research, and environmental policy towards a sustainable raw materials supply. The INTRAW consortium developed three possible future scenarios that encompass defined regimes of political, economic, and technological norms. The first scenario, "Unlimited Trade," reflects a world in which free trade continues to dominate the global political and economic environment, with expectations of a growing demand for raw materials from widely distributed global growth. The "National Walls" scenario reflects a world where nationalism and economic protectionism begins to dominate, leading to stagnating economic growth and uneven dynamics in raw materials supply and demand. The final scenario, "Sustainability Alliance," examines the dynamics of a global political and economic climate that is focused on environmental and economic sustainability, leading towards increasingly towards a circular raw materials economy. These scenarios were reviewed, tested, and provided simulations of impacts with members of the Consortium and a panel of global experts on international raw materials issues which led to expected end conditions for 2050. Given the current uncertainty in global politics, these scenarios are informative to identifying likely opportunities and crises. The details of these simulations and expected responses to the research demand, technology investments, and economic components of raw materials system will be discussed.

  16. Vortical Flows Research Program of the Fluid Dynamics Research Branch

    NASA Technical Reports Server (NTRS)

    1986-01-01

    The research interests of the staff of the Fluid Dynamics Research Branch in the general area of vortex flows are summarized. A major factor in the development of enchanced maneuverability and reduced drag by aerodynamic means is the use of effective vortex control devices. The key to control is the use of emerging computational tools for predicting viscous fluid flow in close coordination with fundamental experiments. In fact, the extremely complex flow fields resulting from numerical solutions to boundary value problems based on the Navier-Stokes equations requires an intimate relationship between computation and experiment. The field of vortex flows is important in so many practical areas that a concerted effort in this area is justified. A brief background of the research activity undertaken is presented, including a proposed classification of the research areas. The classification makes a distinction between issues related to vortex formation and structure, and work on vortex interactions and evolution. Examples of current research results are provided, along with references where available. Based upon the current status of research and planning, speculation on future research directions of the group is also given.

  17. Nephron blood flow dynamics measured by laser speckle contrast imaging

    PubMed Central

    Holstein-Rathlou, Niels-Henrik; Sosnovtseva, Olga V.; Pavlov, Alexey N.; Cupples, William A.; Sorensen, Charlotte Mehlin

    2011-01-01

    Tubuloglomerular feedback (TGF) has an important role in autoregulation of renal blood flow and glomerular filtration rate (GFR). Because of the characteristics of signal transmission in the feedback loop, the TGF undergoes self-sustained oscillations in single-nephron blood flow, GFR, and tubular pressure and flow. Nephrons interact by exchanging electrical signals conducted electrotonically through cells of the vascular wall, leading to synchronization of the TGF-mediated oscillations. Experimental studies of these interactions have been limited to observations on two or at most three nephrons simultaneously. The interacting nephron fields are likely to be more extensive. We have turned to laser speckle contrast imaging to measure the blood flow dynamics of 50–100 nephrons simultaneously on the renal surface of anesthetized rats. We report the application of this method and describe analytic techniques for extracting the desired data and for examining them for evidence of nephron synchronization. Synchronized TGF oscillations were detected in pairs or triplets of nephrons. The amplitude and the frequency of the oscillations changed with time, as did the patterns of synchronization. Synchronization may take place among nephrons not immediately adjacent on the surface of the kidney. PMID:21048025

  18. Nephron blood flow dynamics measured by laser speckle contrast imaging.

    PubMed

    Holstein-Rathlou, Niels-Henrik; Sosnovtseva, Olga V; Pavlov, Alexey N; Cupples, William A; Sorensen, Charlotte Mehlin; Marsh, Donald J

    2011-02-01

    Tubuloglomerular feedback (TGF) has an important role in autoregulation of renal blood flow and glomerular filtration rate (GFR). Because of the characteristics of signal transmission in the feedback loop, the TGF undergoes self-sustained oscillations in single-nephron blood flow, GFR, and tubular pressure and flow. Nephrons interact by exchanging electrical signals conducted electrotonically through cells of the vascular wall, leading to synchronization of the TGF-mediated oscillations. Experimental studies of these interactions have been limited to observations on two or at most three nephrons simultaneously. The interacting nephron fields are likely to be more extensive. We have turned to laser speckle contrast imaging to measure the blood flow dynamics of 50-100 nephrons simultaneously on the renal surface of anesthetized rats. We report the application of this method and describe analytic techniques for extracting the desired data and for examining them for evidence of nephron synchronization. Synchronized TGF oscillations were detected in pairs or triplets of nephrons. The amplitude and the frequency of the oscillations changed with time, as did the patterns of synchronization. Synchronization may take place among nephrons not immediately adjacent on the surface of the kidney.

  19. The computational modeling of supercritical carbon dioxide flow in solid wood material

    NASA Astrophysics Data System (ADS)

    Gething, Brad Allen

    , respectively. This sensitivity requires that the input parameters, principally permeability, be relatively accurate to evaluate the appropriateness of the phenomenological relationships of the computational flow model. Providing this stipulation, it was observed that below the region of transition from CO2 gas to supercritical fluid, the computational flow model has the potential to predict flow accurately. However, above the transition region, the model does not fully account for the physics of the flow process, resulting in prediction inaccuracy. One potential cause for the loss of prediction accuracy in the supercritical region was attributed to a dynamic change in permeability that is likely caused by an interaction between the flowing SC CO2 and the wood material. Furthermore, a hysteresis was observed between the pressurization and depressurization stages of treatment, which cannot be explained by the current flow model. If greater accuracy in the computational flow model is desired, a more complex approach to the model is necessary, which would include non-constant input parameters of temperature and permeability. Furthermore, the implications of a multi-scale methodology for the flow model were explored from a qualitative standpoint.

  20. Cascading dynamics with local weighted flow redistribution in interdependent networks

    NASA Astrophysics Data System (ADS)

    Qiu, Yuzhuo

    2013-07-01

    We study load cascading dynamics in a system composed of coupled interdependent networks while adopting a local weighted flow redistribution rule. We find that when the intra- or inter-connectivity increases, robustness against the cascade of load failures in the symmetrically coupled interdependent networks increases. In addition, when a failed link has to first split its flow asymmetrically to its neighbouring link groups according to the link types, even though there exists an optimal split, the robustness is lowered in contrast with the non-split situation. Furthermore, the optimal weighting mechanism in an isolated network no longer holds in interdependent networks. Finally, robustness against the cascade of load failures is not guaranteed to increase by making the distribution of the degree of intra-connectivity broader. We confirm these phenomena by theoretical analysis based on mean-field theory. Our findings might have great implications for preventing load-failure-induced local cascades in symmetrically coupled interdependent networks.

  1. Modeling the dynamical sinking of biogenic particles in oceanic flow

    NASA Astrophysics Data System (ADS)

    Monroy, Pedro; Hernández-García, Emilio; Rossi, Vincent; López, Cristóbal

    2017-06-01

    We study the problem of sinking particles in a realistic oceanic flow, with major energetic structures in the mesoscale, focussing on the range of particle sizes and densities appropriate for marine biogenic particles. Our aim is to evaluate the relevance of theoretical results of finite size particle dynamics in their applications in the oceanographic context. By using a simplified equation of motion of small particles in a mesoscale simulation of the oceanic velocity field, we estimate the influence of physical processes such as the Coriolis force and the inertia of the particles, and we conclude that they represent negligible corrections to the most important terms, which are passive motion with the velocity of the flow, and a constant added vertical velocity due to gravity. Even if within this approximation three-dimensional clustering of particles can not occur, two-dimensional cuts or projections of the evolving three-dimensional density can display inhomogeneities similar to the ones observed in sinking ocean particles.

  2. Chaotic dynamics of a microswimmer in Poiseuille flow

    NASA Astrophysics Data System (ADS)

    Chacón, Ricardo

    2013-11-01

    The chaotic dynamics of pointlike, spherical particles in cylindrical Poiseuille flow is theoretically characterized and numerically confirmed when their own intrinsic swimming velocity undergoes temporal fluctuations around an average value. Two dimensionless ratios associated with the three significant temporal scales of the problem are identified that fully determine the chaos scenario. In particular, small but finite periodic fluctuations of swimming speed result in chaotic or regular motion depending on the position and orientation of the microswimmer with respect to the flow center line. Remarkably, the spatial extension of chaotic microswimmers is found to depend crucially on the fluctuations' period and amplitude and to be highly sensitive to the Fourier spectrum of the fluctuations. This has implications for the design of artificial microswimmers.

