Three-dimensional simulation of viscous-flow agglomerate sintering.
Kirchhof, M J; Schmid, H -J; Peukert, W
2009-08-01
The viscous-flow sintering of different agglomerate particle morphologies is studied by three-dimensional computer simulations based on the concept of fractional volume of fluid. For a fundamental understanding of particle sintering characteristics, the neck growth kinetics in agglomerate chains and in doublets consisting of differently sized primary particles is investigated. Results show that different sintering contacts in agglomerates even during the first stages are not completely independent from each other, even though differences are small. The neck growth kinetics of differently sized primary particles is determined by the smaller one up to a size difference by a factor of approximately 2, whereas for larger size differences, the kinetics becomes faster. In particular, the agglomerate sintering kinetics is investigated for particle chains of different lengths and for different particle morphologies each having ten primary particles and nine initial sintering contacts. For agglomerate chains, the kinetics approximately can be normalized by using the radius of the fully coalesced sphere. In general, different agglomerate morphologies show equal kinetics during the first sintering stages, whereas during advanced stages, compact morphologies show significantly faster sintering progress than more open morphologies. Hence, the overall kinetics cannot be described by simply using constant morphology correction factors such as fractal dimension or mean coordination number which are used in common sintering models. However, for the first stages of viscous-flow agglomerate sintering, which are the most important for many particle processes, a sintering equation is presented. Although we use agglomerates consisting of spherical primary particles, our methodology can be applied to other aggregate geometries as well.
Three-dimensional attached viscous flow basic principles and theoretical foundations
Hirschel, Ernst Heinrich; Kordulla, Wilhelm
2014-01-01
Viscous flow is usually treated in the frame of boundary-layer theory and as a two-dimensional flow. At best, books on boundary layers provide the describing equations for three-dimensional boundary layers, and solutions only for certain special cases. This book presents the basic principles and theoretical foundations of three-dimensional attached viscous flows as they apply to aircraft of all kinds. Though the primary flight speed range is that of civil air transport vehicles, flows past other flying vehicles up to hypersonic speeds are also considered. Emphasis is put on general three-dimensional attached viscous flows and not on three-dimensional boundary layers, as this wider scope is necessary in view of the theoretical and practical problems that have to be overcome in practice. The specific topics covered include weak, strong, and global interaction; the locality principle; properties of three-dimensional viscous flows; thermal surface effects; characteristic properties; wall compatibility con...
Swarming in viscous fluids: Three-dimensional patterns in swimmer- and force-induced flows
Chuang, Yao-Li; Chou, Tom; D'Orsogna, Maria R.
2016-04-01
We derive a three-dimensional theory of self-propelled particle swarming in a viscous fluid environment. Our model predicts emergent collective behavior that depends critically on fluid opacity, mechanism of self-propulsion, and type of particle-particle interaction. In "clear fluids" swimmers have full knowledge of their surroundings and can adjust their velocities with respect to the lab frame, while in "opaque fluids" they control their velocities only in relation to the local fluid flow. We also show that "social" interactions that affect only a particle's propensity to swim towards or away from neighbors induces a flow field that is qualitatively different from the long-ranged flow fields generated by direct "physical" interactions. The latter can be short-ranged but lead to much longer-ranged fluid-mediated hydrodynamic forces, effectively amplifying the range over which particles interact. These different fluid flows conspire to profoundly affect swarm morphology, kinetically stabilizing or destabilizing swarm configurations that would arise in the absence of fluid. Depending upon the overall interaction potential, the mechanism of swimming ( e.g., pushers or pullers), and the degree of fluid opaqueness, we discover a number of new collective three-dimensional patterns including flocks with prolate or oblate shapes, recirculating pelotonlike structures, and jetlike fluid flows that entrain particles mediating their escape from the center of mill-like structures. Our results reveal how the interplay among general physical elements influence fluid-mediated interactions and the self-organization, mobility, and stability of new three-dimensional swarms and suggest how they might be used to kinetically control their collective behavior.
A three-dimensional viscous/potential flow interaction analysis method for multi-element wings
Dvorak, F. A.; Woodward, F. A.; Maskew, B.
1977-01-01
An analysis method and computer program were developed for the calculation of the viscosity dependent aerodynamic characteristics of multi-element, finite wings in incompressible flow. A fully-three dimensional potential flow program is used to determine the inviscid pressure distribution about the configuration. The potential flow program uses surface source and vortex singularities to represent the inviscid flow. The method is capable of analysing configurations having at most one slat, a main element, and two slotted flaps. Configurations are limited to full span slats or flaps. The configuration wake is allowed to relax as a force free wake, although roll up is not allowed at this time. Once the inviscid pressure distribution is calculated, a series of boundary layer computations are made along streamwise strips.
Simulation of three-dimensional viscous flow within a multistage turbine
Adamczyk, John J.; Celestina, Mark L.; Beach, Tim A.; Barnett, Mark
1989-01-01
This work outlines a procedure for simulating the flow field within multistage turbomachinery which includes the effects of unsteadiness, compressibility, and viscosity. The associated modeling equations are the average passage equation system which governs the time-averaged flow field within a typical passage of a blade row embedded within a multistage configuration. The results from a simulation of a low aspect ratio stage and a one-half turbine will be presented and compared with experimental measurements. It will be shown that the secondary flow field generated by the rotor causes the aerodynamic performance of the downstream vane to be significantly different from that of an isolated blade row.
Thoughts on the chimera method of simulation of three-dimensional viscous flow
Steger, Joseph L.
1991-01-01
The chimera overset grid is reviewed and discussed relative to other procedures for simulating flow about complex configurations. It is argued that while more refinement of the technique is needed, current schemes are competitive to unstructured grid schemes and should ultimately prove more useful.
Araujo, Vitor; Viana, Marcelo
2010-01-01
In this book, the authors present the elements of a general theory for flows on three-dimensional compact boundaryless manifolds, encompassing flows with equilibria accumulated by regular orbits. The book aims to provide a global perspective of this theory and make it easier for the reader to digest the growing literature on this subject. This is not the first book on the subject of dynamical systems, but there are distinct aspects which together make this book unique. Firstly, this book treats mostly continuous time dynamical systems, instead of its discrete counterpart, exhaustively treated
Ramzan, Muhammad
2015-01-01
The present exploration discusses the influence of Newtonian heating on the magnetohydrodynamic (MHD) three dimensional couple stress nanofluid past a stretching surface. Viscous dissipation and Joule heating effects are also considered. Moreover, the nanofluid model includes the combined effects of thermophoresis and Brownian motion. Using an appropriate transformation, the governing non linear partial differential equations are converted into nonlinear ordinary differential equations. Series solutions using Homotopy Analysis method (HAM) are computed. Plots are presented to portrait the arising parameters in the problem. It is seen that an increase in conjugate heating parameter results in considerable increase in the temperature profile of the stretching wall. Skin friction coefficient, local Nusselt and local Sherwood numbers tabulated and analyzed. Higher values of conjugate parameter, Thermophoresis parameter and Brownian motion parameter result in enhancement of temperature distribution.
Energy Technology Data Exchange (ETDEWEB)
Kirtley, K.R.
1988-10-01
A new coupled parabolic-marching method was developed to solve the three-dimensional incompressible Navier-Stokes equation for turbulent turbomachinery flows. Earlier space-marching methods were analyzed to determine their global stability during multiple passes of the computational domain. The methods were found to be unconditionally unstable even when an extra equation for the pressure, namely the Poisson equation for the pressure, was used between passes of the domain. Relaxation of one constraint during the solution process was found to be necessary for the successful calculation of a complex flow.Thus, the method of pseudocompressibility was introduced into the partially parabolized Navier-Stokes equation to relax the mass flow constraint during a forward-marching integration as well as globally stable during successive passes of the domain. With consistent discretization, the new method was found to be convergent.
International Nuclear Information System (INIS)
Umegaki, Kikuo; Miki, Kazuyoshi
1990-01-01
A numerical method is developed to solve three-dimensional incompressible viscous flow in complicated geometry using curvilinear coordinate transformation and domain decomposition technique. In this approach, a complicated flow domain is decomposed into several subdomains, each of which has an overlapping region with neighboring subdomains. Curvilinear coordinates are numerically generated in each subdomain using the boundary-fitted coordinate transformation technique. The modified SMAC scheme is developed to solve Navier-Stokes equations in which the convective terms are discretized by the QUICK method. A fully vectorized computer program is developed on the basis of the proposed method. The program is applied to flow analysis in a semicircular curved, 90deg elbow and T-shape branched pipes. Computational time with the vector processor of the HITAC S-810/20 supercomputer system, is reduced to 1/10∼1/20 of that with a scalar processor. (author)
Three-dimensional viscous fingering of miscible fluids in porous media
Suekane, Tetsuya; Ono, Jei; Hyodo, Akimitsu; Nagatsu, Yuichiro
2017-10-01
Viscous fingering is a flow instability that is induced at the displacement front when a less-viscous fluid (LVF) displaces a more-viscous fluid (MVF). Because of the opaque nature of porous media, most experimental investigations of the structure of viscous fingering and its development in time have been limited to two-dimensional porous media or Hele-Shaw cells. In this study, we investigate the three-dimensional characteristics of viscous fingering in porous media using a microfocused x-ray computer tomography (CT) scanner. Similar to two-dimensional experiments, characteristic events such as tip-splitting, shielding, and coalescence were observed in three-dimensional viscous fingering as well. With an increase in the Péclet number at a fixed viscosity ratio, M , the fingers appearing on the interface tend to be fine; however, the locations of the tips of the fingers remain the same for the same injected volume of the LVF. The finger extensions increase in proportion to ln M , and the number of fingers emerging at the initial interface increases with M . This fact agrees qualitatively with linear stability analyses. Within the fingers, the local concentration of NaI, which is needed for the x-ray CT scanner, linearly decreases, whereas it sharply decreases at the tips of the fingers. A locally high Péclet number as well as unsteady motions in lateral directions may enhance the dispersion at the tips of the fingers. As the viscosity ratio increases, the efficiency of each sweep monotonically decreases and reaches an asymptotic state; in addition, the degree of mixing increases with the viscosity ratio. For high flow rates, the asymptotic value of the sweep efficiency is low for high viscosity ratios, while there is no clear dependence of the asymptotic value on the Péclet number.
Three dimensional viscous analysis of a hypersonic inlet
Reddy, D. R.; Smith, G. E.; Liou, M.-F.; Benson, Thomas J.
1989-01-01
The flow fields in supersonic/hypersonic inlets are currently being studied at NASA Lewis Research Center using 2- and 3-D full Navier-Stokes and Parabolized Navier-Stokes solvers. These tools have been used to analyze the flow through the McDonnell Douglas Option 2 inlet which has been tested at Calspan in support of the National Aerospace Plane Program. Comparisons between the computational and experimental results are presented. These comparisons lead to better overall understanding of the complex flows present in this class of inlets. The aspects of the flow field emphasized in this work are the 3-D effects, the transition from laminar to turbulent flow, and the strong nonuniformities generated within the inlet.
Pan, Ronghua; Zhou, Yi; Zhu, Yi
2018-02-01
In this paper, we study the global existence of classical solutions to the three dimensional incompressible viscous magneto-hydrodynamical system without magnetic diffusion on periodic boxes, that is, with periodic boundary conditions. We work in Eulerian coordinates and employ a time-weighted energy estimate to prove the global existence result, under the assumptions that the initial magnetic field is close enough to an equilibrium state and the initial data have some symmetries.
Magnetic field effect on a three-dimensional mixed convective flow ...
African Journals Online (AJOL)
An analytical solution to the problem of the MHD free and forced convection three dimensional flow of an incompressible viscous electrically conducting fluid with mass transfer along a vertical porous plate with transverse sinusoidal suction velocity is presented. A uniform magnetic field is assumed to be applied transversely ...
Three-dimensional viscous-inviscid coupling method for wind turbine computations
DEFF Research Database (Denmark)
Ramos García, Néstor; Sørensen, Jens Nørkær; Shen, Wen Zhong
2016-01-01
role in the predictions of blade aerodynamics and wake dynamics, especially at high angles of attack just before and after boundary layer separation takes place. The present code is validated in detail against the well-known MEXICO experiment and a set of non-rotating cases. Copyright © 2014 John Wiley......In this paper, a computational model for predicting the aerodynamic behavior of wind turbine wakes and blades subjected to unsteady motions and viscous effects is presented. The model is based on a three-dimensional panel method using a surface distribution of quadrilateral sources and doublets...
Three-dimensional flow and turbulence structure in electrostatic precipitator
DEFF Research Database (Denmark)
Ullum, Thorvald Uhrskov; Larsen, Poul Scheel; Özcan, Oktay
2002-01-01
and bulk velocity U0 on secondary flows and turbulence levels and structures due to the action of the three-dimensional electrostatic field on the charged gas. At constant bulk velocity (U0 = 1 m/s) and current density (Jm = 0.4 mA/m2), secondary flows in the form of rolls of axial vorticity with swirl...
Two-dimensional turbulence in three-dimensional flows
Xia, H.; Francois, N.
2017-11-01
This paper presents a review of experiments performed in three-dimensional flows that show behaviour associated with two-dimensional turbulence. Experiments reveal the presence of the inverse energy cascade in two different systems, namely, flows in thick fluid layers driven electromagnetically and the Faraday wave driven flows. In thick fluid layers, large-scale coherent structures can shear off the vertical eddies and reinforce the planarity of the flow. Such structures are either self-generated or externally imposed. In the Faraday wave driven flows, a seemingly three-dimensional flow is shown to be actually two-dimensional when it is averaged over several Faraday wave periods. In this system, a coupling between the wave motion and 2D hydrodynamic turbulence is uncovered.
Singularities at rims in three-dimensional fluid flow
Driesen, C.H.; Kuerten, Johannes G.M.
1999-01-01
Asymptotic solutions are presented for Stokes flow near circular rims in three-dimensional geometries. Using nonstandard toroidal coordinates, asymptotic analytical expressions are derived for different corner angles. In comparison to the two-dimensional case, an extra critical corner angle value is
Analysis and visualization of complex unsteady three-dimensional flows
Van Dalsem, William R.; Buning, Pieter G.; Dougherty, F. Carroll; Smith, Merritt H.
1989-01-01
Flow field animation is the natural choice as a tool in the analysis of the numerical simulations of complex unsteady three-dimensional flows. The PLOT4D extension of the widely used PLOT3D code to allow the interactive animation of a broad range of flow variables was developed and is presented. To allow direct comparison with unsteady experimental smoke and dye flow visualization, the code STREAKER was developed to produce time accurate streaklines. Considerations regarding the development of PLOT4D and STREAKER, and example results are presented.
Three-dimensional flow measurements in a tesla turbine rotor
Fuchs, Thomas; Schosser, Constantin; Hain, Rainer; Kaehler, Christian
2015-11-01
Tesla turbines are fluid mechanical devices converting flow energy into rotation energy by two physical effects: friction and adhesion. The advantages of the tesla turbine are its simple and robust design, as well as its scalability, which makes it suitable for custom power supply solutions, and renewable energy applications. To this day, there is a lack of experimental data to validate theoretical studies, and CFD simulations of these turbines. This work presents a comprehensive analysis of the flow through a tesla turbine rotor gap, with a gap height of only 0.5 mm, by means of three-dimensional Particle Tracking Velocimetry (3D-PTV). For laminar flows, the experimental results match the theory very well, since the measured flow profiles show the predicted second order parabolic shape in radial direction and a fourth order behavior in circumferential direction. In addition to these laminar measurements, turbulent flows at higher mass flow rates were investigated.
