Transient Wellbore Fluid Flow Model
1982-04-06
WELBORE is a code to solve transient, one-dimensional two-phase or single-phase non-isothermal fluid flow in a wellbore. The primary thermodynamic variables used in solving the equations are the pressure and specific energy. An equation of state subroutine provides the density, quality, and temperature. The heat loss out of the wellbore is calculated by solving a radial diffusion equation for the temperature changes outside the bore. The calculation is done at each node point in themore » wellbore.« less
VISCOPLASTIC FLUID MODEL FOR DEBRIS FLOW ROUTING.
Chen, Cheng-lung
1986-01-01
This paper describes how a generalized viscoplastic fluid model, which was developed based on non-Newtonian fluid mechanics, can be successfully applied to routing a debris flow down a channel. The one-dimensional dynamic equations developed for unsteady clear-water flow can be used for debris flow routing if the flow parameters, such as the momentum (or energy) correction factor and the resistance coefficient, can be accurately evaluated. The writer's generalized viscoplastic fluid model can be used to express such flow parameters in terms of the rheological parameters for debris flow in wide channels. A preliminary analysis of the theoretical solutions reveals the importance of the flow behavior index and the so-called modified Froude number for uniformly progressive flow in snout profile modeling.
Template Matching Using a Fluid Flow Model
NASA Astrophysics Data System (ADS)
Newman, William Curtis
Template matching is successfully used in machine recognition of isolated spoken words. In these systems a word is broken into frames (20 millisecond time slices) and the spectral characteristics of each frame are found. Thus, each word is represented as a 2-dimensional (2-D) function of spectral characteristic and frame number. An unknown word is recognized by matching its 2-D representation to previously stored example words, or templates, also in this 2-D form. A new model for this matching step will be introduced. The 2-D representations of the template and unknown are used to determine the shape of a volume of viscous fluid. This volume is broken up into many small elements. The unknown is changed into the template by allowing flows between the element boundaries. Finally the match between the template and unknown is determined by calculating a weighted squared sum of the flow values. The model also allows the relative flow resistance between the element boundaries to be changed. This is useful for characterizing the important features of a given template. The flow resistances are changed according to the gradient of a simple performance function. This performance function is evaluated using a set of training samples provided by the user. The model is applied to isolated word and single character recognition tasks. Results indicate the applications where this model works best.
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."
A coupled model of fluid flow in jointed rock
Swenson, Daniel; Martineau, Rick; James, Mark; Brown, Don
1991-01-01
We present a fully coupled model of fluid flow in jointed rock, where the fluid flow depends on the joint openings and the joint openings depend on the fluid pressure. The joints and rock blocks are modeled discretely using the finite element method. Solutions for the fluid and rock are obtained and iteration is performed until both solutions converge. Example applications include an examination of the effects of back-pressure on flow in a geothermal reservoir and transient fluid injection into a reservoir.
Two-fluid Hydrodynamic Model for Fluid-Flow Simulation in Fluid-Solids Systems
1994-06-20
FLUFIX is a two-dimensional , transient, Eulerian, and finite-difference program, based on a two-fluid hydrodynamic model, for fluid flow simulation in fluid-solids systems. The software is written in a modular form using the Implicit Multi-Field (IMF) numerical technique. Quantities computed are the spatial distribution of solids loading, gas and solids velocities, pressure, and temperatures. Predicted are bubble formation, bed frequencies, and solids recirculation. Applications include bubbling and circulating atmospheric and pressurized fluidized bed reactors, combustors, gasifiers, and FCC (Fluid Catalytic Cracker) reactors.
Two-fluid Hydrodynamic Model for Fluid-Flow Simulation in Fluid-Solids Systems
1994-06-20
FLUFIX is a two-dimensional , transient, Eulerian, and finite-difference program, based on a two-fluid hydrodynamic model, for fluid flow simulation in fluid-solids systems. The software is written in a modular form using the Implicit Multi-Field (IMF) numerical technique. Quantities computed are the spatial distribution of solids loading, gas and solids velocities, pressure, and temperatures. Predicted are bubble formation, bed frequencies, and solids recirculation. Applications include bubbling and circulating atmospheric and pressurized fluidized bed reactors, combustors,more » gasifiers, and FCC (Fluid Catalytic Cracker) reactors.« less
Pulmonary fluid flow challenges for experimental and mathematical modeling.
Levy, Rachel; Hill, David B; Forest, M Gregory; Grotberg, James B
2014-12-01
Modeling the flow of fluid in the lungs, even under baseline healthy conditions, presents many challenges. The complex rheology of the fluids, interaction between fluids and structures, and complicated multi-scale geometry all add to the complexity of the problem. We provide a brief overview of approaches used to model three aspects of pulmonary fluid and flow: the surfactant layer in the deep branches of the lung, the mucus layer in the upper airway branches, and closure/reopening of the airway. We discuss models of each aspect, the potential to capture biological and therapeutic information, and open questions worthy of further investigation. We hope to promote multi-disciplinary collaboration by providing insights into mathematical descriptions of fluid-mechanics in the lung and the kinds of predictions these models can make. PMID:25096289
Pulmonary Fluid Flow Challenges for Experimental and Mathematical Modeling
Levy, Rachel; Hill, David B.; Forest, M. Gregory; Grotberg, James B.
2014-01-01
Modeling the flow of fluid in the lungs, even under baseline healthy conditions, presents many challenges. The complex rheology of the fluids, interaction between fluids and structures, and complicated multi-scale geometry all add to the complexity of the problem. We provide a brief overview of approaches used to model three aspects of pulmonary fluid and flow: the surfactant layer in the deep branches of the lung, the mucus layer in the upper airway branches, and closure/reopening of the airway. We discuss models of each aspect, the potential to capture biological and therapeutic information, and open questions worthy of further investigation. We hope to promote multi-disciplinary collaboration by providing insights into mathematical descriptions of fluid-mechanics in the lung and the kinds of predictions these models can make. PMID:25096289
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.
A preliminary study to Assess Model Uncertainties in Fluid Flows
Marc Oliver Delchini; Jean C. Ragusa
2009-09-01
The goal of this study is to assess the impact of various flow models for a simplified primary coolant loop of a light water nuclear reactor. The various fluid flow models are based on the Euler equations with an additional friction term, gravity term, momentum source, and energy source. The geometric model is purposefully chosen simple and consists of a one-dimensional (1D) loop system in order to focus the study on the validity of various fluid flow approximations. The 1D loop system is represented by a rectangle; the fluid is heated up along one of the vertical legs and cooled down along the opposite leg. A pressurizer and a pump are included in the horizontal legs. The amount of energy transferred and removed from the system is equal in absolute value along the two vertical legs. The various fluid flow approximations are compressible vs. incompressible, and complete momentum equation vs. Darcy’s approximation. The ultimate goal is to compute the fluid flow models’ uncertainties and, if possible, to generate validity ranges for these models when applied to reactor analysis. We also limit this study to single phase flows with low-Mach numbers. As a result, sound waves carry a very small amount of energy in this particular case. A standard finite volume method is used for the spatial discretization of the system.
Hydromechanical Modeling of Fluid Flow in the Lower Crust
NASA Astrophysics Data System (ADS)
Connolly, J.
2011-12-01
The lower crust lies within an ambiguous rheological regime between the brittle upper crust and ductile sub-lithospheric mantle. This ambiguity has allowed two schools of thought to develop concerning the nature of fluid flow in the lower crust. The classical school holds that lower crustal rocks are inviscid and that any fluid generated by metamorphic devolatilization is squeezed out of rocks as rapidly as it is produced. According to this school, permeability is a dynamic property and fluid flow is upward. In contrast, the modern school uses concepts from upper crustal hydrology that presume implicitly, if not explicitly, that rocks are rigid or, at most, brittle. For the modern school, the details of crustal permeability determine fluid flow and as these details are poorly known almost anything is possible. Reality, to the extent that it is reflected by inference from field studies, offers some support to both schools. In particular, evidence of significant lateral and channelized fluid flow are consistent with flow in rigid media, while evidence for short (104 - 105 y) grain-scale fluid-rock interaction during much longer metamorphic events, suggests that reaction-generated grain-scale permeability is sealed rapidly by compaction; a phenomenon that is also essential to prevent extensive retrograde metamorphism. These observations provide a compelling argument for recognizing in conceptual models of lower crustal fluid flow that rocks are neither inviscid nor rigid, but compact by viscous mechanisms on a finite time-scale. This presentation will review the principle consequences of, and obstacles to, incorporating compaction in such models. The role of viscous compaction in the lower crust is extraordinarily uncertain, but ignoring this uncertainty in models of lower crustal fluid flow does not make the models any more certain. Models inevitably invoke an initial steady state hydraulic regime. This initial steady state is critical to model outcomes because it
Modeling and Direct Numerical Simulation of Ternary Fluid Flows
NASA Astrophysics Data System (ADS)
Kim, Jun-Seok; Lowengrub, John; Longmire, Ellen
2001-06-01
In this talk, we will present a physically-based model of flows involving three liquid components. The components may exhibit preferential miscibility with one another. The flows we consider are characterized by the presence of interfaces separating immiscible flow components with pinchoff and reconnection of interfaces being important features of the flow. In our model, these topological transitions are handled smoothly without explicit interface reconstruction. In addition, we model the diffusion of miscible components in the bulk and across the interfaces. To illustrate the method, we present numerical simulations of remediation of a contaminant-laden fluid using liquid/liquid extraction.
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
Particle hopping vs. fluid-dynamical models for traffic flow
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.
Numerical modeling of fluid flow with rafts: An application to lava flows
NASA Astrophysics Data System (ADS)
Tsepelev, Igor; Ismail-Zadeh, Alik; Melnik, Oleg; Korotkii, Alexander
2016-07-01
Although volcanic lava flows do not significantly affect the life of people, its hazard is not negligible as hot lava kills vegetation, destroys infrastructure, and may trigger a flood due to melting of snow/ice. The lava flow hazard can be reduced if the flow patterns are known, and the complexity of the flow with debris is analyzed to assist in disaster risk mitigation. In this paper we develop three-dimensional numerical models of a gravitational flow of multi-phase fluid with rafts (mimicking rigid lava-crust fragments) on a horizontal and topographic surfaces to explore the dynamics and the interaction of lava flows. We have obtained various flow patterns and spatial distribution of rafts depending on conditions at the surface of fluid spreading, obstacles on the way of a fluid flow, raft landing scenarios, and the size of rafts. Furthermore, we analyze two numerical models related to specific lava flows: (i) a model of fluid flow with rafts inside an inclined channel, and (ii) a model of fluid flow from a single vent on an artificial topography, when the fluid density, its viscosity, and the effusion rate vary with time. Although the studied models do not account for lava solidification, crust formation, and its rupture, the results of the modeling may be used for understanding of flows with breccias before a significant lava cooling.
Modeling Fluid Flows in Distensible Tubes for Applications in Hemodynamics
NASA Astrophysics Data System (ADS)
Descovich, X.; Pontrelli, G.; Melchionna, S.; Succi, S.; Wassertheurer, S.
2013-05-01
We present a lattice Boltzmann (LB) model for the simulation of hemodynamic flows in the presence of compliant walls. The new scheme is based on the use of a continuous bounce-back boundary condition, as combined with a dynamic constitutive relation between the flow pressure at the wall and the resulting wall deformation. The method is demonstrated for the case of two-dimensional (axisymmetric) pulsatile flows, showing clear evidence of elastic wave propagation of the wall perturbation in response to the fluid pressure. The extension of the present two-dimensional axisymmetric formulation to more general three-dimensional geometries is currently under investigation.
Numerical modeling of fluid flow in solid tumors.
Soltani, M; Chen, P
2011-01-01
A mathematical model of interstitial fluid flow is developed, based on the application of the governing equations for fluid flow, i.e., the conservation laws for mass and momentum, to physiological systems containing solid tumors. The discretized form of the governing equations, with appropriate boundary conditions, is developed for a predefined tumor geometry. The interstitial fluid pressure and velocity are calculated using a numerical method, element based finite volume. Simulations of interstitial fluid transport in a homogeneous solid tumor demonstrate that, in a uniformly perfused tumor, i.e., one with no necrotic region, because of the interstitial pressure distribution, the distribution of drug particles is non-uniform. Pressure distribution for different values of necrotic radii is examined and two new parameters, the critical tumor radius and critical necrotic radius, are defined. Simulation results show that: 1) tumor radii have a critical size. Below this size, the maximum interstitial fluid pressure is less than what is generally considered to be effective pressure (a parameter determined by vascular pressure, plasma osmotic pressure, and interstitial osmotic pressure). Above this size, the maximum interstitial fluid pressure is equal to effective pressure. As a consequence, drugs transport to the center of smaller tumors is much easier than transport to the center of a tumor whose radius is greater than the critical tumor radius; 2) there is a critical necrotic radius, below which the interstitial fluid pressure at the tumor center is at its maximum value. If the tumor radius is greater than the critical tumor radius, this maximum pressure is equal to effective pressure. Above this critical necrotic radius, the interstitial fluid pressure at the tumor center is below effective pressure. In specific ranges of these critical sizes, drug amount and therefore therapeutic effects are higher because the opposing force, interstitial fluid pressure, is low in
ANFIS modeling for prediction of particle motions in fluid flows
NASA Astrophysics Data System (ADS)
Safdari, Arman; Kim, Kyung Chun
2015-11-01
Accurate dynamic analysis of parcel of solid particles driven in fluid flow system is of interest for many natural and industrial applications such as sedimentation process, study of cloud particles in atmosphere, etc. In this paper, numerical modeling of solid particles in incompressible flow using Eulerian-Lagrangian approach is carried out to investigate the dynamic behavior of particles in different flow conditions; channel and cavity flow. Although modern computers have been well developed, the high computational time and costs for this kind of problems are still demanded. The Lattice Boltzmann Method (LBM) is used to simulate fluid flows and combined with the Lagrangian approach to predict the motion of particles in the range of masses. Some particles are selected, and subjected to Adaptive-network-based fuzzy inference system (ANFIS) to predict the trajectory of moving solid particles. Using a hybrid learning procedure from computational particle movement, the ANFIS can construct an input-output mapping based on fuzzy if-then rules and stipulated computational fluid dynamics prediction pairs. The obtained results from ANFIS algorithm is validated and compared with the set of benchmark data provided based on point-like approach coupled with the LBM method.
GEOSIM: A numerical model for geophysical fluid flow simulation
NASA Technical Reports Server (NTRS)
Butler, Karen A.; Miller, Timothy L.; Lu, Huei-Iin
1991-01-01
A numerical model which simulates geophysical fluid flow in a wide range of problems is described in detail, and comparisons of some of the model's results are made with previous experimental and numerical studies. The model is based upon the Boussinesq Navier-Stokes equations in spherical coordinates, which can be reduced to a cylindrical system when latitudinal walls are used near the pole and the ratio of latitudinal length to the radius of the sphere is small. The equations are approximated by finite differences in the meridional plane and spectral decomposition in the azimuthal direction. The user can specify a variety of boundary and initial conditions, and there are five different spectral truncation options. The results of five validation cases are presented: (1) the transition between axisymmetric flow and baroclinic wave flow in the side heated annulus; (2) the steady baroclinic wave of the side heated annulus; (3) the wave amplitude vacillation of the side heated annulus; (4) transition to baroclinic wave flow in a bottom heated annulus; and (5) the Spacelab Geophysical Fluid Flow Cell (spherical) experiment.
Fluid flow and heat transfer modeling for castings
Domanus, H.M.; Liu, Y.Y.; Sha, W.T.
1986-01-01
Casting is fundamental to manufacturing of many types of equipment and products. Although casting is a very old technology that has been in existence for hundreds of years, it remains a highly empirical technology, and production of new castings requires an expensive and time-consuming trial-and-error approach. In recent years, mathematical modeling of casting has received increasing attention; however, a majority of the modeling work has been in the area of heat transfer and solidification. Very little work has been done in modeling fluid flow of the liquid melt. This paper presents a model of fluid flow coupled with heat transfer of a liquid melt for casting processes. The model to be described in this paper is an extension of the COMMIX code and is capable of handling castings with any shape, size, and material. A feature of this model is the ability to track the liquid/gas interface and liquid/solid interface. The flow of liquid melt through the sprue and runners and into the mold cavity is calculated as well as three-dimensional temperature and velocity distributions of the liquid melt throughout the casting process. 14 refs., 13 figs.
FLUFIXMOD2. Two-fluid Hydrodynamic Model for Fluid-Flow Simulation in Fluid-Solids Systems
Lyczkowski, R.W.; Bouillard, J.X.; Folga, S.M.
1992-04-01
FLUFIX is a two-dimensional , transient, Eulerian, and finite-difference program, based on a two-fluid hydrodynamic model, for fluid flow simulation in fluid-solids systems. The software is written in a modular form using the Implicit Multi-Field (IMF) numerical technique. Quantities computed are the spatial distribution of solids loading, gas and solids velocities, pressure, and temperatures. Predicted are bubble formation, bed frequencies, and solids recirculation. Applications include bubbling and circulating atmospheric and pressurized fluidized bed reactors, combustors, gasifiers, and FCC (Fluid Catalytic Cracker) reactors.
Modelling couplings between reaction, fluid flow and deformation: Kinetics
NASA Astrophysics Data System (ADS)
Malvoisin, Benjamin; Podladchikov, Yury Y.; Connolly, James A. D.
2016-04-01
Mineral assemblages out of equilibrium are commonly found in metamorphic rocks testifying of the critical role of kinetics for metamorphic reactions. As experimentally determined reaction rates in fluid-saturated systems generally indicate complete reaction in less than several years, i.e. several orders of magnitude faster than field-based estimates, metamorphic reaction kinetics are generally thought to be controlled by transport rather than by processes at the mineral surface. However, some geological processes like earthquakes or slow-slip events have shorter characteristic timescales, and transport processes can be intimately related to mineral surface processes. Therefore, it is important to take into account the kinetics of mineral surface processes for modelling fluid/rock interactions. Here, a model coupling reaction, fluid flow and deformation was improved by introducing a delay in the achievement of equilibrium. The classical formalism for dissolution/precipitation reactions was used to consider the influence of the distance from equilibrium and of temperature on the reaction rate, and a dependence on porosity was introduced to model evolution of reacting surface area during reaction. The fitting of experimental data for three reactions typically occurring in metamorphic systems (serpentine dehydration, muscovite dehydration and calcite decarbonation) indicates a systematic faster kinetics close from equilibrium on the dehydration side than on the hydration side. This effect is amplified through the porosity term in the reaction rate since porosity is formed during dehydration. Numerical modelling indicates that this difference in reaction rate close from equilibrium plays a key role in microtextures formation. The developed model can be used in a wide variety of geological systems where couplings between reaction, deformation and fluid flow have to be considered.
A Generalized Fluid System Simulation Program to Model Flow Distribution in Fluid Networks
NASA Technical Reports Server (NTRS)
Majumdar, Alok; Bailey, John W.; Schallhorn, Paul; Steadman, Todd
1998-01-01
This paper describes a general purpose computer program for analyzing steady state and transient flow in a complex network. The program is capable of modeling phase changes, compressibility, mixture thermodynamics and external body forces such as gravity and centrifugal. The program's preprocessor allows the user to interactively develop a fluid network simulation consisting of nodes and branches. Mass, energy and specie conservation equations are solved at the nodes; the momentum conservation equations are solved in the branches. The program contains subroutines for computing "real fluid" thermodynamic and thermophysical properties for 33 fluids. The fluids are: helium, methane, neon, nitrogen, carbon monoxide, oxygen, argon, carbon dioxide, fluorine, hydrogen, parahydrogen, water, kerosene (RP-1), isobutane, butane, deuterium, ethane, ethylene, hydrogen sulfide, krypton, propane, xenon, R-11, R-12, R-22, R-32, R-123, R-124, R-125, R-134A, R-152A, nitrogen trifluoride and ammonia. The program also provides the options of using any incompressible fluid with constant density and viscosity or ideal gas. Seventeen different resistance/source options are provided for modeling momentum sources or sinks in the branches. These options include: pipe flow, flow through a restriction, non-circular duct, pipe flow with entrance and/or exit losses, thin sharp orifice, thick orifice, square edge reduction, square edge expansion, rotating annular duct, rotating radial duct, labyrinth seal, parallel plates, common fittings and valves, pump characteristics, pump power, valve with a given loss coefficient, and a Joule-Thompson device. The system of equations describing the fluid network is solved by a hybrid numerical method that is a combination of the Newton-Raphson and successive substitution methods. This paper also illustrates the application and verification of the code by comparison with Hardy Cross method for steady state flow and analytical solution for unsteady flow.
Complex fluid flow modeling with SPH on GPU
NASA Astrophysics Data System (ADS)
Bilotta, Giuseppe; Hérault, Alexis; Del Negro, Ciro; Russo, Giovanni; Vicari, Annamaria
2010-05-01
We describe an implementation of the Smoothed Particle Hydrodynamics (SPH) method for the simulation of complex fluid flows. The algorithm is entirely executed on Graphic Processing Units (GPUs) using the Compute Unified Device Architecture (CUDA) developed by NVIDIA and fully exploiting their computational power. An increase of one to two orders of magnitude in simulation speed over equivalent CPU code is achieved. A complete modeling of the flow of a complex fluid such as lava is challenging from the modelistic, numerical and computational points of view. The natural topography irregularities, the dynamic free boundaries and phenomena such as solidification, presence of floating solid bodies or other obstacles and their eventual fragmentation make the problem difficult to solve using traditional numerical methods (finite volumes, finite elements): the need to refine the discretization grid in correspondence of high gradients, when possible, is computationally expensive and with an often inadequate control of the error; for real-world applications, moreover, the information needed by the grid refinement may not be available (e.g. because the Digital Elevation Models are too coarse); boundary tracking is also problematic with Eulerian discretizations, more so with complex fluids due to the presence of internal boundaries given by fluid inhomogeneity and presence of solidification fronts. An alternative approach is offered by mesh-free particle methods, that solve most of the problems connected to the dynamics of complex fluids in a natural way. Particle methods discretize the fluid using nodes which are not forced on a given topological structure: boundary treatment is therefore implicit and automatic; the movement freedom of the particles also permits the treatment of deformations without incurring in any significant penalty; finally, the accuracy is easily controlled by the insertion of new particles where needed. Our team has developed a new model based on the
FLUENT/BFC - A general purpose fluid flow modeling program for all flow speeds
NASA Astrophysics Data System (ADS)
Dvinsky, Arkady S.
FLUENT/BFC is a fluid flow modeling program for a variety of applications. Current capabilities of the program include laminar and turbulent flows, subsonic and supersonic viscous flows, incompressible flows, time-dependent and stationary flows, isothermal flows and flows with heat transfer, Newtonian and power-law fluids. The modeling equations in the program have been written in coordinate system invariant form to accommodate the use of boundary-conforming, generally nonorthogonal coordinate systems. The boundary-conforming coordinate system can be generated using both an internal grid generator, which is an integral part of the code, and external application-specific grid generators. The internal grid generator is based on a solution of a system of elliptic partial differential equations and can produce grids for a wide variety of two- and three-dimensional geometries.
Pulsatile flow of power-law fluid model for blood flow under periodic body acceleration.
Chaturani, P; Palanisamy, V
1990-01-01
A mathematical model has been proposed to study the pulsatile flow of a power-law fluid through rigid circular tubes under the influence of a periodic body acceleration. Numerical solutions have been obtained by using finite difference method. The accuracy of the numerical procedure has been checked by comparing the obtained numerical results with other numerical and analytical solutions. It is found that the agreement between them is quite good. Interaction of non-Newtonian nature of fluid with the body acceleration has been investigated by using the physiological data for two particular cases (coronary and femoral arteries). The axial velocity, fluid acceleration, wall shear stress and instantaneous volume flow rate have been computed and their variations with different parameters have been analyzed. The following important observations have been made: (i) The velocity and acceleration profiles can have more than one maxima, this is in contrast with usual parabolic profiles where they have only one maximum at the axis. As n increases, the maxima shift towards the axis; (ii) For the flow with no body acceleration, the amplitude of both, wall shear and flow rate, increases with n, whereas for the flow with body acceleration, the amplitude of wall shear (flow rate) increases (decreases) as n increases; (iii) In the absence of body acceleration, pseudoplastic (dilatant) fluids, with low frequency pulsations, have higher (lower) value of maximum flow rate Qmax than Newtonian fluids, whereas for high frequencies, opposite behavior has been observed; for flow with body acceleration pulsations gives higher (lower) value of Qmax for pseudoplastic (dilatant) fluids than Newtonian fluids.
Hydraulic sand-model studies of miscible-fluid flow
Cahill, J.M.
1973-01-01
Hydraulic sand models are useful physical tools in the investigation of the transition zone that occurs between salt and fresh ground water in coastal aquifers. Such models are used to demonstrate the effects of transport mechanisms that influence the dynamic behavior and the shape of the transition zone. The techniques employed in obtaining in-place measurements of solute concentrations are generally the stumbling block in generating data for two-dimensional dispersion systems. Two in-place measurement techniques were used in the studies described: (1) conductivity probes when salt was used as a tracer; and (2) photoelectric cells when organic dye was used as a tracer. Results indicate that conductivity methods are more reliable; however, care must be exercised inasmuch as the probes tend to disturb the fluid flow.
Advances in modelling of biomimetic fluid flow at different scales
2011-01-01
The biomimetic flow at different scales has been discussed at length. The need of looking into the biological surfaces and morphologies and both geometrical and physical similarities to imitate the technological products and processes has been emphasized. The complex fluid flow and heat transfer problems, the fluid-interface and the physics involved at multiscale and macro-, meso-, micro- and nano-scales have been discussed. The flow and heat transfer simulation is done by various CFD solvers including Navier-Stokes and energy equations, lattice Boltzmann method and molecular dynamics method. Combined continuum-molecular dynamics method is also reviewed. PMID:21711847
Wu, Binxin
2010-12-01
In this paper, 12 turbulence models for single-phase non-newtonian fluid flow in a pipe are evaluated by comparing the frictional pressure drops obtained from computational fluid dynamics (CFD) with those from three friction factor correlations. The turbulence models studied are (1) three high-Reynolds-number k-ε models, (2) six low-Reynolds-number k-ε models, (3) two k-ω models, and (4) the Reynolds stress model. The simulation results indicate that the Chang-Hsieh-Chen version of the low-Reynolds-number k-ε model performs better than the other models in predicting the frictional pressure drops while the standard k-ω model has an acceptable accuracy and a low computing cost. In the model applications, CFD simulation of mixing in a full-scale anaerobic digester with pumped circulation is performed to propose an improvement in the effective mixing standards recommended by the U.S. EPA based on the effect of rheology on the flow fields. Characterization of the velocity gradient is conducted to quantify the growth or breakage of an assumed floc size. Placement of two discharge nozzles in the digester is analyzed to show that spacing two nozzles 180° apart with each one discharging at an angle of 45° off the wall is the most efficient. Moreover, the similarity rules of geometry and mixing energy are checked for scaling up the digester.
Energy flow model for thin plate considering fluid loading with mean flow
NASA Astrophysics Data System (ADS)
Han, Ju-Bum; Hong, Suk-Yoon; Song, Jee-Hun
2012-11-01
Energy Flow Analysis (EFA) has been developed to predict the vibration energy density of system structures in the high frequency range. This paper develops the energy flow model for the thin plate in contact with mean flow. The pressure generated by mean flow affects energy governing equation and power reflection-transmission coefficients between plates. The fluid pressure is evaluated by using velocity potential and Bernoulli's equation, and energy governing equations are derived by considering the flexural wavenumbers of a plate, which are different along the direction of flexural wave and mean flow. The derived energy governing equation is composed of two kinds of group velocities. To verify the developed energy flow model, various numerical analyses are performed for a simple plate and a coupled plate for several excitation frequencies. The EFA results are compared with the analytical solutions, and correlations between the EFA results and the analytical solutions are verified.
Mathematical modeling of slope flows with entrainment as flows of non-Newtonian fluids
NASA Astrophysics Data System (ADS)
Zayko, Julia; Eglit, Margarita
2015-04-01
Non-Newtonian fluids in which the shear stresses are nonlinear functions of the shear strain rates are used to model slope flows such as snow avalanches, mudflows, debris flows. The entrainment of bottom material is included into the model basing on the assumption that in entraining flows the bed friction is equal to the shear stress of the bottom material (Issler et al, 2011). Unsteady motion down long homogeneous slopes with constant inclines is studied numerically for different flow rheologies and different slope angles. Variation of the velocity profile, increase of the flow depth and velocity due to entrainment as well as the value of the entrainment rate is calculated. Asymptotic formulae for the entrainment rate are derived for unsteady flows of different rheological properties. REFERENCES Chowdhury M., Testik F., 2011. Laboratory testing of mathematical models for high-concentration fluid mud turbidity currents. Ocean Engineering 38, 256-270. Eglit, M.E., Demidov, K.S., 2005. Mathematical modeling of snow entrainment in avalanche motion. Cold Reg. Sci. Technol. 43 (1-2), 10-23. Eglit M. E., Yakubenko A. E., 2012, Mathematical Modeling of slope flows entraining bottom material. Eglit M. E., Yakubenko A. E., 2014, Numerical modeling of slope flows entraining bottom material. Cold Reg. Sci. Technol. 108, 139-148. Issler D, M. Pastor Peréz. 2011. Interplay of entrainment and rheology in snow avalanches; a numerical study. Annals of Glaciology, 52(58), pp.143-147 Kern M. A., Tiefenbacher F., McElwaine J., N., 2004. The rheology of snow in large chute flows. Cold Regions Science and Technology, 39, 181 -192. Naaim, M., Faug, T., Naaim-Bouvet, F., 2003. Dry granular flow modelling including erosion and deposition. Surv. Geophys. 24, 569-585. Naaim, M., Naaim-Bouvet, F., Faug, T., Bouchet, A., 2004. Dense snow avalanche modeling: flow, erosion, deposition and obstacle effects. Cold Reg. Sci. Technol. 39, 193-204. Rougier, J & Kern, M 2010, 'Predicting snow
Winters, W.S.
1984-01-01
An overview of the computer code TOPAZ (Transient-One-Dimensional Pipe Flow Analyzer) is presented. TOPAZ models the flow of compressible and incompressible fluids through complex and arbitrary arrangements of pipes, valves, flow branches and vessels. Heat transfer to and from the fluid containment structures (i.e. vessel and pipe walls) can also be modeled. This document includes discussions of the fluid flow equations and containment heat conduction equations. The modeling philosophy, numerical integration technique, code architecture, and methods for generating the computational mesh are also discussed.
Chang, F.C.; Hull, J.R.; Wang, Y.H.; Blazek, K.E.
1996-02-01
A computer model was developed to predict eddy currents and fluid flows in molten steel. The model was verified by comparing predictions with experimental results of liquid-metal containment and fluid flow in electromagnetic (EM) edge dams (EMDs) designed at Inland Steel for twin-roll casting. The model can optimize the EMD design so it is suitable for application, and minimize expensive, time-consuming full-scale testing. Numerical simulation was performed by coupling a three-dimensional (3-D) finite-element EM code (ELEKTRA) and a 3-D finite-difference fluids code (CaPS-EM) to solve heat transfer, fluid flow, and turbulence transport in a casting process that involves EM fields. ELEKTRA is able to predict the eddy- current distribution and the electromagnetic forces in complex geometries. CaPS-EM is capable of modeling fluid flows with free surfaces. Results of the numerical simulation compared well with measurements obtained from a static test.
Predicting multidimensional annular flow with a locally based two-fluid model
Antal, S.P.; Edwards, D.P.; Strayer, T.D.
1998-06-01
The purpose of this work was to: develop a methodology to predict annular flows using a multidimensional four-field, two-fluid Computational Fluid Dynamics (CFD) computer code; develop closure models which use the CFD predicted local velocities, phasic volume fractions, etc...; implement a numerical method which allows the discretized equations to have the same characteristics as the differential form; and compare predicted results to local flow field data taken in a R-134a working fluid test section.
Regional Fluid Flow and Basin Modeling in Northern Alaska
Kelley, Karen D.
2007-01-01
INTRODUCTION The foothills of the Brooks Range contain an enormous accumulation of zinc (Zn) in the form of zinc sulfide and barium (Ba) in the form of barite in Carboniferous shale, chert, and mudstone. Most of the resources and reserves of Zn occur in the Red Dog deposit and others in the Red Dog district; these resources and reserves surpass those of most deposits worldwide in terms of size and grade. In addition to zinc and lead sulfides (which contain silver, Ag) and barite, correlative strata host phosphate deposits. Furthermore, prolific hydrocarbon source rocks of Carboniferous and Triassic to Early Jurassic age generated considerable amounts of petroleum that may have contributed to the world-class petroleum resources of the North Slope. Deposits of Zn-Pb-Ag or barite as large as those in the Brooks Range are very rare on a global basis and, accordingly, multiple coincident favorable factors must be invoked to explain their origins. To improve our understanding of these factors and to contribute to more effective assessments of resources in sedimentary basins of northern Alaska and throughout the world, the Mineral Resources Program and the Energy Resources Program of the U.S. Geological Survey (USGS) initiated a project that was aimed at understanding the petroleum maturation and mineralization history of parts of the Brooks Range that were previously poorly characterized. The project, titled ?Regional Fluid Flow and Basin Modeling in Northern Alaska,? was undertaken in collaboration with industry, academia, and other government agencies. This Circular contains papers that describe the results of the recently completed project. The studies that are highlighted in these papers have led to a better understanding of the following: *The complex sedimentary facies relationships and depositional settings and the geochemistry of the sedimentary rocks that host the deposits (sections 2 and 3). *The factors responsible for formation of the barite and zinc deposits
E-1 Dynamic Fluid-Flow Model Update: EASY/ROCETS Enhancement and Model Development Support
NASA Technical Reports Server (NTRS)
Follett, Randolph F.; Taylor, Robert P.
1998-01-01
This report documents the research conducted to update computer models for dynamic fluid flow simulation of the E-1 test stand subsystems at te NASA John C. Stennis Space Center.Work also involved significant upgrades to the capabilities of EASY/ROCKETS library through the inclusion of the NIST-12 thermodynamic property database and development of new control system modules.
Fluid Structure Modelling of Blood Flow in Vessels.
Moatamedi, M; Souli, M; Al-Bahkali, E
2014-12-01
This paper describes the capabilities of fluid structure interaction based multi-physics numerical modelling in solving problems related to vascular biomechanics. In this research work, the onset of a pressure pulse was simulated at the entrance of a three dimensional straight segment of the blood vessel like circular tube and the resulting dynamic response in the form of a propagating pulse wave through the wall was analysed and compared. Good agreement was found between the numerical results and the theoretical description of an idealized artery. Work has also been done on implementing the material constitutive models specific for vascular applications.
Fluid Structure Modelling of Blood Flow in Vessels.
Moatamedi, M; Souli, M; Al-Bahkali, E
2014-12-01
This paper describes the capabilities of fluid structure interaction based multi-physics numerical modelling in solving problems related to vascular biomechanics. In this research work, the onset of a pressure pulse was simulated at the entrance of a three dimensional straight segment of the blood vessel like circular tube and the resulting dynamic response in the form of a propagating pulse wave through the wall was analysed and compared. Good agreement was found between the numerical results and the theoretical description of an idealized artery. Work has also been done on implementing the material constitutive models specific for vascular applications. PMID:26336693
Predicting multidimensional annular flows with a locally based two-fluid model
Antal, S.P. Edwards, D.P.; Strayer, T.D.
1998-06-01
Annular flows are a well utilized flow regime in many industrial applications, such as, heat exchangers, chemical reactors and industrial process equipment. These flows are characterized by a droplet laden vapor core with a thin, wavy liquid film wetting the walls. The prediction of annular flows has been largely confined to one-dimensional modeling which typically correlates the film thickness, droplet loading, and phase velocities by considering the average flow conditions and global mass and momentum balances to infer the flow topology. In this paper, a methodology to predict annular flows using a locally based two-fluid model of multiphase flow is presented. The purpose of this paper is to demonstrate a modeling approach for annular flows using a multifield, multidimensional two-fluid model and discuss the need for further work in this area.
A Tightly Coupled Particle-Fluid Model for DNA-Laden Flows in Complex Microscale Geometries
Trebotich, D; Miller, G H; Colella, P; Graves, D T; Martin, D F; Schwartz, P O
2004-11-18
We present a stable and convergent method for the computation of flows of DNA-laden fluids in microchannels with complex geometry. The numerical strategy combines a ball-rod model representation for polymers tightly coupled with a projection method for incompressible viscous flow. We use Cartesian grid embedded boundary methods to discretize the fluid equations in the presence of complex domain boundaries. A sample calculation is presented showing flow through a packed array microchannel in 2D.
Field and modelling studies of immiscible fluid flow above a contaminated water-table aquifer
Herkelrath, W.N.; Essaid, H.I.; Hess, K.M.
1991-01-01
A method was developed for measuring the spatial distribution of immiscible liquid contaminants in the subsurface. Fluid saturation distributions measured at a crude-oil spill site were used to test a numerical multiphase flow model.
Masoumi, Nafiseh; Framanzad, F; Zamanian, Behnam; Seddighi, A S; Moosavi, M H; Najarian, S; Bastani, Dariush
2013-01-01
Many diseases are related to cerebrospinal fluid (CSF) hydrodynamics. Therefore, understanding the hydrodynamics of CSF flow and intracranial pressure is helpful for obtaining deeper knowledge of pathological processes and providing better treatments. Furthermore, engineering a reliable computational method is promising approach for fabricating in vitro models which is essential for inventing generic medicines. A Fluid-Solid Interaction (FSI)model was constructed to simulate CSF flow. An important problem in modeling the CSF flow is the diastolic back flow. In this article, using both rigid and flexible conditions for ventricular system allowed us to evaluate the effect of surrounding brain tissue. Our model assumed an elastic wall for the ventricles and a pulsatile CSF input as its boundary conditions. A comparison of the results and the experimental data was done. The flexible model gave better results because it could reproduce the diastolic back flow mentioned in clinical research studies. The previous rigid models have ignored the brain parenchyma interaction with CSF and so had not reported the back flow during the diastolic time. In this computational fluid dynamic (CFD) analysis, the CSF pressure and flow velocity in different areas were concordant with the experimental data.
Masoumi, Nafiseh; Framanzad, F; Zamanian, Behnam; Seddighi, A S; Moosavi, M H; Najarian, S; Bastani, Dariush
2013-01-01
Many diseases are related to cerebrospinal fluid (CSF) hydrodynamics. Therefore, understanding the hydrodynamics of CSF flow and intracranial pressure is helpful for obtaining deeper knowledge of pathological processes and providing better treatments. Furthermore, engineering a reliable computational method is promising approach for fabricating in vitro models which is essential for inventing generic medicines. A Fluid-Solid Interaction (FSI)model was constructed to simulate CSF flow. An important problem in modeling the CSF flow is the diastolic back flow. In this article, using both rigid and flexible conditions for ventricular system allowed us to evaluate the effect of surrounding brain tissue. Our model assumed an elastic wall for the ventricles and a pulsatile CSF input as its boundary conditions. A comparison of the results and the experimental data was done. The flexible model gave better results because it could reproduce the diastolic back flow mentioned in clinical research studies. The previous rigid models have ignored the brain parenchyma interaction with CSF and so had not reported the back flow during the diastolic time. In this computational fluid dynamic (CFD) analysis, the CSF pressure and flow velocity in different areas were concordant with the experimental data. PMID:25337330
A fully coupled porous flow and geomechanics model for fluid driven cracks: a peridynamics approach
NASA Astrophysics Data System (ADS)
Ouchi, Hisanao; Katiyar, Amit; York, Jason; Foster, John T.; Sharma, Mukul M.
2015-03-01
A state-based non-local peridynamic formulation is presented for simulating fluid driven fractures in an arbitrary heterogeneous poroelastic medium. A recently developed peridynamic formulation of porous flow has been coupled with the existing peridynamic formulation of solid and fracture mechanics resulting in a peridynamic model that for the first time simulates poroelasticity and fluid-driven fracture propagation. This coupling is achieved by modeling the role of pore pressure on the deformation of porous media and vice versa through porosity variation with medium deformation, pore pressure and total mean stress. The poroelastic model is verified by simulating the one-dimensional consolidation of fluid saturated rock. An additional porous flow equation with material permeability dependent on fracture width is solved to simulate fluid flow in the fractured region. Finally, single fluid-driven fracture propagation with a two-dimensional plane strain assumption is simulated and verified against the corresponding classical analytical solution.
Modelling of fluid-structure interaction with multiphase viscous flows using an immersed-body method
NASA Astrophysics Data System (ADS)
Yang, P.; Xiang, J.; Fang, F.; Pavlidis, D.; Latham, J.-P.; Pain, C. C.
2016-09-01
An immersed-body method is developed here to model fluid-structure interaction for multiphase viscous flows. It does this by coupling a finite element multiphase fluid model and a combined finite-discrete element solid model. A coupling term containing the fluid stresses is introduced within a thin shell mesh surrounding the solid surface. The thin shell mesh acts as a numerical delta function in order to help apply the solid-fluid boundary conditions. When used with an advanced interface capturing method, the immersed-body method has the capability to solve problems with fluid-solid interfaces in the presence of multiphase fluid-fluid interfaces. Importantly, the solid-fluid coupling terms are treated implicitly to enable larger time steps to be used. This two-way coupling method has been validated by three numerical test cases: a free falling cylinder in a fluid at rest, elastic membrane and a collapsing column of water moving an initially stationary solid square. A fourth simulation example is of a water-air interface with a floating solid square being moved around by complex hydrodynamic flows including wave breaking. The results show that the immersed-body method is an effective approach for two-way solid-fluid coupling in multiphase viscous flows.
Hydraulic modeling of unsteady debris-flow surges with solid-fluid interactions
Iverson, Richard M.
1997-01-01
Interactions of solid and fluid constituents produce the unique style of motion that typifies debris flows. To simulate this motion, a new hydraulic model represents debris flows as deforming masses of granular solids variably liquefied by viscous pore fluid. The momentum equation of the model describes how internal and boundary forces change as coarse-grained surge heads dominated by grain-contact friction grade into muddy debris-flow bodies more strongly influenced by fluid viscosity and pressure. Scaling analysis reveals that pore-pressure variations can cause flow resistance in surge heads to surpass that in debris-flow bodies by orders of magnitude. Numerical solutions of the coupled momentum and continuity equations provide good predictions of unsteady, nonuniform motion of experimental debris flows from initiation through deposition.
Modeling deformation-induced fluid flow in cortical bone's canalicular-lacunar system.
Gururaja, S; Kim, H J; Swan, C C; Brand, R A; Lakes, R S
2005-01-01
To explore the potential role that load-induced fluid flow plays as a mechano-transduction mechanism in bone adaptation, a lacunar-canalicular scale bone poroelasticity model is developed and implemented. The model uses micromechanics to homogenize the pericanalicular bone matrix, a system of straight circular cylinders in the bone matrix through which bone fluids can flow, as a locally anisotropic poroelastic medium. In this work, a simplified two-dimensional model of a periodic array of lacunae and their surrounding systems of canaliculi is used to quantify local fluid flow characteristics in the vicinity of a single lacuna. When the cortical bone model is loaded, microscale stress, and strain concentrations occur in the vicinity of individual lacunae and give rise to microscale spatial variations in the pore fluid pressure field. Furthermore, loading of the bone matrix containing canaliculi generates fluid pressures in the contained fluids. Consequently, loading of cortical bone induces fluid flow in the canaliculi and exchange of fluid between canaliculi and lacunae. For realistic bone morphology parameters, and a range of loading frequencies, fluid pressures and fluid-solid drag forces in the canalicular bone are computed and the associated energy dissipation in the models compared to that measured in physical in vitro experiments on human cortical bone. The proposed model indicates that deformation-induced fluid pressures in the lacunar-canalicular system have relaxation times on the order of milliseconds as opposed to the much shorter times (hundredths of milliseconds) associated with deformation-induced pressures in the Haversian system.
Direct pore-level modeling of incompressible fluid flow in porous media
Ovaysi, Saeed; Piri, Mohammad
2010-09-20
We present a dynamic particle-based model for direct pore-level modeling of incompressible viscous fluid flow in disordered porous media. The model is capable of simulating flow directly in three-dimensional high-resolution micro-CT images of rock samples. It is based on moving particle semi-implicit (MPS) method. We modify this technique in order to improve its stability for flow in porous media problems. Using the micro-CT image of a rock sample, the entire medium, i.e., solid and fluid, is discretized into particles. The incompressible Navier-Stokes equations are then solved for each particle using the MPS summations. The model handles highly irregular fluid-solid boundaries effectively. An algorithm to split and merge fluid particles is also introduced. To handle the computational load, we present a parallel version of the model that runs on distributed memory computer clusters. The accuracy of the model is validated against the analytical, numerical, and experimental data available in the literature. The validated model is then used to simulate both unsteady- and steady-state flow of an incompressible fluid directly in a representative elementary volume (REV) size micro-CT image of a naturally-occurring sandstone with 3.398 {mu}m resolution. We analyze the quality and consistency of the predicted flow behavior and calculate absolute permeability using the steady-state flow rate.
Soltani, M; Chen, P
2013-01-01
Modeling of interstitial fluid flow involves processes such as fluid diffusion, convective transport in extracellular matrix, and extravasation from blood vessels. To date, majority of microvascular flow modeling has been done at different levels and scales mostly on simple tumor shapes with their capillaries. However, with our proposed numerical model, more complex and realistic tumor shapes and capillary networks can be studied. Both blood flow through a capillary network, which is induced by a solid tumor, and fluid flow in tumor's surrounding tissue are formulated. First, governing equations of angiogenesis are implemented to specify the different domains for the network and interstitium. Then, governing equations for flow modeling are introduced for different domains. The conservation laws for mass and momentum (including continuity equation, Darcy's law for tissue, and simplified Navier-Stokes equation for blood flow through capillaries) are used for simulating interstitial and intravascular flows and Starling's law is used for closing this system of equations and coupling the intravascular and extravascular flows. This is the first study of flow modeling in solid tumors to naturalistically couple intravascular and extravascular flow through a network. This network is generated by sprouting angiogenesis and consisting of one parent vessel connected to the network while taking into account the non-continuous behavior of blood, adaptability of capillary diameter to hemodynamics and metabolic stimuli, non-Newtonian blood flow, and phase separation of blood flow in capillary bifurcation. The incorporation of the outlined components beyond the previous models provides a more realistic prediction of interstitial fluid flow pattern in solid tumors and surrounding tissues. Results predict higher interstitial pressure, almost two times, for realistic model compared to the simplified model.
(Reactive fluid flow models and applications to diagenesis, mineral deposits and crustal rocks)
Lasaga, A.C.; Rye, D.M.
1991-01-01
The objective of this proposal is to put constraints on fluid and mass flux by combining theoretical and field studies of coupled fluid flow, heat and mass transport, and chemical reaction in hydrothermal and metamorphic systems. We are presently applying the two-dimensional code 2DREACT to the study of reactive flow in hydrothermal system. The code represents a new approach to the modeling of simultaneous reaction and transport which was completed in the first months of this project.
An Image-Based Model of Fluid Flow Through Lymph Nodes.
Cooper, Laura J; Heppell, James P; Clough, Geraldine F; Ganapathisubramani, Bharathram; Roose, Tiina
2016-01-01
The lymphatic system returns fluid to the bloodstream from the tissues to maintain tissue fluid homeostasis. Lymph nodes distributed throughout the system filter the lymphatic fluid. The afferent and efferent lymph flow conditions of lymph nodes can be measured in experiments; however, it is difficult to measure the flow within the nodes. In this paper, we present an image-based modelling approach to investigating how the internal structure of the node affects the fluid flow pathways within the node. Selective plane illumination microscopy images of murine lymph nodes are used to identify the geometry and structure of the tissue within the node and to determine the permeability of the lymph node interstitium to lymphatic fluid. Experimental data are used to determine boundary conditions and optimise the parameters for the model. The numerical simulations conducted within the model are implemented in COMSOL Multiphysics, a commercial finite element analysis software. The parameter fitting resulted in the estimate that the average permeability for lymph node tissue is of the order of magnitude of [Formula: see text]. Our modelling shows that the flow predominantly takes a direct path between the afferent and efferent lymphatics and that fluid is both filtered and absorbed across the blood vessel boundaries. The amount that is absorbed or extravasated in the model is dependent on the efferent lymphatic lumen fluid pressure. PMID:26690921
NASA Technical Reports Server (NTRS)
Cho, Y. I.; Crawford, D. W.; Back, L. H.; Back, M. R.
1987-01-01
A flow visualization study using selective dye injection and frame by frame analysis of a movie provided qualitative and quantitative data on the motion of marked fluid particles in a 60 degree artery branch model for simulation of physiological femoral artery flow. Physical flow features observed included jetting of the branch flow into the main lumen during the brief reverse flow period, flow separation along the main lumen wall during the near zero flow phase of diastole when the core flow was in the downstream direction, and inference of flow separation conditions along the wall opposite the branch later in systole at higher branch flow ratios. There were many similarities between dye particle motions in pulsatile flow and the comparative steady flow observations.
Microgravity two-phase fluid flow pattern modeling
NASA Technical Reports Server (NTRS)
Lee, Doojeong; Best, Frederick R.
1988-01-01
When gas and liquid mixtures flow in a pipe, the distribution of the two phases may take many forms. A flow pattern, or flow regime, is the characteristic spatial distribution of the phases of flow in a pipe. Because heat transfer and pressure drop are dependent on the characteristic distribution of phases, it is necessary to describe flow patterns in an appropriate manner so that a hydrodynamic or heat transfer theory applicable to that can be chosen. A theoretical two phase flow regime transition map under a microgravity environment was developed on physical concepts. These transitions use four basic flow patterns: dispersed flow, slug flow, stratified flow, and annular flow. The forces considered are body force, surface tension force, inertial force, friction, and the force from eddy turbulent fluctuation. Three dimensionless parameters were developed. Because these transition boundaries were developed based on physical concepts, they should be applicable to flow regimes occurring in various design conditions. Because the flow pattern data from KC-135 experiments are insufficient to verify these theoretical transition lines completely, an adiabatic experiment for flow regime analysis is recommended.
Development of Efficient Real-Fluid Model in Simulating Liquid Rocket Injector Flows
NASA Technical Reports Server (NTRS)
Cheng, Gary; Farmer, Richard
2003-01-01
The characteristics of propellant mixing near the injector have a profound effect on the liquid rocket engine performance. However, the flow features near the injector of liquid rocket engines are extremely complicated, for example supercritical-pressure spray, turbulent mixing, and chemical reactions are present. Previously, a homogeneous spray approach with a real-fluid property model was developed to account for the compressibility and evaporation effects such that thermodynamics properties of a mixture at a wide range of pressures and temperatures can be properly calculated, including liquid-phase, gas- phase, two-phase, and dense fluid regions. The developed homogeneous spray model demonstrated a good success in simulating uni- element shear coaxial injector spray combustion flows. However, the real-fluid model suffered a computational deficiency when applied to a pressure-based computational fluid dynamics (CFD) code. The deficiency is caused by the pressure and enthalpy being the independent variables in the solution procedure of a pressure-based code, whereas the real-fluid model utilizes density and temperature as independent variables. The objective of the present research work is to improve the computational efficiency of the real-fluid property model in computing thermal properties. The proposed approach is called an efficient real-fluid model, and the improvement of computational efficiency is achieved by using a combination of a liquid species and a gaseous species to represent a real-fluid species.
Arterial pulsation-driven cerebrospinal fluid flow in the perivascular space: a computational model.
Bilston, Lynne E; Fletcher, David F; Brodbelt, Andrew R; Stoodley, Marcus A
2003-08-01
This study was conducted to determine whether local arterial pulsations are sufficient to cause cerebrospinal fluid (CSF) flow along perivascular spaces (PVS) within the spinal cord. A theoretical model of the perivascular space surrounding a "typical" small artery was analysed using computational fluid dynamics. Systolic pulsations were modelled as travelling waves on the arterial wall. The effects of wave geometry and variable pressure conditions on fluid flow were investigated. Arterial pulsations induce fluid movement in the PVS in the direction of arterial wave travel. Perivascular flow continues even in the presence of adverse pressure gradients of a few kilopascals. Flow rates are greater with increasing pulse wave velocities and arterial deformation, as both an absolute amplitude and as a proportion of the PVS. The model suggests that arterial pulsations are sufficient to cause fluid flow in the perivascular space even against modest adverse pressure gradients. Local increases in flow in this perivascular pumping mechanism or reduction in outflow may be important in the etiology of syringomyelia.
Modeling the Effect of Fluid Flow on a Growing Network of Fractures in a Porous Medium
NASA Astrophysics Data System (ADS)
Alhashim, Mohammed; Koch, Donald
2015-11-01
The injection of a viscous fluid at high pressure in a geological formation induces the fracturing of pre-existing joints. Assuming a constant solid-matrix stress field, a weak joint saturated with fluid is fractured when the fluid pressure exceeds a critical value that depends on the joint's orientation. In this work, the formation of a network of fractures in a porous medium is modeled. When the average length of the fractures is much smaller than the radius of a cluster of fractured joints, the fluid flow within the network can be described as Darcy flow in a permeable medium consisting of the fracture network. The permeability and porosity of the medium are functions of the number density of activated joints and consequently depend on the fluid pressure. We demonstrate conditions under which these relationships can be derived from percolation theory. Fluid may also be lost from the fracture network by flowing into the permeable rock matrix. The solution of the model shows that the cluster radius grows as a power law with time in two regimes: (1) an intermediate time regime when the network contains many fractures but fluid loss is negligible; and (2) a long time regime when fluid loss dominates. In both regimes, the power law exponent depends on the Euclidean dimension and the injection rate dependence on time.
Unsteady fluid dynamic model for propeller induced flow fields
NASA Technical Reports Server (NTRS)
Katz, Joseph; Ashby, Dale L.; Yon, Steven
1991-01-01
A potential flow based three-dimensional panel method was modified to treat time dependent flow conditions in which the body's geometry may vary with time. The main objective of this effort was the study of a flow field due to a propeller rotating relative to a nonrotating body which is otherwise moving at a constant forward speed. Calculated surface pressure, thrust and torque coefficient data for a four-bladed marine propeller/body compared favorably with previously published experimental results.
Preece, D.S. Perkins, E.D.
1999-02-10
Techniques for modeling oil well sand production have been developed using the formulations for superquadric discrete elements and Darcy fluid flow. Discrete element models are generated using the new technique of particle cloning. Discrete element sources and sinks allow simulation of sand production from the initial state through the transition to an equilibrium state where particles are created and removed at the same rate.
An Integrative Model of Excitation Driven Fluid Flow in a 2D Uterine Channel
NASA Astrophysics Data System (ADS)
Maggio, Charles; Fauci, Lisa; Chrispell, John
2009-11-01
We present a model of intra-uterine fluid flow in a sagittal cross-section of the uterus by inducing peristalsis in a 2D channel. This is an integrative multiscale computational model that takes as input fluid viscosity, passive tissue properties of the uterine channel and a prescribed wave of membrane depolarization. This voltage pulse is coupled to a model of calcium dynamics inside a uterine smooth muscle cell, which in turn drives a kinetic model of myosin phosphorylation governing contractile muscle forces. Using the immersed boundary method, these muscle forces are communicated to a fluid domain to simulate the contractions which occur in a human uterus. An analysis of the effects of model parameters on the flow properties and emergent geometry of the peristaltic channel will be presented.
Fluid simulation of tokamak ion temperature gradient turbulence with zonal flow closure model
NASA Astrophysics Data System (ADS)
Yamagishi, Osamu; Sugama, Hideo
2016-03-01
Nonlinear fluid simulation of turbulence driven by ion temperature gradient modes in the tokamak fluxtube configuration is performed by combining two different closure models. One model is a gyrofluid model by Beer and Hammett [Phys. Plasmas 3, 4046 (1996)], and the other is a closure model to reproduce the kinetic zonal flow response [Sugama et al., Phys. Plasmas 14, 022502 (2007)]. By including the zonal flow closure, generation of zonal flows, significant reduction in energy transport, reproduction of the gyrokinetic transport level, and nonlinear upshift on the critical value of gradient scale length are observed.
Billeter, Thomas R.; Philipp, Lee D.; Schemmel, Richard R.
1976-01-01
A microwave fluid flow meter is described utilizing two spaced microwave sensors positioned along a fluid flow path. Each sensor includes a microwave cavity having a frequency of resonance dependent upon the static pressure of the fluid at the sensor locations. The resonant response of each cavity with respect to a variation in pressure of the monitored fluid is represented by a corresponding electrical output which can be calibrated into a direct pressure reading. The pressure drop between sensor locations is then correlated as a measure of fluid velocity. In the preferred embodiment the individual sensor cavities are strategically positioned outside the path of fluid flow and are designed to resonate in two distinct frequency modes yielding a measure of temperature as well as pressure. The temperature response can then be used in correcting for pressure responses of the microwave cavity encountered due to temperature fluctuations.
Oxygen isotopic transport and exchange during fluid flow: One-dimensional models and applications
Bowman, J.R. ); Willett, S.D. ); Cook, S.J. Environ Corp., Houston, TX )
1994-01-01
In this work the authors investigate the consequences of fluid flow and fluid-rock interaction to the isotopic evolution of fluids and rock with one-dimensional transport models of fluid flow and oxygen isotope exchange. Transport models dealing with stable isotopes are well established in recent geochemical literature. The authors extend previous treatments by presenting the derivation of both analytical and numerical solutions to the transport equations incorporating simultaneously advection, diffusion and hydrodynamic dispersion, and kinetics of isotopic exchange. The increased generality of numerical solutions allows the incorporation of other effects which control the spatial patterns of [delta][sup 18]O values developed in rocks and fluids including multiple reactive species and temperature gradients. The authors discuss the effects of flow parameters, conditions of isotopic exchange, and temperature gradients on the spatial patterns of isotopic shifts produced in rock sequences subjected to fluid flow, and on conventionally calculated W/R ratios for these rock sequences. Finally, the authors examine the implications of oxygen isotope transport for two natural systems where isotopic shifts or gradients could be interpreted in terms of unidirectional fluid infiltration. Solutions of one-dimensional transport equations including the mechanisms of advection, diffusion, hydrodynamic dispersion, and non-equilibrium exchange between water and rock indicate that the time-space evolution of oxygen isotopic compositions of rock and infiltrating fluid is dependent on (1) the rate of fluid infiltration, (2) the diffusive and dispersive properties of the rock matrix, (3) the rate of isotopic exchange, and (4) the rock-water mass oxygen ratio in a unit volume of water-saturated, porous rock. 56 refs., 18 figs., 2 tabs.
A two-phase solid/fluid model for dense granular flows including dilatancy effects
NASA Astrophysics Data System (ADS)
Mangeney, Anne; Bouchut, Francois; Fernandez-Nieto, Enrique; Koné, El-Hadj; Narbona-Reina, Gladys
2016-04-01
Describing grain/fluid interaction in debris flows models is still an open and challenging issue with key impact on hazard assessment [{Iverson et al.}, 2010]. We present here a two-phase two-thin-layer model for fluidized debris flows that takes into account dilatancy effects. It describes the velocity of both the solid and the fluid phases, the compression/dilatation of the granular media and its interaction with the pore fluid pressure [{Bouchut et al.}, 2016]. The model is derived from a 3D two-phase model proposed by {Jackson} [2000] based on the 4 equations of mass and momentum conservation within the two phases. This system has 5 unknowns: the solid and fluid velocities, the solid and fluid pressures and the solid volume fraction. As a result, an additional equation inside the mixture is necessary to close the system. Surprisingly, this issue is inadequately accounted for in the models that have been developed on the basis of Jackson's work [{Bouchut et al.}, 2015]. In particular, {Pitman and Le} [2005] replaced this closure simply by imposing an extra boundary condition at the surface of the flow. When making a shallow expansion, this condition can be considered as a closure condition. However, the corresponding model cannot account for a dissipative energy balance. We propose here an approach to correctly deal with the thermodynamics of Jackson's model by closing the mixture equations by a weak compressibility relation following {Roux and Radjai} [1998]. This relation implies that the occurrence of dilation or contraction of the granular material in the model depends on whether the solid volume fraction is respectively higher or lower than a critical value. When dilation occurs, the fluid is sucked into the granular material, the pore pressure decreases and the friction force on the granular phase increases. On the contrary, in the case of contraction, the fluid is expelled from the mixture, the pore pressure increases and the friction force diminishes. To
Experimental Investigation and Pore-Scale Modeling of Non-Newtonian Fluid Flow in Porous Media
NASA Astrophysics Data System (ADS)
Hauswirth, S.; Dye, A. L.; Miller, C. T.; Tapscott, C.; Schultz, P. B.
2015-12-01
Systems involving the flow of non-Newtonian fluids in porous media arise in a number of settings, including hydraulic fracturing, enhanced oil recovery, contaminant remediation, and biological systems. Development of accurate macroscale models of such systems requires an understanding of the relationship between the fluid and medium properties at the microscale and averaged macroscale properties. This study investigates the flow of aqueous solutions of guar gum, a major component of hydraulic fracturing fluids that exhibits Cross model rheological behavior. The rheological properties of solutions containing varying concentrations of guar gum were characterized using a rotational rheometer and the data were fit to a model relating viscosity to shear rate and concentration. Flow experiments were conducted in a porous medium-packed column to measure the pressure response during the flow of guar gum solutions at a wide range of flow rates and determine apparent macroscale viscosities and shear rates. To investigate the relationship between the fluid rheology, microscale physics, and the observed macroscale properties, a lattice Boltzmann pore scale simulator incorporating non-Newtonian behavior was developed. The model was validated, then used to simulate systems representative of the column experiments, allowing direct correlation of detailed microscale physics to the macroscale observations.
Chemical vapor deposition fluid flow simulation modelling tool
NASA Technical Reports Server (NTRS)
Bullister, Edward T.
1992-01-01
Accurate numerical simulation of chemical vapor deposition (CVD) processes requires a general purpose computational fluid dynamics package combined with specialized capabilities for high temperature chemistry. In this report, we describe the implementation of these specialized capabilities in the spectral element code NEKTON. The thermal expansion of the gases involved is shown to be accurately approximated by the low Mach number perturbation expansion of the incompressible Navier-Stokes equations. The radiative heat transfer between multiple interacting radiating surfaces is shown to be tractable using the method of Gebhart. The disparate rates of reaction and diffusion in CVD processes are calculated via a point-implicit time integration scheme. We demonstrate the use above capabilities on prototypical CVD applications.
Morin, Kristen T; Lenz, Michelle S; Labat, Caroline A; Tranquillo, Robert T
2015-05-01
Knowledge is limited about fluid flow in tissues containing engineered microvessels, which can be substantially different in topology than native capillary networks. A need exists for a computational model that allows for flow through tissues dense in nonpercolating and possibly nonperfusable microvessels to be efficiently evaluated. A finite difference (FD) model based on Poiseuille flow through a distribution of straight tubes acting as point sources and sinks, and Darcy flow through the interstitium, was developed to describe fluid flow through a tissue containing engineered microvessels. Accuracy of the FD model was assessed by comparison to a finite element (FE) model for the case of a single tube. Because the case of interest is a tissue with microvessels aligned with the flow, accuracy was also assessed in depth for a corresponding 2D FD model. The potential utility of the 2D FD model was then explored by correlating metrics of flow through the model tissue to microvessel morphometric properties. The results indicate that the model can predict the density of perfused microvessels based on parameters that can be easily measured. PMID:25424905
Predictions of bubbly flows in vertical pipes using two-fluid models in CFDS-FLOW3D code
Banas, A.O.; Carver, M.B.; Unrau, D.