  3. Chaotic dynamics of a microswimmer in Poiseuille flow.

    PubMed

    Chacón, Ricardo

    2013-11-01

    The chaotic dynamics of pointlike, spherical particles in cylindrical Poiseuille flow is theoretically characterized and numerically confirmed when their own intrinsic swimming velocity undergoes temporal fluctuations around an average value. Two dimensionless ratios associated with the three significant temporal scales of the problem are identified that fully determine the chaos scenario. In particular, small but finite periodic fluctuations of swimming speed result in chaotic or regular motion depending on the position and orientation of the microswimmer with respect to the flow center line. Remarkably, the spatial extension of chaotic microswimmers is found to depend crucially on the fluctuations' period and amplitude and to be highly sensitive to the Fourier spectrum of the fluctuations. This has implications for the design of artificial microswimmers.

  4. Molecular dynamics simulation of ion flows around microparticles

    NASA Astrophysics Data System (ADS)

    Piel, Alexander

    2017-03-01

    The interaction of an ion flow with charged microparticles is studied by simulations with the molecular asymmetric dynamics (MAD) code. This code treats positive ions as "Yukawa particles" that are shielded by thermal electrons while the microparticle is assumed unshielded. The code is described and critically compared with results from published particle-in-cell simulations of other authors. As an application, the MAD code is used for a systematic study of the repulsive and ion-wake induced attractive forces in a particle pair. It is shown that the combined wake charges of a vertically, flow-aligned particle pair do not lead to a net attractive force. When the lower particle is shifted sidewards, a horizontal restoring force is found, which gives harmonic confinement for small displacements and a decreasing attraction force for a large distance.

  5. Dynamics of a polyelectrolyte in simple shear flow

    NASA Astrophysics Data System (ADS)

    Jayasree, Kandiledath; Kumar Manna, Raj; Banerjee, Debapriya; Kumar, P. B. Sunil

    2013-12-01

    The configurational dynamics of a polyelectrolyte (PE), subjected to a simple shear flow, is studied using Brownian dynamics (BD) and Dissipative Particle Dynamics (DPD) simulations of a bead-spring model with explicit counterions. We explore the effect of counterion condensation on the tumbling and extension of PEs by varying the shear rates for a range of values of the electrostatic coupling parameter A (which is defined as the ratio of the Bjerrum length to the size of the monomer). In all cases, the power spectrum of Rs(t) (which characterizes the projected length of the PE in the flow direction as a function of time) exhibits a power law decay at high frequencies, similar to that for a dumbbell in shear flow. For lower values of A (A ˜ 2), the tumbling of the PE is periodic and is always associated with folding and stretching, which is in contrast to the oscillatory transition between the extended and globular states seen at higher values of A (A ˜ 15). We observe that for A ˜ 2 the tumbling frequency decreases and the average tumbling time increases with hydrodynamic interaction (HI). For A > 15, we observe a critical shear rate {dot{γ }}_c below which there is considerable counterion condensation and the PE remains in the globular state with a structure akin to that of a neutral polymer in poor solvent. The {dot{γ }}_c and the behavior of the PE above the critical shear rate are dependent on the HI. For a given shear rate, when there is considerable condensed counterion fluctuation, the PE extends as a whole and then collapses by the formation of folds with no observable periodicity in tumbling. When the condensed counterion fluctuations are suppressed, the polymer exhibits periodic tumbling. Simulation artifacts resulting from the implicit nature of the solvent and that due to boundary conditions are discussed by comparing the BD results with that obtained from the DPD simulations incorporating Ewald summation for electrostatics.

  6. Channel Geometry and Flood Flows: Quantifying over-bank flow dynamics during high-flow events in North Carolina's floodplains

    NASA Astrophysics Data System (ADS)

    Lovette, J. P.; Duncan, J. M.; Vimal, S.; Band, L. E.

    2015-12-01

    Natural riparian areas play numerous roles in the maintenance and improvement of stream water quality. Both restoration of riparian areas and improvement of hydrologic connectivity to the stream are often key goals of river restoration projects. These management actions are designed to improve nutrient removal by slowing and treating overland flow delivered from uplands and by storing, treating, and slowly releasing streamwater from overbank inundation during flood events. A major question is how effective this storage of overbank flow is at treating streamwater based on the cumulative time stream discharge at a downstream location has spent in shallower, slower overbank flow. The North Carolina Floodplain Mapping Program maintains a detailed statewide Flood Risk Information System (FRIS) using HEC-RAS modeling, lidar, and detailed surveyed river cross-sections. FRIS provides extensive information regarding channel geometry on approximately 39,000 stream reaches (a slightly coarser spatial resolution than the NHD+v2 dataset) with tens of cross-sections for each reach. We use this FRIS data to calculate volume and discharge from floodplain riparian areas separately from in-channel flow during overbank events. Preliminary results suggest that a small percentage of total annual discharge interacts with the full floodplain extent along a stream reach due to the infrequency of overbank flow events. However, with the significantly different physical characteristics of the riparian area when compared to the channel itself, this overbank flow can provide unique services to water quality. Our project aims to use this information in conjunction with data from the USGS SPARROW program to target non-point source hotspots of Nitrogen and Phosphorus addition and removal. By better understanding the flow dynamics within riparian areas during high flow events, riparian restoration projects can be carried out with improved efficacy.

  7. Dynamic behavior of particulate/porous energetic materials

    NASA Astrophysics Data System (ADS)

    Nesterenko, Vitali

    2011-06-01

    Dynamic behavior of particulate/porous energetic materials in a broad range of impact conditions and types of deformation (shock, shear) will be discussed. Samples of these materials were fabricated using Cold Isostatic Pressing, sintering and Hot Isostatic Pressing with and without vacuum encapsulation. The current interest in these materials is due to the combination of their high strength with energy efficiency under critical conditions of mechanical deformation. They may exhibit high compressive and tensile strength with the ability to bulk distributed fracture resulting in a small size reactive fragments and possible reaction on later stages. The results of dynamic deformation and fragmentation of these materials in conditions of low velocity (10 m/s), high energy impact, under localized deformation in single and multiple shear bands generated using explosively driven Thick Walled Cylinder method will be discussed. The mechanical properties of these materials are highly sensitive to mesostructure. For example, a dynamic strength of Al-W composites with fine W particles is significantly larger than the strength of composite with the coarse W particles at the same porosity. Morphology of W inclusions had a strong effect on dynamic strength. Samples with W wires arranged in axial direction with the same volume content of components had a highest dynamic strength. Porosity in these materials can provide a strain hardening mechanism effect due to in situ densification which was observed experimentally for cold isostatically pressed Al and Al-coarse W powders. Experimental results will be compared with available numerical data. The support for this project provided by ONR MURI N00014-07-1-0740 (Program Officer Dr. Clifford Bedford).

  8. Transverse flow reactor studies of the dynamics of radical reactions

    SciTech Connect

    Macdonald, R.G.

    1993-12-01

    Radical reactions are in important in combustion chemistry; however, little state-specific information is available for these reactions. A new apparatus has been constructed to measure the dynamics of radical reactions. The unique feature of this apparatus is a transverse flow reactor in which an atom or radical of known concentration will be produced by pulsed laser photolysis of an appropriate precursor molecule. The time dependence of individual quantum states or products and/or reactants will be followed by rapid infrared laser absorption spectroscopy. The reaction H + O{sub 2} {yields} OH + O will be studied.

  9. Dielectric barrier plasma dynamics for active control of separated flows

    SciTech Connect

    Roy, Subrata; Singh, K.P.; Gaitonde, Datta V.