Langlois, William E
2014-01-01
Leonardo wrote, 'Mechanics is the paradise of the mathematical sciences, because by means of it one comes to the fruits of mathematics' ; replace 'Mechanics' by 'Fluid mechanics' and here we are." - from the Preface to the Second Edition Although the exponential growth of computer power has advanced the importance of simulations and visualization tools for elaborating new models, designs and technologies, the discipline of fluid mechanics is still large, and turbulence in flows remains a challenging problem in classical physics. Like its predecessor, the revised and expanded Second Edition of this book addresses the basic principles of fluid mechanics and solves fluid flow problems where viscous effects are the dominant physical phenomena. Much progress has occurred in the nearly half a century that has passed since the edition of 1964. As predicted, aspects of hydrodynamics once considered offbeat have risen to importance. For example, the authors have worked on problems where variations in viscosity a...
Three-dimensional flows in a transonic compressor rotor
Reid, Lonnie; Celestina, Mark L.; Dewitt, Kenneth; Keith, Theo
1991-01-01
This study involves an experimental and numerical investigation of the three-dimensional flows in a transonic compressor rotor. A variety of data which could be used, in a complementary fashion, to validate/calibrate the computational fluid dynamics turbomachinery code and improve understanding of the flow physics, were acquired. Detailed radial survey data which consisted of total pressure, total temperature, static pressure and flow angle were obtained at stations upstream and downstream of the rotor blade. Detailed velocity and turbulence profiles were obtained upstream of the rotor and used as the upstream boundary conditions for the numerical analysis. Calibrated flush-mounted hot film probes were used to measure wall shear stress on the hub and casing walls upstream of the rotor. The blade-to-blade shear-stress angle distributions were obtained at two axial locations on the rotor casing, using flush-mounted hot film probes. A numerical analysis conducted using a three-dimensional Navier-Stokes code was compared with the experimental results.
Vocal Fold Pathologies and Three-Dimensional Flow Separation Phenomena
Apostoli, Adam G.; Weiland, Kelley S.; Plesniak, Michael W.
2013-11-01
Polyps and nodules are two different pathologies, which are geometric abnormalities that form on the medial surface of the vocal folds, and have been shown to significantly disrupt a person's ability to communicate. Although the mechanism by which the vocal folds self-oscillate and the three-dimensional nature of the glottal jet has been studied, the effect of irregularities caused by pathologies is not fully understood. Examining the formation and evolution of vortical structures created by a geometric protuberance is important, not only for understanding the aerodynamic forces exerted by these structures on the vocal folds, but also in the treatment of the above-mentioned pathological conditions. Using a wall-mounted prolate hemispheroid with a 2:1 aspect ratio in cross flow, the present investigation considers three-dimensional flow separation induced by a model vocal fold polyp. Building on previous work using skin friction line visualization, both the velocity flow field and wall pressure measurements around the model polyp are presented and compared. Supported by the National Science Foundation, Grant No. CBET-1236351 and GW Center for Biomimetics and Bioinspired Engineering (COBRE).
Miao, Sha; Hendrickson, Kelli; Liu, Yuming
2017-12-01
This work presents a Fully-Coupled Immersed Flow (FCIF) solver for the three-dimensional simulation of fluid-fluid interaction by coupling two distinct flow solvers using an Immersed Boundary (IB) method. The FCIF solver captures dynamic interactions between two fluids with disparate flow properties, while retaining the desirable simplicity of non-boundary-conforming grids. For illustration, we couple an IB-based unsteady Reynolds Averaged Navier Stokes (uRANS) simulator with a depth-integrated (long-wave) solver for the application of slug development with turbulent gas and laminar liquid. We perform a series of validations including turbulent/laminar flows over prescribed wavy boundaries and freely-evolving viscous fluids. These confirm the effectiveness and accuracy of both one-way and two-way coupling in the FCIF solver. Finally, we present a simulation example of the evolution from a stratified turbulent/laminar flow through the initiation of a slug that nearly bridges the channel. The results show both the interfacial wave dynamics excited by the turbulent gas forcing and the influence of the liquid on the gas turbulence. These results demonstrate that the FCIF solver effectively captures the essential physics of gas-liquid interaction and can serve as a useful tool for the mechanistic study of slug generation in two-phase gas/liquid flows in channels and pipes.
Lagrangian chaos in three- dimensional steady buoyancy-driven flows
Contreras, Sebastian; Speetjens, Michel; Clercx, Herman
2016-11-01
Natural convection plays a key role in fluid dynamics owing to its ubiquitous presence in nature and industry. Buoyancy-driven flows are prototypical systems in the study of thermal instabilities and pattern formation. The differentially heated cavity problem has been widely studied for the investigation of buoyancy-induced oscillatory flow. However, far less attention has been devoted to the three-dimensional Lagrangian transport properties in such flows. This study seeks to address this by investigating Lagrangian transport in the steady flow inside a cubic cavity differentially-heated from the side. The theoretical and numerical analysis expands on previously reported similarities between the current flow and lid-driven flows. The Lagrangian dynamics are controlled by the Péclet number (Pe) and the Prandtl number (Pr). Pe controls the behaviour qualitatively in that growing Pe progressively perturbs the integable state (Pe =0), thus paving the way to chaotic dynamics. Pr plays an entirely quantitative role in that Pr1 amplifies and diminishes, respectively, the perturbative effect of non-zero Pe. S.C. acknowledges financial support from Consejo Nacional de Ciencia y Tecnología (CONACYT).
Self-organization in three-dimensional compressible magnetohydrodynamic flow
International Nuclear Information System (INIS)
Horiuchi, Ritoku; Sato, Tetsuya.
1987-07-01
A three-dimensional self-organization process of a compressible dissipative plasma with a velocity-magnetic field correlation is investigated in detail by means of a variational method and a magnetohydrodynamic simulation. There are two types of relaxation, i.e., fast relaxation in which the cross helicity is not conserved, and slow relaxation in which the cross helicity is approximately conserved. In the slow relaxation case the cross helicity consists of two components with opposite sign which have almost the same amplitude in the large wavenumber region. In both cases the system approaches a high correlation state, dependent on the initial condition. These results are consistent with an observational data of the solar wind. Selective dissipation of magnetic energy, normal cascade of magnetic energy spectrum and inverse cascade of magnetic helicity spectrum are observed for the sub-Alfvenic flow case as was previously observed for the zero flow case. When the flow velocity is super-Alfvenic, the relaxation process is significantly altered from the zero flow case. (author)
Turbulent Flows Over Three-Dimensional Shark Skin
Boomsma, Aaron; Wen, Li; Lauder, George; Sotiropoulos, Fotis
2012-11-01
Shark skin is covered with thousands of small tooth-like structures called denticles. It has long been hypothesized that denticles act as riblets do in a turbulent boundary layer and help reduce friction drag and enhance shark swimming efficiency. We employ the Curvilinear Immersed Boundary (CURVIB) method (Ge and Sotiropoulos, J. Comp. Physics, 2008) to carry out high-resolution large eddy simulations of turbulent flow past a series of anatomically realistic shark denticles mounted on a flat plate. The denticle shapes used in our simulations were obtained by scanning Mako Short Fin shark skin with micro-CT. The computed results are analyzed to elucidate the three-dimensional structure of the flow past the denticles and identify possible drag reduction mechanics. Drag measurements obtained in a laboratory flume for various denticle spacings and arrangements are also reported and analyzed in tandem with the LES results to explore similarities between shark skin and engineered riblets. Computational Resources were provided by the University of Minnesota Supercomputing Institute.
Analysis of Three-Dimensional Viscous Internal Flows.
1985-12-01
Coupled Strongly-Implicit and Multigrid Methods ," Multigrid Methods , NASA-CP-2202. Ghia, U., Ghia, K.N. and Shin, C.T. (1982), "High-Re Solutions for...Non-Uniform Curvilinear Grids, Time Marching and A Direct Method," Multigrid Methods , NASA CP-2202, October 1981. Osswald, G.A., Ghia, K.N. and Ghia, U...K.N. and Shin, C.T., "Solution of Incompressible Navier-Stokes Equations by Coupled Strongly-Implicit and Multigrid Methods ," Multigrid Methods , NASA
Parallel Simulation of Three-Dimensional Free Surface Fluid Flow Problems
International Nuclear Information System (INIS)
BAER, THOMAS A.; SACKINGER, PHILIP A.; SUBIA, SAMUEL R.
1999-01-01
Simulation of viscous three-dimensional fluid flow typically involves a large number of unknowns. When free surfaces are included, the number of unknowns increases dramatically. Consequently, this class of problem is an obvious application of parallel high performance computing. We describe parallel computation of viscous, incompressible, free surface, Newtonian fluid flow problems that include dynamic contact fines. The Galerkin finite element method was used to discretize the fully-coupled governing conservation equations and a ''pseudo-solid'' mesh mapping approach was used to determine the shape of the free surface. In this approach, the finite element mesh is allowed to deform to satisfy quasi-static solid mechanics equations subject to geometric or kinematic constraints on the boundaries. As a result, nodal displacements must be included in the set of unknowns. Other issues discussed are the proper constraints appearing along the dynamic contact line in three dimensions. Issues affecting efficient parallel simulations include problem decomposition to equally distribute computational work among a SPMD computer and determination of robust, scalable preconditioners for the distributed matrix systems that must be solved. Solution continuation strategies important for serial simulations have an enhanced relevance in a parallel coquting environment due to the difficulty of solving large scale systems. Parallel computations will be demonstrated on an example taken from the coating flow industry: flow in the vicinity of a slot coater edge. This is a three dimensional free surface problem possessing a contact line that advances at the web speed in one region but transitions to static behavior in another region. As such, a significant fraction of the computational time is devoted to processing boundary data. Discussion focuses on parallel speed ups for fixed problem size, a class of problems of immediate practical importance
Czech Academy of Sciences Publication Activity Database
Petrov, A. G.; Kharlamov, Alexander A.
2013-01-01
Roč. 48, č. 5 (2013), s. 577-587 ISSN 0015-4628 R&D Projects: GA ČR(CZ) GA103/09/2066 Grant - others:Development of the Scientific Potential of the Higher Schoo(RU) 2.1.2/3604; Russian Foundation for Basic Research(RU) 11- 01-005355 Institutional support: RVO:67985874 Keywords : lubrication layer theory * viscous and inviscid fluids * thin layer * vicinity of a contact * three-dimensional problems Subject RIV: BK - Fluid Dynamics Impact factor: 0.320, year: 2013
Measurements of the three-dimensional oscillatory flow in a double bifurcation
Nemes, Andras; Jalal, Sahar; van de Moortele, Tristan; Coletti, Filippo
2015-11-01
Above a certain ventilation frequency, the unsteady nature of the respiratory flow becomes apparent, and inhalation and exhalation cannot be approximated as quasi-stationary processes. This is especially important in the upper and central airways, where length and velocity scales are the largest, making inertia and acceleration effects dominant over viscous dissipation. We experimentally investigate the primary features of the oscillatory flow through a symmetric double bifurcation which models the self-similar branching of the human bronchial tree. We consider a range of Reynolds and Womersley numbers relevant to physiological conditions between the trachea and the lobar bronchi. Three-component, three-dimensional velocity fields are acquired at multiple phases within the ventilation cycle using magnetic resonance imaging (MRI), and are complemented with instantaneous two-dimensional fields obtained by particle image velocimetry (PIV). The phase-averaged volumetric data provide a description of the rich flow topology, characterizing the main secondary flow structures and their spatio-temporal evolution. The instantaneous measurements reveal some of the dynamics of the laminar-to-turbulent transition in the bifurcations, and its aperiodicity throughout the respiratory cycle.
Effective Rheology of Two-Phase Flow in Three-Dimensional Porous Media: Experiment and Simulation.
Sinha, Santanu; Bender, Andrew T; Danczyk, Matthew; Keepseagle, Kayla; Prather, Cody A; Bray, Joshua M; Thrane, Linn W; Seymour, Joseph D; Codd, Sarah L; Hansen, Alex
2017-01-01
We present an experimental and numerical study of immiscible two-phase flow of Newtonian fluids in three-dimensional (3D) porous media to find the relationship between the volumetric flow rate ( Q ) and the total pressure difference ([Formula: see text]) in the steady state. We show that in the regime where capillary forces compete with the viscous forces, the distribution of capillary barriers at the interfaces effectively creates a yield threshold ([Formula: see text]), making the fluids reminiscent of a Bingham viscoplastic fluid in the porous medium. In this regime, Q depends quadratically on an excess pressure drop ([Formula: see text]). While increasing the flow rate, there is a transition, beyond which the overall flow is Newtonian and the relationship is linear. In our experiments, we build a model porous medium using a column of glass beads transporting two fluids, deionized water and air. For the numerical study, reconstructed 3D pore networks from real core samples are considered and the transport of wetting and non-wetting fluids through the network is modeled by tracking the fluid interfaces with time. We find agreement between our numerical and experimental results. Our results match with the mean-field results reported earlier.
Computation of Viscous Incompressible Flows
Kwak, Dochan
2011-01-01
This monograph is intended as a concise and self-contained guide to practitioners and graduate students for applying approaches in computational fluid dynamics (CFD) to real-world problems that require a quantification of viscous incompressible flows. In various projects related to NASA missions, the authors have gained CFD expertise over many years by developing and utilizing tools especially related to viscous incompressible flows. They are looking at CFD from an engineering perspective, which is especially useful when working on real-world applications. From that point of view, CFD requires two major elements, namely methods/algorithm and engineering/physical modeling. As for the methods, CFD research has been performed with great successes. In terms of modeling/simulation, mission applications require a deeper understanding of CFD and flow physics, which has only been debated in technical conferences and to a limited scope. This monograph fills the gap by offering in-depth examples for students and engine...
Three-dimensional investigation of the two-phase flow structure in a bubbly pipe flow
International Nuclear Information System (INIS)
Schmidl, W.; Hassan, Y.A.; Ortiz-Villafuerte, J.
1996-01-01
Particle image velocimetry (PIV) is a nonintrusive measurement technique that can be used to study the structure of various fluid flows. PIV is used to measure the time-varying, full-field velocity data of a particle-seeded flow field within either a two-dimensional plane or three-dimensional volume. PIV is a very efficient measurement technique since it can obtain both qualitative and quantitative spatial information about the flow field being studied. The quantitative spatial velocity information can be further processed into information of flow parameters such as vorticity and turbulence over extended areas. The objective of this study was to apply recent advances and improvements in the PIV flow measurement technique to the full-field, nonintrusive analysis of a three-dimensional, two-phase fluid flow system in such a manner that both components of the two-phase system could be experimentally quantified
Quasi-Three-Dimensional Analysis Of Turbine Flow
Hsu, Wayne W.
1988-01-01
Computer program reduces computer time and treats multiple elements. Improved design-analysis program for turbomachinery applied to multiple turbine elements simultaneously. Enables continuous and coherent analyses rather than previous piece-meal analyses of flow fields. Effects of upstream elements on downstream flow taken into account automatically.
A three-dimensional autonomous nonlinear dynamical system modelling equatorial ocean flows
Ionescu-Kruse, Delia
2018-04-01
We investigate a nonlinear three-dimensional model for equatorial flows, finding exact solutions that capture the most relevant geophysical features: depth-dependent currents, poleward or equatorial surface drift and a vertical mixture of upward and downward motions.