1995-09-01
This paper reports the results of a preliminary study exploring the performance of two sets of two-fluid closure relationships applied to the simulation of turbulent air-water bubbly upflows through vertical pipes. Predictions obtained with the default CFDS-FLOW3D model for dispersed flows were compared with the predictions of a new model (based on the work of Lee), and with the experimental data of Liu. The new model, implemented in the CFDS-FLOW3D code, included additional source terms in the {open_quotes}standard{close_quotes} {kappa}-{epsilon} transport equations for the liquid phase, as well as modified model coefficients and wall functions. All simulations were carried out in a 2-D axisymmetric format, collapsing the general multifluid framework of CFDS-FLOW3D to the two-fluid (air-water) case. The newly implemented model consistently improved predictions of radial-velocity profiles of both phases, but failed to accurately reproduce the experimental phase-distribution data. This shortcoming was traced to the neglect of anisotropic effects in the modelling of liquid-phase turbulence. In this sense, the present investigation should be considered as the first step toward the ultimate goal of developing a theoretically sound and universal CFD-type two-fluid model for bubbly flows in channels.
NASA Astrophysics Data System (ADS)
Dietterich, H. R.; Lev, E.; Chen, J.; Cashman, K. V.; Honor, C.
2015-12-01
Recent eruptions in Hawai'i, Iceland, and Cape Verde highlight the need for improved lava flow models for forecasting and hazard assessment. Existing models used for lava flow simulation range in assumptions, complexity, and the degree to which they have been validated against analytical solutions, experiments, and natural observations. In order to assess the capabilities of existing models and test the development of new codes, we conduct a benchmarking study of computational fluid dynamics models for lava flows, including VolcFlow, OpenFOAM, Flow3D, and COMSOL. Using new benchmark scenarios defined in Cordonnier et al. (2015) as a guide, we model Newtonian, Herschel-Bulkley and cooling flows over inclined planes, obstacles, and digital elevation models with a wide range of source conditions. Results are compared to analytical theory, analogue and molten basalt experiments, and measurements from natural lava flows. Our study highlights the strengths and weakness of each code, including accuracy and computational costs, and provides insights regarding code selection. We apply the best-fit codes to simulate the lava flows in Harrat Rahat, a predominately mafic volcanic field in Saudi Arabia. Input parameters are assembled from rheology and volume measurements of past flows using geochemistry, crystallinity, and present-day lidar and photogrammetric digital elevation models. With these data, we use our verified models to reconstruct historic and prehistoric events, in order to assess the hazards posed by lava flows for Harrat Rahat.
Dynamic coupling between fluid flow and vein growth in fractures: a 3D numerical model
NASA Astrophysics Data System (ADS)
Schwarz, J.-O.; Enzmann, F.
2012-04-01
Fluid flow is one of the main mass transport mechanisms in the Earth's crust and abundant mineral vein networks are important indicators for fluid flow and fluid rock interaction. These systems are dynamic and part of the so called RTM processes (reaction-transport-mechanics). Understanding of mineral vein systems requires coupling of these processes. Here we present a conceptional model for dynamic vein growth of syntaxial, posttectonic veins generated by advective fluid flow and show first results of a numerical model for this scenario. Vein generation requires three processes to occur: (i) fracture generation by mechanical stress e.g. hydro-fracturing, (ii) flow of a supersaturated fluid on that fracture and (iii) crystallization of phase(s) on or in the fracture. 3D synthetic fractures are generated with the SynFrac code (Ogilvie, et al. 2006). Subsequently solutions of the Navier-Stokes equation for this fracture are computed by a computational fluid dynamics code called GeoDict (Wiegmann 2007). Transport (advective and diffusive) of chemical species to growth sites in the fracture and vein growth are computed by a self-written MATLAB script. The numerical model discretizes the wall rock and fracture geometry by volumetric pixels (voxels). Based on this representation, the model computes the three basic functions for vein generation: (a) nucleation, (b) fluid flow with transport of chemical species and (c) growth. The following conditions were chosen for these three modules. Nucleation is heterogeneous and occurs instantaneously at the wall rock/fracture interface. Advective and diffusive flow of a supersaturated fluid and related transport of chemical species occurs according to the computed fluid flow field by GeoDict. Concentration of chemical species at the inflow is constant, representing external fluid buffering. Changes/decrease in the concentration of chemical species occurs only due to vein growth. Growth of nuclei is limited either by transport of
Pulsatile flow of blood using a modified second-grade fluid model
Massoudi, Mehrdad; Tran, P.X.
2008-07-01
We study the unsteady pulsatile flow of blood in an artery, where the effects of body acceleration are included. The blood is modeled as a modified second-grade fluid where the viscosity and the normal stress coefficients depend on the shear rate. It is assumed that the blood near the wall behaves as a Newtonian fluid, and in the core as a non-Newtonian fluid. This phenomenon is also known as the Fahraeus–Lindqvist effect. The equations are made dimensionless and solved numerically.
Hutnak, M.; Hurwitz, S.; Ingebritsen, S.E.; Hsieh, P.A.
2009-01-01
Ground surface displacement (GSD) in large calderas is often interpreted as resulting from magma intrusion at depth. Recent advances in geodetic measurements of GSD, notably interferometric synthetic aperture radar, reveal complex and multifaceted deformation patterns that often require complex source models to explain the observed GSD. Although hydrothermal fluids have been discussed as a possible deformation agent, very few quantitative studies addressing the effects of multiphase flow on crustal mechanics have been attempted. Recent increases in the power and availability of computing resources allow robust quantitative assessment of the complex time-variant thermal interplay between aqueous fluid flow and crustal deformation. We carry out numerical simulations of multiphase (liquid-gas), multicomponent (H 2O-CO2) hydrothermal fluid flow and poroelastic deformation using a range of realistic physical parameters and processes. Hydrothermal fluid injection, circulation, and gas formation can generate complex, temporally and spatially varying patterns of GSD, with deformation rates, magnitudes, and geometries (including subsidence) similar to those observed in several large calderas. The potential for both rapid and gradual deformation resulting from magma-derived fluids suggests that hydrothermal fluid circulation may help explain deformation episodes at calderas that have not culminated in magmatic eruption.
Fluid friction and wall viscosity of the 1D blood flow model.
Wang, Xiao-Fei; Nishi, Shohei; Matsukawa, Mami; Ghigo, Arthur; Lagrée, Pierre-Yves; Fullana, Jose-Maria
2016-02-29
We study the behavior of the pulse waves of water into a flexible tube for application to blood flow simulations. In pulse waves both fluid friction and wall viscosity are damping factors, and difficult to evaluate separately. In this paper, the coefficients of fluid friction and wall viscosity are estimated by fitting a nonlinear 1D flow model to experimental data. In the experimental setup, a distensible tube is connected to a piston pump at one end and closed at another end. The pressure and wall displacements are measured simultaneously. A good agreement between model predictions and experiments was achieved. For amplitude decrease, the effect of wall viscosity on the pulse wave has been shown as important as that of fluid viscosity. PMID:26862041
Fluid friction and wall viscosity of the 1D blood flow model.
Wang, Xiao-Fei; Nishi, Shohei; Matsukawa, Mami; Ghigo, Arthur; Lagrée, Pierre-Yves; Fullana, Jose-Maria
2016-02-29
We study the behavior of the pulse waves of water into a flexible tube for application to blood flow simulations. In pulse waves both fluid friction and wall viscosity are damping factors, and difficult to evaluate separately. In this paper, the coefficients of fluid friction and wall viscosity are estimated by fitting a nonlinear 1D flow model to experimental data. In the experimental setup, a distensible tube is connected to a piston pump at one end and closed at another end. The pressure and wall displacements are measured simultaneously. A good agreement between model predictions and experiments was achieved. For amplitude decrease, the effect of wall viscosity on the pulse wave has been shown as important as that of fluid viscosity.
Numerical Modeling on Two phase Fluid flow in a Coupled Fracture-Skin-Matrix System
NASA Astrophysics Data System (ADS)
Valsala Kumari, R.; G, S. K.
2015-12-01
Multiphase flow modeling studies below the ground surface is very essential for designing suitable remediation strategies for contaminated aquifers and for the development of petroleum and geothermal reservoirs. Presence of fractured bedrock beneath the ground surface will make multiphase flow process more complex due to its highly heterogeneous nature. A major challenge in modeling flow within a fractured rock is to capture the interaction between the high permeability fracture and the low permeability rock-matrix. In some instances, weathering and mineral depositions will lead to formation of an additional layer named fracture-skin at the fracture-matrix interface. Porosity and permeability of fracture-skin may significantly vary from the adjacent rock matrix and this variation will result in different flow and transport behavior within the fracture-skin. In the present study, an attempt has been made to model simultaneous flow of two immiscible phases (water and LNAPL) in a saturated coupled fracture-skin-matrix system. A fully-implicit finite difference model has been developed to simulate the variation of pressure and saturation of fluid phases along the fracture and within the rock-matrix. Sensitivity studies have been done to analyze the effect of change of various fracture-skin parameters such as porosity, diffusion coefficient and thickness on pressure and saturation distribution of both wetting and non-wetting fluid phases. It can be concluded from the study that the presence of fracture-skin is significantly affecting the fluid flow at the fracture-matrix interface and it can also be seen from the study that the flow behavior of both fluid phases is sensitive to fracture-skin parameters.
Massoudi, M.C.; Tran, P.X.
2007-06-15
After providing a brief review of the constitutive modeling of the stress tensor for granular materials using non-Newtonian fluid models, we study the flow between two horizontal flat plates. It is assumed that the granular media behaves as a non-Newtonian fluid (of the Reiner–Rivlin type); we use the constitutive relation derived by Rajagopal and Massoudi [Rajagopal, K. R. and M. Massoudi, “A Method for measuring material moduli of granular materials: flow in an orthogonal rheometer,” Topical Report, DOE/PETC/TR-90/3, 1990] which can predict the normal stress differences. The lower plate is fixed and heated, and the upper plate (which is at a lower temperature than the lower plate) is set into motion with a constant velocity. The steady fully developed flow and the heat transfer equations are made dimensionless and are solved numerically; the effects of different dimensionless numbers and viscous dissipation are discussed.
Fluid flow model of the Cerro Prieto Geothermal Field based on well log interpretation
Halfman, S.E.; Lippmann, M.J.; Zelwe, R.; Howard, J.H.
1982-08-10
The subsurface geology of the Cerro Prieto geothermal field was analyzed using geophysical and lithologic logs. The distribution of permeable and relatively impermeable units and the location of faults are shown in a geologic model of the system. By incorporating well completion data and downhole temperature profiles into the geologic model, it was possible to determine the direction of geothermal fluid flow and the role of subsurface geologic features that control this movement.
Fluid flow model of the Cerro Prieto geothermal field based on well log interpretation
Halfman, S.E.; Lippmann, M.J.; Zelwer, R.; Howard, J.H.
1982-10-01
The subsurface geology of the Cerro Prieto geothermal field was analyzed using geophysical and lithologic logs. The distribution of permeable and relatively impermeable units and the location of faults are shown in a geologic model of the system. By incorporating well completion data and downhole temperature profiles into the geologic model, it was possible to determine he direction of geothermal fluid flow and the role of subsurface geologic features that control this movement.
Numerical Modeling of Multiphase Fluid Flow in Ore-Forming Hydrothermal Systems
NASA Astrophysics Data System (ADS)
Weis, P.; Driesner, T.; Coumou, D.; Heinrich, C. A.
2007-12-01
Two coexisting fluid phases - a variably saline liquid and a vapor phase - are ubiquitous in ore-forming and other hydrothermal systems. Understanding the dynamics of phase separation and the distinct physical and chemical evolution of the two fluids probably plays a key role in generating different ore deposit types, e.g. porphyry type, high and low sulfidation Cu-Mo-Au deposits. To this end, processes within hydrothermal systems have been studied with a refined numerical model describing fluid flow in transient porous media (CSP~5.0). The model is formulated on a mass, energy and momentum conserving finite-element-finite-volume (FEFV) scheme and is capable of simulating multiphase flow of NaCl-H20 fluids. Fluid properties are computed from an improved equation of state (SOWAT~2.0). It covers conditions with temperatures of up to 1000 degrees~C, pressures of up to 500 MPa, and fluid salinities of 0~to 100%~NaCl. In particular, the new set-up allows for a more accurate description of fluid phase separation during boiling of hydrothermal fluids into a vapor and a brine phase. The geometric flexibility of the FEFV-meshes allows for investigations of a large variety of geological settings, ranging from ore-forming processes in magmatic hydrothermal system to the dynamics of black smokers at mid-ocean ridges. Simulations demonstrated that hydrothermal convection patterns above cooling plutons are primarily controlled by the system-scale permeability structure. In porphyry systems, high fluid pressures develop in a stock rising from the magma chamber which can lead to rock failure and, eventually, an increase in permeability due to hydrofracturing. Comparisons of the thermal evolution as inferred from modeling studies with data from fluid inclusion studies of the Pb-Zn deposits of Madan, Bulgaria are in a strikingly good agreement. This indicates that cross-comparisons of field observations, analytical data and numerical simulations will become a powerful tool towards a
SPH-DCDEM model for arbitrary geometries in free surface solid-fluid flows
NASA Astrophysics Data System (ADS)
Canelas, Ricardo B.; Crespo, Alejandro J. C.; Domínguez, Jose M.; Ferreira, Rui M. L.; Gómez-Gesteira, Moncho
2016-05-01
A unified discretization of rigid solids and fluids is introduced, allowing for resolved simulations of fluid-solid phases within a meshless framework. The numerical solution, attained by Smoothed Particle Hydrodynamics (SPH) and a variation of Discrete Element Method (DEM), the Distributed Contact Discrete Element Method (DCDEM) discretization, is achieved by directly considering solid-solid and solid-fluid interactions. The novelty of the work is centred on the generalization of the coupling of the DEM and SPH methodologies for resolved simulations, allowing for state-of-the-art contact mechanics theories to be used in arbitrary geometries, while fluid to solid and vice versa momentum transfers are accurately described. The methods are introduced, analysed and discussed. Initial validations on the DCDEM and the fluid coupling are presented, drawing from test cases in the literature. An experimental campaign serves as a validation point for complex, large scale solid-fluid flows, where a set of blocks in several configurations is subjected to a dam-break wave. Blocks are tracked and positions are then compared between experimental data and the numerical solutions. A Particle Image Velocimetry (PIV) technique allows for the quantification of the flow field and direct comparison with numerical data. The results show that the model is accurate and is capable of treating highly complex interactions, such as transport of debris or hydrodynamic actions on structures, if relevant scales are reproduced.
A Rayleigh-Plesset based transport model for cryogenic fluid cavitating flow computations
NASA Astrophysics Data System (ADS)
Shi, SuGuo; Wang, GuoYu; Hu, ChangLi
2014-04-01
The present article focuses on modeling issues to simulate cryogenic fluid cavitating flows. A revised cavitation model, in which the thermal effect is considered, is derivated and established based on Kubota model. Cavitating flow computations are conducted around an axisymmetric ogive and a 2D quarter caliber hydrofoil in liquid nitrogen implementing the revised model and Kubota model coupled with energy equation and dynamically updating the fluid physical properties, respecitively. The results show that the revised cavitation model can better describe the mass transport process in the cavitation process in cryogenic fluids. Compared with Kubota model, the revised model can reflect the observed "frosty" appearance within the cavity. The cavity length becomes shorter and it can capture the temperature and pressure depressions more consistently in the cavitating region, particularly at the rear of the cavity. The evaporation rate decreases, and while the magnitude of the condensation rate becomes larger because of the thermal effect terms in the revised model compared with the results obtained by the Kubota model.
Multiscale computational model of fluid flow and matrix deformation in decellularized liver.
Nishii, Kenichiro; Reese, Greg; Moran, Emma C; Sparks, Jessica L
2016-04-01
Currently little is known about the biomechanical environment in decellularized tissue. The goal of this research is to quantify the mechanical microenvironment in decellularized liver, for varying organ-scale perfusion conditions, using a combined experimental/computational approach. Needle-guided ultra-miniature pressure sensors were inserted into liver tissue to measure parenchymal fluid pressure ex-situ in portal vein-perfused native (n=5) and decellularized (n=7) ferret liver, for flow rates from 3-12mL/min. Pressures were also recorded at the inlet near the portal vein cannula to estimate total vascular resistance of the specimens. Experimental results were fit to a multiscale computational model to simulate perfusion conditions inside native versus decellularized livers for four experimental flow rates. The multiscale model consists of two parts: an organ-scale electrical analog model of liver hemodynamics and a tissue-scale model that predicts pore fluid pressure, pore fluid velocity, and solid matrix stress and deformation throughout the 3D hepatic lobule. Distinct models were created for native versus decellularized liver. Results show that vascular resistance decreases by 82% as a result of decellularization. The hydraulic conductivity of the decellularized liver lobule, a measure of tissue permeability, was 5.6 times that of native liver. For the four flow rates studied, mean fluid pressures in the decellularized lobule were 0.6-2.4mmHg, mean fluid velocities were 211-767μm/s, and average solid matrix principal strains were 1.7-6.1%. In the future this modeling platform can be used to guide the optimization of perfusion seeding and conditioning strategies for decellularized scaffolds in liver bioengineering.
NASA Astrophysics Data System (ADS)
Pan, Peng-Zhi; Rutqvist, Jonny; Feng, Xia-Ting; Yan, Fei
2014-03-01
In this paper, the two computer codes TOUGH2 and RDCA (for "rock discontinuous cellular automaton") are integrated for coupled hydromechanical analysis of multiphase fluid flow and discontinuous mechanical behavior in heterogeneous rock. TOUGH2 is a well-established code for geohydrological analysis involving multiphase, multicomponent fluid flow and heat transport; RDCA is a numerical model developed for simulating the nonlinear and discontinuous geomechanical behavior of rock. The RDCA incorporates the discontinuity of a fracture independently of the mesh, such that the fracture can be arbitrarily located within an element, while the fluid pressure calculated by TOUGH2 can be conveniently applied to fracture surfaces. We verify and demonstrate the coupled TOUGH-RDCA simulator by modeling a number of simulation examples related to coupled multiphase flow and geomechanical processes associated with the deep geological storage of carbon dioxide—including modeling of ground surface uplift, stress-dependent permeability, and the coupled multiphase flow and geomechanical behavior of fractures intersecting the caprock.
NASA Astrophysics Data System (ADS)
Wu, Xiao-Gang; Yu, Wei-Lun; Cen, Hai-Peng; Wang, Yan-Qin; Guo, Yuan; Chen, Wei-Yi
2015-02-01
A hierarchical model is developed to predict the streaming potential (SP) in the canaliculi of a loaded osteon. Canaliculi are assumed to run straight across the osteon annular cylinder wall, while disregarding the effect of lacuna. SP is generalized by the canalicular fluid flow. Analytical solutions are obtained for the canalicular fluid velocity, pressure, and SP. Results demonstrate that SP amplitude (SPA) is proportional to the pressure difference, strain amplitude, frequency, and strain rate amplitude. However, the key loading factor governing SP is the strain rate, which is a representative loading parameter under the specific physiological state. Moreover, SPA is independent of canalicular length. This model links external loads to the canalicular fluid pressure, velocity, and SP, which can facilitate further understanding of the mechanotransduction and electromechanotransduction mechanisms of bones.
Three-dimensional Oldroyd-B fluid flow with Cattaneo-Christov heat flux model
NASA Astrophysics Data System (ADS)
Shehzad, S. A.; Hayat, T.; Abbasi, F. M.; Javed, Tariq; Kutbi, M. A.
2016-04-01
The impact of Cattaneo-Christov heat flux in three-dimensional flow of an Oldroyd-B fluid over a bidirectional stretching surface is explored in this article. The boundary layer flow of an incompressible fluid is considered. Heat transfer analysis is discussed via the Cattaneo-Christov model of heat flux. Similarity transformations lead to the nonlinear ordinary differential systems. Convergent solutions of dimensionless velocities and temperature have been computed. Convergence analysis is presented graphically and numerically. The influence of physical parameters on the velocities and temperature are plotted and discussed. We observed that the values of temperature gradient are higher for the Cattaneo-Christov heat flux model when we compare it with the values obtained by the simple Fourier's law of heat conduction.
NASA Astrophysics Data System (ADS)
Antonellini, Marco; Nella Mollema, Pauline
2016-04-01
Surface outcrops provide natural analogs for aquifers and they offer an opportunity to study the geometry of geologic heterogeneities in three dimensions over a range of scales. We show photographs, maps, quantitative field data of rock fractures and sedimentary features in outcrops exposed in a unique collection of many different settings. These include small-scale sedimentary structures, carbonate nodules, faults, and other fractures as documented in outcrops of porous sandstone (Utah, USA and Italy), tight sandstones (Bolivia), dolomite (Northern Italy), and carbonates (Central Italy). We simulate the geometries observed in outcrops with simple conceptual and numerical models of flow to show how important it is to recognize the appropriate attributes for the description and the process responsible for the formation of geologic heterogeneities. For example, knowing the type of structural heterogeneities (fault, joint, compaction band, stylolite, and vein) and their development mechanics helps to predict the distribution and preferential orientation of these features within an aquifer. This knowledge is particularly important for modeling of fluid flow where geophysical or borehole data are lacking. Geologic heterogeneities of sedimentary, structural or diagenetic (chemical) nature influence the fluid flow properties in many aquifers and reservoirs at scales varying over several orders of magnitude and with a spatial variability ranging from mm to tens of meters. Heterogeneities may enhance or degrade porosity and permeability, they impart anisotropy to permeability and dispersion and affect mass transport-related processes in groundwater. Furthermore, aquifer heterogeneities control aquifer continuity and compartmentalization. In fractured aquifers, geologic and diagenetic heterogeneities may affect connectivity, aperture of the flow channels or the distribution of permeability buffers, barriers and seals. Also variations in layer thickness and lithology within a
Magnetically stimulated fluid flow patterns
Martin, Jim; Solis, Kyle
2016-07-12
Sandia National Laboratories' Jim Martin and Kyle Solis explain research on the effects of magnetic fields on fluid flows and how they stimulate vigorous flows. Fluid flow is a necessary phenomenon in everything from reactors to cooling engines in cars.
Magnetically stimulated fluid flow patterns
Martin, Jim; Solis, Kyle
2014-03-06
Sandia National Laboratories' Jim Martin and Kyle Solis explain research on the effects of magnetic fields on fluid flows and how they stimulate vigorous flows. Fluid flow is a necessary phenomenon in everything from reactors to cooling engines in cars.
NASA Astrophysics Data System (ADS)
Horiuchi, Shun-suke; Iwamori, Hikaru
2016-05-01
Water plays crucial roles in the subduction zone dynamics affecting the thermal-flow structure through the fluid processes. We aim to understand what controls the dynamics and construct a model to solve consistently fluid generation, fluid transport, its reaction with the solid and resultant viscosity, and thermal-flow structure. We highlight the effect of mechanical weakening of rocks associated with hydration. The viscosity of serpentinite (ηserp) in subduction zones critically controls the flow-thermal structure via extent of mechanical coupling between the subducting slab and overlying mantle wedge. When ηserp is greater than 1021 Pa s, the thermal-flow structure reaches a steady state beneath the volcanic zone, and the melting region expands until Cin (initial water content in the subducting oceanic crust) reaches 3 wt %, and it does not expand from 3 wt %. On the other hand, when ηserp is less than 1019 Pa s, the greater water dependence of viscosity (expressed by a larger fv) confines a hot material to a narrower channel intruding into the wedge corner from a deeper part of the back-arc region. Consequently, the overall heat flux becomes less for a larger fv. When ageba (age of back-arc basin as a rifted lithosphere) = 7.5 Ma, the increase in fv weakens but shifts the melting region toward the trench side because of the narrow channel flow intruding into the wedge corner, where as it shuts down melting when ageba=20 Ma. Several model cases (particularly those with ηserp=1020 to 1021 Pa s and a relatively large fv for Cin=2 to 3 wt %) broadly account for the observations in the Northeast Japan arc (i.e., location and width of volcanic chain, extent of serpentinite, surface heat flow, and seismic tomography), although the large variability of surface heat flow and seismic tomographic images does not allow us to constrain the parameter range tightly.
NASA Astrophysics Data System (ADS)
Abdelaziz, Ramadan; Sussumu Komori, Fabio
2015-04-01
Recently, Lattice Boltzmann Modelling (LBM) techniques attract many scientists in various fields of research. This work shows the capability for LBM to simulate the fluid flow and solute transport in porous and fracture media, additionally, how to study behavior of nanofluids submitted to a temperature gradient, which it is an important process in natural aquatic environments, water treatment, and other water related technologies. LBSim is used in this work as Lattice Boltzmann Model simulator software. In this article, a series of cases using the lattice Boltzmann method are presented, showing the capability of the method in simulating phenomena with fluid flow and heat transfer in porous media. Results show that the lattice Boltzmann method delivers reliable and helpful simulations for the analyses of processes in water related technologies. Thus, LBSim is a recommended tool for simulating fluid flow at laminar and turbulent condition, and heat and mass transport under complex geometry and boundary condition. parameter values. Keywords: Lattice Boltzmann Model, LBSim, Fractures Media, Porous Media, nanofluids
Fibroblast alignment under interstitial fluid flow using a novel 3-D tissue culture model.
Ng, Chee Ping; Swartz, Melody A
2003-05-01
Interstitial flow is an important component of the microcirculation and interstitial environment, yet its effects on cell organization and tissue architecture are poorly understood, in part due to the lack of in vitro models. To examine the effects of interstitial flow on cell morphology and matrix remodeling, we developed a tissue culture model that physically supports soft tissue cultures and allows microscopic visualization of cells within the three-dimensional matrix. In addition, pressure-flow relationships can be continuously monitored to evaluate the bulk hydraulic resistance as an indicator of changes in the overall matrix integrity. We observed that cells such as human dermal fibroblasts aligned perpendicular to the direction of interstitial flow. In contrast, fibroblasts in static three-dimensional controls remained randomly oriented, whereas cells subjected to fluid shear as a two-dimensional monolayer regressed. Also, the dynamic measurements of hydraulic conductivity suggest reorganization toward a steady state. These primary findings help establish the importance of interstitial flow on the biology of tissue organization and interstitial fluid balance. PMID:12531726
Otto Laporte Lecture: Fluid Dynamics Prize Talk: Simple Models for Turbulent Flows
NASA Astrophysics Data System (ADS)
Pope, Stephen B.
2009-11-01
We focus on the modeling of two turbulent flows: dispersion from a line source in grid turbulence; and, a lifted non-premixed turbulent jet flame. Stochastic Lagrangian models and PDF methods are described, and are shown to model these flows satisfactorily. For the line source, a Lagrangian approach is taken, with the Langevin equation modeling the velocity following a fluid particle, and with a simple relaxation model for the particle temperature. Comparison with experimental data shows that the resulting model describes accurately the dispersion from single and multiple line sources. These simple stochastic Lagrangian models are then applied to the much more challenging case of a lifted non-premixed jet flame. The stochastic Lagrangian models form the basis for a particle/mesh numerical method for solving a modeled transport equation for the Eulerian joint probability density function (PDF) of velocity and composition. The PDF calculations are in excellent agreement with the experimental data, and exhibit the observed extreme sensitivity of the flame to the temperature of the co-flow. The PDF model calculations presented clearly demonstrate that simple models can be very useful, even though aspects of their behavior may be inaccurate or incomplete. The shortcomings of the Langevin equation are examined, and more advanced models (designed to overcome some of these shortcomings) are described. These include models for fluid-particle acceleration, including the effects of intermittency; models accounting for mean shear, which are correct in the rapid- distortion limit; and models designed for use in conjunction with large-eddy simulations (LES).
NASA Technical Reports Server (NTRS)
Adeniji-Fashola, A. A.
1988-01-01
A multiple-realization particle trajectory scheme has been developed and applied to the numerical prediction of confined turbulent fluid-particle flows. The example flows investigated include the vertical pipe upflow experimental data of Tsuji et al. and the experimental data of Leavitt for a coaxial jet flow, comprising a particle-laden central jet and a clean annular jet, into a large recirculation chamber. The results obtained from the numerical scheme agree well with the experimental data, lending confidence to the modeling approach. The multiple-realization particle trajectory turbulent flow modeling scheme is believed to be a more elegant and accurate approach to the extension of single-particle hydrodynamics to dilute multi-particle systems than the more commonly employed two-fluid modeling approach. It is also better able to incorporate additional force items such as lift, virtual mass and Bassett history terms directly into the particle equation of motion as appropriate. This makes it a suitable candidate for particle migration studies and an extension to situations involving liquid particulate phases with possible propulsion applications, such as in spray combustion, follows naturally.
Prediction of Parameters Distribution of Upward Boiling Two-Phase Flow With Two-Fluid Models
Yao, Wei; Morel, Christophe
2002-07-01
In this paper, a multidimensional two-fluid model with additional turbulence k - {epsilon} equations is used to predict the two-phase parameters distribution in freon R12 boiling flow. The 3D module of the CATHARE code is used for numerical calculation. The DEBORA experiment has been chosen to evaluate our models. The radial profiles of the outlet parameters were measured by means of an optical probe. The comparison of the radial profiles of void fraction, liquid temperature, gas velocity and volumetric interfacial area at the end of the heated section shows that the multidimensional two-fluid model with proper constitutive relations can yield reasonably predicted results in boiling conditions. Sensitivity tests show that the turbulent dispersion force, which involves the void fraction gradient, plays an important role in determining the void fraction distribution; and the turbulence eddy viscosity is a significant factor to influence the liquid temperature distribution. (authors)
Fedosov, Dmitry A.; Karniadakis, George Em; Caswell, Bruce
2010-01-01
Polymer fluids are modeled with dissipative particle dynamics (DPD) as undiluted bead-spring chains and their solutions. The models are assessed by investigating their steady shear-rate properties. Non-Newtonian viscosity and normal stress coefficients, for shear rates from the lower to the upper Newtonian regimes, are calculated from both plane Couette and plane Poiseuille flows. The latter is realized as reverse Poiseuille flow (RPF) generated from two Poiseuille flows driven by uniform body forces in opposite directions along two-halves of a computational domain. Periodic boundary conditions ensure the RPF wall velocity to be zero without density fluctuations. In overlapping shear-rate regimes the RPF properties are confirmed to be in good agreement with those calculated from plane Couette flow with Lees–Edwards periodic boundary conditions (LECs), the standard virtual rheometer for steady shear-rate properties. The concentration and the temperature dependence of the properties of the model fluids are shown to satisfy the principles of concentration and temperature superposition commonly employed in the empirical correlation of real polymer-fluid properties. The thermodynamic validity of the equation of state is found to be a crucial factor for the achievement of time-temperature superposition. With these models, RPF is demonstrated to be an accurate and convenient virtual rheometer for the acquisition of steady shear-rate rheological properties. It complements, confirms, and extends the results obtained with the standard LEC configuration, and it can be used with the output from other particle-based methods, including molecular dynamics, Brownian dynamics, smooth particle hydrodynamics, and the lattice Boltzmann method. PMID:20405981
Fedosov, Dmitry A; Karniadakis, George Em; Caswell, Bruce
2010-04-14
Polymer fluids are modeled with dissipative particle dynamics (DPD) as undiluted bead-spring chains and their solutions. The models are assessed by investigating their steady shear-rate properties. Non-Newtonian viscosity and normal stress coefficients, for shear rates from the lower to the upper Newtonian regimes, are calculated from both plane Couette and plane Poiseuille flows. The latter is realized as reverse Poiseuille flow (RPF) generated from two Poiseuille flows driven by uniform body forces in opposite directions along two-halves of a computational domain. Periodic boundary conditions ensure the RPF wall velocity to be zero without density fluctuations. In overlapping shear-rate regimes the RPF properties are confirmed to be in good agreement with those calculated from plane Couette flow with Lees-Edwards periodic boundary conditions (LECs), the standard virtual rheometer for steady shear-rate properties. The concentration and the temperature dependence of the properties of the model fluids are shown to satisfy the principles of concentration and temperature superposition commonly employed in the empirical correlation of real polymer-fluid properties. The thermodynamic validity of the equation of state is found to be a crucial factor for the achievement of time-temperature superposition. With these models, RPF is demonstrated to be an accurate and convenient virtual rheometer for the acquisition of steady shear-rate rheological properties. It complements, confirms, and extends the results obtained with the standard LEC configuration, and it can be used with the output from other particle-based methods, including molecular dynamics, Brownian dynamics, smooth particle hydrodynamics, and the lattice Boltzmann method.
Fluid flow, mineral reactions, and metasomatism
Ferry, J.M.; Dipple, G.M. )
1991-03-01
A general model that relates fluid flow along a temnperature gradient to chemical reaction in rocks can be used to quantitatively interpret petrologic and geochemical data on metasomatism from ancient flow systems in terms of flow direction and time-integrated fluid flux. The model is applied to regional metamorphism, quartz veins, and a metasomatized ductile fault zone.
A two-fluid model for particle acceleration and dynamics in black-hole accretion flows
NASA Astrophysics Data System (ADS)
Lee, Jason P.
Hot, tenuous Advection-Dominated Accretion Flows (ADAFs) are ideal sites for the Fermi acceleration of relativistic particles at standing shock waves in the accretion disk. Previous work has demonstrated that the shock-acceleration process can be efficient enough to power the observed, strong outflows in radio-loud active galaxies such as M87. However, the dynamical effect (back-reaction) on the flow, due to the pressure of the relativistic particles, has not been previously considered, as this effect can have a significant influence on the disk structure. We reexamine the problem by creating a new two-fluid model that includes the dynamical effect of the relativistic particle pressure, as well as the background (thermal) gas pressure. The new model is analogous to the incorporation of the cosmic-ray pressure in the two-fluid model of cosmic-ray-modified supernova shock waves. We derive a new set of shock jump conditions and obtain dynamical solutions that describe the structure of the disk, the discontinuous shock, and the outflow. From this, we show that smooth (shock-free) global flows are impossible when relativistic particle diffusion is included in the dynamical model.
A Two-Phase Solid/Fluid Model for Dense Granular Flows Including Dilatancy Effects
NASA Astrophysics Data System (ADS)
Mangeney, Anne; Bouchut, Francois; Fernandez-Nieto, Enrique; Narbona-Reina, Gladys
2015-04-01
We propose a thin layer depth-averaged two-phase model to describe solid-fluid mixtures such as debris flows. It describes the velocity of the two phases, the compression/dilatation of the granular media and its interaction with the pore fluid pressure, that itself modifies the friction within the granular phase (Iverson et al., 2010). The model is derived from a 3D two-phase model proposed by Jackson (2000) based on the 4 equations of mass and momentum conservation within the two phases. This system has 5 unknowns: the solid and fluid velocities, the solid and fluid pressures and the solid volume fraction. As a result, an additional equation inside the mixture is necessary to close the system. Surprisingly, this issue is inadequately accounted for in the models that have been developed on the basis of Jackson's work (Bouchut et al., 2014). In particular, Pitman and Le replaced this closure simply by imposing an extra boundary condition at the surface of the flow. When making a shallow expansion, this condition can be considered as a closure condition. However, the corresponding model cannot account for a dissipative energy balance. We propose here an approach to correctly deal with the thermodynamics of Jackson's equations. We close the mixture equations by a weak compressibility relation involving a critical density, or equivalently a critical pressure. Moreover, we relax one boundary condition, making it possible for the fluid to escape the granular media when compression of the granular mass occurs. Furthermore, we introduce second order terms in the equations making it possible to describe the evolution of the pore fluid pressure in response to the compression/dilatation of the granular mass without prescribing an extra ad-hoc equation for the pore pressure. We prove that the energy balance associated with this Jackson closure is dissipative, as well as its thin layer associated model. We present several numerical tests for the 1D case that are compared to the
A Two-Phase Solid/Fluid Model for Dense Granular Flows Including Dilatancy Effects
NASA Astrophysics Data System (ADS)
Mangeney, A.; Bouchut, F.; Fernández-Nieto, E. D.; Narbona-Reina, G.; Kone, E. H.
2014-12-01
We propose a thin layer depth-averaged two-phase model to describe solid-fluid mixtures such as debris flows. It describes the velocity of the two phases, the compression/dilatation of the granular media and its interaction with the pore fluid pressure, that itself modifies the friction within the granular phase (Iverson et al., 2010). The model is derived from a 3D two-phase model proposed by Jackson (2000) based on the 4 equations of mass and momentum conservation within the two phases. This system has 5 unknowns: the solid and fluid velocities, the solid and fluid pressures and the solid volume fraction. As a result, an additional equation inside the mixture is necessary to close the system. Surprisingly, this issue is inadequately accounted for in the models that have been developed on the basis of Jackson's work (Bouchut et al., 2014). In particular, Pitman and Le replaced this closure simply by imposing an extra boundary condition at the surface of the flow. When making a shallow expansion, this condition can be considered as a closure condition. However, the corresponding model cannot account for a dissipative energy balance. We propose here an approach to correctly deal with the thermodynamics of Jackson's equations. We close the mixture equations by a weak compressibility relation involving a critical density, or equivalently a critical pressure. Moreover, we relax one boundary condition, making it possible for the fluid to escape the granular media when compression of the granular mass occurs. Furthermore, we introduce second order terms in the equations making it possible to describe the evolution of the pore fluid pressure in response to the compression/dilatation of the granular mass without prescribing an extra ad-hoc equation for the pore pressure. We prove that the energy balance associated with this Jackson closure is dissipative, as well as its thin layer associated model. We present several numerical tests for the 1D case that are compared to the
Optimization of a Two-Fluid Hydrodynamic Model of Churn-Turbulent Flow
Donna Post Guillen
2009-07-01
A hydrodynamic model of two-phase, churn-turbulent flows is being developed using the computational multiphase fluid dynamics (CMFD) code, NPHASE-CMFD. The numerical solutions obtained by this model are compared with experimental data obtained at the TOPFLOW facility of the Institute of Safety Research at the Forschungszentrum Dresden-Rossendorf. The TOPFLOW data is a high quality experimental database of upward, co-current air-water flows in a vertical pipe suitable for validation of computational fluid dynamics (CFD) codes. A five-field CMFD model was developed for the continuous liquid phase and four bubble size groups using mechanistic closure models for the ensemble-averaged Navier-Stokes equations. Mechanistic models for the drag and non-drag interfacial forces are implemented to include the governing physics to describe the hydrodynamic forces controlling the gas distribution. The closure models provide the functional form of the interfacial forces, with user defined coefficients to adjust the force magnitude. An optimization strategy was devised for these coefficients using commercial design optimization software. This paper demonstrates an approach to optimizing CMFD model parameters using a design optimization approach. Computed radial void fraction profiles predicted by the NPHASE-CMFD code are compared to experimental data for four bubble size groups.
Sanford, Ward E.; Pearson, S.C.P.; Kiyosugi, K.; Lehto, H.L.; Saballos, J.A.; Connor, C.B.
2012-01-01
We investigate geologic controls on circulation in the shallow hydrothermal system of Masaya volcano, Nicaragua, and their relationship to surface diffuse degassing. On a local scale (~250 m), relatively impermeable normal faults dipping at ~60° control the flowpath of water vapor and other gases in the vadose zone. These shallow normal faults are identified by modeling of a NE-SW trending magnetic anomaly of up to 2300 nT that corresponds to a topographic offset. Elevated SP and CO2 to the NW of the faults and an absence of CO2 to the SE suggest that these faults are barriers to flow. TOUGH2 numerical models of fluid circulation show enhanced flow through the footwalls of the faults, and corresponding increased mass flow and temperature at the surface (diffuse degassing zones). On a larger scale, TOUGH2 modeling suggests that groundwater convection may be occurring in a 3-4 km radial fracture zone transecting the entire flank of the volcano. Hot water rising uniformly into the base of the model at 1 x 10-5 kg/m2s results in convection that focuses heat and fluid and can explain the three distinct diffuse degassing zones distributed along the fracture. Our data and models suggest that the unusually active surface degassing zones at Masaya volcano can result purely from uniform heat and fluid flux at depth that is complicated by groundwater convection and permeability variations in the upper few km. Therefore isolating the effects of subsurface geology is vital when trying to interpret diffuse degassing in light of volcanic activity.
Multidimensional Model of Fluid Flow and Heat Transfer in Generation-IV Supercritical Water Reactors
Gallaway, Tara; Antal, Steven P.; Podowski, Michael Z.
2006-07-01
This paper is concerned with the mechanistic modeling and theoretical/computational analysis of flow and heat transfer in future Generation-IV Supercritical Water Cooled Reactors (SCWR). The issues discussed in the paper include: the development of analytical models of the properties of supercritical water, and the application of full three-dimensional computational modeling framework to simulate fluid flow and heat transfer in SCWRs. Several results of calculations are shown, including the evaluation of water properties (density, specific heat, thermal conductivity, viscosity, and Prandtl number) near the pseudo-critical temperature for various supercritical pressures, and the CFD predictions using the NPHASE computer code. It is demonstrated that the proposed approach is very promising for future mechanistic analyses of SCWR thermal-hydraulics and safety. (authors)
Computational Modeling of Fluid Flow and Intra-Ocular Pressure following Glaucoma Surgery
Gardiner, Bruce S.; Smith, David W.; Coote, Michael; Crowston, Jonathan G.
2010-01-01
Background Glaucoma surgery is the most effective means for lowering intraocular pressure by providing a new route for fluid to exit the eye. This new pathway is through the sclera of the eye into sub-conjunctival tissue, where a fluid filled bleb typically forms under the conjunctiva. The long-term success of the procedure relies on the capacity of the sub-conjunctival tissue to absorb the excess fluid presented to it, without generating excessive scar tissue during tissue remodeling that will shut-down fluid flow. The role of inflammatory factors that promote scarring are well researched yet little is known regarding the impact of physical forces on the healing response. Methodology To help elucidate the interplay of physical factors controlling the distribution and absorption of aqueous humor in sub-conjunctival tissue, and tissue remodeling, we have developed a computational model of fluid production in the eye and removal via the trabecular/uveoscleral pathways and the surgical pathway. This surgical pathway is then linked to a porous media computational model of a fluid bleb positioned within the sub-conjunctival tissue. The computational analysis is centered on typical functioning bleb geometry found in a human eye following glaucoma surgery. A parametric study is conducted of changes in fluid absorption by the sub-conjunctival blood vessels, changes in hydraulic conductivity due to scarring, and changes in bleb size and shape, and eye outflow facility. Conclusions This study is motivated by the fact that some blebs are known to have ‘successful’ characteristics that are generally described by clinicians as being low, diffuse and large without the formation of a distinct sub-conjunctival encapsulation. The model predictions are shown to accord with clinical observations in a number of key ways, specifically the variation of intra-ocular pressure with bleb size and shape and the correspondence between sites of predicted maximum interstitial fluid pressure
Zebrafish models of idiopathic scoliosis link cerebrospinal fluid flow defects to spine curvature.
Grimes, D T; Boswell, C W; Morante, N F C; Henkelman, R M; Burdine, R D; Ciruna, B
2016-06-10
Idiopathic scoliosis (IS) affects 3% of children worldwide, yet the mechanisms underlying this spinal deformity remain unknown. Here we show that ptk7 mutant zebrafish, a faithful developmental model of IS, exhibit defects in ependymal cell cilia development and cerebrospinal fluid (CSF) flow. Transgenic reintroduction of Ptk7 in motile ciliated lineages prevents scoliosis in ptk7 mutants, and mutation of multiple independent cilia motility genes yields IS phenotypes. We define a finite developmental window for motile cilia in zebrafish spine morphogenesis. Notably, restoration of cilia motility after the onset of scoliosis blocks spinal curve progression. Together, our results indicate a critical role for cilia-driven CSF flow in spine development, implicate irregularities in CSF flow as an underlying biological cause of IS, and suggest that noninvasive therapeutic intervention may prevent severe scoliosis.
Zebrafish models of idiopathic scoliosis link cerebrospinal fluid flow defects to spine curvature.
Grimes, D T; Boswell, C W; Morante, N F C; Henkelman, R M; Burdine, R D; Ciruna, B
2016-06-10
Idiopathic scoliosis (IS) affects 3% of children worldwide, yet the mechanisms underlying this spinal deformity remain unknown. Here we show that ptk7 mutant zebrafish, a faithful developmental model of IS, exhibit defects in ependymal cell cilia development and cerebrospinal fluid (CSF) flow. Transgenic reintroduction of Ptk7 in motile ciliated lineages prevents scoliosis in ptk7 mutants, and mutation of multiple independent cilia motility genes yields IS phenotypes. We define a finite developmental window for motile cilia in zebrafish spine morphogenesis. Notably, restoration of cilia motility after the onset of scoliosis blocks spinal curve progression. Together, our results indicate a critical role for cilia-driven CSF flow in spine development, implicate irregularities in CSF flow as an underlying biological cause of IS, and suggest that noninvasive therapeutic intervention may prevent severe scoliosis. PMID:27284198
Paul Meakin; Alexandre Tartakovsky
2009-07-01
In the subsurface fluids play a critical role by transporting dissolved minerals, colloids and contaminants (sometimes over long distances), by mediating dissolution and precipitation processes and enabling chemical transformations in solution and at mineral surfaces. Although the complex geometries of fracture apertures, fracture networks and pore spaces may make it difficult to accurately predict fluid flow in saturated (single-phase) subsurface systems, well developed methods are available. The simulation of multiphase fluid flow in the subsurface is much more challenging because of the large density and/or viscosity ratios found in important applications (water/air in the vadose zone, water/oil, water/gas, gas/oil and water/oil/gas in oil reservoirs, water/air/non-aqueous phase liquids (NAPL) in contaminated vadose zone systems and gas/molten rock in volcanic systems, for example). In addition, the complex behavior of fluid-fluid-solid contact lines, and its impact on dynamic contact angles, must also be taken into account, and coupled with the fluid flow. Pore network models and simple statistical physics based models such as the invasion percolation and diffusion-limited aggregation models have been used quite extensively. However, these models for multiphase fluid flow are based on simplified models for pore space geometries and simplified physics. Other methods such a lattice Boltzmann and lattice gas models, molecular dynamics, Monte Carlo methods, and particle methods such as dissipative particle dynamics and smoothed particle hydrodynamics are based more firmly on first principles, and they do not require simplified pore and/or fracture geometries. However, they are less (in some cases very much less) computationally efficient that pore network and statistical physics models. Recently a combination of continuum computation fluid dynamics, fluid-fluid interface tracking or capturing and simple models for the dependence of contact angles on fluid velocity
Meakin, Paul; Tartakovsky, Alexandre M.
2009-07-14
In the subsurface fluids play a critical role by transporting dissolved minerals, colloids and contaminants (sometimes over long distances), by mediating dissolution and precipitation processes and enabling chemical transformations in solution and at mineral surfaces. Although the complex geometries of fracture apertures, fracture networks and pore spaces may make it difficult to accurately predict fluid flow in saturated (single-phase) subsurface systems, well developed methods are available. The simulation of multiphase fluid flow in the subsurface is much more challenging because of the large density and/or viscosity ratios found in important applications (water/air in the vadose zone, water/oil, water/gas, gas/oil and water/oil/gas in oil reservoirs, water/air/non-aqueous phase liquids (NAPL) in contaminated vadose zone systems and gas/molten rock in volcanic systems, for example). In addition, the complex behavior of fluid-fluid-solid contact lines, and its impact on dynamic contact angles, must also be taken into account, and coupled with the fluid flow. Pore network models and simple statistical physics based models such as the invasion percolation and diffusion-limited aggregation models have been used quite extensively. However, these models for multiphase fluid flow are based on simplified models for pore space geometries and simplified physics. Other methods such a lattice Boltzmann and lattice gas models, molecular dynamics, Monte Carlo methods, and particle methods such as dissipative particle dynamics and smoothed particle hydrodynamics are based more firmly on first principles, and they do not require simplified pore and/or fracture geometries. However, they are less (in some cases very much less) computationally efficient that pore network and statistical physics models. Recently a combination of continuum computation fluid dynamics, fluid-fluid interface tracking or capturing and simple models for the dependence of contact angles on fluid velocity
Jones, Cameron C; Capasso, Patrizio; McDonough, James M; Wang, Dongfang; Rosenstein, Kyle S; Zwischenberger, Joseph B
2013-01-01
This article presents an investigation into the validation of velocity fields obtained from computational fluid dynamic (CFD) models of flow through the membrane oxygenators using x-ray digital subtraction angiography (DSA). Computational fluid dynamic is a useful tool in characterizing artificial lung devices, but numerical results must be experimentally validated. We used DSA to visualize flow through a membrane oxygenator at 2 L/min using 37% glycerin at 22°C. A Siemens Artis Zee system acquired biplane x-ray images at 7.5 frames per second, after infusion of an iodinated contrast agent at a rate of 33 ml/s. A maximum cross-correlation (MCC) method was used to track the contrast perfusion through the fiber bundle. For the CFD simulations, the fiber bundle was treated as a single momentum sink according to the Ergun equation. Blood was modeled as a Newtonian fluid, with constant viscosity (3.3 cP) and density (1050 kg/m3). Although CFD results and experimental pressure measurements were in general agreement, the simulated 2 L/min perfusion did not reproduce the flow behavior seen in vitro. Simulated velocities in the fiber bundle were on average 42% lower than experimental values. These results indicate that it is insufficient to use only pressure measurements for validation of the flow field because pressure-validated CFD results can still significantly miscalculate the physical velocity field. We have shown that a clinical x-ray modality, together with a MCC tracking algorithm, can provide a nondestructive technique for acquiring experimental data useful for validation of the velocity field inside membrane oxygenators.
A viscoelastic fluid-structure interaction model for carotid arteries under pulsatile flow.
Wang, Zhongjie; Wood, Nigel B; Xu, Xiao Yun
2015-05-01
In this study, a fluid-structure interaction model (FSI) incorporating viscoelastic wall behaviour is developed and applied to an idealized model of the carotid artery under pulsatile flow. The shear and bulk moduli of the arterial wall are described by Prony series, where the parameters can be derived from in vivo measurements. The aim is to develop a fully coupled FSI model that can be applied to realistic arterial geometries with normal or pathological viscoelastic wall behaviour. Comparisons between the numerical and analytical solutions for wall displacements demonstrate that the coupled model is capable of predicting the viscoelastic behaviour of carotid arteries. Comparisons are also made between the solid only and FSI viscoelastic models, and the results suggest that the difference in radial displacement between the two models is negligible.
NASA Astrophysics Data System (ADS)
Chen, Guang-Hao; Wang, Guo-Yu; Huang, Biao; Hu, Chang-Li; Wang, Zhi-Ying; Wang, Jian
2015-02-01
In this paper, a compressible fluid model is proposed to investigate dynamics of the turbulent cavitating flow over a Clark-Y hydrofoil. The numerical simulation is based on the homogeneous mixture approach coupled with filter-based density correction model (FBDCM) turbulence model and Zwart cavitation model. Considering the compressibility effect, the equation of state of each phase is introduced into the numerical model. The results show that the predicted results agree well with experimental data concerning the time-averaged lift/drag coefficient and shedding frequency. The quasi-periodic evolution of sheet/cloud cavitation and the resulting lift and drag are discussed in detail. Especially, the present compressible-mixture numerical model is capable of simulating the shock waves in the final stage of cavity collapse. It is found that the shock waves may cause the transient significant increase and decrease in lift and drag if the cavity collapses near the foil surface.
Computational Fluid Dynamics Modeling of a Lithium/Thionyl Chloride Battery with Electrolyte Flow
Gu, W.B.; Jungst, Rudolph G.; Nagasubramanian, Ganesan; Wang, C.Y.; Weidner, John.
1999-06-11
A two-dimensional model is developed to simulate discharge of a lithium/thionyl chloride primary battery. The model accounts for not only transport of species and charge, but also the electrode porosity variations and the electrolyte flow induced by the volume reduction caused by electrochemical reactions. Numerical simulations are performed using a finite volume method of computational fluid dynamics. The predicted discharge curves for various temperatures are compared to the experimental data with excellent agreement. Moreover, the simulation results. in conjunction with computer visualization and animation techniques, confirm that cell utilization in the temperature and current range of interest is limited by pore plugging or clogging of the front side of the cathode as a result of LiCl precipitation. The detailed two-dimensional flow simulation also shows that the electrolyte is replenished from the cell header predominantly through the separator into the front of the cathode during most parts of the discharge, especially for higher cell temperatures.
General Fluid System Simulation Program to Model Secondary Flows in Turbomachinery
NASA Technical Reports Server (NTRS)
Majumdar, Alok K.; Van Hoosier, Katherine P.
1995-01-01
The complexity and variety of turbomachinery flow circuits created a need for a general fluid system simulation program for test data anomaly resolution as well as design review. The objective of the paper is to present a computer program that has been developed to support Marshall Space Flight Center's turbomachinery internal flow analysis efforts. The computer program solves for the mass. energy and species conservation equation at each node and flow rate equation at each branch of the network by a novel numerical procedure which is a combination of both Newton-Ralphson and successive substitution method and uses a thermodynamic property program for computing real gas properties. A generalized, robust, modular, and 'user-friendly' computer program has been developed to model internal flow rates, pressures, temperatures, concentrations of gas mixtures and axial thrusts. The program can be used for any network for compressible and incompressible flows, choked flow, change of phase and gaseous mixturecs. The code has been validated by comparing the predictions with Space Shuttle Main Engine test data.
NASA Astrophysics Data System (ADS)
Akbar, Noreen Sher; Nadeem, S.; Lee, Changhoon
In the present article we have analyzed the Jeffrey fluid model for the peristaltic flow of chyme in the small intestine. We have formulated the problem using two non-periodic sinusoidal waves of different wavelengths propagating with same speed c along the outer wall of the tube. Governing equations for the problem under consideration have been simplified under the assumptions of long wavelength and low Reynolds number approximation (such assumptions are consistent since Re (Reynolds number) is very small and long wavelength approximation also exists in the small intestine). Exact solutions have been calculated for velocity and pressure rise. Physical behavior of different parameters of Jeffrey fluid has been presented graphically for velocity, pressure rise, pressure gradient and frictional forces. The trapping phenomenon is also discussed at the end of the article.
Multi-fluid modelling of pulsed discharges for flow control applications
NASA Astrophysics Data System (ADS)
Poggie, J.
2015-02-01
Experimental evidence suggests that short-pulse dielectric barrier discharge actuators are effective for speeds corresponding to take-off and approach of large aircraft, and thus are a fruitful direction for flow control technology development. Large-eddy simulations have reproduced some of the main fluid dynamic effects. The plasma models used in such simulations are semi-empirical, however, and need to be tuned for each flowfield under consideration. In this paper, the discharge physics is examined in more detail with multi-fluid modelling, comparing a five-moment model (continuity, momentum, and energy equations) to a two-moment model (continuity and energy equations). A steady-state, one-dimensional discharge was considered first, and the five-moment model was found to predict significantly lower ionisation rates and number densities than the two-moment model. A two-dimensional, transient discharge problem with an elliptical cathode was studied next. Relative to the two-moment model, the five-moment model predicted a slower response to the activation of the cathode, and lower electron velocities and temperatures as the simulation approached steady-state. The primary reason for the differences in the predictions of the two models can be attributed to the effects of particle inertia, particularly electron inertia in the cathode layer. The computational cost of the five-moment model is only about twice that of the simpler variant, suggesting that it may be feasible to use the more sophisticated model in practical calculations for flow control actuator design.
Incompressible SPH Model for Simulating Violent Free-Surface Fluid Flows
NASA Astrophysics Data System (ADS)
Staroszczyk, Ryszard
2014-06-01
In this paper the problem of transient gravitational wave propagation in a viscous incompressible fluid is considered, with a focus on flows with fast-moving free surfaces. The governing equations of the problem are solved by the smoothed particle hydrodynamics method (SPH). In order to impose the incompressibility constraint on the fluid motion, the so-called projection method is applied in which the discrete SPH equations are integrated in time by using a fractional-step technique. Numerical performance of the proposed model has been assessed by comparing its results with experimental data and with results obtained by a standard (weakly compressible) version of the SPH approach. For this purpose, a plane dam-break flow problem is simulated, in order to investigate the formation and propagation of a wave generated by a sudden collapse of a water column initially contained in a rectangular tank, as well as the impact of such a wave on a rigid vertical wall. The results of simulations show the evolution of the free surface of water, the variation of velocity and pressure fields in the fluid, and the time history of pressures exerted by an impacting wave on a wall.
Analysis Of Residence Time Distribution Of Fluid Flow By Axial Dispersion Model
NASA Astrophysics Data System (ADS)
Sugiharto, Su'ud, Zaki; Kurniadi, Rizal; Waris, Abdul; Abidin, Zainal
2010-12-01
Radioactive tracer 82Br in the form of KBr-82 with activity ± 1 mCi has been injected into steel pipeline to qualify the extent dispersion of water flowing inside it. Internal diameter of the pipe is 3 in. The water source was originated from water tank through which the water flow gravitically into the pipeline. Two collimated sodium iodide detectors were used in this experiment each of which was placed on the top of the pipeline at the distance of 8 and 11 m from injection point respectively. Residence time distribution (RTD) curves obtained from injection of tracer are elaborated numerically to find information of the fluid flow properties. The transit time of tracer calculated from the mean residence time (MRT) of each RTD curves is 14.9 s, therefore the flow velocity of the water is 0.2 m/s. The dispersion number, D/uL, for each RTD curve estimated by using axial dispersion model are 0.055 and 0.06 respectively. These calculations are performed after fitting the simulated axial dispersion model on the experiment curves. These results indicated that the extent of dispersion of water flowing in the pipeline is in the category of intermediate.
Analysis Of Residence Time Distribution Of Fluid Flow By Axial Dispersion Model
Sugiharto; Su'ud, Zaki; Kurniadi, Rizal; Waris, Abdul; Abidin, Zainal
2010-12-23
Radioactive tracer {sup 82}Br in the form of KBr-82 with activity {+-} 1 mCi has been injected into steel pipeline to qualify the extent dispersion of water flowing inside it. Internal diameter of the pipe is 3 in. The water source was originated from water tank through which the water flow gravitically into the pipeline. Two collimated sodium iodide detectors were used in this experiment each of which was placed on the top of the pipeline at the distance of 8 and 11 m from injection point respectively. Residence time distribution (RTD) curves obtained from injection of tracer are elaborated numerically to find information of the fluid flow properties. The transit time of tracer calculated from the mean residence time (MRT) of each RTD curves is 14.9 s, therefore the flow velocity of the water is 0.2 m/s. The dispersion number, D/uL, for each RTD curve estimated by using axial dispersion model are 0.055 and 0.06 respectively. These calculations are performed after fitting the simulated axial dispersion model on the experiment curves. These results indicated that the extent of dispersion of water flowing in the pipeline is in the category of intermediate.
Massively Parallel Linear Stability Analysis with P_ARPACK for 3D Fluid Flow Modeled with MPSalsa
Lehoucq, R.B.; Salinger, A.G.
1998-10-13
We are interested in the stability of three-dimensional fluid flows to small dkturbances. One computational approach is to solve a sequence of large sparse generalized eigenvalue problems for the leading modes that arise from discretizating the differential equations modeling the flow. The modes of interest are the eigenvalues of largest real part and their associated eigenvectors. We discuss our work to develop an effi- cient and reliable eigensolver for use by the massively parallel simulation code MPSalsa. MPSalsa allows simulation of complex 3D fluid flow, heat transfer, and mass transfer with detailed bulk fluid and surface chemical reaction kinetics.
Multicomponent model of deformation and detachment of a biofilm under fluid flow
Tierra, Giordano; Pavissich, Juan P.; Nerenberg, Robert; Xu, Zhiliang; Alber, Mark S.
2015-01-01
A novel biofilm model is described which systemically couples bacteria, extracellular polymeric substances (EPS) and solvent phases in biofilm. This enables the study of contributions of rheology of individual phases to deformation of biofilm in response to fluid flow as well as interactions between different phases. The model, which is based on first and second laws of thermodynamics, is derived using an energetic variational approach and phase-field method. Phase-field coupling is used to model structural changes of a biofilm. A newly developed unconditionally energy-stable numerical splitting scheme is implemented for computing the numerical solution of the model efficiently. Model simulations predict biofilm cohesive failure for the flow velocity between and m s−1 which is consistent with experiments. Simulations predict biofilm deformation resulting in the formation of streamers for EPS exhibiting a viscous-dominated mechanical response and the viscosity of EPS being less than . Higher EPS viscosity provides biofilm with greater resistance to deformation and to removal by the flow. Moreover, simulations show that higher EPS elasticity yields the formation of streamers with complex geometries that are more prone to detachment. These model predictions are shown to be in qualitative agreement with experimental observations. PMID:25808342
Multicomponent model of deformation and detachment of a biofilm under fluid flow.
Tierra, Giordano; Pavissich, Juan P; Nerenberg, Robert; Xu, Zhiliang; Alber, Mark S
2015-05-01
A novel biofilm model is described which systemically couples bacteria, extracellular polymeric substances (EPS) and solvent phases in biofilm. This enables the study of contributions of rheology of individual phases to deformation of biofilm in response to fluid flow as well as interactions between different phases. The model, which is based on first and second laws of thermodynamics, is derived using an energetic variational approach and phase-field method. Phase-field coupling is used to model structural changes of a biofilm. A newly developed unconditionally energy-stable numerical splitting scheme is implemented for computing the numerical solution of the model efficiently. Model simulations predict biofilm cohesive failure for the flow velocity between [Formula: see text] and [Formula: see text] m s(-1) which is consistent with experiments. Simulations predict biofilm deformation resulting in the formation of streamers for EPS exhibiting a viscous-dominated mechanical response and the viscosity of EPS being less than [Formula: see text]. Higher EPS viscosity provides biofilm with greater resistance to deformation and to removal by the flow. Moreover, simulations show that higher EPS elasticity yields the formation of streamers with complex geometries that are more prone to detachment. These model predictions are shown to be in qualitative agreement with experimental observations.
Multicomponent model of deformation and detachment of a biofilm under fluid flow.
Tierra, Giordano; Pavissich, Juan P; Nerenberg, Robert; Xu, Zhiliang; Alber, Mark S
2015-05-01
A novel biofilm model is described which systemically couples bacteria, extracellular polymeric substances (EPS) and solvent phases in biofilm. This enables the study of contributions of rheology of individual phases to deformation of biofilm in response to fluid flow as well as interactions between different phases. The model, which is based on first and second laws of thermodynamics, is derived using an energetic variational approach and phase-field method. Phase-field coupling is used to model structural changes of a biofilm. A newly developed unconditionally energy-stable numerical splitting scheme is implemented for computing the numerical solution of the model efficiently. Model simulations predict biofilm cohesive failure for the flow velocity between [Formula: see text] and [Formula: see text] m s(-1) which is consistent with experiments. Simulations predict biofilm deformation resulting in the formation of streamers for EPS exhibiting a viscous-dominated mechanical response and the viscosity of EPS being less than [Formula: see text]. Higher EPS viscosity provides biofilm with greater resistance to deformation and to removal by the flow. Moreover, simulations show that higher EPS elasticity yields the formation of streamers with complex geometries that are more prone to detachment. These model predictions are shown to be in qualitative agreement with experimental observations. PMID:25808342
A fiber matrix model for fluid flow and streaming potentials in the canaliculi of an osteon
NASA Technical Reports Server (NTRS)
Zeng, Y.; Cowin, S. C.; Weinbaum, S.