    2006-03-20

    The dynamics of separation mitigation with asymmetric dielectric barrier discharges is explored by considering the gas flow past a flat plate at an angle of attack. A self-consistent model utilizing motion of electrons, ions, and neutrals is employed to couple the electric force field to the momentum of the fluid. The charge separation and concomitant electric field yield a time-averaged body force which is oriented predominantly downstream, with a smaller transverse component towards the wall. This induces a wall-jet-like feature that effectively eliminates the separation bubble. The impact of several geometric and electrical operating parameters is elucidated.

  10. Evaluation of the intranasal flow field through computational fluid dynamics.

    PubMed

    Hildebrandt, Thomas; Goubergrits, Leonid; Heppt, Werner Johannes; Bessler, Stephan; Zachow, Stefan

    2013-04-01

    A reliable and comprehensive assessment of nasal breathing is problematic and still a common issue in rhinosurgery. Impairments of nasal breathing need an objective approach. In this regard, currently rhinomanometry is the only standard diagnostic tool available but has various limitations. However, in the last decade, computational fluid dynamics (CFD) has become a promising method in facing the challenge of qualifying nasal breathing. This article presents use of CFD with a symptom-free subject and a symptomatic patient. Thereby, certain flow field features and changes before and after surgery were investigated. Moreover, the study outlines suggestions for concrete rhinologic CFD applications. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

  11. Dislocation dynamics: simulation of plastic flow of bcc metals

    SciTech Connect

    Lassila, D H

    2001-02-20

    This is the final report for the LDRD strategic initiative entitled ''Dislocation Dynamic: Simulation of Plastic Flow of bcc Metals'' (tracking code: 00-SI-011). This report is comprised of 6 individual sections. The first is an executive summary of the project and describes the overall project goal, which is to establish an experimentally validated 3D dislocation dynamics simulation. This first section also gives some information of LLNL's multi-scale modeling efforts associated with the plasticity of bcc metals, and the role of this LDRD project in the multiscale modeling program. The last five sections of this report are journal articles that were produced during the course of the FY-2000 efforts.

  12. Global dynamics of zooplankton and harmful algae in flowing habitats

    NASA Astrophysics Data System (ADS)

    Hsu, Sze-Bi; Wang, Feng-Bin; Zhao, Xiao-Qiang

    This paper is devoted to the study of two advection-dispersion-reaction models arising from the dynamics of harmful algae and zooplankton in flowing-water habitats where a main channel is coupled to a hydraulic storage zone, representing an ensemble of fringing coves on the shoreline. For the system modeling the dynamics of algae and their toxin that contains little limiting nutrient, we establish a threshold type result on the global attractivity in terms of the basic reproduction ratio for algae. For the model with zooplankton that eat the algae and are inhibited by the toxin produced by algae, we show that there exists a coexistence steady state and the zooplankton is uniformly persistent provided that two basic reproduction ratios for algae and zooplankton are greater than unity.

  13. Unified power flow controller: modeling and dynamic characteristic

    NASA Astrophysics Data System (ADS)

    Bach, D. H.; Loc, H. D.

    2005-12-01

    Unified power flow controller (UPFC) consists two converters. There are three purposes of this paper, firstly to illustrate the UPFC device based VSC designs, then to describe a decoupling method the UPFC's controller into two separate control systems of the shunt and the series converters respectively in realizing an appropriate coordination between them. Finally, using the Matlab tool to build a discrete simulator for the UPFC with 12 pulse converters. The simulation results show that the developed UPFC model is reflected the static and dynamic characteristics of the UPFC. The harmonics of the output of the model were analyzed. Using the simple power system with UPFC as an example, the dynamics characteristics were studied. The fault status of the system with UPFC was analyzed too.

  14. Assessing computer waste generation in Chile using material flow analysis.

    PubMed

    Steubing, Bernhard; Böni, Heinz; Schluep, Mathias; Silva, Uca; Ludwig, Christian

    2010-03-01

    The quantities of e-waste are expected to increase sharply in Chile. The purpose of this paper is to provide a quantitative data basis on generated e-waste quantities. A material flow analysis was carried out assessing the generation of e-waste from computer equipment (desktop and laptop PCs as well as CRT and LCD-monitors). Import and sales data were collected from the Chilean Customs database as well as from publications by the International Data Corporation. A survey was conducted to determine consumers' choices with respect to storage, re-use and disposal of computer equipment. The generation of e-waste was assessed in a baseline as well as upper and lower scenarios until 2020. The results for the baseline scenario show that about 10,000 and 20,000 tons of computer waste may be generated in the years 2010 and 2020, respectively. The cumulative e-waste generation will be four to five times higher in the upcoming decade (2010-2019) than during the current decade (2000-2009). By 2020, the shares of LCD-monitors and laptops will increase more rapidly replacing other e-waste including the CRT-monitors. The model also shows the principal flows of computer equipment from production and sale to recycling and disposal. The re-use of computer equipment plays an important role in Chile. An appropriate recycling scheme will have to be introduced to provide adequate solutions for the growing rate of e-waste generation. Copyright 2009 Elsevier Ltd. All rights reserved.

  15. Dynamics of Lipid Bilayer Vesicles in Viscous Flows

    NASA Astrophysics Data System (ADS)

    Schwalbe, Jonathan; Vlahovska, Petia; Miksis, Michael J.

    2008-11-01

    An analytical theory is developed to describe the dynamics of a closed lipid bilayer membrane (vesicle) in a general linear viscous flow. The dynamics of the membrane is governed by the Stokes equations in the fluid plus the normal and tangential stress condition along the bilayer interface. The effects of the membrane fluidity, incompressibility and resistance to bending are taken into account. The model is a generalization of the work on planar membranes by Seifert and Langer (Europhys. Lett. vol. 23, 71, 1993), which accounted for the variations in lipid density along both leaflets of the bilayer. Considering a nearly spherical vesicle, a perturbation solution is derived. The leading order analysis results in a nonlinear coupled system of equations for the dynamics of the shape and the mean lipid density difference between the inner and outer monolayer. Multiple solution states are found as a function of viscosity ratio and the monolayer slip coefficient. The dynamics and stability of these solutions is discussed. Comparisons are made to previous works based on the minimal curvature model which did not consider variable lipid density.

  16. Research in Structures, Structural Dynamics and Materials, 1990

    NASA Technical Reports Server (NTRS)

    Barthelemy, Jean-Francois M. (Compiler); Noor, Ahmed K. (Compiler)

    1990-01-01

    The Structural Dynamics and Materials (SDM) Conference was held on April 2 to 4, 1990 in Long Beach, California. This publication is a compilation of presentations of the work-in-progress sessions and does not contain papers from the regular sessions since those papers are published by AIAA in the conference proceedings.

  17. Effect of available entrainable material on a viscous gravity current including run-out characteristics and internal flow properties

    NASA Astrophysics Data System (ADS)

    Bates, Belinda; Ancey, Christophe

    2013-04-01

    It has long been accepted that entrainment of loose material by geophysical gravity flows such as dense snow avalanches and debris flows may change their behaviour significantly. Run-out distances and bulk-flow velocities are notable examples of susceptible behaviours. It is still disputed how this has an effect but it has been noted that the availability of entrainable material is a principal parameter. Laboratory and numerical results are studied side-by-side to demonstrate the effects of a finite erodible bed of varying length and depth, which is placed in the path of a flowing gravity current. Both the current and the bed are composed of the same material. Natural geophysical flows are simulated as idealized viscous gravity currents at zero degrees inclination in order to study the link between the internal dynamics and the bulk features in the simplest case. In the laboratory, a PIV configuration using a laser sheet allows the visualization of a vertical stream-wise cross section of the flow in the transition region from rigid to erodible bed, far from the side-walls. This allows the study of the velocity field within the cross-section of the flow in the entrainable region. Run-out speeds and distances are measured after the current exits the erodible bed and flows over a rigid base once more. A relationship is sought between the released volume, the erodible bed dimensions (that is, length and depth) and the run-out characteristics of the flow. This bulk run-out behaviour is investigated with reference to the internal flow dynamics as measured by PIV. This work is supplemented by results obtained modelling the same system using the open source CFD software OpenFOAM. We were able to track the front of the current during the flow and found that even the presence of a shallow entrainable bed (3 mm deep) significantly advanced the run-out front compared to the no-bed case. A further increase in bed depth led to a slight increase in run-out. The length of the bed

  18. Dynamic characterization and modeling of potting materials for electronics assemblies

    NASA Astrophysics Data System (ADS)

    Joshi, Vasant S.; Lee, Gilbert F.; Santiago, Jaime R.