Numerical Calculation of the Three-Dimensional Swirling Flow Inside the Centrifugal Pump Volutes
Directory of Open Access Journals (Sweden)
E. Cezmi Nursen
2003-01-01
Full Text Available The flow inside the volute of a centrifugal pump is threedimensional and, depending upon the position of the inlet relative to the cross-section center line, a single or double swirling flow occurs. The purpose of this study was the calculation of the three-dimensional swirling flow inside the centrifugal pump volute.
Wu, J.; Shu, C.
2010-07-01
The recently proposed boundary condition-enforced immersed boundary-lattice Boltzmann method (IB-LBM) [14] is improved in this work to simulate three-dimensional incompressible viscous flows. In the conventional IB-LBM, the restoring force is pre-calculated, and the non-slip boundary condition is not enforced as compared to body-fitted solvers. As a result, there is a flow penetration to the solid boundary. This drawback was removed by the new version of IB-LBM [14], in which the restoring force is considered as unknown and is determined in such a way that the non-slip boundary condition is enforced. Since Eulerian points are also defined inside the solid boundary, the computational domain is usually regular and the Cartesian mesh is used. On the other hand, to well capture the boundary layer and in the meantime, to save the computational effort, we often use non-uniform mesh in IB-LBM applications. In our previous two-dimensional simulations [14], the Taylor series expansion and least squares-based lattice Boltzmann method (TLLBM) was used on the non-uniform Cartesian mesh to get the flow field. The final expression of TLLBM is an algebraic formulation with some weighting coefficients. These coefficients could be computed in advance and stored for the following computations. However, this way may become impractical for 3D cases as the memory requirement often exceeds the machine capacity. The other way is to calculate the coefficients at every time step. As a result, extra time is consumed significantly. To overcome this drawback, in this study, we propose a more efficient approach to solve lattice Boltzmann equation on the non-uniform Cartesian mesh. As compared to TLLBM, the proposed approach needs much less computational time and virtual storage. Its good accuracy and efficiency are well demonstrated by its application to simulate the 3D lid-driven cubic cavity flow. To valid the combination of proposed approach with the new version of IBM [14] for 3D flows
Large Eddy Simulation of turbulent flow fields over three- dimensional alluvial dunes
Hardy, R. J.; Parsons, D. R.; Best, J.; Reesink, A. J. H.; Ockelford, A.
2016-12-01
Flow over fluvial dunes has been extensively studied and there is general understanding of the nature of the flow field over two dimensional dunes under equilibrium flow conditions. However, fluvial systems typically experience unsteady flow and therefore the sediment-water interface is constantly reorganizing to form complex three-dimensional morphologies (ripples, dunes and bar forms). Here we report on a numerical experiment which predicts flow over three dimensional dunes using Large Eddy Simulation (LES). Bed topography generated through flume experiments, where fine sand was water worked under a range of unsteady hydraulic conditions to generate quasi-equilibrium three dimensional bed forms, was measured with terrestrial LiDAR to create digital elevation models. This topography was then incorporated into a LES model, with a wall-adapting local eddy-viscosity turbulence model, through a Mass Flux Scaling algorithm, to generate three dimensional, high resolution space time prediction of flow over naturally formed dunes. The numerically predicted flows were analysed by standard Reynolds decomposition approaches, Eulerian and Lagrangian coherent flow structure identification methods and proper orthogonal decomposition. The results show that superimposed bed forms can cause changes in the nature of the classical separated flow regions and turbulence field. In particular, the number of locations where vortices are shed increase which causes coalescence of vortices. This increases the rate of transfer of turbulent kinetic energy into smaller scales. This has significant implications for the time dependent prediction of shear stress and as such for sediment transport dynamics which are required for an improved process understanding of three-dimensional bed form adjustment.
The importance of three dimensional dune morphology on the time dependent flow field
Hardy, Richard; Parsons, Dan; Reesink, Arnold; Best, Jim
2017-04-01
The flow field over dunes has been extensively studied and there is general understanding of the nature of the flow over dunes formed over two dimensional dunes under equilibrium flow conditions. This model is typically used to explain flow fields over all dunes fields. However, fluvial systems typically experience unsteady flow and therefore the sediment-water interface is constantly reorganizing to form complex three-dimensional morphologies (ripples, dunes and bar forms). Here we investigate how flow over natural three dimensional dunes differs from the accepted model of flow of two dimensional dunes. A series of experiments were undertaken in a flume where fine sand was water worked under a range of unsteady hydraulic conditions to generate quasi-equilibrium three dimensional bed forms. On four occasions, the flume was drained and the bed topography measured with terrestrial LiDAR to create digital elevation models (DEM). Here to demonstrate the approach we choose the DEM with the greatest topographic variation and apply a new Large Eddy Simulation model with an wall-adapting local eddy-viscosity (WALE) turbulence model and a non-linear higher-order numerical differencing scheme. This provided a three dimensional time dependent prediction of the flow field over the static three-dimensional dune morphology at millimeter and hertz scale resolution. The numerically predicted flows were analyzed by standard Reynolds decomposition approaches and Eulerian and Lagrangian coherent flow structure identification methods. The results show that the superimposed bed forms can cause changes in the nature of the classical separated flow regions, in particularly the number of locations where vortices are shed and the points of flow reattachment. Coalescence of vortices generated downstream and can be seen to move to the free surface and form kolk signatures. These structures also correlate in space and time showing a clear flow morphology feedback. The modified flow field
Bradbrook, Kathryn Frances
1999-01-01
This thesis investigates controls on and the nature of three-dimensional flow structures at river channel confluences. Previous work has shown that junction angle is an important control on the flow patterns at channel junctions since it affects the degree of curvature of flow from each tributary and sets up secondary circulation cells similar to those in meander bends. Recent work has highlighted the common occurrence of, and importance of, bed discordance at river confluences due to a signi...
Experimental investigation of three-dimensional flow instabilities in a rotating lid-driven cavity
DEFF Research Database (Denmark)
Sørensen, Jens Nørkær; Naumov, I.; Mikkelsen, Robert Flemming
2006-01-01
liquid. For the first time the onset of three-dimensionality and transition are analysed by combining the high spatial resolution of Particle Image Velocimetry (PIV) and the temporal accuracy of Laser Doppler Anemometry (LDA). A detailed mapping of the transition from steady and axisymmetric flow...
Three-dimensional investigation of the two-phase flow structure in a bubbly pipe flow
International Nuclear Information System (INIS)
Hassan, Y.A.; Schmidl, W.D.; Ortiz-Villafuerte, J.
1997-01-01
Particle Image Velocimetry (PIV) is a non-intrusive measurement technique, which can be used to study the structure of various fluid flows. PIV is used to measure the time varying full field velocity data of a particle-seeded flow field within either a two-dimensional plane or three-dimensional volume. PIV is a very efficient measurement technique since it can obtain both qualitative and quantitative spatial information about the flow field being studied. This information can be further processed into information such as vorticity and pathlines. Other flow measurement techniques (Laser Doppler Velocimetry, Hot Wire Anemometry, etc...) only provide quantitative information at a single point. PIV can be used to study turbulence structures if a sufficient amount of data can be acquired and analyzed, and it can also be extended to study two-phase flows if both phases can be distinguished. In this study, the flow structure around a bubble rising in a pipe filled with water was studied in three-dimensions. The velocity of the rising bubble and the velocity field of the surrounding water was measured. Then the turbulence intensities and Reynolds stresses were calculated from the experimental data. (author)
Three Dimensional Flow and Pressure Patterns in a Hydrostatic Journal Bearing
Braun, M. Jack; Dzodzo, Milorad B.
1996-01-01
The flow in a hydrostatic journal bearing (HJB) is described by a mathematical model that uses the three dimensional non-orthogonal form of the Navier-Stokes equations. Using the u, v, w, and p, as primary variables, a conservative formulation, finite volume multi-block method is applied through a collocated, body fitted grid. The HJB has four shallow pockets with a depth/length ratio of 0.067. This paper represents a natural extension to the two and three dimensional studies undertaken prior to this project.
On a modified form of navier-stokes equations for three-dimensional flows.
Venetis, J
2015-01-01
A rephrased form of Navier-Stokes equations is performed for incompressible, three-dimensional, unsteady flows according to Eulerian formalism for the fluid motion. In particular, we propose a geometrical method for the elimination of the nonlinear terms of these fundamental equations, which are expressed in true vector form, and finally arrive at an equivalent system of three semilinear first order PDEs, which hold for a three-dimensional rectangular Cartesian coordinate system. Next, we present the related variational formulation of these modified equations as well as a general type of weak solutions which mainly concern Sobolev spaces.
THREE-DIMENSIONAL SIMULATION OF FLOW AT AN OPEN-CHANNEL CONFLUENCE WITH TURBULENCE MODELS
Dinh Thanh, Mung; Kimura, Ichiro; Shimizu, Yasuyuki
Open-channel confluence flows are common in natural river systems as well as in environmental and hydraulic engineering, such as in river engineering. Often, these flows are three-dimensional and complex,while numerical studies fully describing confluence flow are still few. This paper presents the results of investigation of confluence flow using a three-dimensional numerical model with the linear and nonlinear k-ε models. To treat the dynamic boundary condition at the free surface, non-hydrostatic pressure is included in the present model. The model is validated using the experimental data available. Adequacy of the present model with two turbulence models above is indicated based on the result analysis. The nonlinear model is indicated as the more advantageous one than the linear one.
Subramanian, S. V.; Bozzola, R.; Povinelli, L. A.
1986-01-01
The performance of a three dimensional computer code developed for predicting the flowfield in stationary and rotating turbomachinery blade rows is described in this study. The four stage Runge-Kutta numerical integration scheme is used for solving the governing flow equations and yields solution to the full, three dimensional, unsteady Euler equations in cylindrical coordinates. This method is fully explicit and uses the finite volume, time marching procedure. In order to demonstrate the accuracy and efficiency of the code, steady solutions were obtained for several cascade geometries under widely varying flow conditions. Computed flowfield results are presented for a fully subsonic turbine stator and a low aspect ratio, transonic compressor rotor blade under maximum flow and peak efficiency design conditions. Comparisons with Laser Anemometer measurements and other numerical predictions are also provided to illustrate that the present method predicts important flow features with good accuracy and can be used for cost effective aerodynamic design studies.
K. V. Pagalthivarthi; R. J. Visintainer
2013-01-01
Multi-size particulate dense slurry flow through three-dimensional rectangular channel is modeled using penalty finite elements with 8-noded hexahedral elements. The methodology previously developed for two-dimensional channel is extended. The computed eddy viscosity of the pure carrier flow is modified to account for the presence of solid particles. Predictions from Spalart-Almaras and k-ε turbulence models are compared to show consistency of trends in results. Results are also found to comp...
Modeling flow and shear stress fields over unsteady three dimensional dunes
Hardy, Richard; Parsons, Dan; Ashworth, Phil; Reesink, Arjan; Best, Jim
2014-05-01
The flow field over dunes has been extensively measured in laboratory conditions and there is general understanding on the nature of the flow over dunes formed under equilibrium flow conditions. This has allowed an understanding of bed shear stress to be derived and the development of morpho-dynamic models. However, fluvial systems typically experience unsteady flow and therefore the sediment-water interface is constantly responding and reorganizing to these unsteady flows and stresses, over a range of both spatial and temporal scales. This is primarily through the adjustment of bed forms (including ripples, dunes and bar forms) which then subsequently alter the flow field. This paper investigates, through the application of a numerical model, the influence of these roughness elements on the overall flow and bed shear stress. A series of physical experiments were undertaken in a flume, 16m long and 2m wide, where a fine sand (D50 of 239µm) was water worked under a range of unsteady hydraulic conditions to generate a series of quasi-equilibrium three dimensional bed forms. During the experiments flow was measured with acoustic Doppler velocimeters, (aDv's). On four occasions the flume was drained and the bed topography measured with terrestrial LiDAR to create digital elevation models. This data provide the necessary boundary conditions and validation data for a numerical three dimensional flow model. The prediction of flow over the four static beds demonstrates the spatial distribution of shear stress and the potential sediment transport paths between the dune crests. These appear to be associated with coherent flow structures formed by localized shear flow. These flow predictions are currently being used to develop a fully three dimensional morphodynamic model to further understand dune dynamics under unsteady flow conditions.
Three-dimensional power Doppler sonography: imaging and quantifying blood flow and vascularization.
Pairleitner, H; Steiner, H; Hasenoehrl, G; Staudach, A
1999-08-01
To assess the feasibility of imaging low-velocity blood flow in adnexal masses by transvaginal three-dimensional power Doppler sonography, to analyze three-dimensional power Doppler sonography data sets with a new computer-assisted method and to test the reproducibility of the technique. A commercially available 5-MHz Combison 530 ultrasound system was used to perform three-dimensional power Doppler sonography transvaginally. A cube (= volume of interest) was defined enclosing the vessels of the cyst and the Cartesian characteristics were stored on a hard disk. This cube was analyzed using specially designed software. Five indices representing vascularization (the vascularization index (VI) or blood flow (the flow index (FI)) or both (the vascularization-flow index (VFI)) were calculated. The intraobserver repeatability of cube definition and scan repetition was assessed using Hartley's test for homogeneous variances. Interobserver agreement was assessed by the Pearson correlation coefficient. Imaging of vessels with low-velocity blood flow by three-dimensional power Doppler sonography and cube definition was possible in all adnexal massed studied. In some cases even induced non-vascular flow related to endometriosis was detected. The calculated F value with intraobserver repeated Cartesian file-saving ranged from 0 to 18.8, with intraobserver scan repetition from 4.74 to 24.8 for VI, FI 1, FI 2 and VFI 1; for VFI 2 the calculated F value was 64. The interobserver correlation coefficient ranged between 0.83 and 0.92 for VI, FI 1, FI 2 and VFI 1; for VFI 2 the correlation coefficient was less than 0.75. Vessels with low-velocity blood flow can be imaged using three-dimensional power Doppler sonography. Induced non-vascular flow was detected in endometriotic cyst fluid. Three-dimensional power Doppler sonography combined with the cube method gave reproducible information for all indices except VFI 2. These indices might prove to be a new predictor in all fields of
Three Dimensional Flow and Pressure Patterns in a Single Pocket of a Hydrostatic Journal Bearing
Braun, M. Jack; Dzodzo, Milorad B.
1996-01-01
The flow in a hydrostatic pocket is described by a mathematical model that uses the three dimensional Navier-Stokes equations written in terms of the primary variables, u, v, w, and p. Using a conservative formulation, a finite volume multi-block method is applied through a collocated, body fitted grid. The flow is simulated in a shallow pocket with a depth/length ratio of 0.02. The flow structures obtained and described by the authors in their previous two dimensional models are made visible in their three dimensional aspect for the Couette flow. It has been found that the flow regimes formed central and secondary vortical cells with three dimensional corkscrew-like structures that lead the fluid on an outward bound path in the axial direction of the pocket. The position of the central vortical cell center is at the exit region of the capillary restrictor feedline. It has also been determined that a fluid turn around zone occupies all the upstream space between the floor of the pocket and the runner, thus preventing any flow exit through the upstream port. The corresponding pressure distribution under the shaft presented as well. It was clearly established that for the Couette dominated case the pressure varies significantly in the pocket in the circumferential direction, while its variation is less pronounced axially.