1994-01-01
A theoretical model is developed to predict the fluid shear stress and streaming potential at the surface of osteocytic processes in the lacunar-canalicular porosity of an osteon when the osteon is subject to mechanical loads that are parallel or perpendicular to its axis. The theory developed in Weinbaum et al. (31) for the flow through a proteoglycan matrix in a canaliculus is employed in a poroelastic model for the osteon. Our formulation is a generalization of that of Petrov et al. (17). Our model predicts that, in order to satisfy the measured frequency dependence of the phase and magnitude of the SGP in macroscopic bone samples, the fiber spacing in the fluid annulus must lie in the narrow range 6-7 nm typical of the spacing of GAG sidechains along a protein monomer. The model predictions for the local SGP profiles in the osteon agree with the experimental observations of Starkebaum et al. (24). The theory predicts that the pore pressure relaxation time, tau d, for a 150-300 microns diameter osteon with the foregoing matrix structure is approximately 0.03-0.13 sec, and that the amplitude of the mean fluid shear stress on the membrane of the osteocytic process at the mean areal radius of the osteon has a maximum at 28 Hz if tau d = 0.06 sec. This maximum, which is independent of the magnitude of the loading, could be important in vivo since the recent experiments of Turner et al. (28) and McLeod et al. (15) have a peak in the strain frequency spectrum between 20 and 30 Hz that also appears to be independent of the type (magnitude) of loading. Numerical predictions for the amplitude of the average fluid shear stress on the osteocytic membrane at the mean areal radius of the osteon show that the fluid shear stress associated with the low amplitude 20-30 Hz spectral strain component is at least as large as the average fluid shear stress associated with the high amplitude 1 Hz stride component, although the latter loading is an order of magnitude larger, and has a
SDEM modelling of deformation associated with a listric fault system and associated fluid flow
NASA Astrophysics Data System (ADS)
Rasmussen, Marie L.; Clausen, Ole R.; Egholm, David L.; Andresen, Katrine J.
2016-04-01
Numerical modelling of geological structures using FEM, DEM and SDEM methods as well as analogue modelling are widely used in order to achieve a better understanding of the kinematics and dynamics during deformation. The methods are furthermore the ultimate source for mapping (observing) the true geometry of geological structures as well as subsurface fluid flow phenomena in 3D seismic data developed for hydrocarbon exploration. Here we use 3D seismic data and SDEM modelling to suggest a dynamic-kinematic evolution of the deformation in the hangingwall of a listric fault overlying an active salt roller. We use the results to obtain a better understanding of the fluid flow in a complex deformed hangingwall. The case study is focused at the D-1 fault trend in the western part of the Norwegian Danish Basin, at the northern slope of the Ringkøbing-Fyn High. The D-1 main fault detaches along the northern flank of a Zechstein salt roller which was active during the Cenozoic. The seismic analysis shows a system of secondary normal antithetic and synthetic faults dipping approximately 50-60dg within the hangingwall. Shallow gas is trapped in the hangingwall and the secondary faults often confine the accumulations i.e. indicating that the secondary faults are sealing. The modelling confirms that the geometry of the secondary faults is highly controlled by the rheology of different layers in the hangingwall but also on the intensity of the salt movement. The modelling also suggests the presence of vertical deformation zones; structures which are not directly observed on the seismic data. The vertical deformation zones are related to the differential vertical movement of the strata due to salt migration. A neural network trained chimney probability cube shows high probabilities for the presence of minor vertical gas chimneys below the gas accumulations suggesting that vertical fluid migration in the hangingwall occurred in areas with significant vertical salt movements. The
Inverse model of fully coupled fluid flow and stress in fractured rock masses
NASA Astrophysics Data System (ADS)
Wang, Y.; Rutqvist, J.
2008-12-01
In order to reflect the real behavior of the seepage field and deformation field during the environment change and construction process£¬the basic equations and FEM methods for fully coupled analysis of fluid flow and stress are developed£¬based on the assumptions of small deformation and incompressible water flow in complicated fractured rock masses. Both the equivalent continuum media model and the discrete media model are adopted. And the modified initial flow method is used to deal with the free surface of unconfined seepage. Due to the difficulty in determining the parameters of water flow field, stress field and their coupling relations, an inverse model is presented for the fully coupled problem in which both the data of water head and displacement are taken into consideration. Objective function is defined based on sensitivity analysis of parameters, and the relative values of water head, displacement on parameters are adopted in the establishment of objective function. A hybrid genetic algorithm is proposed as optimization method. The probability of crossover and mutation is determined according to chromosome fitness and a concept of self- adaptive probability is given. In addition, simplex method is also applied to increase the ability of local search, the operation of accelerated cycle is used in order to decrease optimization time.
Nanoscale Pore Imaging and Pore Scale Fluid Flow Modeling in Chalk
Tomutsa, Liviu; Silin, Dmitriy
2004-08-19
For many rocks of high economic interest such as chalk, diatomite, tight gas sands or coal, nanometer scale resolution is needed to resolve the 3D-pore structure, which controls the flow and trapping of fluids in the rocks. Such resolutions cannot be achieved with existing tomographic technologies. A new 3D imaging method, based on serial sectioning and using the Focused Ion Beam (FIB) technology has been developed. FIB allows for the milling of layers as thin as 10 nanometers by using accelerated Ga+ ions to sputter atoms from the sample surface. After each milling step, as a new surface is exposed, a 2D image of this surface is generated. Next, the 2D images are stacked to reconstruct the 3D pore or grain structure. Resolutions as high as 10 nm are achievable using such a technique. A new robust method of pore-scale fluid flow modeling has been developed and applied to sandstone and chalk samples. The method uses direct morphological analysis of the pore space to characterize the petrophysical properties of diverse formations. Not only petrophysical properties (porosity, permeability, relative permeability and capillary pressures) can be computed but also flow processes, such as those encountered in various IOR approaches, can be simulated. Petrophysical properties computed with the new method using the new FIB data will be presented. Present study is a part of the development of an Electronic Core Laboratory at LBNL/UCB.
Modeling of flow and heat transfer for fluids at supercritical conditions
NASA Astrophysics Data System (ADS)
Gallaway, Tara
2011-12-01
The Supercritical Water Reactor (SCWR) has been proposed as one of the six Generation IV reactor design concepts under consideration. The key feature of the SCWR is that water at supercritical pressures is used as the reactor coolant. At supercritical pressures, the working fluid does not undergo phase change as it is heated, but rather the fluid properties experience dramatic variations throughout what is known as the pseudo-critical region. Highly nonuniform temperature and uid property distributions are expected in the reactor core, which will have a significant impact on turbulence and heat transfer as well as stability limits for future SCWRs. The goal of this work is to understand and predict the effects of these fluid property variations on turbulence and heat transfer throughout the reactor core and to predict the potential onset of dynamic instabilities. CO2 at supercritical conditions is included in the current study due in some part to its use as a viable simulant fluid in place of water for experimental studies. The use of CO2 at supercritical conditions as a reactor coolant has also gained popularity in recent years. Spline-type property models have been developed for both water and CO2 at supercritical pressures in order to include the property variations into a numerical solver. Turbulence and heat transfer models for fluids at supercritical conditions have been developed and implemented into the NPHASE-CMFD computer code. The results of predictions using the proposed models have been compared to experimental data from the Korea Atomic Energy Research Institute (KAERI) for various heat transfer regimes. While no model is without some deficiency, the Chien Low-Reynolds k -- epsilon model performs best at predicting the experimental data. A stability model has been developed and is presented in this dissertation as well. This model utilizes three different solution methods and tests the effects of inlet temperature, mass flow rate, local loss
Computer modeling of fluid flow and combustion in the ISV (In Situ Vitrification) confinement hood
Johnson, R.W.; Paik, S.
1990-09-01
Safety and suitability objectives for the application of the In Situ Vitrification (ISV) technology at the INEL require that the physical processes involved in ISVV be modeled to determine their operational behavior. The mathematical models that have been determined to address the modeling needs adequately for the ISV analysis package are detailed elsewhere. The present report is concerned with the models required for simulating the reacting flow that occurs in the ISV confinement hood. An experimental code named COYOTE has been secured that appears adequate to model the combustion in the confinement hood. The COYOTE code is a two-dimensional, transient, compressible, Eulerian, gas dynamics code for modeling reactive flows. It recognizes nonuniform Cartesian and cylindrical geometry and is based on the ICE (Implicit Continuous-fluid Eulerian) family of solution methods. It includes models for chemical reactions based on chemical kinetics as well as equilibrium chemistry. The mathematical models contained in COYOTE, their discrete analogs, the solution procedure, code structure and some test problems are presented in the report. 12 refs., 17 figs., 6 tabs.
Kwon, Ronald Y.; Frangos, John A.
2010-01-01
Skeletal adaptation to mechanical loading has been widely hypothesized to involve the stimulation of osteocytes by interstitial fluid flow (IFF). However, direct investigation of this hypothesis has been difficult due in large part to the inability to directly measure IFF velocities within the lacunar–canalicular system. Measurements of fluorescence recovery after photobleaching (FRAP) within individual lacunae could be used to quantify lacunar–canalicular IFF when combined with mathematical modeling. In this study, we used a computational transport model to characterize the relationship between flow frequency (0.5–10 Hz), peak flow velocity (0–300 μm/s), tracer diffusion coefficient (100–300 μm2/s), and transport enhancement (i.e., (k/k0) − 1, where k and k0 are the transport rates in the presence/absence of flow) during lacunar FRAP investigations. We show that this relationship is well described by a simple power law with frequency-dependent coefficients, and is relatively insensitive to variations in lacunar geometry. Using this power law relationship, we estimated peak IFF velocities in hindlimb mice subjected to intramedullary pressurization using values of k and k0 previously obtained from ex vivo lacunar FRAP investigations. Together, our findings suggest that skeletal adaptation in hindlimb suspended mice subjected to dynamic intramedullary pressure occurred in the presence of IFF at levels associated with physiological loading. PMID:21076644
Mukhopadhyay, S.; Tsang, Y.; Finsterle, S.
2009-01-15
A simple conceptual model has been recently developed for analyzing pressure and temperature data from flowing fluid temperature logging (FFTL) in unsaturated fractured rock. Using this conceptual model, we developed an analytical solution for FFTL pressure response, and a semianalytical solution for FFTL temperature response. We also proposed a method for estimating fracture permeability from FFTL temperature data. The conceptual model was based on some simplifying assumptions, particularly that a single-phase airflow model was used. In this paper, we develop a more comprehensive numerical model of multiphase flow and heat transfer associated with FFTL. Using this numerical model, we perform a number of forward simulations to determine the parameters that have the strongest influence on the pressure and temperature response from FFTL. We then use the iTOUGH2 optimization code to estimate these most sensitive parameters through inverse modeling and to quantify the uncertainties associated with these estimated parameters. We conclude that FFTL can be utilized to determine permeability, porosity, and thermal conductivity of the fracture rock. Two other parameters, which are not properties of the fractured rock, have strong influence on FFTL response. These are pressure and temperature in the borehole that were at equilibrium with the fractured rock formation at the beginning of FFTL. We illustrate how these parameters can also be estimated from FFTL data.
Moller, Nancy; Weare J. H.
2008-05-29
Successful exploitation of the vast amount of heat stored beneath the earth’s surface in hydrothermal and fluid-limited, low permeability geothermal resources would greatly expand the Nation’s domestic energy inventory and thereby promote a more secure energy supply, a stronger economy and a cleaner environment. However, a major factor limiting the expanded development of current hydrothermal resources as well as the production of enhanced geothermal systems (EGS) is insufficient knowledge about the chemical processes controlling subsurface fluid flow. With funding from past grants from the DOE geothermal program and other agencies, we successfully developed advanced equation of state (EOS) and simulation technologies that accurately describe the chemistry of geothermal reservoirs and energy production processes via their free energies for wide XTP ranges. Using the specific interaction equations of Pitzer, we showed that our TEQUIL chemical models can correctly simulate behavior (e.g., mineral scaling and saturation ratios, gas break out, brine mixing effects, down hole temperatures and fluid chemical composition, spent brine incompatibilities) within the compositional range (Na-K-Ca-Cl-SO4-CO3-H2O-SiO2-CO2(g)) and temperature range (T < 350°C) associated with many current geothermal energy production sites that produce brines with temperatures below the critical point of water. The goal of research carried out under DOE grant DE-FG36-04GO14300 (10/1/2004-12/31/2007) was to expand the compositional range of our Pitzer-based TEQUIL fluid/rock interaction models to include the important aluminum and silica interactions (T < 350°C). Aluminum is the third most abundant element in the earth’s crust; and, as a constituent of aluminosilicate minerals, it is found in two thirds of the minerals in the earth’s crust. The ability to accurately characterize effects of temperature, fluid mixing and interactions between major rock-forming minerals and hydrothermal and
NASA Astrophysics Data System (ADS)
Li, Feng-Chen; Wang, Lu; Cai, Wei-Hua
2015-07-01
A mixed subgrid-scale (SGS) model based on coherent structures and temporal approximate deconvolution (MCT) is proposed for turbulent drag-reducing flows of viscoelastic fluids. The main idea of the MCT SGS model is to perform spatial filtering for the momentum equation and temporal filtering for the conformation tensor transport equation of turbulent flow of viscoelastic fluid, respectively. The MCT model is suitable for large eddy simulation (LES) of turbulent drag-reducing flows of viscoelastic fluids in engineering applications since the model parameters can be easily obtained. The LES of forced homogeneous isotropic turbulence (FHIT) with polymer additives and turbulent channel flow with surfactant additives based on MCT SGS model shows excellent agreements with direct numerical simulation (DNS) results. Compared with the LES results using the temporal approximate deconvolution model (TADM) for FHIT with polymer additives, this mixed SGS model MCT behaves better, regarding the enhancement of calculating parameters such as the Reynolds number. For scientific and engineering research, turbulent flows at high Reynolds numbers are expected, so the MCT model can be a more suitable model for the LES of turbulent drag-reducing flows of viscoelastic fluid with polymer or surfactant additives. Project supported by the China Postdoctoral Science Foundation (Grant No. 2011M500652), the National Natural Science Foundation of China (Grant Nos. 51276046 and 51206033), and the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20112302110020).
Interstitial fluid flow and drug delivery in vascularized tumors: a computational model.
Welter, Michael; Rieger, Heiko
2013-01-01
Interstitial fluid is a solution that bathes and surrounds the human cells and provides them with nutrients and a way of waste removal. It is generally believed that elevated tumor interstitial fluid pressure (IFP) is partly responsible for the poor penetration and distribution of therapeutic agents in solid tumors, but the complex interplay of extravasation, permeabilities, vascular heterogeneities and diffusive and convective drug transport remains poorly understood. Here we consider-with the help of a theoretical model-the tumor IFP, interstitial fluid flow (IFF) and its impact upon drug delivery within tumor depending on biophysical determinants such as vessel network morphology, permeabilities and diffusive vs. convective transport. We developed a vascular tumor growth model, including vessel co-option, regression, and angiogenesis, that we extend here by the interstitium (represented by a porous medium obeying Darcy's law) and sources (vessels) and sinks (lymphatics) for IFF. With it we compute the spatial variation of the IFP and IFF and determine its correlation with the vascular network morphology and physiological parameters like vessel wall permeability, tissue conductivity, distribution of lymphatics etc. We find that an increased vascular wall conductivity together with a reduction of lymph function leads to increased tumor IFP, but also that the latter does not necessarily imply a decreased extravasation rate: Generally the IF flow rate is positively correlated with the various conductivities in the system. The IFF field is then used to determine the drug distribution after an injection via a convection diffusion reaction equation for intra- and extracellular concentrations with parameters guided by experimental data for the drug Doxorubicin. We observe that the interplay of convective and diffusive drug transport can lead to quite unexpected effects in the presence of a heterogeneous, compartmentalized vasculature. Finally we discuss various
Desbonnets, Quentin; Broc, Daniel
2012-07-01
It is well known that a fluid may strongly influence the dynamic behaviour of a structure. Many different physical phenomena may take place, depending on the conditions: fluid flow, fluid at rest, little or high displacements of the structure. Inertial effects can take place, with lower vibration frequencies, dissipative effects also, with damping, instabilities due to the fluid flow (Fluid Induced Vibration). In this last case the structure is excited by the fluid. Tube bundles structures are very common in the nuclear industry. The reactor cores and the steam generators are both structures immersed in a fluid which may be submitted to a seismic excitation or an impact. In this case the structure moves under an external excitation, and the movement is influence by the fluid. The main point in such system is that the geometry is complex, and could lead to very huge sizes for a numerical analysis. Homogenization models have been developed based on the Euler equations for the fluid. Only inertial effects are taken into account. A next step in the modelling is to build models based on the homogenization of the Navier-Stokes equations. The papers presents results on an important step in the development of such model: the analysis of the fluid flow in a oscillating tube bundle. The analysis are made from the results of simulations based on the Navier-Stokes equations for the fluid. Comparisons are made with the case of the oscillations of a single tube, for which a lot of results are available in the literature. Different fluid flow pattern may be found, depending in the Reynolds number (related to the velocity of the bundle) and the Keulegan Carpenter number (related to the displacement of the bundle). A special attention is paid to the quantification of the inertial and dissipative effects, and to the forces exchanges between the bundle and the fluid. The results of such analysis will be used in the building of models based on the homogenization of the Navier
Modeling fluid flow in deformation bands with stabilized localization mixed finite elements
NASA Astrophysics Data System (ADS)
Sun, W.; Ostien, J. T.; Foulk, J. W.; Abdeljawad, F.
2012-12-01
Deformation bands in geological materials refer to narrow zones of inhomogeneous strain. Their onset and propagation may cause significant changes in microstructures and therefore profoundly enhance or suppress fluid flow and induce anisotropy. These changes in hydraulic properties have strong implications in geotechnical engineering, carbon dioxide sequestration and nuclear waste storage. The difficulty in modeling such multiphysics phenomena is threefold. 1. Monolithically coupled promechanics formulation may lead to non-physical oscillation in pore pressure near the undrained limit if identical mesh and basis functions are used for pore pressure and displacement. 2. Onsets of deformation bands may lead to non-converging mesh-dependent results if no length scale is introduced to the finite element formulation. 3. Modeling anisotropy induced by the deformation band may require a very fine mesh to capture the sharp pore pressure gradient and results in a computational intensive system. In this study, we introduce a projection-based technique to stabilize a large deformation finite element model that eliminates the non-physical oscillation in pore pressure. Using a 1D analytical solution as guideline, we introduce a simple scheme that can adaptively update the optimal value for the stabilization parameter that can restore stability without over-diffusing the system. This stabilized model is coupled with a localization element technique used to introduce proper length scale to regularize the governing equations and resolve the fluid flow jumps across the deformation bands. Numerical examples are presented to demonstrate the properties and performance of the proposed localized models. *Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000
North Cascadia heat flux and fluid flow from gas hydrates: Modeling 3-D topographic effects
NASA Astrophysics Data System (ADS)
Li, Hong-lin; He, Tao; Spence, George D.
2014-01-01
The bottom-simulating reflector (BSR) of gas hydrate is well imaged from two perpendicular seismic grids in the region of a large carbonate mound, informally called Cucumber Ridge off Vancouver Island. We use a new method to calculate 3-D heat flow map from the BSR depths, in which we incorporate 3-D topographic corrections after calibrated by the drilling results from nearby (Integrated) Ocean Drilling Program Site 889 and Site U1327. We then estimate the associated fluid flow by relating it to the topographically corrected heat flux anomalies. In the midslope region, a heat flux anomaly of 1 mW/m2 can be associated with an approximate focused fluid flow rate of 0.09 mm/yr. Around Cucumber Ridge, high rates of focused fluid flow were observed at steep slopes with values more than double the average regional diffusive fluid discharge rate of 0.56 mm/yr. As well, in some areas of relatively flat seafloor, the focused fluid flow rates still exceeded 0.5 mm/yr. On the seismic lines the regions of focused fluid flow were commonly associated with seismic blanking zones above the BSR and sometimes with strong reflectors below the BSR, indicating that the faults/fractures provide high-permeability pathways for fluids to carry methane from BSR depths to the seafloor. These high fluid flow regions cover mostly the western portion of our area with gas hydrate concentration estimations of ~6% based on empirical correlations from Hydrate Ridge in south off Oregon, significantly higher than previously recognized values of ~2.5% in the eastern portion determined from Site U1327.
NASA Technical Reports Server (NTRS)
Sheere, R. W.
1970-01-01
Fluid-flow restrictor has degree of restriction easily and accurately controlled during manufacture. Restrictor's flow channel is machined square thread around a solid slug which is shrink-fitted to cylindrical case. One end of case is closed, open end capped, and both ends tapped for tube fittings for fluid flow.
Interstitial Fluid Flow and Drug Delivery in Vascularized Tumors: A Computational Model
Welter, Michael; Rieger, Heiko
2013-01-01
Interstitial fluid is a solution that bathes and surrounds the human cells and provides them with nutrients and a way of waste removal. It is generally believed that elevated tumor interstitial fluid pressure (IFP) is partly responsible for the poor penetration and distribution of therapeutic agents in solid tumors, but the complex interplay of extravasation, permeabilities, vascular heterogeneities and diffusive and convective drug transport remains poorly understood. Here we consider–with the help of a theoretical model–the tumor IFP, interstitial fluid flow (IFF) and its impact upon drug delivery within tumor depending on biophysical determinants such as vessel network morphology, permeabilities and diffusive vs. convective transport. We developed a vascular tumor growth model, including vessel co-option, regression, and angiogenesis, that we extend here by the interstitium (represented by a porous medium obeying Darcy's law) and sources (vessels) and sinks (lymphatics) for IFF. With it we compute the spatial variation of the IFP and IFF and determine its correlation with the vascular network morphology and physiological parameters like vessel wall permeability, tissue conductivity, distribution of lymphatics etc. We find that an increased vascular wall conductivity together with a reduction of lymph function leads to increased tumor IFP, but also that the latter does not necessarily imply a decreased extravasation rate: Generally the IF flow rate is positively correlated with the various conductivities in the system. The IFF field is then used to determine the drug distribution after an injection via a convection diffusion reaction equation for intra- and extracellular concentrations with parameters guided by experimental data for the drug Doxorubicin. We observe that the interplay of convective and diffusive drug transport can lead to quite unexpected effects in the presence of a heterogeneous, compartmentalized vasculature. Finally we discuss various
NASA Astrophysics Data System (ADS)
Adachi, H.
1986-08-01
In the Part I, the author describes the fundamental form of the hydraulic basic equations for a one-dimensional two-phase flow (two fluid model). Most of the discussions are concentrated on the treatment of phase change inertial force terms in the equations of motion, and the author's equations of motion have a strong uniqueness on the following three points in comparison with conventional equations of motion: (1) To express force balance of unit mass two-phase fluid instead of that of unit volume two-phase fluid; (2) To pick up the unit existing mass and the unit flowing mass as the unit mass of two-phase fluid; and (3) To apply the kinetic energy principle instead of the momentum low in the evaluation of stational inertia force term. In these three, the item: (1) is for excluding a part of momentum change or kinetic energy change due to mass change of the elementary part of fluid, which is independent of force; (2) is not to introduce a phenomenological physical model into the evaluation of phase change inertial force term; and (3) is for correctly applying the momentum law taking into account the difference of representative velocities between the main flow fluid (vapor phase or liquid phase) and the phase change part of fluid. In the Part II, characteristics of various kinds of high speed two-phase flow are clarified theoretically by using the basic equations derived in the Part I.
NASA Astrophysics Data System (ADS)
Belferman, Mariana; Katsman, Regina; Agnon, Amotz
2015-04-01
The Levant has been repeatedly devastated by numerous earthquakes since prehistorical time, as recorded in historical documents, archaeological ruins, and sedimentary archives. In order to understand the role of the dynamics of the water bodies in triggering the deformations in the Levant basin, a new theoretical thermo-mechanical model is constructed and extended by including a fluid flow component. The latter is modeled on a basis of two-way poroelastic coupling with momentum equation. This coupling is essential to capture the fluid flow evolution induced by dynamic water loading and to resolve porosity changes. All the components of the model, namely elasticity, creep, plasticity, fluid flow, etc., have been extensively verified and presented. Results of the initial sensitivity analysis addressing the relative importance of each process in earthquakes triggering are discussed. The rich archives of pre-instrumental destructive earthquakes will set constraints for future modeling under the present formulation.
NASA Astrophysics Data System (ADS)
Meakin, Paul; Tartakovsky, Alexandre M.
2009-07-01
In the subsurface, fluids play a critical role by transporting dissolved minerals, colloids, and contaminants (sometimes over long distances); by mediating dissolution and precipitation processes; and by enabling chemical transformations in solution and at mineral surfaces. Although the complex geometries of fracture apertures, fracture networks, and pore spaces may make it difficult to accurately predict fluid flow in saturated (single-phase) subsurface systems, well-developed methods are available. The simulation of multiphase fluid flow in the subsurface is much more challenging because of the large density and/or viscosity ratios found in important applications (water/air in the vadose zone; water/oil, water/gas, gas/oil, and water/oil/gas in hydrocarbon reservoirs; water/air/nonaqueous phase liquids (nonaqueous phase liquids/dense nonaqueous phase liquids) in contaminated vadose zone systems; and gas/molten rock in volcanic systems, for example). In addition, the complex behavior of fluid-fluid-solid contact lines and their impact on dynamic contact angles must also be taken into account and coupled with the fluid flow. Here we review the methods that are currently being used to simulate pore-scale multiphase fluid flow and reactive transport in fractured and porous media. After the introduction, the review begins with an overview of the fundamental physics of multiphase fluids flow followed by a more detailed discussion of the complex dynamic behavior of contact lines and contact angles, an important barrier to accurate pore-scale modeling and simulation. The main part of the review focuses on five different approaches: pore network models, lattice gas and lattice Boltzmann methods, Monte Carlo methods, particle methods (molecular dynamics, dissipative particle dynamics, and smoothed particle hydrodynamics), and traditional grid-based computational fluid dynamics coupled with interface tracking and a contact angle model. Finally, the review closes with a
NASA Astrophysics Data System (ADS)
Song, Yongjia; Hu, Hengshan; Rudnicki, John W.
2016-07-01
Grain-scale local fluid flow is an important loss mechanism for attenuating waves in cracked fluid-saturated poroelastic rocks. In this study, a dynamic elastic modulus model is developed to quantify local flow effect on wave attenuation and velocity dispersion in porous isotropic rocks. The Eshelby transform technique, inclusion-based effective medium model (the Mori-Tanaka scheme), fluid dynamics and mass conservation principle are combined to analyze pore-fluid pressure relaxation and its influences on overall elastic properties. The derivation gives fully analytic, frequency-dependent effective bulk and shear moduli of a fluid-saturated porous rock. It is shown that the derived bulk and shear moduli rigorously satisfy the Biot-Gassmann relationship of poroelasticity in the low-frequency limit, while they are consistent with isolated-pore effective medium theory in the high-frequency limit. In particular, a simplified model is proposed to quantify the squirt-flow dispersion for frequencies lower than stiff-pore relaxation frequency. The main advantage of the proposed model over previous models is its ability to predict the dispersion due to squirt flow between pores and cracks with distributed aspect ratio instead of flow in a simply conceptual double-porosity structure. Independent input parameters include pore aspect ratio distribution, fluid bulk modulus and viscosity, and bulk and shear moduli of the solid grain. Physical assumptions made in this model include (1) pores are inter-connected and (2) crack thickness is smaller than the viscous skin depth. This study is restricted to linear elastic, well-consolidated granular rocks.
Interpretation and modeling of the averaged equations for a fluid-solid flow
NASA Technical Reports Server (NTRS)
Shen, Hayley H.; Hwang, Guann-Jiun
1989-01-01
A self-consistent derivation of the conservation laws is given for flows of a fluid-solid mixture. A unified analytical framework for obtaining constitutive relations is provided. This analysis uses a control volume/control surface approach that is widely used in fluid mechanics. All terms in the governing equations and the constitutive relations are written in terms of the mass-weighted averages except solid concentration. It is believed that the mass-weighted average is the natural bridge between micromechanics and constitutive relations. The derived momentum equations contain terms that differ from all existing models except that of Prosperetti and Jones (1984). However, their assumptions are not needed here. Special attention is given to the solid phase pressure. The physical basis of the previously assumed form for this pressure (Givler 1987) becomes clear. A number of related phenomena are also discussed. These include the anti-diffusion and anisotropic normal stresses. The energy equations are also different from existing models.
A unified approach to fluid-flow, geomechanical, and seismic modelling
NASA Astrophysics Data System (ADS)
Yarushina, Viktoriya; Minakov, Alexander
2016-04-01
The perturbations of pore pressure can generate seismicity. This is supported by observations from human activities that involve fluid injection into rocks at high pressure (hydraulic fracturing, CO2 storage, geothermal energy production) and natural examples such as volcanic earthquakes. Although the seismic signals that emerge during geotechnical operations are small both in amplitude and duration when compared to natural counterparts. A possible explanation for the earthquake source mechanism is based on a number of in situ stress measurements suggesting that the crustal rocks are close to its plastic yield limit. Hence, a rapid increase of the pore pressure decreases the effective normal stress, and, thus, can trigger seismic shear deformation. At the same time, little attention has been paid to the fact that the perturbation of fluid pressure itself represents an acoustic source. Moreover, non-double-couple source mechanisms are frequently reported from the analysis of microseismicity. A consistent formulation of the source mechanism describing microseismic events should include both a shear and isotropic component. Thus, improved understanding of the interaction between fluid flow and seismic deformation is needed. With this study we aim to increase the competence in integrating real-time microseismic monitoring with geomechanical modelling such that there is a feedback loop between monitored deformation and stress field modelling. We propose fully integrated seismic, geomechanical and reservoir modelling. Our mathematical formulation is based on fundamental set of force balance, mass balance, and constitutive poro-elastoplastic equations for two-phase media consisting of deformable solid rock frame and viscous fluid. We consider a simplified 1D modelling setup for consistent acoustic source and wave propagation in poro-elastoplastic media. In this formulation the seismic wave is generated due to local changes of the stress field and pore pressure induced by
Hsieh, Paul A.
2001-01-01
This report serves as a user?s guide for two computer models: TopoDrive and ParticleFlow. These two-dimensional models are designed to simulate two ground-water processes: topography-driven flow and advective transport of fluid particles. To simulate topography-driven flow, the user may specify the shape of the water table, which bounds the top of the vertical flow section. To simulate transport of fluid particles, the model domain is a rectangle with overall flow from left to right. In both cases, the flow is under steady state, and the distribution of hydraulic conductivity may be specified by the user. The models compute hydraulic head, ground-water flow paths, and the movement of fluid particles. An interactive visual interface enables the user to easily and quickly explore model behavior, and thereby better understand ground-water flow processes. In this regard, TopoDrive and ParticleFlow are not intended to be comprehensive modeling tools, but are designed for modeling at the exploratory or conceptual level, for visual demonstration, and for educational purposes.
NASA Astrophysics Data System (ADS)
Chao, Zhongxi; Wang, Yuefa; Jakobsen, Jana P.; Fernandino, Maria; Jakobsen, Hugo A.
2011-12-01
A turbulent multi-fluid reactive fluid model is presented in the paper, which is a combination of a kinetic theory granular flow multi-fluid model(Chao et al., 2011) and the reaction kinetics description(Lindborg, 2008). A two dimensional in-house code was developed to simulate the gas-catalyst-sorbent three-phase reactive flow in the sorption enhanced steam methane reforming fluidized bed reactor. In the simulation, Ca-based sorbents and Ni/MgAl2O3 catalysts are used. The simulation results show that a high production of hydrogen in SE-SMR is obtained compared with the conventional SMR process. The increase of the gas fluidization velocity does not affect the purity of the product hydrogen apparently,while it can shorten the time to get to the breakthrough apparently. The increase of the steam/carbon ratio can increase the purity of the product hydrogen. A homogeneous gas temperature distribution is found which is due to the gas, particle turbulent flows and the heat balance of the SMR-CO2 adsorption reactions. These simulation results are in good agreement with the experimental results from Johnsen et al. (2006a).
McKay, Mark D.; Sweeney, Chad E.; Spangler, Jr., B. Samuel
1993-01-01
A flow meter and temperature measuring device comprising a tube with a body centered therein for restricting flow and a sleeve at the upper end of the tube to carry several channels formed longitudinally in the sleeve to the appropriate axial location where they penetrate the tube to allow pressure measurements and temperature measurements with thermocouples. The high pressure measurement is made using a channel penetrating the tube away from the body and the low pressure measurement is made at a location at the widest part of the body. An end plug seals the end of the device and holes at its upper end allow fluid to pass from the interior of the tube into a plenum. The channels are made by cutting grooves in the sleeve, the grooves widened at the surface of the sleeve and then a strip of sleeve material is welded to the grooves closing the channels. Preferably the sleeve is packed with powdered graphite before cutting the grooves and welding the strips.
McKay, M.D.; Sweeney, C.E.; Spangler, B.S. Jr.
1993-11-30
A flow meter and temperature measuring device are described comprising a tube with a body centered therein for restricting flow and a sleeve at the upper end of the tube to carry several channels formed longitudinally in the sleeve to the appropriate axial location where they penetrate the tube to allow pressure measurements and temperature measurements with thermocouples. The high pressure measurement is made using a channel penetrating the tube away from the body and the low pressure measurement is made at a location at the widest part of the body. An end plug seals the end of the device and holes at its upper end allow fluid to pass from the interior of the tube into a plenum. The channels are made by cutting grooves in the sleeve, the grooves widened at the surface of the sleeve and then a strip of sleeve material is welded to the grooves closing the channels. Preferably the sleeve is packed with powdered graphite before cutting the grooves and welding the strips. 7 figures.
Qayyum, Mubashir; Khan, Hamid; Rahim, M. Tariq; Ullah, Inayat
2015-01-01
The aim of this article is to model and analyze an unsteady axisymmetric flow of non-conducting, Newtonian fluid squeezed between two circular plates passing through porous medium channel with slip boundary condition. A single fourth order nonlinear ordinary differential equation is obtained using similarity transformation. The resulting boundary value problem is solved using Homotopy Perturbation Method (HPM) and fourth order Explicit Runge Kutta Method (RK4). Convergence of HPM solution is verified by obtaining various order approximate solutions along with absolute residuals. Validity of HPM solution is confirmed by comparing analytical and numerical solutions. Furthermore, the effects of various dimensionless parameters on the longitudinal and normal velocity profiles are studied graphically. PMID:25738864
A critical evaluation of various turbulence models as applied to internal fluid flows
NASA Technical Reports Server (NTRS)
Nallasamy, M.
1985-01-01
Models employed in the computation of turbulent flows are described and their application to internal flows is evaluated by examining the predictions of various turbulence models in selected flow configurations. The main conclusions are: (1) the k-epsilon model is used in a majority of all the two-dimensional flow calculations reported in the literature; (2) modified forms of the k-epsilon model improve the performance for flows with streamline curvature and heat transfer; (3) for flows with swirl, the k-epsilon model performs rather poorly; the algebraic stress model performs better in this case; and (4) for flows with regions of secondary flow (noncircular duct flows), the algebraic stress model performs fairly well for fully developed flow, for developing flow, the algebraic stress model performance is not good; a Reynolds stress model should be used. False diffusion and inlet boundary conditions are discussed. Countergradient transport and its implications in turbulence modeling is mentioned. Two examples of recirculating flow predictions obtained using PHOENICS code are discussed. The vortex method, large eddy simulation (modeling of subgrid scale Reynolds stresses), and direct simulation, are considered. Some recommendations for improving the model performance are made. The need for detailed experimental data in flows with strong curvature is emphasized.
Priyadharshini, S.; Ponalagusamy, R.
2015-01-01
An analysis of blood flow through a tapered artery with stenosis and dilatation has been carried out where the blood is treated as incompressible Herschel-Bulkley fluid. A comparison between numerical values and analytical values of pressure gradient at the midpoint of stenotic region shows that the analytical expression for pressure gradient works well for the values of yield stress till 2.4. The wall shear stress and flow resistance increase significantly with axial distance and the increase is more in the case of converging tapered artery. A comparison study of velocity profiles, wall shear stress, and flow resistance for Newtonian, power law, Bingham-plastic, and Herschel-Bulkley fluids shows that the variation is greater for Herschel-Bulkley fluid than the other fluids. The obtained velocity profiles have been compared with the experimental data and it is observed that blood behaves like a Herschel-Bulkley fluid rather than power law, Bingham, and Newtonian fluids. It is observed that, in the case of a tapered stenosed tube, the streamline pattern follows a convex pattern when we move from r/R = 0 to r/R = 1 and it follows a concave pattern when we move from r/R = 0 to r/R = −1. Further, it is of opposite behaviour in the case of a tapered dilatation tube which forms new information that is, for the first time, added to the literature. PMID:27041979
Priyadharshini, S; Ponalagusamy, R
2015-01-01
An analysis of blood flow through a tapered artery with stenosis and dilatation has been carried out where the blood is treated as incompressible Herschel-Bulkley fluid. A comparison between numerical values and analytical values of pressure gradient at the midpoint of stenotic region shows that the analytical expression for pressure gradient works well for the values of yield stress till 2.4. The wall shear stress and flow resistance increase significantly with axial distance and the increase is more in the case of converging tapered artery. A comparison study of velocity profiles, wall shear stress, and flow resistance for Newtonian, power law, Bingham-plastic, and Herschel-Bulkley fluids shows that the variation is greater for Herschel-Bulkley fluid than the other fluids. The obtained velocity profiles have been compared with the experimental data and it is observed that blood behaves like a Herschel-Bulkley fluid rather than power law, Bingham, and Newtonian fluids. It is observed that, in the case of a tapered stenosed tube, the streamline pattern follows a convex pattern when we move from r/R = 0 to r/R = 1 and it follows a concave pattern when we move from r/R = 0 to r/R = -1. Further, it is of opposite behaviour in the case of a tapered dilatation tube which forms new information that is, for the first time, added to the literature.
Priyadharshini, S; Ponalagusamy, R
2015-01-01
An analysis of blood flow through a tapered artery with stenosis and dilatation has been carried out where the blood is treated as incompressible Herschel-Bulkley fluid. A comparison between numerical values and analytical values of pressure gradient at the midpoint of stenotic region shows that the analytical expression for pressure gradient works well for the values of yield stress till 2.4. The wall shear stress and flow resistance increase significantly with axial distance and the increase is more in the case of converging tapered artery. A comparison study of velocity profiles, wall shear stress, and flow resistance for Newtonian, power law, Bingham-plastic, and Herschel-Bulkley fluids shows that the variation is greater for Herschel-Bulkley fluid than the other fluids. The obtained velocity profiles have been compared with the experimental data and it is observed that blood behaves like a Herschel-Bulkley fluid rather than power law, Bingham, and Newtonian fluids. It is observed that, in the case of a tapered stenosed tube, the streamline pattern follows a convex pattern when we move from r/R = 0 to r/R = 1 and it follows a concave pattern when we move from r/R = 0 to r/R = -1. Further, it is of opposite behaviour in the case of a tapered dilatation tube which forms new information that is, for the first time, added to the literature. PMID:27041979
Khosravian, N; Rafii-Tabar, H
2008-07-01
In the design of nanotube-based fluidic devices, a critical issue is the effect of the induced vibrations in the nanotube arising from the fluid flow, since these vibrations can promote structural instabilities, such as buckling transitions. It is known that the induced resonant frequencies depend on the fluid flow velocity in a significant manner. We have studied, for the first time, the flow of a non-viscous fluid in stubby multi-walled carbon nanotubes, using the Timoshenko classical beam theory to model the nanotubes as a continuum structure. We have obtained the variations of the resonant frequencies with the fluid flow velocity under several experimentally interesting boundary conditions and aspect ratios of the nanotube. The main finding from our work is that, compared to an Euler-Bernoulli classical beam model of a nanotube, the Timoshenko beam predicts the loss of stability at lower fluid flow velocities. PMID:21828715
Acoustic concentration of particles in fluid flow
Ward, Michael D.; Kaduchak, Gregory
2010-11-23
An apparatus for acoustic concentration of particles in a fluid flow includes a substantially acoustically transparent membrane and a vibration generator that define a fluid flow path therebetween. The fluid flow path is in fluid communication with a fluid source and a fluid outlet and the vibration generator is disposed adjacent the fluid flow path and is capable of producing an acoustic field in the fluid flow path. The acoustic field produces at least one pressure minima in the fluid flow path at a predetermined location within the fluid flow path and forces predetermined particles in the fluid flow path to the at least one pressure minima.
Well-posedness and convergence of cfd two-fluid model for bubbly flows
NASA Astrophysics Data System (ADS)
Vaidheeswaran, Avinash
The current research is focused on developing a well-posed multidimensional CFD two-fluid model (TFM) for bubbly flows. Two-phase flows exhibit a wide range of local flow instabilities such as Kelvin-Helmholtz, Rayleigh-Taylor, plume and jet instabilities. They arise due to the density difference and/or the relative velocity between the two phases. A physically correct TFM is essential to model these instabilities. However, this is not the case with the TFMs in numerical codes, which can be shown to have complex eigenvalues due to incompleteness and hence are ill-posed as initial value problems. A common approach to regularize an incomplete TFM is to add artificial physics or numerically by using a coarse grid or first order methods. However, it eliminates the local physical instabilities along with the undesired high frequency oscillations resulting from the ill-posedness. Thus, the TFM loses the capability to predict the inherent local dynamics of the two-phase flow. The alternative approach followed in the current study is to introduce appropriate physical mechanisms that make the TFM well-posed. First a well-posed 1-D TFM for vertical bubbly flows is analyzed with characteristics, and dispersion analysis. When an incomplete TFM is used, it results in high frequency oscillations in the solution. It is demonstrated through the travelling void wave problem that, by adding the missing short wavelength physics to the numerical TFM, this can be removed by making the model well-posed. To extend the limit of well-posedness beyond the well-known TFM of Pauchon and Banerjee [1], the mechanism of collision is considered, and it is shown by characteristics analysis that the TFM then becomes well-posed for all void fractions of practical interest. The aforementioned ideas are then extended to CFD TFM. The travelling void wave problem is again used to demonstrate that by adding appropriate physics, the problem of ill-posedness is resolved. Furthermore, issues pertaining to
Cerebrospinal fluid flow in adults.
Bradley, William G; Haughton, Victor; Mardal, Kent-Andre
2016-01-01
This chapter uses magnetic resonance imaging phase-contrast cerebrospinal fluid (CSF) flow measurements to predict which clinical normal-pressure hydrocephalus (NPH) patients will respond to shunting as well as which patients with Chiari I are likely to develop symptoms of syringomyelia. Symptomatic NPH patients with CSF flow (measured as the aqueductal CSF stroke volume) which is shown to be hyperdynamic (defined as twice normal) are quite likely to respond to ventriculoperitoneal shunting. The hyperdynamic CSF flow results from normal systolic brain expansion compressing the enlarged ventricles. When atrophy occurs, there is less brain expansion, decreased aqueductal CSF flow, and less likelihood of responding to shunting. It appears that NPH is a "two-hit" disease, starting as benign external hydrocephalus in infancy, followed by deep white-matter ischemia in late adulthood, which causes increased resistance to CSF outflow through the extracellular space of the brain. Using computational flow dynamics (CFD), CSF flow can be modeled at the foramen magnum and in the upper cervical spine. As in the case of NPH, hyperdynamic CSF flow appears to cause the signs and symptoms in Chiari I and can provide an additional indication for surgical decompression. CFD can also predict CSF pressures over the cardiac cycle. It has been hypothesized that elevated pressure pulses may be a significant etiologic factor in some cases of syringomyelia. PMID:27432684
Fluid flows around nanoelectromechanical resonators
NASA Astrophysics Data System (ADS)
Svitelskiy, O.; Sauer, V.; Liu, N.; Vick, D.; Cheng, K. M.; Freeman, M. R.; Hiebert, W. K.
2012-02-01
To explore properties of fluids on a nanosize scale, we fabricated by a standard top down technique a series of nanoelectromechanical resonators (cantilevers and bridges) with widths w and thicknesses t from 100 to 500 nm; lengths l from 0.5 to 12 micron; and resonant frequencies f from 10 to 400 MHz. For the sake of purity of the experiment, the undercut in the widest (w=500 nm) devices was eliminated using the focused ion beam. To model the fluidic environment the devices were placed in the atmosphere of compressed gases (He, N2, CO2, Ar, H2) at pressures from vacuum up to 20 MPa, and in liquid CO2; their properties were studied by the real time stroboscopic optical interferometry. Thus, we fully explored the Newtonian and non-Newtonian flow damping models. Observing free molecular flow extending above atmospheric pressure, we find the fluid relaxation time model to be the best approximation throughout, but not beyond, the non-Newtonian regime, and both, vibrating spheres model and the model based on Knudsen number, to be valid in the viscous limit.
A simple model of fluid flow and electrolyte balance in the body
NASA Technical Reports Server (NTRS)
White, R. J.; Neal, L.
1973-01-01
The model is basically a three-compartment model, the three compartments being the plasma, interstitial fluid and cellular fluid. Sodium, potassium, chloride and urea are the only major solutes considered explicitly. The control of body water and electrolyte distribution is affected via drinking and hormone levels. Basically, the model follows the effect of various oral input water loads on solute and water distribution throughout the body.
NASA Astrophysics Data System (ADS)
Crone, T. J.; Sohn, R. A.; Barreyre, T.
2014-12-01
Recent measurements of ocean bottom pressure suggest that hydrothermal flow induces cm-scale periodic ground surface displacement (GSD) at the Trans-Atlantic Geotraverse (TAG) hydrothermal field on the Mid-Atlantic Ridge (Sohn et al., 2009). The pressure measurements contain spectral peaks and harmonics with periods ranging from 22 to 53 min, none of which can be attributed to oceanographic or Earth tide processes. It is hypothesized that GSD cycles in this system may result from a nonlinear feedback between pore pressure and permeability in the hydrothermal system. To test this hypothesis we have developed a poroelastic convection model representing the upper crustal section at TAG that includes a "switching" type pressure-permeability feedback in the stockwork zone of the hydrothermal system. In this zone, the permeability increases when the pressure reaches a critical high value, and decreases when it reaches a critical low value. This behavior simulates the opening and closing of cracks within the hydrothermal system, and is similar to mechanisms that have been proposed for dike propagation in magmatic systems (Buck et al., 2006). Our modeling suggests that this mechanism can generate GSD that are similar to those observed at TAG. We are currently using these models to explore the sensitivity of inflation and deflation rates to system properties such as the geometry of the stockwork zone, the temperature of fluid in the upflow zone, the elastic properties of the lithosphere, and the relationship between pore pressure and permeability.
Kenkeremath, D.
1985-05-01
Numerical simulation models and data bases that were developed for DOE as part of a number of geothermal programs have been assessed with respect to their overall stage of development and usefulness. This report combines three separate studies that focus attention upon: (1) economic models related to geothermal energy; (2) physical geothermal system models pertaining to thermal energy and the fluid medium; and (3) geothermal energy data bases. Computerized numerical models pertaining to the economics of extracting and utilizing geothermal energy have been summarized and catalogued with respect to their availability, utility and function. The 19 models that are discussed in detail were developed for use by geothermal operators, public utilities, and lending institutions who require a means to estimate the value of a given resource, total project costs, and the sensitivity of these values to specific variables. A number of the models are capable of economically assessing engineering aspects of geothermal projects. Computerized simulations of heat distribution and fluid flow have been assessed and are presented for ten models. Five of the models are identified as wellbore simulators and five are described as reservoir simulators. Each model is described in terms of its operational characteristics, input, output, and other pertinent attributes. Geothermal energy data bases are reviewed with respect to their current usefulness and availability. Summaries of eight data bases are provided in catalogue format, and an overall comparison of the elements of each data base is included.
Takatani, H.; Gandin, C.A.; Rappaz, M.
2000-02-09
Columnar dendritic grains of steel growth in the presence of fluid flow (e.g., solidified on turning rolls) have been characterized by Electron Backscattered Diffraction (EBSD) technique. It is shown that grains have a random crystallographic orientation at the surfaces of the sheet in contact with the mould. In the middle of the sheet, the grains which have survived the growth selection mechanisms exhibit a (100) texture in which the average dendrite trunk direction is not exactly aligned with the thermal gradient (i.e., the normal to the surfaces of the sheet). It is tilted by about 15{degree} toward the upstream direction. This deviation is examined by simulations of grain structure formation based on a three-dimensional Cellular Automation (CA)-Finite Element (FE) (3D CAFE) model, which has been modified in order to account for fluid flow effects. The modified Ca algorithm includes a growth kinetics of the dendrites which is a function of both the undercooling and fluid flow direction. It is validated by comparing the predicted shape of an individual grain growing under given thermal and fluid flow conditions with an analytical solution. The 3D CAFE predictions of the columnar grains grown in the presence of fluid flow are in good agreement with the experimental EBSB results.
Relaminarization of fluid flows
NASA Technical Reports Server (NTRS)
Narasimha, R.; Sreenivasan, K. R.
1979-01-01
The mechanisms of the relaminarization of turbulent flows are investigated with a view to establishing any general principles that might govern them. Three basic archetypes of reverting flows are considered: the dissipative type, the absorptive type, and the Richardson type exemplified by a turbulent boundary layer subjected to severe acceleration. A number of other different reverting flows are then considered in the light of the analysis of these archetypes, including radial Poiseuille flow, convex boundary layers, flows reverting by rotation, injection, and suction, as well as heated horizontal and vertical gas flows. Magnetohydrodynamic duct flows are also examined. Applications of flow reversion for turbulence control are discussed.
Pawaskar, Sainath Shrikant; Fisher, John; Jin, Zhongmin
2010-03-01
Contact detection in cartilage contact mechanics is an important feature of any analytical or computational modeling investigation when the biphasic nature of cartilage and the corresponding tribology are taken into account. The fluid flow boundary conditions will change based on whether the surface is in contact or not, which will affect the interstitial fluid pressurization. This in turn will increase or decrease the load sustained by the fluid phase, with a direct effect on friction, wear, and lubrication. In laboratory experiments or clinical hemiarthroplasty, when a rigid indenter or metallic prosthesis is used to apply load to the cartilage, there will not be any fluid flow normal to the surface in the contact region due to the impermeable nature of the indenter/prosthesis. In the natural joint, on the other hand, where two cartilage surfaces interact, flow will depend on the pressure difference across the interface. Furthermore, in both these cases, the fluid would flow freely in non-contacting regions. However, it should be pointed out that the contact area is generally unknown in advance in both cases and can only be determined as part of the solution. In the present finite element study, a general and robust algorithm was proposed to decide nodes in contact on the cartilage surface and, accordingly, impose the fluid flow boundary conditions. The algorithm was first tested for a rigid indenter against cartilage model. The algorithm worked well for two-dimensional four-noded and eight-noded axisymmetric element models as well as three-dimensional models. It was then extended to include two cartilages in contact. The results were in excellent agreement with the previous studies reported in the literature.
Barker, Andrew T. Cai Xiaochuan
2010-02-01
We introduce and study numerically a scalable parallel finite element solver for the simulation of blood flow in compliant arteries. The incompressible Navier-Stokes equations are used to model the fluid and coupled to an incompressible linear elastic model for the blood vessel walls. Our method features an unstructured dynamic mesh capable of modeling complicated geometries, an arbitrary Lagrangian-Eulerian framework that allows for large displacements of the moving fluid domain, monolithic coupling between the fluid and structure equations, and fully implicit time discretization. Simulations based on blood vessel geometries derived from patient-specific clinical data are performed on large supercomputers using scalable Newton-Krylov algorithms preconditioned with an overlapping restricted additive Schwarz method that preconditions the entire fluid-structure system together. The algorithm is shown to be robust and scalable for a variety of physical parameters, scaling to hundreds of processors and millions of unknowns.
Fluid Flow Phenomena during Welding
Zhang, Wei
2011-01-01
MOLTEN WELD POOLS are dynamic. Liquid in the weld pool in acted on by several strong forces, which can result in high-velocity fluid motion. Fluid flow velocities exceeding 1 m/s (3.3 ft/s) have been observed in gas tungsten arc (GTA) welds under ordinary welding conditions, and higher velocities have been measured in submerged arc welds. Fluid flow is important because it affects weld shape and is related to the formation of a variety of weld defects. Moving liquid transports heat and often dominates heat transport in the weld pool. Because heat transport by mass flow depends on the direction and speed of fluid motion, weld pool shape can differ dramatically from that predicted by conductive heat flow. Temperature gradients are also altered by fluid flow, which can affect weld microstructure. A number of defects in GTA welds have been attributed to fluid flow or changes in fluid flow, including lack of penetration, top bead roughness, humped beads, finger penetration, and undercutting. Instabilities in the liquid film around the keyhole in electron beam and laser welds are responsible for the uneven penetration (spiking) characteristic of these types of welds.
Guidelines for optimizing multilevel ECN using fluid-flow-based TCP model
NASA Astrophysics Data System (ADS)
Quet, Pierre-Francois; Chellappan, Sriram; Durresi, Arjan; Sridharan, Mukundan; Ozbay, Hitay; Jain, Raj
2002-07-01
Congestion avoidance on today's Internet is mainly provided by the combination of the TCP protocol and Active Queue Management (AQM) schemes such as the de facto standard RED (Random Early Detection). When used with ECN (Explicit Congestion Notification), these algorithms can be modeled as a feedback control system in which the feedback information is carried on a single bit. A modification of this scheme called MECN was proposed, where the marking information is carried using 2 bits. MECN conveys more accurate feedback about the network congestion to the source than the current 1-bit ECN. The TCP source reaction was modified so that it takes advantage of the extra information about congestion and adapts faster to the changing congestion scenario leading to a smoother decrease in the sending rates of the sources upon congestion detection and consequently resulting in an increase in the router's throughput. A linearized fluid flow model already developed for ECN is extended to our case. Using control theoretic tools we justify the performance obtained in using the MECN scheme and give guidelines for optimizing its parameters. We use ns simulations to illustrate the performance improvement from the point of better throughput and low level of oscillations in the queue.
NASA Astrophysics Data System (ADS)
Guo, Liancheng; Morita, Koji; Tagami, Hirotaka; Tobita, Yoshiharu
2014-06-01
The postulated core disruptive accidents (CDAs) are regarded as particular difficulties in the safety analysis of liquid-metal fast reactors (LMFRs). In CDAs, the motions and interactions of solid particles, such as refrozen fuels, disrupted pellets, etc., not only dominate fundamental behaviors of multiphase flows, but also drastically influence the process of CDAs. The fast reactor safety analysis code, SIMMER-IV, which is a 3D, multi-velocity-field, multiphase, multicomponent, Eulerian, fluid dynamics code coupled with a fuel-pin model and a space- and energy-dependent neutron kinetics model, was successfully applied to a series of CDA assessments. However, strong interactions among solid particles as well as particle characteristics in multiphase flows with rich solid particles were not taken into consideration for fluid-dynamics models of SIMMER-IV. In this article, a hybrid method for multiphase flow analysis is developed by coupling the discrete element method (DEM) with the multi-fluid model of SIMMER-IV. In the coupling algorithm, motions of liquid and gas phases are solved by a time-factorization (time-splitting) method. For the solid phases, contacts among particles and interactions with fluid phases are considered through DEM. Numerical simulations of dam-break behavior with rich solid particles show reasonable agreements with corresponding experimental results. It is expected that SIMMER-IV coupled with DEM could provide a promising and useful computational tool for complicated multiphase-flow phenomena with high concentration of solid particles.
Quaini, A.; Canic, S.; Glowinski, R.; Igo, S.; Hartley, C.J.; Zoghbi, W.; Little, S.
2011-01-01
This work presents a validation of a fluid-structure interaction computational model simulating the flow conditions in an in vitro mock heart chamber modeling mitral valve regurgitation during the ejection phase during which the trans-valvular pressure drop and valve displacement are not as large. The mock heart chamber was developed to study the use of 2D and 3D color Doppler techniques in imaging the clinically relevant complex intra-cardiac flow events associated with mitral regurgitation. Computational models are expected to play an important role in supporting, refining, and reinforcing the emerging 3D echocardiographic applications. We have developed a 3D computational fluid-structure interaction algorithm based on a semi-implicit, monolithic method, combined with an arbitrary Lagrangian-Eulerian approach to capture the fluid domain motion. The mock regurgitant mitral valve corresponding to an elastic plate with a geometric orifice, was modeled using 3D elasticity, while the blood flow was modeled using the 3D Navier-Stokes equations for an incompressible, viscous fluid. The two are coupled via the kinematic and dynamic conditions describing the two-way coupling. The pressure, the flow rate, and orifice plate displacement were measured and compared with numerical simulation results. In-line flow meter was used to measure the flow, pressure transducers were used to measure the pressure, and a Doppler method developed by one of the authors was used to measure the axial displacement of the orifice plate. The maximum recorded difference between experiment and numerical simulation for the flow rate was 4%, the pressure 3.6%, and for the orifice displacement 15%, showing excellent agreement between the two. PMID:22138194
Reactive fluid flow models and applications to diagenesis, mineral deposits and crustal rocks
Lasaga, A.C.; Rye, D.M.
1993-08-01
Funds are requested for a combined theoretical and field study of coupled fluid flow, heat and mass transport, and chemical reaction in hydrothermal and metamorphic systems. An existing computer code developed by the applicants which numerically treats multi-component, finite-rate reactions combined with advective and dispersive transport in one and two dimensions and which incorporates isotopic exchange and heat and mass transfer will continue to be developed and applied in a variety of geological settings. The code we have developed simultaneously solves for mass transport and reaction, thus offering a significant improvement in computational efficiency over existing ``batch`` reaction path codes. By coupling flow and chemical reaction in a hydrothermal system, we can explicitly investigate the extent to which characteristic flow-reaction paths govern the chemical evolution of the fluids in a hydrothermal system. The concept of a flow-reaction path is particularly important where certain portions of mature hydrothermal systems may exhaust the buffer capacity of the rock as the primary mineralogy is consumed. In these instances 7 fluids traversing distinct regions within the hydrothermal system may experience very different reaction histories, even where the system can be described as nearly isothermal. The study of paleo-hydrothermal systems can yield some important insights into the chemical dynamics of hydrothermal systems in general. As an example of a paleo-hydrothermal system, we have considered the geochemical evolution of ``porphyry-copper`` type mineralization.
NASA Astrophysics Data System (ADS)
Čanić, Sunčica; Mikelić, Andro; Tambača, Josip
2005-12-01
We derive a closed system of effective equations describing a time-dependent flow of a viscous incompressible Newtonian fluid through a long and narrow elastic tube. The 3D axially symmetric incompressible Navier-Stokes equations are used to model the flow. Two models are used to describe the tube wall: the linear membrane shell model and the linearly elastic membrane and the curved, linearly elastic Koiter shell model. We study the behavior of the coupled fluid-structure interaction problem in the limit when the ratio between the radius and the length of the tube, ɛ, tends to zero. We obtain the reduced equations that are of Biot type with memory. An interesting feature of the reduced equations is that the memory term explicitly captures the viscoelastic nature of the coupled problem. Our model provides significant improvement over the standard 1D approximations of the fluid-structure interaction problem, all of which assume an ad hoc closure assumption for the velocity profile. We performed experimental validation of the reduced model using a mock circulatory flow loop assembled at the Cardiovascular Research Laboratory at the Texas Heart Institute. Experimental results show excellent agreement with the numerically calculated solution. Major applications include blood flow through large human arteries. To cite this article: S. Čanić et al., C. R. Mecanique 333 (2005).
Fluid flow modeling at the Lusi mud eruption, East java, Indonesia.
NASA Astrophysics Data System (ADS)
Collignon, Marine; Schmid, Daniel; Mazzini, Adriano
2016-04-01
The 29th of may 2006, gas water and mud breccia started to erupt at several localities along the Watukosek fault system, in the Sidoarjo Regency in East java, Indonesia. The most prominent eruption, named Lusi, is still active and covering a surface of nearly 7 km2, resulting in the displacement of ~ 30 000 people. Although the origin and the chemical composition of the erupted fluids have been documented, the mechanical and physical properties of the mud are poorly constrained, and many aspects still remain not understood. Very little is known about the internal dynamics of the Lusi conduit(s). In this study, conducted in the framework of the Lusi Lab project (ERC grant n°308126) we use both analytical and numerical methods to better understand the flow dynamics within the main conduit and to try to explain the longevity of the edifice. The 2D numerical model considers a vertical conduit with a reservoir at its base and solves the stokes equations, discretized on a finite element mesh. Although, three phases (solid, liquid and gas) are present in nature, we only consider the liquid phase. The solid phase is treated as rigid particles in suspension in the liquid. The gaseous phase (methane and carbon dioxide) is treated in an analytical manner using the equations of state of the H2O-CO2 and H2O-CH4 systems. Here, we discuss the effects of density, viscosity, gas concentration and clasts concentration and size on the dynamics of the flow in the conduit as well as implications of the conduit stability.
NASA Astrophysics Data System (ADS)
Steinbrenner, Julie E.
2005-11-01
Interaction between gas and liquid phases in separated flow through a channel governs flow regimes and influences the behavior of each phase. However, this interaction is not well modeled by traditional single-phase parameters. A compact model is presented which accounts for the interaction of the two phases by employing a modification to the single-phase friction factor formulation for rectangular channels. The modification represents the interaction between phases using a multiplicative factor derived from an analytical solution to stratified flow between parallel plates. Film thickness and pressure drop predictions from the model are compared with analytical solutions to two-fluid flow in a rectangular duct. Computational results are compared with experimental measurements of the liquid film thickness in stratified two-phase flow in rectangular microchannels (D = 50-500 μm) for various aspect ratios. A physical interpretation of experimental and computational results is presented.
NASA Astrophysics Data System (ADS)
Tsamopoulos, John; Karapetsas, George
2013-11-01
It is well known that during extrusion of viscoelastic fluids various flow instabilities may arise resulting in a distorted free surface. In order to investigate the factors generating these instabilities we perform a linear stability analysis at zero Reynolds number around the steady solution of the cylindrical or planar stick-slip flow for a viscoelastic fluid following the PTT model. The stick-slip flow is an important special case of the extrudate swell problem, since the latter reduces to it in the limit of infinite surface tension. We will show that the flow becomes unstable as the Weissenberg number increases above a critical value, due to a Hopf bifurcation suggesting that the flow will become periodic in time. Both the critical value of the Weissenberg number and the frequency of the instability depend strongly on the rheological parameters of the viscoelastic model. The elasticity alone can be responsible for the appearance of instabilities in the extrusion process of viscoelastic fluids and the often used assumptions of wall slip or compressibility, although they might be present, are not required. Finally, the mechanisms that produce these instabilities are examined through energy analysis of the disturbance flow. The authors would like to acknowledge the financial support by the General Secretariat of Research and Technology of Greece under the Action ``Supporting Postdoctoral Researchers'' (Grant No: PE8/906), and under the ``Excellence Program'' (Grant No: 1918)
Fluid flow modeling of resin transfer molding for composite material wind turbine blade structures.
Cairns, Douglas S.; Rossel, Scott M.
2004-06-01
Resin transfer molding (RTM) is a closed mold process for making composite materials. It has the potential to produce parts more cost effectively than hand lay-up or other methods. However, fluid flow tends to be unpredictable and parts the size of a wind turbine blade are difficult to engineer without some predictive method for resin flow. There were five goals of this study. The first was to determine permeabilities for three fabrics commonly used for RTM over a useful range of fiber volume fractions. Next, relations to estimate permeabilities in mixed fabric lay-ups were evaluated. Flow in blade substructures was analyzed and compared to predictions. Flow in a full-scale blade was predicted and substructure results were used to validate the accuracy of a full-scale blade prediction.