    2017-01-01

    Prediction of survivability of encapsulated electronic components subject to impact relies on accurate modeling, which in turn needs both static and dynamic characterization of individual electronic components and encapsulation material to generate reliable material parameters for a robust material model. Current focus is on potting materials to mitigate high rate loading on impact. In this effort, difficulty arises in capturing one of the critical features characteristic of the loading environment in a high velocity impact: multiple loading events coupled with multi-axial stress states. Hence, potting materials need to be characterized well to understand its damping capacity at different frequencies and strain rates. An encapsulation scheme to protect electronic boards consists of multiple layers of filled as well as unfilled polymeric materials like Sylgard 184 and Trigger bond Epoxy # 20-3001. A combination of experiments conducted for characterization of materials used Split Hopkinson Pressure Bar (SHPB), and dynamic material analyzer (DMA). For material which behaves in an ideal manner, a master curve can be fitted to Williams-Landel-Ferry (WLF) model. To verify the applicability of WLF model, a new temperature-time shift (TTS) macro was written to compare idealized temperature shift factor with experimental incremental shift factor. Deviations can be readily observed by comparison of experimental data with the model fit to determine if model parameters reflect the actual material behavior. Similarly, another macro written for obtaining Ogden model parameter from Hopkinson Bar tests can readily indicate deviations from experimental high strain rate data. Experimental results for different materials used for mitigating impact, and ways to combine data from DMA and Hopkinson bar together with modeling refinements are presented.

  19. Flow Dynamics and Plasma Heating of Spheromaks in SSX

    NASA Astrophysics Data System (ADS)

    Brown, M. R.; Cothran, C. D.; Cohen, D. H.; Horwitz, J.; Chaplin, V.

    2008-06-01

    We report several new experimental results related to flow dynamics and heating from single dipole-trapped spheromaks and spheromak merging studies at SSX. Single spheromaks (stabilized with a pair of external coils, see Brown, Phys. Plasmas 13 102503 (2006)) and merged FRC-like configurations (see Brown, Phys. Plasmas 13, 056503 (2006)) are trapped in our prolate ( R = 0.2 m, L = 0.6 m) copper flux conserver. Local spheromak flow is studied with two Mach probes ( r 1 ≤ ρ i , r 2 ≥ ρ i ) calibrated by time-of-flight with a fast set of magnetic probes at the edge of the device. Both Mach probes feature six ion collectors housed in a boron nitride sheath. The larger Mach probe will ultimately be used in the MST reversed field pinch. Line averaged flow is measured by ion Doppler spectroscopy (IDS) at the midplane. The SSX IDS instrument measures with 1 μ s or better time resolution the width and Doppler shift of the C III impurity (H plasma) 229.7 nm line to determine the temperature and line-averaged flow velocity (see Cothran, RSI 77, 063504 (2006)). We find axial flows up to 100 km/s during formation of the dipole trapped spheromak. Flow returns at the wall to form a large vortex. Recent high-resolution IDS velocity measurements during spheromak merging show bi-directional outflow jets at ±40 km/s (nearly the Alfvén speed). We also measure T i ≥ 80 eV and T e ≥ 20 eV during spheromak merging events after all plasma facing surfaces are cleaned with helium glow discharge conditioning. Transient electron heating is inferred from bursts on a four-channel soft x-ray array. The spheromaks are also characterized by a suite of magnetic probe arrays for magnetic structure B(r,t), and interferometry for n e . Finally, we are designing a new oblate, trapezoidal flux conserver for FRC studies. Equilibrium and dynamical simulations suggest that a tilt-stable, oblate FRC can be formed by spheromak merging in the new flux conserver.

  20. Hydrogels in Healthcare: From Static to Dynamic Material Microenvironments.

    PubMed

    Kirschner, Chelsea M; Anseth, Kristi S

    2013-02-01

    Advances in hydrogel design have revolutionized the way biomaterials are applied to address biomedical needs. Hydrogels were introduced in medicine over 50 years ago and have evolved from static, bioinert materials to dynamic, bioactive microenvironments, which can be used to direct specific biological responses such as cellular ingrowth in wound healing or on-demand delivery of therapeutics. Two general classes of mechanisms, those defined by the user and those dictated by the endogenous cells and tissues, can control dynamic hydrogel microenvironments. These highly tunable materials have provided bioengineers and biological scientists with new ways to not only treat patients in the clinic but to study the fundamental cellular responses to engineered microenvironments as well. Here, we provide a brief history of hydrogels in medicine and follow with a discussion of the synthesis and implementation of dynamic hydrogel microenvironments for healthcare-related applications.

  1. Hydrogels in Healthcare: From Static to Dynamic Material Microenvironments

    PubMed Central

    Kirschner, Chelsea M.; Anseth, Kristi S.

    2013-01-01

    Advances in hydrogel design have revolutionized the way biomaterials are applied to address biomedical needs. Hydrogels were introduced in medicine over 50 years ago and have evolved from static, bioinert materials to dynamic, bioactive microenvironments, which can be used to direct specific biological responses such as cellular ingrowth in wound healing or on-demand delivery of therapeutics. Two general classes of mechanisms, those defined by the user and those dictated by the endogenous cells and tissues, can control dynamic hydrogel microenvironments. These highly tunable materials have provided bioengineers and biological scientists with new ways to not only treat patients in the clinic but to study the fundamental cellular responses to engineered microenvironments as well. Here, we provide a brief history of hydrogels in medicine and follow with a discussion of the synthesis and implementation of dynamic hydrogel microenvironments for healthcare-related applications. PMID:23929381

  2. Overhauser dynamic nuclear polarization amplification of NMR flow imaging.

    PubMed

    Lingwood, Mark D; Sederman, Andrew J; Mantle, Mick D; Gladden, Lynn F; Han, Songi

    2012-03-01

    We describe the first study comparing the ability of phase shift velocity imaging and Overhauser dynamic nuclear polarization (DNP)-enhanced imaging to generate contrast for visualizing the flow of water. Prepolarization of water by the Overhauser DNP mechanism is performed in the 0.35T fringe field of an unshielded 2.0T non-clinical MRI magnet, followed by the rapid transfer of polarization-enhanced water to the 2.0T imaging location. This technique, previously named remotely enhanced liquids for image contrast (RELIC), produces a continuous flow of hyperpolarized water and gives up to an -8.2-fold enhanced signal within the image with respect to thermally polarized signal at 2.0T. Using flow through a cylindrical expansion phantom as a model system, spin-echo intensity images with DNP are compared to 3D phase shift velocity images to illustrate the complementary information available from the two techniques. The spin-echo intensity images enhanced with DNP show that the levels of enhancement provide an estimate of the transient propagation of flow, while the phase shift velocity images quantitatively measure the velocity of each imaging voxel. Phase shift velocity images acquired with and without DNP show that DNP weights velocity values towards those of the inflowing (DNP-enhanced) water, while velocity images without DNP more accurately reflect the average steady-state velocity of each voxel. We conclude that imaging with DNP prepolarized water better captures the transient path of water shortly after injection, while phase shift velocity imaging is best for quantifying the steady-state flow of water throughout the entire phantom. Copyright © 2012 Elsevier Inc. All rights reserved.