A finite area scheme for shallow granular flows on three-dimensional surfaces
Rauter, Matthias
2017-04-01
Shallow granular flow models have become a popular tool for the estimation of natural hazards, such as landslides, debris flows and avalanches. The shallowness of the flow allows to reduce the three-dimensional governing equations to a quasi two-dimensional system. Three-dimensional flow fields are replaced by their depth-integrated two-dimensional counterparts, which yields a robust and fast method [1]. A solution for a simple shallow granular flow model, based on the so-called finite area method [3] is presented. The finite area method is an adaption of the finite volume method [4] to two-dimensional curved surfaces in three-dimensional space. This method handles the three dimensional basal topography in a simple way, making the model suitable for arbitrary (but mildly curved) topography, such as natural terrain. Furthermore, the implementation into the open source software OpenFOAM [4] is shown. OpenFOAM is a popular computational fluid dynamics application, designed so that the top-level code mimics the mathematical governing equations. This makes the code easy to read and extendable to more sophisticated models. Finally, some hints on how to get started with the code and how to extend the basic model will be given. I gratefully acknowledge the financial support by the OEAW project "beyond dense flow avalanches". Savage, S. B. & Hutter, K. 1989 The motion of a finite mass of granular material down a rough incline. Journal of Fluid Mechanics 199, 177-215. Ferziger, J. & Peric, M. 2002 Computational methods for fluid dynamics, 3rd edn. Springer. Tukovic, Z. & Jasak, H. 2012 A moving mesh finite volume interface tracking method for surface tension dominated interfacial fluid flow. Computers & fluids 55, 70-84. Weller, H. G., Tabor, G., Jasak, H. & Fureby, C. 1998 A tensorial approach to computational continuum mechanics using object-oriented techniques. Computers in physics 12(6), 620-631.
Numerical simulation of viscous transonic airfoil flows
Coakley, Thomas J.
1987-01-01
Numerical simulations of transonic airfoil flows using the Reynolds-averaged Navier-Stokes equations and various turbulence models are presented and compared with experimental data. Three different airfoils were investigated under varying flow conditions ranging from subcritical unseparated flows to supercritical separated flows. The turbulence models investigated consisted of three zero-equation models and one two-equation model. For unseparated flows involving weak viscous-inviscid interactions, the four models were comparable in their agreement with experiment. For separated flows involving strong viscous-inviscid interactions, the nonequilibrium zero-equation model of Johnson and King gave the best overall agreement with experiment.
Energy Technology Data Exchange (ETDEWEB)
Shehzad, S.A., E-mail: ali_qau70@yahoo.com [Department of Mathematics, Comsats Institute of Information Technology, Sahiwal 57000 (Pakistan); Abdullah, Z. [Department of Mathematics, Comsats Institute of Information Technology, Sahiwal 57000 (Pakistan); Alsaedi, A. [Nonlinear Analysis and Applied Mathematics (NAAM) Research Group, Faculty of Science, King Abdulaziz University, P. O. Box 80257, Jeddah 21589 (Saudi Arabia); Abbasi, F.M. [Department of Mathematics, Comsats Institute of Information Technology, Islamabad 44000 (Pakistan); Hayat, T. [Nonlinear Analysis and Applied Mathematics (NAAM) Research Group, Faculty of Science, King Abdulaziz University, P. O. Box 80257, Jeddah 21589 (Saudi Arabia); Department of Mathematics, Quaid-I-Azam University 45320, Islamabad 44000 (Pakistan)
2016-01-01
This research work addresses the three-dimensional hydromagnetic flow of Jeffrey fluid with nanoparticles. Flow is generated by a bidirectional stretching surface. The effects of thermal radiation and internal heat generation are encountered in energy expressions. More realistic convective boundary conditions at the surface are employed instead of constant surface temperature and mass species conditions. Boundary layer assumptions lead to the governing non-linear mathematical model. Resulting equations through momentum, energy and mass species are made dimensionless using suitable variables. The solution expressions of dimensionless velocities, temperature and nanoparticle concentration have been computed for the convergent series solutions. The impacts of interesting parameters on the dimensionless quantities are displayed and interpreted. The values of physical quantities are computed and analyzed. - Highlights: • Three-dimensional hydromagnetic flow of Jeffrey nanofluid is considered. • Brownian motion and thermophoresis effects are encountered. • Heat transfer analysis is performed with thermal radiation. • Results are plotted and visualized.
Impact of magnetic field in three-dimensional flow of Sisko nanofluid with convective condition
Energy Technology Data Exchange (ETDEWEB)
Hayat, T. [Department of Mathematics, Quaid-I-Azam University, Islamabad 44000 (Pakistan); Nonlinear Analysis and Applied Mathematics (NAAM) Research Group, Department of Mathematics, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589 (Saudi Arabia); Muhammad, Taseer, E-mail: taseer_qau@yahoo.com [Department of Mathematics, Quaid-I-Azam University, Islamabad 44000 (Pakistan); Ahmad, B. [Nonlinear Analysis and Applied Mathematics (NAAM) Research Group, Department of Mathematics, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589 (Saudi Arabia); Shehzad, S.A. [Department of Mathematics, Comsats Institute of Information Technology, Sahiwal 57000 (Pakistan)
2016-09-01
This communication addresses the magnetohydrodynamic (MHD) three dimensional flow of Sisko nanofluid bounded by a surface stretched bidirectionally. Nanofluid model includes the Brownian motion and thermophoresis. Heat transfer through convective condition is discussed. Developed condition with the zero nanoparticles mass flux at the surface is implemented. The governing problems subject to boundary layer approximations are computed for the convergent series solutions. Effects of interesting flow parameters on the temperature and nanoparticles concentration distributions are studied and discussed. Skin friction coefficients and the local Nusselt number are computed and analyzed. - Highlights: • Three-dimensional flow of Sisko nanofluid is modeled. • Uniform applied magnetic field is adopted. • Brownian motion and thermophoresis effects are accounted. • Heat transfer convective condition is utilized. • Recently constructed condition with zero nanoparticles mass flux is implemented.
Three-dimensional hypersonic rarefied flow calculations using direct simulation Monte Carlo method
Celenligil, M. Cevdet; Moss, James N.
1993-01-01
A summary of three-dimensional simulations on the hypersonic rarefied flows in an effort to understand the highly nonequilibrium flows about space vehicles entering the Earth's atmosphere for a realistic estimation of the aerothermal loads is presented. Calculations are performed using the direct simulation Monte Carlo method with a five-species reacting gas model, which accounts for rotational and vibrational internal energies. Results are obtained for the external flows about various bodies in the transitional flow regime. For the cases considered, convective heating, flowfield structure and overall aerodynamic coefficients are presented and comparisons are made with the available experimental data. The agreement between the calculated and measured results are very good.
DEFF Research Database (Denmark)
Cutanda Henriquez, Vicente; Andersen, Peter Risby
2018-01-01
then be modeled with numerical methods that include losses. In recent years, versions of both the Finite Element Method (FEM) and the Boundary Element Method (BEM) including viscous and thermal losses have been developed. This paper deals with an improved formulation in three dimensions of the BEM with losses...... which avoids the calculation of tangential derivatives on the surface by finite differences used in a previous BEM implementation. Instead, the tangential derivatives are obtained from the element shape functions. The improved implementation is demonstrated using an oscillating sphere, where......Sound waves in fluids are subject to viscous and thermal losses, which are particularly relevant in the so-called viscous and thermal boundary layers at the boundaries, with thicknesses in the micrometer range at audible frequencies. Small devices such as acoustic transducers or hearing aids must...
Large Eddy Simulations of the Flow in a Three-Dimensional Ventilated Room
DEFF Research Database (Denmark)
Davidson, Lars; Nielsen, Peter V.
We have done Large Eddy Simulations (LES) of the flow in a three-dimensional ventilated room. A finite volume method is used with a collocated grid arrangement. The momentum equations are solved with an explicit method using central differencing for all terms. The pressure is obtained from a Pois...... a Poisson equation, which is solved with a conjugate gradient method. For the discretization in time we use the Adam-Bashfourth scheme, which is second-order accurate.......We have done Large Eddy Simulations (LES) of the flow in a three-dimensional ventilated room. A finite volume method is used with a collocated grid arrangement. The momentum equations are solved with an explicit method using central differencing for all terms. The pressure is obtained from...
Thermally induced rarefied gas flow in a three-dimensional enclosure with square cross-section
Zhu, Lianhua; Yang, Xiaofan; Guo, Zhaoli
2017-12-01
Rarefied gas flow in a three-dimensional enclosure induced by nonuniform temperature distribution is numerically investigated. The enclosure has a square channel-like geometry with alternatively heated closed ends and lateral walls with a linear temperature distribution. A recently proposed implicit discrete velocity method with a memory reduction technique is used to numerically simulate the problem based on the nonlinear Shakhov kinetic equation. The Knudsen number dependencies of the vortices pattern, slip velocity at the planar walls and edges, and heat transfer are investigated. The influences of the temperature ratio imposed at the ends of the enclosure and the geometric aspect ratio are also evaluated. The overall flow pattern shows similarities with those observed in two-dimensional configurations in literature. However, features due to the three-dimensionality are observed with vortices that are not identified in previous studies on similar two-dimensional enclosures at high Knudsen and small aspect ratios.
Measuring three-dimensional flow structures in the conductive airways using 3D-PTV
Janke, Thomas; Schwarze, Rüdiger; Bauer, Katrin
2017-10-01
Detailed information about flow patterns and mass transport in the conductive airways is of crucial interest to improve ventilation strategies as well as targeted drug delivery. Despite a vast number of flow studies in this field, there is still a dearth in experimental data of three-dimensional flow patterns, in particular for the validation of numerical results. Therefore, oscillating flow within a realistic model of the upper human conductive airways is studied here experimentally. The investigated range of Reynolds numbers is Re = 250-2000 and the Womersley number is varied between α = 1.9-5.1, whereby physiological flow at rest conditions is included. In employing the three-dimensional particle tracking velocimetry measurement technique, we can directly visualize airway specific flow structures as well as examine Lagrangian trajectory statistics, which has not been covered to date. The systematic variation of characteristic flow parameters in combination with the advanced visualization technique sheds new light on the mechanisms of evolving flow patterns. By determining Lagrangian properties such as pathline curvature and torsion, we find that both strongly depend on the Reynolds number. Moreover, the probability density function of the curvature reveals a unique shape for certain flow regions and resembles a turbulent like behavior at the small scales.
Three-Dimensional Mapping of Air Flow at an Urban Canyon Intersection
Carpentieri, Matteo; Robins, Alan G.; Baldi, Sandro
2009-11-01
In this experimental work both qualitative (flow visualisation) and quantitative (laser Doppler anemometry) methods were applied in a wind tunnel in order to describe the complex three-dimensional flow field in a real environment (a street canyon intersection). The main aim was an examination of the mean flow, turbulence and flow pathlines characterising a complex three-dimensional urban location. The experiments highlighted the complexity of the observed flows, particularly in the upwind region of the intersection. In this complex and realistic situation some details of the upwind flow, such as the presence of two tall towers, play an important role in defining the flow field within the intersection, particularly at roof level. This effect is likely to have a strong influence on the mass exchange mechanism between the canopy flow and the air aloft, and therefore the distribution of pollutants. This strong interaction between the flows inside and outside the urban canopy is currently neglected in most state-of-the-art local scale dispersion models.
Three dimensional PNS solutions of hypersonic internal flows with equilibrium chemistry
Liou, May-Fun
1989-01-01
An implicit procedure for solving parabolized Navier-Stokes equations under the assumption of a general equation of state for a gas in chemical equilibrium is given. A general and consistent approach for the evaluation of Jacobian matrices in the implicit operator avoids the use of unnecessary auxiliary quantities and approximations, and leads to a simple expression. Applications to two- and three-dimensional flow problems show efficiency in computer time and economy in storage.
Nadeem, S.; Abbas, Nadeem; Khan, A. U.
2018-03-01
The characteristics of three-dimensional stagnation point flow of Hybrid nanofluid past a circular cylinder are explored. The fluid flow is entertained in the presence/absence of thermal slip effects. The flow model is controlled through the partial differential equations. Since these equations are highly non-linear in character. So for the order reduction a suitable set of transformation is used. The reduced system is solved by using shooting method. The obtained results are offered through graphs and tables. It is noticed that the heat transfer rate is high in Hybrid nanofluid as compared to nanofluid. The present work is validated by developing comprising with existing literature.
Three-dimensional fluid flow phenomena in the blade end wall corner region
Hazarika, B. K.; Raj, R.; Boldman, D. R.
1986-01-01
Flow visualization, static and total pressure measurements, and mean velocity profile measurements with a single-sensor inclined hot wire probe, are used in a study of three-dimensional flow at a turbine blade end wall corner region for six critical axial stations along the blade chord. Three vortices are identified: (1) a horseshoe vortex near the leading edge; (2) a corner eddy between the horseshoe vortex and the corner; and (3) a vortex at the rear portion of the corner due to the corner eddy's secondary flow. Attention is given to the relative size and rate-of-spread of the vortices in the streamwise direction.
The influence of three dimensional dunes on river flows and fluxes
Hardy, R. J.; Parsons, D. R.; Ockelford, A.; Ashworth, P. J.; Reesink, A.; Best, J.
2015-12-01
Fluvial systems in large river basins experience temporal variations in flow discharge, which creates unsteady changes in the flow field and sediment fluxes. The sediment-water interface responds and organizes to these changes over a wide range of spatial and temporal scales, primarily through adjustment of a variety of bed roughness elements. These roughness elements are the key component of overall flow resistance and the magnitude of their form drag significantly influences river stage levels for given discharge and determines the state and functioning of river systems and sediment fluxes. Here we present three dimensional numerically predicted flow results to demonstrate the importance of complex morphology on flow and sediment fluxes. Model boundary conditions and validation data were taken from two sources. Initially, they were collected from a field campaign on a 1.5 by 0.3 km stretch of the Mississippi near Alton, Illinois. Secondly, a series of flume experiments were undertaken that applied unsteady hydraulic conditions to generate a series of quasi-equilibrium three dimensional bed forms, which were scaled on the data collected in the field. The numerical flow results show that superimposed bed forms can cause changes in the nature of the classical separated flow region in particularly the number of locations where vortices are shed and the point of flow reattachment, which may be important for sediment flux dynamics during bed form adjustment.
RICHTER, DAVID
2010-03-29
The results from a numerical investigation of inertial viscoelastic flow past a circular cylinder are presented which illustrate the significant effect that dilute concentrations of polymer additives have on complex flows. In particular, effects of polymer extensibility are studied as well as the role of viscoelasticity during three-dimensional cylinder wake transition. Simulations at two distinct Reynolds numbers (Re = 100 and Re = 300) revealed dramatic differences based on the choice of the polymer extensibility (L2 in the FENE-P model), as well as a stabilizing tendency of viscoelasticity. For the Re = 100 case, attention was focused on the effects of increasing polymer extensibility, which included a lengthening of the recirculation region immediately behind the cylinder and a sharp increase in average drag when compared to both the low extensibility and Newtonian cases. For Re = 300, a suppression of the three-dimensional Newtonian mode B instability was observed. This effect is more pronounced for higher polymer extensibilities where all three-dimensional structure is eliminated, and mechanisms for this stabilization are described in the context of roll-up instability inhibition in a viscoelastic shear layer. © 2010 Cambridge University Press.