Mathematical model for blood flow through a bifurcated artery using couple stress fluid.
Srinivasacharya, D; Madhava Rao, G
2016-08-01
In this article, the blood flow through a bifurcated artery with mild stenosis is investigated taking blood as couple stress fluid. The artery configuring bifurcation is assumed to be symmetric about the axis of the artery and straight cylinders of finite length. The governing equations are non-dimensionalized and coordinate transformation is used to convert the irregular boundary to a regular boundary. The resulting system of equations is solved numerically using the finite difference method. The variation of shear stress, flow rate and impedance near the apex with pertinent parameters are studied graphically. It has been noticed that shear stress, flow rate and impedance have been changing suddenly with all the parameters on both sides of the apex. This occurs because of the backflow of the streaming blood at the onset of the lateral junction and secondary flow near the apex in the daughter artery. PMID:27235925
Mathematical model for blood flow through a bifurcated artery using couple stress fluid.
Srinivasacharya, D; Madhava Rao, G
2016-08-01
In this article, the blood flow through a bifurcated artery with mild stenosis is investigated taking blood as couple stress fluid. The artery configuring bifurcation is assumed to be symmetric about the axis of the artery and straight cylinders of finite length. The governing equations are non-dimensionalized and coordinate transformation is used to convert the irregular boundary to a regular boundary. The resulting system of equations is solved numerically using the finite difference method. The variation of shear stress, flow rate and impedance near the apex with pertinent parameters are studied graphically. It has been noticed that shear stress, flow rate and impedance have been changing suddenly with all the parameters on both sides of the apex. This occurs because of the backflow of the streaming blood at the onset of the lateral junction and secondary flow near the apex in the daughter artery.
NASA Astrophysics Data System (ADS)
Muha, Boris; Canić, Suncica
2013-03-01
We study a nonlinear, unsteady, moving boundary, fluid-structure interaction (FSI) problem arising in modeling blood flow through elastic and viscoelastic arteries. The fluid flow, which is driven by the time-dependent pressure data, is governed by two-dimensional incompressible Navier-Stokes equations, while the elastodynamics of the cylindrical wall is modeled by the one-dimensional cylindrical Koiter shell model. Two cases are considered: the linearly viscoelastic and the linearly elastic Koiter shell. The fluid and structure are fully coupled (two-way coupling) via the kinematic and dynamic lateral boundary conditions describing continuity of velocity (the no-slip condition), and the balance of contact forces at the fluid-structure interface. We prove the existence of weak solutions to the two FSI problems (the viscoelastic and the elastic case) as long as the cylinder radius is greater than zero. The proof is based on a novel semi-discrete, operator splitting numerical scheme, known as the kinematically coupled scheme, introduced in Guidoboni et al. (J Comput Phys 228(18):6916-6937, 2009) to numerically solve the underlying FSI problems. The backbone of the kinematically coupled scheme is the well-known Marchuk-Yanenko scheme, also known as the Lie splitting scheme. We effectively prove convergence of that numerical scheme to a solution of the corresponding FSI problem.
On the multidimensional modeling of fluid flow and heat transfer in SCWRS
Gallaway, T.; Antal, S. P.; Podowski, M. Z.
2012-07-01
The Supercritical Water Reactor (SCWR) has been proposed as one of the six Generation IV reactor design concepts under consideration. The key feature of the SCWR is that water at supercritical pressures is used as the reactor coolant. Although at such pressures, fluids do not undergo phase change as they are heated, the fluid properties experience dramatic variations throughout what is known as the pseudo-critical region. Highly nonuniform temperature and fluid property distributions are expected in the reactor core, which will have a significant impact on turbulence and heat transfer in future SCWRs. The goal of the present work has been to understand and predict the effects of these fluid property variations on turbulence and heat transfer throughout the reactor core. Spline-type property models have been formulated for water at supercritical pressures in order to include the dependence of properties on both temperature and pressure into a numerical solver. New models of turbulence and heat transfer for variable-property fluids have been developed and implemented into the NPHASE-CMFD software. The results for these models have been compared to experimental data from the Korea Atomic Energy Research Inst. (KAERI) for various heat transfer regimes. It is found that the Low-Reynolds {kappa}-{epsilon} model performs best at predicting the experimental data. (authors)
Insertable fluid flow passage bridgepiece and method
Jones, Daniel O.
2000-01-01
A fluid flow passage bridgepiece for insertion into an open-face fluid flow channel of a fluid flow plate is provided. The bridgepiece provides a sealed passage from a columnar fluid flow manifold to the flow channel, thereby preventing undesirable leakage into and out of the columnar fluid flow manifold. When deployed in the various fluid flow plates that are used in a Proton Exchange Membrane (PEM) fuel cell, bridgepieces of this invention prevent mixing of reactant gases, leakage of coolant or humidification water, and occlusion of the fluid flow channel by gasket material. The invention also provides a fluid flow plate assembly including an insertable bridgepiece, a fluid flow plate adapted for use with an insertable bridgepiece, and a method of manufacturing a fluid flow plate with an insertable fluid flow passage bridgepiece.
Modeling on Fluid Flow and Inclusion Motion in Centrifugal Continuous Casting Strands
NASA Astrophysics Data System (ADS)
Wang, Qiangqiang; Zhang, Lifeng; Sridhar, Seetharaman
2016-08-01
During the centrifugal continuous casting process, unreasonable casting parameters can cause violent level fluctuation, serious gas entrainment, and formation of frozen shell pieces at the meniscus. Thus, in the current study, a three-dimensional multiphase turbulent model was established to study the transport phenomena during centrifugal continuous casting process. The effects of nozzle position, casting and rotational speed on the flow pattern, centrifugal force acting on the molten steel, level fluctuation, gas entrainment, shear stress on mold wall, and motion of inclusions during centrifugal continuous casting process were investigated. Volume of Fluid model was used to simulate the molten steel-air two-phase. The level fluctuation and the gas entrainment during casting were calculated by user-developed subroutines. The trajectory of inclusions in the rotating system was calculated using the Lagrangian approach. The results show that during centrifugal continuous casting, a large amount of gas was entrained into the molten steel, and broken into bubbles of various sizes. The greater the distance to the mold wall, the smaller the centrifugal force. Rotation speed had the most important influence on the centrifugal force distribution at the side region. Angular moving angle of the nozzle with 8° and keeping the rotation speed with 60 revolutions per minute can somehow stabilize the level fluctuation. The increase of angular angle of nozzle from 8 to 18 deg and rotation speed from 40 to 80 revolutions per minute favored to decrease the total volume of entrained bubbles, while the increase of distance of nozzle moving left and casting speed had reverse effects. The trajectories of inclusions in the mold were irregular, and then rotated along the strand length. After penetrating a certain distance, the inclusions gradually moved to the center of billet and gathered there. More work, such as the heat transfer, the solidification, and the inclusions entrapment
Modeling of heat transfer and fluid flow in keyhole mode welding
NASA Astrophysics Data System (ADS)
Rai, Rohit
In this work, computationally efficient numerical models have been developed for linear keyhole mode LBW and EBW processes. The models combine an energy balance based model for keyhole geometry calculation with a well tested 3D heat transfer and fluid flow model. For LBW, keyhole wall temperatures are assumed to be equal to the boiling point of the alloy at 1 atm pressure. Keyhole wall temperatures in EBW are calculated from the equilibrium vapor pressure versus temperature relation for the work-piece material. The vapor pressure is, in turn, calculated from a force balance at the keyhole walls between the surface tension, vapor pressure and hydrostatic forces. A turbulence model is used to estimate the effective values of viscosity and thermal conductivity to account for the enhanced heat and mass transport in the turbulent weld pool due to the fluctuating components of velocities in both LBW and EBW. The proposed model for LBW has been tested for materials with wide ranging thermo-physical properties under varying input powers and welding speeds covering both partial and full penetration welds. The tested materials include Al 5754 alloy, A131 steel, 304L stainless steel, Ti-6Al-4V, tantalum, and vanadium. These materials vary significantly in their thermo-physical properties, including boiling point, thermal conductivity, and specific heat. The EBW model was tested for 21Cr-6Ni-9Mn steel, 304L stainless steel, and Ti-6Al-4V for different input powers and power density distributions. To improve the agreement between the calculated and experimental results, a methodology is presented to estimate the values of uncertain input parameters like absorption coefficient and beam radius using a genetic algorithm with the numerical model and limited amount of experimental data. Finally, a genetic algorithm is used with the numerical model to prescribe welding conditions that would result in a desired weld attribute. The computed weld cross-sectional geometries and thermal
Fluid Flow Within Fractured Porous Media
Crandall, D.M.; Ahmadi, G.; Smith, D.H.; Bromhal, G.S.
2006-10-01
Fractures provide preferential flow paths to subterranean fluid flows. In reservoir scale modeling of geologic flows fractures must be approximated by fairly simple formulations. Often this is accomplished by assuming fractures are parallel plates subjected to an applied pressure gradient. This is known as the cubic law. An induced fracture in Berea sandstone has been digitized to perform numerical flow simulations. A commercially available computational fluid dynamics software package has been used to solve the flow through this model. Single phase flows have been compared to experimental works in the literature to evaluate the accuracy with which this model can be applied. Common methods of fracture geometry classification are also calculated and compared to experimentally obtained values. Flow through regions of the fracture where the upper and lower fracture walls meet (zero aperture) are shown to induce a strong channeling effect on the flow. This model is expanded to include a domain of surrounding porous media through which the flow can travel. The inclusion of a realistic permeability in this media shows that the regions of small and zero apertures contribute to the greatest pressure losses over the fracture length and flow through the porous media is most prevalent in these regions. The flow through the fracture is shown to be the largest contributor to the net flow through the media. From this work, a novel flow relationship is proposed for flow through fractured media.
NASA Technical Reports Server (NTRS)
Sharp, John R.; Kittredge, Ken; Schunk, Richard G.
2003-01-01
As part of the aero-thermodynamics team supporting the Columbia Accident Investigation Board (CAB), the Marshall Space Flight Center was asked to perform engineering analyses of internal flows in the port wing. The aero-thermodynamics team was split into internal flow and external flow teams with the support being divided between shorter timeframe engineering methods and more complex computational fluid dynamics. In order to gain a rough order of magnitude type of knowledge of the internal flow in the port wing for various breach locations and sizes (as theorized by the CAB to have caused the Columbia re-entry failure), a bulk venting model was required to input boundary flow rates and pressures to the computational fluid dynamics (CFD) analyses. This paper summarizes the modeling that was done by MSFC in Thermal Desktop. A venting model of the entire Orbiter was constructed in FloCAD based on Rockwell International s flight substantiation analyses and the STS-107 reentry trajectory. Chemical equilibrium air thermodynamic properties were generated for SINDA/FLUINT s fluid property routines from a code provided by Langley Research Center. In parallel, a simplified thermal mathematical model of the port wing, including the Thermal Protection System (TPS), was based on more detailed Shuttle re-entry modeling previously done by the Dryden Flight Research Center. Once the venting model was coupled with the thermal model of the wing structure with chemical equilibrium air properties, various breach scenarios were assessed in support of the aero-thermodynamics team. The construction of the coupled model and results are presented herein.
Wetzel, L.R.; Raffensperger, J.P.; Shock, E.L.
2001-01-01
Coordinated geochemical and hydrological calculations guide our understanding of the composition, fluid flow patterns, and thermal structure of near-ridge oceanic crust. The case study presented here illustrates geochemical and thermal changes taking place as oceanic crust ages from 0.2 to 1.0 Myr. Using a finite element code, we model fluid flow and heat transport through the upper few hundred meters of an abyssal hill created at an intermediate spreading rate. We use a reaction path model with a customized database to calculate equilibrium fluid compositions and mineral assemblages of basalt and seawater at 500 bars and temperatures ranging from 150 to 400??C. In one scenario, reaction path calculations suggest that volume increases on the order of 10% may occur within portions of the basaltic basement. If this change in volume occurred, it would be sufficient to fill all primary porosity in some locations, effectively sealing off portions of the oceanic crust. Thermal profiles resulting from fluid flow simulations indicate that volume changes along this possible reaction path occur primarily within the first 0.4 Myr of crustal aging. ?? 2001 Elsevier Science B.V. All rights reserved.
A modified Shkadov's model for thin film flow of a power law fluid over an inclined surface
NASA Astrophysics Data System (ADS)
Amaouche, Mustapha; Djema, Amar; Bourdache, L.
2009-01-01
A new evolution equation coherent up to order one in the long wave parameter is derived to describe the non-linear behavior of a thin film flow down an inclined plane of a power law fluid for small to moderate Reynolds numbers. The method we have used combines the lubrication theory and the weighted residual approach, with a suitable weighting function. That approach was first developed by Ruyer-Quil and Manneville (2000) for Newtonian fluids. The model has the advantages of both the Shkadov type approach far from criticality and that of Benney close to criticality. To cite this article: M. Amaouche et al., C. R. Mecanique 337 (2009).
Proceedings of the fluid flow measurement
1995-12-31
This report presents reports which were presented at the Third International Symposium on Fluid Flow Measurement. Topics were concerned with metering, calibration, flow modeling, and gas properties. Individual reports have been processed separately for the United States Department of Energy databases.
Numerical investigation of a space-fractional model of turbulent fluid flow in rectangular ducts
NASA Astrophysics Data System (ADS)
Churbanov, Alexander G.; Vabishchevich, Petr N.
2016-09-01
Models containing fractional derivatives are among the most promising new approaches for description of turbulent flows. In the present work, a steady-state flow in a duct is considered under the condition that the turbulent diffusion is governed by a fractional power of the Laplace operator. To study numerically flows in rectangular channels, finite-difference approximations are employed. The resulting discrete problem is solved by a preconditioned conjugate gradient method. At each iteration, the problem with a fractional power of the grid Laplace operator is solved. Predictions of turbulent flows in ducts at different Reynolds numbers are presented via mean velocity fields.
Modeling of Fluid Flow and Heat Transfer in Nanotube and Nanowire Forests
NASA Astrophysics Data System (ADS)
Martin, Michael
2010-10-01
Bundles of nanotubes, also known as nanotube forests, are under consideration for applications such as chip cooling and pre-concentrators for biodetection. Scaling law analysis shows that the air flow through these forests at atmospheric pressure is in the free-molecular flow regime. Based on the linearized free-molecular flow equations, a model is presented for the pressure drop and heat transfer in these systems. The momentum and energy equations are coupled, requiring that they be solved simultaneously. Results show large pressure drops, and a non-linear pressure distribution, similar to that seen in rarefied micro-channel flows.
Dynamic simulation of wavy-stratified two-phase flow with the one-dimensional two-fluid model
NASA Astrophysics Data System (ADS)
Fullmer, William D.
The one-dimensional two-fluid model is the basis for the description of the transport of mass, momentum and energy in the thermal-hydraulic codes used for nuclear reactor safety analysis. Unlike other physical transport models, the one-dimensional two-fluid model suffers from the possibility of being ill-posed as an initial-boundary value problem depending on the flow conditions and the relevant physical closure laws. Typically, the ill-posedness is dealt with through either excessive numerical damping or the addition of unphysical closure laws designed for the sole purpose of hyperbolization. Unfortunately both methods eliminate the instability along with the problem of ill-posedness causing the model to undoubtedly lose some of its inherent dynamic capability. In this work, a one-dimensional two-fluid model for horizontal or slightly inclined stratified flow is developed. Higher order physical models that are often neglected, such as surface tension and axial viscous stress, are retained for their short-wavelength stability properties. Characteristic, dispersion and nonlinear analyses are performed to demonstrate that the resulting model is linearly well-posed and nonlinearly well-behaved. While it has been known that higher-order differential terms are able to regularize the short-wavelength problem of ill-posedness without removing the long-wavelength instability, the literature is relatively silent on the consequences of using a model under linearly unstable conditions. Using carefully selected conditions in an idealized infinite domain, it is demonstrated for the first time that the one-dimensional two-fluid model exhibits chaotic behavior in addition to limit cycles and asymptotic stability. The chaotic behavior is a consequence of the long-wavelength linear instability (energy source) the nonlinearity (energy transfer) and the short-wavelength dissipation (energy sink). Since the model is chaotic, solutions exhibit a sensitive dependence on initial
NASA Astrophysics Data System (ADS)
Mushtaq, A.; Abbasbandy, S.; Mustafa, M.; Hayat, T.; Alsaedi, A.
2016-01-01
Present work studies the well-known Sakiadis flow of Maxwell fluid along a moving plate in a calm fluid by considering the Cattaneo-Christov heat flux model. This recently developed model has the tendency to describe the characteristics of relaxation time for heat flux. Some numerical local similarity solutions of the associated problem are computed by two approaches namely (i) the shooting method and (ii) the Keller-box method. The solution is dependent on some interesting parameters which include the viscoelastic fluid parameter β, the dimensionless thermal relaxation time γ and the Prandtl number Pr. Our simulations indicate that variation in the temperature distribution with an increase in local Deborah number γ is non-monotonic. The results for the Fourier's heat conduction law can be obtained as special cases of the present study.
Rotational fluid flow experiment
NASA Technical Reports Server (NTRS)
1991-01-01
This project which began in 1986 as part of the Worcester Polytechnic Institute (WPI) Advanced Space Design Program focuses on the design and implementation of an electromechanical system for studying vortex behavior in a microgravity environment. Most of the existing equipment was revised and redesigned by this project team, as necessary. Emphasis was placed on documentation and integration of the electrical and mechanical subsystems. Project results include reconfiguration and thorough testing of all hardware subsystems, implementation of an infrared gas entrainment detector, new signal processing circuitry for the ultrasonic fluid circulation device, improved prototype interface circuits, and software for overall control of experiment operation.
A Mathematical Model for the Flow of a Casson Fluid due to Metachronal Beating of Cilia in a Tube
Siddiqui, A. M.; Farooq, A. A.; Rana, M. A.
2015-01-01
A mathematical model is developed to study the transport mechanism of a Casson fluid flow inspired by the metachronal coordination between the beating cilia in a cylindrical tube. A two-dimensional system of nonlinear equations governing the flow problem is formulated by using axisymmetric cylindrical coordinates and then simplified by employing the long wavelength and low Reynolds number assumptions. Exact solutions are derived for the velocity components, the axial pressure gradient, and the stream function. However, the expressions for the pressure rise and the volume flow rate are evaluated numerically. The features of the flow characteristics such as pumping and trapping are illustrated and discussed with the help of graphs. It is observed that the volume flow rate is influenced significantly by the width of plug flow region Hp as well as the cilia length parameter ε. The analysis is also applied and compared with the estimated value of the volume flow rate of epididymal fluid in the ductus efferentes of the human male reproductive tract. PMID:25789334
A mathematical model for the flow of a Casson fluid due to metachronal beating of cilia in a tube.
Siddiqui, A M; Farooq, A A; Rana, M A
2015-01-01
A mathematical model is developed to study the transport mechanism of a Casson fluid flow inspired by the metachronal coordination between the beating cilia in a cylindrical tube. A two-dimensional system of nonlinear equations governing the flow problem is formulated by using axisymmetric cylindrical coordinates and then simplified by employing the long wavelength and low Reynolds number assumptions. Exact solutions are derived for the velocity components, the axial pressure gradient, and the stream function. However, the expressions for the pressure rise and the volume flow rate are evaluated numerically. The features of the flow characteristics such as pumping and trapping are illustrated and discussed with the help of graphs. It is observed that the volume flow rate is influenced significantly by the width of plug flow region H p as well as the cilia length parameter ε. The analysis is also applied and compared with the estimated value of the volume flow rate of epididymal fluid in the ductus efferentes of the human male reproductive tract. PMID:25789334
NASA Astrophysics Data System (ADS)
Konar, D.
2015-09-01
The uses of ejector for efficient refrigeration are manifold - it has been used, among other applications, in the VCRS to reduce the compression ratio, in the combined ejector absorption cycle to enhance the refrigeration capacity and in the ejector absorber cycle to obtain lower evaporator pressures, higher absorber pressures and pre-absorption of the refrigerant in the ejector. Hence, modeling of flow which may be two phase two fluid as in ejector absorber cycle or two phase single fluid as in VCRS in an ejector assumes utmost importance. However, much work has not been done in this field. The primary objective of the present work is to discuss about the role of ejectors in various refrigeration systems and to model the two phase two fluid flow in the nozzle and the diffuser of an ejector under suitable assumptions. The equations of conservation of mass, momentum and energy have been solved to find the different flow properties like pressure, temperature and velocity of the two phases as function of the length in the diffuser. Different cases pertaining to different flows have been taken care of by appreciating what type of phenomena can actually occur at the interface of the two phases. Higher pressure rise was obtained for a given diffuser length with higher diffuser angles, smaller droplet diameter, higher inlet velocity of the gaseous phase and higher drag coefficients. Among other results, it was also seen that the two phases reached thermal equilibrium faster with higher diffuser angle, smaller droplet diameter and higher heat transfer coefficient.
A model for fluid flow during saturated boiling on a horizontal cylinder
NASA Technical Reports Server (NTRS)
Kheyrandish, K.; Dalton, C.; Lienhard, J. H.
1987-01-01
A model has been developed to represent the vapor removal pattern in the vicinity of a cylinder during nucleate flow boiling across a horizontal cylinder. The model is based on a potential flow representation of the liquid and vapor regions and an estimate of the losses that should occur in the flow. Correlation of the losses shows a weak dependence on the Weber number and a slightly stronger dependence on the saturated liquid-to-vapor density ratio. The vapor jet thickness, which is crucial to the prediction of the burnout heat flux, and the shape of the vapor film are predicted. Both are verified by qualitative experimental observations.
NASA Astrophysics Data System (ADS)
Ovaysi, S.; Piri, M.
2009-12-01
We present a three-dimensional fully dynamic parallel particle-based model for direct pore-level simulation of incompressible viscous fluid flow in disordered porous media. The model was developed from scratch and is capable of simulating flow directly in three-dimensional high-resolution microtomography images of naturally occurring or man-made porous systems. It reads the images as input where the position of the solid walls are given. The entire medium, i.e., solid and fluid, is then discretized using particles. The model is based on Moving Particle Semi-implicit (MPS) technique. We modify this technique in order to improve its stability. The model handles highly irregular fluid-solid boundaries effectively. It takes into account viscous pressure drop in addition to the gravity forces. It conserves mass and can automatically detect any false connectivity with fluid particles in the neighboring pores and throats. It includes a sophisticated algorithm to automatically split and merge particles to maintain hydraulic connectivity of extremely narrow conduits. Furthermore, it uses novel methods to handle particle inconsistencies and open boundaries. To handle the computational load, we present a fully parallel version of the model that runs on distributed memory computer clusters and exhibits excellent scalability. The model is used to simulate unsteady-state flow problems under different conditions starting from straight noncircular capillary tubes with different cross-sectional shapes, i.e., circular/elliptical, square/rectangular and triangular cross-sections. We compare the predicted dimensionless hydraulic conductances with the data available in the literature and observe an excellent agreement. We then test the scalability of our parallel model with two samples of an artificial sandstone, samples A and B, with different volumes and different distributions (non-uniform and uniform) of solid particles among the processors. An excellent linear scalability is
Two-fluid equilibrium with flow: FLOW2
Guazzotto, L.; Betti, R.
2015-09-15
The effects of finite macroscopic velocities on axisymmetric ideal equilibria are examined using the two-fluid (ions and electrons) model. A new equilibrium solver, the code FLOW2, is introduced for the two-fluid model and used to investigate the importance of various flow patterns on the equilibrium of tight aspect ratio (NSTX) and regular tokamak (DIII-D) configurations. Several improvements to the understanding and calculation of two-fluid equilibria are presented, including an analytical and numerical proof of the single-fluid and static limits of the two-fluid model, a discussion of boundary conditions, a user-friendly free-function formulation, and the explicit evaluation of velocity components normal to magnetic surfaces.
A non-Newtonian fluid model for blood flow through arteries under stenotic conditions.
Misra, J C; Patra, M K; Misra, S C
1993-09-01
This paper presents an analytical study on the behaviour of blood flow through an arterial segment having a mild stenosis. The artery has been treated as a thin-walled initially stressed orthotropic non-linear viscoelastic cylindrical tube filled with a non-Newtonian fluid representing blood. The analysis is restricted to propagation of small-amplitude harmonic waves, generated due to blood flow whose wave length is large compared to the radius of the arterial segment. For the equations of motion of the arterial wall consideration is made of a pair of appropriate equations derived by using suitable constitutive relations and the principle of superimposition of a small additional deformation on a state of known finite deformation. It has been shown through numerical computations of the resulting analytical expressions that the resistance to flow and the wall shear increase as the size of the stenosis increases. A quantitative analysis is also made for the frequency variation of the flow rate at different locations of the artery, as well as of the phase velocities and transmission per wavelength.
NASA Technical Reports Server (NTRS)
Wu, Jie; Yu, Sheng-Tao; Jiang, Bo-nan
1996-01-01
In this paper a numerical procedure for simulating two-fluid flows is presented. This procedure is based on the Volume of Fluid (VOF) method proposed by Hirt and Nichols and the continuum surface force (CSF) model developed by Brackbill, et al. In the VOF method fluids of different properties are identified through the use of a continuous field variable (color function). The color function assigns a unique constant (color) to each fluid. The interfaces between different fluids are distinct due to sharp gradients of the color function. The evolution of the interfaces is captured by solving the convective equation of the color function. The CSF model is used as a means to treat surface tension effect at the interfaces. Here a modified version of the CSF model, proposed by Jacqmin, is used to calculate the tension force. In the modified version, the force term is obtained by calculating the divergence of a stress tensor defined by the gradient of the color function. In its analytical form, this stress formulation is equivalent to the original CSF model. Numerically, however, the use of the stress formulation has some advantages over the original CSF model, as it bypasses the difficulty in approximating the curvatures of the interfaces. The least-squares finite element method (LSFEM) is used to discretize the governing equation systems. The LSFEM has proven to be effective in solving incompressible Navier-Stokes equations and pure convection equations, making it an ideal candidate for the present applications. The LSFEM handles all the equations in a unified manner without any additional special treatment such as upwinding or artificial dissipation. Various bench mark tests have been carried out for both two dimensional planar and axisymmetric flows, including a dam breaking, oscillating and stationary bubbles and a conical liquid sheet in a pressure swirl atomizer.
NASA Astrophysics Data System (ADS)
Ilyasov, A. M.; Bulgakova, G. T.
2016-08-01
This paper describes a mathematical model of the main fracture isolation in porous media by water-based mature gels. While modeling injection, water infiltration from the gel pack through fracture walls is taking into account, due to which the polymer concentration changes and the residual water resistance factor changes as a consequence. The salutation predicts velocity and pressure fields of the non-Newtonian incompressible fluid filtration for conditions of a non-deformable formation as well as a gel front trajectory in the fracture. The mathematical model of agent injection into the main fracture is based on the fundamental laws of continuum mechanics conservation describing the flow of non-Newtonian and Newtonian fluids separated by an interface plane in a flat channel with permeable walls. The mathematical model is based on a one-dimensional isothermal approximation, with dynamic parameters pressure and velocity, averaged over the fracture section.
On the hyperbolicity of a two-fluid model for debris flows
NASA Astrophysics Data System (ADS)
Mineo, C.; Torrisi, M.
2010-05-01
We consider the system of partial differential equations associated with the mathematical model for debris flows proposed by E.B. Pitman and L. Le (Phil. Trans. R. Soc. A, 363, 1573-1601, 2005) and analyze the problem of the hyperbolicity of the model.
Fluid/structure interactions. Internal flows
NASA Astrophysics Data System (ADS)
Weaver, D. S.
1991-05-01
Flow-induced vibrations are found wherever structures are exposed to high velocity fluid flows. Internal flows are usually characterized by the close proximity of solid boundaries. There are surfaces against which separated flows may reattach, or from which pressure disturbances may be reflected resulting in acoustic resonance. When the fluid is a liquid, the close proximity of solid boundaries to a vibrating component can produce very high added mass effects. This paper presents three different experimental studies of flow-induced vibration problems associated with internal flows. The emphasis was on experimental techniques developed for understanding excitation mechanisms. In difficult flow-induced vibration problems, a useful experimental technique is flow visualization using a large scale model and strobe light triggered by the phenomenon being observed. This should be supported by point measurements of velocity and frequency spectra. When the flow excitation is associated with acoustic resonance, the sound can be fed back to enhance or eliminate the instability. This is potentially a very useful tool for studying and controlling fluid-structure interaction problems. Some flow-induced vibration problems involve a number of different excitation mechanisms and care must be taken to ensure that the mechanisms are properly identified. Artificially imposing structural vibrations or acoustic fields may induce flow structures not naturally present in the system.
Boutchko, Rostyslav; Rayz, Vitaliy L.; Vandehey, Nicholas T.; O’Neil, James P.; Budinger, Thomas F.; Nico, Peter S.; Druhan, Jennifer L.; Saloner, David A.; Gullberg, Grant T.; Moses, William W.
2014-01-01
This paper presents experimental and modeling aspects of applying nuclear emission tomography to study fluid flow in laboratory packed porous media columns of the type frequently used in geophysics, geochemistry and hydrology research. Positron emission tomography (PET) and single photon emission computed tomography (SPECT) are used as non-invasive tools to obtain dynamic 3D images of radioactive tracer concentrations. Dynamic sequences obtained using 18F-FDG PET are used to trace flow through a 5 cm diameter × 20 cm tall sand packed column with and without an impermeable obstacle. In addition, a custom-made rotating column setup placed in a clinical two-headed SPECT camera is used to image 99mTc-DTPA tracer propagation in a through-flowing column (10 cm diameter × 30 cm tall) packed with recovered aquifer sediments. A computational fluid dynamics software package FLUENT is used to model the observed flow dynamics. Tracer distributions obtained in the simulations in the smaller column uniformly packed with sand and in the column with an obstacle are remarkably similar to the reconstructed images in the PET experiments. SPECT results demonstrate strongly non-uniform flow patterns for the larger column slurry-packed with sub-surface sediment and slow upward flow. In the numerical simulation of the SPECT study, two symmetric channels with increased permeability are prescribed along the column walls, which result in the emergence of two well-defined preferential flow paths. Methods and results of this work provide new opportunities in hydrologic and biogeochemical research. The primary target application for developed technologies is non-destructive, non-perturbing, quantitative imaging of flow dynamics within laboratory scale porous media systems. PMID:24917693
Experimental and numerical modelling of the fluid flow in the continuous casting of steel
NASA Astrophysics Data System (ADS)
Timmel, K.; Miao, X.; Wondrak, T.; Stefani, F.; Lucas, D.; Eckert, S.; Gerbeth, G.
2013-03-01
This article gives an overview of recent research activities with respect to the mold flow in the continuous casting of steel in presence of DC magnetic fields. The magnetic fields appear to be an attractive tool for controlling the melt flow in a contactless way. Various kinds of magnetic systems are already in operation in industrial steel casting, but the actual impact on the melt flow has not been sufficiently verified by experimental studies. The rapid development of innovative diagnostic techniques in low-melting liquid metals over the last two decades enables new possibilities for systematic flow measurements in liquid metal model experiments. A new research program was initiated at HZDR comprising three experimental facilities providing a LIquid Metal Model for continuous CASTing of steel (LIMMCAST). The facilities operate in a temperature range from room temperature up to 400∘C using the low-melting alloys GaInSn and SnBi, respectively. The experimental program is focused on quantitative flow measurements in the mold, the submerged entry nozzle and the tundish. Local potential probes, Ultrasonic Doppler Velocimetry (UDV) and Contactless Inductive Flow Tomography (CIFT) are employed to measure the melt flow. The behavior of two-phase flows in case of argon injection is investigated by means of the Mutual Inductance Tomography (MIT) and X-ray radioscopy. The experimental results provide a substantial data basis for the validation of related numerical simulations. Numerical calculations were performed with the software package ANSYS-CFX with an implemented RANS-SST turbulence model. The non-isotropic nature of MHD turbulence was taken into account by specific modifications of the turbulence model. First results of the LIMMCAST program reveal important findings such as the peculiar, unexpected phenomenon that the application of a DC magnetic field may excite non-steady, non-isotropic large-scale flow oscillations in the mold. Another important result of our
Verification of mesoscopic models of viscoelastic fluids with a non-monotonic flow curve
NASA Astrophysics Data System (ADS)
Kuznetsova, Julia L.; Skul'skiy, Oleg I.
2016-02-01
The non-monotonic flow curve of a 1 wt.% polyacrylonitrile solution in dimethyl sulfoxide is described by two mesoscopic models: the modified Vinogradov-Pokrovsky model and the model proposed by Remmelgas, Harrison and Leal. To obtain an adequate description of the experimental curve, we have selected suitable internal parameters for these models. Analytical solutions for the Couette-Poiseuille flow problems are determined in parametric form, which allows us to plot the distribution of stress components and anisotropy tensor as well as the velocity profiles containing closed loops and weak tangential discontinuities. It is shown that both models predict a similar qualitative picture of structure evolution, but exhibit a significant discrepancy in the quantitative description of the magnitude of molecular chain stretching.
Guidelines in the experimental validation of a 3D heat and fluid flow model of keyhole laser welding
NASA Astrophysics Data System (ADS)
Courtois, Mickael; Carin, Muriel; Le Masson, Philippe; Gaied, Sadok; Balabane, Mikhaël
2016-04-01
During the past few years, numerous sophisticated models have been proposed to predict in a self-consistent way the dynamics of the keyhole, together with the melt pool and vapor jet. However, these models are only partially compared to experimental data, so the reliability of these models is questionable. The present paper aims to propose a more complete experimental set-up in order to validate the most relevant results calculated by these models. A complete heat transfer and fluid flow three-dimensional (3D) model is first proposed in order to describe laser welding in keyhole regimes. The interface is tracked with a level set method and fluid flows are calculated in liquid and gas. The mechanisms of recoil pressure and keyhole creation are highlighted in a fusion line configuration chosen as a reference. Moreover, a complete validation of the model is proposed with guidelines on the variables to observe. Numerous comparisons with dedicated experiments (thermocouples, pyrometry, high-speed camera) are proposed to estimate the validity of the model. In addition to traditional geometric measurements, the main variables calculated, temperatures, and velocities in the melt pool are at the center of this work. The goal is to propose a reference validation for complex 3D models proposed over the last few years.
Widmer Soyka, René P; López, Alejandro; Persson, Cecilia; Cristofolini, Luca; Ferguson, Stephen J
2013-11-01
Fluids present or used in biology, medicine and (biomedical) engineering are often significantly non-Newtonian. Furthermore, they are chemically complex and can interact with the porous matrix through which they flow. The porous structures themselves display complex morphological inhomogeneities on a wide range of length scales. In vertebroplasty, a shear-thinning fluid, e.g. poly(methyl methacrylate) (PMMA), is injected into the cavities of vertebral trabecular bone for the stabilization of fractures and metastatic lesions. The main objective of this study was therefore to provide a protocol for numerically investigating the rheological properties of PMMA-based bone cements to predict its spreading behavior while flowing through vertebral trabecular bone. A numerical upscaling scheme based on a dimensionless formulation of the Navier-Stokes equation is proposed in order to relate the pore-scale rheological properties of the PMMA that were experimentally estimated using a plate rheometer, to the continuum-scale. On the pore length scale, a viscosity change on the order of one magnitude was observed whilst the shear-thinning properties caused a viscosity change on the order of only 10% on the continuum length scale and in a flow regime that is relevant for vertebroplasty. An experimental validation, performed on human cadaveric vertebrae (n=9), showed a significant improvement of the cement spreading prediction accuracy with a non-Newtonian formulation. A root mean square cement surface prediction error of 1.53mm (assuming a Newtonian fluid) and 1.37mm (assuming a shear-thinning fluid) was found. Our findings highlight the importance of incorporating the non-Newtonian fluids properties in computational models of porous media at the appropriate length scale. PMID:23867293
Widmer Soyka, René P; López, Alejandro; Persson, Cecilia; Cristofolini, Luca; Ferguson, Stephen J
2013-11-01
Fluids present or used in biology, medicine and (biomedical) engineering are often significantly non-Newtonian. Furthermore, they are chemically complex and can interact with the porous matrix through which they flow. The porous structures themselves display complex morphological inhomogeneities on a wide range of length scales. In vertebroplasty, a shear-thinning fluid, e.g. poly(methyl methacrylate) (PMMA), is injected into the cavities of vertebral trabecular bone for the stabilization of fractures and metastatic lesions. The main objective of this study was therefore to provide a protocol for numerically investigating the rheological properties of PMMA-based bone cements to predict its spreading behavior while flowing through vertebral trabecular bone. A numerical upscaling scheme based on a dimensionless formulation of the Navier-Stokes equation is proposed in order to relate the pore-scale rheological properties of the PMMA that were experimentally estimated using a plate rheometer, to the continuum-scale. On the pore length scale, a viscosity change on the order of one magnitude was observed whilst the shear-thinning properties caused a viscosity change on the order of only 10% on the continuum length scale and in a flow regime that is relevant for vertebroplasty. An experimental validation, performed on human cadaveric vertebrae (n=9), showed a significant improvement of the cement spreading prediction accuracy with a non-Newtonian formulation. A root mean square cement surface prediction error of 1.53mm (assuming a Newtonian fluid) and 1.37mm (assuming a shear-thinning fluid) was found. Our findings highlight the importance of incorporating the non-Newtonian fluids properties in computational models of porous media at the appropriate length scale.
Nanometer-scale imaging and pore-scale fluid flow modeling inchalk
Tomutsa, Liviu; Silin, Dmitriy; Radmilovich, Velimir
2005-08-23
For many rocks of high economic interest such as chalk,diatomite, tight gas sands or coal, nanometer scale resolution is neededto resolve the 3D-pore structure, which controls the flow and trapping offluids in the rocks. Such resolutions cannot be achieved with existingtomographic technologies. A new 3D imaging method, based on serialsectioning and using the Focused Ion Beam (FIB) technology has beendeveloped. FIB allows for the milling of layers as thin as 10 nanometersby using accelerated Ga+ ions to sputter atoms from the sample surface.After each milling step, as a new surface is exposed, a 2D image of thissurface is generated. Next, the 2D images are stacked to reconstruct the3D pore or grain structure. Resolutions as high as 10 nm are achievableusing this technique. A new image processing method uses directmorphological analysis of the pore space to characterize thepetrophysical properties of diverse formations. In addition to estimationof the petrophysical properties (porosity, permeability, relativepermeability and capillary pressures), the method is used for simulationof fluid displacement processes, such as those encountered in variousimproved oil recovery (IOR) approaches. Computed with the new methodcapillary pressure curves are in good agreement with laboratory data. Themethod has also been applied for visualization of the fluid distributionat various saturations from the new FIB data.
NASA Astrophysics Data System (ADS)
Jacobs, C. T.; Piggott, M. D.
2015-03-01
This model description paper introduces a new finite element model for the simulation of non-linear shallow water flows, called Firedrake-Fluids. Unlike traditional models that are written by hand in static, low-level programming languages such as Fortran or C, Firedrake-Fluids uses the Firedrake framework to automatically generate the model's code from a high-level abstract language called Unified Form Language (UFL). By coupling to the PyOP2 parallel unstructured mesh framework, Firedrake can then target the code towards a desired hardware architecture to enable the efficient parallel execution of the model over an arbitrary computational mesh. The description of the model includes the governing equations, the methods employed to discretise and solve the governing equations, and an outline of the automated solution process. The verification and validation of the model, performed using a set of well-defined test cases, is also presented along with a road map for future developments and the solution of more complex fluid dynamical systems.
Viscoelastic flow modeling in the extrusion of a dough-like fluid
NASA Technical Reports Server (NTRS)
Dhanasekharan, M.; Kokini, J. L.; Janes, H. W. (Principal Investigator)
2000-01-01
This work attempts to investigate the effect of viscoelasticity and three-dimensional geometry in screw channels. The Phan-Thien Tanner (PTT) constitutive equation with simplified model parameters was solved in conjunction with the flow equations. Polyflow, a commercially available finite element code was used to solve the resulting nonlinear partial differential equations. The PTT model predicted one log scale lower pressure buildup compared to the equivalent Newtonian results. However, the velocity profile did not show significant changes for the chosen PTT model parameters. Past Researchers neglected viscoelastic effects and also the three dimensional nature of the flow in extruder channels. The results of this paper provide a starting point for further simulations using more realistic model parameters, which may enable the food engineer to more accurately scale-up and design extrusion processes.
Viscoelastic flow modeling in the extrusion of a dough-like fluid.
Dhanasekharan, M; Kokini, J L
2000-08-01
This work attempts to investigate the effect of viscoelasticity and three-dimensional geometry in screw channels. The Phan-Thien Tanner (PTT) constitutive equation with simplified model parameters was solved in conjunction with the flow equations. Polyflow, a commercially available finite element code was used to solve the resulting nonlinear partial differential equations. The PTT model predicted one log scale lower pressure buildup compared to the equivalent Newtonian results. However, the velocity profile did not show significant changes for the chosen PTT model parameters. Past Researchers neglected viscoelastic effects and also the three dimensional nature of the flow in extruder channels. The results of this paper provide a starting point for further simulations using more realistic model parameters, which may enable the food engineer to more accurately scale-up and design extrusion processes.
NASA Technical Reports Server (NTRS)
Makuch, Lauren A.
2004-01-01
Humans reach peak bone mass at age 30. After this point, we lose 1 to 2 percent of bone mass each decade. In the microgravity environment of space, astronauts lose bone mass at an accelerated rate of 1 to 2 percent each month. When astronauts travel to Mars, they may be in space for as long as 3 years. During this time, they may lose about half of their bone mass from weight-bearing bones. This loss may be irreversible. The drastic loss in bone that astronauts experience in space makes them much more vulnerable to fractures. In addition, the corresponding removal of calcium from bone results in higher levels of calcium in the blood, which increases the risk of developing kidney stones. Currently, studies are being conducted which investigate factors governing bone adaptation and mechanotransduction. Bone is constantly adapting in response to mechanical stimuli. Increased mechanical loading stimulates bone formation and suppresses bone resorption. Reduction in mechanical loading caused by bedrest, disuse, or microgravity results in decreased bone formation and possibly increased bone resorption. Osteoblasts and osteoclasts are the two main cell types that participate in bone remodeling. Osteoblasts are anabolic (bone-forming) cells and osteoclasts are catabolic (bone-resorbing) cells. In microgravity, the activity of osteoblasts slows down and the activity of osteoclasts may speed up, causing a loss of bone density. Mechanotransduction, the molecular mechanism by which mechanical stimuli are converted to biochemical signals, is not yet understood. Exposure of cells to fluid flow imposes a shear stress on the cells. Several studies have shown that the shear stress that results from fluid flow induces a cellular response similar to that induced by mechanical loading. Thus, fluid flow can be used as an in vitro model to simulate the mechanical stress that bone cells experience in vivo. Previous in vitro studies have shown that fluid flow induces several responses in
Rubab, Khansa; Mustafa, M.
2016-01-01
This letter investigates the MHD three-dimensional flow of upper-convected Maxwell (UCM) fluid over a bi-directional stretching surface by considering the Cattaneo-Christov heat flux model. This model has tendency to capture the characteristics of thermal relaxation time. The governing partial differential equations even after employing the boundary layer approximations are non linear. Accurate analytic solutions for velocity and temperature distributions are computed through well-known homotopy analysis method (HAM). It is noticed that velocity decreases and temperature rises when stronger magnetic field strength is accounted. Penetration depth of temperature is a decreasing function of thermal relaxation time. The analysis for classical Fourier heat conduction law can be obtained as a special case of the present work. To our knowledge, the Cattaneo-Christov heat flux model law for three-dimensional viscoelastic flow problem is just introduced here. PMID:27093542
Rubab, Khansa; Mustafa, M
2016-01-01
This letter investigates the MHD three-dimensional flow of upper-convected Maxwell (UCM) fluid over a bi-directional stretching surface by considering the Cattaneo-Christov heat flux model. This model has tendency to capture the characteristics of thermal relaxation time. The governing partial differential equations even after employing the boundary layer approximations are non linear. Accurate analytic solutions for velocity and temperature distributions are computed through well-known homotopy analysis method (HAM). It is noticed that velocity decreases and temperature rises when stronger magnetic field strength is accounted. Penetration depth of temperature is a decreasing function of thermal relaxation time. The analysis for classical Fourier heat conduction law can be obtained as a special case of the present work. To our knowledge, the Cattaneo-Christov heat flux model law for three-dimensional viscoelastic flow problem is just introduced here. PMID:27093542
Faybishenko, Boris; Doughty, Christine; Stoops, Thomas M.; Wood, thomas R.; Wheatcraft, Stephen W.
1999-12-31
(1) To determine if and when dynamical chaos theory can be used to investigate infiltration of fluid and contaminant transport in heterogeneous soils and fractured rocks. (2) To introduce a new approach to the multiscale characterization of flow and transport in fractured basalt vadose zones and to develop physically based conceptual models on a hierarchy of scales. The following activities are indicative of the success in meeting the project s objectives: A series of ponded infiltration tests, including (1) small-scale infiltration tests (ponded area 0.5 m2) conducted at the Hell s Half Acre site near Shelley, Idaho, and (2) intermediate-scale infiltration tests (ponded area 56 m2) conducted at the Box Canyon site near Arco, Idaho. Laboratory investigations and modeling of flow in a fractured basalt core. A series of small-scale dripping experiments in fracture models. Evaluation of chaotic behavior of flow in laboratory and field experiments using methods from nonlinear dynamics; Evaluation of the impact these dynamics may have on contaminant transport through heterogeneous fractured rocks and soils, and how it can be used to guide remediation efforts; Development of a conceptual model and mathematical and numerical algorithms for flow and transport that incorporate (1) the spatial variability of heterogeneous porous and fractured media, and (2) the description of the temporal dynamics of flow and transport, both of which may be chaotic. Development of appropriate experimental field and laboratory techniques needed to detect diagnostic parameters for chaotic behavior of flow. This approach is based on the assumption that spatial heterogeneity and flow phenomena are affected by nonlinear dynamics, and in particular, by chaotic processes. The scientific and practical value of this approach is that we can predict the range within which the parameters of flow and transport change with time in order to design and manage the remediation, even when we can not predict
Shen, Binglin; Pan, Bailiang; Jiao, Jian; Xia, Chunsheng
2015-07-27
Comprehensive analysis of kinetic and fluid dynamic processes in flowing-gas diode-pumped alkali vapor amplifiers is reported. Taking into account effects of the temperature, the amplified spontaneous emission, the saturation power, the excitation of the alkali atoms to high electronic levels and the ionization, a detailed physical model is established to simulate the output performance of flowing-gas diode-pumped alkali vapor amplifiers. Influences of the flow velocity and the pump power on the amplified power are calculated and analyzed. Comparisons between single and double amplifier, longitudinal and transverse flow are made. Results show that end-pumped cascaded amplifier can provide higher output power under the same total pump power and the cell length, while output powers achieved by single- and double-end pumped, double-side pumped amplifiers with longitudinal or transverse flow have a complicated but valuable relation. Thus the model is extremely helpful for designing high-power flowing-gas diode-pumped alkali vapor amplifiers.
Numerical Model of Fluid Flow through Heterogeneous Rock for High Level Radioactive Waste Disposal
NASA Astrophysics Data System (ADS)
Shirai, M.; Chiba, R.; Fomin, S.; Chugunov, V.; Takahashi, T.; Niibori, Y.; Hashida, T.
2007-03-01
An international consensus has emerged that deep geological disposal on land is one of the most appropriate means for high level radioactive wastes (HLW). The fluid transport is slow and radioactive elements are dangerous, so it's impossible to experiment over thousands of years. Instead, numerical model in such natural barrier as fractured underground needs to be considered. Field observations reveal that the equation with fractional derivative is more appropriate for describing physical phenomena than the equation which is based on the Fick's law. Thus, non-Fickian diffusion into inhomogeneous underground appears to be important in the assessment of HLW disposal. A solute transport equation with fractional derivative has been suggested and discussed in literature. However, no attempts were made to apply this equation for modeling of HLW disposal with account for the radioactive decay. In this study, we suggest the use of a novel fractional advection-diffusion equation which accounts for the effect of radioactive disintegration and for interactions between major, macro pores and fractal micro pores. This model is fundamentally different from previous proposed model of HLW, particularly in utilizing fractional derivative. Breakthrough curves numerically obtained by the present model are presented for a variety of rock types with respect to some important nuclides. Results of the calculation showed that for longer distance our model tends to be more conservative than the conventional Fickian model, therefore our model can be said to be safer.
NASA Astrophysics Data System (ADS)
Chitta, Varun
Modeling of complex flows involving the combined effects of flow transition and streamline curvature using two advanced turbulence models, one in the Reynolds-averaged Navier-Stokes (RANS) category and the other in the hybrid RANS-Large eddy simulation (LES) category is considered in this research effort. In the first part of the research, a new scalar eddy-viscosity model (EVM) is proposed, designed to exhibit physically correct responses to flow transition, streamline curvature, and system rotation effects. The four equation model developed herein is a curvature-sensitized version of a commercially available three-equation transition-sensitive model. The physical effects of rotation and curvature (RC) enter the model through the added transport equation, analogous to a transverse turbulent velocity scale. The eddy-viscosity has been redefined such that the proposed model is constrained to reduce to the original transition-sensitive model definition in nonrotating flows or in regions with negligible RC effects. In the second part of the research, the developed four-equation model is combined with a LES technique using a new hybrid modeling framework, dynamic hybrid RANS-LES. The new framework is highly generalized, allowing coupling of any desired LES model with any given RANS model and addresses several deficiencies inherent in most current hybrid models. In the present research effort, the DHRL model comprises of the proposed four-equation model for RANS component and the MILES scheme for LES component. Both the models were implemented into a commercial computational fluid dynamics (CFD) solver and tested on a number of engineering and generic flow problems. Results from both the RANS and hybrid models show successful resolution of the combined effects of transition and curvature with reasonable engineering accuracy, and for only a small increase in computational cost. In addition, results from the hybrid model indicate significant levels of turbulent
Fluid dynamic modeling and numerical simulation of low-density hypersonic flow
NASA Technical Reports Server (NTRS)
Cheng, H. K.; Wong, Eric Y.
1988-01-01
The concept of a viscous shock-layer and several related versions of continuum theories/methods are examined for their adequacy as a viable framework to study flow physics and aerothermodynamics of relevance to sustained hypersonic flights. Considering the flat plate at angle of attack, or the wedge, as a generic example for the major aerodynamic component of a hypersonic vehicle, the relative importance of the molecular-transport effects behind the shock (in the form of the 'shock slip') and the wall-slip effects are studied. In the flow regime where the shock-transition-zone thickness remains small compared to the shock radius of curvature, a quasi-one-dimensional shock structure under the Burnett/thirteen-moment approximation, as well as particulate/collisional models, can be consistently developed. The fully viscous version of the shock-layer model is shown to provide the crucial boundary condition downstream the shock in this case. The gas-kinetic basis of the continuum description for the flow behind the bow shock, and certain features affecting the non-equilibrium flow chemistry, are also discussed.
Fluid dynamic modeling and numerical simulation of low-density hypersonic flow
NASA Astrophysics Data System (ADS)
Cheng, H. K.; Wong, Eric Y.
1988-06-01
The concept of a viscous shock-layer and several related versions of continuum theories/methods are examined for their adequacy as a viable framework to study flow physics and aerothermodynamics of relevance to sustained hypersonic flights. Considering the flat plate at angle of attack, or the wedge, as a generic example for the major aerodynamic component of a hypersonic vehicle, the relative importance of the molecular-transport effects behind the shock (in the form of the 'shock slip') and the wall-slip effects are studied. In the flow regime where the shock-transition-zone thickness remains small compared to the shock radius of curvature, a quasi-one-dimensional shock structure under the Burnett/thirteen-moment approximation, as well as particulate/collisional models, can be consistently developed. The fully viscous version of the shock-layer model is shown to provide the crucial boundary condition downstream the shock in this case. The gas-kinetic basis of the continuum description for the flow behind the bow shock, and certain features affecting the non-equilibrium flow chemistry, are also discussed.
Geophysical Fluid Flow Cell (GFFC) Simulation
NASA Technical Reports Server (NTRS)
1999-01-01
These simulations of atmospheric flow use the same experimental parameters but started with slightly different initial conditions in the model. The simulations were part of data analysis for the Geophysical Fluid Flow Cell (GFFC), a planet in a test tube apparatus flown on Spacelab to mimic the atmospheres on gas giant planets and stars. (Credit: Dr. Tim Miller of Global Hydrology and Climate Center at the Marshall Space Flight Center)
NASA Technical Reports Server (NTRS)
Habbal, Shadia Rifai; Esser, Ruth; Guhathakurta, Madhulika; Fisher, Richard
1995-01-01
Using the empirical constraints provided by observations in the inner corona and in interplanetary space. we derive the flow properties of the solar wind using a two fluid model. Density and scale height temperatures are derived from White Light coronagraph observations on SPARTAN 201-1 and at Mauna Loa, from 1.16 to 5.5 R, in the two polar coronal holes on 11-12 Apr. 1993. Interplanetary measurements of the flow speed and proton mass flux are taken from the Ulysses south polar passage. By comparing the results of the model computations that fit the empirical constraints in the two coronal hole regions, we show how the effects of the line of sight influence the empirical inferences and subsequently the corresponding numerical results.
Gao, Feng; Ueda, Hiroshi; Gang, Li; Okada, Hiroshi
2013-04-26
One treatment method for aortic aneurysm is the invasive insertion of a stent into the aneurysm. Another method is wrapping the aneurysm using newly developed expanded polytetrafluoroethylene (PTFE) material. A virtual stented aneurysm model and a wrapped aneurysm model were created to study the flow and wall dynamics by means of fluid-structure interaction analyses. The flow velocity and pressure distribution as well as the deformation and wall stress were investigated. Stenting significantly changed the blood flow pattern and the vortexes in the aneurysm. Wrapping increased the thickness of the aneurysm wall and increased the strength of the vessel wall. The maximum von Mises stress in the stented model was found to be 220,494 Pa and 228,218 Pa at the time of peak flow and peak pressure, respectively. This was reduced by 37.8% and 36.7% to 137,200 and 144,354 Pa, respectively, in the wrapped model. Our results provide information that may improve the understanding of the biomechanics of stenting and wrapping. PMID:23477789
Gao, Feng; Ueda, Hiroshi; Gang, Li; Okada, Hiroshi
2013-04-26
One treatment method for aortic aneurysm is the invasive insertion of a stent into the aneurysm. Another method is wrapping the aneurysm using newly developed expanded polytetrafluoroethylene (PTFE) material. A virtual stented aneurysm model and a wrapped aneurysm model were created to study the flow and wall dynamics by means of fluid-structure interaction analyses. The flow velocity and pressure distribution as well as the deformation and wall stress were investigated. Stenting significantly changed the blood flow pattern and the vortexes in the aneurysm. Wrapping increased the thickness of the aneurysm wall and increased the strength of the vessel wall. The maximum von Mises stress in the stented model was found to be 220,494 Pa and 228,218 Pa at the time of peak flow and peak pressure, respectively. This was reduced by 37.8% and 36.7% to 137,200 and 144,354 Pa, respectively, in the wrapped model. Our results provide information that may improve the understanding of the biomechanics of stenting and wrapping.
NASA Astrophysics Data System (ADS)
Raziperchikolaee, S.; Alvarado, V.; Yin, S.
2014-09-01
Studying rock joint deformation including both slippage and opening mechanisms provides an opportunity to investigate the connection between the permeability and seismic source mechanisms. A microscale fluid flow-geomechanics-seismicity model was built to evaluate the transport response and failure mechanism of microcracks developed along a joint in Berea sandstone samples during deformation. The modeling method considers comprehensive grain-cement interactions. Fluid flow behavior is obtained through a realistic network model of the pore space in the compacted assembly. The geometric description of the complex pore structure is characterized to predict permeability of the rock sample as a function of rock deformation by using a dynamic pore network model. As a result of microcracks development, forces and displacements in grains involved in bond breakage are measured to determine seismic moment tensor. Shear and nonshear displacements are applied to the joint samples to investigate their effects on permeability evolution and failure mechanism of microcracks during joint deformation. In addition, the effect of joint roughness is analyzed by performing numerical compression tests. We also investigate how confining pressure affects volumetric deformation leading to opening or closure of developed microcracks and permeability changes of samples with joints.
Ferroelectric Fluid Flow Control Valve
NASA Technical Reports Server (NTRS)
Jalink, Antony, Jr. (Inventor); Hellbaum, Richard F. (Inventor); Rohrbach, Wayne W. (Inventor)
1999-01-01
An active valve is controlled and driven by external electrical actuation of a ferroelectric actuator to provide for improved passage of the fluid during certain time periods and to provide positive closure of the valve during other time periods. The valve provides improved passage in the direction of flow and positive closure in the direction against the flow. The actuator is a dome shaped internally prestressed ferroelectric actuator having a curvature, said dome shaped actuator having a rim and an apex. and a dome height measured from a plane through said rim said apex that varies with an electric voltage applied between an inside and an outside surface of said dome shaped actuator.
Fluid flow electrophoresis in space
NASA Technical Reports Server (NTRS)
Griffin, R. N.
1975-01-01
Four areas relating to free-flow electrophoresis in space were investigated. The first was the degree of improvement over earthbound operations that might be expected. The second area of investigation covered the problems in developing a flowing buffer electrophoresis apparatus. The third area of investigation was the problem of testing on the ground equipment designed for use in space. The fourth area of investigation was the improvement to be expected in space for purification of biologicals. The results of some ground-based experiments are described. Other studies included cooling requirements in space, fluid sealing techniques, and measurement of voltage drop across membranes.
General Transient Fluid Flow Algorithm
1992-03-12
SALE2D calculates two-dimensional fluid flows at all speeds, from the incompressible limit to highly supersonic. An implicit treatment of the pressure calculation similar to that in the Implicit Continuous-fluid Eulerian (ICE) technique provides this flow speed flexibility. In addition, the computing mesh may move with the fluid in a typical Lagrangian fashion, be held fixed in an Eulerian manner, or move in some arbitrarily specified way to provide a continuous rezoning capability. This latitude resultsmore » from use of an Arbitrary Lagrangian-Eulerian (ALE) treatment of the mesh. The partial differential equations solved are the Navier-Stokes equations and the mass and internal energy equations. The fluid pressure is determined from an equation of state and supplemented with an artificial viscous pressure for the computation of shock waves. The computing mesh consists of a two-dimensional network of quadrilateral cells for either cylindrical or Cartesian coordinates, and a variety of user-selectable boundary conditions are provided in the program.« less
NASA Astrophysics Data System (ADS)
Denisenko, N. S.; Chupakhin, A. P.; Khe, A. K.; Cherevko, A. A.; Yanchenko, A. A.; Tulupov, A. A.; Boiko, A. V.; Krivoshapkin, A. L.; Orlov, K. Yu; Moshkin, M. P.; Akulov, A. E.
2016-06-01
In our experiments, we investigate a flow of a viscous fluid in the model of the common carotid artery bifurcation. The studies are carried out using three hardware equipments: two magnetic resonance scanners by Philips and Bruker, and intravascular guidewire ComboWire. The flux is generated by a special pump CompuFlow that is designed to reproduce a flow similar to the one in the blood vessels. A verification of the obtained data is carried out. Conducted research shows the capabilities of the measurement instruments and reflects the character of fluid flow inside the model.
NASA Astrophysics Data System (ADS)
Taheri, Mehrdad
In this thesis analytical and numerical investigations of fluid flow and heat transfer through open cell metal foam heat exchangers are presented. Primarily, different representative unit cell approximations, i.e, tetrakaidecahedron, dodecahedron and cubic are discussed. By applying the thermal resistance analogy, a novel formulation for evaluation of the effective thermal conductivity of metal foams is proposed. The model improves previous models based on cubic or hexagonal cells. By using computer tomography images of a nickel foam sample a realistic 3D geometry is created and the foam's geometrical properties (i.e., porosity and surface area to volume ratio) and effective thermal conductivity are obtained. By using the experimentally found values of permeability, Forchheimer coefficient and solid-fluid interfacial convection coefficient, mathematical models for fluid flow and heat transfer in metal foams are developed. Two different assumptions: local thermal equilibrium (LTE) and local thermal non-equilibrium (LTNE), are used. LTNE yields more accurate results. A three-dimensional computational fluid dynamics (CFD) model of metal foam is made and validated against the experimental data for a square cross sectional nickel foam heat exchanger channel heated from the side walls while cooling air passes through the foam. The simulations are carried out for constant temperature or heat flux and different foam materials with pore densities of 10 and 40 pores per inch. The results show that the bonding of the foam to the walls has a considerable impact on the heat transfer rate. Convective heat transfer coefficients in terms of Nusselt number as functions of Reynolds number are also obtained. The design and CFD modeling of metal foam cross flow heat exchangers are also discussed. The results indicate both effectiveness and number of transfer units (NTU) for the metal foam heat exchangers are higher than those of a hollow channel; however, the effectiveness-NTU curves
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
NASA Astrophysics Data System (ADS)
Khoei, A. R.; Hosseini, N.; Mohammadnejad, T.
2016-08-01
In the present paper, a numerical model is developed based on a combination of the extended finite element method and an equivalent continuum model to simulate the two-phase fluid flow through fractured porous media containing fractures with multiple length scales. The governing equations involve the linear momentum balance equation and the flow continuity equation for each fluid phase. The extended finite element method allows for an explicit and accurate representation of cracks by enriching the standard finite element approximation of the field variables with appropriate enrichment functions, and captures the mass transfer between the fracture and the matrix. Due to the high computational cost of X-FEM, this technique is only used to model large fractures. The pre-existing short fractures, which are distributed randomly in the porous medium, contribute to the increase of the effective permeability tensor and are modeled with an equivalent continuum model. Finally, the robustness of the proposed computational model is demonstrated through several numerical examples, and the effects of crack orientation, capillary pressure function, solid skeleton deformation, and existence of short cracks on the pattern of fluid flow are investigated. It is shown that the developed model provides a correct prediction of flow pattern for different crack configurations.
INGBER,M.S.; SUBIA,SAMUEL R.; MONDY,LISA ANN
2000-01-18
The analysis of many complex multiphase fluid flow systems is based on a scale decoupling procedure. At the macroscale continuum models are used to perform large-scale simulations. At the mesoscale statistical homogenization theory is used to derive continuum models based on representative volume elements (RVEs). At the microscale small-scale features, such as interfacial properties, are analyzed to be incorporated into mesoscale simulations. In this research mesoscopic simulations of hard particles suspended in a Newtonian fluid undergoing nonlinear shear flow are performed using a boundary element method. To obtain an RVE at higher concentrations, several hundred particles are included in the simulations, putting considerable demands on the computational resources both in terms of CPU and memory. Parallel computing provides a viable platform to study these large multiphase systems. The implementation of a portable, parallel computer code based on the boundary element method using a block-block data distribution is discussed in this paper. The code employs updated direct-solver technologies that make use of dual-processor compute nodes.