  3. Analysis of flow dynamics in right ventricular outflow tract.

    PubMed

    Berdajs, Denis A; Mosbahi, Selim; Charbonnier, Dominique; Hullin, Roger; von Segesser, Ludwig K

    2015-07-01

    The mechanism behind early graft failure after right ventricular outflow tract (RVOT) reconstruction is not fully understood. Our aim was to establish a three-dimensional computational fluid dynamics (CFD) model of RVOT to investigate the hemodynamic conditions that may trigger the development of intimal hyperplasia and arteriosclerosis. Pressure, flow, and diameter at the RVOT, pulmonary artery (PA), bifurcation of the PA, and left and right PAs were measured in 10 normal pigs with a mean weight of 24.8 ± 0.78 kg. Data obtained from the experimental scenario were used for CFD simulation of pressure, flow, and shear stress profile from the RVOT to the left and right PAs. Using experimental data, a CFD model was obtained for 2.0 and 2.5-L/min pulsatile inflow profiles. In both velocity profiles, time and space averaged in the low-shear stress profile range from 0-6.0 Pa at the pulmonary trunk, its bifurcation, and at the openings of both PAs. These low-shear stress areas were accompanied to high-pressure regions 14.0-20.0 mm Hg (1866.2-2666 Pa). Flow analysis revealed a turbulent flow at the PA bifurcation and ostia of both PAs. Identified local low-shear stress, high pressure, and turbulent flow correspond to a well-defined trigger pattern for the development of intimal hyperplasia and arteriosclerosis. As such, this real-time three-dimensional CFD model may in the future serve as a tool for the planning of RVOT reconstruction, its analysis, and prediction of outcome. Copyright © 2015 Elsevier Inc. All rights reserved.

  4. Cellular Manufacturing System with Dynamic Lot Size Material Handling

    NASA Astrophysics Data System (ADS)

    Khannan, M. S. A.; Maruf, A.; Wangsaputra, R.; Sutrisno, S.; Wibawa, T.

    2016-02-01

    Material Handling take as important role in Cellular Manufacturing System (CMS) design. In several study at CMS design material handling was assumed per pieces or with constant lot size. In real industrial practice, lot size may change during rolling period to cope with demand changes. This study develops CMS Model with Dynamic Lot Size Material Handling. Integer Linear Programming is used to solve the problem. Objective function of this model is minimizing total expected cost consisting machinery depreciation cost, operating costs, inter-cell material handling cost, intra-cell material handling cost, machine relocation costs, setup costs, and production planning cost. This model determines optimum cell formation and optimum lot size. Numerical examples are elaborated in the paper to ilustrate the characterictic of the model.

  5. Evaluation of Local Flow Conditions in Jailed Side Branch Lesions Using Computational Fluid Dynamics

    PubMed Central

    Na, Sang-Hoon; Kim, Jeong Chul; Yang, Han-Mo; Park, Kyung-Woo; Kang, Hyun-Jae; Kim, Hyo-Soo; Oh, Byung-Hee; Park, Young-Bae

    2011-01-01

    Background and Objectives Lesions of vascular bifurcation and their treatment outcomes have been evaluated by anatomical and physiological methods, such as intravascular ultrasound and fractional flow reserve (FFR). However, local changes in flow dynamics in lesions of bifurcation have not been well evaluated. This study aimed at evaluating changes in the local flow patterns of bifurcation lesions. Materials and Methods Eight (n=8) representative simulation-models were constructed: 1 normal bifurcation, 5 main-branch (MB) stenting models with various side-branch (SB) stenoses (ostial or non-ostial 75% diameter stenosis with 1- or 2-cm lesion lengths, ostial 75% diameter stenosis caused by carina shift), and 2 post-kissing models (no or 50% SB residual stenosis). Pressure, velocity, and wall shear stress (WSS) profiles around the bifurcation sites were investigated using computational fluid dynamics. Results Post-stenting models revealed significant pressure drop in the SB (FFR<0.75), excluding the carina shift model (FFR=0.89). In the post-kissing models, there was no significant pressure drop. All post-stenting models revealed eccentric low velocity flow patterns and areas of low WSS, primarily in the lateral wall on distal MB. Post-kissing angioplasty improved pressure drop in the SB but resulted in alteration of flow distribution in the MB. In the carina shift model, kissing ballooning resulted in deteriorated local flow conditions due to increased area of low velocity and WSS. Conclusion This study suggests that the most commonly used bifurcation intervention strategy may cause local flow disturbances, which may partially explain high restenosis and event rates in patients with bifurcation lesions. PMID:21430994

  6. Frictional Fluid Dynamics and Plug Formation in Multiphase Millifluidic Flow

    NASA Astrophysics Data System (ADS)

    Dumazer, Guillaume; Sandnes, Bjørnar; Ayaz, Monem; Mâløy, Knut Jørgen; Flekkøy, Eirik Grude

    2016-07-01

    We study experimentally the flow and patterning of a granular suspension displaced by air inside a narrow tube. The invading air-liquid interface accumulates a plug of granular material that clogs the tube due to friction with the confining walls. The gas percolates through the static plug once the gas pressure exceeds the pore capillary entry pressure of the packed grains, and a moving accumulation front is reestablished at the far side of the plug. The process repeats, such that the advancing interface leaves a trail of plugs in its wake. Further, we show that the system undergoes a fluidization transition—and complete evacuation of the granular suspension—when the liquid withdrawal rate increases beyond a critical value. An analytical model of the stability condition for the granular accumulation predicts the flow regime.

  7. Low frequency sound attenuation in a flow duct using a thin slow sound material.

    PubMed

    Aurégan, Yves; Farooqui, Maaz; Groby, Jean-Philippe

    2016-05-01

    A thin subwavelength material that can be flush mounted in a duct and that gives an attenuation band at low frequencies in air flow channels is presented. To decrease the material thickness, the sound is slowed in the material using folded side branch tubes. The impedance of the material is compared to the optimal value given by the Cremer condition, which can differ greatly from the air characteristic impedance. Grazing flow on this material increases the losses at the interface between the flow and the material.

  8. Dynamics of Motorized Vehicle Flow under Mixed Traffic Circumstance

    NASA Astrophysics Data System (ADS)

    Guo, Hong-Wei; Gao, Zi-You; Zhao, Xiao-Mei; Xie, Dong-Fan

    2011-04-01

    To study the dynamics of mixed traffic flow consisting of motorized and non-motorized vehicles, a car-following model based on the principle of collision free and cautious driving is proposed. Lateral friction and overlapping driving are introduced to describe the interactions between motorized vehicles and non-motorized vehicles. By numerical simulations, the flux-density relation, the temporal-spatial dynamics, and the velocity evolution are investigated in detail. The results indicate non-motorized vehicles have a significant impact on the motorized vehicle flow and cause the maximum flux to decline by about 13%. Non-motorized vehicles can decrease the motorized vehicle velocity and cause velocity oscillation when the motorized vehicle density is low. Moreover, non-motorized vehicles show a significant damping effect on the oscillating velocity when the density is medium and high, and such an effect weakens as motorized vehicle density increases. The results also stress the necessity for separating motorized vehicles from non-motorized vehicles.

  9. Onset of turbulent mean dynamics in boundary layer flow

    NASA Astrophysics Data System (ADS)

    Hamman, Curtis; Sayadi, Taraneh; Moin, Parviz

    2012-11-01

    Statistical properties of turbulence in low Reynolds number boundary layers are compared. Certain properties are shown to approach an asymptotic state resembling higher Reynolds number flow much earlier during transition than previously thought. This incipient turbulence is less stochastic and more organized than developed turbulence farther downstream, but the mean dynamics and production mechanisms are remarkably similar. The onset of turbulence in our recent simulations is also similar to that observed in the bypass transition of Wu & Moin where continuous freestream turbulence, rather than small-amplitude linear waves, triggers transition. For these inflow disturbances, self-sustaining turbulence occurs rapidly after laminar flow breakdown without requiring a significant development length nor significant randomization. Slight disagreements with FST-induced bypass transition are observed that correlate with the extra strain a turbulent freestream would impose upon the near-wall dynamics. Nevertheless, the turbulence statistics are similar shortly after the skin-friction overshoot independent of upstream receptivity. This early onset of deterministic turbulence provides support for reduced-order modeling of turbulent boundary layers based on non-linear stability mechanisms.