Wu, Chung-Hua
1993-01-01
This report represents a general theory applicable to axial, radial, and mixed flow turbomachines operating at subsonic and supersonic speeds with a finite number of blades of finite thickness. References reflect the evolution of computational methods used, from the inception of the theory in the 50's to the high-speed computer era of the 90's. Two kinds of relative stream surfaces, S(sub 1) and S(sub 2), are introduced for the purpose of obtaining a three-dimensional flow solution through the combination of two-dimensional flow solutions. Nonorthogonal curvilinear coordinates are used for the governing equations. Methods of computing transonic flow along S(sub 1) and S(sub 2) stream surfaces are given for special cases as well as for fully three-dimensional transonic flows. Procedures pertaining to the direct solutions and inverse solutions are presented. Information on shock wave locations and shapes needed for computations are discussed. Experimental data from a Deutsche Forschungs- und Versuchsanstalt fur Luft- und Raumfahrt e.V. (DFVLR) rotor and from a Chinese Academy of Sciences (CAS) transonic compressor rotor are compared with the computed flow properties.
Measurement of flow in viscous fluids
Energy Technology Data Exchange (ETDEWEB)
Mills, Chris [NEL Technology for Life (Mexico)
2011-07-01
Taking accurate flow measurements of viscous fluids can prove to be a difficult task. The process faces a number of challenges which include pressure losses, varying velocity profiles, higher viscous friction, and the presence of solids or gas. In this presentation NEL, holder of UK's National Standards for flow measurement, shares a test that was conducted to identify the influencing factors of flow measurements for viscous fluids. The test, which was conducted at NEL's National Standards oil flow facility, utilizes three test meters. The first test meter used was a multi-path ultrasonic meter, the other two were twin-tube coriolis meters of different sizes. Readings were taken from each meter for kerosene and primol at varying degrees of viscosity. Adjustments in flowrate and temperature were also made and recorded throughout the test. From the tests, NEL was able to generate data regarding the factors impacting mass flowrate, density, and pressure.
Experimental investigation of three-dimensional flow instabilities in a rotating lid-driven cavity
DEFF Research Database (Denmark)
Sørensen, Jens Nørkær; Naumov, I.; Mikkelsen, Robert Flemming
2006-01-01
The flow between a rotating lid and a stationary cylinder is studied experimentally. The flow is governed by two parameters: The ratio of container height to disk radius, h, and the Reynolds number, Re, based on the disk angular velocity, cylinder radius and kinematic viscosity of the working...... stability analysis of Gelfgat et al. [J. Fluid. Mech. 438, (2001)]. In most cases the measured onset of three-dimensionality is in good agreement with the numerical results and disagreements can be explained by bifurcations not accounted for by the stability analysis....
Directory of Open Access Journals (Sweden)
K. V. Pagalthivarthi
2013-03-01
Full Text Available Multi-size particulate dense slurry flow through three-dimensional rectangular channel is modeled using penalty finite elements with 8-noded hexahedral elements. The methodology previously developed for two-dimensional channel is extended. The computed eddy viscosity of the pure carrier flow is modified to account for the presence of solid particles. Predictions from Spalart-Almaras and k-ε turbulence models are compared to show consistency of trends in results. Results are also found to compare well with experimental results from the literature.
Three-dimensional visualization of myocardial motion and blood flow with cine-MR images
International Nuclear Information System (INIS)
Oshiro, Osamu; Matani, Ayumu; Chihara, Kunihiro; Mikami, Taisei; Kitabatake, Akira.
1997-01-01
This paper describes a three-dimensional (3D) reconstruction and presentation method to visualize myocardial motion and blood flow in a heart using cine-MR (magnetic resonance) images. Firstly, the region of myocardium and blood were segmented with certain threshold gray values. Secondly, some slices were interpolated linearly to reconstruct a 3D static image. Finally, a 3D dynamic image was presented with displaying the 3D static images sequentially. The experimental results indicate that this method enables to visualize not only normal but also abnormal blood flow in cine-mode. (author)
PIV measurements in a microfluidic 3D-sheathing structure with three-dimensional flow behaviour
DEFF Research Database (Denmark)
Klank, Henning; Goranovic, Goran; Kutter, Jörg Peter
2002-01-01
. The structures are often of complex geometry and include strongly three-dimensional flow behaviour, which poses a challenge for the micro particle image velocimetry (micro-PIV) technique. The flow in a microfluidic 3D-sheathing structure has been measured throughout the volume using micro-PIV. In addition......, a stereoscopic principle was applied to obtain all three velocity components, showing the feasibility of obtaining full volume mapping (x, y, z, U, V, W) from micro-PIV measurements. The results are compared with computational fluid dynamics (CFD) simulations....
Wavelet-based regularization of the Galerkin truncated three-dimensional incompressible Euler flows.
Farge, Marie; Okamoto, Naoya; Schneider, Kai; Yoshimatsu, Katsunori
2017-12-01
We present numerical simulations of the three-dimensional Galerkin truncated incompressible Euler equations that we integrate in time while regularizing the solution by applying a wavelet-based denoising. For this, at each time step, the vorticity field is decomposed into wavelet coefficients, which are split into strong and weak coefficients, before reconstructing them in physical space to obtain the corresponding coherent and incoherent vorticities. Both components are multiscale and orthogonal to each other. Then, by using the Biot-Savart kernel, one obtains the coherent and incoherent velocities. Advancing the coherent flow in time, while filtering out the noiselike incoherent flow, models turbulent dissipation and corresponds to an adaptive regularization. To track the flow evolution in both space and scale, a safety zone is added in wavelet coefficient space to the coherent wavelet coefficients. It is shown that the coherent flow indeed exhibits an intermittent nonlinear dynamics and a k^{-5/3} energy spectrum, where k is the wave number, characteristic of three-dimensional homogeneous isotropic turbulence. Finally, we compare the dynamical and statistical properties of Euler flows subjected to four kinds of regularizations: dissipative (Navier-Stokes), hyperdissipative (iterated Laplacian), dispersive (Euler-Voigt), and wavelet-based regularizations.
Riley, Christopher J.
1992-01-01
An engineering method has been developed that couples an approximate three dimensional inviscid technique with the axisymmetric analog and a set of approximate convective heating equations. The displacement effect on the boundary layer on the outer inviscid flow is calculated and included as a boundary condition in the inviscid technique. This accounts for the viscous interaction present at lower Reynolds numbers. The method is applied to blunted axisymmetric and three dimensional elliptic cones at angle of attack for the laminar hypersonic flow of a perfect gas. The method is applied to turbulent and equilibrium-air conditions. The present technique predicts surface heating rates, pressures, and shock shapes that compare favorably with experimental (ground-test and flight) data and numerical solutions of the Navier-Stokes and viscous shock-layer equations. In addition, the inclusion of viscous interaction significantly improves results obtained at lower Reynolds numbers. The new technique represents a major improvement over current engineering aerothermal methods with only a modest increase in computational effort.
Three dimensional computations of the flow around a LM19 rotor
Energy Technology Data Exchange (ETDEWEB)
Hambraeus, T. [FFA, Bromma (Sweden)
1997-12-31
To achieve insight in the flow phenomenon occurring in wind power engineering modeling of the flow through the basic governing equations, Navier-Stokes and Euler, can be a great complement to experiments and other computational methods such as the BEM (Blade Element Momentum). Navier-Stokes methods is regularly used in prediction of air-foil flows but then mostly under attached flow conditions. One of the main differences between air-foil computations for aircraft industry and computations for wind turbine applications is that the former is not very interested in separated flow while for the latter case this is part of the operating conditions. It has been noted that separated flow poses problems since the most popular turbulence models such as Baldwin-Lomax and the {kappa}-{epsilon} model seems to over estimate the amount of turbulent viscosity produced and thus suppressing the separation. The work with finding better turbulence models is presently an area with large amount of research offering improved models. However, in the present report only the two mentioned turbulence models have been used. The present report shows computational results obtained with the Navier-Stokes solver EU-RANUS. First the results from a two-dimensional verification cases are shown to verify that the solver produces results comparable with other solvers. The flow computed is attached flow and slightly separated flow over the so called Profile-A. Secondly three dimensional computations of the flow over a full three dimensional rotor at attached and stalled conditions is shown. The computed results are compared with measured power data from field experiments. (EG)
Three-Dimensional Flow Separation Induced by a Model Vocal Fold Polyp
Stewart, Kelley C.; Erath, Byron D.; Plesniak, Michael W.
2012-11-01
The fluid-structure energy exchange process for normal speech has been studied extensively, but it is not well understood for pathological conditions. Polyps and nodules, which are geometric abnormalities that form on the medial surface of the vocal folds, can disrupt vocal fold dynamics and thus can have devastating consequences on a patient's ability to communicate. A recent in-vitro investigation of a model polyp in a driven vocal fold apparatus demonstrated that such a geometric abnormality considerably disrupts the glottal jet behavior and that this flow field adjustment was a likely reason for the severe degradation of the vocal quality in patients. Understanding of the formation and propagation of vortical structures from a geometric protuberance, and their subsequent impact on the aerodynamic loadings that drive vocal fold dynamic, is a critical component in advancing the treatment of this pathological condition. The present investigation concerns the three-dimensional flow separation induced by a wall-mounted prolate hemispheroid with a 2:1 aspect ratio in cross flow, i.e. a model vocal fold polyp. Unsteady three-dimensional flow separation and its impact of the wall pressure loading are examined using skin friction line visualization and wall pressure measurements. Supported by the National Science Foundation, Grant No. CBET-1236351 and GW Center for Biomimetics and Bioinspired Engineering (COBRE).
International Nuclear Information System (INIS)
Taggart, K.A.; Liles, D.R.
1977-08-01
The development of the TRAC computer code for analysis of LOCAs in light-water reactors involves the use of a three-dimensional (r-theta-z), two-fluid hydrodynamics model to describe the two-phase flow of steam and water through the reactor vessel. One of the major problems involved in interpreting results from this code is the presentation of three-dimensional flow patterns. The purpose of the report is to present a partial solution to this data display problem. A first version of a code which produces three-dimensional movies of flow in the reactor vessel has been written and debugged. This code (POST) is used as a postprocessor in conjunction with a stand alone three-dimensional two-phase hydrodynamics code (CYLTF) which is a test bed for the three-dimensional algorithms to be used in TRAC
Three-dimensional rotating flow of carbon nanotubes with Darcy-Forchheimer porous medium.
Directory of Open Access Journals (Sweden)
Tasawar Hayat
Full Text Available Here we are concerned with the Darcy-Forchheimer three-dimensional flow of carbon nanotubes in a rotating frame. Flow is generated by stretching of the surface. Xue model is adopted for nanofluid transport mechanism. Results for single wall carbon nanotubes (SWCNTs and multi wall carbon nanotubes are achieved and compared. Flow saturating porous space obeys Darcy-Forchheimer expression. Boundary layer approximations are invoked to simplify governing partial differential system. Optimal homotopy analysis method (OHAM is utilized for solutions of governing model. The optimal values of auxiliary parameters are computed. Plots have been displayed in order to analyze how the velocities and temperature fields get affected by various flow parameters. Skin-friction coefficients and local Nusselt number are presented through numerical data for both SWCNTs and MWCNTs. Moreover the skin-friction coefficients and local Nusselt number are enhanced for larger values of nanoparticles volume fraction.
Three-dimensional rotating flow of carbon nanotubes with Darcy-Forchheimer porous medium.
Hayat, Tasawar; Haider, Farwa; Muhammad, Taseer; Alsaedi, Ahmed
2017-01-01
Here we are concerned with the Darcy-Forchheimer three-dimensional flow of carbon nanotubes in a rotating frame. Flow is generated by stretching of the surface. Xue model is adopted for nanofluid transport mechanism. Results for single wall carbon nanotubes (SWCNTs) and multi wall carbon nanotubes are achieved and compared. Flow saturating porous space obeys Darcy-Forchheimer expression. Boundary layer approximations are invoked to simplify governing partial differential system. Optimal homotopy analysis method (OHAM) is utilized for solutions of governing model. The optimal values of auxiliary parameters are computed. Plots have been displayed in order to analyze how the velocities and temperature fields get affected by various flow parameters. Skin-friction coefficients and local Nusselt number are presented through numerical data for both SWCNTs and MWCNTs. Moreover the skin-friction coefficients and local Nusselt number are enhanced for larger values of nanoparticles volume fraction.
Emergence of three-dimensional flow structures in shock boundary layer interactions
Gs, Sidharth; Dwivedi, Anubhav; Nichols, Joseph; Jovanovic, Mihailo; Candler, Graham
2017-11-01
Experiments and computations point to the emergence of three-dimensional (3D) flow structures in laminar shock boundary layer interactions in various configurations. We examine a Mach 5 flow over a double compression ramp and reveal the presence of a bifurcation from a steady 2D to a steady 3D flow state. This is done by varying the relative angle of the two ramps which increases the interaction strength. We employ global linear stability analysis and direct numerical simulation to characterize this bifurcation and demonstrate that global instability induces 3D flow structures. We use the direct and adjoint linear equations to further investigate the origin of this instability and examine the influence of uncertainty (including the effect of geometric irregularities in the ramp and free-stream disturbances in wind tunnel) on this bifurcation. This work was supported by Office of Naval Research through Grant Number N00014-15-1-2522.
An implicit three-dimensional Navier-Stokes solver for compressible flow
International Nuclear Information System (INIS)
Yoon, Seokkwan; Kwak, Dochan.
1991-01-01
A three-dimensional numerical method based on the lower-upper symmetric-Gauss-Seidel implicit scheme in conjunction with the flux-limited dissipation model is developed for solving the compressible Navier-Stokes equations. A new computer code which is based on this method requires only 9 microsec per grid-point per iteration on a single processor of a Cray YMP computer and executes at the sustained rate of 170 MFLOPS. A reduction of 4 orders of magnitude in the residual for a high Reynolds number flow using 230 K grid points is obtained in 24 minutes. The computational results compare well with available experimental data. 39 refs
Calculation of three-dimensional fluid flow with multiple free surfaces
International Nuclear Information System (INIS)
Vander Vorst, M.J.; Chan, R.K.C.
1978-01-01
This paper presents a method for computing incompressible fluid flows with multiple free surfaces which are not restricted in their orientation. The method is presented in the context of the three-dimensional flow in a Mark I reactor pressure suppression system immediately following a postulated loss of coolant accident. The assumption of potential flow is made. The numerical method is a mixed Eulerian-Lagrangian formulation with the interior treated as Eulerian and the free surfaces as Lagrangian. The accuracy of solution hinges on the careful treatment of two important aspects. First, the Laplace equation for the potential is solved at interior points of the Eulerian finite difference mesh using a three-dimensional ''irregular star'' so that boundary conditions can be imposed at the exact position of the free surface. Second, the Lagrangian free surfaces are composed of triangular elements, upon each vertex of which is applied the fully nonlinear Bernoulli equation. One result of these calculations is the transient load on the suppression vessel during the vent clearing and bubble formation events of a loss of coolant accident
Three-dimensional flow structure measurements behind a queue of studied model vehicles
International Nuclear Information System (INIS)
Huang, J.F.; Chan, T.L.; Zhou, Y.
2009-01-01
The three-dimensional flow structures of a queue of studied model vehicles (i.e., one-, two- and three-vehicle cases) were investigated comprehensively in a closed-circuit wind tunnel using particle image velocimetry (PIV) for the typical urban vehicle speeds (i.e., 10, 30 and 50 km/h). In this three-dimensional vehicle wake, a pair of longitudinal vortices is characterized by counter-rotating and moving downstream at relatively low velocity than their surrounding flow. The flow structures of multiple studied model vehicles are dominated by the wake generated from the last studied model vehicle but the preceding studied model vehicle(s) also has/have some minor effects. Cross-sectional turbulence distribution is non-uniform in the far-wake region for all studied cases. The lowest turbulence occurs at the center part of the vehicle wake while high turbulence occurs at its two sides. As such, it may lead to considerable underestimation in turbulence magnitude if the measurement is only taken along the centerline of the vehicle wake.