NASA Astrophysics Data System (ADS)
Hu, Mengsu; Rutqvist, Jonny; Wang, Yuan
2016-11-01
In this study, a numerical manifold method (NMM) model is developed to analyze flow in porous media with discrete fractures in a non-conforming mesh. This new model is based on a two-cover-mesh system with a uniform triangular mathematical mesh and boundary/fracture-divided physical covers, where local independent cover functions are defined. The overlapping parts of the physical covers are elements where the global approximation is defined by the weighted average of the physical cover functions. The mesh is generated by a tree-cutting algorithm. A new model that does not introduce additional degrees of freedom (DOF) for fractures was developed for fluid flow in fractures. The fracture surfaces that belong to different physical covers are used to represent fracture flow in the direction of the fractures. In the direction normal to the fractures, the fracture surfaces are regarded as Dirichlet boundaries to exchange fluxes with the rock matrix. Furthermore, fractures that intersect with Dirichlet or Neumann boundaries are considered. Simulation examples are designed to verify the efficiency of the tree-cutting algorithm, the calculation's independency from the mesh orientation, and accuracy when modeling porous media that contain fractures with multiple intersections and different orientations. The simulation results show good agreement with available analytical solutions. Finally, the model is applied to cases that involve nine intersecting fractures and a complex network of 100 fractures, both of which achieve reasonable results. The new model is very practical for modeling flow in fractured porous media, even for a geometrically complex fracture network with large hydraulic conductivity contrasts between fractures and the matrix.
Analysis of Fluid Flow over a Surface
NASA Technical Reports Server (NTRS)
McCloud, Peter L. (Inventor)
2013-01-01
A method, apparatus, and computer program product for modeling heat radiated by a structure. The flow of a fluid over a surface of a model of the structure is simulated. The surface has a plurality of surface elements. Heat radiated by the plurality of surface elements in response to the fluid flowing over the surface of the model of the structure is identified. An effect of heat radiated by at least a portion of the plurality of surface elements on each other is identified. A model of the heat radiated by the structure is created using the heat radiated by the plurality of surface elements and the effect of the heat radiated by at least a portion of the plurality of surface elements on each other.
Finite scale equations for compressible fluid flow
Margolin, Len G
2008-01-01
Finite-scale equations (FSE) describe the evolution of finite volumes of fluid over time. We discuss the FSE for a one-dimensional compressible fluid, whose every point is governed by the Navier-Stokes equations. The FSE contain new momentum and internal energy transport terms. These are similar to terms added in numerical simulation for high-speed flows (e.g. artificial viscosity) and for turbulent flows (e.g. subgrid scale models). These similarities suggest that the FSE may provide new insight as a basis for computational fluid dynamics. Our analysis of the FS continuity equation leads to a physical interpretation of the new transport terms, and indicates the need to carefully distinguish between volume-averaged and mass-averaged velocities in numerical simulation. We make preliminary connections to the other recent work reformulating Navier-Stokes equations.
NASA Astrophysics Data System (ADS)
Sandbach, S. D.; Hardy, R. J.; Lane, S. N.; Ashworth, P. J.; Parsons, D. R.
2010-12-01
Our understanding of large rivers is limited due to the difficulties in obtaining field data at these large scales. Data rich results may be obtained using computational fluid dynamic (CFD) models permitting the investigation of detailed flow patterns that would otherwise not be available. However, the application of these models to large rivers is not without its own complications and has yet to be fully developed. This is the result of two limiting factors, our inability; i) to design numerically stable meshes for complex topographies at these spatial resolutions; and; ii) to collect high resolution data appropriate for the boundary conditions of the numerical scheme. Here, we demonstrate a five-term mass-flux scaling algorithm (MFSA) for including bed topography in a very large river, where the discretised form of the mass and momentum equations are modified using a numerical blockage. Converged solutions were obtained using the Reynolds-averaged Navier stokes (RANS) equations modelling turbulence with a κ-ɛ RNG turbulence model. The boundary conditions were supplied from a field investigation of the Rio Paraná upstream of the Paraguay-Paraná confluence. A 38 km long reach was investigated where topographic and velocity data was collected using an acoustic Doppler current profiler (aDcp) and a single beam echo sounder. The model was validated against the aDcp data and in general showed good agreement. The model was then used to explore the impacts of roughness height upon key characteristics of the 3D flow field in large rivers. The results demonstrate the importance of topographic forcing on determining flow structures including the detection of large helical flow structures.
Xu, Chun; Sin, SangHun; McDonough, Joseph M; Udupa, Jayaram K; Guez, Allon; Arens, Raanan; Wootton, David M
2006-01-01
Computational fluid dynamic (CFD) analysis was used to model the effect of airway geometry on internal pressure in the upper airway of three children with obstructive sleep apnea syndrome (OSAS), and three controls. Model geometry was reconstructed from magnetic resonance images obtained during quiet tidal breathing, meshed with an unstructured grid, and solved at normative peak resting flow. The unsteady Reynolds-averaged Navier-Stokes equations were solved with steady flow boundary conditions in inspiration and expiration, using a two-equation low-Reynolds number turbulence model. Model results were validated using an in-vitro scale model, unsteady flow simulation, and reported nasal resistance measurements in children. Pharynx pressure drop strongly correlated to airway area restriction. Inspiratory pressure drop was primarily proportional to the square of flow, consistent with pressure losses due to convective acceleration caused by area restriction. On inspiration, in OSAS pressure drop occurred primarily between the choanae and the region where the adenoids overlap the tonsils (overlap region) due to airway narrowing, rather than in the nasal passages; in controls the majority of pressure drop was in the nasal passages. On expiration, in OSAS the majority of pressure drop occurred between the oropharynx (posterior to the tongue) and overlap region, and local minimum pressure in the overlap region was near atmospheric due to pressure recovery in the anterior nasopharynx. The results suggest that pharyngeal airway shape in children with OSAS significantly affects internal pressure distribution compared to nasal resistance. The model may also help explain regional dynamic airway narrowing during expiration. PMID:16098533
NASA Astrophysics Data System (ADS)
Kees, C. E.; Farthing, M.; Dimakopoulos, A.; DeLataillade, T.
2015-12-01
Performance analysis and optimization of coastal and navigation structures is becoming feasible due to recent improvements in numerical methods for multiphase flows and the steady increase in capacity and availability of high performance computing resources. Now that the concept of fully three-dimensional air/water flow modelling for real world engineering analysis is achieving acceptance by the wider engineering community, it is critical to expand careful comparative studies on verification,validation, benchmarking, and uncertainty quantification for the variety of competing numerical methods that are continuing to evolve. Furthermore, uncertainty still remains about the relevance of secondary processes such as surface tension, air compressibility, air entrainment, and solid phase (structure) modelling so that questions about continuum mechanical theory and mathematical analysis of multiphase flow are still required. Two of the most popular and practical numerical approaches for large-scale engineering analysis are the Volume-Of-Fluid (VOF) and Level Set (LS) approaches. In this work we will present a publically available verification and validation test set for air-water-structure interaction problems as well as computational and physical model results including a hybrid VOF-LS method, traditional VOF methods, and Smoothed Particle Hydrodynamics (SPH) results. The test set repository and test problem formats will also be presented in order to facilitate future comparative studies and reproduction of scientific results.
Coupled Model for CO2 Leaks from Geological Storage: Geomechanics, Fluid Flow and Phase Transitions
NASA Astrophysics Data System (ADS)
Gor, G.; Prevost, J.
2013-12-01
Deep saline aquifers are considered as a promising option for long-term storage of carbon dioxide. However, risk of CO2 leakage from the aquifers through faults, natural or induced fractures or abandoned wells cannot be disregarded. Therefore, modeling of various leakage scenarios is crucial when selecting a site for CO2 sequestration and choosing proper operational conditions. Carbon dioxide is injected into wells at supercritical conditions (t > 31.04 C, P > 73.82 bar), and these conditions are maintained in the deep aquifers (at 1-2 km depth) due to hydrostatic pressure and geothermal gradient. However, if CO2 and brine start to migrate from the aquifer upward, both pressure and temperature will decrease, and at the depth of 500-750 m, the conditions for CO2 will become subcritical. At subcritical conditions, CO2 starts boiling and the character of the flow changes dramatically due to appearance of the third (vapor) phase and latent heat effects. When modeling CO2 leaks, one needs to couple the multiphase flow in porous media with geomechanics. These capabilities are provided by Dynaflow, a finite element analysis program [1]; Dynaflow has already showed to be efficient for modeling caprock failure causing CO2 leaks [2, 3]. Currently we have extended the capabilities of Dynaflow with the phase transition module, based on two-phase and three-phase isenthalpic flash calculations [4]. We have also developed and implemented an efficient method for solving heat and mass transport with the phase transition using our flash module. Therefore, we have developed a robust tool for modeling CO2 leaks. In the talk we will give a brief overview of our method and illustrate it with the results of simulations for characteristic test cases. References: [1] J.H. Prevost, DYNAFLOW: A Nonlinear Transient Finite Element Analysis Program. Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ. http://www.princeton.edu/~dynaflow/ (last update 2013
Numerical modelling of the stability of loaded shells of revolution containing fluid flows
NASA Astrophysics Data System (ADS)
Bochkarev, S. A.; Matveenko, V. P.
2008-03-01
A mixed finite-element algorithm is proposed to study the dynamic behavior of loaded shells of revolution containing a stationary or moving compressible fluid. The behavior of the fluid is described by potential theory, whose equations are reduced to integral form using the Galerkin method. The dynamics of the shell is analyzed with the use of the variational principle of possible displacements, which includes the linearized Bernoulli equation for calculating the hydrodynamic pressure exerted on the shell by the fluid. The solution of the problem reduces to the calculation and analysis of the eigenvalues of the coupled system of equations. As an example, the effect of hydrostatic pressure on the dynamic behavior of shells of revolution containing a moving fluid is studied under various boundary conditions.
Analytical study of Cattaneo-Christov heat flux model for a boundary layer flow of Oldroyd-B fluid
NASA Astrophysics Data System (ADS)
F, M. Abbasi; M, Mustafa; S, A. Shehzad; M, S. Alhuthali; T, Hayat
2016-01-01
We investigate the Cattaneo-Christov heat flux model for a two-dimensional laminar boundary layer flow of an incompressible Oldroyd-B fluid over a linearly stretching sheet. Mathematical formulation of the boundary layer problems is given. The nonlinear partial differential equations are converted into the ordinary differential equations using similarity transformations. The dimensionless velocity and temperature profiles are obtained through optimal homotopy analysis method (OHAM). The influences of the physical parameters on the velocity and the temperature are pointed out. The results show that the temperature and the thermal boundary layer thickness are smaller in the Cattaneo-Christov heat flux model than those in the Fourier’s law of heat conduction. Project supported by the Deanship of Scientific Research (DSR) King Abdulaziz University, Jeddah, Saudi Arabia (Grant No. 32-130-36-HiCi).
Habbal, Shadia Rifai; Esser, Ruth; Guhathakurta, Madhulika; Fisher, Richard
1996-07-20
We derive the flow properties of the solar wind using a two-fluid model constrained by the density gradients inferred from white light observations of a south polar coronal hole on 11 April 1993 during the SPARTAN 201-1 flight, and interplanetary observations, e.g. from Ulysses' south polar passage. We present the results of model computations for which we get the best fit to these data. One of the main results of this study is that, for the same energy input to electrons and protons, the proton temperature can be significantly higher than the electron temperature in the inner corona. In addition, we show that different functional forms of the energy addition with the same total energy input can yield different solar wind parameters at 1AU.
2-Phase Fluid Flow & Heat Transport
1993-03-13
GEOTHER is a three-dimensional, geothermal reservoir simulation code. The model describes heat transport and flow of a single component, two-phase fluid in porous media. It is based on the continuity equations for steam and water, which are reduced to two nonlinear partial differential equations in which the dependent variables are fluid pressure and enthalpy. GEOTHER can be used to simulate the fluid-thermal interaction in rock that can be approximated by a porous media representation. Itmore » can simulate heat transport and the flow of compressed water, two-phase mixtures, and superheated steam in porous media over a temperature range of 10 to 300 degrees C. In addition, it can treat the conversion from single to two-phase flow, and vice versa. It can be used for evaluation of a near repository spatial scale and a time scale of a few years to thousands of years. The model can be used to investigate temperature and fluid pressure changes in response to thermal loading by waste materials.« less
NASA Technical Reports Server (NTRS)
Bandyopadhyay, Alak; Majumdar, Alok
2007-01-01
The present paper describes the verification and validation of a quasi one-dimensional pressure based finite volume algorithm, implemented in Generalized Fluid System Simulation Program (GFSSP), for predicting compressible flow with friction, heat transfer and area change. The numerical predictions were compared with two classical solutions of compressible flow, i.e. Fanno and Rayleigh flow. Fanno flow provides an analytical solution of compressible flow in a long slender pipe where incoming subsonic flow can be choked due to friction. On the other hand, Raleigh flow provides analytical solution of frictionless compressible flow with heat transfer where incoming subsonic flow can be choked at the outlet boundary with heat addition to the control volume. Nonuniform grid distribution improves the accuracy of numerical prediction. A benchmark numerical solution of compressible flow in a converging-diverging nozzle with friction and heat transfer has been developed to verify GFSSP's numerical predictions. The numerical predictions compare favorably in all cases.
NASA Astrophysics Data System (ADS)
Li, Linmin; Liu, Zhongqiu; Cao, Maoxue; Li, Baokuan
2015-07-01
In the ladle metallurgy process, the bubble movement and slag layer behavior is very important to the refining process and steel quality. For the bubble-liquid flow, bubble movement plays a significant role in the phase structure and causes the unsteady complex turbulent flow pattern. This is one of the most crucial shortcomings of the current two-fluid models. In the current work, a one-third scale water model is established to investigate the bubble movement and the slag open-eye formation. A new mathematical model using the large eddy simulation (LES) is developed for the bubble-liquid-slag-air four-phase flow in the ladle. The Eulerian volume of fluid (VOF) model is used for tracking the liquid-slag-air free surfaces and the Lagrangian discrete phase model (DPM) is used for describing the bubble movement. The turbulent liquid flow is induced by bubble-liquid interactions and is solved by LES. The procedure of bubble coming out of the liquid and getting into the air is modeled using a user-defined function. The results show that the present LES-DPM-VOF coupled model is good at predicting the unsteady bubble movement, slag eye formation, interface fluctuation, and slag entrainment.
Cheng, Cheng; Zhang, Xiaobing
2013-05-01
In conventional models for two-phase reactive flow of interior ballistic, the dynamic collision phenomenon of particles is neglected or empirically simplified. However, the particle collision between particles may play an important role in dilute two-phase flow because the distribution of particles is extremely nonuniform. The collision force may be one of the key factors to influence the particle movement. This paper presents the CFD-DEM approach for simulation of interior ballistic two-phase flow considering the dynamic collision process. The gas phase is treated as a Eulerian continuum and described by a computational fluid dynamic method (CFD). The solid phase is modeled by discrete element method (DEM) using a soft sphere approach for the particle collision dynamic. The model takes into account grain combustion, particle-particle collisions, particle-wall collisions, interphase drag and heat transfer between gas and solid phases. The continuous gas phase equations are discretized in finite volume form and solved by the AUSM+-up scheme with the higher order accurate reconstruction method. Translational and rotational motions of discrete particles are solved by explicit time integrations. The direct mapping contact detection algorithm is used. The multigrid method is applied in the void fraction calculation, the contact detection procedure, and CFD solving procedure. Several verification tests demonstrate the accuracy and reliability of this approach. The simulation of an experimental igniter device in open air shows good agreement between the model and experimental measurements. This paper has implications for improving the ability to capture the complex physics phenomena of two-phase flow during the interior ballistic cycle and to predict dynamic collision phenomena at the individual particle scale.
A Coupled Multiphase Fluid Flow And Heat And Vapor Transport Model For Air-Gap Membrane Distillation
NASA Astrophysics Data System (ADS)
Mukhopadhyay, Sumit
2010-05-01
Membrane distillation (MD) is emerging as a viable desalination technology because of its low energy requirements that can be provided from low-grade, waste heat and because it causes less fouling. In MD, desalination is accomplished by transporting water vapour through a porous hydrophobic membrane. The vapour transport process is governed by the vapour pressure difference between the two sides of a membrane. A variety of configurations have been tested to impose this vapour pressure gradient, however, the air-gap membrane distillation (AGMD) has been found to be the most efficient. The separation mechanism of AGMD and its overall efficiency is based on vapour-liquid equilibrium (VLE). At present, little knowledge is available about the optimal design of such a transmembrane VLE-based evaporation, and subsequent condensation processes. While design parameters for MD have evolved mostly through experimentations, a comprehensive mathematical model is yet to be developed. This is primarily because the coupling and non-linearity of the equations, the interactions between the flow, heat and mass transport regimes, and the complex geometries involved pose a challenging modelling and simulation problem. Yet a comprehensive mathematical model is needed for systematic evaluation of the processes, design parameterization, and performance prediction. This paper thus presents a coupled fluid flow, heat and mass transfer model to investigate the main processes and parameters affecting the performance of an AGMD.
Tchafa, Alimatou M; Shah, Arpit D; Wang, Shafei; Duong, Melissa T; Shieh, Adrian C
2012-07-25
The growth and progression of most solid tumors depend on the initial transformation of the cancer cells and their response to stroma-associated signaling in the tumor microenvironment (1). Previously, research on the tumor microenvironment has focused primarily on tumor-stromal interactions (1-2). However, the tumor microenvironment also includes a variety of biophysical forces, whose effects remain poorly understood. These forces are biomechanical consequences of tumor growth that lead to changes in gene expression, cell division, differentiation and invasion(3). Matrix density (4), stiffness (5-6), and structure (6-7), interstitial fluid pressure (8), and interstitial fluid flow (8) are all altered during cancer progression. Interstitial fluid flow in particular is higher in tumors compared to normal tissues (8-10). The estimated interstitial fluid flow velocities were measured and found to be in the range of 0.1-3 μm s(-1), depending on tumor size and differentiation (9, 11). This is due to elevated interstitial fluid pressure caused by tumor-induced angiogenesis and increased vascular permeability (12). Interstitial fluid flow has been shown to increase invasion of cancer cells (13-14), vascular fibroblasts and smooth muscle cells (15). This invasion may be due to autologous chemotactic gradients created around cells in 3-D (16) or increased matrix metalloproteinase (MMP) expression (15), chemokine secretion and cell adhesion molecule expression (17). However, the mechanism by which cells sense fluid flow is not well understood. In addition to altering tumor cell behavior, interstitial fluid flow modulates the activity of other cells in the tumor microenvironment. It is associated with (a) driving differentiation of fibroblasts into tumor-promoting myofibroblasts (18), (b) transporting of antigens and other soluble factors to lymph nodes (19), and (c) modulating lymphatic endothelial cell morphogenesis (20). The technique presented here imposes interstitial
NASA Astrophysics Data System (ADS)
Tecklenburg, Jan; Neuweiler, Insa
2014-05-01
Flow processes in geotechnical applications do often take place in highly heterogeneous porous media, such as fractured rock. Since, in this type of media, classical modelling approaches are problematic, flow and transport is often modelled using multi-continua approaches. Based on such approaches, we derived a multirate mass transfer (mrmt) model for immiscible displacement of two fluids in highly heterogeneous media including capillary forces by Homogenization theory (see Tecklenburg et. al. (2013)). For the mrmt model the fractured media is represented by a mobile zone, where "fast" flow takes place, and an immobile zone. The immobile zone would be the rock matrix and the mobile zone would be the connected fracture network, where the fractures are represented by an equivalent porous media. The flow in the mobile zone is modelled by the Buckley-Leverett equation. This equation is expanded by a sink-source-term which is nonlocal in time to model the mass transfer between the mobile and the immobile zone. For immiscible displacement of two fluids the mass transfer can be driven by capillary diffusion. For particular imbibition cases this diffusive mass transfer process can be linearized. In this contribution we test the applicability of the mrmt model for the two phase flow in two dimensional fracture networks. This is done with numerical simulations of immiscible displacement in fracture networks. We compare the results of the mrmt model and the results of a full two dimensional two phase flow model where the code dumux by Flemisch et. al. (2011) is used. The flow parameters for the mrmt model are calculated by analyzing fracture and matrix geometry and using the integral solution for two phase flow by McWorther and Sunnada (1990). Tecklenburg, J., Neuweiler, I., Dentz, M., Carrera, J., Geiger, S., Abramowski, C. and O. Silva: A non-local two-phase flow model for immiscible displacement in highly heterogeneous porous media and its parametrization, Advances in
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.
Rakowski, Cynthia L.; Serkowski, John A.; Richmond, Marshall C.; Perkins, William A.
2010-12-01
In 2003, an extension of the existing ice and trash sluiceway was added at Bonneville Powerhouse 2 (B2). This extension started at the existing corner collector for the ice and trash sluiceway adjacent to Bonneville Powerhouse 2 and the new sluiceway was extended to the downstream end of Cascade Island. The sluiceway was designed to improve juvenile salmon survival by bypassing turbine passage at B2, and placing these smolt in downstream flowing water minimizing their exposure to fish and avian predators. In this study, a previously developed computational fluid dynamics model was modified and used to characterized tailrace hydraulics and sluiceway egress conditions for low total river flows and low levels of spillway flow. STAR-CD v4.10 was used for seven scenarios of low total river flow and low spill discharges. The simulation results were specifically examined to look at tailrace hydraulics at 5 ft below the tailwater elevation, and streamlines used to compare streamline pathways for streamlines originating in the corner collector outfall and adjacent to the outfall. These streamlines indicated that for all higher spill percentage cases (25% and greater) that streamlines from the corner collector did not approach the shoreline at the downstream end of Bradford Island. For the cases with much larger spill percentages, the streamlines from the corner collector were mid-channel or closer to the Washington shore as they moved downstream. Although at 25% spill at 75 kcfs total river, the total spill volume was sufficient to "cushion" the flow from the corner collector from the Bradford Island shore, areas of recirculation were modeled in the spillway tailrace. However, at the lowest flows and spill percentages, the streamlines from the B2 corner collector pass very close to the Bradford Island shore. In addition, the very flow velocity flows and large areas of recirculation greatly increase potential predator exposure of the spillway passed smolt. If there is
Flow behaviour of extremely bidisperse magnetizable fluids
NASA Astrophysics Data System (ADS)
Susan-Resiga, Daniela; Bica, Doina; Vékás, L.
2010-10-01
In this paper we investigated the rheological and magnetorheological behaviours of an extremely bidisperse (nano-micro) magnetizable fluid (sample D1) for comparison of a commercial magnetorheological fluid (MRF-140CG; LORD Co. (USA)) with the same magnetic solid volume fraction, using the Physica MCR-300 rheometer with a 20 mm diameter plate-plate magnetorheological cell (MRD180). D1 sample is a suspension of micrometer range Fe particles in a transformer oil based magnetic fluid as carrier. For both types of samples, the experimental data for zero and non-zero magnetic field conditions were fitted to equations derived from the Newtonian and Cross type flow equations, as well as the Herschel-Bulkley model. The main advantage of both rheological equations for the quantitative description of the magnetic field behaviour of samples is that they can be used in regular CFD codes to compute the flow properties of the magnetorheological fluid and of the bidisperse magnetizable fluid for practical applications.
Fluid Flow Experiment for Undergraduate Laboratory.
ERIC Educational Resources Information Center
Vilimpochapornkul, Viroj; Obot, Nsima T.
1986-01-01
The undergraduate fluid mechanics laboratory at Clarkson University consists of three experiments: mixing; drag measurements; and fluid flow and pressure drop measurements. The latter experiment is described, considering equipment needed, procedures used, and typical results obtained. (JN)
López, Dina L.; Smith, Leslie; Storey, Michael L.; Nielson, Dennis L.
1994-01-01
The hydrothermal systems of the Basin and Range Province are often located at or near major range bounding normal faults. The flow of fluid and energy at these faults is affected by the advective transfer of heat and fluid from an to the adjacent mountain ranges and valleys, This paper addresses the effect of the exchange of fluid and energy between the country rock, the valley fill sediments, and the fault zone, on the fluid and heat flow regimes at the fault plane. For comparative purposes, the conditions simulated are patterned on Leach Hot Springs in southern Grass Valley, Nevada. Our simulations indicated that convection can exist at the fault plane even when the fault is exchanging significant heat and fluid with the surrounding country rock and valley fill sediments. The temperature at the base of the fault decreased with increasing permeability of the country rock. Higher groundwater discharge from the fault and lower temperatures at the base of the fault are favored by high country rock permabilities and fault transmissivities. Preliminary results suggest that basal temperatures and flow rates for Leach Hot Springs can not be simulated with a fault 3 km deep and an average regional heat flow of 150 mW/m2 because the basal temperature and mass discharge rates are too low. A fault permeable to greater depths or a higher regional heat flow may be indicated for these springs.
NASA Astrophysics Data System (ADS)
Hasan, Raisul
2016-07-01
In this research paper firstly theoretical analysis and design of the porous matrix for filtration and selection of associated liquid (highly viscous and low viscous liquid) is carried out. Hence, porosity of the bed has been found out followed by a detailed CFD analysis of the flow to identify displacement structure (fingering: due to the nonlinear interactions among viscous, capillary and gravitational forces). Moreover, an experiment will be with synthetic porous medium consists of a single layer of glass beads which are then positioned homogeneously or non-homogeneously between two Perspex sheets and then fluid displacement structure/fingering will be photographed. Then the effort will be made to validate results with the experiment based photograph and then the CFD model will be extended to microgravity condition KEYWORDS: CFD, Fingering, microgravity, Non-homogeneously, Capillary .
Barton, C.C.; Larsen, E.; Page, W.R.; Howard, T.M.
1993-12-31
Fractures have been characterized for fluid-flow, geomechanical, and paleostress modeling at three localities in the vicinity of drill hole USW G-4 at Yucca Mountain in southwestern Nevada. A method for fracture characterization is introduced that integrates mapping fracture-trace networks and quantifying eight fracture parameters: trace length, orientation, connectivity, aperture, roughness, shear offset, trace-length density, and mineralization. A complex network of fractures was exposed on three 214- to 260-m 2 pavements cleared of debris in the upper lithophysal unit of the Tiva Canyon Member of the Miocene Paint-brush Tuff. The pavements are two-dimensional sections through the three-dimensional network of strata-bound fractures. All fractures with trace lengths greater than 0.2 m were mapped and studied.
NASA Astrophysics Data System (ADS)
Riasi, M. S.; Huang, G.; Montemagno, C.; Yeghiazarian, L.
2014-12-01
Micro-scale modeling of multiphase flow in porous media is critical to characterize porous materials. Several modeling techniques have been implemented to date, but none can be used as a general strategy for all porous media applications due to challenges presented by non-smooth high-curvature and deformable solid surfaces, and by a wide range of pore sizes and porosities. Finite approaches like the finite volume method require a high quality, problem-dependent mesh, while particle-based approaches like the lattice Boltzmann require too many particles to achieve a stable meaningful solution. Both come at a large computational cost. Other methods such as pore network modeling (PNM) have been developed to accelerate the solution process by simplifying the solution domain, but so far a unique and straightforward methodology to implement PNM is lacking. Pore topology method (PTM) is a new topologically consistent approach developed to simulate multiphase flow in porous media. The core of PTM is to reduce the complexity of the 3-D void space geometry by working with its medial surface as the solution domain. Medial surface is capable of capturing all the corners and surface curvatures in a porous structure, and therefore provides a topologically consistent representative geometry for porous structure. Despite the simplicity and low computational cost, PTM provides a fast and straightforward approach for micro-scale modeling of fluid flow in all types of porous media irrespective of their porosity and pore size distribution. In our previous work, we developed a non-iterative fast medial surface finder algorithm to determine a voxel-wide medial surface of the void space of porous media as well as a set of simple rules to determine the capillary pressure-saturation curves for a porous system assuming quasi-static two-phase flow with a planar w-nw interface. Our simulation results for a highly porous fibrous material and polygonal capillary tubes were in excellent agreement
NASA Astrophysics Data System (ADS)
Iyer, Karthik; Schmid, Daniel
2016-04-01
Evidence of mass extinction events in conjunction with climate change occur throughout the geological record and may be accompanied by pronounced negative carbon isotope excursions. The processes that trigger such globally destructive changes are still under considerable debate. These include mechanisms such as poisoning from trace metals released during large volcanic eruptions (Vogt, 1972), CO2 released from lava degassing during the formation of Large Igneous Provinces (LIPs) (Courtillot and Renne, 2003) and CH4 release during the destabilization of sub-seafloor methane (Dickens et al., 1995), to name a few. Thermogenic methane derived from contact metamorphism associated with magma emplacement and cooling in sedimentary basins has been recently gaining considerable attention as a potential mechanism that may have triggered global climate events in the past (e.g. Svensen and Jamtveit, 2010). The discovery of hydrothermal vent complexes that are spatially associated with such basins also supports the discharge of greenhouse gases into the atmosphere (e.g. Jamtveit et al., 2004; Planke et al., 2005; Svensen et al., 2006). A previous study that investigated this process using a fluid flow model (Iyer et al., 2013) suggested that although hydrothermal plume formation resulting from sill emplacement may indeed release large quantities of methane at the surface, the rate at which this methane is released into the atmosphere is too slow to trigger, by itself, some of the negative δ13C excursions observed in the fossil record over short time scales observed in the fossil record. Here, we reinvestigate the rates of gas release during sill emplacement in a case study from the Harstad Basin off-shore Norway with a special emphasis on vent formation. The presented study is based on a seismic line that crosses multiple sill structures emplaced around 55 Ma within the Lower Cretaceous sediments. A single well-defined vent complex is interpreted above the termination of the
Using toughreact to model reactive fluid flow and geochemical transport in hydrothermal systems
Xu, Tianfu; Sonnenthal, Eric; Spycher, Nicolas; Pruess, Karsten
2003-07-31
The interaction between hydrothermal fluids and the rocks through which they migrate alters the earlier formed primary minerals and leads to the formation of secondary minerals, resulting in changes in the physical and chemical properties of the system. We have developed a comprehensive numerical simulator, TOUGHREACT, which considers nonisothermal multi-component chemical transport in both liquid and gas phases. A variety of subsurface thermo-physical-chemical processes is considered under a wide range of conditions of pressure, temperature, water saturation, and ionic strength. The code can be applied to problems in fundamental analysis of the hydrothermal systems and in the exploration of geothermal reservoirs including chemical evolution, mineral alteration, mineral scaling, changes of porosity and permeability, and mineral recovery from geothermal fluids.
McHugh, P.R.; Ramshaw, J.D.
1991-11-01
MAGMA is a FORTRAN computer code designed to viscous flow in in situ vitrification melt pools. It models three-dimensional, incompressible, viscous flow and heat transfer. The momentum equation is coupled to the temperature field through the buoyancy force terms arising from the Boussinesq approximation. All fluid properties, except density, are assumed variable. Density is assumed constant except in the buoyancy force terms in the momentum equation. A simple melting model based on the enthalpy method allows the study of the melt front progression and latent heat effects. An indirect addressing scheme used in the numerical solution of the momentum equation voids unnecessary calculations in cells devoid of liquid. Two-dimensional calculations can be performed using either rectangular or cylindrical coordinates, while three-dimensional calculations use rectangular coordinates. All derivatives are approximated by finite differences. The incompressible Navier-Stokes equations are solved using a new fully implicit iterative technique, while the energy equation is differenced explicitly in time. Spatial derivatives are written in conservative form using a uniform, rectangular, staggered mesh based on the marker and cell placement of variables. Convective terms are differenced using a weighted average of centered and donor cell differencing to ensure numerical stability. Complete descriptions of MAGMA governing equations, numerics, code structure, and code verification are provided. 14 refs.
NASA Astrophysics Data System (ADS)
Abushaikha, Ahmad S.; Blunt, Martin J.; Gosselin, Olivier R.; Pain, Christopher C.; Jackson, Matthew D.
2015-10-01
We present a new control volume finite element method that improves the modelling of multi-phase fluid flow in highly heterogeneous and fractured reservoirs, called the Interface Control Volume Finite Element (ICVFE) method. The method drastically decreases the smearing effects in other CVFE methods, while being mass conservative and numerically consistent. The pressure is computed at the interfaces of elements, and the control volumes are constructed around them, instead of at the elements' vertices. This assures that a control volume straddles, at most, two elements, which decreases the fluid smearing between neighbouring elements when large variations in their material properties are present. Lowest order Raviart-Thomas vectorial basis functions are used for the pressure calculation and first-order Courant basis functions are used to compute fluxes. The method is a combination of Mixed Hybrid Finite Element (MHFE) and CVFE methods. Its accuracy and convergence are tested using three dimensional tetrahedron elements to represent heterogeneous reservoirs. Our new approach is shown to be more accurate than current CVFE methods.
NASA Astrophysics Data System (ADS)
Iyer, K. H.; Rupke, L.
2013-12-01
In recent years, the emplacement of Large Igneous Provinces (LIPs) has been closely linked with past climate variations and mass extinctions. The hypothesis is that organic matter present within contact aureole of the surrounding sedimentary rock such as shale undergoes thermal maturation and releases greenhouse gases such as methane and carbon dioxide due to the emplacement of hot igneous bodies. These gases are then vented into the atmosphere through hydrothermal pipe structures resulting in climate change. Although, basin-scale estimates of potential methane generation show that these processes alone could trigger global incidents, the rates at which these gases are released into the atmosphere and the transport mechanism are quantitatively unknown. We use a 2D, hybrid FEM/FVM model that solves for fully compressible fluid flow to quantify the thermogenic release of methane and to evaluate flow patterns within these systems. In addition, methane transport within the system is tracked enabling us to constrain the rate of release of methane from the basin surface. The important outcomes of this study are: (1) the location of hydrothermal vents is directly controlled by the flow pattern, even in systems with no vigorous convection, without the explicit need for explosive degassing and/or boiling effects. The merging of fluid flow from the bottom and top edges of the sill result in hydrothermal plumes positioned at the lateral edges of the sill and is consistent with geological observations. (2) Methane generation potential in systems with fluid flow does not significantly differ from that estimated in diffusive systems, e.g. 2200 to 3350 Gt CH4 can be potentially generated within the Vøring and Møre basins with a sediment TOC content of 5 wt% and varying permeability structure. On the other hand, methane venting at the surface occurs in three distinct stages and can last for hundreds of thousands of years. Also, not all of the methane reaches the surface as some
Ben Hadj Ali, A.; Laurien, E.
2012-07-01
A three-fluid model of counter-current air-water flow is suggested. The accurate prediction of droplet entrainment in two-phase flows is relevant to calculate interfacial exchange between the fluids. The present study delivers a model based on the constitutive physics for droplet separation considering re-entrainment of the dispersed water droplets into the continuous water film. A monodisperse distribution of the droplets is taken into account by means of a transport equation for the droplet number density in order to determine the droplet size. (authors)
Encyclopedia of fluid mechanics. Volume 2 - Dynamics of single-fluid flows and mixing
NASA Astrophysics Data System (ADS)
Cheremisinoff, N. P.
Various papers on the dynamics of single-fluid flows and mixing are presented. The general topics addressed include: channel and free surface flows, mixing phenomena and practices, and fluid transport equipment. Individual papers discuss: statistics of deep water surface waves, unstable turbulent channel flow, hydraulic jumps and internal flows, wave attenuation in open channel flow, straight sediment stable channels, three-dimensional deep-water waves, estimating peak flows, hydrodynamics of laminar buoyant jets, impinging jets, hydrodynamics of confined coaxial jets, and turbulent mixing and diffusion of jets. Also addressed are: hydrodynamics of jets in cross flow, modelling turbulent jets in cross flow, batchwise jet mixing in tanks, stability of jets in liquid-liquid systems, jet mixing of fluids in vessels, mixing in loop reactors, backmixing in stirred vessels, industrial mixing equipment, pump classifications and design features, oscillating displacement pumps, fluid dynamics of inducers, hydrodynamics of outflow from vessels, and analysis of axial flow turbines.
Sefidgar, Mostafa; Soltani, M; Raahemifar, Kaamran; Bazmara, Hossein
2015-01-01
A solid tumor is investigated as porous media for fluid flow simulation. Most of the studies use Darcy model for porous media. In Darcy model, the fluid friction is neglected and a few simplified assumptions are implemented. In this study, the effect of these assumptions is studied by considering Brinkman model. A multiscale mathematical method which calculates fluid flow to a solid tumor is used in this study to investigate how neglecting fluid friction affects the solid tumor simulation. The mathematical method involves processes such as blood flow through vessels and solute and fluid diffusion, convective transport in extracellular matrix, and extravasation from blood vessels. The sprouting angiogenesis model is used for generating capillary network and then fluid flow governing equations are implemented to calculate blood flow through the tumor-induced capillary network. Finally, the two models of porous media are used for modeling fluid flow in normal and tumor tissues in three different shapes of tumors. Simulations of interstitial fluid transport in a solid tumor demonstrate that the simplifications used in Darcy model affect the interstitial velocity and Brinkman model predicts a lower value for interstitial velocity than the values that Darcy model predicts.
Vaughan, T J; Haugh, M G; McNamara, L M
2013-04-01
Bone continuously adapts its internal structure to accommodate the functional demands of its mechanical environment and strain-induced flow of interstitial fluid is believed to be the primary mediator of mechanical stimuli to bone cells in vivo. In vitro investigations have shown that bone cells produce important biochemical signals in response to fluid flow applied using parallel-plate flow chamber (PPFC) systems. However, the exact mechanical stimulus experienced by the cells within these systems remains unclear. To fully understand this behaviour represents a most challenging multi-physics problem involving the interaction between deformable cellular structures and adjacent fluid flows. In this study, we use a fluid-structure interaction computational approach to investigate the nature of the mechanical stimulus being applied to a single osteoblast cell under fluid flow within a PPFC system. The analysis decouples the contribution of pressure and shear stress on cellular deformation and for the first time highlights that cell strain under flow is dominated by the pressure in the PPFC system rather than the applied shear stress. Furthermore, it was found that strains imparted on the cell membrane were relatively low whereas significant strain amplification occurred at the cell-substrate interface. These results suggest that strain transfer through focal attachments at the base of the cell are the primary mediators of mechanical signals to the cell under flow in a PPFC system. Such information is vital in order to correctly interpret biological responses of bone cells under in vitro stimulation and elucidate the mechanisms associated with mechanotransduction in vivo.
Fluid flow in crystallization processes
NASA Technical Reports Server (NTRS)
Brown, R. A.
1982-01-01
Investigations of the interactions of heat, mass, and momentum transport in crystal growth from the melt are described. Studies of the mall-scale floating zone process and on a prototype of the vertical Bridgman growth system were emphasized. In both systems detailed numerical calculations are used to dissect the interplay between fluid convection and dopant segregation. These calculations are based on finite element techniques that make feasible the complete solution of solidification problems which include convection. Other numerical methods were developed for solving thermal models of crystal growth processes with melt/gas menisci and for simulating the microscale instabilities in solidification interfaces.
NASA Astrophysics Data System (ADS)
Li, Rong; She, Zhen-Su; Yin, Lan; State Key Laboratory for Turbulence; Complex Systems Team
Transport properties of vortex fluid in high-temperature superconductors have been described in terms of viscous dynamics of magnetic and thermal vortices. We have constructed a quantitative model by extending the Bardeen-Stephen model of damping viscosity to include the contributions of flux pinning in low temperature and vortex-vortex interaction in high magnetic field. A uniformly accurate description of flux flow resistivity and Nernst signal is achieved for empirical data over a wide range of temperature and magnetic field strength. A discrepancy of three orders of magnitude between data and Anderson model of Nernst signal is pointed out, suggesting the existence of anomalous transport in high-temperature superconductor beyond mere quantum and thermal fluctuations. The model enables to derive a set of physical parameters characterizing the vortex dynamics from the Nernst signal, as we illustrate with an analysis of six samples of Bi2Sr2-yLayCuO6 and Bi2Sr2CaCu2O8+δ.
NASA Astrophysics Data System (ADS)
Lee, Choon-Tae; Moon, Byung-Young
2006-02-01
In this study, a new mathematical dynamic model of shock absorber is proposed to predict the dynamic characteristics of an automotive system. The performance of shock absorber is directly related to the car behaviours and performance, both for handling and ride comfort. Damping characteristics of automotive can be analysed by considering the performance of displacement-sensitive shock absorber (DSSA) for the ride comfort. The proposed model of the DSSA is considered as two modes of damping force (i.e. soft and hard) according to the position of piston. For the simulation validation of vehicle-dynamic characteristics, the DSSA is mathematically modelled by considering the fluid flow in chamber and valve in accordance with the hard, transient and soft zone. And the vehicle dynamic characteristic of the DSSA is analysed using quarter car model. To show the effectiveness of the proposed damper, the analysed results of damping characteristics were compared with the experimental results, which showed similar behaviour with the corresponding experimental one. The simulation results of frequency response are compared with the ones of passive shock absorber. From the simulation results of the DSSA, it can be concluded that the ride comfort of the DSSA increased at the low-amplitude road condition and the driving safety was increased partially at the high-amplitude road condition. The results reported herein will provide a better understanding of the shock absorber. Moreover, it is believed that those properties of the results can be utilised in the dynamic design of the automotive system.
Connecting Pore Scale Dynamics to Macroscopic Models for Two-Fluid Phase Flow
NASA Astrophysics Data System (ADS)
McClure, J. E.; Dye, A. L.; Miller, C. T.; Gray, W. G.
2015-12-01
Imaging technologies such as computed micro-tomography (CMT) provide high resolution three-dimensional images of real porous medium systems that reveal the true geometric structure of fluid and solid phases. Simulation and analysis tools are essential to extract knowledge from this raw data, and can be applied in tandem to provide information that is otherwise inaccessible. Guidance from multi-scale averaging theory is used to develop a multi-scale analysis framework to determine phase connectivity and extract interfacial areas, curvatures, common line length, contact angle and the velocities of the interface and common curve. The approach is applied to analyze pore-scale dynamics based on a multiphase lattice Boltzmann method. Dense sets of simulations are performed to evaluate the equilibrium relationship between capillary pressure, saturation and interfacial area for several experimentally imaged porous media. The approach is also used study the evolution of macroscopic quantities under dynamic conditions, which is compared to the equilibrium data.
Numerical Modeling of Three-Dimensional Fluid Flow with Phase Change
NASA Technical Reports Server (NTRS)
Esmaeeli, Asghar; Arpaci, Vedat
1999-01-01
We present a numerical method to compute phase change dynamics of three-dimensional deformable bubbles. The full Navier-Stokes and energy equations are solved for both phases by a front tracking/finite difference technique. The fluid boundary is explicitly tracked by discrete points that are connected by triangular elements to form a front that is used to keep the stratification of material properties sharp and to calculate the interfacial source terms. Two simulations are presented to show robustness of the method in handling complex phase boundaries. In the first case, growth of a vapor bubble in zero gravity is studied where large volume increase of the bubble is managed by adaptively increasing the front resolution. In the second case, growth of a bubble under high gravity is studied where indentation at the rear of the bubble results in a region of large curvature which challenges the front tracking in three dimensions.
Modeling of fiber orientation in viscous fluid flow with application to self-compacting concrete
NASA Astrophysics Data System (ADS)
Kolařík, Filip; Patzák, Bořek
2013-10-01
In recent years, unconventional concrete reinforcement is of growing popularity. Especially fiber reinforcement has very wide usage in high performance concretes like "Self Compacting Concrete" (SCC). The design of advanced tailor-made structures made of SCC can take advantage of anisotropic orientation of fibers. Tools for fiber orientation predictions can contribute to design of tailor made structure and allow to develop casting procedures that enable to achieve the desired fiber distribution and orientation. This paper deals with development and implementation of suitable tool for prediction of fiber orientation in a fluid based on the knowledge of the velocity field. Statistical approach to the topic is employed. Fiber orientation is described by a probability distribution of the fiber angle.
Poiseuille equation for steady flow of fractal fluid
NASA Astrophysics Data System (ADS)
Tarasov, Vasily E.
2016-07-01
Fractal fluid is considered in the framework of continuous models with noninteger dimensional spaces (NIDS). A recently proposed vector calculus in NIDS is used to get a description of fractal fluid flow in pipes with circular cross-sections. The Navier-Stokes equations of fractal incompressible viscous fluids are used to derive a generalization of the Poiseuille equation of steady flow of fractal media in pipe.
Smolarkiewicz, P.K.; Grubisic, V.; Margolin, L.G.
1999-03-31
Traditionally, numerical models for simulating planetary scale weather and climate employ the hydrostatic primitive equations-an abbreviated form of Navier-Stokes equations that neglect vertical accelerations and use simplified inertial forces. 1 Although there is no evidence so far that including nonhydrostatic effects in global models has any physical significance for large scale solutions, there is an apparent trend in the community toward restoring Navier-Stokes equations (or at least their less constrained forms) in global models of atmospheres and oceans. The primary motivation for this is that the state-of-the-art computers already admit resolutions where local nonhydrostatic effects become noticeable. Other advantages include: the convenience of local mesh refinement; better overall accuracy; insubstantial computational overhead relative to hydrostatic models; universality and therefore convenience of maintaining a single large code; as well as conceptual simplicity and mathematical elegancy--features important for education. The few existing nonhydrostatic global models differ in analytic formulation and numerical design, reflecting their different purposes and origins. Much of our present research improves the design of a high-performance numerical model for simulating the flows of moist (and precipitating), rotating, stratified fluids past a specified time-dependent irregular lower boundary. This model is representative of a class of nonhydrostatic atmospheric codes employing the an elastic equations of motion in a terrain-following curvilinear framework, and contains parallel implementations of semi-Lagrangian and Eulerian approximations selectable by the user. The model has been employed in a variety of applications; the quality of results suggest that modern nonoscillatory forward-in-time (NFT) methods are superior to the more traditional centered-in-time-and-space schemes, in terms of accuracy, computational efficiency, flexibility and robustness.
NASA Astrophysics Data System (ADS)
Mortensen, Dag
1999-02-01
A finite-element method model for the time-dependent heat and fluid flows that develop during direct-chill (DC) semicontinuous casting of aluminium ingots is presented. Thermal convection and turbulence are included in the model formulation and, in the mushy zone, the momentum equations are modified with a Darcy-type source term dependent on the liquid fraction. The boundary conditions involve calculations of the air gap along the mold wall as well as the heat transfer to the falling water film with forced convection, nucleate boiling, and film boiling. The mold wall and the starting block are included in the computational domain. In the start-up period of the casting, the ingot domain expands over the starting-block level. The numerical method applies a fractional-step method for the dynamic Navier-Stokes equations and the “streamline upwind Petrov-Galerkin” (SUPG) method for mixed diffusion and convection in the momentum and energy equations. The modeling of the start-up period of the casting is demonstrated and compared to temperature measurements in an AA1050 200×600 mm sheet ingot.
George, David L.; Iverson, Richard M.
2011-01-01
Pore-fluid pressure plays a crucial role in debris flows because it counteracts normal stresses at grain contacts and thereby reduces intergranular friction. Pore-pressure feedback accompanying debris deformation is particularly important during the onset of debrisflow motion, when it can dramatically influence the balance of forces governing downslope acceleration. We consider further effects of this feedback by formulating a new, depth-averaged mathematical model that simulates coupled evolution of granular dilatancy, solid and fluid volume fractions, pore-fluid pressure, and flow depth and velocity during all stages of debris-flow motion. To illustrate implications of the model, we use a finite-volume method to compute one-dimensional motion of a debris flow descending a rigid, uniformly inclined slope, and we compare model predictions with data obtained in large-scale experiments at the USGS debris-flow flume. Predictions for the first 1 s of motion show that increasing pore pressures (due to debris contraction) cause liquefaction that enhances flow acceleration. As acceleration continues, however, debris dilation causes dissipation of pore pressures, and this dissipation helps stabilize debris-flow motion. Our numerical predictions of this process match experimental data reasonably well, but predictions might be improved by accounting for the effects of grain-size segregation.
Piezoelectric energy harvesting in internal fluid flow.
Lee, Hyeong Jae; Sherrit, Stewart; Tosi, Luis Phillipe; Walkemeyer, Phillip; Colonius, Tim
2015-10-14
We consider piezoelectric flow energy harvesting in an internal flow environment with the ultimate goal powering systems such as sensors in deep oil well applications. Fluid motion is coupled to structural vibration via a cantilever beam placed in a converging-diverging flow channel. Two designs were considered for the electromechanical coupling: first; the cantilever itself is a piezoelectric bimorph; second; the cantilever is mounted on a pair of flextensional actuators. We experimentally investigated varying the geometry of the flow passage and the flow rate. Experimental results revealed that the power generated from both designs was similar; producing as much as 20 mW at a flow rate of 20 L/min. The bimorph designs were prone to failure at the extremes of flow rates tested. Finite element analysis (FEA) showed fatigue failure was imminent due to stress concentrations near the bimorph's clamped region; and that robustness could be improved with a stepped-joint mounting design. A similar FEA model showed the flextensional-based harvester had a resonant frequency of around 375 Hz and an electromechanical coupling of 0.23 between the cantilever and flextensional actuators in a vacuum. These values; along with the power levels demonstrated; are significant steps toward building a system design that can eventually deliver power in the Watts range to devices down within a well.
Piezoelectric energy harvesting in internal fluid flow.
Lee, Hyeong Jae; Sherrit, Stewart; Tosi, Luis Phillipe; Walkemeyer, Phillip; Colonius, Tim
2015-01-01
We consider piezoelectric flow energy harvesting in an internal flow environment with the ultimate goal powering systems such as sensors in deep oil well applications. Fluid motion is coupled to structural vibration via a cantilever beam placed in a converging-diverging flow channel. Two designs were considered for the electromechanical coupling: first; the cantilever itself is a piezoelectric bimorph; second; the cantilever is mounted on a pair of flextensional actuators. We experimentally investigated varying the geometry of the flow passage and the flow rate. Experimental results revealed that the power generated from both designs was similar; producing as much as 20 mW at a flow rate of 20 L/min. The bimorph designs were prone to failure at the extremes of flow rates tested. Finite element analysis (FEA) showed fatigue failure was imminent due to stress concentrations near the bimorph's clamped region; and that robustness could be improved with a stepped-joint mounting design. A similar FEA model showed the flextensional-based harvester had a resonant frequency of around 375 Hz and an electromechanical coupling of 0.23 between the cantilever and flextensional actuators in a vacuum. These values; along with the power levels demonstrated; are significant steps toward building a system design that can eventually deliver power in the Watts range to devices down within a well. PMID:26473879
Piezoelectric Energy Harvesting in Internal Fluid Flow
Lee, Hyeong Jae; Sherrit, Stewart; Tosi, Luis Phillipe; Walkemeyer, Phillip; Colonius, Tim
2015-01-01
We consider piezoelectric flow energy harvesting in an internal flow environment with the ultimate goal powering systems such as sensors in deep oil well applications. Fluid motion is coupled to structural vibration via a cantilever beam placed in a converging-diverging flow channel. Two designs were considered for the electromechanical coupling: first; the cantilever itself is a piezoelectric bimorph; second; the cantilever is mounted on a pair of flextensional actuators. We experimentally investigated varying the geometry of the flow passage and the flow rate. Experimental results revealed that the power generated from both designs was similar; producing as much as 20 mW at a flow rate of 20 L/min. The bimorph designs were prone to failure at the extremes of flow rates tested. Finite element analysis (FEA) showed fatigue failure was imminent due to stress concentrations near the bimorph’s clamped region; and that robustness could be improved with a stepped-joint mounting design. A similar FEA model showed the flextensional-based harvester had a resonant frequency of around 375 Hz and an electromechanical coupling of 0.23 between the cantilever and flextensional actuators in a vacuum. These values; along with the power levels demonstrated; are significant steps toward building a system design that can eventually deliver power in the Watts range to devices down within a well. PMID:26473879
Fluid flow in a skewed annulus
Haci, M.; Cartalos, U.
1996-06-01
A novel, realistic treatment of annular flow in an oil well is developed. The fluid flow in an annulus with an inclined or S-shaped inner pipe is considered. The model covers laminar and turbulent flow regimes and the results are experimentally verified. The study predicts axial and angular velocities and frictional pressure losses. The frictional pressure losses are shown to be higher than in the corresponding concentric annulus when the inner pipe is severely S-shaped. However, for typical drilling well geometries, the frictional pressure losses are found to approach the eccentric annular predictions asymptotically. Thus, the study finds the average eccentricity of a vertical or near vertical well, which is a difficult parameter for the engineer to estimate. The results of the study are of practical importance where high annular frictional pressure losses are encountered, such as in slim holes and coiled tubing operations. The frictional pressure losses in complex annular geometries are presented in an easily usable form.
Value for controlling flow of cryogenic fluid
Knapp, Philip A.
1996-01-01
A valve is provided for accurately controlling the flow of cryogenic fluids such as liquid nitrogen. The valve comprises a combination of disc and needle valves affixed to a valve stem in such a manner that the disc and needle are free to rotate about the stem, but are constrained in lateral and vertical movements. This arrangement provides accurate and precise fluid flow control and positive fluid isolation.
Flow properties of the solar wind obtained from white light data and a two-fluid model
NASA Technical Reports Server (NTRS)
Habbal, Shadia Rifai; Esser, Ruth; Guhathakurta, Madhulika; Fisher, Richard
1994-01-01
The flow properties of the solar wind from 1 R(sub s) to 1 AU were obtained using a two fluid model constrained by density and scale height temperatures derived from white light observations, as well as knowledge of the electron temperature in coronal holes. The observations were obtained with the white light coronographs on SPARTAN 201-1 and at Mauna Loa (Hawaii), in a north polar coronal hole from 1.16 to 5.5 R(sub s) on 11 Apr. 1993. By specifying the density, temperature, Alfven wave velocity amplitude and heating function at the coronal base, it was found that the model parameters fit well the constraints of the empirical density profiles and temperatures. The optimal range of the input parameters was found to yield a higher proton temperature than electron temperature in the inner corona. The results indicate that no preferential heating of the protons at larger distances is needed to produce higher proton than electron temperatures at 1 AU, as observed in the high speed solar wind.
Overview of heat transfer and fluid flow problem areas encountered in Stirling engine modeling
NASA Technical Reports Server (NTRS)
Tew, Roy C., Jr.
1988-01-01
NASA Lewis Research Center has been managing Stirling engine development programs for over a decade. In addition to contractual programs, this work has included in-house engine testing and development of engine computer models. Attempts to validate Stirling engine computer models with test data have demonstrated that engine thermodynamic losses need better characterization. Various Stirling engine thermodynamic losses and efforts that are underway to characterize these losses are discussed.
Overview of heat transfer and fluid flow problem areas encountered in stirling engine modeling
Tew, R.C. Jr.
1988-02-01
NASA Lewis Research Center has been managing Stirling engine development programs for over a decade. In addition to contractual programs, this work has included in-house engine testing and development of engine computer models. Attempts to validate Stirling engine computer models with test data have demonstrated that engine thermodynamic losses need better characterization. Various Stirling engine thermodynamic losses and efforts that are underway to characterize these losses are discussed.
NASA Astrophysics Data System (ADS)
Chen, Y.; Valocchi, A. J.; Kohanpur, A. H.; Freiburg, J. T.
2015-12-01
Direct numerical simulation of multiphase flow in porous media is an important tool for understanding pore-scale processes affecting transport and fate of supercritical CO2 in saline reservoirs. The lattice Boltzmann method, based on microscopic models and mesoscopic kinetic equations, is particularly well suited for fluid flow simulations involving interfacial dynamics and complex boundaries. In this study, we compare the Shan-Chen and color-fluid model in lattice Boltzmann simulation of multiphase flow in porous media. The original models were proposed two decades ago, and suffer from significant spurious currents as well as other numerical limitations. Therefore, the latest developments of the two models are employed, which allows consideration of density and viscosity contrasts relevant to geological sequestration in saline reservoirs. Previous studies of the comparison of the two models were mostly done in simple geometries, and demonstrated that the Shan-Chen model suffered from more serious numerical errors than the color-fluid model, although the latter is more computationally demanding. The real impact on multiphase flow in porous media has not been studied in detail. In this investigation, we employ realistic fluid parameters and perform numerical simulations in geometries based on micro-CT images of rock cores. The fluid displacement patterns and the relative permeability obtained by simulations will be used to evaluate the two models. The computational cost of the two models will also be presented for comparison. This work was supported as part of the Center for Geologic Storage of CO2, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science.
Stokes flow of a micropolar fluid past an assemblage of spheroidal particle-in-cell models with slip
NASA Astrophysics Data System (ADS)
Sherief, H. H.; Faltas, M. S.; Ashmawy, E. A.; Nashwan, M. G.
2015-05-01
In a cell model it is assumed that the three-dimensional assemblage may be considered to consist of a number of identical unit cells, each of which contains a particle surrounded by a fluid envelope with a fictitious surface (free surface) containing a volume of fluid sufficient to make the fractional void volume in the cell identical to that in the entire assemblage. The quasi-steady axisymmetric translational motion of a spherical or spheroidal cell of an incompressible micropolar fluid is investigated utilizing the cell model method. The inner particle of the cell is assumed to be solid and the outer to be fictitious. Linear velocity and microrotation slip boundary conditions on the surface of the solid particle are proposed. Normalized mobility is obtained for both spherical and spheroidal particles in the cell model and is represented graphically. Expressions for the superficial fluid velocity through an assemblage of spherical and spheroidal particles are obtained.
Hibi, Yoshihiko; Tomigashi, Akira
2015-09-01
Numerical simulations that couple flow in a surface fluid with that in a porous medium are useful for examining problems of pollution that involve interactions among atmosphere, water, and groundwater, including saltwater intrusion along coasts. Coupled numerical simulations of such problems must consider both vertical flow between the surface fluid and the porous medium and complicated boundary conditions at their interface. In this study, a numerical simulation method coupling Navier-Stokes equations for surface fluid flow and Darcy equations for flow in a porous medium was developed. Then, the basic ability of the coupled model to reproduce (1) the drawdown of a surface fluid observed in square-pillar experiments, using pillars filled with only fluid or with fluid and a porous medium and (2) the migration of saltwater (salt concentration 0.5%) in the porous medium using the pillar filled with fluid and a porous medium was evaluated. Simulations that assumed slippery walls reproduced well the results with drawdowns of 10-30 cm when the pillars were filled with packed sand, gas, and water. Moreover, in the simulation of saltwater infiltration by the method developed in this study, velocity was precisely reproduced because the experimental salt concentration in the porous medium after saltwater infiltration was similar to that obtained in the simulation. Furthermore, conditions across the boundary between the porous medium and the surface fluid were satisfied in these numerical simulations of square-pillar experiments in which vertical flow predominated. Similarly, the velocity obtained by the simulation for a system coupling flow in surface fluid with that in a porous medium when horizontal flow predominated satisfied the conditions across the boundary. Finally, it was confirmed that the present simulation method was able to simulate a practical-scale surface fluid and porous medium system. All of these numerical simulations, however, required a great deal of
NASA Astrophysics Data System (ADS)
Rubino, J. G.; Holliger, K.
2010-12-01
suitable upscaling procedure. This computational procedure emulates a corresponding pertinent laboratory experiment, in which a representative, mesoscopic-scale rock sample is subjected to a time-harmonic compressibility test. The thus observed complex volume change of the probed sample then allows for estimating the equivalent complex plane-wave modulus, which in turn yields the corresponding effective phase velocity and quality factor as functions of frequency. We apply this approach to a range of canonical models of porous media characterized by realistic, highly heterogeneous distributions of the hydraulic and/or elastic properties as well as varying levels of saturation. In particular, we also compare the results of spatially continuous variations of the medium and fluid properties with equivalent binary parameter distributions. Interestingly, preliminary results provide evidence to suggest that for most heterogeneous porous media characterized by spatially continuous variations of the hydraulic and/or elastic properties, the contribution of wave-induced mesoscopic fluid flow effects to the velocity dispersion and attenuation of seismic waves is likely to be of subordinate importance.
Fluid flow through the larynx channel
NASA Astrophysics Data System (ADS)
Miller, J. A.; Pereira, J. C.; Thomas, D. W.
1988-03-01
The classic two-mass model of the larynx channel is extended by including the false vocal folds and the laryngeal ventricle. Several glottis profiles are postulated to exist which are the result of the forces applied to the mucus membrane due to intraglottal pressure variation. These profiles constrain the air flow which allows the formation of one or two "venae contractae". The location of these influences the pressure in the glottis and layrngeal ventricle and also gives rise to additional viscous losses as well as losses due to flow enlargement. Sampled waveforms are calculated from the model for volume velocity, glottal area, Reynolds number and fluid forces over the vocal folds for various profiles. Results show that the computed waveforms agree with physiological data [1,2] and that it is not necessary to use any empirical constants to match the simulation results. Also, the onset of phonation is shown to be possible either with abduction or adduction of the vocal folds.
Visualizing vector field topology in fluid flows
NASA Technical Reports Server (NTRS)
Helman, James L.; Hesselink, Lambertus
1991-01-01
Methods of automating the analysis and display of vector field topology in general and flow topology in particular are discussed. Two-dimensional vector field topology is reviewed as the basis for the examination of topology in three-dimensional separated flows. The use of tangent surfaces and clipping in visualizing vector field topology in fluid flows is addressed.
Fluid flow through packings of rotating obstacles
NASA Astrophysics Data System (ADS)
Oliveira, Rafael S.; Andrade, José S.; Andrade, Roberto F. S.
2015-03-01
We investigate through numerical simulation the nonstationary flow of a Newtonian fluid through a two-dimensional channel filled with an array of circular obstacles of distinct sizes. The disks may rotate around their respective centers, modeling a nonstationary, inhomogeneous porous medium. Obstacle sizes and positions are defined by the geometry of an Apollonian packing (AP). To allow for fluid flow, the radii of the disks are uniformly reduced by a factor 0.6 ≤s ≤0.8 for assemblies corresponding to the four first AP generations. The investigation is targeted to elucidate the main features of the rotating regime as compared to the fixed disk condition. It comprises the evaluation of the region of validity of Darcy's law as well as the study of the nonlinear hydraulic resistance as a function of the channel Reynolds number, the reduction factor s , and the AP generation. Depending on a combination of these factors, the resistance of rotating disks may be larger or smaller than that of the corresponding static case. We also analyze the flow redistribution in the interdisk channels as a result of the rotation pattern and characterize the angular velocity of the disks. Here, the striking feature is the emergence of a stable oscillatory behavior of the angular velocity for almost all disks that are inserted into the assemblies after the second generation.
Saffer, D.M.; Bekins, B.A.
1998-01-01
Down-hole geochemical anomalies encountered in active accretionary systems can be used to constrain the timing, rates, and localization of fluid flow. Here we combine a coupled flow and solute transport model with a kinetic model for smectite dehydration to better understand and quantify fluid flow in the Nankai accretionary complex offshore of Japan. Compaction of sediments and clay dehydration provide fluid sources which drive the model flow system. We explicitly include the consolidation rate of underthrust sediments in our calculations to evaluate the impact that variations in this unknown quantity have on pressure and chloride distribution. Sensitivity analysis of steady state pressure solutions constrains bulk and flow conduit permeabilities. Steady state simulations with 30% smectite in the incoming sedimentary sequence result in minimum chloride concentrations at site 808 of 550 mM, but measured chlorinity is as low as 447 mM. We simulate the transient effects of hydrofracture or a strain event by assuming an instantaneous permeability increase of 3-4 orders of magnitude along a flow conduit (in this case the de??collement), using steady state results as initial conditions. Transient results with an increase in de??collement permeability from 10-16 m2 to 10-13 m2 and 20% smectite reproduce the observed chloride profile at site 808 after 80-160 kyr. Modeled chloride concentrations are highly sensitive to the consolidation rate of underthrust sediments, such that rapid compaction of underthrust material leads to increased freshening. Pressures within the de??collement during transient simulations rise rapidly to a significant fraction of lithostatic and remain high for at least 160 kyr, providing a mechanism for maintaining high permeability. Flow rates at the deformation front for transient simulations are in good agreement with direct measurements, but steady state flow rates are 2-3 orders of magnitude smaller than observed. Fluid budget calculations
Method and Apparatus for Measuring Fluid Flow
NASA Technical Reports Server (NTRS)
Arndt, G. Dickey (Inventor); Nguyen, Thanh X. (Inventor); Carl, James R. (Inventor)
1997-01-01
Method and apparatus for making measurements on fluids related to their complex permeability are disclosed. A microwave probe is provided for exposure to the fluids. The probe can be non-intrusive or can also be positioned at the location where measurements are to be made. The impedance of the probe is determined. in part. by the complex dielectric constant of the fluids at the probe. A radio frequency signal is transmitted to the probe and the reflected signal is phase and amplitude detected at a rapid rate for the purpose of identifying the fluids. Multiple probes may be selectively positioned to monitor the behavior of the fluids including their flow rate. Fluids may be identified as between two or more different fluids as well as multiple phases of the same fluid based on differences between their complex permittivities.