  10. Quasi-3D cytoskeletal dynamics of osteocytes under fluid flow.

    PubMed

    Baik, Andrew D; Lu, X Lucas; Qiu, Jun; Huo, Bo; Hillman, Elizabeth M C; Dong, Cheng; Guo, X Edward

    2010-11-03

    Osteocytes respond to dynamic fluid shear loading by activating various biochemical pathways, mediating a dynamic process of bone formation and resorption. Whole-cell deformation and regional deformation of the cytoskeleton may be able to directly regulate this process. Attempts to image cellular deformation by conventional microscopy techniques have been hindered by low temporal or spatial resolution. In this study, we developed a quasi-three-dimensional microscopy technique that enabled us to simultaneously visualize an osteocyte's traditional bottom-view profile and a side-view profile at high temporal resolution. Quantitative analysis of the plasma membrane and either the intracellular actin or microtubule (MT) cytoskeletal networks provided characterization of their deformations over time. Although no volumetric dilatation of the whole cell was observed under flow, both the actin and MT networks experienced primarily tensile strains in all measured strain components. Regional heterogeneity in the strain field of normal strains was observed in the actin networks, especially in the leading edge to flow, but not in the MT networks. In contrast, side-view shear strains exhibited similar subcellular distribution patterns in both networks. Disruption of MT networks caused actin normal strains to decrease, whereas actin disruption had little effect on the MT network strains, highlighting the networks' mechanical interactions in osteocytes. Copyright © 2010 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  11. Applying uncertainty quantification to multiphase flow computational fluid dynamics

    SciTech Connect

    Gel, A; Garg, R; Tong, C; Shahnam, M; Guenther, C

    2013-07-01

    Multiphase computational fluid dynamics plays a major role in design and optimization of fossil fuel based reactors. There is a growing interest in accounting for the influence of uncertainties associated with physical systems to increase the reliability of computational simulation based engineering analysis. The U.S. Department of Energy's National Energy Technology Laboratory (NETL) has recently undertaken an initiative to characterize uncertainties associated with computer simulation of reacting multiphase flows encountered in energy producing systems such as a coal gasifier. The current work presents the preliminary results in applying non-intrusive parametric uncertainty quantification and propagation techniques with NETL's open-source multiphase computational fluid dynamics software MFIX. For this purpose an open-source uncertainty quantification toolkit, PSUADE developed at the Lawrence Livermore National Laboratory (LLNL) has been interfaced with MFIX software. In this study, the sources of uncertainty associated with numerical approximation and model form have been neglected, and only the model input parametric uncertainty with forward propagation has been investigated by constructing a surrogate model based on data-fitted response surface for a multiphase flow demonstration problem. Monte Carlo simulation was employed for forward propagation of the aleatory type input uncertainties. Several insights gained based on the outcome of these simulations are presented such as how inadequate characterization of uncertainties can affect the reliability of the prediction results. Also a global sensitivity study using Sobol' indices was performed to better understand the contribution of input parameters to the variability observed in response variable.

  12. Quasi-3D Cytoskeletal Dynamics of Osteocytes under Fluid Flow

    PubMed Central

    Baik, Andrew D.; Lu, X. Lucas; Qiu, Jun; Huo, Bo; Hillman, Elizabeth M.C.; Dong, Cheng; Guo, X. Edward

    2010-01-01

    Osteocytes respond to dynamic fluid shear loading by activating various biochemical pathways, mediating a dynamic process of bone formation and resorption. Whole-cell deformation and regional deformation of the cytoskeleton may be able to directly regulate this process. Attempts to image cellular deformation by conventional microscopy techniques have been hindered by low temporal or spatial resolution. In this study, we developed a quasi-three-dimensional microscopy technique that enabled us to simultaneously visualize an osteocyte's traditional bottom-view profile and a side-view profile at high temporal resolution. Quantitative analysis of the plasma membrane and either the intracellular actin or microtubule (MT) cytoskeletal networks provided characterization of their deformations over time. Although no volumetric dilatation of the whole cell was observed under flow, both the actin and MT networks experienced primarily tensile strains in all measured strain components. Regional heterogeneity in the strain field of normal strains was observed in the actin networks, especially in the leading edge to flow, but not in the MT networks. In contrast, side-view shear strains exhibited similar subcellular distribution patterns in both networks. Disruption of MT networks caused actin normal strains to decrease, whereas actin disruption had little effect on the MT network strains, highlighting the networks' mechanical interactions in osteocytes. PMID:21044578

  13. Particle and Blood Cell Dynamics in Oscillatory Flows Final Report

    SciTech Connect

    Juan M. Restrepo

    2008-09-01

    Our aim has been to uncover fundamental aspects of the suspension and dislodgement of particles in wall-bounded oscillatory flows, in flows characterized by Reynolds numbers en- compassing the situation found in rivers and near shores (and perhaps in some industrial processes). Our research tools are computational and our coverage of parameter space fairly broad. Computational means circumvent many complications that make the measurement of the dynamics of particles in a laboratory setting an impractical task, especially on the broad range of parameter space we plan to report upon. The impact of this work on the geophysical problem of sedimentation is boosted considerably by the fact that the proposed calculations can be considered ab-initio, in the sense that little to no modeling is done in generating dynamics of the particles and of the moving fluid: we use a three-dimensional Navier Stokes solver along with straightforward boundry conditions. Hence, to the extent that Navier Stokes is a model for an ideal incompressible isotropic Newtonian fluid, the calculations yield benchmark values for such things as the drag, buoyancy, and lift of particles, in a highly controlled environment. Our approach will be to make measurements of the lift, drag, and buoyancy of particles, by considering progressively more complex physical configurations and physics.

  14. Multi-material incompressible flow simulation using the moment-of-fluid method

    SciTech Connect

    Garimella, R V; Schofield, S P; Lowrie, R B; Swartz, B K; Christon, M A; Dyadechko, V

    2009-01-01

    The Moment-of-Fluid interface reconstruction technique is implemented in a second order accurate, unstructured finite element variable density incompressible Navier-Stokes solver. For flows with multiple materials, MOF significantly outperforms existing first and second order interface reconstruction techniques. For two material flows, the performance of MOF is similar to other interface reconstruction techniques. For strongly driven bouyant flows, the errors in the flow solution dominate and all the interface reconstruction techniques perform similarly.

  15. Theoretical interpretation of abnormal ultrafine-grained material deformation dynamics

    NASA Astrophysics Data System (ADS)

    Borodin, Elijah N.; Mayer, Alexander E.

    2016-02-01

    Some recent experiments with ultrafine-grained metal samples reveal that it has an abnormal mechanical response on the intensive dynamical loading caused by its impact or electron beam irradiations. On the basis of the original plasticity model, which takes into account dislocation slip and grain boundary sliding, we show that this response is usual for such structure. Moreover, our calculations predict an inverse Hall-Petch relation for ultrafine grained metals at extremely high strain rates (above 107 s-1), while the classical low strain rate experiments and molecular dynamic simulations detects such inverse Hall-Petch relation only for nanocrystalline materials. The main outcomes of present work are the described plasticity model and the conclusions that the ultrafine-grained metals (with grains of about 100-200 nm in diameter) has to have maximal dynamic shear strength and it is the most persistent to dynamic spall fracture because of maximal energy dissipation in it.