DEFF Research Database (Denmark)
Shapiro, Alexander A.
2018-01-01
A new three-dimensional hydrodynamic model for unsteady two-phase flows in a porous medium, accounting for the motion of the interface between the flowing liquids, is developed. In a minimum number of interpretable geometrical assumptions, a complete system of macroscale flow equations is derived......, their expansion or contraction is also described, while rotation has been proven negligible. A detailed comparison with the previous studies for the two-phase flows accounting for propagation of the interface on micro- and macroscale has been carried out. A numerical algorithm has been developed allowing...... by averaging the microscale equations for viscous flow. The macroscale flow velocities of the phases may be non-parallel, while the interface between them is, on average, inclined to the directions of the phase velocities, as well as to the direction of the saturation gradient. The last gradient plays...
Stabilisation of a three-dimensional boundary layer by base-flow manipulation using plasma actuators
International Nuclear Information System (INIS)
Dörr, P C; Kloker, M J
2015-01-01
The applicability of dielectric barrier discharge plasma actuators for controlling the crossflow-vortex-induced laminar breakdown in a three-dimensional swept-wing-type boundary-layer flow is investigated using direct numerical simulation. Similar to the classical application of suction at the wall the aim is to modify the quasi two-dimensional base flow and to weaken primary crossflow (CF) instability, mainly due to a reduction of the basic CF. Not only localised volumetric forcing by plasma actuators but also CF counter-blowing and spots with a moving wall are investigated to identify effective fundamental mechanisms. It is found that counter blowing always results in partial blockage of the flow and eventually increased CF velocity, whereas moving-wall spots can slightly reduce the CF and the amplitude of crossflow vortices. Using discrete volumetric forcing a significant attenuation even of finite-amplitude crossflow vortices and thus a distinct transition delay is achieved. (paper)
Energy Technology Data Exchange (ETDEWEB)
Rauf, A., E-mail: raufamar@ciitsahiwal.edu.pk [Department of Mathematics, Comsats Institute of Information Technology, Sahiwal 57000 (Pakistan); Siddiq, M.K. [Centre for Advanced Studies in Pure and Applied Mathematics, Department of Mathematics, Bahauddin Zakariya University, Multan 63000 (Pakistan); Abbasi, F.M. [Department of Mathematics, Comsats Institute of Information Technology, Islamabad 44000 (Pakistan); Meraj, M.A. [Department of Mathematics, Comsats Institute of Information Technology, Sahiwal 57000 (Pakistan); Ashraf, M. [Centre for Advanced Studies in Pure and Applied Mathematics, Department of Mathematics, Bahauddin Zakariya University, Multan 63000 (Pakistan); Shehzad, S.A. [Department of Mathematics, Comsats Institute of Information Technology, Sahiwal 57000 (Pakistan)
2016-10-15
The present work deals with the steady laminar three-dimensional mixed convective magnetohydrodynamic (MHD) boundary layer flow of Casson nanofluid over a bidirectional stretching surface. A uniform magnetic field is applied normal to the flow direction. Similarity variables are implemented to convert the non-linear partial differential equations into ordinary ones. Convective boundary conditions are utilized at surface of the sheet. A numerical technique of Runge–Kutta–Fehlberg (RFK45) is used to obtain the results of velocity, temperature and concentration fields. The physical dimensionless parameters are discussed through tables and graphs. - Highlights: • Mixed convective boundary layer flow of Casson nanofluid is taken into account. • Impact of magnetic field is examined. • Convective heat and mass conditions are imposed. • Numerical solutions are presented and discussed.
Mao, Xiaole; Nawaz, Ahmad Ahsan; Lin, Sz-Chin Steven; Lapsley, Michael Ian; Zhao, Yanhui; McCoy, J Philip; El-Deiry, Wafik S; Huang, Tony Jun
2012-06-01
In this work, we demonstrate an integrated, single-layer, miniature flow cytometry device that is capable of multi-parametric particle analysis. The device integrates both particle focusing and detection components on-chip, including a "microfluidic drifting" based three-dimensional (3D) hydrodynamic focusing component and a series of optical fibers integrated into the microfluidic architecture to facilitate on-chip detection. With this design, multiple optical signals (i.e., forward scatter, side scatter, and fluorescence) from individual particles can be simultaneously detected. Experimental results indicate that the performance of our flow cytometry chip is comparable to its bulky, expensive desktop counterpart. The integration of on-chip 3D particle focusing with on-chip multi-parametric optical detection in a single-layer, mass-producible microfluidic device presents a major step towards low-cost flow cytometry chips for point-of-care clinical diagnostics.
PIV measurements in a microfluidic 3D-sheathing structure with three-dimensional flow behaviour
DEFF Research Database (Denmark)
Klank, Henning; Goranovic, Goran; Kutter, Jörg Peter
2002-01-01
. The structures are often of complex geometry and include strongly three-dimensional flow behaviour, which poses a challenge for the micro particle image velocimetry (micro-PIV) technique. The flow in a microfluidic 3D-sheathing structure has been measured throughout the volume using micro-PIV. In addition......The design and production time for complex microfluidic systems is considerable, often up to several months. It is therefore important to be able to understand and predict the flow phenomena prior to design and fabrication of the microdevice in order to save costly fabrication resources......, a stereoscopic principle was applied to obtain all three velocity components, showing the feasibility of obtaining full volume mapping (x, y, z, U, V, W) from micro-PIV measurements. The results are compared with computational fluid dynamics (CFD) simulations....
Numerical method for three dimensional steady-state two-phase flow calculations
International Nuclear Information System (INIS)
Raymond, P.; Toumi, I.
1992-01-01
This paper presents the numerical scheme which was developed for the FLICA-4 computer code to calculate three dimensional steady state two phase flows. This computer code is devoted to steady state and transient thermal hydraulics analysis of nuclear reactor cores 1,3 . The first section briefly describes the FLICA-4 flow modelling. Then in order to introduce the numerical method for steady state computations, some details are given about the implicit numerical scheme based upon an approximate Riemann solver which was developed for calculation of flow transients. The third section deals with the numerical method for steady state computations, which is derived from this previous general scheme and its optimization. We give some numerical results for steady state calculations and comparisons on required CPU time and memory for various meshing and linear system solvers
DEFF Research Database (Denmark)
Sørensen, Jens Nørkær; Gelfgat, A. Yu; Naumov, I. V.
2009-01-01
for each mode. The onset of three-dimensional flow behavior is measured by combining the high spatial resolution of particle image velocimetry and the temporal accuracy of laser Doppler anemometry. The results are compared to the numerical stability analysis. The measured onset of three dimensionality......The three-dimensional axisymmetry-breaking instability of axisymmetric flow between a rotating lid and a stationary cylinder is analyzed both numerically and experimentally for the case of tall cylinders with the height/radius aspect ratio between 3.3 and 5.5. A complete stability diagram...... for the primary three-dimensional instability is obtained experimentally and computed numerically. The instability sets in due to different three-dimensional disturbance modes that are characterized by different azimuthal wavenumbers. The critical Reynolds numbers and associated frequencies are identified...
Directory of Open Access Journals (Sweden)
M. Nawaz
Full Text Available In this article, we developed a computer code of Galerikan Finite Element method (GFEM for three dimensional flow equations of nano-plasma fluid (blood in the presence of uniform applied magnetic field when Hall and ion slip current are significant. Lorentz force is calculated through generalized Ohmâs law with Maxwell equations. A series of numerical simulations are carried out to search Î·max and algebraic equations are solved by Gauss-Seidel method with simulation tolerance 10-8. Simulated results for special case have an excellent agreement with the already published results. Velocity components and temperature of the nano-plasma (blood are influenced significantly by the inclusion of nano-particles of Copper (Cu and Silver (Ag. Heat enhancement is observed when copper and silver nonmagnetic nanoparticles are used instead of simple base fluid (conventional fluid. Radiative nature of nano-plasma in the presence of magnetic field causes a decrease in the temperature due to the transfer of heat by the electromagnetic waves. In contrast to this, due to heat dissipated by Joule heating and viscous dissipation phenomena, temperature of nano-plasmaincreases as thermal radiation parameter is increased. Thermal boundary layer thickness can be controlled by using radiative fluid instead of non-radiative fluid. Momentum boundary layer thickness can be reduced by increasing the intensity of the applied magnetic field. Temperature of plasma in the presence magnetic field is higher than the plasma in the absence of magnetic field. Keywords: Nanofluid, Grid independent study, Convergence, Error analysis, Skin friction, Joule heating, Viscous dissipation, Hall and ion currents
Lardeau, Sylvain; Ferrari, Simone; Rossi, Lionel
2008-12-01
Three-dimensional (3D) direct numerical simulations of a flow driven by multiscale electromagnetic forcing are performed in order to reproduce with maximum accuracy the quasi-two-dimensional (2D) flow generated by the same multiscale forcing in the laboratory. The method presented is based on a 3D description of the flow and the electromagnetic forcing. Very good agreements between our simulations and the experiments are found both on velocity and acceleration field, this last comparison being, to our knowledge, done for the first time. Such agreement requires that both experiments and simulations are carefully performed and, more importantly, that the underlying simplification to model the experiments and the multiscale electromagnetic forcing do not introduce significant errors. The results presented in this paper differ significantly from previous 2D direct numerical simulation in which a classical linear Rayleigh friction modeling term was used to mimic the effect of the wall-normal friction. Indeed, purely 2D simulations are found to underestimate the Reynolds number and, due to the dominance of nonhomogeneous bottom friction, lead to the wrong physical mechanism. For the range of conditions presented in this paper, the Reynolds number, defined by the ratio between acceleration and viscous terms, remains the order of unity, and the Hartmann number, defined by the ratio between electromagnetic force terms and viscous terms, is about 2. The main conclusion is that 3D simulations are required to model the (3D) electromagnetic forces and the wall-normal shear. Indeed, even if the flow is quasi-2D in terms of energy, a full 3D approach is required to simulate these shallow layer flows driven by multiscale electromagnetic forcing. In the range of forcing intensity investigated in this paper, these multiscale flows remain quasi-2D, with negligible energy in the wall-normal velocity component. It is also shown that the driving terms are the electromagnetic forcing and
International Nuclear Information System (INIS)
Hua, T.Q.; Walker, J.S.; Picologlou, B.F.; Reed, C.B.
1988-07-01
Magnetohydrodynamic flows of liquid metals in rectangular ducts with thin conducting walls in the presence of strong nonuniform transverse magnetic fields are examined. The interaction parameter and Hartmann number are assumed to be large, whereas the magnetic Reynolds number is assumed to be small. Under these assumptions, viscous and inertial effects are confined in very thin boundary layers adjacent to the walls. A significant fraction of the fluid flow is concentrated in the boundary layers adjacent to the side walls which are parallel to the magnetic field. This paper describes the analysis and numerical methods for obtaining 3-D solutions for flow parameters outside these layers, without solving explicitly for the layers themselves. Numerical solutions are presented for cases which are relevant to the flows of liquid metals in fusion reactor blankets. Experimental results obtained from the ALEX experiments at Argonne National Laboratory are used to validate the numerical code. In general, the agreement is excellent. 5 refs., 14 figs
International Nuclear Information System (INIS)
Rao, S.I.; Dimiduk, D.M.; Parthasarathy, T.A.; Uchic, M.D.; Tang, M.; Woodward, C.
2008-01-01
Recent experimental studies have revealed that micrometer-scale face-centered cubic (fcc) crystals show strong strengthening effects, even at high initial dislocation densities. We use large-scale three-dimensional discrete dislocation simulations (DDS) to explicitly model the deformation behavior of fcc Ni microcrystals in the size range of 0.5-20 μm. This study shows that two size-sensitive athermal hardening processes, beyond forest hardening, are sufficient to develop the dimensional scaling of the flow stress, stochastic stress variation, flow intermittency and high initial strain-hardening rates, similar to experimental observations for various materials. One mechanism, source-truncation hardening, is especially potent in micrometer-scale volumes. A second mechanism, termed exhaustion hardening, results from a breakdown of the mean-field conditions for forest hardening in small volumes, thus biasing the statistics of ordinary dislocation processes
Unsteady three-dimensional flow of Casson–Carreau fluids past a stretching surface
Directory of Open Access Journals (Sweden)
C.S.K. Raju
2016-06-01
Full Text Available In this study, we investigated the effects of nonlinear thermal radiation and non-uniform heat source/sink in unsteady three-dimensional flow of Carreau and Casson fluids past a stretching surface in the presence of homogeneous–heterogeneous reactions. The transformed governing equations are solved numerically using Runge–Kutta based shooting technique. We obtained good accuracy of the present results by comparing with the already published literature. The influence of dimensionless governing parameters on velocity, temperature and concentration profiles along with the friction factors, local Nusselt and Sherwood numbers is discussed and presented graphically. We presented dual solutions for flow, heat and mass transfer in Carreau and Casson fluids. It is found that the heat and mass transfer rate in Casson fluid is significantly high while compared with the Carreau fluid.
Hayat, Tasawar; Ayub, Tayyaba; Muhammad, Taseer; Alsaedi, Ahmed
Here three dimensional (3D) flow of second grade fluid has been studied in the presence of Cattaneo-Christov double diffusion and heterogeneous-homogeneous reactions. Flow is bounded by a bidirectional linear stretchable surface. Generalized versions of Fourier's and Fick's law through Cattaneo-Christov double diffusion are employed. Equal diffusion coefficients are considered for both autocatalyst and reactants. The conversion of partial differential system to nonlinear ordinary differential system has been done by employing appropriate transformations. The obtained nonlinear systems have been solved through the optimal homotopy analysis method (OHAM). Graphs have been displayed in order to examine how the velocities, temperature and concentration fields are affected by various pertinent parameters. Moreover the skin friction coefficients and heat and mass transfer rates have been computed and analyzed.
User's manual for three-dimensional analysis of propeller flow fields
Chaussee, D. S.; Kutler, P.
1983-01-01
A detailed operating manual is presented for the prop-fan computer code (in addition to supporting programs) recently developed by Kutler, Chaussee, Sorenson, and Pulliam while at the NASA'S Ames Research Center. This code solves the inviscid Euler equations using an implicit numerical procedure developed by Beam and Warming of Ames. A description of the underlying theory, numerical techniques, and boundary conditions with equations, formulas, and methods for the mesh generation program (MGP), three dimensional prop-fan flow field program (3DPFP), and data reduction program (DRP) is provided, together with complete operating instructions. In addition, a programmer's manual is also provided to assist the user interested in modifying the codes. Included in the programmer's manual for each program is a description of the input and output variables, flow charts, program listings, sample input and output data, and operating hints.