Debris-flow deposition: Effects of pore-fluid pressure and friction concentrated at flow margins
Major, J.J.; Iverson, R.M.
1999-01-01
Measurements of pore-fluid pressure and total bed-normal stress at the base of several ???10 m3 experimental debris flows provide new insight into the process of debris-flow deposition. Pore-fluid pressures nearly sufficient to cause liquefaction were developed and maintained during flow mobilization and acceleration, persisted in debris-flow interiors during flow deceleration and deposition, and dissipated significantly only during postdepositional sediment consolidation. In contrast, leading edges of debris flows exhibited little or no positive pore-fluid pressure. Deposition therefore resulted from grain-contact friction and bed friction concentrated at flow margins. This finding contradicts models that invoke widespread decay of excess pore-fluid pressure, uniform viscoplastic yield strength, or pervasive grain-collision stresses to explain debris-flow deposition. Furthermore, the finding demonstrates that deposit thickness cannot be used to infer the strength of flowing debris.
Focused fluid flow in passive continental margins.
Berndt, Christian
2005-12-15
Passive continental margins such as the Atlantic seaboard of Europe are important for society as they contain large energy resources, and they sustain ecosystems that are the basis for the commercial fish stock. The margin sediments are very dynamic environments. Fluids are expelled from compacting sediments, bottom water temperature changes cause gas hydrate systems to change their locations and occasionally large magmatic intrusions boil the pore water within the sedimentary basins, which is then expelled to the surface. The fluids that seep through the seabed at the tops of focused fluid flow systems have a crucial role for seabed ecology, and study of such fluid flow systems can also help in predicting the distribution of hydrocarbons in the subsurface and deciphering the climate record. Therefore, the study of focused fluid flow will become one of the most important fields in marine geology in the future.
Unified slip boundary condition for fluid flows.
Thalakkottor, Joseph John; Mohseni, Kamran
2016-08-01
Determining the correct matching boundary condition is fundamental to our understanding of several everyday problems. Despite over a century of scientific work, existing velocity boundary conditions are unable to consistently explain and capture the complete physics associated with certain common but complex problems, such as moving contact lines and corner flows. The widely used Maxwell and Navier slip boundary conditions make an implicit assumption that velocity varies only in the wall normal direction. This makes their boundary condition inapplicable in the vicinity of contact lines and corner points, where velocity gradient exists both in the wall normal and wall tangential directions. In this paper, by identifying this implicit assumption we are able to extend Maxwell's slip model. Here, we present a generalized velocity boundary condition that shows that slip velocity is a function of not only the shear rate but also the linear strain rate. In addition, we present a universal relation for slip length, which shows that, for a general flow, slip length is a function of the principal strain rate. The universal relation for slip length along with the generalized velocity boundary condition provides a unified slip boundary condition to model a wide range of steady Newtonian fluid flows. We validate the unified slip boundary for simple Newtonian liquids by using molecular dynamics simulations and studying both the moving contact line and corner flow problems. PMID:27627398
Unified slip boundary condition for fluid flows
NASA Astrophysics Data System (ADS)
Thalakkottor, Joseph John; Mohseni, Kamran
2016-08-01
Determining the correct matching boundary condition is fundamental to our understanding of several everyday problems. Despite over a century of scientific work, existing velocity boundary conditions are unable to consistently explain and capture the complete physics associated with certain common but complex problems, such as moving contact lines and corner flows. The widely used Maxwell and Navier slip boundary conditions make an implicit assumption that velocity varies only in the wall normal direction. This makes their boundary condition inapplicable in the vicinity of contact lines and corner points, where velocity gradient exists both in the wall normal and wall tangential directions. In this paper, by identifying this implicit assumption we are able to extend Maxwell's slip model. Here, we present a generalized velocity boundary condition that shows that slip velocity is a function of not only the shear rate but also the linear strain rate. In addition, we present a universal relation for slip length, which shows that, for a general flow, slip length is a function of the principal strain rate. The universal relation for slip length along with the generalized velocity boundary condition provides a unified slip boundary condition to model a wide range of steady Newtonian fluid flows. We validate the unified slip boundary for simple Newtonian liquids by using molecular dynamics simulations and studying both the moving contact line and corner flow problems.
Thermohydrodynamic analysis of cryogenic liquid turbulent flow fluid film bearings
NASA Technical Reports Server (NTRS)
Andres, Luis San
1993-01-01
A thermohydrodynamic analysis is presented and a computer code developed for prediction of the static and dynamic force response of hydrostatic journal bearings (HJB's), annular seals or damper bearing seals, and fixed arc pad bearings for cryogenic liquid applications. The study includes the most important flow characteristics found in cryogenic fluid film bearings such as flow turbulence, fluid inertia, liquid compressibility and thermal effects. The analysis and computational model devised allow the determination of the flow field in cryogenic fluid film bearings along with the dynamic force coefficients for rotor-bearing stability analysis.
Fluid flow dynamics in MAS systems.
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. PMID:26073599
NASA Astrophysics Data System (ADS)
Karapetsas, George; Tsamopoulos, John
2013-09-01
During extrusion of viscoelastic fluids various flow instabilities may arise resulting in a distorted free surface. In order to investigate the factors generating these instabilities we performed a linear stability analysis at zero Reynolds number around the steady solution of the cylindrical or planar stick-slip flow for a viscoelastic fluid following the affine exponential Phan-Thien Tanner (PTT) model. Stick-slip flow is an important special case of the extrudate swell problem, since the latter reduces to it in the limit of infinite surface tension but avoids the complications of a free-boundary flow. The linear stability analysis is performed for various values of the rheological parameters of the PTT model in order to determine the effects of all material properties. It is found that the flow becomes unstable as the Weissenberg number increases above a critical value, due to a Hopf bifurcation suggesting that the flow will become periodic in time. Both the critical value of the Weissenberg number and the frequency of the instability depend strongly on the rheological parameters of the viscoelastic model. The corresponding eigenvectors indicate that the perturbed flow field has a spatially periodic structure, initiated at the rim of the die, extending for up to 5-7 die gaps downstream, but confined close to the surface of the extrudate, in qualitative agreement with existing experiments. This suggests that instability is generated by the combination of the singularity in the velocity and stress fields at the die lip and the strong extension that the extruded polymer undergoes near its surface. The elasticity alone can be responsible for the appearance of instabilities in the extrusion process of viscoelastic fluids and the often used assumptions of wall slip or compressibility, although they might be present, are not required. Finally, the mechanisms that produce these instabilities are examined through energy analysis of the disturbance flow.
Two-Fluid Equilibrium for Transonic Poloidal Flows
NASA Astrophysics Data System (ADS)
Guazzotto, Luca; Betti, Riccardo
2012-03-01
Much analytical and numerical work has been done in the past on ideal MHD equilibrium in the presence of macroscopic flow. In recent years, several authors have worked on equilibrium formulations for a two-fluid system, in which inertial ions and massless electrons are treated as distinct fluids. In this work, we present our approach to the formulation of the two-fluid equilibrium problem. Particular attention is given to the relation between the two-fluid equations and the equilibrium equations for the single-fluid ideal MHD system. Our purpose is to reconsider the results of one-fluid calculation with the more accurate two-fluid model, referring in particular to the so-called transonic discontinuities, which occur when the poloidal velocity spans a range crossing the poloidal sound speed (i.e., the sound speed reduced by a factor Bp/B). It is expected that the one-fluid discontinuity will be resolved into a sharp gradient region by the two-fluid model. Also, contrary to the ideal MHD case, in the two-fluid model the equations governing the equilibrium are elliptic in the whole range of interest for transonic equilibria. The numerical solution of the two-fluid system of equations is going to be based on a code built on the structure of the existing ideal-MHD code FLOW.
Faybishenko, B.
1997-10-01
'Understanding subsurface flow and transport processes is critical for effective assessment, decision-making, and remediation activities for contaminated sites. However, for fluid flow and contaminant transport through fractured vadose zones, traditional hydrogeological approaches are often found to be inadequate. In this project, the authors examine flow and transport through a fractured vadose zone as a deterministic chaotic dynamical process, and develop a model of it in these terms. Initially, they examine separately the geometric model of fractured rock and the flow dynamics model needed to describe chaotic behavior. Ultimately they will put the geometry and flow dynamics together to develop a chaotic-dynamical model of flow and transport in a fractured vadose zone. They investigate water flow and contaminant transport on several scales, ranging from small-scale laboratory experiments in fracture replicas and fractured cores, to field experiments conducted in a single exposed fracture at a basalt outcrop, and finally to a ponded infiltration test using a pond of 7 by 8 m. In the field experiments, the authors measure the time-variation of water flux, moisture content, and hydraulic head at various locations, as well as the total inflow rate to the subsurface. Such variations reflect the changes in the geometry and physics of water flow that display chaotic behavior, which the authors try to reconstruct using the data obtained. In the analysis of experimental data, a chaotic model can be used to predict the long-term bounds on fluid flow and transport behavior, known as the attractor of the system, and to examine the limits of short-term predictability within these bounds. This approach is especially well suited to the need for short-term predictions to support remediation decisions and long-term bounding studies.'
NASA Astrophysics Data System (ADS)
Robl, Jörg; Hergarten, Stefan
2015-04-01
Debris flows are globally abundant threats for settlements and infrastructure in mountainous regions. Crucial influencing factors for hazard zone planning and mitigation strategies are based on numerical models that describe granular flow on general topography by solving a depth-averaged form of the Navier Stokes equations in combination with an appropriate flow resistance law. In case of debris flows, the Voellmy rheology is a widely used constitutive law describing the flow resistance. It combines a velocity independent Coulomb friction term with a term proportional to the square of the velocity as it is commonly used for turbulent flow. Parameters of the Vollemy fluid are determined by back analysis from observed events so that modelled events mimic their historical counterparts. Determined parameters characterizing individual debris flows show a large variability (related to fluid composition and surface roughness). However, there may be several sets of parameters that lead to a similar depositional pattern but cause large differences in flow velocity and momentum along the flow path. Fluid volumes of hazardous debris flows are estimated by analyzing historic events, precipitation time series, hydrographs or empirical relationships that correlate fluid volumes and drainage areas of torrential catchments. Beside uncertainties in the determination of the fluid volume the position and geometry of the initial masses of forthcoming debris flows are in general not well constrained but heavily influence the flow dynamics and the depositional pattern even in the run-out zones. In this study we present a new, freely available numerical description of rapid mass movements based on the GERRIS framework and early results of a Monte Carlo simulation exploring effects of the aforementioned parameters on run-out distance, inundated area and momentum. The novel numerical model describes rapid mass movements on complex topography using the shallow water equations in Cartesian
Engineering fluid flow using sequenced microstructures.
Amini, Hamed; Sollier, Elodie; Masaeli, Mahdokht; Xie, Yu; Ganapathysubramanian, Baskar; Stone, Howard A; Di Carlo, Dino
2013-01-01
Controlling the shape of fluid streams is important across scales: from industrial processing to control of biomolecular interactions. Previous approaches to control fluid streams have focused mainly on creating chaotic flows to enhance mixing. Here we develop an approach to apply order using sequences of fluid transformations rather than enhancing chaos. We investigate the inertial flow deformations around a library of single cylindrical pillars within a microfluidic channel and assemble these net fluid transformations to engineer fluid streams. As these transformations provide a deterministic mapping of fluid elements from upstream to downstream of a pillar, we can sequentially arrange pillars to apply the associated nested maps and, therefore, create complex fluid structures without additional numerical simulation. To show the range of capabilities, we present sequences that sculpt the cross-sectional shape of a stream into complex geometries, move and split a fluid stream, perform solution exchange and achieve particle separation. A general strategy to engineer fluid streams into a broad class of defined configurations in which the complexity of the nonlinear equations of fluid motion are abstracted from the user is a first step to programming streams of any desired shape, which would be useful for biological, chemical and materials automation.
Engineering fluid flow using sequenced microstructures
NASA Astrophysics Data System (ADS)
Amini, Hamed; Sollier, Elodie; Masaeli, Mahdokht; Xie, Yu; Ganapathysubramanian, Baskar; Stone, Howard A.; di Carlo, Dino
2013-05-01
Controlling the shape of fluid streams is important across scales: from industrial processing to control of biomolecular interactions. Previous approaches to control fluid streams have focused mainly on creating chaotic flows to enhance mixing. Here we develop an approach to apply order using sequences of fluid transformations rather than enhancing chaos. We investigate the inertial flow deformations around a library of single cylindrical pillars within a microfluidic channel and assemble these net fluid transformations to engineer fluid streams. As these transformations provide a deterministic mapping of fluid elements from upstream to downstream of a pillar, we can sequentially arrange pillars to apply the associated nested maps and, therefore, create complex fluid structures without additional numerical simulation. To show the range of capabilities, we present sequences that sculpt the cross-sectional shape of a stream into complex geometries, move and split a fluid stream, perform solution exchange and achieve particle separation. A general strategy to engineer fluid streams into a broad class of defined configurations in which the complexity of the nonlinear equations of fluid motion are abstracted from the user is a first step to programming streams of any desired shape, which would be useful for biological, chemical and materials automation.
Laminar flow of two miscible fluids in a simple network
NASA Astrophysics Data System (ADS)
Karst, Casey M.; Storey, Brian D.; Geddes, John B.
2013-03-01
When a fluid comprised of multiple phases or constituents flows through a network, nonlinear phenomena such as multiple stable equilibrium states and spontaneous oscillations can occur. Such behavior has been observed or predicted in a number of networks including the flow of blood through the microcirculation, the flow of picoliter droplets through microfluidic devices, the flow of magma through lava tubes, and two-phase flow in refrigeration systems. While the existence of nonlinear phenomena in a network with many inter-connections containing fluids with complex rheology may seem unsurprising, this paper demonstrates that even simple networks containing Newtonian fluids in laminar flow can demonstrate multiple equilibria. The paper describes a theoretical and experimental investigation of the laminar flow of two miscible Newtonian fluids of different density and viscosity through a simple network. The fluids stratify due to gravity and remain as nearly distinct phases with some mixing occurring only by diffusion. This fluid system has the advantage that it is easily controlled and modeled, yet contains the key ingredients for network nonlinearities. Experiments and 3D simulations are first used to explore how phases distribute at a single T-junction. Once the phase separation at a single junction is known, a network model is developed which predicts multiple equilibria in the simplest of networks. The existence of multiple stable equilibria is confirmed experimentally and a criterion for existence is developed. The network results are generic and could be applied to or found in different physical systems.
Lattice Boltzmann methods for viscous fluid flows and for two-phase fluid flows
NASA Astrophysics Data System (ADS)
Inamuro, Takaji
2006-09-01
Lattice Boltzmann methods (LBMs) for viscous fluid flows and for two-phase fluid flows are presented. First, the LBMs for incompressible viscous fluid flows and for temperature fields are described. Then, we derive a lattice kinetic scheme (LKS) which is an improved scheme of the LBM. The LKS does not require any velocity distribution functions and is more stable than the LBMs. In addition, the LBM for two-phase fluid flows is presented. The method can simulate flows with the density ratio up to 1000. Numerical examples of unsteady flows in a three-dimensional porous structure, binary droplet collision and rising bubbles in a square duct are illustrated. It is expected that the LBMs (and LKS) will become promising numerical schemes for simulating complex fluid flows.
Apparatus for measuring fluid flow
Smith, J.E.; Thomas, D.G.
Flow measuring apparatus includes a support loop having strain gages mounted thereon and a drag means which is attached to one end of the support loop and which bends the sides of the support loop and induces strains in the strain gages when a flow stream impacts thereon.
Apparatus for measuring fluid flow
Smith, Jack E.; Thomas, David G.
1984-01-01
Flow measuring apparatus includes a support loop having strain gages mounted thereon and a drag means which is attached to one end of the support loop and which bends the sides of the support loop and induces strains in the strain gages when a flow stream impacts thereon.
Directed flow fluid rinse trough
Kempka, S.N.; Walters, R.N.
1996-07-02
Novel rinse troughs accomplish thorough uniform rinsing. The tanks are suitable for one or more essentially planar items having substantially the same shape. The troughs ensure that each surface is rinsed uniformly. The new troughs also require less rinse fluid to accomplish a thorough rinse than prior art troughs. 9 figs.
Directed flow fluid rinse trough
Kempka, Steven N.; Walters, Robert N.
1996-01-01
Novel rinse troughs accomplish thorough uniform rinsing. The tanks are suitable for one or more essentially planar items having substantially the same shape. The troughs ensure that each surface is rinsed uniformly. The new troughs also require less rinse fluid to accomplish a thorough rinse than prior art troughs.
Hanna, S R; Brown, M J; Camelli, F E; Chan, S T; Coirier, W J; Hansen, O R; Huber, A H; Kim, S; Reynolds, R M
2006-03-06
Computational Fluid Dynamics (CFD) model simulations of urban boundary layers have improved so that they are useful in many types of flow and dispersion analyses. The study described here is intended to assist in planning emergency response activities related to releases of chemical or biological agents into the atmosphere in large cities such as New York City. Five CFD models (CFD-Urban, FLACS, FEM3MP, FEFLO-Urban, and Fluent-Urban) have been applied by five independent groups to the same 3-D building data and geographic domain in Manhattan, using approximately the same wind input conditions. Wind flow observations are available from the Madison Square Garden March 2005 (MSG05) field experiment. It is seen from the many side-by-side comparison plots that the CFD models simulations of near-surface wind fields generally agree with each other and with field observations, within typical atmospheric uncertainties of a factor of two. The qualitative results shown here suggest, for example, that transport of a release at street level in a large city could reach a few blocks in the upwind and crosswind directions. There are still key differences seen among the models for certain parts of the domain. Further quantitative examinations of differences among the models and the observations are necessary to understand causal relationships.
Prodanov, L; Semeins, C M; van Loon, J J W A; te Riet, J; Jansen, J A; Klein-Nulend, J; Walboomers, X F
2013-05-01
Introducing nanoroughness on various biomaterials has been shown to profoundly effect cell-material interactions. Similarly, physical forces act on a diverse array of cells and tissues. Particularly in bone, the tissue experiences compressive or tensile forces resulting in fluid shear stress. The current study aimed to develop an experimental setup for bone cell behavior, combining a nanometrically grooved substrate (200 nm wide, 50 nm deep) mimicking the collagen fibrils of the extracellular matrix, with mechanical stimulation by pulsatile fluid flow (PFF). MC3T3-E1 osteoblast-like cells were assessed for morphology, expression of genes involved in cell attachment and osteoblastogenesis and nitric oxide (NO) release. The results showed that both nanotexture and PFF did affect cellular morphology. Cells aligned on nanotexture substrate in a direction parallel to the groove orientation. PFF at a magnitude of 0.7 Pa was sufficient to induce alignment of cells on a smooth surface in a direction perpendicular to the applied flow. When environmental cues texture and flow were interacting, PFF of 1.4 Pa applied parallel to the nanogrooves initiated significant cellular realignment. PFF increased NO synthesis 15-fold in cells attached to both smooth and nanotextured substrates. Increased collagen and alkaline phosphatase mRNA expression was observed on the nanotextured substrate, but not on the smooth substrate. Furthermore, vinculin and bone sialoprotein were up-regulated after 1 h of PFF stimulation. In conclusion, the data show that interstitial fluid forces and structural cues mimicking extracellular matrix contribute to the final bone cell morphology and behavior, which might have potential application in tissue engineering.
Akbarzadeh, Pooria
2016-04-01
In this paper, the unsteady pulsatile magneto-hydrodynamic blood flows through porous arteries concerning the influence of externally imposed periodic body acceleration and a periodic pressure gradient are numerically simulated. Blood is taken into account as the third-grade non-Newtonian fluid. Besides the numerical solution, for small Womersley parameter (such as blood flow through arterioles and capillaries), the analytical perturbation method is used to solve the nonlinear governing equations. Consequently, analytical expressions for the velocity profile, wall shear stress, and blood flow rate are obtained. Excellent agreement between the analytical and numerical predictions is evident. Also, the effects of body acceleration, magnetic field, third-grade non-Newtonian parameter, pressure gradient, and porosity on the flow behaviors are examined. Some important conclusions are that, when the Womersley parameter is low, viscous forces tend to dominate the flow, velocity profiles are parabolic in shape, and the center-line velocity oscillates in phase with the driving pressure gradient. In addition, by increasing the pressure gradient, the mean value of the velocity profile increases and the amplitude of the velocity remains constant. Also, when non-Newtonian effect increases, the amplitude of the velocity profile.
Akbarzadeh, Pooria
2016-04-01
In this paper, the unsteady pulsatile magneto-hydrodynamic blood flows through porous arteries concerning the influence of externally imposed periodic body acceleration and a periodic pressure gradient are numerically simulated. Blood is taken into account as the third-grade non-Newtonian fluid. Besides the numerical solution, for small Womersley parameter (such as blood flow through arterioles and capillaries), the analytical perturbation method is used to solve the nonlinear governing equations. Consequently, analytical expressions for the velocity profile, wall shear stress, and blood flow rate are obtained. Excellent agreement between the analytical and numerical predictions is evident. Also, the effects of body acceleration, magnetic field, third-grade non-Newtonian parameter, pressure gradient, and porosity on the flow behaviors are examined. Some important conclusions are that, when the Womersley parameter is low, viscous forces tend to dominate the flow, velocity profiles are parabolic in shape, and the center-line velocity oscillates in phase with the driving pressure gradient. In addition, by increasing the pressure gradient, the mean value of the velocity profile increases and the amplitude of the velocity remains constant. Also, when non-Newtonian effect increases, the amplitude of the velocity profile. PMID:26792174
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.
Physical ecology of fluid flow sensing in arthropods.
Casas, Jérôme; Dangles, Olivier
2010-01-01
Terrestrial and aquatic arthropods sense fluid flow in many behavioral and ecological contexts, using dedicated, highly sensitive mechanosensory hairs, which are often abundant. Strong similarities exist in the biomechanics of flow sensors and in the sensory ecology of insects, arachnids, and crustaceans in their respective fluid environments. We extend these considerations to flow in sand and its implications for flow sensing by arthropods inhabiting this granular medium. Finally, we highlight the need to merge the various findings of studies that have focused on different arthropods in different fluids. This could be achieved using the unique combination, for sensory ecology, of both a workable and well-accepted mathematical model for hair-based flow sensing, both in air and water, and microelectronic mechanical systems microtechnology to tinker with physical models.
Instrument continuously measures density of flowing fluids
NASA Technical Reports Server (NTRS)
Jacobs, R. B.; Macinko, J.; Miller, C. E.
1967-01-01
Electromechanical densitometer continuously measures the densities of either single-phase or two-phase flowing cryogenic fluids. Measurement is made on actual flow. The instrument operates on the principle that the mass of any vibrating system is a primary factor in determining the dynamic characteristics of the system.
Standardization of Thermo-Fluid Modeling in Modelica.Fluid
Franke, Rudiger; Casella, Francesco; Sielemann, Michael; Proelss, Katrin; Otter, Martin; Wetter, Michael
2009-09-01
This article discusses the Modelica.Fluid library that has been included in the Modelica Standard Library 3.1. Modelica.Fluid provides interfaces and basic components for the device-oriented modeling of onedimensional thermo-fluid flow in networks containing vessels, pipes, fluid machines, valves and fittings. A unique feature of Modelica.Fluid is that the component equations and the media models as well as pressure loss and heat transfer correlations are decoupled from each other. All components are implemented such that they can be used for media from the Modelica.Media library. This means that an incompressible or compressible medium, a single or a multiple substance medium with one or more phases might be used with one and the same model as long as the modeling assumptions made hold. Furthermore, trace substances are supported. Modeling assumptions can be configured globally in an outer System object. This covers in particular the initialization, uni- or bi-directional flow, and dynamic or steady-state formulation of mass, energy, and momentum balance. All assumptions can be locally refined for every component. While Modelica.Fluid contains a reasonable set of component models, the goal of the library is not to provide a comprehensive set of models, but rather to provide interfaces and best practices for the treatment of issues such as connector design and implementation of energy, mass and momentum balances. Applications from various domains are presented.
Electromagnetic probe technique for fluid flow measurements
NASA Technical Reports Server (NTRS)
Arndt, G. D.; Carl, J. R.
1994-01-01
The probes described herein, in various configurations, permit the measurement of the volume fraction of two or more fluids flowing through a pipe. Each probe measures the instantaneous relative dielectric constant of the fluid in immediate proximity. As long as separation of the relative dielectric constant of the fluid is possible, several or even many fluids can be measured in the same flow stream. By using multiple probes, the velocity of each fluid can generally be determined as well as the distribution of each constituent in the pipe. The values are determined by statistical computation. There are many potential applications for probes of this type in industry and government. Possible NASA applications include measurements of helium/hydrazine flow during rocket tests at White Sands, liquid/gas flow in hydrogen or oxygen lines in Orbiter engines, and liquid/gaseous Freon flow in zero gravity tests with the KS135 aircraft at JSC. Much interest has been shown recently by the oil industry. In this a good method is needed to measure the fractions of oil, water, and natural gas flowing in a pipeline and the velocity of each. This particular problem involves an extension of what has been developed to date and our plans to solve this problem will be discussed herein.
Electromagnetic Probe Technique for Fluid Flow Measurements
NASA Technical Reports Server (NTRS)
Arndt, G. D.; Carl, J. R.; Nguyen, T. X.
1994-01-01
The probes described herein, in various configurations, permit the measurement of the volume fraction of two or more fluids flowing through a pipe. Each probe measures the instantaneous relative dielectric constant of the fluid in immediate proximity. As long as separation of the relative dielectric constants of each fluid is possible, several or even many fluids can be measured in the same flow steam. By using multiple probes, the velocity of each fluid can generally be determined as well as the distribution of each constituent in the pipe. The values are determined by statistical computation. There are many potential applications for probes of this type in industry and government. Possible NASA applications include measurements of helium/hydrazine flow during rocket tests at White Sands, liquid/gas flow in hydrogen or oxygen lines in Orbiter engines, and liquid/gaseous Freon flow in zero gravity tests with the KS135 aircraft at JSC. Much interest has been shown recently by the oil industry. In this industry, a good method is needed to measure the fractions of oil, water, and natural gas flowing in a pipeline and the velocity of each. This particular problem involves an extension of what has been developed to date and our plans and program to solve this problem will be discussed herein.
Fluid flow and chemical reaction kinetics in metamorphic systems
Lasaga, A.C.; Rye, D.M. )
1993-05-01
The treatment and effects of chemical reaction kinetics during metamorphism are developed along with the incorporation of fluid flow, diffusion, and thermal evolution. The interplay of fluid flow and surface reaction rates, the distinction between steady state and equilibrium, and the possible overstepping of metamorphic reactions are discussed using a simple analytic model. This model serves as an introduction to the second part of the paper, which develops a reaction model that solves the coupled temperature-fluid flow-chemical composition differential equations relevant to metamorphic processes. Consideration of stable isotopic evidence requires that such a kinetic model be considered for the chemical evolution of a metamorphic aureole. A general numerical scheme is discussed to handle the solution of the model. The results of this kinetic model allow us to reach several important conclusions regarding the factors controlling the chemical evolution of mineral assemblages during a metamorphic event. 41 refs., 19 figs., 5 tabs.
Drift flux model as approximation of two fluid model for two phase dispersed and slug flow in tube
Nigmatulin, R.I.
1995-09-01
The analysis of one-dimensional schematizing for non-steady two-phase dispersed and slug flow in tube is presented. Quasi-static approximation, when inertia forces because of the accelerations of the phases may be neglected, is considered. Gas-liquid bubbly and slug vertical upward flows are analyzed. Non-trivial theoretical equations for slip velocity for these flows are derived. Juxtaposition of the derived equations for slip velocity with the famous Zuber-Findlay correlation as cross correlation coefficients is criticized. The generalization of non-steady drift flux Wallis theory taking into account influence of wall friction on the bubbly or slug flows for kinematical waves is considered.
Heat transfer and fluid flow in microchannels
NASA Astrophysics Data System (ADS)
Mala, Ghulam Mohiuddin
Fluid flow and heat transfer characteristics in microchannels of different cross-sections; parallel plate, cylindrical and trapezoidal microchannels were studied. The trapezoidal microchannels were etched in silicon and glass by photolithographic techniques. The cylindrical microchannels of fused silica and stainless steel were readily available. Channels with depths of 18 μm to 300 μm were studied. The study was divided into three parts viz. theoretical modeling, numerical simulation and experimentation. Electrokinetic effects such as the effects of electrical double layer (EDL) at the solid-liquid interface and surface roughness effects were considered. An experimental apparatus was constructed and a procedure devised to measure the flow rate, pressure drop, temperatures and electrokinetic parameters like streaming potential, streaming current, and conductivity of the working fluid. Great care was taken so that the measurements were accurate and repeatable. For steady state laminar flow and heat transfer in microchannels, mathematical models were developed that consider the effects of electrical double layer and surface roughness at the microchannel walls. The non- linear, 2-D, Poisson-Boltzmann equation that describes the potential distribution at the solid liquid interface was solved numerically and results were compared with a linear approximate solution that overestimates the potential distribution for higher values of zeta potential. Effects of the EDL field at the solid-liquid interface, surface roughness at the microchannel walls and the channel size, on the velocity distribution, streaming potential, apparent viscosity, temperature distribution and heat transfer characteristics are discussed. The experimental results indicate significant departure in flow characteristics from the predictions of the Navier-Stokes equations, referred to as conventional theory. The difference between the experimental results and theoretical predictions decreases as the
Destabilization of confined granular packings due to fluid flow
NASA Astrophysics Data System (ADS)
Monloubou, Martin; Sandnes, Bjørnar
2016-04-01
Fluid flow through granular materials can cause fluidization when fluid drag exceeds the frictional stress within the packing. Fluid driven failure of granular packings is observed in both natural and engineered settings, e.g. soil liquefaction and flowback of proppants during hydraulic fracturing operations. We study experimentally the destabilization and flow of an unconsolidated granular packing subjected to a point source fluid withdrawal using a model system consisting of a vertical Hele-Shaw cell containing a water-grain mixture. The fluid is withdrawn from the cell at a constant rate, and the emerging flow patterns are imaged in time-lapse mode. Using Particle Image Velocimetry (PIV), we show that the granular flow gets localized in a narrow channel down the center of the cell, and adopts a Gaussian velocity profile similar to those observed in dry grain flows in silos. We investigate the effects of the experimental parameters (flow rate, grain size, grain shape, fluid viscosity) on the packing destabilization, and identify the physical mechanisms responsible for the observed complex flow behaviour.
NASA Technical Reports Server (NTRS)
Stier, Bernd; Falco, R. E.
1994-01-01
Optical measurements on an axisymmetrical quartz component engine research model were made to evaluate the flow field encountered during induction. The measurement technique is LIPA (Laser Induced Photochemical Anemometry), a non-intrusive velocimetry concept that provides an investigator of fluid flow with a tool to attain planar information about three-dimensional velocity and vorticity vectors in a single measurement step. The goal of this investigation is to further develop this measurement technique and apply it to study the induction stroke of a water analog model of a four-stroke internal combustion engine. The research conducted in the water analog model is a fundamental scientific inquiry into the flow fields that develop in the induction stroke of an engine at idling engine speeds. As this is the first investigation of its kind using LIPA technique, our goal has been to quantify, in a preliminary manner, the flow field features that develop during the intake stroke. In the process a more comprehensive understanding of the flow field features was developed, and tied to the quantification. The study evaluated the flow field of the intake stroke by estimating fields of velocity and vorticity. On the basis of these data, information about fluid dynamics during induction at engine speeds of 10, 20, and 30 RPM (corresponding to 170, 340, and 510 RPM respectively, when air is the flowing medium) for three different valve lifts was obtained. The overall development of the flow field, its energy content (kinetic, fluctuation) for the different settings of the engine parameters, vorticity information, and cyclic variations have been quantified. These have been discussed in terms of mixing performance.
Analytical solution of two-fluid electro-osmotic flows of viscoelastic fluids.
Afonso, A M; Alves, M A; Pinho, F T
2013-04-01
This paper presents an analytical model that describes a two-fluid electro-osmotic flow of stratified fluids with Newtonian or viscoelastic rheological behavior. This is the principle of operation of an electro-osmotic two-fluid pump as proposed by Brask et al. [Tech. Proc. Nanotech., 1, 190-193, 2003], in which an electrically non-conducting fluid is transported by the interfacial dragging viscous force of a conducting fluid that is driven by electro-osmosis. The electric potential in the conducting fluid and the analytical steady flow solution of the two-fluid electro-osmotic stratified flow in a planar microchannel are presented by assuming a planar interface between the two immiscible fluids with Newtonian or viscoelastic rheological behavior. The effects of fluid rheology, shear viscosity ratio, holdup and interfacial zeta potential are analyzed to show the viability of this technique, where an enhancement of the flow rate is observed as the shear-thinning effects are increased.
Anwar, Md Rajib; Camarda, Kyle V; Kieweg, Sarah L
2015-06-25
Topically applied microbicide gels can provide a self-administered and effective strategy to prevent sexually transmitted infections (STIs). We have investigated the interplay between vaginal tissue elasticity and the yield-stress of non-Newtonian fluids during microbicide deployment. We have developed a mathematical model of tissue deformation driven spreading of microbicidal gels based on thin film lubrication approximation and demonstrated the effect of tissue elasticity and fluid yield-stress on the spreading dynamics. Our results show that both elasticity of tissue and yield-stress rheology of gel are strong determinants of the coating behavior. An optimization framework has been demonstrated which leverages the flow dynamics of yield-stress fluid during deployment to maximize retention while reaching target coating length for a given tissue elasticity. PMID:25798760
Anwar, Md Rajib; Camarda, Kyle V; Kieweg, Sarah L
2015-06-25
Topically applied microbicide gels can provide a self-administered and effective strategy to prevent sexually transmitted infections (STIs). We have investigated the interplay between vaginal tissue elasticity and the yield-stress of non-Newtonian fluids during microbicide deployment. We have developed a mathematical model of tissue deformation driven spreading of microbicidal gels based on thin film lubrication approximation and demonstrated the effect of tissue elasticity and fluid yield-stress on the spreading dynamics. Our results show that both elasticity of tissue and yield-stress rheology of gel are strong determinants of the coating behavior. An optimization framework has been demonstrated which leverages the flow dynamics of yield-stress fluid during deployment to maximize retention while reaching target coating length for a given tissue elasticity.
Barker, C.E.; Bone, Y.; Lewan, M.D.
1999-01-01
Nine basalt dikes, ranging from 6 cm to 40 m thick, intruding the Upper Jurassic-Lower Cretaceous Strzelecki Group, western onshore Gippsland Basin, were used to study maximum temperatures (Tmax) reached next to dikes. Tmax was estimated from fluid inclusion and vitrinitereflectance geothermometry and compared to temperatures calculated using heat-flow models of contact metamorphism. Thermal history reconstruction suggests that at the time of dike intrusion the host rock was at a temperature of 100-135??C. Fracture-bound fluid inclusions in the host rocks next to thin dikes ( 1.5, using a normalized distance ratio used for comparing measurements between dikes regardless of their thickness. In contrast, the pattern seen next to the thin dikes is a relatively narrow zone of elevated Rv-r. Heat-flow modeling, along with whole rock elemental and isotopic data, suggests that the extended zone of elevated Rv-r is caused by a convection cell with local recharge of the hydrothermal fluids. The narrow zone of elevated Rv-r found next to thin dikes is attributed to the rise of the less dense, heated fluids at the dike contact causing a flow of cooler groundwater towards the dike and thereby limiting its heating effects. The lack of extended heating effects suggests that next to thin dikes an incipient convection system may form in which the heated fluid starts to travel upward along the dike but cooling occurs before a complete convection cell can form. Close to the dike contact at X/D 1.5. ?? 1998 Elsevier Science B.V. All rights reserved.
Rakowski, Cynthia L.; Serkowski, John A.; Richmond, Marshall C.
2010-12-01
The U.S. Army Corps of Engineers-Portland District (CENWP) has ongoing work to improve the survival of juvenile salmonids (smolt) migrating past The Dalles Dam. As part of that effort, a spillwall was constructed to improve juvenile egress through the tailrace downstream of the stilling basin. The spillwall was designed to improve smolt survival by decreasing smolt retention time in the spillway tailrace and the exposure to predators on the spillway shelf. The spillwall guides spillway flows, and hence smolt, more quickly into the thalweg. In this study, an existing computational fluid dynamics (CFD) model was modified and used to characterize tailrace hydraulics between the new spillwall and the Washington shore for six different total river flows. The effect of spillway flow distribution was simulated for three spill patterns at the lowest total river flow. The commercial CFD solver, STAR-CD version 4.1, was used to solve the unsteady Reynolds-averaged Navier-Stokes equations together with the k-epsilon turbulence model. Free surface motion was simulated using the volume-of-fluid (VOF) technique. The model results were used in two ways. First, results graphics were provided to CENWP and regional fisheries agency representatives for use and comparison to the same flow conditions at a reduced-scale physical model. The CFD results were very similar in flow pattern to that produced by the reduced-scale physical model but these graphics provided a quantitative view of velocity distribution. During the physical model work, an additional spill pattern was tested. Subsequently, that spill pattern was also simulated in the numerical model. The CFD streamlines showed that the hydraulic conditions were likely to be beneficial to fish egress at the higher total river flows (120 kcfs and greater, uniform flow distribution). At the lowest flow case, 90 kcfs, it was necessary to use a non-uniform distribution. Of the three distributions tested, splitting the flow evenly between
Patterns and flow in frictional fluid dynamics
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
Particle Deposition in a Two-Fluid Flow Environment
NASA Astrophysics Data System (ADS)
Yap, Yit Fatt; Goharzadeh, Afshin; Vargas, Francisco M.; John Chai, Chee Kiong
2014-11-01
The formation of particle deposit on surfaces occurs in many applications. For example, in the oil and gas industry, deposition of wax, hydrates and asphaltene reduces flows and clogs pipelines eventually if left untreated. Removal of the deposits is costly as it disrupts production. To further complicate the problem, the main flow carrying the depositing particles is often of a multi-phase nature. Successful mitigation effort requires good understanding and eventual prediction of the deposition process interacting within a multiphase flow environment. This work presents a model for prediction of particle deposition in a two-fluid flow environment. Modeling of the process is challenging as there are two unknown evolving interfaces, i.e. the fluid-fluid interface and the depositing front. Both interfaces are captured via the level-set method. The deposition at the depositing front is modeled as a first order reaction. The two immiscible fluids are modeled using the incompressible Navier-Stokes equations. Solution of the equations is implemented using a finite volume method. The model is then verified against known solutions. Preliminary results on deposition process in a two-fluid flow environment are presented. ADNOC R&D Oil-Sub Committee.
NASA Astrophysics Data System (ADS)
Bardsley, C.; Sewell, S.; Cumming, W. B.; Minnick, M.; Rowland, J. V.; O'Brien, J.; Price, L.
2012-12-01
Identifying permeable zones is essential for economically viable exploration and development of conventional geothermal reservoirs with naturally high permeability. Except very close to boreholes, the resolution of geological and geophysical tools is at a much larger scale than the centimetre aperture of most geothermal fluid pathways important to production. A case study from the >250°C Rotokawa Geothermal Field, currently producing 175 MWe within the Taupo Volcanic Zone in New Zealand, illustrates how a 3D visualization of a subset of available data that are conceptually relevant at the scales of interest has enhanced the understanding of fluid flow within this system. Geoscience data sets including subsurface formation geometry and permeable zones in wells; the natural state temperature pattern deduced from wells and MT resistivity; microearthquakes (MEQ) induced by injection, and surface geology have been integrated with engineering data including production pressure responses and injection rates to constrain the location and general hydraulic properties of one of the most influential faults in the field. Stratigraphic offsets of >500 m, recorded in core and cuttings from wells drilled on either side of the field, confirm the presence of this fault, initially suspected based on a surface lineation of eight young (<22 ka) hydrothermal eruption craters. The 3D visualization of the MEQ occurrence pattern in space and time helps constrain the mechanism of the MEQs themselves and, importantly, the confinement of most of the MEQs to the eastern side of the fault closest to the injection wells. Hosted within the Mesozoic meta-sedimentary basement formation, this has provided an important conceptual constraint that explains the lack of injection fluid on the western side of this fault. Further to this, if this fault is acting as a barrier at the Mesozoic meta-sedimentary level today, this could imply a switch in the behaviour of this structure as it is inferred, based
Flow over a membrane-covered, fluid-filled cavity
Mongeau, Luc; Frankel, Steven H.
2014-01-01
The flow-induced response of a membrane covering a fluid-filled cavity located in a section of a rigid-walled channel was explored using finite element analysis. The membrane was initially aligned with the channel wall and separated the channel fluid from the cavity fluid. As fluid flowed over the membrane-covered cavity, a streamwise-dependent transmural pressure gradient caused membrane deformation. This model has application to synthetic models of the vocal fold cover layer used in voice production research. In this paper, the model is introduced and responses of the channel flow, the membrane, and the cavity flow are summarized for a range of flow and membrane parameters. It is shown that for high values of cavity fluid viscosity, the intracavity pressure and the beam deflection both reached steady values. For combinations of low cavity viscosity and sufficiently large upstream pressures, large-amplitude membrane vibrations resulted. Asymmetric conditions were introduced by creating cavities on opposing sides of the channel and assigning different stiffness values to the two membranes. The asymmetry resulted in reduction in or cessation of vibration amplitude, depending on the degree of asymmetry, and in significant skewing of the downstream flow field. PMID:24723738
MEANS FOR VISUALIZING FLUID FLOW PATTERNS
Lynch, F.E.; Palmer, L.D.; Poppendick, H.F.; Winn, G.M.
1961-05-16
An apparatus is given for determining both the absolute and relative velocities of a phosphorescent fluid flowing through a transparent conduit. The apparatus includes a source for exciting a narrow trsnsverse band of the fluid to phosphorescence, detecting means such as a camera located downstream from the exciting source to record the shape of the phosphorescent band as it passes, and a timer to measure the time elapsed between operation of the exciting source and operation of the camera.
Fluid pressure and flow as a cause of bone resorption
Fahlgren, Anna
2010-01-01
Background Unstable implants in bone become surrounded by an osteolytic zone. This is seen around loose screws, for example, but may also contribute to prosthetic loosening. Previous animal studies have shown that such zones can be induced by fluctuations in fluid pressure or flow, caused by implant instability. Method To understand the roles of pressure and flow, we describe the 3-dimensional distribution of osteolytic lesions in response to fluid pressure and flow in a previously reported rat model of aseptic loosening. 50 rats had a piston inserted in the proximal tibia, designed to produce 20 local spikes in fluid pressure of a clinically relevant magnitude (700 mmHg) twice a day. The spikes lasted for about 0.3 seconds. After 2 weeks, the pressure was measured in vivo, and the osteolytic lesions induced were studied using micro-CT scans. Results Most bone resorption occurred at pre-existing cavities within the bone in the periphery around the pressurized region, and not under the piston. This region is likely to have a higher fluid flow and less pressure than the area just beneath the piston. The velocity of fluid flow was estimated to be very high (roughly 20 mm/s). Interpretation The localization of the resorptive lesions suggests that high-velocity fluid flow is important for bone resorption induced by instability. PMID:20718695
Method and Apparatus for Measuring Fluid Flow
NASA Technical Reports Server (NTRS)
Arndt, G. Dickey (Inventor); Nguyen, Than X. (Inventor); Carl, James R. (Inventor)
1995-01-01
The invention is a method and apparatus for monitoring the presence, concentration, and the movement of fluids. It is based on utilizing electromagnetic measurements of the complex permittivity of the fluids for detecting and monitoring the fluid. More particularly the apparatus uses one or more microwave probes which are placed at the locations where the measurements are to be made. A radio frequency signal is transmitted to the probe and the reflected signal is phase and amplitude detected at a rapid rate for the purpose of identifying the fluids, based on their dielectric constant at the probe. The apparatus can be used for multiple purposes including measures of flow rates, turbulence, dispersion, fluid identification, and changes in flow conditions of multiple fluids or multiple states of a single fluid in a flowline or a holding container. The apparatus includes a probe consisting of two electrical conductors separated by an insulator. A radio frequency signal is communicated to the probe and is reflected back from the portion of the probe exposed to the fluid. The radio frequency signal also provides a reference signal. An oscillator generates a second signal which combined with each of the reference signal and the reflected signal to produce signals of lower frequencies to facilitate filtering and amplifying those signals. The two signals are then mixed in a detector to produce an output signal that is representative of the phase and amplitude change caused by the reflection of the signal at the probe exposed to the fluid. The detector may be a dual phase detector that provides two such output signals that are in phase quadrature. A phase shifter may be provided for selectively changing the phase of the reference signal to improve the sensitivity of at least one of the output signals for more accurate readings and/or for calibration purposes. The two outputs that are in quadrature with respect to each other may be simultaneously monitored to account for
Ghosh, Pranay; Vahedipour, Kaveh; Lin, Min; Vogel, Jens H; Haynes, Charles; von Lieres, Eric
2013-08-30
Membrane chromatography (MC) is increasingly being used as a purification platform for large biomolecules due to higher operational flow rates. The zonal rate model (ZRM) has previously been applied to accurately characterize the hydrodynamic behavior in commercial MC capsules at different configurations and scales. Explorations of capsule size, geometry and operating conditions using the model and experiment were used to identify possible causes of inhomogeneous flow and their contributions to band broadening. In the present study, the hydrodynamics within membrane chromatography capsules are more rigorously investigated by computational fluid dynamics (CFD). The CFD models are defined according to precisely measured capsule geometries in order to avoid the estimation of geometry related model parameters. In addition to validating the assumptions and hypotheses regarding non-ideal flow mechanisms encoded in the ZRM, we show that CFD simulations can be used to mechanistically understand and predict non-binding breakthrough curves without need for estimation of any parameters. When applied to a small-scale axial flow MC capsules, CFD simulations identify non-ideal flows in the distribution (hold-up) volumes upstream and downstream of the membrane stack as the major source of band broadening. For the large-scale radial flow capsule, the CFD model quantitatively predicts breakthrough data using binding parameters independently determined using the small-scale axial flow capsule, identifying structural irregularities within the membrane pleats as an important source of band broadening. The modeling and parameter determination scheme described here therefore facilitates a holistic mechanistic-based method for model based scale-up, obviating the need of performing expensive large-scale experiments under binding conditions. As the CFD model described provides a rich mechanistic analysis of membrane chromatography systems and the ability to explore operational space, but
Program helps friction factor for non-Newtonian fluid flow
Ohen, H.A. )
1989-01-02
A Fortran program has been developed that gives more accurate predictions for shear rates, effective viscosity, Reynold's number, and hence the friction factor from which frictional pressure losses for flowing non-Newtonian fluids can be obtained. The method presented can handle flow in smooth pipes, transition, and fully rough zones of turbulence. Two mathematical models, namely the power law and the Bingham have been widely used with drilling fluids and cement slurries for relating shear stress to shear rate, the most popular being Bingham. However, most non-Newtonian fluids are not correctly represented by either of these models. In fact, experience has shown that the consistency curves of most non-Newtonian fluids fall in between those predicted by these models.
Fluid Flow in An Evaporating Droplet
NASA Technical Reports Server (NTRS)
Hu, H.; Larson, R.
1999-01-01
Droplet evaporation is a common phenomenon in everyday life. For example, when a droplet of coffee or salt solution is dropped onto a surface and the droplet dries out, a ring of coffee or salt particles is left on the surface. This phenomenon exists not only in everyday life, but also in many practical industrial processes and scientific research and could also be used to assist in DNA sequence analysis, if the flow field in the droplet produced by the evaporation could be understood and predicted in detail. In order to measure the fluid flow in a droplet, small particles can be suspended into the fluid as tracers. From the ratio of gravitational force to Brownian force a(exp 4)(delta rho)(g)/k(sub B)T, we find that particle's tendency to settle is proportional to a(exp 4) (a is particle radius). So, to keep the particles from settling, the droplet size should be chosen to be in a range 0.1 -1.0 microns in experiments. For such small particles, the Brownian force will affect the motion of the particle preventing accurate measurement of the flow field. This problem could be overcome by using larger particles as tracers to measure fluid flow under microgravity since the gravitational acceleration g is then very small. For larger particles, Brownian force would hardly affect the motion of the particles. Therefore, accurate flow field could be determined from experiments in microgravity. In this paper, we will investigate the fluid flow in an evaporating droplet under normal gravity, and compare experiments to theories. Then, we will present our ideas about the experimental measurement of fluid flow in an evaporating droplet under microgravity.
NASA Astrophysics Data System (ADS)
Jacobs, C. T.; Piggott, M. D.
2014-08-01
This model description paper introduces a new finite element model for the simulation of non-linear shallow water flows, called Firedrake-Fluids. Unlike traditional models that are written by hand in static, low-level programming languages such as Fortran or C, Firedrake-Fluids uses the Firedrake framework to automatically generate the model's code from a high-level abstract language called UFL. By coupling to the PyOP2 parallel unstructured mesh framework, Firedrake can then target the code in a performance-portable manner towards a desired hardware architecture to enable the efficient parallel execution of the model over an arbitrary computational mesh. The description of the model includes the governing equations, the methods employed to discretise and solve the governing equations, and an outline of the automated solution process. The verification and validation of the model, performed using a set of well-defined test cases, is also presented along with a roadmap for future developments and the solution of more complex fluid dynamical systems.
Fluid flow meter for measuring the rate of fluid flow in a conduit
NASA Technical Reports Server (NTRS)
White, P. R. (Inventor)
1986-01-01
A tube fluid flow rate meter consists of a reservoir divided by flexible diaphragm into two separate isolated compartments. The incoming and outgoing tubes open into the compartments. The orifice is sized to allow maximum tube fluid flow. Opposing compression springs are secured within the two compartments on opposite sides of the orifice to maintain orifice position when the tube fluid pressure is zero. A tapered element is centered in, and extends through the orifice into the compartment, leaving an annular opening between the element and the perimeter of the oriface. The size varies as the diaphragm flexes with changes in the tube fluid pressure to change the fluid flow through the opening. The light source directs light upon the element which in turn scatters the light through the opening into the compartment. The light detector in the compartment senses the scattered light to generate a signal indicating the amount of fluid.
NASA Astrophysics Data System (ADS)
Garven, G.; Dumoulin, J. A.; Bradley, D. A.; Young, L. E.; Kelley, K. D.; Leach, D. L.
2002-12-01
Crustal heat flow can provide a strong mechanism for driving groundwater flow, particularly in submarine basins where other mechanisms for driving pore fluid flow such as topography, compaction and crustal deformation are too weak or too slow to have a significant effect on disturbing conductive heat flow. Fault zones appear to play a crucial role in focusing fluid migration in basins, as inferred in ancient rocks by many examples of hydrothermal deposits of sediment-hosted ores worldwide. Many rift-hosted deposits of lead, zinc, and barite ore appear to have formed at or near the seafloor by focused venting of hot basinal fluids and modified seawater, although the geophysical nature of these systems is not so well known. For example, the upper Kuna Formation, a finely laminated, black, organic-rich siliceous mudstone and shale in the Western Brooks Range of northwest Alaska, is host to the largest resources of zinc yet discovered in the Earth's crust, containing ore reserves in excess of 175 Mt averaging about 16% Zn and 5% Pb. Although situated today in a highly-deformed series of structural allocthonous plates thrusted during the Jurassic to Cretaceous Brookian Orogeny, the stratiform ores are thought to have formed much earlier in the anoxic, mud-rich Carboniferous-age Kuna Basin when adjacent carbonate platforms were drowned by rifting and tectonic subsidence. Fluid inclusion studies of ore-stage sphalerite and gangue minerals indicate sub-seafloor mineralization temperatures less than 200oC and most likely between 120 to 150 oC, during a period of sediment diagenesis and extensional faulting. We have constructed fully-coupled numerical models of heat and fluid flow to test hydrologic theories for free convection, submarine venting and subsequent ore formation, as constrained by paleoheat flow and petrologic observations. A finite element grid was designed and adapted for a cross section of the Kuna Basin, geologically restored to latest Mississippian time
Pedersen, Jenny M.; Shim, Yoo-Sik; Hans, Vaibhav; Phillips, Martin B.; Macdonald, Jeffrey M.; Walker, Glenn; Andersen, Melvin E.; Clewell, Harvey J.; Yoon, Miyoung
2016-01-01
Accurate prediction of metabolism is a significant outstanding challenge in toxicology. The best predictions are based on experimental data from in vitro systems using primary hepatocytes. The predictivity of the primary hepatocyte-based culture systems, however, is still limited due to well-known phenotypic instability and rapid decline of metabolic competence within a few hours. Dynamic flow bioreactors for three-dimensional cell cultures are thought to be better at recapitulating tissue microenvironments and show potential to improve in vivo extrapolations of chemical or drug toxicity based on in vitro test results. These more physiologically relevant culture systems hold potential for extending metabolic competence of primary hepatocyte cultures as well. In this investigation, we used computational fluid dynamics to determine the optimal design of a flow-based hepatocyte culture system for evaluating chemical metabolism in vitro. The main design goals were (1) minimization of shear stress experienced by the cells to maximize viability, (2) rapid establishment of a uniform distribution of test compound in the chamber, and (3) delivery of sufficient oxygen to cells to support aerobic respiration. Two commercially available flow devices – RealBio® and QuasiVivo® (QV) – and a custom developed fluidized bed bioreactor were simulated, and turbulence, flow characteristics, test compound distribution, oxygen distribution, and cellular oxygen consumption were analyzed. Experimental results from the bioreactors were used to validate the simulation results. Our results indicate that maintaining adequate oxygen supply is the most important factor to the long-term viability of liver bioreactor cultures. Cell density and system flow patterns were the major determinants of local oxygen concentrations. The experimental results closely corresponded to the in silico predictions. Of the three bioreactors examined in this study, we were able to optimize the experimental
Advanced designs for fluid flow visualization
NASA Technical Reports Server (NTRS)
1978-01-01
Research was carried out on existing and new designs for minimally intrusive measurement of flow fields in the Geophysical Fluid Flow Cell and the proposed Atmospheric General Circulation Experiment. The following topics are discussed: (1) identification and removal of foreign particles, (2) search for higher dielectric photochromic solutions, (3) selection of uv light source, (4) analysis of refractive techniques and (5) examination of fresnel lens applicability.
Fluid migration in the subduction zone: a coupled fluid flow approach
NASA Astrophysics Data System (ADS)
Wang, Hongliang; Huismans, Ritske; Rondenay, Stéphane
2016-04-01
Subduction zone are the main entry point of water into earth's mantle and play an important role in the global water cycle. The progressive release of water by metamorphic dehydration induce important physical-chemical process in the subduction zone, such as hydrous melting, hydration and weakening of the mantle wedge, creation of pore fluid pressures that may weaken the subduction interface and induce earthquakes. Most previous studies on the role of fluids in subduction zones assume vertical migration or migration according to the dynamic pressure in the solid matrix without considering the pore fluid pressure effect on the deformation of the solid matrix. Here we investigate this interaction by explicitly modeling two-phase coupled poro-plastic flow during subduction. In this approach, the fluid migrates by compaction and decompaction of the solid matrix and affects the subduction dynamics through pore fluid pressure dependent frictional-plastic yield. Our preliminary results indicate that: 1) the rate of fluid migration depends strongly on the permeability and the bulk viscosity of the solid matrix, 2) fluid transfer occurs preferentially along the slab and then propagates into the mantle wedge by viscous compaction driven fluid flow, 3) fluid transport from the surface to depth is a prerequisite for producing high fluid pore pressures and associated hydration induced weakening of the subduction zone interface.
Granular Materials Flows with Interstitial Fluid Effects
NASA Astrophysics Data System (ADS)
Hunt, M. L.; Brennen, C. E.; Campbell, C. S.
2002-11-01
In 1954, R.A. Bagnold published his seminal findings on the rheological properties of liquid-solid flows. We recently completed an extensive reevaluation of Bagnold's work, and our analysis and simulations indicate that the rheological measurements of Bagnold were affected significantly by secondary flows within the experimental apparatus. The concentric cylinder rheometer was designed by Bagnold to measure simultaneously the shear and normal forces for a wide range for solid concentrations, fluid viscosities and shear rates. As presented by Bagnold, the shear and normal forces depended linearly on the shear rate in the 'macroviscous' regime. As the grain-to-grain interactions increased in the 'grain inertia' regime, the stresses depended on the square of the shear rate and were independent of the fluid viscosity. These results, however, appear to be dictated by the design of the experimental facility. In Bagnold's experiments, the height (h) of the rheometer was relatively short compared to the spacing (t) between the rotating outer and stationary inner cylinder (h/t=4.6). Since the top and bottom end plates rotated with the outer cylinder, the flow contained two axisymmetric counter-rotating cells in which flow moved outward along the end plates and inward at the midheight of the annulus. These cells contribute significantly to the measured torque, and obscured any accurate measurements of the shear or normal stresses. Before doing the reevaluation of Bagnold's work, our research objective was to examine the effects of the interstitial fluid for flows in which the densities of the two phases were different. After reevaluating Bagnold's work, we redesigned our experimental facility to minimize secondary flow effects. Like Bagnold's facility, we use a concentric cylinder rheometer with a rotating outer wall. The inner cylinder also is able to rotate slightly but will also be restrained by flexible supports; the torque is measured from the deformation of the
An Iterative CT Reconstruction Algorithm for Fast Fluid Flow Imaging.
Van Eyndhoven, Geert; Batenburg, K Joost; Kazantsev, Daniil; Van Nieuwenhove, Vincent; Lee, Peter D; Dobson, Katherine J; Sijbers, Jan
2015-11-01
The study of fluid flow through solid matter by computed tomography (CT) imaging has many applications, ranging from petroleum and aquifer engineering to biomedical, manufacturing, and environmental research. To avoid motion artifacts, current experiments are often limited to slow fluid flow dynamics. This severely limits the applicability of the technique. In this paper, a new iterative CT reconstruction algorithm for improved a temporal/spatial resolution in the imaging of fluid flow through solid matter is introduced. The proposed algorithm exploits prior knowledge in two ways. First, the time-varying object is assumed to consist of stationary (the solid matter) and dynamic regions (the fluid flow). Second, the attenuation curve of a particular voxel in the dynamic region is modeled by a piecewise constant function over time, which is in accordance with the actual advancing fluid/air boundary. Quantitative and qualitative results on different simulation experiments and a real neutron tomography data set show that, in comparison with the state-of-the-art algorithms, the proposed algorithm allows reconstruction from substantially fewer projections per rotation without image quality loss. Therefore, the temporal resolution can be substantially increased, and thus fluid flow experiments with faster dynamics can be performed.
NASA Astrophysics Data System (ADS)
Cilona, Antonino; Antonellini, Marco; Tondi, Emanuele; Agosta, Fabrizio; Johnson, Gareth; Shackleton, Ryan
2013-04-01
This contribution integrates structural analysis and numerical modelling to build up, from outcrop data, a 3D Discrete Fracture Network (DFN) model, and then to run fluid flow simulations of a porous carbonate reservoir. A semi-automated process of lineament analysis, followed by the use of power law distributions to model sub-seismic scale features, is here proposed as a workflow for reservoir-scale assessment of the control exerted by structural features on the bulk permeability in porous carbonate reservoirs. In Favignana Island (southern Italy), several quarries provide an excellent 3D view of Lower-Pleistocene grainstones crosscut by a strike-slip fault system. This fault system is made up of two main conjugate sets of strike-slip structural features such as Compactive Shear Bands (CSB), Zones of compactive shear Bands (ZB) and faults. The multi-scale properties of the aforementioned elements, distinguished for individual sets, have been previously assessed by mean of detailed scan-line and scan-area measurements. The DFN model was built using the Fracture Modelling module within the MOVE software package from Midland Valley. Analysis of an aerial photo was performed to identify the major faults. The intensity of CSBs and ZBs was computed after a preliminary outcrop analysis. We used the variation in intensity to build a DFN that reflects a pattern of deformation similar to the natural structural framework. It is well known that both CSBs and ZBs reduce permeability, whilst slip surfaces present within faults enhance fault-parallel fluid flow. The obtained DFN was used, hence, to model the effect of deformation on host rock permeability by imposing a reduced porosity of the CSBs and ZBs relative to both host rock and slip surfaces. By taking advantage of the computed distribution of both porosity and permeability within the modelled rock volume, fluid flow simulations have been carried out by solving the flow and transport equations with finite elements. In
A Causal, Covariant Theory of Dissipative Fluid Flow
NASA Astrophysics Data System (ADS)
Scofield, Dillon; Huq, Pablo
2015-04-01
The use of newtonian viscous dissipation theory in covariant fluid flow theories is known to lead to predictions that are inconsistent with the second law of thermodynamics and to predictions that are acausal. For instance, these problems effectively limit the covariant form of the Navier-Stokes theory (NST) to time-independent flow regimes. Thus the NST, the work horse of fluid dynamical theory, is limited in its ability to model time-dependent turbulent, stellar or thermonuclear flows. We show how such problems are avoided by a new geometrodynamical theory of fluids. This theory is based on a recent result of geometrodynamics showing current conservation implies gauge field creation, called the vortex field lemma and classification of flows by their Pfaff dimension. Experimental confirmation of the theory is reviewed.
The Geophysical Fluid Flow Cell Experiment
NASA Technical Reports Server (NTRS)
Hart, J. E.; Ohlsen, D.; Kittleman, S.; Borhani, N.; Leslie, F.; Miller, T.
1999-01-01
The Geophysical Fluid Flow Cell (GFFC) experiment performed visualizations of thermal convection in a rotating differentially heated spherical shell of fluid. In these experiments dielectric polarization forces are used to generate a radially directed buoyancy force. This enables the laboratory simulation of a number of geophysically and astrophysically important situations in which sphericity and rotation both impose strong constraints on global scale fluid motions. During USML-2 a large set of experiments with spherically symmetric heating were carried out. These enabled the determination of critical points for the transition to various forms of nonaxisymmetric convection and, for highly turbulent flows, the transition latitudes separating the different modes of motion. This paper presents a first analysis of these experiments as well as data on the general performance of the instrument during the USML-2 flight.
Fluid flow in free flow electrophoresis chamber in microgravity
NASA Astrophysics Data System (ADS)
Bello, Michail S.; Polezhaev, V. I.