  16. Effect of flow field and geometry on the dynamic contact angle.

    PubMed

    Lukyanov, A V; Shikhmurzaev, Y D

    2007-05-01

    A number of recent experiments suggest that, at a given wetting speed, the dynamic contact angle formed by an advancing liquid-gas interface with a solid substrate depends on the flow field and geometry near the moving contact line. In the present work, this effect is investigated in the framework of an earlier developed theory that was based on the fact that dynamic wetting is, by its very name, a process of formation of a new liquid-solid interface (newly "wetted" solid surface) and hence should be considered not as a singular problem but as a particular case from a general class of flows with forming or/and disappearing interfaces. The results demonstrate that, in the flow configuration of curtain coating, where a liquid sheet ("curtain") impinges onto a moving solid substrate, the actual dynamic contact angle indeed depends not only on the wetting speed and material constants of the contacting media, as in the so-called slip models, but also on the inlet velocity of the curtain, its height, and the angle between the falling curtain and the solid surface. In other words, for the same wetting speed the dynamic contact angle can be varied by manipulating the flow field and geometry near the moving contact line. The obtained results have important experimental implications: given that the dynamic contact angle is determined by the values of the surface tensions at the contact line and hence depends on the distributions of the surface parameters along the interfaces, which can be influenced by the flow field, one can use the overall flow conditions and the contact angle as a macroscopic multiparametric signal-response pair that probes the dynamics of the liquid-solid interface. This approach would allow one to investigate experimentally such properties of the interface as, for example, its equation of state and the rheological properties involved in the interface's response to an external torque, and would help to measure its parameters, such as the coefficient of

  17. An Experimental Study of Mixing Dynamics in 3D Granular Flows

    NASA Astrophysics Data System (ADS)

    Zaman, Zafir

    Compared with the mixing of fluids, the mixing and segregation of granular materials remains one of the big questions of science. Unlike fluids, granular materials segregate based on differences in particle properties, such as density and size. For 2D granular flows, a dynamical systems framework has been effective in describing regions of mixing and segregation. However, computational and theoretical results are just starting to form a framework for 3D granular flows, such as the bi-axial spherical tumbler (BST) flow. This thesis builds on this emerging framework through a series of experimental studies with theoretical and model support with the goal of better understanding 3D mixing. The first study tests the commonly used assumption in continuum models of granular flow that single axis tumbler flow is two dimensional. Utilizing both surface and destructive subsurface imaging, this study shows that weak 3D deviations occur in the form of an axial drift within single axis tumbler flow of varying material spanwise depth. Afterward, this thesis focuses on the development of a custom-built X-ray imaging system to non-destructively visualize the tumbler subsurface. The second study revisits the axial drift and demonstrates that wall roughness impacts the curvature and overall displacement of particle trajectories throughout the tumbler domain using subsurface particle trajectories provided by the X-ray imaging system. Finally, mixing in the fully 3D BST flow is studied. In particular, 3D persistent mixing barriers that are predicted by the dynamical systems framework are shown to exist. Some barriers are remarkably persistent for as much as 500 protocol iterations despite the presence of collisional diffusion. The structures arise from two competing effects, the cutting and shuffling action of the protocol and the stretching from the flowing layer. The tumbling protocol controls the mixing behavior as well as the types of non-mixing barriers observed. Supplementary

  18. Anisotropic material synthesis by capillary flow in a fluid stripe.

    PubMed

    Hancock, Matthew J; Piraino, Francesco; Camci-Unal, Gulden; Rasponi, Marco; Khademhosseini, Ali

    2011-09-01

    We present a simple bench-top technique to produce centimeter long concentration gradients in biomaterials incorporating soluble, material, and particle gradients. By patterning hydrophilic regions on a substrate, a stripe of prepolymer solution is held in place on a glass slide by a hydrophobic boundary. Adding a droplet to one end of this "pre-wet" stripe causes a rapid capillary flow that spreads the droplet along the stripe to generate a gradient in the relative concentrations of the droplet and pre-wet solutions. The gradient length and shape are controlled by the pre-wet and droplet volumes, stripe thickness, fluid viscosity and surface tension. Gradient biomaterials are produced by crosslinking gradients of prepolymer solutions. Demonstrated examples include a concentration gradient of cells encapsulated in three dimensions (3D) within a homogeneous biopolymer and a constant concentration of cells encapsulated in 3D within a biomaterial gradient exhibiting a gradient in cell spreading. The technique employs coated glass slides that may be purchased or custom made from tape and hydrophobic spray. The approach is accessible to virtually any researcher or student and should dramatically reduce the time required to synthesize a wide range of gradient biomaterials. Moreover, since the technique employs passive mechanisms it is ideal for remote or resource poor settings.

  19. Material Flow for the Intentional Use of Mercury in China.

    PubMed

    Lin, Yan; Wang, Shuxiao; Wu, Qingru; Larssen, Thorjørn

    2016-03-01

    Intentional use of mercury (Hg) is an important contributor to the release of Hg into the environment. This study presents the first inventory of material flow for intentional use of Hg in China. The total amount of Hg used in China increased from 803 ± 95 tons in 2005 to its peak level of 1272 ± 110 tons in 2011. Vinyl chloride monomer (VCM) production is the largest user of Hg, accounting for over 60% of the total demand. As regulations on Hg content in products are tightening globally against the background of the Minamata Convention, the total demand will decrease. Medical devices will likely still use a significant amount of Hg and become the second largest user of Hg if no proactive measures are taken. Significant knowledge gaps exist in China for catalyst recycling sector. Although more than half of the Hg used is recycled, this sector has not drawn enough attention. There are also more than 200 tons of Hg that had unknown fates in 2011; very little information exists related to this issue. Among the final environmental fates, landfill is the largest receiver of Hg, followed by air, water, and soil.

  20. Literature search of publications concerning the prediction of dynamic inlet flow distortion and related topics

    NASA Technical Reports Server (NTRS)

    Schweikhhard, W. G.; Chen, Y. S.

    1983-01-01

    Publications prior to March 1981 were surveyed to determine inlet flow dynamic distortion prediction methods and to catalog experimental and analytical information concerning inlet flow dynamic distortion prediction methods and to catalog experimental and analytical information concerning inlet flow dynamics at the engine-inlet interface of conventional aircraft (excluding V/STOL). The sixty-five publications found are briefly summarized and tabulated according to topic and are cross-referenced according to content and nature of the investigation (e.g., predictive, experimental, analytical and types of tests). Three appendices include lists of references, authors, organizations and agencies conducting the studies. Also, selected materials summaries, introductions and conclusions - from the reports are included. Few reports were found covering methods for predicting the probable maximum distortion. The three predictive methods found are those of Melick, Jacox and Motycka. The latter two require extensive high response pressure measurements at the compressor face, while the Melick Technique can function with as few as one or two measurements.

  1. Potential Vorticity Dynamics and Models of Zonal Flow Formation

    NASA Astrophysics Data System (ADS)

    Hsu, Pei-Chun

    We describe the general theory of anisotropic flow formation in quasi two- dimensional turbulence from the perspective on the potential vorticity (PV) trans- port in real space. The aim is to calculate the vorticity or PV flux. In Chapter 2, the general structure of PV flux is deduced non-perturbatively using two relaxation models: the first is a mean field theory for the dynamics of minimum enstrophy relaxation based on the requirement that the mean flux of PV dissipates total po- tential enstrophy but conserves total fluid kinetic energy. The analyses show that the structure of PV flux has the form of a sum of a positive definite hyper-viscous and a negative or positive viscous flux of PV. Turbulence spreading is shown to be related to PV mixing via the link of turbulence energy flux to PV flux. In the relaxed state, the ratio of the PV gradient to zonal flow velocity is homogenized. This structure of the relaxed state is consistent with PV staircases. The homog- enized quantity sets a constraint on the amplitudes of PV and zonal flow in the relaxed state. The second relaxation model is derived from a joint reflection symmetry principle, which constrains the PV flux driven by the deviation from the self- organized state. The form of PV flux contains a nonlinear convective term in addition to viscous and hyper-viscous terms. The nonlinear convective term, how- ever, can be viewed as a generalized diffusion, on account of the gradient-dependent ballistic transport in avalanche-like systems. For both cases, the detailed transport coefficients can be calculated using perturbation theory in Chapter 3. For a broad turbulence spectrum, a modula- tional calculation of the PV flux gives both a negative viscosity and a positive hyper-viscosity. For a narrow turbulence spectrum, the result of a parametric in- stability analysis shows that PV transport is also convective. In both relaxation and perturbative analyses, it is shown that turbulent PV transport is sensitive to

  2. Multifractal dynamics of turbulent flows in swimming bacterial suspensions.

    PubMed

    Liu, Kuo-An; I, Lin

    2012-07-01

    We experimentally investigate the self-propelled two-dimensional turbulent flows of Escherichia coli suspensions in thin liquid films at two different cell concentrations. It is found that the flow has fluctuating vortices with a broad range of scales and intensities through the nonlinear interaction of the swimming bacteria. Increasing cell concentration increases the total propelling power and the nonlinear interaction. It causes the generation of vortices with larger scale, lower frequency, and higher intensity. It also widens the histograms of the flow velocity and the velocity increment between two spatially separated points with more stretched non-Gaussian tails. From the scaling analysis of the structure function S(q)(r) of the qth moment of the velocity increment between two points with spatial separation r, nonlinear relations between the scaling exponent ζ(q) of S(q)(r) and q are found for both cell concentrations, which manifests the multifractal dynamics. The multifractality can be enhanced by increasing cell concentration.