Advanced numerical methods for three dimensional two-phase flow calculations
Energy Technology Data Exchange (ETDEWEB)
Toumi, I. [Laboratoire d`Etudes Thermiques des Reacteurs, Gif sur Yvette (France); Caruge, D. [Institut de Protection et de Surete Nucleaire, Fontenay aux Roses (France)
1997-07-01
This paper is devoted to new numerical methods developed for both one and three dimensional two-phase flow calculations. These methods are finite volume numerical methods and are based on the use of Approximate Riemann Solvers concepts to define convective fluxes versus mean cell quantities. The first part of the paper presents the numerical method for a one dimensional hyperbolic two-fluid model including differential terms as added mass and interface pressure. This numerical solution scheme makes use of the Riemann problem solution to define backward and forward differencing to approximate spatial derivatives. The construction of this approximate Riemann solver uses an extension of Roe`s method that has been successfully used to solve gas dynamic equations. As far as the two-fluid model is hyperbolic, this numerical method seems very efficient for the numerical solution of two-phase flow problems. The scheme was applied both to shock tube problems and to standard tests for two-fluid computer codes. The second part describes the numerical method in the three dimensional case. The authors discuss also some improvements performed to obtain a fully implicit solution method that provides fast running steady state calculations. Such a scheme is not implemented in a thermal-hydraulic computer code devoted to 3-D steady-state and transient computations. Some results obtained for Pressurised Water Reactors concerning upper plenum calculations and a steady state flow in the core with rod bow effect evaluation are presented. In practice these new numerical methods have proved to be stable on non staggered grids and capable of generating accurate non oscillating solutions for two-phase flow calculations.
Multi-GPU three dimensional Stokes solver for simulating glacier flow
Licul, Aleksandar; Herman, Frédéric; Podladchikov, Yuri; Räss, Ludovic; Omlin, Samuel
2016-04-01
Here we present how we have recently developed a three-dimensional Stokes solver on the GPUs and apply it to a glacier flow. We numerically solve the Stokes momentum balance equations together with the incompressibility equation, while also taking into account strong nonlinearities for ice rheology. We have developed a fully three-dimensional numerical MATLAB application based on an iterative finite difference scheme with preconditioning of residuals. Differential equations are discretized on a regular staggered grid. We have ported it to C-CUDA to run it on GPU's in parallel, using MPI. We demonstrate the accuracy and efficiency of our developed model by manufactured analytical solution test for three-dimensional Stokes ice sheet models (Leng et al.,2013) and by comparison with other well-established ice sheet models on diagnostic ISMIP-HOM benchmark experiments (Pattyn et al., 2008). The results show that our developed model is capable to accurately and efficiently solve Stokes system of equations in a variety of different test scenarios, while preserving good parallel efficiency on up to 80 GPU's. For example, in 3D test scenarios with 250000 grid points our solver converges in around 3 minutes for single precision computations and around 10 minutes for double precision computations. We have also optimized the developed code to efficiently run on our newly acquired state-of-the-art GPU cluster octopus. This allows us to solve our problem on more than 20 million grid points, by just increasing the number of GPU used, while keeping the computation time the same. In future work we will apply our solver to real world applications and implement the free surface evolution capabilities. REFERENCES Leng,W.,Ju,L.,Gunzburger,M. & Price,S., 2013. Manufactured solutions and the verification of three-dimensional stokes ice-sheet models. Cryosphere 7,19-29. Pattyn, F., Perichon, L., Aschwanden, A., Breuer, B., de Smedt, B., Gagliardini, O., Gudmundsson,G.H., Hindmarsh, R
Kobayashi, Y.; Towhata, I.
2005-01-01
Since the design policy of countermeasures to liquefaction is currently prevention of liquefaction, conventional liquefaction analysis aims to predict the possibility of liquefaction at a target site. However, quantitative prediction of ground flow by liquefaction has been studied for new design policy that allows the deformation of liquefied ground if it is not critical. This paper presents a method for prediction of the ground deformation related liquefaction by viscous fluid model. Furthermore, the mitigation effect of a sheet pile wall is assessed by modeling a sheet pile wall as an elastic beam.
Three-Dimensional Interactions and Vortical Flows with Emphasis on High Speeds
1980-07-01
Rainbird (1968b). 24 Overall Viscous Flow Field - With the introduction of fast computers, such as the CDC 7600, a moi ’r less complete picture of the...1M)e) (b) TURBULENT: u.-" 200 ftfm~; RD - 2 x 106, R6 -0.4 x 106! ( FAST AND HOXEY lft) S5 Fig. 34 Skin-friction lines on surfaces about protuberance...isuliatin n crclarcoe a hgh eltiv icidnc, a2,wit trbuen layes (ainird t a. 166) LIA4o -- "o Fi. 7 ildt sr facealo visualization on cirular~s cuofne of
Software Package \\Nesvetay-3D" for modeling three-dimensional flows of monatomic rarefied gas
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V. A. Titarev
2014-01-01
Full Text Available Analysis of three-dimensional rarefied gas flowsin microdevices (micropipes, micropumps etc and over re-entry vehicles requires development of methods of computational modelling. One of such methods is the direct numerical solution of the Boltzmann kinetic equation for the velocity distribution function with either exact or approximate (model collision integral. At present, for flows of monatomic rarefied gas the Shakhov model kinetic equation, also called S-model, has gained wide-spread use. The equation can be regarded as a model equation of the incomplete thirdorder approximation. Despite its relative simplicity, the S-model is still a complicated integrodifferential equation of high dimension. The numerical solution of such an equation requires high-accuracy parallel methods.The present work is a review of recent results concerning the development and application of three-dimensional computer package Nesvetay-3D intended for modelling of rarefied gas flows. The package solves Boltzmann kinetic equation with the BGK (Krook and Shakhov model collision integrals using the discrete velocity approach. Calculations are carried out in non-dimensional variables. A finite integration domain and a mesh are introduced in the molecular velocity space. Next, the kinetic equation is re-written as a system of kinetic equations for each of the discrete velocities. The system is solved using an implicit finite-volume method of Godunov type. The steady-state solution is computed by a time marching method. High order of spatial accuracy is achieved by using a piece-wise linear representation of the distribution function in each spatial cell. In general, the coefficients of such an approximation are found using the least-square method. Arbitrary unstructured meshes in the physical space can be used in calculations, which allow considering flows over objects of general geometrical shape. Conservative property of the method with respect to the model collision
Reynolds number effects on three-dimensional flow control over a square cylinder
Malekzadeh, S.; Mirzaee, I.; Pourmahmoud, N.
2018-04-01
In this article, the effects of Reynolds number on three-dimensional flow over a square cylinder with flow control are discussed at moderate Reynolds numbers, i.e. Re W = 200–1000 (based on the width of the square cylinder and the inlet flow velocity). The flow is controlled by a thin vertical plate placed upstream of the cylinder. The vorticity structures at different Reynolds numbers, turbulent kinetic energy, Reynolds stresses, and mean and fluctuating fluid forces on the square cylinder in the presence of the control plate are investigated in order to determine the characteristics of the transient flow regime at the wake region behind the square cylinder. The results show that the transitional process of the flow regime from laminar to turbulent in the wake region behind the square cylinder at Re W = 300–600 causes the pulsation phenomena to happen in the instantaneous lift signals of the square cylinder, and both of spanwise instability modes of A and B, as well as the dislocation phenomena are presented in the wake region behind the cylinder. It is also found that the mean and fluctuating fluid forces of the square cylinder in the presence of the control plate decrease in comparison to the single square cylinder, except for the rms drag coefficient at Re W = 300.
Richardson, S. I. Heath; Baggaley, A. W.; Hill, N. A.
2018-02-01
We study the effects of imposed three-dimensional flows on the trajectories and mixing of gyrotactic swimming microorganisms and identify phenomena not seen in flows restricted to two dimensions. Through numerical simulation of Taylor-Green and Arnold-Beltrami-Childress (ABC) flows, we explore the role that the flow and the cell shape play in determining the long-term configuration of the cells' trajectories, which often take the form of multiple sinuous and helical "plumelike" structures, even in the chaotic ABC flow. This gyrotactic suppression of Lagrangian chaos persists even in the presence of random noise. Analytical solutions for a number of cases reveal the how plumes form and the nature of the competition between torques acting on individual cells. Furthermore, studies of Lyapunov exponents reveal that, as the ratio of cell swimming speed relative to the flow speed increases from zero, the initial chaotic trajectories are first suppressed and then give way to a second unexpected window of chaotic trajectories at speeds greater than unity, before suppression of chaos at high relative swimming speeds.
Lagrangian transport in a class of three-dimensional buoyancy-driven flows
Contreras, Sebastian; Speetjens, Michel; Clercx, Herman
2017-11-01
The study concerns the Lagrangian dynamics of three-dimensional (3D) buoyancy-driven cavity flows under steady and laminar conditions due to a global temperature gradient imposed via an opposite hot and cold sidewall. This serves as archetypal configuration for natural-convection flows in which gravity is perpendicular to the global temperature gradient. Limited insight into the Lagrangian properties of this class of flows motivates this study. The 3D Lagrangian dynamics are investigated in terms of the generic structure of the Lagrangian flow topology that is described in terms of the Grashof number (Gr) and the Prandtl number (Pr). Gr is the principal control parameter for the flow topology: vanishing Gr yields a state of closed streamlines (integrable state); increasing Gr causes the formation of toroidal coherent structures embedded in chaotic streamlines governed by Hamiltonian mechanisms. Fluid inertia prevails for ``smaller'' Gr. A buoyancy-induced bifurcation of the flow topology occurs for ``larger'' Gr and underlies the emergence of ``secondary rolls'' and secondary tori for ``larger'' Pr. Stagnation points and corresponding manifold interactions are key to the dynamics. S.C. acknowledges financial support from Consejo Nacional de Ciencia y Tecnología (CONACYT).
McBride, D.; Cross, M.; Croft, N.; Bennett, C.; Gebhardt, J.
2006-03-01
A computational procedure is presented for solving complex variably saturated flows in porous media, that may easily be implemented into existing conventional finite-volume-based computational fluid dynamics codes, so that their functionality might be geared upon to readily enable the modelling of a complex suite of interacting fluid, thermal and chemical reaction process physics. This procedure has been integrated within a multi-physics finite volume unstructured mesh framework, allowing arbitrarily complex three-dimensional geometries to be modelled. The model is particularly targeted at ore heap-leaching processes, which encounter complex flow problems, such as infiltration into dry soil, drainage, perched water tables and flow through heterogeneous materials, but is equally applicable to any process involving flow through porous media, such as in environmental recovery processes. The computational procedure is based on the mixed form of the classical Richards equation, employing an adaptive transformed mixed algorithm that is numerically robust and significantly reduces compute (or CPU) time. The computational procedure is accurate (compares well with other methods and analytical data), comprehensive (representing any kind of porous flow model), and is computationally efficient. As such, this procedure provides a suitable basis for the implementation of large-scale industrial heap-leach models.
Three dimensional boundary layer flow of a viscoelastic nanofluid with Soret and Dufour effects
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M. Ramzan
2016-03-01
Full Text Available The present research focuses on the three-dimensional flow of viscoelastic fluid in the presence of Soret and Dufour effects. Effects of thermophoresis and Brownian motion are taken into account. Appropriate similarity transformations lead to nonlinear ordinary differential equations. Solution expressions of velocity, temperature and nanoparticle concentration are computed via homotopy analysis method (HAM. Convergence of obtained solutions is analyzed graphically and numerically. Results are plotted and analyzed for the dimensionless velocities, temperature and nanoparticle concentration. Values of local Nusselt and Sherwood numbers are examined through tabular form. It is observed that Temperature field is enhanced for the larger Brownian motion parameter and an increase in Dufour number gives rise to the temperature and thermal boundary layer thickness.
Free convection nanofluid flow in the stagnation-point region of a three-dimensional body.
Farooq, Umer; Xu, Hang
2014-01-01
Analytical results are presented for a steady three-dimensional free convection flow in the stagnation point region over a general curved isothermal surface placed in a nanofluid. The momentum equations in x- and y-directions, energy balance equation, and nanoparticle concentration equation are reduced to a set of four fully coupled nonlinear differential equations under appropriate similarity transformations. The well known technique optimal homotopy analysis method (OHAM) is used to obtain the exact solution explicitly, whose convergence is then checked in detail. Besides, the effects of the physical parameters, such as the Lewis number, the Brownian motion parameter, the thermophoresis parameter, and the buoyancy ratio on the profiles of velocities, temperature, and concentration, are studied and discussed. Furthermore the local skin friction coefficients in x- and y-directions, the local Nusselt number, and the local Sherwood number are examined for various values of the physical parameters.
International Nuclear Information System (INIS)
Graf, U.
1986-01-01
A combination of several numerical methods is used to construct a procedure for effective calculation of complex three-dimensional fluid flow problems. The split coefficient matrix (SCM) method is used so that the differenced equations of the hyperbolic system do not disturb correct signal propagation. The semi-discretisation of the equations of the SCM method is done with the asymmetric, separated region, weighted residual (ASWR) method to give accurate solutions on a relatively coarse mesh. For the resulting system of ordinary differential equations, a general-purpose ordinary differential equation solver is used in conjunction with a method of fractional steps for an economic solution of the large system of linear equations. (orig.) [de
Mixing in three-dimensional turbulent flow near the river confluence
Lyubimova, T.; Lepikhin, A.; Konovalov, V.; Parshakova, Ya.; Tiunov, A.
2012-04-01
Main source of potable water for Perm city having about one million inhabitants is Chusovaya water intake located in the immediate vicinity of the confluence of Chusovaya and Sylva rivers. These rivers are similar in water content but significantly different in hydrochemical regime: the water of Sylva river is characterized by high hardness and the hardness of Chusovaya river is much lower. Since the hardness is an important indicator of water quality, there arises the goal to organize the water intake in such a way that water was characterized by minimal hardness. The solution to this problem in the discussed case is complicated due to the fact that the water intake is located in the zone of hydraulic backwater of the Kama hydroelectric power station and the hydrodynamic regime in this zone depends not only on the cumulative effect of hydrological regimes of Chusovaya and Sylva rivers but also on the filling level of the Kama water reservoir and on the reset mode on the Kama hydroelectric power station. From the viewpoint of ensuring the standard water quality, the dynamics of water hardness in the considered rivers and its dependence on the water flow rates is of the fundamental importance. This is especially significant for low flow rates typical for winter seasons. For large flow velocities and small differences in mineralization, one could expect sufficient homogeneity of water composition in depth due to intense vertical mixing. And in winter season, at low flow velocities and significant differences in mineralization, considerable vertical inhomogeneity of water composition may arise. Experimental measurements show that, in winter low flow season, specific electric conductivity and, consequently, mineralization and hardness of the water near the bottom several times larger than their values near the surface. To study the formation of vertical stratification in different conditions, numerical simulation of mixing in three-dimensional turbulent flows for the
Yang, Ren; Feeback, Daniel L.; Wang, Wan-Jun
2005-01-01
This paper details a novel three-dimensional (3D) hydro-focusing micro cell sorter for micro flow cytometry applications. The unit was microfabricated by means of SU-8 3D lithography. The 3D microstructure for coaxial sheathing was designed, microfabricated, and tested. Three-dimensional hydrofocusing capability was demonstrated with an experiment to sort labeled tanned sheep erythrocytes (red blood cells). This polymer hydro-focusing microstructure is easily microfabricated and integrated with other polymer microfluidic structures. Keywords: SU-8, three-dimensional hydro-focusing, microfluidic, microchannel, cytometer
Finite analytic numerical method for three-dimensional fluid flow in heterogeneous porous media
Wang, Yan-Feng; Liu, Zhi-Feng; Wang, Xiao-Hong
2014-12-01
Understanding fluid flows in heterogeneous porous media is fundamental to applied geosciences. The wide connectivity variations in the natural aquifer or oil reservoirs make the equivalent permeability have strong spatial variations. When performing the simulations for subsurface flows, the permeabilities may have strong discontinuities across the interfaces between different grid cells. Utilizing the traditional numerical schemes to simulate flows in strong heterogeneous media, the refinement ratio for the grid cell needs to increase dramatically to get an accurate result. Recently, we proposed a finite analytic numerical scheme to solve the two-dimensional fluid flows in heterogeneous porous media. With only 2 × 2 or 3 × 3 subdivisions, this scheme can provide rather accurate solutions. In this paper, we develop the finite analytic numerical method for solving the three-dimensional fluid flows in heterogeneous porous media. For the rectangular grid system, it is generally proposed that the pressure gradient in a plane normal to the edge joining different permeability regions will tend to infinite as approaching the edge according to a typical power-law solution and the tangential derivate of the pressure along the edge must be of limited value due to the pressure continuity. Consequently, the three-dimensional flow will reduce to the two-dimensional one in the neighborhood around each edge. Such quasi-two-dimensional behavior is then applied to construct a finite analytic numerical scheme. Numerical examples show that the proposed scheme can provide rather accurate solutions with only 2 × 2 × 2 or 3 × 3 × 3 subdivisions and the convergent speed is independent of the permeability heterogeneity. Due to its high calculation efficiency, the proposed scheme is utilized to test the well known LLM (Landau, Lifshitz and Matheron) conjecture, which provides keq /kG = exp (1/6σlnk2) for the isotropic log-normal porous medium. The numerical results do not
Viscous flows the practical use of theory
Brenner, Howard
1988-01-01
Representing a unique approach to the study of fluid flows, Viscous Flows demonstrates the utility of theoretical concepts and solutions for interpreting and predicting fluid flow in practical applications. By critically comparing all relevant classes of theoretical solutions with experimental data and/or general numerical solutions, it focuses on the range of validity of theoretical expressions rather than on their intrinsic character.This book features extensive use of dimensional analysis on both models and variables, and extensive development of theoretically based correlating equations.