1990-05-01
The paper is devoted to the approximate analysis and computer simulations of the viscous incompressible fluid flow in the free-flow electrophoresis chamber, parameters of which are similar to those of the Hele-Shaw cell. The buoyancy effects are assumed to be negligible and do not affect the fluid flow. Such a case corresponds to either electrophoretic separation in microgravity environment or to the electrophoresis in a rather thin chamber. The investigation is based on the Navier-Stokes equations averaged over the transverse coordinate. The streamlines of the steady flow were calculated for various values of the parameter alpha and the relative size of the inlet opening s. The parameter alpha characterizes the ratio of the fluid friction forces against chamber walls to the inertia forces. Three different regimes of the steady flow in the chamber could occur: irrotational flow and jetlike flow with and without secondary flows. The dependence of the entrance region length on the parameters alpha and s was obtained.
14 CFR 23.1095 - Carburetor deicing fluid flow rate.
Code of Federal Regulations, 2011 CFR
2011-01-01
... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Carburetor deicing fluid flow rate. 23.1095... Induction System § 23.1095 Carburetor deicing fluid flow rate. (a) If a carburetor deicing fluid system is used, it must be able to simultaneously supply each engine with a rate of fluid flow, expressed...
14 CFR 23.1095 - Carburetor deicing fluid flow rate.
Code of Federal Regulations, 2012 CFR
2012-01-01
... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Carburetor deicing fluid flow rate. 23.1095... Induction System § 23.1095 Carburetor deicing fluid flow rate. (a) If a carburetor deicing fluid system is used, it must be able to simultaneously supply each engine with a rate of fluid flow, expressed...
NASA Astrophysics Data System (ADS)
Lu, C.; Deng, S.; Podgorney, R. K.; Huang, H.
2011-12-01
Reliable reservoir performance predictions of enhanced geothermal reservoir systems require accurate and robust modeling for the coupled thermal-hydrological-mechanical processes. Conventionally, in order to reduce computational cost, these types of problems are solved using operator splitting method, usually by sequentially coupling a subsurface flow and heat transport simulator with a solid mechanics simulator via input files. However, such operator splitting approaches are applicable only to loosely coupled problems and usually converge slowly. As in most enhanced geothermal systems (EGS), fluid flow, heat transport, and rock deformation are typically strongly nonlinearly coupled, an alternative is to solve the system of nonlinear partial differential equations that govern the system simultaneously using a fully coupled solution procedure for fluid flow, heat transport, and solid mechanics. This procedure solves for all solution variables (fluid pressure, temperature and rock displacement fields) simultaneously, which leads to one large nonlinear algebraic system that needs to be solved by a strongly convergent nonlinear solver. Development over the past 10 years in the area of physics-based conditioning, strongly convergent nonlinear solvers (such as Jacobian Free Newton methods) and efficient linear solvers (such as GMRES, AMG), makes such an approach competitive. In this presentation, we will introduce a continuum-scaled parallel physics-based, fully coupled, modeling tool for predicting the dynamics of fracture initiation and propagation, fluid flow, rock deformation, and heat transport in a single integrated code named FALCON (Fracturing And Liquid-steam CONvection). FALCON is built upon a parallel computing framework developed at Idaho National Laboratory (INL) for solving coupled systems of nonlinear equations with finite element method with unstructured and adaptively refined/coarsened grids. Currently, FALCON contains poro- and thermal- elastic models
Wu, Yu-Shu; Mukhopadhyay, Sumit; Zhang, Keni; Bodvarsson, G S
2006-06-30
A multidimensional, mountain-scale, thermal-hydrologic (TH) numerical model is presented for investigating unsaturated flow behavior in response to decay heat from the proposed radioactive waste repository in the Yucca Mountain unsaturated zone (UZ), The model, consisting of both two-dimensional (2-D) and three-dimensional (3-D) representations of the UZ repository system, is based on the current repository design, drift layout, thermal loading scenario, and estimated current and future climate conditions. This mountain-scale TH model evaluates the coupled TH processes related to mountain-scale UZ flow. It also simulates the impact of radioactive waste heat release on the natural hydrogeological system, including heat-driven processes occurring near and far away from the emplacement tunnels or drifts. The model simulates predict thermally perturbed liquid saturation, gas- and liquid-phase fluxes, and water and rock temperature elevations, as well as the changes in water flux driven by evaporation/condensation processes and drainage between drifts. These simulations provide insights into mountain-scale thermally perturbed flow fields under thermal loading conditions. PMID:16624442
Wu, Yu-Shu; Mukhopadhyay, Sumit; Zhang, Keni; Bodvarsson,Gudmundur S.
2005-05-25
A multidimensional, mountain-scale, thermal-hydrologic (TH) numerical model is presented for investigating unsaturated flow behavior in response to decay heat from the radioactive waste repository in the Yucca Mountain unsaturated zone (UZ), Nevada. The model, consisting of both two-dimensional (2-D) and three-dimensional (3-D) representations of the UZ repository system, is based on the current repository design, drift layout, thermal loading scenario, and estimated current and future climate conditions. This mountain-scale TH model evaluates the coupled TH processes related to mountain-scale UZ flow. It also simulates the impact of radioactive waste heat release on the natural hydrogeological system, including heat-driven processes occurring near and far away from the emplacement tunnels or drifts. The model simulations predict thermally perturbed liquid saturation, gas- and liquid-phase fluxes, and water and rock temperature elevations, as well as the changes in water flux driven by evaporation/condensation processes and drainage between drifts. These simulations provide mountain-scale thermally perturbed flow fields for assessing the repository performance under thermal loading conditions.
Wu, Yu-Shu; Mukhopadhyay, Sumit; Zhang, Keni; Bodvarsson, G S
2006-06-30
A multidimensional, mountain-scale, thermal-hydrologic (TH) numerical model is presented for investigating unsaturated flow behavior in response to decay heat from the proposed radioactive waste repository in the Yucca Mountain unsaturated zone (UZ), The model, consisting of both two-dimensional (2-D) and three-dimensional (3-D) representations of the UZ repository system, is based on the current repository design, drift layout, thermal loading scenario, and estimated current and future climate conditions. This mountain-scale TH model evaluates the coupled TH processes related to mountain-scale UZ flow. It also simulates the impact of radioactive waste heat release on the natural hydrogeological system, including heat-driven processes occurring near and far away from the emplacement tunnels or drifts. The model simulates predict thermally perturbed liquid saturation, gas- and liquid-phase fluxes, and water and rock temperature elevations, as well as the changes in water flux driven by evaporation/condensation processes and drainage between drifts. These simulations provide insights into mountain-scale thermally perturbed flow fields under thermal loading conditions.
Fluid-solid modeling of lymphatic valves
NASA Astrophysics Data System (ADS)
Caulk, Alexander; Ballard, Matthew; Nepiyushchikh, Zhanna; Dixon, Brandon; Alexeev, Alexander
2015-11-01
The lymphatic system performs important physiological functions such as the return of interstitial fluid to the bloodstream to maintain tissue fluid balance, as well as the transport of immune cells in the body. It utilizes contractile lymphatic vessels, which contain valves that open and close to allow flow in only one direction, to directionally pump lymph against a pressure gradient. We develop a fluid-solid model of geometrically representative lymphatic valves. Our model uses a hybrid lattice-Boltzmann lattice spring method to capture fluid-solid interactions with two-way coupling between a viscous fluid and lymphatic valves in a lymphatic vessel. We use this model to investigate the opening and closing of lymphatic valves, and its effect on lymphatic pumping. This helps to broaden our understanding of the fluid dynamics of the lymphatic system.
Fluid flow in nanopores: Accurate boundary conditions for carbon nanotubes
NASA Astrophysics Data System (ADS)
Sokhan, Vladimir P.; Nicholson, David; Quirke, Nicholas
2002-11-01
Steady-state Poiseuille flow of a simple fluid in carbon nanopores under a gravitylike force is simulated using a realistic empirical many-body potential model for carbon. Building on our previous study of slit carbon nanopores we show that fluid flow in a nanotube is also characterized by a large slip length. By analyzing temporal profiles of the velocity components of particles colliding with the wall we obtain values of the Maxwell coefficient defining the fraction of molecules thermalized by the wall and, for the first time, propose slip boundary conditions for smooth continuum surfaces such that they are equivalent in adsorption, diffusion, and fluid flow properties to fully dynamic atomistic models.
Parametric Modeling for Fluid Systems
NASA Technical Reports Server (NTRS)
Pizarro, Yaritzmar Rosario; Martinez, Jonathan
2013-01-01
Fluid Systems involves different projects that require parametric modeling, which is a model that maintains consistent relationships between elements as is manipulated. One of these projects is the Neo Liquid Propellant Testbed, which is part of Rocket U. As part of Rocket U (Rocket University), engineers at NASA's Kennedy Space Center in Florida have the opportunity to develop critical flight skills as they design, build and launch high-powered rockets. To build the Neo testbed; hardware from the Space Shuttle Program was repurposed. Modeling for Neo, included: fittings, valves, frames and tubing, between others. These models help in the review process, to make sure regulations are being followed. Another fluid systems project that required modeling is Plant Habitat's TCUI test project. Plant Habitat is a plan to develop a large growth chamber to learn the effects of long-duration microgravity exposure to plants in space. Work for this project included the design and modeling of a duct vent for flow test. Parametric Modeling for these projects was done using Creo Parametric 2.0.
Dense brushes of stiff polymers or filaments in fluid flow
NASA Astrophysics Data System (ADS)
Römer, F.; Fedosov, D. A.
2015-03-01
Dense filamentous brush-like structures are present in many biological interfacial systems (e.g., glycocalyx layer in blood vessels) to control their surface properties. Such structures can regulate the softness of a surface and modify fluid flow. In this letter, we propose a theoretical model which predicts quantitatively flow-induced deformation of a dense brush of stiff polymers or filaments, whose persistence length is larger or comparable to their contour length. The model is validated by detailed mesoscopic simulations and characterizes different contributions to brush deformation including hydrodynamic friction due to flow and steric excluded-volume interactions between grafted filaments. This theoretical model can be used to describe the effect of a stiff-polymer brush on fluid flow and to aid in the quantification of experiments.
NASA Astrophysics Data System (ADS)
Kim, Ho Jun; Lee, Hae June
2016-06-01
The wide applicability of capacitively coupled plasma (CCP) deposition has increased the interest in developing comprehensive numerical models, but CCP imposes a tremendous computational cost when conducting a transient analysis in a three-dimensional (3D) model which reflects the real geometry of reactors. In particular, the detailed flow features of reactive gases induced by 3D geometric effects need to be considered for the precise calculation of radical distribution of reactive species. Thus, an alternative inclusive method for the numerical simulation of CCP deposition is proposed to simulate a two-dimensional (2D) CCP model based on the 3D gas flow results by simulating flow, temperature, and species fields in a 3D space at first without calculating the plasma chemistry. A numerical study of a cylindrical showerhead-electrode CCP reactor was conducted for particular cases of SiH4/NH3/N2/He gas mixture to deposit a hydrogenated silicon nitride (SiN x H y ) film. The proposed methodology produces numerical results for a 300 mm wafer deposition reactor which agree very well with the deposition rate profile measured experimentally along the wafer radius.
Calculate pipeline flow of compressible fluids
Cochran, T.W.
1996-02-01
When designing plants, performing safety studies, and analyzing plant problems and opportunities, estimates of the flowrate of compressible fluids in pipelines are often required. In fact, the impact of piping systems on process plant economics is so great that the initial investment in piping systems for new installations has been estimated to range from 18 to 61% of the equipment costs and from 7 to 15% of the total cost of the installed plant. Likewise, operating (energy) and maintenance costs for piping systems are significant. Considering this, practical sizing and analysis methods for pipelines are essential. In sizing pipe for incompressible fluids (that is, liquids), the Darcy or Fanning equation is typically used with the appropriate friction-factor correlation. This analysis is greatly simplified by the constant fluid density. However, with compressible fluids (gases and vapors), density, and hence velocity, may change considerably from one end of the pipe to the other. This, along with the limitations imposed by choked flow, complicates the analysis. Here the authors analyze methods for determining compressible fluid flow that are rigorous enough to handle most industrial situations, yet simple enough to be easily programmed into a personal computer. The theory and derivation of the basic equations are described very well in texts by Levenspiel and Saad.
Ultrasonic fluid flow measurement method and apparatus
Kronberg, J.W.
1993-10-12
An apparatus for measuring the flow of a fluid in a pipe using ultrasonic waves. The apparatus comprises an ultrasonic generator, a lens for focusing the sound energy produced by the generator, and means for directing the focused energy into the side of the pipe through an opening and in a direction close to parallel to the long axis of the pipe. A cone carries the sound energy to the lens from the generator. Depending on the choice of materials, there may be a quarter-wave, acoustic impedance matching section between the generator and the cone to reduce the reflections of energy at the cone boundary. The lens material has an acoustic impedance similar to that of the cone material but a different sonic velocity so that the lens can converge the sound waves in the fluid. A transition section between the lens and the fluid helps to couple the energy to the fluid and assures it is directed as close to parallel to the fluid flow direction as possible. 3 figures.
Ultrasonic fluid flow measurement method and apparatus
Kronberg, James W.
1993-01-01
An apparatus for measuring the flow of a fluid in a pipe using ultrasonic waves. The apparatus comprises an ultrasonic generator, a lens for focusing the sound energy produced by the generator, and means for directing the focused energy into the side of the pipe through an opening and in a direction close to parallel to the long axis of the pipe. A cone carries the sound energy to the lens from the generator. Depending on the choice of materials, there may be a quarter-wave, acoustic impedance matching section between the generator and the cone to reduce the reflections of energy at the cone boundary. The lens material has an acoustic impedance similar to that of the cone material but a different sonic velocity so that the lens can converge the sound waves in the fluid. A transition section between the lens and the fluid helps to couple the energy to the fluid and assures it is directed as close to parallel to the fluid flow direction as possible.
Miller, Cass T.
2009-01-01
This work is the fifth in a series of papers on the thermodynamically constrained averaging theory (TCAT) approach for modeling flow and transport phenomena in multiscale porous medium systems. The general TCAT framework and the mathematical foundation presented in previous works are used to develop models that describe species transport and single-fluid-phase flow through a porous medium system in varying physical regimes. Classical irreversible thermodynamics formulations for species in fluids, solids, and interfaces are developed. Two different approaches are presented, one that makes use of a momentum equation for each entity along with constitutive relations for species diffusion and dispersion, and a second approach that makes use of a momentum equation for each species in an entity. The alternative models are developed by relying upon different approaches to constrain an entropy inequality using mass, momentum, and energy conservation equations. The resultant constrained entropy inequality is simplified and used to guide the development of closed models. Specific instances of dilute and non-dilute systems are examined and compared to alternative formulation approaches. PMID:22563137
Fluid flow through carbon nanotubes and graphene based nanostructures
NASA Astrophysics Data System (ADS)
Tahmassebi, Amirhessam
The investigation into the behavior of the fluids in nanoscale channels, such as carbon nanotubes leads us to a new approach in the field of nanoscience. This is referred to as nano-fluidics, which can be used in nano-scale filtering and as nano-pipes for conveying fluids. The behavior of fluids in nano-fluidic devices is very different from the corresponding behavior in microscopic and macroscopic channels. In this study, we investigate the fluid flow through carbon nanotubes and graphene based nanostructures using a molecular dynamics (MD) method at a constant temperature. Three different models were created which contain single-walled carbon nanotube, graphene, and a combination of both. Liquid argon is used as fluid in the system. In the previous investigations, they were considered bombarding the atoms towards the carbon nanotubes like bullets from a gun, and due to the interactions, they lost most of their momentum. Thus, the chance for the atoms to pass through the carbon nanotube was very low. Here, we employed a new approach using a moving graphene wall to push the argon fluid towards the confinements of the systems. By performing this method, we have tried to make a continuum flow to find out how the physical quantities such as, position, velocity, pressure, and energy change when the fluid flow reaches the confinements of the systems.
Lumb, A B; Burns, A D; Figueroa Rosette, J A; Gradzik, K B; Ingham, D B; Pourkashanian, M
2015-05-01
We have used computational fluid dynamic modelling to study the effects of tracheal tube size and position on regional gas flow in the large airways. Using a three-dimensional mathematical model, we simulated flow with and without a tracheal tube, replicating both physiological and artificial breathing. Ventilation through a tracheal tube increased proportional flow to the left lung from 39.5% with no tube to 43.1-47.2%, depending on tube position. Ventilation mode and tube distance from the carina had no effect on flow. Lateral displacement and deflection of the tube increased ventilation to the ipsilateral lung; for example, when deflected 10° to the left of centre, flow to the left lung increased from 43.8 to 53.7%. Because of the small diameter of a tracheal tube relative to the trachea, gas exits a tube at high velocity such that regional ventilation may be affected by changes in the position and angle of the tube. PMID:25581493
Map of fluid flow in fractal porous medium into fractal continuum flow.
Balankin, Alexander S; Elizarraraz, Benjamin Espinoza
2012-05-01
This paper is devoted to fractal continuum hydrodynamics and its application to model fluid flows in fractally permeable reservoirs. Hydrodynamics of fractal continuum flow is developed on the basis of a self-consistent model of fractal continuum employing vector local fractional differential operators allied with the Hausdorff derivative. The generalized forms of Green-Gauss and Kelvin-Stokes theorems for fractional calculus are proved. The Hausdorff material derivative is defined and the form of Reynolds transport theorem for fractal continuum flow is obtained. The fundamental conservation laws for a fractal continuum flow are established. The Stokes law and the analog of Darcy's law for fractal continuum flow are suggested. The pressure-transient equation accounting the fractal metric of fractal continuum flow is derived. The generalization of the pressure-transient equation accounting the fractal topology of fractal continuum flow is proposed. The mapping of fluid flow in a fractally permeable medium into a fractal continuum flow is discussed. It is stated that the spectral dimension of the fractal continuum flow d(s) is equal to its mass fractal dimension D, even when the spectral dimension of the fractally porous or fissured medium is less than D. A comparison of the fractal continuum flow approach with other models of fluid flow in fractally permeable media and the experimental field data for reservoir tests are provided.
A full 3D model of fluid flow and heat transfer in an E.B. heated liquid metal bath
NASA Astrophysics Data System (ADS)
Matveichev, A.; Jardy, A.; Bellot, J. P.
2016-07-01
In order to study the dissolution of exogeneous inclusions in the liquid metal during processing of titanium alloys, a series of dipping experiments has been performed in an Electron Beam Melting laboratory furnace. Precise determination of the dissolution kinetics requires knowing and mastering the exact thermohydrodynamic behavior of the melt pool, which implies full 3D modeling of the process. To achieve this goal, one needs to describe momentum and heat transfer, phase change, as well as the development of flow turbulence in the liquid. EB power input, thermal radiation, heat loss through the cooling circuit, surface tension effects (i.e. Marangoni-induced flow) must also be addressed in the model. Therefore a new solver dealing with all these phenomena was implemented within OpenFOAM platform. Numerical results were compared with experimental data from actual Ti melting, showing a pretty good agreement. In the second stage, the immersion of a refractory sample rod in the liquid pool was simulated. Results of the simulations showed that the introduction of the sample slightly disturbs the flow field inside the bath. The amount of such disturbance depends on the exact location of the dipping.
Fluid flow sensing with ionic polymer-metal composites
NASA Astrophysics Data System (ADS)
Stalbaum, Tyler; Trabia, Sarah; Shen, Qi; Kim, Kwang J.
2016-04-01
Ionic polymer-metal composite (IPMC) actuators and sensors have been developed and modeled over the last two decades for use as soft-robotic deformable actuators and sensors. IPMC devices have been suggested for application as underwater actuators, energy harvesting devices, and medical devices such as in guided catheter insertion. Another interesting application of IPMCs in flow sensing is presented in this study. IPMC interaction with fluid flow is of interest to investigate the use of IPMC actuators as flow control devices and IPMC sensors as flow sensing devices. An organized array of IPMCs acting as interchanging sensors and actuators could potentially be designed for both flow measurement and control, providing an unparalleled tool in maritime operations. The underlying physics for this system include the IPMC ion transport and charge fundamental framework along with fluid dynamics to describe the flow around IPMCs. An experimental setup for an individual rectangular IPMC sensor with an externally controlled fluid flow has been developed to investigate this phenomenon and provide further insight into the design and application of this type of device. The results from this portion of the study include recommendations for IPMC device designs in flow control.
Boles, James R.; Garven, Grant
2015-08-04
Our studies have had an important impact on societal issues. Experimental and field observations show that CO_{2} degassing, such as might occur from stored CO_{2} reservoir gas, can result in significant stable isotopic disequilibrium. In the offshore South Ellwood field of the Santa Barbara channel, we show how oil production has reduced natural seep rates in the area, thereby reducing greenhouse gases. Permeability is calculated to be ~20-30 millidarcys for km-scale fault-focused fluid flow, using changes in natural gas seepage rates from well production, and poroelastic changes in formation pore-water pressure. In the Los Angeles (LA) basin, our characterization of formation water chemistry, including stable isotopic studies, allows the distinction between deep and shallow formations waters. Our multiphase computational-based modeling of petroleum migration demonstrates the important role of major faults on geological-scale fluid migration in the LA basin, and show how petroleum was dammed up against the Newport-Inglewood fault zone in a “geologically fast” interval of time (less than 0.5 million years). Furthermore, these fluid studies also will allow evaluation of potential cross-formational mixing of formation fluids. Lastly, our new study of helium isotopes in the LA basin shows a significant leakage of mantle helium along the Newport Inglewood fault zone (NIFZ), at flow rates up to 2 cm/yr. Crustal-scale fault permeability (~60 microdarcys) and advective versus conductive heat transport rates have been estimated using the observed helium isotopic data. The NIFZ is an important deep-seated fault that may crosscut a proposed basin decollement fault in this heavily populated area, and appears to allow seepage of helium from the mantle sources about 30 km beneath Los Angeles. The helium study has been widely cited in recent weeks by the news media, both in radio and on numerous web sites.
Garven, Grant
2015-08-11
Our studies have had an important impact on societal issues. Experimental and field observations show that CO_{2} degassing, such as might occur from stored CO_{2} reservoir gas, can result in significant stable isotopic disequilibrium. In the offshore South Ellwood field of the Santa Barbara channel, we show how oil production has reduced natural seep rates in the area, thereby reducing greenhouse gases. Permeability is calculated to be ~20-30 millidarcys for km-scale fault-focused fluid flow, using changes in natural gas seepage rates from well production, and poroelastic changes in formation pore-water pressure. In the Los Angeles (LA) basin, our characterization of formation water chemistry, including stable isotopic studies, allows the distinction between deep and shallow formations waters. Our multiphase computational-based modeling of petroleum migration demonstrates the important role of major faults on geological-scale fluid migration in the LA basin, and show how petroleum was dammed up against the Newport-Inglewood fault zone in a “geologically fast” interval of time (less than 0.5 million years). Furthermore, these fluid studies also will allow evaluation of potential cross-formational mixing of formation fluids. Lastly, our new study of helium isotopes in the LA basin shows a significant leakage of mantle helium along the Newport Inglewood fault zone (NIFZ), at flow rates up to 2 cm/yr. Crustal-scale fault permeability (~60 microdarcys) and advective versus conductive heat transport rates have been estimated using the observed helium isotopic data. The NIFZ is an important deep-seated fault that may crosscut a proposed basin decollement fault in this heavily populated area, and appears to allow seepage of helium from the mantle sources about 30 km beneath Los Angeles. The helium study has been widely cited in recent weeks by the news media, both in radio and on numerous web sites.
NASA Astrophysics Data System (ADS)
Vásquez, A.; Tolson, G.
2012-12-01
The quantification of fracture systems is important to understand the phenomenon of fluid flow in naturally fractured petroleum reservoirs. In this work, we present a case of detailed analysis of filled fracture networks (veins) covering four orders of magnitude of scale. For our analysis we selected rocks of the El Doctor platform in the state of Querétaro, Central Mexico, which is an exposed analog of naturally fractured carbonate reservoir rocks common in the near-offshore oil fields in southeast Mexico. The fractal properties of one and two dimensional natural fracture patterns mapped on limestone outcrops, are present and compared to the results obtained in other studies at different scales. The fractal dimension of different fracture properties, such as spacing, thickness, spatial distribution, density, connectivity and length are investigated and measured using different methods. The principal fractal parameters obtained in this study include the cumulative-frequency exponent of spacing and thickness, box-counting dimension, correlation dimension and Lyapunov exponent in 1D analysis; whereas the 2D analysis included the cumulative-length exponent (fragmentation dimension), box-counting dimension, mass dimension (mid and intersection points of fractures), lacunarity and connectivity. In addition, we analyzed the orientation, density and intensity of the fracture arrays. The results of the 1D analysis indicate that the fracture spacing can be characterised using the parameters mentioned before, but the best fractal parameter to characterize the distribution and array of fractures is the Lyapunov exponent, because it's value (1.06-1.42) can differentiate between different types of array. The fractal dimension obtained for cumulative-frequency of the spacing, shows a power law with a negative exponent between -1.08 and -0.70. In the case of box-counting and correlation dimensions, the values of dimension were 0.30-0.68 and 0.40-0.63 respectively. With respect
The origin of massive hydrothermal alterations: what drives fluid flow?
NASA Astrophysics Data System (ADS)
Gomez-Rivas, Enrique; Bons, Paul D.; Martín-Martín, Juan-Diego; Corbella, Mercè; Stafford, Sherry L.; Griera, Albert; Teixell, Antonio; Salas, Ramón; Travé, Anna
2014-05-01
Hydrothermal alterations form when fluids warmer than the host rocks flow through them dissolving and precipitating minerals. These fluids typically flow upwards from deeper geologic units using faults as major conduits. In some cases, hydrothermal alterations affect large (km-scale) rock volumes. One example of such process is the massive high-temperature dolostones that crop out at the Benicàssim outcrop analogue (Maestrat Basin, E Spain). In this area, seismic-scale fault-controlled stratabound dolostone bodies extend over several kilometres away from large-scale faults, replacing Lower Cretaceous limestones. The fluid responsible for such alteration is a seawater-derived brine that interacted with underlying Permian-Triassic and Paleozoic basement rocks. The estimated volume of fluid required to produce the Benicàssim dolomitization is huge, with fluid-rock ratios in the order of several tens to a few hundreds, depending on composition and reaction temperature (Gomez-Rivas et al., 2014). An open key question is what brought this warm fluid (80 - 150 ºC) upwards to a depth of less than 1 km, where the dolomitization reaction took place. The driving forces should have been able not only to provide sufficient fluid volumes at shallow depths but also to heat up the whole host rock, including the non-replaced limestones. There are two hyphoteses for driving a warm fluid upwards in the Maestrat Basin: (a) rapid release through faults of overpressured solutions in recurrent pulses and (b) thermal convection. We present a series of heat and fluid flow numerical simulations to constrain the dolomitization conditions under these two end-member cases. The results indicate that in a pulsating model the fluid must flow upwards at velocities higher than cm/s to keep their elevated temperature. Otherwise they cool down quickly, and the host rocks cannot be heated. Such velocities can be reached if the fluid flow velocity equals that of fracture propagation, as in mobile
Zhang, Yan-Hong; Ye, Shu-Jun; Wu, Ji-Chun
2014-06-01
Based on light transmission method in quantification of liquid saturation and its application in two-phase flow system, two groups of sandbox experiments were set up to study the migration of gas or Dense Non-Aqueous Phase Liquids (DNAPLs) in water saturated porous media. The migration of gas or DNAPL was monitored in the study. Two modified Light Intensity-Saturation (LIS) models for water/gas two-phase system were applied and verified by the experiment data. Moreover two new LIS models for NAPL/water system were developed and applied to simulate the DNAPL infiltration experiment data. The gas injection experiment showed that gas moved upward to the top of the sandbox in the form of 'fingering' and finally formed continuous distribution. The results of DNAPL infiltration experiment showed that TCE mainly moved downward as the result of its gravity, eventually formed irregular plume and accumulated at the bottom of the sandbox. The outcomes of two LIS models for water/gas system (WG-A and WG-B) were consistent to the measured data. The results of two LIS models for NAPL/water system (NW-A and NW-B) fit well with the observations, and Model NW-A based on assumption of individual drainage gave better results. It could be a useful reference for quantification of NAPL/water saturation in porous media system.
Squeeze flow of a Carreau fluid during sphere impact
NASA Astrophysics Data System (ADS)
Uddin, J.; Marston, J. O.; Thoroddsen, S. T.
2012-07-01
We present results from a combined numerical and experimental investigation into the squeeze flow induced when a solid sphere impacts onto a thin, ultra-viscous film of non-Newtonian fluid. We examine both the sphere motion through the liquid as well as the fluid flow field in the region directly beneath the sphere during approach to a solid plate. In the experiments we use silicone oil as the model fluid, which is well-described by the Carreau model. We use high-speed imaging and particle tracking to achieve flow visualisation within the film itself and derive the corresponding velocity fields. We show that the radial velocity either diverges as the gap between the sphere and the wall diminishes (Ztip → 0) or that it reaches a maximum value and then decays rapidly to zero as the sphere comes to rest at a non-zero distance (Ztip = Zmin) away from the wall. The horizontal shear rate is calculated and is responsible for significant viscosity reduction during the approach of the sphere. Our model of this flow, based on lubrication theory, is solved numerically and compared to experimental trials. We show that our model is able to correctly describe the physical features of the flow observed in the experiments.
Comprehensive Mathematical Model Of Real Fluids
NASA Technical Reports Server (NTRS)
Anderson, Peter G.
1996-01-01
Mathematical model of thermodynamic properties of water, steam, and liquid and gaseous hydrogen and oxygen developed for use in computational simulations of flows of mass and heat in main engine of space shuttle. Similar models developed for other fluids and applications. Based on HBMS equation of state.
Two-fluid models of turbulence
NASA Technical Reports Server (NTRS)
Spalding, D. B.
1985-01-01
The defects of turbulence models are summarized and the importance of so-called nongradient diffusion in turbulent fluxes is discussed. The mathematical theory of the flow of two interpenetrating continua is reviewed, and the mathematical formulation of the two fluid model is outlined. Results from plane wake, axisymmetric jet, and combustion studies are shown.
Physical aspects of computing the flow of a viscous fluid
NASA Technical Reports Server (NTRS)
Mehta, U. B.
1984-01-01
One of the main themes in fluid dynamics at present and in the future is going to be computational fluid dynamics with the primary focus on the determination of drag, flow separation, vortex flows, and unsteady flows. A computation of the flow of a viscous fluid requires an understanding and consideration of the physical aspects of the flow. This is done by identifying the flow regimes and the scales of fluid motion, and the sources of vorticity. Discussions of flow regimes deal with conditions of incompressibility, transitional and turbulent flows, Navier-Stokes and non-Navier-Stokes regimes, shock waves, and strain fields. Discussions of the scales of fluid motion consider transitional and turbulent flows, thin- and slender-shear layers, triple- and four-deck regions, viscous-inviscid interactions, shock waves, strain rates, and temporal scales. In addition, the significance and generation of vorticity are discussed. These physical aspects mainly guide computations of the flow of a viscous fluid.
Garven, G.; Raffensperger, J.P.; Dumoulin, J.A.; Bradley, D.A.; Young, L.E.; Kelley, K.D.; Leach, D.L.
2003-01-01
The Red Dog deposit is a giant 175 Mton (16% Zn, 5% Pb), shale-hosted Pb-Zn-Ag-Ba ore district situated in the Carboniferous Kuna Basin, Western Brooks Range, Alaska. These SEDEX-type ores are thought to have formed in calcareous turbidites and black mudstone at elevated sub-seafloor temperatures (120-150??C) within a hydrogeologic framework of submarine convection that was structurally organized by large normal faults. The theory for modeling brine migration and heat transport in the Kuna Basin is discussed with application to evaluating flow patterns and heat transport in faulted rift basins and the effects of buoyancy-driven free convection on reactive flow and ore genesis. Finite element simulations show that hydrothermal fluid was discharged into the Red Dog subbasin during a period of basin-wide crustal heat flow of 150-160 mW/m2. Basinal brines circulated to depths as great as 1-3 km along multiple normal faults flowed laterally through thick clastic aquifers acquiring metals and heat, and then rapidly ascended a single discharge fault zone at rates ??? 5 m/year to mix with seafloor sulfur and precipitate massive sulfide ores. ?? 2003 Elsevier Science B.V. All rights reserved.
NASA Astrophysics Data System (ADS)
Gray, J. D.; Owen, I.; Escudier, M. P.
2007-10-01
Dimensional analysis has been applied to an unsteady pulsatile flow of a shear-thinning power-law non-Newtonian liquid. An experiment was then designed in which both Newtonian and non-Newtonian liquids were used to model blood flow through a large-scale (38.5 mm dia.), simplified, rigid arterial junction (a distal anastomosis of a femorodistal bypass). The flow field within the junction was obtained by Particle Imaging Velocimetry and near-wall velocities were used to calculate the wall shear stresses. Dimensionless wall shear stresses were obtained at different points in the cardiac cycle for two different but dynamically similar non-Newtonian fluids; the good agreement between the measured dimensionless wall shear stresses confirm the validity of the dimensional analysis. However, blood exhibits a constant viscosity at high-shear rates and to obtain complete dynamic similarity between large-scale experiments and life-scale flows, the high-shear viscosity also needs to be included in the analysis. How this might be done is discussed in the paper.
Quantitative evaluation fo cerebrospinal fluid shunt flow
Chervu, S.; Chervu, L.R.; Vallabhajosyula, B.; Milstein, D.M.; Shapiro, K.M.; Shulman, K.; Blaufox, M.D.
1984-01-01
The authors describe a rigorous method for measuring the flow of cerebrospinal fluid (CSF) in shunt circuits implanted for the relief of obstructive hydrocephalus. Clearance of radioactivity for several calibrated flow rates was determined with a Harvard infusion pump by injecting the Rickham reservoir of a Rickham-Holter valve system with 100 ..mu..Ci of Tc-99m as pertechnetate. The elliptical and the cylindrical Holter valves used as adjunct valves with the Rickham reservoir yielded two different regression lines when the clearances were plotted against flow rats. The experimental regression lines were used to determine the in vivo flow rates from clearances calculated after injecting the Rickham reservoirs of the patients. The unique clearance characteristics of the individual shunt systems available requires that calibration curves be derived for an entire system identical to one implanted in the patient being evaluated, rather than just the injected chamber. Excellent correlation between flow rates and the clinical findings supports the reliability of this method of quantification of CSF shunt flow, and the results are fully accepted by neurosurgeons.
Curious Fluid Flows: From Complex Fluid Breakup to Helium Wetting
NASA Astrophysics Data System (ADS)
Huisman, Fawn Mitsu
This work encompasses three projects; pinch-off dynamics in non-Newtonian fluids; helium wetting on alkali metals; and the investigation of quartz tuning forks as cryogenic pressure transducers. Chapter 1 discusses the breakup of a non-Newtonian yield stress fluid bridge. We measured the minimum neck radius, hmin, as a function of time and fit it to a power law with exponent n 1. We then compare n1 to exponent n2, obtained from a rotational rheometer using a Herschel-Bulkley model. We confirm n1=n2 for the widest variety of non-Newtonian fluids to date. When these fluids are diluted with a Newtonian fluid n1 does not equal n2. No current models predict that behavior, identifying a new class of fluid breakup. Chapter 2 presents the first chemical potential-temperature phase diagram of helium on lithium, sodium and gold, using a novel pressure measurement system. The growth and superfluid transition of a helium film on these substrates is measured via an oscillator for isotherms (fixed temperature, varying amount of helium gas), and quenches (fixed amount of helium gas, varying temperature). The chemical potential-temperature plot is similar for gold, lithium and sodium despite the large difference in the substrate binding energies. No signs of a 2-D liquid-vapor transition were seen. Chapter 3 discusses the creation of a 32.768 kHz quartz tuning fork in situ pressure transducer. Tuning forks are used to measure pressure at room temperature, but no work addresses their potential as cryogenic pressure transducers. We mapped out the behavior of a tuning fork as a function of pressure at 298, 7.0, 2.5, 1.6, 1.0 and 0.7 K by measuring the quality factor. The fork is sensitive to pressures above 0.1 mTorr, limiting its use as a pressure gauge at 0.6 K and below. The experimental curves were compared to a theoretical Q(P, T) function that was refined using the 298 K data. At cryogenic temperatures the formula breaks down in the viscous region and becomes inaccurate. The
3D topographic correction of the BSR heat flow and detection of focused fluid flow
NASA Astrophysics Data System (ADS)
He, Tao; Li, Hong-Lin; Zou, Chang-Chun
2014-06-01
The bottom-simulating reflector (BSR) is a seismic indicator of the bottom of a gas hydrate stability zone. Its depth can be used to calculate the seafloor surface heat flow. The calculated BSR heat flow variations include disturbances from two important factors: (1) seafloor topography, which focuses the heat flow over regions of concave topography and defocuses it over regions of convex topography, and (2) the focused warm fluid flow within the accretionary prism coming from depths deeper than BSR. The focused fluid flow can be detected if the contribution of the topography to the BSR heat flow is removed. However, the analytical equation cannot solve the topographic effect at complex seafloor regions. We prove that 3D finite element method can model the topographic effect on the regional background heat flow with high accuracy, which can then be used to correct the topographic effect and obtain the BSR heat flow under the condition of perfectly flat topography. By comparing the corrected BSR heat flow with the regional background heat flow, focused fluid flow regions can be detected that are originally too small and cannot be detected using present-day equipment. This method was successfully applied to the midslope region of northern Cascadia subducting margin. The results suggest that the Cucumber Ridge and its neighboring area are positive heat flow anomalies, about 10%-20% higher than the background heat flow after 3D topographic correction. Moreover, the seismic imaging associated the positive heat flow anomaly areas with seabed fracture-cavity systems. This suggests flow of warm gas-carrying fluids along these high-permeability pathways, which could result in higher gas hydrate concentrations.
NASA Astrophysics Data System (ADS)
Salahuddin, T.; Malik, M. Y.; Hussain, Arif; Bilal, S.; Awais, M.
2016-03-01
The present analysis inspects the numerical investigation of MHD flow of Williamson fluid model over a sheet with variable thickness. Cattaneo-Christov heat flux model, an amended form of Fourier's law, is used to explore the heat transfer phenomena. The governing non-linear problem is presented and transformed into self-similar form by using similarity approach. The developed non-linear problem is solved numerically by using implicit finite difference scheme known as Keller box method. The effects of relevant physical parameters on velocity and temperature profiles are taken into consideration. The important finds are as follows: influence of Hartmann number M on velocity and temperature profile is opposite. Large values of wall thickness parameter α and Weissenberg number λ are suitable for reduction of velocity profile. A comparative investigation between the previously published results and the present results is found to be in good agreement.
Finite-scale equations for compressible fluid flow.
Margolin, L G
2009-07-28
Finite-scale equations (FSE) describe the evolution of finite volumes of fluid over time. We discuss the FSE for a one-dimensional compressible fluid, whose every point is governed by the Navier-Stokes equations. The FSE contain new momentum and internal energy transport terms. These are similar to terms added in numerical simulation for high-speed flows (e.g. artificial viscosity) and for turbulent flows (e.g. subgrid scale models). These similarities suggest that the FSE may provide new insight as a basis for computational fluid dynamics. Our analysis of the FS continuity equation leads to a physical interpretation of the new transport terms, and indicates the need to carefully distinguish between volume-averaged and mass-averaged velocities in numerical simulation. We make preliminary connections to the other recent work reformulating Navier-Stokes equations.
Fluid flow in solidifying monotectic alloys
NASA Technical Reports Server (NTRS)
Ecker, A.; Frazier, D. O.; Alexander, J. Iwan D.
1989-01-01
Use of a two-wavelength holographic technique results in a simultaneous determination of temperature and composition profiles during directional solidification in a system with a miscibility gap. The relationships among fluid flow, phase separation, and mass transport during the solidification of the monotectic alloy are discussed. The primary sources of fluid motion in this system are buoyancy and thermocapillary forces. These forces act together when phase separation results in the formation of droplets (this occurs at the solid-liquid interface and in the bulk melt). In the absence of phase separation, buoyancy results from density gradients related to temperature and compositional gradients in the single-phase bulk melt. The effects of buoyancy are especially evident in association with water- or ethanol-rich volumes created at the solid-liquid growth interface.
Centrifuge modelling of granular flows
NASA Astrophysics Data System (ADS)
Cabrera, Miguel Angel; Wu, Wei
2015-04-01
A common characteristic of mass flows like debris flows, rock avalanches and mudflows is that gravity is their main driving force. Gravity defines the intensity and duration of the main interactions between particles and their surrounding media (particle-particle, particle-fluid, fluid-fluid). At the same time, gravity delimits the occurrence of phase separation, inverse segregation, and mass consolidation, among other phenomena. Therefore, in the understanding of the flow physics it is important to account for the scaling of gravity in scaled models. In this research, a centrifuge model is developed to model free surface granular flows down an incline at controlled gravity conditions. Gravity is controlled by the action of an induced inertial acceleration field resulting from the rotation of the model in a geotechnical centrifuge. The characteristics of the induced inertial acceleration field during flow are discussed and validated via experimental data. Flow heights, velocity fields, basal pressure and impact forces are measured for a range of channel inclinations and gravity conditions. Preliminary results enlighten the flow characteristics at variable gravity conditions and open a discussion on the simulation of large scale processes at a laboratory scale. Further analysis on the flow physics brings valuable information for the validation of granular flows rheology.
Fluid flow in solidifying monotectic alloys
NASA Astrophysics Data System (ADS)
Ecker, A.; Frazier, D. O.; Alexander, J. Iwan D.
1989-11-01
Use of a two-wavelength holographic technique results in a simultaneous determination of temperature and composition profiles during directional solidification in a system with a miscibility gap. A shadowgraph technique is employed for flow visualization. By these methods, flow regimes are identified and related to particular melt compositions. We discuss the relationships among fluid flow, phase separation, and mass transport during the solidification of the monotectic alloy. The primary sources of fluid motion in this system are buoyancy and thermocapillary forces. These forces act together when phase separation results in the formation of droplets (this occurs at the solid-liquid interface and in the bulk melt). While buoyancy forces arise due to density differences between the droplet and the host phase, thermocapillary forces (associated with temperature gradients in the droplet surface) may predominate. In the absence of phase separation, buoyancy results from density gradients related to temperature and compositional gradients in the single-phase bulk melt. The effects of buoyancy are especially evident in association with water- or ethanol-rich volumes created at the solid-liquid growth interface.
Xu, Zhijie; Meakin, Paul
2009-06-21
Dissipative particle dynamics (DPD) is an effective mesoscopic particle model with a lower computational cost than molecular dynamics because of the soft potentials that it employs. However, the soft potential is not strong enough to prevent the DPD particles that are used to represent the fluid from penetrating solid boundaries represented by stationary DPD particles. A phase-field variable, phi(x,t), is used to indicate the phase at point x and time t, with a smooth transition from -1 (phase 1) to +1 (phase 2) across the interface. We describe an efficient implementation of no-slip boundary conditions in DPD models that combines solid-liquid particle-particle interactions with reflection at a sharp boundary located with subgrid scale accuracy using the phase field. This approach can be used for arbitrarily complex flow geometries and other similar particle models (such as smoothed particle hydrodynamics), and the validity of the model is demonstrated by DPD simulations of flow in confined systems with various geometries.
Hu, Mei-Hua; Chan, Wei-Hung; Chen, Yao-Chang; Cherng, Chen-Hwan; Lin, Chih-Kung; Tsai, Chien-Sung; Chou, Yu-Ching; Huang, Go-Shine
2016-01-01
The effects of intravenous (IV) catheter gauge and pressurization of IV fluid (IVF) bags on fluid flow rate have been studied. However, the pressure needed to achieve a flow rate equivalent to that of a 16 gauge (G) catheter through smaller G catheters and the potential for endothelial damage from the increased kinetic energy produced by higher pressurization are unclear. Constant pressure on an IVF bag was maintained by an automatic adjustable pneumatic pressure regulator of our own design. Fluids running through 16 G, 18 G, 20 G, and 22 G catheters were assessed while using IV bag pressurization to achieve the flow rate equivalent to that of a 16 G catheter. We assessed flow rates, kinetic energy, and flow injury to rabbit inferior vena cava endothelium. By applying sufficient external constant pressure to an IVF bag, all fluids could be run through smaller (G) catheters at the flow rate in a 16 G catheter. However, the kinetic energy increased significantly as the catheter G increased. Damage to the venous endothelium was negligible or minimal/patchy cell loss. We designed a new rapid infusion system, which provides a constant pressure that compresses the fluid volume until it is free from visible residual fluid. When large-bore venous access cannot be obtained, multiple smaller catheters, external pressure, or both should be considered. However, caution should be exercised when fluid pressurized to reach a flow rate equivalent to that in a 16 G catheter is run through a smaller G catheter because of the profound increase in kinetic energy that can lead to venous endothelium injury.
Hu, Mei-Hua; Chan, Wei-Hung; Chen, Yao-Chang; Cherng, Chen-Hwan; Lin, Chih-Kung; Tsai, Chien-Sung; Chou, Yu-Ching; Huang, Go-Shine
2016-01-01
The effects of intravenous (IV) catheter gauge and pressurization of IV fluid (IVF) bags on fluid flow rate have been studied. However, the pressure needed to achieve a flow rate equivalent to that of a 16 gauge (G) catheter through smaller G catheters and the potential for endothelial damage from the increased kinetic energy produced by higher pressurization are unclear. Constant pressure on an IVF bag was maintained by an automatic adjustable pneumatic pressure regulator of our own design. Fluids running through 16 G, 18 G, 20 G, and 22 G catheters were assessed while using IV bag pressurization to achieve the flow rate equivalent to that of a 16 G catheter. We assessed flow rates, kinetic energy, and flow injury to rabbit inferior vena cava endothelium. By applying sufficient external constant pressure to an IVF bag, all fluids could be run through smaller (G) catheters at the flow rate in a 16 G catheter. However, the kinetic energy increased significantly as the catheter G increased. Damage to the venous endothelium was negligible or minimal/patchy cell loss. We designed a new rapid infusion system, which provides a constant pressure that compresses the fluid volume until it is free from visible residual fluid. When large-bore venous access cannot be obtained, multiple smaller catheters, external pressure, or both should be considered. However, caution should be exercised when fluid pressurized to reach a flow rate equivalent to that in a 16 G catheter is run through a smaller G catheter because of the profound increase in kinetic energy that can lead to venous endothelium injury. PMID:26674456
Fluid Physics of Foam Evolution and Flow
NASA Technical Reports Server (NTRS)
Aref, H.; Thoroddsen, S. T.; Sullivan, J. M.
2003-01-01
The grant supported theoretical, numerical and experimental work focused on the elucidation of the fluid physics of foam structure, evolution and flow. The experimental work concentrated on these subject areas: (a) Measurements of the speed of reconnections within a foam; (b) statistics of bubble rearrangements; and (c) three-dimensional reconstruction of the foam structure. On the numerical simulation and theory side our efforts concentrated on the subjects: (a) simulation techniques for 2D and 3D foams; (b) phase transition in a compressible foam; and (c) TCP structures.
COMPARING SIMULATED AND EXPERIMENTAL HYSTERETIC TWO- PHASE TRANSIENT FLUID FLOW PHENOMENA
A hysteretic model for two-phase permeability (k)-saturation (S)-pressure (P) relations is outlined that accounts for effects of nonwetting fluid entrapment. The model can be employed in unsaturated fluid flow computer codes to predict temporal and spatial fluid distributions. Co...
Flow Diode and Method for Controlling Fluid Flow Origin of the Invention
NASA Technical Reports Server (NTRS)
Dyson, Rodger W (Inventor)
2015-01-01
A flow diode configured to permit fluid flow in a first direction while preventing fluid flow in a second direction opposite the first direction is disclosed. The flow diode prevents fluid flow without use of mechanical closures or moving parts. The flow diode utilizes a bypass flowline whereby all fluid flow in the second direction moves into the bypass flowline having a plurality of tortuous portions providing high fluidic resistance. The portions decrease in diameter such that debris in the fluid is trapped. As fluid only travels in one direction through the portions, the debris remains trapped in the portions.
Flow rate measurement in aggressive conductive fluids
NASA Astrophysics Data System (ADS)
Dubovikova, Nataliia; Kolesnikov, Yuri; Karcher, Christian
2014-03-01
Two non-contact experimental methods of flow rate measurements for aggressive conductive liquids are described. The techniques are based on electromagnetic forces and Faraday's law: Lorentz force is induced inside moving conductive liquid under influence of variable magnetic field of permanent magnets. They are mounted along a liquid metal channel or (in case of the second method) inserted into rotated metal wheels. The force acts in the opposite of fluids' velocity direction and hence it is possible to measure reaction force of it that takes place according to Newton's law on magnetic field source - permanent magnets. And by knowing the force, which linearly depends on velocity, one can calculate mean flow rate of liquid. In addition experimental "dry" calibration and its results are described for one of the measurements' techniques.
Intravenous fluid flow meter concept for zero gravity environment
NASA Technical Reports Server (NTRS)
Miller, C. G.
1972-01-01
Measuring chamber, included in infusion-set tubing, and peristaltic flow meter concept can be incorporated into flow meter that measures fluid flow rates between 100 and 600 cu cm per hour and at the same time maintains sterilization.
Geometrodynamical Fluid Theory Applied to Dynamo Flows in Planetary Interiors
NASA Astrophysics Data System (ADS)
Lewis, Kayla; Miramontes, Diego; Scofield, Dillon
2015-11-01
Due to their reliance on a Newtonian viscous stress model, the traditional Navier-Stokes equations are of parabolic type; this in turn leads to acausal behavior of solutions to these equations, e.g., a localized disturbance at any point instantaneously affects the solution arbitrarily far away. Geometrodynamical fluid theory (GFT) avoids this problem through a relativistically covariant formulation of the flow equations. Using GFT, we derive the magnetohydrodynamic equations describing the balance of energy-momentum appropriate for dynamo flows in planetary interiors. These equations include interactions between magnetic and fluid vortex fields. We derive scaling laws from these equations and compare them with scaling laws derived from the traditional approach. Finally, we discuss implications of these scalings for flows in planetary dynamos.
Modeling of curvilinear suspension flows
NASA Astrophysics Data System (ADS)
Morris, Jeffrey F.; Boulay, Fabienne
1996-11-01
The curvilinear parallel-plate and cone-and-plate rheometric flows of monodisperse noncolloidal suspensions have been modeled. Although nonuniform in shear rate, dotγ, the parallel-plate flow has been shown experimentally(A. W. Chow, S. W. Sinton, J. H. Iwayima & T. S. Stephens 1994 Phys. Fluids) 6, 2561. not to exhibit particle migration, contrary to predictions of prior suspension-flow modeling. Predictions of nonuniform particle volume fraction, φ, by the suspension-balance model(P. R. Nott & J. F. Brady 1994 J. Fluid Mech.) 275, 157. for parallel-plate and cone-and-plate flow without normal stress differences are presented. The ``nonmigration'' in parallel-plate flow may be attributed to bulk suspension normal stress differences: assuming the bulk stress has the form Σ ~ η dotγ Q(φ) with η the fluid viscosity, nonmigration is predicted for parallel-plate flow provided that Q_33 = (1/2) Q_11 at the bulk φ of interest, with 1 the flow direction and 3 the vorticity direction. Extending the model to include normal stress differences satisfying this requirement, a range of migration behavior is predicted for the cone-and-plate flow depending upon the ratio Q_11/Q_22.
Microscale imaging of cilia-driven fluid flow
Huang, Brendan K.; Choma, Michael A.
2015-01-01
Cilia-driven fluid flow is important for multiple processes in the body, including respiratory mucus clearance, gamete transport in the oviduct, right-left patterning in the embryonic node, and cerebrospinal fluid circulation. Multiple imaging techniques have been applied towards quantifying ciliary flow. Here we review common velocimetry methods of quantifying fluid flow. We then discuss four important optical modalities, including light microscopy, epifluorescence, confocal microscopy, and optical coherence tomography, that have been used to investigate cilia-driven flow. PMID:25417211
Fluid-Structure Interaction in Internal Physiological Flows
NASA Astrophysics Data System (ADS)
Heil, Matthias; Hazel, Andrew L.
2011-01-01
We provide a selective review of recent progress in the analysis of several physiological and physiologically inspired fluid-structure interaction problems, our aim being to explain the underlying physical mechanisms that cause the observed behaviors. Specifically, we discuss recent studies of self-excited oscillations in collapsible tubes, focusing primarily on studies of an idealized model system, the Starling resistor -- a device used in most laboratory experiments. We next review studies of a particular physiological, flow-induced oscillation: vocal-fold oscillations during phonation. Finally, we discuss the closure and reopening of pulmonary airways, physiological fluid-structure interaction problems that also involve the airways' liquid lining.
Fluid-dynamical model for antisurfactants
NASA Astrophysics Data System (ADS)
Conn, Justin J. A.; Duffy, Brian R.; Pritchard, David; Wilson, Stephen K.; Halling, Peter J.; Sefiane, Khellil
2016-04-01
We construct a fluid-dynamical model for the flow of a solution with a free surface at which surface tension acts. This model can describe both classical surfactants, which decrease the surface tension of the solution relative to that of the pure solvent, and antisurfactants (such as many salts when added to water, and small amounts of water when added to alcohol) which increase it. We demonstrate the utility of the model by considering the linear stability of an infinitely deep layer of initially quiescent fluid. In particular, we predict the occurrence of an instability driven by surface-tension gradients, which occurs for antisurfactant, but not for surfactant, solutions.
A Finite-Time Thermodynamics of Unsteady Fluid Flows
NASA Astrophysics Data System (ADS)
Noack, Bernd R.; Schlegel, Michael; Ahlborn, Boye; Mutschke, Gerd; Morzyński, Marek; Comte, Pierre; Tadmor, Gilead
2008-06-01
Turbulent fluid has often been conceptualized as a transient thermodynamic phase. Here, a finite-time thermodynamics (FTT) formalism is proposed to compute mean flow and fluctuation levels of unsteady incompressible flows. The proposed formalism builds upon the Galerkin model framework, which simplifies a continuum 3D fluid motion into a finite-dimensional phase-space dynamics and, subsequently, into a thermodynamics energy problem. The Galerkin model consists of a velocity field expansion in terms of flow configuration dependent modes and of a dynamical system describing the temporal evolution of the mode coefficients. Each mode is treated as one thermodynamic degree of freedom, characterized by an energy level. The dynamical system approaches local thermal equilibrium (LTE) where each mode has the same energy if it is governed only by internal (triadic) mode interactions. However, in the generic case of unsteady flows, the full system approaches only partial LTE with unequal energy levels due to strongly mode-dependent external interactions. The FTT model is first illustrated by a traveling wave governed by a 1D Burgers equation. It is then applied to two flow benchmarks: the relatively simple laminar vortex shedding, which is dominated by two eigenmodes, and the homogeneous shear turbulence, which has been modeled with 1459 modes.
Gravity-Driven Thin Film Flow of an Ellis Fluid
Kheyfets, Vitaly O.
2014-01-01
The thin film lubrication approximation has been studied extensively for moving contact lines of Newtonian fluids. However, many industrial and biological applications of the thin film equation involve shear-thinning fluids, which often also exhibit a Newtonian plateau at low shear. This study presents new numerical simulations of the three-dimensional (i.e. two-dimensional spreading), constant-volume, gravity-driven, free surface flow of an Ellis fluid. The numerical solution was validated with a new similarity solution, compared to previous experiments, and then used in a parametric study. The parametric study centered around rheological data for an example biological application of thin film flow: topical drug delivery of anti-HIV microbicide formulations, e.g. hydroxyethylcellulose (HEC) polymer solutions. The parametric study evaluated how spreading length and front velocity saturation depend on Ellis parameters. A lower concentration polymer solution with smaller zero shear viscosity (η0), τ1/2, and λ values spread further. However, when comparing any two fluids with any possible combinations of Ellis parameters, the impact of changing one parameter on spreading length depends on the direction and magnitude of changes in the other two parameters. In addition, the isolated effect of the shear-thinning parameter, λ, on the front velocity saturation depended on τ1/2. This study highlighted the relative effects of the individual Ellis parameters, and showed that the shear rates in this flow were in both the shear-thinning and plateau regions of rheological behavior, emphasizing the importance of characterizing the full range of shear-rates in rheological measurements. The validated numerical model and parametric study provides a useful tool for future steps to optimize flow of a fluid with rheological behavior well-described by the Ellis constitutive model, in a range of industrial and biological applications. PMID:25309029
Gravity-Driven Thin Film Flow of an Ellis Fluid.
Kheyfets, Vitaly O; Kieweg, Sarah L
2013-12-01
The thin film lubrication approximation has been studied extensively for moving contact lines of Newtonian fluids. However, many industrial and biological applications of the thin film equation involve shear-thinning fluids, which often also exhibit a Newtonian plateau at low shear. This study presents new numerical simulations of the three-dimensional (i.e. two-dimensional spreading), constant-volume, gravity-driven, free surface flow of an Ellis fluid. The numerical solution was validated with a new similarity solution, compared to previous experiments, and then used in a parametric study. The parametric study centered around rheological data for an example biological application of thin film flow: topical drug delivery of anti-HIV microbicide formulations, e.g. hydroxyethylcellulose (HEC) polymer solutions. The parametric study evaluated how spreading length and front velocity saturation depend on Ellis parameters. A lower concentration polymer solution with smaller zero shear viscosity (η 0), τ 1/2, and λ values spread further. However, when comparing any two fluids with any possible combinations of Ellis parameters, the impact of changing one parameter on spreading length depends on the direction and magnitude of changes in the other two parameters. In addition, the isolated effect of the shear-thinning parameter, λ, on the front velocity saturation depended on τ 1/2. This study highlighted the relative effects of the individual Ellis parameters, and showed that the shear rates in this flow were in both the shear-thinning and plateau regions of rheological behavior, emphasizing the importance of characterizing the full range of shear-rates in rheological measurements. The validated numerical model and parametric study provides a useful tool for future steps to optimize flow of a fluid with rheological behavior well-described by the Ellis constitutive model, in a range of industrial and biological applications. PMID:25309029
Partitioned fluid-solid coupling for cardiovascular blood flow: left-ventricular fluid mechanics.
Krittian, Sebastian; Janoske, Uwe; Oertel, Herbert; Böhlke, Thomas
2010-04-01
We present a 3D code-coupling approach which has been specialized towards cardiovascular blood flow. For the first time, the prescribed geometry movement of the cardiovascular flow model KaHMo (Karlsruhe Heart Model) has been replaced by a myocardial composite model. Deformation is driven by fluid forces and myocardial response, i.e., both its contractile and constitutive behavior. Whereas the arbitrary Lagrangian-Eulerian formulation (ALE) of the Navier-Stokes equations is discretized by finite volumes (FVM), the solid mechanical finite elasticity equations are discretized by a finite element (FEM) approach. Taking advantage of specialized numerical solution strategies for non-matching fluid and solid domain meshes, an iterative data-exchange guarantees the interface equilibrium of the underlying governing equations. The focus of this work is on left-ventricular fluid-structure interaction based on patient-specific magnetic resonance imaging datasets. Multi-physical phenomena are described by temporal visualization and characteristic FSI numbers. The results gained show flow patterns that are in good agreement with previous observations. A deeper understanding of cavity deformation, blood flow, and their vital interaction can help to improve surgical treatment and clinical therapy planning.
Instability of fluid flow over saturated porous medium
NASA Astrophysics Data System (ADS)
Lyubimova, Tatyana; Kolchanova, Ekaterina; Lyubimov, Dmitry
2013-04-01
We investigate the stability of a fluid flow over a saturated porous medium. The problem is of importance due to the applications to washing out of contaminants from the bottom layer of vegetation, whose properties are similar to the properties of porous medium. In the case of porous medium with the relatively high permeability and porosity the flow involves a part of the fluid saturating the porous medium, with the tangential fluid velocity drop occurring because of the resistance of the solid matrix. The drop leads to the instability analogous to Kelvin-Helmholtz one accompanied by the formation of travelling waves. In the present paper we consider a two-layer system consisting of a pure fluid layer and a porous layer saturated by the fluid located underneath. The system is bounded by a rigid surface at the bottom and a non-deformable free surface at the top. It is under the gravity and inclined at a slight angle to the horizontal axis. The boundary conditions at the interface between the fluid and porous layers are the continuity of fluid velocities and the balance of normal and tangential stresses taking into account the resistance of the solid matrix with respect to the fluid flow near the interface [1-2]. The problem is solved in the framework of the Brinkman model applying the classical shooting algorithm with orthogonalization. The stability boundaries of the stationary fluid flow over the saturated porous medium with respect to the small oscillatory perturbations are obtained for the various values of the Darcy number and the ratio of the porous layer thickness to the full thickness of the system d. It was shown that at the d > 0.5 with increasing the porous layer thickness (or with decreasing of the fluid layer thickness) the stability threshold rises. This is because of the fact that the instability is primarily caused by perturbations located in the fluid layer. At the d < 0.5 the reduction of the porous layer thickness leads to the stability threshold
Space Coffee Cup: Capillary Flow Driven Fluids in Space
Interested in learning more about how fluids react in Space? In this video, Professor Mark Weislogel, and Dr. Marshall Porterfield will discuss the Space Coffee Cup and Capillary Flow Driven Fluids...
Thermal and Fluid Flow Brazing Simulations
HOSKING, FLOYD MICHAEL; GIANOULAKIS,STEVEN E.; GIVLER,RICHARD C.; SCHUNK,P. RANDALL
1999-12-15
The thermal response of fixtured parts in a batch-type brazing furnace can require numerous, time-consuming development runs before an acceptable furnace schedule or joint design is established. Powerful computational simulation tools are being developed to minimize the required number of verification experiments, improve furnace throughput, and increase product yields. Typical furnace simulations are based on thermal, fluid flow, and structural codes that incorporate the fundamental physics of the brazing process. The use of massively parallel computing to predict furnace and joint-level responses is presented. Measured and computed data are compared. Temperature values are within 1-270 of the expected peak brazing temperature for different loading conditions. Sensitivity studies reveal that the thermal response is more sensitive to the thermal boundary conditions of the heating enclosure than variability y in the materials data. Braze flow simulations predict fillet geometry and free surface joint defects. Dynamic wetting conditions, interfacial reactions, and solidification structure add a high degree of uncertainty to the flow results.
Cerebrospinal fluid flow dynamics in the central nervous system.
Sweetman, Brian; Linninger, Andreas A
2011-01-01
Cine-phase-contrast-MRI was used to measure the three-dimensional cerebrospinal fluid (CSF) flow field inside the central nervous system (CNS) of a healthy subject. Image reconstruction and grid generation tools were then used to develop a three-dimensional fluid-structure interaction model of the CSF flow inside the CNS. The CSF spaces were discretized using the finite-element method and the constitutive equations for fluid and solid motion solved in ADINA-FSI 8.6. Model predictions of CSF velocity magnitude and stroke volume were found to be in excellent agreement with the experimental data. CSF pressure gradients and amplitudes were computed in all regions of the CNS. The computed pressure gradients and amplitudes closely match values obtained clinically. The highest pressure amplitude of 77 Pa was predicted to occur in the lateral ventricles. The pressure gradient between the lateral ventricles and the lumbar region of the spinal canal did not exceed 132 Pa (~1 mmHg) at any time during the cardiac cycle. The pressure wave speed in the spinal canal was predicted and found to agree closely with values previously reported in the literature. Finally, the forward and backward motion of the CSF in the ventricles was visualized, revealing the complex mixing patterns in the CSF spaces. The mathematical model presented in this article is a prerequisite for developing a mechanistic understanding of the relationships among vasculature pulsations, CSF flow, and CSF pressure waves in the CNS.