  3. Space-Time Correlations and Dynamic Coupling in Turbulent Flows

    NASA Astrophysics Data System (ADS)

    He, Guowei; Jin, Guodong; Yang, Yue

    2017-01-01

    Space-time correlation is a staple method for investigating the dynamic coupling of spatial and temporal scales of motion in turbulent flows. In this article, we review the space-time correlation models in both the Eulerian and Lagrangian frames of reference, which include the random sweeping and local straining models for isotropic and homogeneous turbulence, Taylor's frozen-flow model and the elliptic approximation model for turbulent shear flows, and the linear-wave propagation model and swept-wave model for compressible turbulence. We then focus on how space-time correlations are used to develop time-accurate turbulence models for the large-eddy simulation of turbulence-generated noise and particle-laden turbulence. We briefly discuss their applications to two-point closures for Kolmogorov's universal scaling of energy spectra and to the reconstruction of space-time energy spectra from a subset of spatial and temporal signals in experimental measurements. Finally, we summarize the current understanding of space-time correlations and conclude with future issues for the field.

  4. Stochastic Rotation Dynamics simulations of wetting multi-phase flows

    NASA Astrophysics Data System (ADS)

    Hiller, Thomas; Sanchez de La Lama, Marta; Brinkmann, Martin

    2016-06-01

    Multi-color Stochastic Rotation Dynamics (SRDmc) has been introduced by Inoue et al. [1,2] as a particle based simulation method to study the flow of emulsion droplets in non-wetting microchannels. In this work, we extend the multi-color method to also account for different wetting conditions. This is achieved by assigning the color information not only to fluid particles but also to virtual wall particles that are required to enforce proper no-slip boundary conditions. To extend the scope of the original SRDmc algorithm to e.g. immiscible two-phase flow with viscosity contrast we implement an angular momentum conserving scheme (SRD+mc). We perform extensive benchmark simulations to show that a mono-phase SRDmc fluid exhibits bulk properties identical to a standard SRD fluid and that SRDmc fluids are applicable to a wide range of immiscible two-phase flows. To quantify the adhesion of a SRD+mc fluid in contact to the walls we measure the apparent contact angle from sessile droplets in mechanical equilibrium. For a further verification of our wettability implementation we compare the dewetting of a liquid film from a wetting stripe to experimental and numerical studies of interfacial morphologies on chemically structured surfaces.

  5. Retrobulbar blood flow and ophthalmic perfusion in maximum dynamic exercise.

    PubMed

    Kozobolis, Vassilios P; Detorakis, Efstathios T; Konstas, Anastasios G; Achtaropoulos, Athanassios K; Diamandides, Evangelos D

    2008-03-01

    To study the effects of maximum dynamic physical exercise on retrobulbar blood flow and ocular perfusion pressure (OPP). Thirty male subjects undergoing routine periodic medical evaluation were included. All participants underwent cardiac stress test according to a standard protocol. Before the test, the intraocular pressure was measured and colour Doppler imaging was performed with a 7.5 MHz linear probe, to record peak systolic velocity (PSV), end diastolic velocity and resistivity index at the ophthalmic artery (OA), central retinal artery (CRA) and nasal and temporal branches of short posterior ciliary arteries (SPCA). The same measurements were repeated 1 and 30 min after the test. OPP and PSV at the OA were significantly higher at the 1-min interval, compared with the pretest scores (P = 0.01, in both cases), whereas the respective differences on the 30-min interval were statistically not significant. On the contrary, PSV at the CRA and SPCA were not significantly changed on the same intervals. Differences between pretest and post-test scores for end diastolic velocity and resistivity index were statistically not significant for all examined vessels. Maximal physical exercise increases OPP and blood flow at the OA without affecting blood flow at the CRA and SPCA, implying that auto-regulative mechanisms are active in both retinal and choroidal circulations.

  6. Two-dimensional CFD modeling of wave rotor flow dynamics

    NASA Technical Reports Server (NTRS)

    Welch, Gerard E.; Chima, Rodrick V.

    1994-01-01

    A two-dimensional Navier-Stokes solver developed for detailed study of wave rotor flow dynamics is described. The CFD model is helping characterize important loss mechanisms within the wave rotor. The wave rotor stationary ports and the moving rotor passages are resolved on multiple computational grid blocks. The finite-volume form of the thin-layer Navier-Stokes equations with laminar viscosity are integrated in time using a four-stage Runge-Kutta scheme. Roe's approximate Riemann solution scheme or the computationally less expensive advection upstream splitting method (AUSM) flux-splitting scheme is used to effect upwind-differencing of the inviscid flux terms, using cell interface primitive variables set by MUSCL-type interpolation. The diffusion terms are central-differenced. The solver is validated using a steady shock/laminar boundary layer interaction problem and an unsteady, inviscid wave rotor passage gradual opening problem. A model inlet port/passage charging problem is simulated and key features of the unsteady wave rotor flow field are identified. Lastly, the medium pressure inlet port and high pressure outlet port portion of the NASA Lewis Research Center experimental divider cycle is simulated and computed results are compared with experimental measurements. The model accurately predicts the wave timing within the rotor passages and the distribution of flow variables in the stationary inlet port region.

  7. Dynamics of virus spread in the presence of fluid flow.

    PubMed

    Anekal, Samartha G; Zhu, Ying; Graham, Michael D; Yin, John

    2009-12-01

    The dynamics of viral infection spread, whether in laboratory cultures or in naturally infected hosts, reflects a coupling of biological and physical processes that remain to be fully elucidated. Biological processes include the kinetics of virus growth in infected cells while physical processes include transport of virus progeny from infected cells, where they are produced, to susceptible cells, where they initiate new infections. Mechanistic models of infection spread have been widely developed for systems where virus growth is coupled with transport of virus particles by diffusion, but they have yet to be developed for systems where viruses move under the influence of fluid flows. Recent experimental observations of flow-enhanced infection spread in laboratory cultures motivate here the development of initial continuum and discrete virus-particle models of infection spread. The magnitude of a dimensionless group, the Damköhler number, shows how parameters that characterize particle adsorption to cells, strain rates that reflect flow profiles, and diffusivities of virus particles combine to influence the spatial pattern of infection spread.

  8. A multiscale model for nanoparticle binding dynamics under shear flow

    NASA Astrophysics Data System (ADS)

    Liu, Yaling; Tan, Jifu; Nguyen, Kytai

    2011-03-01

    Nanomedicine poses a new frontier in medical technology with the advantages of targeted delivery and patient specific design. In applications of nanoparticle targeted drug delivery, the delivery efficiency is controlled by the physical properties of the nanoparticle such as its size, shape, ligand density, as well as external environmental conditions such as blood flow rate, blood vessel diameter. Proper drug dosage choice relies on determination of the attachment and detachment rates of the nanoparticles at the active region and the understanding of the complex process of targeted drug delivery. A few particulate models have been proposed to study the adhesion probability of individual spherical or non-spherical nanoparticles. Meanwhile, continuum convection-diffusion-reaction models have been widely used to calculate the drug concentration, which usually assumes specific binding and de-binding constants. However, there has not been any study that links the particulate level nanoparticle size and shape information to the system level bounded particle concentration. A hybrid particle binding dynamics and continuum convection-diffusion-reaction model is presented to study the effect of shear flow rate and particle size on binding efficiency. The simulated concentration of bounded nanoparticles agrees well with experimental results in flow chamber studies.

  9. Chaotic Dynamics of Articulated Cylinders in Confined Axial Flow

    NASA Astrophysics Data System (ADS)

    Païdoussis, M. P.; Botez, R. M.

    1993-10-01

    A study is presented of the dynamics of an articulated system of cylinders in confined axial flow. The Articulated system is composed of rigid cylindrical segments, interconnected by rotational springs; it is cantilevered, hanging vertically in the centre of a cylindrical pipe, with fluid flowing downwards in the narro