Fluid Flow Prediction with Development System Interwell Connectivity Influence
NASA Astrophysics Data System (ADS)
Bolshakov, M.; Deeva, T.; Pustovskikh, A.
2016-03-01
In this paper interwell connectivity has been studied. First of all, literature review of existing methods was made which is divided into three groups: Statistically-Based Methods, Material (fluid) Propagation-Based Methods and Potential (pressure) Change Propagation-Based Method. The disadvantages of the first and second groups are as follows: methods do not involve fluid flow through porous media, ignore any changes of well conditions (BHP, skin factor, etc.). The last group considers changes of well conditions and fluid flow through porous media. In this work Capacitance method (CM) has been chosen for research. This method is based on material balance and uses weight coefficients lambdas to assess well influence. In the next step synthetic model was created for examining CM. This model consists of an injection well and a production well. CM gave good results, it means that flow rates which were calculated by analytical method (CM) show matching with flow rate in model. Further new synthetic model was created which includes six production and one injection wells. This model represents seven-spot pattern. To obtain lambdas weight coefficients, the delta function was entered using by minimization algorithm. Also synthetic model which has three injectors and thirteen producer wells was created. This model simulates seven-spot pattern production system. Finally Capacitance method (CM) has been adjusted on real data of oil Field Ω. In this case CM does not give enough satisfying results in terms of field data liquid rate. In conclusion, recommendations to simplify CM calculations were given. Field Ω is assumed to have one injection and one production wells. In this case, satisfying results for production rates and cumulative production were obtained.
Fluid Flow Technology that Measures Up
NASA Technical Reports Server (NTRS)
2004-01-01
From 1994 to 1996, NASA s Marshall Space Flight Center conducted a Center Director's Discretionary Fund research effort to apply artificial intelligence technologies to the health management of plant equipment and space propulsion systems. Through this effort, NASA established a business relationship with Quality Monitoring and Control (QMC), of Kingwood, Texas, to provide hardware modeling and artificial intelligence tools. Very detailed and accurate Space Shuttle Main Engine (SSME) analysis and algorithms were jointly created, which identified several missing, critical instrumentation needs for adequately evaluating the engine health status. One of the missing instruments was a liquid oxygen (LOX) flow measurement. This instrument was missing since the original SSME included a LOX turbine flow meter that failed during a ground test, resulting in considerable damage for NASA. New balanced flow meter technology addresses this need with robust, safe, and accurate flow metering hardware.
NASA Astrophysics Data System (ADS)
Henry, Pierre-Yves; Aberle, Jochen; Dijkstra, Jasper; Myrhaug, Dag
2016-04-01
Aquatic vegetation plays a vital role in ecohydrological systems regulating many physical, chemical, and biological processes across a wide range of spatial and temporal scales. As a consequence, plant-flow interactions are of particular interest to a wide range of disciplines. While early studies of the interactions between vegetation and flowing water employed simplified and non-flexible structures such as rigid cylinders, recent studies have included flexible plants to identify the main characteristics of the hydrodynamics of vegetated flows. However, the description of plant reconfiguration has often been based on a static approach, i.e. considering the plant's deformation under a static load and neglecting turbulent fluctuations. Correlations between drag fluctuations, plant movements, and upstream turbulence were recently established showing that shear layer turbulence at the surface of the different plant elements (such as blades or stems) can contribute significantly to the dynamic behaviour of the plant. However, the relations between plant movement and force fluctuations might change under varying flow velocities, and although this point is crucial for mixing processes and plant dislodgement by fatigue, these aspects of fluid-structure interactions applied to aquatic vegetation remain largely unexplored. Using an innovative combination of sensing techniques in one set of experiments, this study investigates the relations between turbulence, fluctuating fluid forces and movements of a flexible cylindrical plant surrogate. A silicone-based flexible cylinder was attached at the bottom of a 1m wide flume in fully-developed uniform flow. The lower 22 cm of the plant surrogate were made of plain flexible silicone, while the higher 13cm included a casted rigid sensor, measuring accelerations at the tip of the surrogate. Forces were sampled at high frequencies at the surrogate's base by a 6-degrees-of-freedom force/torque sensor measuring down to the gram
On stability and turbulence of fluid flows
NASA Technical Reports Server (NTRS)
Heisenberg, Werner
1951-01-01
This investigation is divided into two parts, the treatment of the stability problem of fluid flows on the one hand, and that of the turbulent motion on the other. The first part summarizes all previous investigations under a unified point of view, that is, sets up as generally as possible the conditions under which a profile possesses unstable or stable characteristics, and indicates the methods for solution of the stability equation for any arbitrary velocity profile and for calculation of the critical Reynolds number for unstable profiles. In the second part, under certain greatly idealizing assumptions, differential equations for the turbulent motions are derived and from them qualitative information about several properties of the turbulent velocity distribution is obtained.
Time-Dependent Thermally-Driven Interfacial Flows in Multilayered Fluid Structures
NASA Technical Reports Server (NTRS)
Haj-Hariri, Hossein; Borhan, A.
1996-01-01
A computational study of thermally-driven convection in multilayered fluid structures will be performed to examine the effect of interactions among deformable fluid-fluid interfaces on the structure of time-dependent flow in these systems. Multilayered fluid structures in two models configurations will be considered: the differentially heated rectangular cavity with a free surface, and the encapsulated cylindrical liquid bridge. An extension of a numerical method developed as part of our recent NASA Fluid Physics grant will be used to account for finite deformations of fluid-fluid interfaces.
Yield Hardening of Electrorheological Fluids in Channel Flow
NASA Astrophysics Data System (ADS)
Helal, Ahmed; Qian, Bian; McKinley, Gareth H.; Hosoi, A. E.
2016-06-01
Electrorheological fluids offer potential for developing rapidly actuated hydraulic devices where shear forces or pressure-driven flow are present. In this study, the Bingham yield stress of electrorheological fluids with different particle volume fractions is investigated experimentally in wall-driven and pressure-driven flow modes using measurements in a parallel-plate rheometer and a microfluidic channel, respectively. A modified Krieger-Dougherty model can be used to describe the effects of the particle volume fraction on the yield stress and is in good agreement with the viscometric data. However, significant yield hardening in pressure-driven channel flow is observed and attributed to an increase and eventual saturation of the particle volume fraction in the channel. A phenomenological physical model linking the densification and consequent microstructure to the ratio of the particle aggregation time scale compared to the convective time scale is presented and used to predict the enhancement in yield stress in channel flow, enabling us to reconcile discrepancies in the literature between wall-driven and pressure-driven flows.
Optimization of micropillar sequences for fluid flow sculpting
NASA Astrophysics Data System (ADS)
Stoecklein, Daniel; Wu, Chueh-Yu; Kim, Donghyuk; Di Carlo, Dino; Ganapathysubramanian, Baskar
2016-01-01
Inertial fluid flow deformation around pillars in a microchannel is a new method for controlling fluid flow. Sequences of pillars have been shown to produce a rich phase space with a wide variety of flow transformations. Previous work has successfully demonstrated manual design of pillar sequences to achieve desired transformations of the flow cross section, with experimental validation. However, such a method is not ideal for seeking out complex sculpted shapes as the search space quickly becomes too large for efficient manual discovery. We explore fast, automated optimization methods to solve this problem. We formulate the inertial flow physics in microchannels with different micropillar configurations as a set of state transition matrix operations. These state transition matrices are constructed from experimentally validated streamtraces for a fixed channel length per pillar. This facilitates modeling the effect of a sequence of micropillars as nested matrix-matrix products, which have very efficient numerical implementations. With this new forward model, arbitrary micropillar sequences can be rapidly simulated with various inlet configurations, allowing optimization routines quick access to a large search space. We integrate this framework with the genetic algorithm and showcase its applicability by designing micropillar sequences for various useful transformations. We computationally discover micropillar sequences for complex transformations that are substantially shorter than manually designed sequences. We also determine sequences for novel transformations that were difficult to manually design. Finally, we experimentally validate these computational designs by fabricating devices and comparing predictions with the results from confocal microscopy.
De Boever, Wesley; Bultreys, Tom; Derluyn, Hannelore; Van Hoorebeke, Luc; Cnudde, Veerle
2016-06-01
In this paper, we examine the possibility to use on-site permeability measurements for cultural heritage applications as an alternative for traditional laboratory tests such as determination of the capillary absorption coefficient. These on-site measurements, performed with a portable air permeameter, were correlated with the pore network properties of eight sandstones and one granular limestone that are discussed in this paper. The network properties of the 9 materials tested in this study were obtained from micro-computed tomography (μCT) and compared to measurements and calculations of permeability and the capillary absorption rate of the stones under investigation, in order to find the correlation between pore network characteristics and fluid management characteristics of these sandstones. Results show a good correlation between capillary absorption, permeability and network properties, opening the possibility of using on-site permeability measurements as a standard method in cultural heritage applications.
Colonization, competition, and dispersal of pathogens in fluid flow networks.
Siryaporn, Albert; Kim, Minyoung Kevin; Shen, Yi; Stone, Howard A; Gitai, Zemer
2015-05-01
The colonization of bacteria in complex fluid flow networks, such as those found in host vasculature, remains poorly understood. Recently, it was reported that many bacteria, including Bacillus subtilis [1], Escherichia coli [2], and Pseudomonas aeruginosa [3, 4], can move in the opposite direction of fluid flow. Upstream movement results from the interplay between fluid shear stress and bacterial motility structures, and such rheotactic-like behavior is predicted to occur for a wide range of conditions [1]. Given the potential ubiquity of upstream movement, its impact on population-level behaviors within hosts could be significant. Here, we find that P. aeruginosa communities use a diverse set of motility strategies, including a novel surface-motility mechanism characterized by counter-advection and transverse diffusion, to rapidly disperse throughout vasculature-like flow networks. These motility modalities give P. aeruginosa a selective growth advantage, enabling it to self-segregate from other human pathogens such as Proteus mirabilis and Staphylococcus aureus that outcompete P. aeruginosa in well-mixed non-flow environments. We develop a quantitative model of bacterial colonization in flow networks, confirm our model in vivo in plant vasculature, and validate a key prediction that colonization and dispersal can be inhibited by modifying surface chemistry. Our results show that the interaction between flow mechanics and motility structures shapes the formation of mixed-species communities and suggest a general mechanism by which bacteria could colonize hosts. Furthermore, our results suggest novel strategies for tuning the composition of multi-species bacterial communities in hosts, preventing inappropriate colonization in medical devices, and combatting bacterial infections. PMID:25843031
Numerical Simulation of non-Newtonian Fluid Flows through Fracture Network
NASA Astrophysics Data System (ADS)
Dharmawan, I. A.; Ulhag, R. Z.; Endyana, C.; Aufaristama, M.
2016-01-01
We present a numerical simulation of non-Newtonian fluid flow in a twodimensional fracture network. The fracture is having constant mean aperture and bounded with Hurst exponent surfaces. The non-Newtonian rheology behaviour of the fluid is described using the Power-Law model. The lattice Boltzmann method is employed to calculate the solutions for non-Newtonian flow in finite Reynolds number. We use a constant force to drive the fluid within the fracture, while the bounceback rules and periodic boundary conditions are applied for the fluid-solid interaction and inflow outlflow boundary conditions, respectively. The validation study of the simulation is done via parallel plate flow simulation and the results demonstrated good agreement with the analytical solution. In addition, the fluid flow properties within the fracture network follow the relationships of power law fluid while the errors are becoming larger if the fluid more shear thinning.
P. Dixon
2004-02-11
The purpose of this Model Report is to document the unsaturated zone (UZ) fluid flow and tracer transport models and submodels as well as the flow fields generated utilizing the UZ Flow and Transport Model of Yucca Mountain (UZ Model), Nevada. This work was planned in ''Technical Work Plan (TWP) for: Performance Assessment Unsaturated Zone'' (BSC 2002 [160819], Section 1.10, Work Package AUZM06). The UZ Model has revised, updated, and enhanced the previous UZ Flow Model REV 00 ICN 01 (BSC 2001 [158726]) by incorporation of the conceptual repository design with new grids, recalibration of property sets, and more comprehensive validation effort. The flow fields describe fracture-fracture, matrix-matrix, and fracture-matrix liquid flow rates and their spatial distributions as well as moisture conditions in the UZ system. These 3-D UZ flow fields are used directly by Performance Assessment (PA). The model and submodels evaluate important hydrogeologic processes in the UZ as well as geochemistry and geothermal conditions. These provide the necessary framework to test conceptual hypotheses of flow and transport at different scales and predict flow and transport behavior under a variety of climatic conditions. In addition, this Model Report supports several PA activities, including abstractions, particle-tracking transport simulations, and the UZ Radionuclide Transport Model.
Theoretical studies of non-Newtonian and Newtonian fluid flow through porous media
Wu, Yu-Shu.
1990-02-01
A comprehensive theoretical study has been carried out on the flow behavior of both single and multiple phase non-Newtonian fluids in porous media. This work is divided into three parts: development of numerical and analytical solutions; theoretical studies of transient flow of non-Newtonian fluids in porous media; and applications of well test analysis and displacement efficiency evaluation to field problems. A fully implicit, integral finite difference model has been developed for simulation of non-Newtonian and Newtonian fluid flow through porous media. Several commonly-used rheological models of power-law and Bingham plastic non-Newtonian fluids have been incorporated in the simulator. A Buckley-Leverett type analytical solution for one-dimensional, immiscible displacement involving non-Newtonian fluids in porous media has been developed. An integral method is also presented for the study of transient flow of Bingham fluids in porous media. In addition, two well test analysis methods have been developed for analyzing pressure transient tests of power-law and Bingham fluids, respectively. Applications are included to demonstrate this new technology. The physical mechanisms involved in immiscible displacement with non-Newtonian fluids in porous media have been studied using the Buckley-Leverett type analytical solution. In another study, an idealized fracture model has been used to obtain some insights into the flow of a power-law fluid in a double-porosity medium. Transient flow of a general pseudoplastic fluid has been studied numerically. 125 refs., 91 figs., 12 tabs.
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.
Flow dichroism in critical colloidal fluids
Lenstra, T. A. J.; Dhont, J. K. G.
2001-06-01
Due to long-range correlations and slow dynamics of concentration fluctuations in the vicinity of the gas-liquid critical point, shear flow is very effective in distorting the microstructure of near-critical fluids. The anisotropic nature of the shear-field renders the microstructure highly anisotropic, leading to dichroism. Experiments on the dichroic behavior can thus be used to test theoretical predictions on microstructural order under shear flow conditions. We performed both static and dynamic dichroism and turbidity measurements on a colloid-polymer mixture, existing of silica spheres (radius 51 nm) and polydimethylsiloxane polymer (molar weight 204 kg/mol). Sufficiently far away from the critical point, in the mean-field region, the experimental data are in good agreement with theory. Very close to the critical point, beyond mean field, for which no theory exists yet, an unexpected decrease of dichroism on approach of the critical point is observed. Moreover, we do not observe critical slowing down of shear-induced dichroism, right up to the critical point, in contrast to the turbidity.
Response of Osteoblasts to the Stimulus of Fluid Flow.
Huang, Ling-Wei; Ren, Li; Yang, Peng-Fei; Shang, Peng
2015-01-01
Bone is an important porous tissue that supports the body, maintains calcium and phosphate homeostasis, protects vital organs, and houses bone marrow. The interaction between hydrostatic pressure and fluid phase, solid phase, cells, and vascular in bone makes bone inevitably bear baseline levels of fluid flow. Fluid flow plays an important role in regulating the proliferation, differentiation, distribution, and apoptosis of osteoblasts in bone. The effect of fluid flow on osteoblasts is dependent on time, velocity, and type. Some response of osteoblasts to fluid flow is closely related to the soluble factors secreted by the osteoblasts themselves or other types of bone cells. When the response is disordered, related bone diseases such as osteoporosis, osteoarthritis, and abnormal osteogenesis probably happen. In this article we review the current progress in the study of the response of osteoblasts to the direct and indirect stimulus of fluid flow and their roles in osteogenesis and related bone diseases.
Fluid flow plate for decreased density of fuel cell assembly
Vitale, Nicholas G.
1999-01-01
A fluid flow plate includes first and second outward faces. Each of the outward faces has a flow channel thereon for carrying respective fluid. At least one of the fluids serves as reactant fluid for a fuel cell of a fuel cell assembly. One or more pockets are formed between the first and second outward faces for decreasing density of the fluid flow plate. A given flow channel can include one or more end sections and an intermediate section. An interposed member can be positioned between the outward faces at an interface between an intermediate section, of one of the outward faces, and an end section, of that outward face. The interposed member can serve to isolate the reactant fluid from the opposing outward face. The intermediate section(s) of flow channel(s) on an outward face are preferably formed as a folded expanse.
Fluid flow and particle transport in mechanically ventilated airways. Part I. Fluid flow structures.
Van Rhein, Timothy; Alzahrany, Mohammed; Banerjee, Arindam; Salzman, Gary
2016-07-01
A large eddy simulation-based computational study of fluid flow and particle transport in upper tracheobronchial airways is carried out to investigate the effect of ventilation parameters on pulmonary fluid flow. Respiratory waveforms commonly used by commercial mechanical ventilators are used to study the effect of ventilation parameters and ventilation circuit on pulmonary fluid dynamics. A companion paper (Alzahrany et al. in Med Biol Eng Comput, 2014) reports our findings on the effect of the ventilation parameters and circuit on particle transport and aerosolized drug delivery. The endotracheal tube (ETT) was found to be an important geometric feature and resulted in a fluid jet that caused an increase in turbulence and created a recirculation zone with high wall shear stress in the main bronchi. Stronger turbulence was found in lower airways than would be found under normal breathing conditions due to the presence of the jet caused by the ETT. The pressure-controlled sinusoidal waveform induced the lowest wall shear stress on the airways wall. PMID:26563199
Cytoskeletal Dynamics and Fluid Flow in Drosophila Oocytes
NASA Astrophysics Data System (ADS)
de Canio, Gabriele; Goldstein, Raymond; Lauga, Eric
2015-11-01
The biological world includes a broad range of phenomena in which transport in a fluid plays a central role. Among these is the fundamental issue of cell polarity arising during development, studied historically using the model organism Drosophila melanogaster. The polarity of the oocyte is known to be induced by the translocation of mRNAs by kinesin motor proteins along a dense microtubule cytoskeleton, a process which also induces cytoplasmic streaming. Recent experimental observations have revealed the remarkable fluid-structure interactions that occur as the streaming flows back-react on the microtubules. In this work we use a combination of theory and simulations to address the interplay between the fluid flow and the configuration of cytoskeletal filaments leading to the directed motion inside the oocyte. We show in particular that the mechanical coupling between the fluid motion and the orientation of the microtubules can lead to a transition to coherent motion within the oocyte, as observed. Supported by EPSRC and ERC Advanced Investigator Grant 247333.
Fluid dynamics in airway bifurcations: I. Primary flows.
Martonen, T B; Guan, X; Schreck, R M
2001-04-01
The subject of fluid dynamics within human airways is of great importance for the risk assessment of air pollutants (inhalation toxicology) and the targeted delivery of inhaled pharmacologic drugs (aerosol therapy). As cited herein, experimental investigations of flow patterns have been performed on airway models and casts by a number of investigators. We have simulated flow patterns in human lung bifurcations and compared the results with the experimental data of Schreck (1972). The theoretical analyses were performed using a third-party software package, FIDAP, on the Cray T90 supercomputer. This effort is part of a systematic investigation where the effects of inlet conditions, Reynolds numbers, and dimensions and orientations of airways were addressed. This article focuses on primary flows using convective motion and isovelocity contour formats to describe fluid dynamics; subsequent articles in this issue consider secondary currents (Part II) and localized conditions (Part III). The agreement between calculated and measured results, for laminar flows with either parabolic or blunt inlet conditions to the bifurcations, was very good. To our knowledge, this work is the first to present such detailed comparisons of theoretical and experimental flow patterns in airway bifurcations. The agreement suggests that the methodologies can be employed to study factors affecting airflow patterns and particle behavior in human lungs.
Su, Kuo-Chih; Chuang, Shu-Fen; Ng, Eddie Yin-Kwee; Chang, Chih-Han
2014-06-01
This study uses fluid-structure interaction (FSI) simulation to investigate the relationship between the dentinal fluid flow in the dental pulp of a tooth and the elastic modulus of masticated food particles and to investigate the effects of chewing rate on fluid flow in the dental pulp. Three-dimensional simulation models of a premolar tooth (enamel, dentine, pulp, periodontal ligament, cortical bone, and cancellous bone) and food particle were created. Food particles with elastic modulus of 2,000 and 10,000 MPa were used, respectively. The external displacement loading (5 μm) was gradually directed to the food particle surface for 1 and 0.1 s, respectively, to simulate the chewing of food particles. The displacement and stress on tooth structure and fluid flow in the dental pulp were selected as evaluation indices. The results show that masticating food with a high elastic modulus results in high stress and deformation in the tooth structure, causing faster dentinal fluid flow in the pulp in comparison with that obtained with soft food. In addition, fast chewing of hard food particles can induce faster fluid flow in the pulp, which may result in dental pain. FSI analysis is shown to be a useful tool for investigating dental biomechanics during food mastication. FSI simulation can be used to predict intrapulpal fluid flow in dental pulp; this information may provide the clinician with important concept in dental biomechanics during food mastication.
NASA Technical Reports Server (NTRS)
Rodriguez, David L. (Inventor); Sturdza, Peter (Inventor)
2013-01-01
Fluid-flow simulation over a computer-generated aircraft surface is generated using inviscid and viscous simulations. A fluid-flow mesh of fluid cells is obtained. At least one inviscid fluid property for the fluid cells is determined using an inviscid fluid simulation that does not simulate fluid viscous effects. A set of intersecting fluid cells that intersects the aircraft surface are identified. One surface mesh polygon of the surface mesh is identified for each intersecting fluid cell. A boundary-layer prediction point for each identified surface mesh polygon is determined. At least one boundary-layer fluid property for each boundary-layer prediction point is determined using the at least one inviscid fluid property of the corresponding intersecting fluid cell and a boundary-layer simulation that simulates fluid viscous effects. At least one updated fluid property for at least one fluid cell is determined using the at least one boundary-layer fluid property and the inviscid fluid simulation.
Thermohydrodynamic Analysis of Cryogenic Liquid Turbulent Flow Fluid Film Bearings
NASA Technical Reports Server (NTRS)
SanAndres, Luis
1996-01-01
Computational programs developed for the thermal analysis of tilting and flexure-pad hybrid bearings, and the unsteady flow and transient response of a point mass rotor supported on fluid film bearings are described. The motion of a cryogenic liquid on the thin film annular region of a fluid film bearing is described by a set of mass and momentum conservation, and energy transport equations for the turbulent bulk-flow velocities and pressure, and accompanied by thermophysical state equations for evaluation of the fluid material properties. Zeroth-order equations describe the fluid flow field for a journal static equilibrium position, while first-order (linear) equations govern the fluid flow for small amplitude-journal center translational motions. Solution to the zeroth-order flow field equations provides the bearing flow rate, load capacity, drag torque and temperature rise. Solution to the first-order equations determines the rotordynamic force coefficients due to journal radial motions.
Natural convection flow of a generalized second grade fluid between two vertical walls
Massoudi, M.C.; Vaidya, Ashwin; Wulandana, Rachmadian
2008-02-01
We study the flow due to natural convection of a non-Newtonian fluid, modeled as a generalized second grade fluid, between two vertical parallel walls. The flow results from the two walls being held at different temperatures. The viscosity of the fluid is taken to be a function of temperature according to Reynolds’ exponential law. We solve for the dimensionless velocity and temperature profiles and study their dependence upon certain material parameters.
First Author = C.Z. Cheng; Jay R. Johnson
1998-07-10
A nonlinear kinetic-fluid model for high-beta plasmas with multiple ion species which can be applied to multiscale phenomena is presented. The model embeds important kinetic effects due to finite ion Larmor radius (FLR), wave-particle resonances, magnetic particle trapping, etc. in the framework of simple fluid descriptions. When further restricting to low frequency phenomena with frequencies less than the ion cyclotron frequency the kinetic-fluid model takes a simpler form in which the fluid equations of multiple ion species collapse into single-fluid density and momentum equations and a low frequency generalized Ohm's law. The kinetic effects are introduced via plasma pressure tensors for ions and electrons which are computed from particle distribution functions that are governed by the Vlasov equation or simplified plasma dynamics equations such as the gyrokinetic equation. The ion FLR effects provide a finite parallel electric field, a perpendicular velocity that modifies the ExB drift, and a gyroviscosity tensor, all of which are neglected in the usual one-fluid MHD description. Eigenmode equations are derived which include magnetosphere-ionosphere coupling effects for low frequency waves (e.g., kinetic/inertial Alfven waves and ballooning-mirror instabilities).
NASA Astrophysics Data System (ADS)
Dewever, B.; Swennen, R.; Breesch, L.
2013-04-01
The fluid flow history in the frontal part of the Sicilian fold and thrust belt (FTB) has been reconstructed using an integrated structural, petrographic, geochemical and microthermometric approach. The study focused on comparing fluid flow during progressive deformation along major thrust horizons and in pelagic sediments occurring in the associated thrust sheets (foot- and hanging wall). A fluid flow model is constructed for the frontal part of the Sicilian FTB. Syn-deformational quartz and calcite have been precipitated along décollement horizons in the Iudica-Scalpello study area. The microthermometric analysis of fluid inclusions in the quartz and calcite indicated migration of low saline high temperature aqueous fluids (- 1.5 < Tm < - 0.2 °C and 80 < Th < 200 °C) and hydrocarbons along the main thrusts. Geochemical and petrographic analysis showed the presence of high manganese (2500-25,000 ppm) and iron (300-7000 ppm) contents in certain calcite phases, suggesting that the migrating fluids originate from clay dewatering and clay-water interactions. The fluid flow history in the thrust sheets can be subdivided into two stages. Calcite of types 1 and 2 has identical light orange cathodoluminescence as the surrounding mudstone. Furthermore, its isotope signature (2 < δ13C < 3‰ and - 6 < δ18O < - 2‰) and minor element content are also in line with closed, host rock buffered fluid flow during the initial stages of the fluid flow history. Type 3 calcite is volumetrically by far the most important calcite phase. It occurs in (hydro-)fractures that are limited to the hanging wall of major thrusts and within major strike-slip faults that are interpreted as transfer faults as a result of thrust development. The presence of associated fluorite suggests more open fluid flow conditions during the final stages of the fluid flow history. Fluorite is characterized by low salinity fluid inclusions (- 2.6 < Tm < - 1.6 °C) with Th between 80 and 140 °C. Type 3
The fluid mechanics of continuous flow electrophoresis
NASA Astrophysics Data System (ADS)
Saville, D. A.
1990-11-01
The overall objective is to establish theoretically and confirm experimentally the ultimate capabilities of continuous flow electrophoresis chambers operating in an environment essentially free of particle sedimentation and buoyancy. The efforts are devoted to: (1) studying the effects of particle concentration on sample conductivity and dielectric constant. The dielectric constant and conductivity were identified as playing crucial roles in the behavior of the sample and on the resolving power and throughput of continuous flow devices; and (2) improving the extant mathematical models to predict flow fields and particle trajectories in continuous flow electrophoresis. A dielectric spectrometer was designed and built to measure the complex dielectric constant of a colloidal dispersion as a function of frequency between 500 Hz and 200 kHz. The real part of the signal can be related to the sample's conductivity and the imaginary part to its dielectric constant. Measurements of the dielectric constants of several different dispersions disclosed that the dielectric constants of dilute systems of the sort encountered in particle electrophoresis are much larger than would be expected based on the extant theory. Experiments were carried out to show that, in many cases, this behavior is due to the presence of a filamentary structure of small hairs on the particle surface. A technique for producing electrokinetically ideal synthetic latex particles by heat treating was developed. Given the ubiquitous nature of hairy surfaces with both cells and synthetic particles, it was deemed necessary to develop a theory to explain their behavior. A theory for electrophoretic mobility of hairy particles was developed. Finally, the extant computer programs for predicting the structure of electro-osmotically driven flows were extended to encompass flow channels with variable wall mobilities.
The fluid mechanics of continuous flow electrophoresis
NASA Technical Reports Server (NTRS)
Saville, D. A.
1990-01-01
The overall objective is to establish theoretically and confirm experimentally the ultimate capabilities of continuous flow electrophoresis chambers operating in an environment essentially free of particle sedimentation and buoyancy. The efforts are devoted to: (1) studying the effects of particle concentration on sample conductivity and dielectric constant. The dielectric constant and conductivity were identified as playing crucial roles in the behavior of the sample and on the resolving power and throughput of continuous flow devices; and (2) improving the extant mathematical models to predict flow fields and particle trajectories in continuous flow electrophoresis. A dielectric spectrometer was designed and built to measure the complex dielectric constant of a colloidal dispersion as a function of frequency between 500 Hz and 200 kHz. The real part of the signal can be related to the sample's conductivity and the imaginary part to its dielectric constant. Measurements of the dielectric constants of several different dispersions disclosed that the dielectric constants of dilute systems of the sort encountered in particle electrophoresis are much larger than would be expected based on the extant theory. Experiments were carried out to show that, in many cases, this behavior is due to the presence of a filamentary structure of small hairs on the particle surface. A technique for producing electrokinetically ideal synthetic latex particles by heat treating was developed. Given the ubiquitous nature of hairy surfaces with both cells and synthetic particles, it was deemed necessary to develop a theory to explain their behavior. A theory for electrophoretic mobility of hairy particles was developed. Finally, the extant computer programs for predicting the structure of electro-osmotically driven flows were extended to encompass flow channels with variable wall mobilities.
14 CFR 23.1095 - Carburetor deicing fluid flow rate.
Code of Federal Regulations, 2010 CFR
2010-01-01
... Induction System § 23.1095 Carburetor deicing fluid flow rate. (a) If a carburetor deicing fluid system is.... (b) The fluid must be introduced into the air induction system— (1) Close to, and upstream of, the carburetor; and (2) So that it is equally distributed over the entire cross section of the induction...
Homogenization of two fluid flow in porous media
Daly, K. R.; Roose, T.
2015-01-01
The macroscopic behaviour of air and water in porous media is often approximated using Richards' equation for the fluid saturation and pressure. This equation is parametrized by the hydraulic conductivity and water release curve. In this paper, we use homogenization to derive a general model for saturation and pressure in porous media based on an underlying periodic porous structure. Under an appropriate set of assumptions, i.e. constant gas pressure, this model is shown to reduce to the simpler form of Richards' equation. The starting point for this derivation is the Cahn–Hilliard phase field equation coupled with Stokes equations for fluid flow. This approach allows us, for the first time, to rigorously derive the water release curve and hydraulic conductivities through a series of cell problems. The method captures the hysteresis in the water release curve and ties the macroscopic properties of the porous media with the underlying geometrical and material properties. PMID:27547073
Some specific features of the NMR study of fluid flows
NASA Astrophysics Data System (ADS)
Davydov, V. V.
2016-07-01
Some specific features of studying fluid flows with a NMR spectrometer are considered. The consideration of these features in the NMR spectrometer design makes it possible to determine the relative concentrations of paramagnetic ions and measure the longitudinal and transverse relaxation times ( T 1 and T 2, respectively) in fluid flows with an error no larger than 0.5%. This approach allows one to completely avoid errors in determining the state of a fluid from measured relaxation constants T 1 and T 2, which is especially urgent when working with medical suspensions and biological solutions. The results of an experimental study of fluid flows are presented.
Fluid flow into vertical fractures from a point source
Clark, P.E.; Zhu, Q.
1995-03-01
Flow into a fracture from a point source recently has been the focus of attention in the petroleum industry. The suggestion has been made that, in this flow configuration, convection (gravity-driven flow) would dominate Stokes`-type settling for determining final proppant distribution. The theory is that when a dense fluid flows into a fracture filled with a less dense fluid from a point source, the density of the fluid will force it to the bottom of the fracture. This clearly happens when the two fluids have low viscosity. However, viscosity of both the fluid in the fracture and the displacing fluid and nonuniformities in the fracture influence displacement process significantly. Results presented in this study clearly show the effects of viscosity and fracture nonuniformity on the convective settling mechanism.
Comparing fluid mechanics models with experimental data.
Spedding, G R
2003-01-01
The art of modelling the physical world lies in the appropriate simplification and abstraction of the complete problem. In fluid mechanics, the Navier-Stokes equations provide a model that is valid under most circumstances germane to animal locomotion, but the complexity of solutions provides strong incentive for the development of further, more simplified practical models. When the flow organizes itself so that all shearing motions are collected into localized patches, then various mathematical vortex models have been very successful in predicting and furthering the physical understanding of many flows, particularly in aerodynamics. Experimental models have the significant added convenience that the fluid mechanics can be generated by a real fluid, not a model, provided the appropriate dimensionless groups have similar values. Then, analogous problems can be encountered in making intelligible but independent descriptions of the experimental results. Finally, model predictions and experimental results may be compared if, and only if, numerical estimates of the likely variations in the tested quantities are provided. Examples from recent experimental measurements of wakes behind a fixed wing and behind a bird in free flight are used to illustrate these principles. PMID:14561348
Characterization of fluid flow in naturally fractured reservoirs. Final report
Evans, R.D.
1981-08-01
This report summarizes the results of a four month study of the characteristics of multiphase flow in naturally fractured porous media. An assessment and evaluation of the literature was carried out and a comprehensive list of references compiled on the subject. Mathematical models presented in the various references cited were evaluated along with the stated assumptions or those inherent in the equations. Particular attention was focused upon identifying unique approaches which would lead to the formulation of a general mathematical model of multiphase/multi-component flow in fractured porous media. A model is presented which may be used to more accurately predict the movement of multi-phase fluids through such type formations. Equations of motion are derived for a multiphase/multicomponent fluid which is flowing through a double porosity, double permeability medium consisting of isotropic primary rock matrix blocks and an anisotropic fracture matrix system. The fractures are assumed to have a general statistical distribution in space and orientation. A general distribution function, called the fracture matrix function is introduced to represent the statistical nature of the fractures.
Advanced numerics for multi-dimensional fluid flow calculations
Vanka, S.P.
1984-04-01
In recent years, there has been a growing interest in the development and use of mathematical models for the simulation of fluid flow, heat transfer and combustion processes in engineering equipment. The equations representing the multi-dimensional transport of mass, momenta and species are numerically solved by finite-difference or finite-element techniques. However despite the multiude of differencing schemes and solution algorithms, and the advancement of computing power, the calculation of multi-dimensional flows, especially three-dimensional flows, remains a mammoth task. The following discussion is concerned with the author's recent work on the construction of accurate discretization schemes for the partial derivatives, and the efficient solution of the set of nonlinear algebraic equations resulting after discretization. The present work has been jointly supported by the Ramjet Engine Division of the Wright Patterson Air Force Base, Ohio, and the NASA Lewis Research Center.
Advanced numerics for multi-dimensional fluid flow calculations
NASA Technical Reports Server (NTRS)
Vanka, S. P.
1984-01-01
In recent years, there has been a growing interest in the development and use of mathematical models for the simulation of fluid flow, heat transfer and combustion processes in engineering equipment. The equations representing the multi-dimensional transport of mass, momenta and species are numerically solved by finite-difference or finite-element techniques. However despite the multiude of differencing schemes and solution algorithms, and the advancement of computing power, the calculation of multi-dimensional flows, especially three-dimensional flows, remains a mammoth task. The following discussion is concerned with the author's recent work on the construction of accurate discretization schemes for the partial derivatives, and the efficient solution of the set of nonlinear algebraic equations resulting after discretization. The present work has been jointly supported by the Ramjet Engine Division of the Wright Patterson Air Force Base, Ohio, and the NASA Lewis Research Center.
Magnetic resonance measurement of fluid dynamics and transport in tube flow of a near-critical fluid
NASA Astrophysics Data System (ADS)
Bray, Joshua M.; Rassi, Erik M.; Seymour, Joseph D.; Codd, Sarah L.
2014-07-01
An ability to predict fluid dynamics and transport in supercritical fluids is essential for optimization of applications such as carbon sequestration, enhanced oil recovery, "green" solvents, and supercritical coolant systems. While much has been done to model supercritical velocity distributions, experimental characterization is sparse, owing in part to a high sensitivity to perturbation by measurement probes. Magnetic resonance (MR) techniques, however, detect signal noninvasively from the fluid molecules and thereby overcome this obstacle to measurement. MR velocity maps and propagators (i.e., probability density functions of displacement) were acquired of a flowing fluid in several regimes about the critical point, providing quantitative data on the transport and fluid dynamics in the system. Hexafluoroethane (C2F6) was pumped at 0.5 ml/min in a cylindrical tube through an MR system, and propagators as well as velocity maps were measured at temperatures and pressures below, near, and above the critical values. It was observed that flow of C2F6 with thermodynamic properties far above or below the critical point had the Poiseuille flow distribution of an incompressible Newtonian fluid. Flows with thermodynamic properties near the critical point exhibit complex flow distributions impacted by buoyancy and viscous forces. The approach to steady state was also observed and found to take the longest near the critical point, but once it was reached, the dynamics were stable and reproducible. These data provide insight into the interplay between the critical phase transition thermodynamics and the fluid dynamics, which control transport processes.
HYDROGEN ELECTROLYZER FLOW DISTRIBUTOR MODEL
Shadday, M
2006-09-28
The hybrid sulfur process (HyS) hydrogen electrolyzer consists of a proton exchange membrane (PEM) sandwiched between two porous graphite layers. An aqueous solution of sulfuric acid with dissolved SO{sub 2} gas flows parallel to the PEM through the porous graphite layer on the anode side of the electrolyzer. A flow distributor, consisting of a number of parallel channels acting as headers, promotes uniform flow of the anolyte fluid through the porous graphite layer. A numerical model of the hydraulic behavior of the flow distributor is herein described. This model was developed to be a tool to aid the design of flow distributors. The primary design objective is to minimize spatial variations in the flow through the porous graphite layer. The hydraulic data from electrolyzer tests consists of overall flowrate and pressure drop. Internal pressure and flow distributions are not measured, but these details are provided by the model. The model has been benchmarked against data from tests of the current electrolyzer. The model reasonably predicts the viscosity effect of changing the fluid from water to an aqueous solution of 30 % sulfuric acid. The permeability of the graphite layer was the independent variable used to fit the model to the test data, and the required permeability for a good fit is within the range literature values for carbon paper. The model predicts that reducing the number of parallel channels by 50 % will substantially improve the uniformity of the flow in the porous graphite layer, while maintaining an acceptable pressure drop across the electrolyzer. When the size of the electrolyzer is doubled from 2.75 inches square to 5.5 inches square, the same number of channels as in the current design will be adequate, but it is advisable to increase the channel cross-sectional flow area. This is due to the increased length of the channels.
Method and apparatus for chemically altering fluids in continuous flow
Heath, W.O.; Virden, J.W. Jr.; Richardson, R.L.; Bergsman, T.M.
1993-10-19
The present invention relates to a continuous flow fluid reactor for chemically altering fluids. The reactor operates on standard frequency (50 to 60 Hz) electricity. The fluid reactor contains particles that are energized by the electricity to form a corona throughout the volume of the reactor and subsequently a non-equilibrium plasma that interacts with the fluid. Particles may form a fixed bed or a fluid bed. Electricity may be provided through electrodes or through an inductive coil. Fluids include gases containing exhaust products and organic fuels requiring oxidation. 4 figures.
Method and apparatus for chemically altering fluids in continuous flow
Heath, William O.; Virden, Jr., Judson W.; Richardson, R. L.; Bergsman, Theresa M.
1993-01-01
The present invention relates to a continuous flow fluid reactor for chemically altering fluids. The reactor operates on standard frequency (50 to 60 Hz) electricity. The fluid reactor contains particles that are energized by the electricity to form a corona throughout the volume of the reactor and subsequently a non-equilibrium plasma that interacts with the fluid. Particles may form a fixed bed or a fluid bed. Electricity may be provided through electrodes or through an inductive coil. Fluids include gases containing exhaust products and organic fuels requiring oxidation.
Human red blood cells deformed under thermal fluid flow.
Foo, Ji-Jinn; Chan, Vincent; Feng, Zhi-Qin; Liu, Kuo-Kang
2006-03-01
The flow-induced mechanical deformation of a human red blood cell (RBC) during thermal transition between room temperature and 42.0 degrees C is interrogated by laser tweezer experiments. Based on the experimental geometry of the deformed RBC, the surface stresses are determined with the aid of computational fluid dynamics simulation. It is found that the RBC is more deformable while heating through 37.0 degrees C to 42.0 degrees C, especially at a higher flow velocity due to a thermal-fluid effect. More importantly, the degree of RBC deformation is irreversible and becomes softer, and finally reaches a plateau (at a uniform flow velocity U > 60 microm s(-1)) after the heat treatment, which is similar to a strain-hardening dominated process. In addition, computational simulated stress is found to be dependent on the progression of thermotropic phase transition. Overall, the current study provides new insights into the highly coupled temperature and hydrodynamic effects on the biomechanical properties of human erythrocyte in a model hydrodynamic flow system.
Dinarvand, Saeed
2011-10-01
In this article, the problem of laminar, isothermal, incompressible and viscous flow in a rectangular domain bounded by two moving porous walls, which enable the fluid to enter or exit during successive expansions or contractions, is investigated. The governing non-linear equations and their associated boundary conditions are transformed into a highly non-linear ordinary differential equation. The series solution of the problem is obtained by utilising the homotopy perturbation method. Graphical results are presented to investigate the influence of the non-dimensional wall dilation rate and seepage Reynolds number (Re) on the velocity, normal pressure distribution and wall shear stress. Since the transport of biological fluids through contracting or expanding vessels is characterised by low seepage Res, the current study focuses on the viscous flow driven by small wall contractions and expansions of two weakly permeable walls.
Incompressible two-phase flows with an inextensible Newtonian fluid interface
NASA Astrophysics Data System (ADS)
Reuther, Sebastian; Voigt, Axel
2016-10-01
We introduce a diffuse interface approximation for an incompressible two-phase flow problem with an inextensible Newtonian fluid interface. This approach allows to model lipid membranes as viscous fluids. In the present setting the membranes are assumed to be stationary. We validate the model and the numerical approach, which is based on a stream function formulation for the surface flow problem, an operator splitting approach and a semi-implicit adaptive finite element discretization, against observed flow patterns in vesicles, which are adhered to a solid surface and are subjected to shear flow. The influence of the Gaussian curvature on the surface flow pattern is discussed.
Pore fluid pressure and shear behavior in debris flows of different compositions
NASA Astrophysics Data System (ADS)
Kaitna, Roland; Palucis, Marisa; Yohannes, Bereket; Hill, Kimberly; Dietrich, William
2016-04-01
Debris flows are mixtures of sediment and water that can have a wide range of different grain size distributions and water contents. The composition of the material is expected to have a strong effect on the development of pore fluid pressures in excess to hydrostatic, which in turn might affect the internal deformation behavior. We present a set of large scale experiments with debris flow mixtures of different compositions in a 4-m diameter rotating drum. Longitudinal profiles of basal fluid pressure and normal stress were measured and a probe to determine fluid pressure at different depths within the flow was developed and tested. Additionally we determined vertical profiles of mean particle velocities in the flow interior by measuring small variations of conductivity of the passing material and calculating the time lag between signals from two independent measurements at a small, known distance apart. Mean values of basal pore fluid pressure range from hydrostatic pressure for gravel-water flows to nearly complete liquefaction for muddy mixtures having a wide grain size distribution. The data indicate that the presence of fines dampens fluctuations of normalized fluid pressure and normal stress and concentrates shear at the base. The mobility of grain-fluid flows is strongly enhanced by a combination of fines in suspension as part of the interstitial fluid and a wide grain size distribution. Excess fluid pressure may arise from fluid displacement by converging grains at the front of the flow and the slow settling of grains through a highly viscous non-Newtonian fluid. Our findings support the need for pore pressure evolution and diffusion equations in debris flow models as they depend on particle size distributions. This study contributes to the understanding of the production of excess fluid pressure in grain fluid mixtures and may guide the development of constitutive models that describe natural events.
Computational fluid dynamic modelling of cavitation
NASA Technical Reports Server (NTRS)
Deshpande, Manish; Feng, Jinzhang; Merkle, Charles L.
1993-01-01
Models in sheet cavitation in cryogenic fluids are developed for use in Euler and Navier-Stokes codes. The models are based upon earlier potential-flow models but enable the cavity inception point, length, and shape to be determined as part of the computation. In the present paper, numerical solutions are compared with experimental measurements for both pressure distribution and cavity length. Comparisons between models are also presented. The CFD model provides a relatively simple modification to an existing code to enable cavitation performance predictions to be included. The analysis also has the added ability of incorporating thermodynamic effects of cryogenic fluids into the analysis. Extensions of the current two-dimensional steady state analysis to three-dimensions and/or time-dependent flows are, in principle, straightforward although geometrical issues become more complicated. Linearized models, however offer promise of providing effective cavitation modeling in three-dimensions. This analysis presents good potential for improved understanding of many phenomena associated with cavity flows.
Friction-Induced Fluid Heating in Nanoscale Helium Flows
Li Zhigang
2010-05-21
We investigate the mechanism of friction-induced fluid heating in nanoconfinements. Molecular dynamics simulations are used to study the temperature variations of liquid helium in nanoscale Poiseuille flows. It is found that the fluid heating is dominated by different sources of friction as the external driving force is changed. For small external force, the fluid heating is mainly caused by the internal viscous friction in the fluid. When the external force is large and causes fluid slip at the surfaces of channel walls, the friction at the fluid-solid interface dominates over the internal friction in the fluid and is the major contribution to fluid heating. An asymmetric temperature gradient in the fluid is developed in the case of nonidentical walls and the general temperature gradient may change sign as the dominant heating factor changes from internal to interfacial friction with increasing external force.
Numerical modeling of fluid migration in subduction zones
NASA Astrophysics Data System (ADS)
Walter, M. J.; Quinteros, J.; Sobolev, S. V.
2015-12-01
It is well known that fluids play a crucial role in subduction evolution. For example, mechanical weakening along tectonic interfaces, due to high fluid pressure, may enable oceanic subduction. Hence, the fluid content seems to be a critical parameter for subduction initiation. Studies have also shown a correlation between the location of slab dehydration and intermediate seismic activity. Furthermore, expelled fluids from the subduction slab affect the melting temperature, consequently, contributing to partial melting in the wedge above the down-going plate and extensive volcanism. In summary, fluids have a great impact on tectonic processes and therefore should be incorporated into geodynamic numerical models. Here we use existing approaches to couple and solve fluid flow equations in the SLIM-3D thermo-mechanical code. SLIM-3D is a three-dimensional thermo-mechanical code capable of simulating lithospheric deformation with elasto-visco-plastic rheology. It has been successfully applied to model geodynamic processes at different tectonic settings, including subduction zones. However, although SLIM-3D already includes many features, fluid migration has not been incorporated into the model yet. To this end, we coupled solid and fluid flow assuming that fluids flow through a porous and deformable solid. Thereby, we introduce a two-phase flow into the model, in which the Stokes flow is coupled with the Darcy law for fluid flow. Ultimately, the evolution of porosity is governed by a compaction pressure and the advection of the porous solid. We show the details of our implementation of the fluid flow into the existing thermo-mechanical finite element code and present first results of benchmarks and experiments. We are especially interested in the coupling of subduction processes and the evolution of the magmatic arc. Thereby, we focus on the key factors controlling magma emplacement and its influence on subduction processes.
Thermodynamics and flow-frames for dissipative relativistic fluids
Ván, P.; Biró, T. S.
2014-01-14
A general thermodynamic treatment of dissipative relativistic fluids is introduced, where the temperature four vector is not parallel to the velocity field of the fluid. Generic stability and kinetic equilibrium points out a particular thermodynamics, where the temperature vector is parallel to the enthalpy flow vector and the choice of the flow fixes the constitutive functions for viscous stress and heat. The linear stability of the homogeneous equilibrium is proved in a mixed particle-energy flow-frame.
Fluid flow in nanopores: An examination of hydrodynamic boundary conditions
NASA Astrophysics Data System (ADS)
Sokhan, V. P.; Nicholson, D.; Quirke, N.
2001-08-01
Steady-state Poiseuille flow of a simple fluid in carbon slit pores under a gravity-like force is simulated using a realistic empirical many-body potential model for carbon. In this work we focus on the small Knudsen number regime, where the macroscopic equations are applicable, and simulate different wetting conditions by varying the strength of fluid-wall interactions. We show that fluid flow in a carbon pore is characterized by a large slip length even in the strongly wetting case, contrary to the predictions of Tolstoi's theory. When the surface density of wall atoms is reduced to values typical of a van der Waals solid, the streaming velocity profile vanishes at the wall, in accordance with earlier findings. From the velocity profiles we have calculated the slip length and by analyzing temporal profiles of the velocity components of particles colliding with the wall we obtained values of the Maxwell coefficient defining the fraction of molecules thermalized by the wall.
NASA Astrophysics Data System (ADS)
Weijermars, Ruud; Schmeling, Harro
1986-09-01
Scale model theory for constructing dynamically scaled analogue models of rock flowing in the solid state has until now assumed that the natural and model flows were both viscous. In viscous flows, at the very low Reynolds numbers ( Re ≪ 1) common in solid rocks, geometrical similarity is sufficient to achieve dynamic similarity between a homogeneous material (scale) model and its natural prototype. However, experiments on the rheology of natural rocks suggest that they flow predominantly as non-Newtonian strain rate softening materials at the characteristic geological strain rate 10 -14 s -1. Non-dimensionalisation of both the equation of motion and the constitutive flow law of non-Newtonian flows is carried out to investigate what criteria are required to achieve dynamic similarity. It is shown that dynamic similarity of non-Newtonian flows at low inertia (e.g., a rock with Re ≪ 1 and its model analogue) can only be attained if the steady-state flow curves of the model materials and the various rocks in the prototype have mutually similar shapes and slopes, and if these flows operate on similar parts of their respective flow curves. We term this the requirement of rheological similarity. Dynamic similarity of low inertia flows ( Re ≪ 1) in non-Newtonian continua is achieved if they are rheologically and geometrically similar. Additional criteria for dynamic similarity of low inertia flows in inhomogeneous media (with Newtonian or non-Newtonian subregions, or both) are formulated in section 5. Scaling of thermal properties is not included. Steady-state flow curves of common rocks are compiled in log stress-log strain rate space together with analogue materials suitable for modelling of solid state rock deformation. This compilation aids the selection of model materials with flow curves geometrically similar to those of rocks in the prototype. Laboratory scale models of rock flow should generally be constructed of materials which strain rate soften during
Visualization periodic flows in a continuously stratified fluid.
NASA Astrophysics Data System (ADS)
Bardakov, R.; Vasiliev, A.
2012-04-01
To visualize the flow pattern of viscous continuously stratified fluid both experimental and computational methods were developed. Computational procedures were based on exact solutions of set of the fundamental equations. Solutions of the problems of flows producing by periodically oscillating disk (linear and torsion oscillations) were visualized with a high resolutions to distinguish small-scale the singular components on the background of strong internal waves. Numerical algorithm of visualization allows to represent both the scalar and vector fields, such as velocity, density, pressure, vorticity, stream function. The size of the source, buoyancy and oscillation frequency, kinematic viscosity of the medium effects were traced in 2D an 3D posing problems. Precision schlieren instrument was used to visualize the flow pattern produced by linear and torsion oscillations of strip and disk in a continuously stratified fluid. Uniform stratification was created by the continuous displacement method. The buoyancy period ranged from 7.5 to 14 s. In the experiments disks with diameters from 9 to 30 cm and a thickness of 1 mm to 10 mm were used. Different schlieren methods that are conventional vertical slit - Foucault knife, vertical slit - filament (Maksoutov's method) and horizontal slit - horizontal grating (natural "rainbow" schlieren method) help to produce supplementing flow patterns. Both internal wave beams and fine flow components were visualized in vicinity and far from the source. Intensity of high gradient envelopes increased proportionally the amplitude of the source. In domains of envelopes convergence isolated small scale vortices and extended mushroom like jets were formed. Experiments have shown that in the case of torsion oscillations pattern of currents is more complicated than in case of forced linear oscillations. Comparison with known theoretical model shows that nonlinear interactions between the regular and singular flow components must be taken
Thermal Evolution and Fluid Flow in Planetesimals Inferred from Dawn Mission Observations of Ceres
NASA Astrophysics Data System (ADS)
Fu, R. R.; Ermakov, A. I.; Marchi, S.; Castillo-Rogez, J. C.; Raymond, C. A.; King, S. D.; Bland, M. T.; Russell, C. T.
2016-08-01
The dwarf planet Ceres is potentially an intact analog to volatile-rich chondrite parent bodies. Data from the NASA Dawn mission and our geophysical modeling suggest an ancient ocean and pervasive internal fluid flow.
Fluid flow in the osteocyte mechanical environment: a fluid-structure interaction approach.
Verbruggen, Stefaan W; Vaughan, Ted J; McNamara, Laoise M
2014-01-01
Osteocytes are believed to be the primary sensor of mechanical stimuli in bone, which orchestrate osteoblasts and osteoclasts to adapt bone structure and composition to meet physiological loading demands. Experimental studies to quantify the mechanical environment surrounding bone cells are challenging, and as such, computational and theoretical approaches have modelled either the solid or fluid environment of osteocytes to predict how these cells are stimulated in vivo. Osteocytes are an elastic cellular structure that deforms in response to the external fluid flow imposed by mechanical loading. This represents a most challenging multi-physics problem in which fluid and solid domains interact, and as such, no previous study has accounted for this complex behaviour. The objective of this study is to employ fluid-structure interaction (FSI) modelling to investigate the complex mechanical environment of osteocytes in vivo. Fluorescent staining of osteocytes was performed in order to visualise their native environment and develop geometrically accurate models of the osteocyte in vivo. By simulating loading levels representative of vigorous physiological activity ([Formula: see text] compression and 300 Pa pressure gradient), we predict average interstitial fluid velocities [Formula: see text] and average maximum shear stresses [Formula: see text] surrounding osteocytes in vivo. Interestingly, these values occur in the canaliculi around the osteocyte cell processes and are within the range of stimuli known to stimulate osteogenic responses by osteoblastic cells in vitro. Significantly our results suggest that the greatest mechanical stimulation of the osteocyte occurs in the cell processes, which, cell culture studies have indicated, is the most mechanosensitive area of the cell. These are the first computational FSI models to simulate the complex multi-physics mechanical environment of osteocyte in vivo and provide a deeper understanding of bone mechanobiology.
FLUID FLOW, SOLUTE MIXING AND PRECIPITATION IN POROUS MEDIA
Redden, George D; Y. Fang; T.D. Scheibe; A.M. Tartakovsky; Fox, Don T; Fujita, Yoshiko; White, Timothy A
2006-09-01
Reactions that lead to the formation of mineral precipitates, colloids or growth of biofilms in porous media often depend on the molecular-level diffusive mixing. For example, for the formation of mineral phases, exceeding the saturation index for a mineral is a minimum requirement for precipitation to proceed. Solute mixing frequently occurs at the interface between two solutions each containing one or more soluble reactants, particularly in engineered systems where contaminant degradation or modification or fluid flow are objectives. Although many of the fundamental component processes involved in the deposition or solubilization of solid phases are reasonably well understood, including precipitation equilibrium and kinetics, fluid flow and solute transport, the deposition of chemical precipitates, biofilms and colloidal particles are all coupled to flow, and the science of such coupled processes is not well developed. How such precipitates (and conversely, dissolution of solids) are distributed in the subsurface along flow paths with chemical gradients is a complex and challenging problem. This is especially true in systems that undergo rapid change where equilibrium conditions cannot be assumed, particularly in subsurface systems where reactants are introduced rapidly, compared to most natural flow conditions, and where mixing fronts are generated. Although the concept of dispersion in porous media is frequently used to approximate mixing at macroscopic scales, dispersion does not necessarily describe pore-level or molecular level mixing that must occur for chemical and biological reactions to be possible. An example of coupling between flow, mixing and mineral precipitation, with practical applications to controlling fluid flow or contaminant remediation in subsurface environments is shown in the mixing zone between parallel flowing solutions. Two- and three-dimensional experiments in packed-sand media were conducted where solutions containing calcium and
Direct modeling for computational fluid dynamics
NASA Astrophysics Data System (ADS)
Xu, Kun
2015-06-01
All fluid dynamic equations are valid under their modeling scales, such as the particle mean free path and mean collision time scale of the Boltzmann equation and the hydrodynamic scale of the Navier-Stokes (NS) equations. The current computational fluid dynamics (CFD) focuses on the numerical solution of partial differential equations (PDEs), and its aim is to get the accurate solution of these governing equations. Under such a CFD practice, it is hard to develop a unified scheme that covers flow physics from kinetic to hydrodynamic scales continuously because there is no such governing equation which could make a smooth transition from the Boltzmann to the NS modeling. The study of fluid dynamics needs to go beyond the traditional numerical partial differential equations. The emerging engineering applications, such as air-vehicle design for near-space flight and flow and heat transfer in micro-devices, do require further expansion of the concept of gas dynamics to a larger domain of physical reality, rather than the traditional distinguishable governing equations. At the current stage, the non-equilibrium flow physics has not yet been well explored or clearly understood due to the lack of appropriate tools. Unfortunately, under the current numerical PDE approach, it is hard to develop such a meaningful tool due to the absence of valid PDEs. In order to construct multiscale and multiphysics simulation methods similar to the modeling process of constructing the Boltzmann or the NS governing equations, the development of a numerical algorithm should be based on the first principle of physical modeling. In this paper, instead of following the traditional numerical PDE path, we introduce direct modeling as a principle for CFD algorithm development. Since all computations are conducted in a discretized space with limited cell resolution, the flow physics to be modeled has to be done in the mesh size and time step scales. Here, the CFD is more or less a direct
On some generalizations of the second grade fluid model
Massoudi, M.; Vaidya, A.
2008-01-01
In this article, we provide a brief review of some generalizations of the second grade fluid model. We discuss certain similarities between these fluids and fluids of higher grades, while also describing certain limitations of these models. The new models that we put forth are based upon some interesting experimental results which suggest that not only can normal stress coefficients depend upon the shear rate, but that this dependency is in fact not the same rate as that of shear viscosity variation with shear rate. We then discuss some steady flows of these generalized second grade fluid models.
On some generalizations of the second grade fluid model
Massoudi, Mehrdad; Vaidya, Ashwin
2008-07-01
In this article, we provide a brief review of some generalizations of the second grade fluid model. We discuss certain similarities between these fluids and fluids of higher grades, while also describing certain limitations of these models. The new models that we put forth are based upon some interesting experimental results which suggest that not only can normal stress coefficients depend upon the shear rate, but that this dependency is in fact not the same rate as that of shear viscosity variation with shear rate. We then discuss some steady flows of these generalized second grade fluid models.
NASA Astrophysics Data System (ADS)
Ague, J. J.
2004-12-01
Fluids are generally expected to be driven upward in the deep parts of orogens, but permeability heterogeneity and anisotropy must also be considered to properly interpret fluid infiltration and kinetic reaction histories preserved in the rock record. This paper focuses on new 2-D models of Darcian fluid flow incorporating permeability contrasts between rock units, the permeability tensor, and reactive fluid sources (e.g., dehydration). Factor of ten contrasts between the minimum and maximum permeability values in anisotropic rocks can strongly divert flow, but contrasts of as little as a factor of two still influence flow behavior. The first example considers fluid flow in subduction zone mélange, Syros, Greece. Geochemical evidence suggests that the interiors of meta-mafic blocks of oceanic crust in the mélange underwent limited fluid-rock reaction, despite extensive dehydration and decarbonation of the subduction complex. Modeling shows that if the blocks have lower permeability than the surrounding serpentine-rich matrix, then flow is diverted around the blocks resulting in little infiltration except at block margins, consistent with field relations. In this way, the subducted oceanic crust could preserve little evidence of fluid infiltration, even though considerable flow occurred through the mélange. The largest fluid fluxes are concentrated in matrix where blocks are in close proximity, and this effect increases as the anisotropy of the matrix increases. The lack of fluid infiltration into blocks could account for the observed limited metamorphism and strong kinetic overstepping of reactions that in some cases allowed preservation of ocean-floor mineral assemblages even at blueschist-eclogite facies conditions. The second example examines fluid flow through a folded sequence in which the direction of maximum permeability is parallel to the folded layering, and is based on field relations of Barrovian metamorphic sequences in CT, USA, and Scotland. As the
Tracing fluid flow in geothermal reservoirs
Rose, P.E.; Adams, M.C.
1997-12-31
A family of fluorescent compounds, the polycyclic aromatic sulfonates, were evaluated for application in intermediate- and high-temperature geothermal reservoirs. Whereas the naphthalene sulfonates were found to be very thermally stable and reasonably detectable, the amino-substituted naphthalene sulfonates were found to be somewhat less thermally stable, but much more detectable. A tracer test was conducted at the Dixie Valley, Nevada, geothermal reservoir using one of the substituted naphthalene sulfonates, amino G, and fluorescein. Four of 9 production wells showed tracer breakthrough during the first 200 days of the test. Reconstructed tracer return curves are presented that correct for the thermal decay of tracer assuming an average reservoir temperature of 227{degrees}C. In order to examine the feasibility of using numerical simulation to model tracer flow, we developed simple, two-dimensional models of the geothermal reservoir using the numerical simulation programs TETRAD and TOUGH2. By fitting model outputs to measured return curves, we show that numerical reservoir simulations can be calibrated with the tracer data. Both models predict the same order of elution, approximate tracer concentrations, and return curve shapes. Using these results, we propose a method for using numerical models to design a tracer test.
The dynamical regime of fluid flow at the core surface
NASA Astrophysics Data System (ADS)
Bloxham, Jeremy
1988-06-01
An alternative method for determining the fluid motion immediately beneath the core-mantle boundary is presented which is based on solving the full nonlinear core motions problem. This method is used to examine three dynamical hypotheses about the flow: (1) the steady motions hypothesis; (2) the geostrophic hypothesis; and (3) the toroidal flow hypothesis. Better fits to the field are obtained with the toroidal flows than with geostrophic flows, casting considerable doubt on the validity of the geostrophic hypothesis. Additionally, some indication is found that failure of the frozen-flux approximation, a concomitant assumption, may be a serious obstacle to obtaining reliable maps of the core fluid flow.
Applying uncertainty quantification to multiphase flow computational fluid dynamics
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.
Faybishenko, B.; Doughty, C.; Geller, J.
1998-07-01
Understanding subsurface flow and transport processes is critical for effective assessment, decision-making, and remediation activities for contaminated sites. However, for fluid flow and contaminant transport through fractured vadose zones, traditional hydrogeological approaches are often found to be inadequate. In this project, the authors examine flow and transport through a fractured vadose zone as a deterministic chaotic dynamical process, and develop a model of it in these terms. Initially, the authors examine separately the geometric model of fractured rock and the flow dynamics model needed to describe chaotic behavior. Ultimately they will put the geometry and flow dynamics together to develop a chaotic-dynamical model of flow and transport in a fractured vadose zone. They investigate water flow and contaminant transport on several scales, ranging from small-scale laboratory experiments in fracture replicas and fractured cores, to field experiments conducted in a single exposed fracture at a basalt outcrop, and finally to a ponded infiltration test using a pond of 7 by 8 m. In the field experiments, they measure the time-variation of water flux, moisture content, and hydraulic head at various locations, as well as the total inflow rate to the subsurface. Such variations reflect the changes in the geometry and physics of water flow that display chaotic behavior, which they try to reconstruct using the data obtained. In the analysis of experimental data, a chaotic model can be used to predic