Three-Dimensional Numerical Analysis of LOX/Kerosene Engine Exhaust Plume Flow Field Characteristics
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Hong-hua Cai
2017-01-01
Full Text Available Aiming at calculating and studying the flow field characteristics of engine exhaust plume and comparative analyzing the effects of different chemical reaction mechanisms on the engine exhaust plume flow field characteristics, a method considering fully the combustion state influence is put forward, which is applied to exhaust plume flow field calculation of multinozzle engine. On this basis, a three-dimensional numerical analysis of the effects of different chemical reaction mechanisms on LOX/kerosene engine exhaust plume flow field characteristics was carried out. It is found that multistep chemical reaction can accurately describe the combustion process in the LOX/kerosene engine, the average chamber pressure from the calculation is 4.63% greater than that of the test, and the average chamber temperature from the calculation is 3.34% greater than that from the thermodynamic calculation. The exhaust plumes of single nozzle and double nozzle calculated using the global chemical reaction are longer than those using the multistep chemical reaction; the highest temperature and the highest velocity on the plume axis calculated using the former are greater than that using the latter. The important influence of chemical reaction mechanism must be considered in the study of the fixing structure of double nozzle engine on the rocket body.
Flow transitions in three-dimensional double-diffusive fingering convection in a porous cavity
Sezai, I.
2002-08-01
In the present study the existence of multiple three-dimensional double-diffusive flow patterns in a horizontal rectangular porous cavity of a square cross-section, having horizontal aspect ratios Ax = Ay = 2 is investigated numerically. Opposing vertical gradients of temperature and concentration are applied between the two horizontal walls of the cavity, where the solute gradient is destabilizing against a stabilizing temperature gradient. All vertical walls are considered to be impermeable and adiabatic. The Brinkman and Forchheimer terms are included in the momentum equations where the convective terms are retained. The effect of the buoyancy ratio, N, thermal Rayleigh number, RaT and Lewis number, Le, on the formation of multiple flow patterns is investigated over a wide range of parameters. Altogether 36 symmetric flow structures have been identified when each of the parameters N, RaT, and Le is varied independently, keeping the others as constants. The results of the calculations are presented in terms of the average Sherwood number curves consisting of different solution branches, where transitions between the branches are indicated. The flow patterns are classified according to their symmetry properties and the type of symmetries broken or preserved are identified during the bifurcation processes.
Pasta, Salvatore; Gentile, Giovanni; Raffa, Giuseppe M; Scardulla, Francesco; Bellavia, Diego; Luca, Angelo; Pilato, Michele; Scardulla, Cesare
2017-09-01
Bicuspid aortic valve (BAV)-associated ascending aneurysmal aortopathy (namely "bicuspid aortopathy") is a heterogeneous disease making surgeon predictions particularly challenging. Computational flow analysis can be used to evaluate the BAV-related hemodynamic disturbances, which likely lead to aneurysm enlargement and progression. However, the anatomic reconstruction process is time consuming so that predicting hemodynamic and structural evolution by computational modeling is unfeasible in routine clinical practice. The aim of the study was to design and develop a parametric program for three-dimensional (3D) representations of aneurysmal aorta and different BAV phenotypes starting from several measures derived by computed-tomography angiography (CTA). Assuming that wall shear stress (WSS) has an important implication on bicuspid aortopathy, computational flow analyses were then performed to estimate how different would such an important parameter be, if a parametric aortic geometry was used as compared to standard geometric reconstructions obtained by CTA scans. Morphologic parameters here documented can be used to rapidly model the aorta and any phenotypes of BAV. t-test and Bland-Altman plot demonstrated that WSS obtained by flow analysis of parametric aortic geometries was in good agreement with that obtained from the flow analysis of CTA-related geometries. The proposed program offers a rapid and automated tool for 3D anatomic representations of bicuspid aortopathy with promising application in routine clinical practice by reducing the amount of time for anatomic reconstructions. © 2017 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.
Three-dimensional Cascaded Lattice Boltzmann Model for Thermal Convective Flows
Hajabdollahi, Farzaneh; Premnath, Kannan
2017-11-01
Fluid motion driven by thermal effects, such as due to buoyancy in differentially heated enclosures arise in several natural and industrial settings, whose understanding can be achieved via numerical simulations. Lattice Boltzmann (LB) methods are efficient kinetic computational approaches for coupled flow physics problems. In this study, we develop three-dimensional (3D) LB models based on central moments and multiple relaxation times for D3Q7 and D3Q15 lattices to solve the energy transport equations in a double distribution function approach. Their collision operators lead to a cascaded structure involving higher order terms resulting in improved stability. This is coupled to a central moment based LB flow solver with source terms. The new 3D cascaded LB models for the convective flows are first validated for natural convection of air driven thermally on two vertically opposite faces in a cubic cavity at different Rayleigh numbers against prior numerical and experimental data, which show good quantitative agreement. Then, the detailed structure of the 3D flow and thermal fields and the heat transfer rates at different Rayleigh numbers are analyzed and interpreted.
Energy Technology Data Exchange (ETDEWEB)
Salah, Anis Bousbia; Vlassenbroeck, Jacques [Bel V - Subsidiary of the Belgian Federal Agency for Nuclear Contro, Brussels (Belize)
2017-04-15
Coolant mixing under natural circulation flow regime constitutes a key parameter that may play a role in the course of an accidental transient in a nuclear pressurized water reactor. This issue has motivated some experimental investigations carried out within the OECD/NEA PKL projects. The aim was to assess the coolant mixing phenomenon in the reactor pressure vessel downcomer and the core lower plenum under several asymmetric steady and unsteady flow conditions, and to provide experimental data for code validations. Former studies addressed the mixing phenomenon using, on the one hand, one-dimensional computational approaches with cross flows that are not fully validated under transient conditions and, on the other hand, expensive computational fluid dynamic tools that are not always justified for large-scale macroscopic phenomena. In the current framework, an unsteady coolant mixing experiment carried out in the Rossendorf coolant mixing test facility is simulated using the three-dimensional porous media capabilities of the thermal–hydraulic system CATHARE code. The current study allows highlighting the current capabilities of these codes and their suitability for reproducing the main phenomena occurring during asymmetric transient natural circulation mixing conditions.
Viscoelastic polymer flows and elastic turbulence in three-dimensional porous structures.
Mitchell, Jonathan; Lyons, Kyle; Howe, Andrew M; Clarke, Andrew
2016-01-14
Viscoelastic polymer solutions flowing through reservoir rocks have been found to improve oil displacement efficiency when the aqueous-phase shear-rate exceeds a critical value. A possible mechanism for this enhanced recovery is elastic turbulence that causes breakup and mobilization of trapped oil ganglia. Here, we apply nuclear magnetic resonance (NMR) pulsed field gradient (PFG) diffusion measurements in a novel way to detect increased motion of disconnected oil ganglia. The data are acquired directly from a three-dimensional (3D) opaque porous structure (sandstone) when viscoelastic fluctuations are expected to be present in the continuous phase. The measured increase in motion of trapped ganglia provides unequivocal evidence of fluctuations in the flowing phase in a fully complex 3D system. This work provides direct evidence of elastic turbulence in a realistic reservoir rock - a measurement that cannot be readily achieved by conventional laboratory methods. We support the NMR data with optical microscopy studies of fluctuating ganglia in simple two-dimensional (2D) microfluidic networks, with consistent apparent rheological behaviour of the aqueous phase, to provide conclusive evidence of elastic turbulence in the 3D structure and hence validate the proposed flow-fluctuation mechanism for enhanced oil recovery.
Numerical three-dimensional turbulent flow analysis trough a pump-turbine in the turbine modes
International Nuclear Information System (INIS)
Cvetkovski, Zlatko; Popovski, Predrag; Markov, Zoran; Lipej, Andrej
2004-01-01
During the design of a new or rehabilitated hydraulic machines, prediction of the performances is one of the most important step in development procedure. However, for re-design of old machines, a fast and reliable flow analyses tool is necessary for allocation of the 'bed geometry' condition. This work describes new computational approaches for modern re-design of a radial type single stage pump-turbine. A pump-turbine with specific speed ns = 89 was calculated, as an example of the applicability of this methodology. The simulation of three-dimensional turbulent flow through a Pump-Turbine impeller at turbine mode, as a part of the complete pump-turbine calculation [3] during the re-design procedure is presented. Four operational regimes were calculated based on the Computational Fluid Dynamics - CFD Methodology (Navier-Stokes equations and the k-e turbulent model). The mesh discretization, boundary conditions and calculated results are presented and the)) shall be useful for development, optimisation, refurbishment or rehabilitation projects, because the impeller behaviour can be a major criterion for increasing the performances of the Pump-Turbines. The complete flow field consists of spiral case, a channel between stator vanes, a channel between guide vanes, a channel between rotor vanes and complete draft tube. Two step calculations are applied. In the first step, calculation was performed for the spiral case and the stator. Second step of the calculations was performed for cascade, rotor and draft tube. (Author)
Directory of Open Access Journals (Sweden)
M. Ali Abbas
2016-03-01
Full Text Available In this present analysis, three dimensional peristaltic flow of hyperbolic tangent fluid in a non-uniform channel has been investigated. We have considered that the pressure is uniform over the whole cross section and the interial effects have been neglected. For this purpose we consider laminar flow under the assumptions of long wavelength (λ→∞ and creeping flow (Re→0 approximations. The attained highly nonlinear equations are solved with the help of Homotopy perturbation method. The influence of various physical parameters of interest is demonstrated graphically for wall tension, mass characterization, damping nature of the wall, wall rigidity, wall elastance, aspect ratio and the Weissenberg number. In this present investigation we found that the magnitude of the velocity is maximum in the center of the channel whereas it is minimum near the walls. Stream lines are also drawn to discuss the trapping mechanism for all the physical parameters. Comparison has also been presented between Newtonian and non-Newtonian fluid.
Directory of Open Access Journals (Sweden)
Qihua Zhang
Full Text Available Abstract To describe flow-induced fiber orientation, the Fokker-Planck equation is widely applied in the processing of composites and fiber suspensions. The analytical solution only exists when the Péclet number is infinite. So developing a numerical method covering a full range of Péclet number is of great significance. To accurately solve the Fokker-Planck equation, a numerical scheme based on the finite volume method is developed. Using spherical symmetry, the boundary is discretized and formulated into a cyclic tridiagonal matrix which is further solved by the CTDMA algorithm. To examine its validity, benchmark tests over a wide range of Péclet number are performed in a simple shear flow. For Pe=∞, the results agree well with the analytical solutions. For the other Pe numbers, the results are compared to results available in the literature. The tests show that this algorithm is accurate, stable, and globally conservative. Furthermore, this algorithm can be extended and used to predict the three-dimensional orientation distribution of complex suspension flows.
Computational strategies for three-dimensional flow simulations on distributed computer systems
Sankar, Lakshmi N.; Weed, Richard A.
1995-01-01
This research effort is directed towards an examination of issues involved in porting large computational fluid dynamics codes in use within the industry to a distributed computing environment. This effort addresses strategies for implementing the distributed computing in a device independent fashion and load balancing. A flow solver called TEAM presently in use at Lockheed Aeronautical Systems Company was acquired to start this effort. The following tasks were completed: (1) The TEAM code was ported to a number of distributed computing platforms including a cluster of HP workstations located in the School of Aerospace Engineering at Georgia Tech; a cluster of DEC Alpha Workstations in the Graphics visualization lab located at Georgia Tech; a cluster of SGI workstations located at NASA Ames Research Center; and an IBM SP-2 system located at NASA ARC. (2) A number of communication strategies were implemented. Specifically, the manager-worker strategy and the worker-worker strategy were tested. (3) A variety of load balancing strategies were investigated. Specifically, the static load balancing, task queue balancing and the Crutchfield algorithm were coded and evaluated. (4) The classical explicit Runge-Kutta scheme in the TEAM solver was replaced with an LU implicit scheme. And (5) the implicit TEAM-PVM solver was extensively validated through studies of unsteady transonic flow over an F-5 wing, undergoing combined bending and torsional motion. These investigations are documented in extensive detail in the dissertation, 'Computational Strategies for Three-Dimensional Flow Simulations on Distributed Computing Systems', enclosed as an appendix.
A three-dimensional model for thermal analysis in a vanadium flow battery
International Nuclear Information System (INIS)
Zheng, Qiong; Zhang, Huamin; Xing, Feng; Ma, Xiangkun; Li, Xianfeng; Ning, Guiling
2014-01-01
Highlights: • A three-dimensional model for thermal analysis in a VFB has been developed. • A quasi-static thermal behavior and temperature spatial distribution were showed. • Ohmic heat gets vital in heat generation if applied current density is large enough. • A lower porosity or a faster flow shows a more uniform temperature distribution. • The model shows good prospect in heat and temperature management for a VFB. - Abstract: A three-dimensional model for thermal analysis has been developed to gain a better understanding of thermal behavior in a vanadium flow battery (VFB). The model is based on a comprehensive description of mass, momentum, charge and energy transport and conservation, combining with a global kinetic model for reactions involving all vanadium species. The emphasis in this paper is placed on the heat losses inside a cell. A quasi-static behavior of temperature and the temperature spatial distribution were characterized via the thermal model. The simulations also indicate that the heat generation exhibits a strong dependence on the applied current density. The reaction rate and the over potential rise with an increased applied current density, resulting in the electrochemical reaction heat rises proportionally and the activation heat rises at a parabolic rate. Based on the Ohm’s law, the ohmic heat rises at a parabolic rate when the applied current density increases. As a result, the determining heat source varies when the applied current density changes. While the relative contribution of the three types of heat is dependent on the cell materials and cell geometry, the regularities of heat losses can also be attained via the model. In addition, the electrochemical reaction heat and activation heat have a lack of sensitivity to the porosity and flow rate, whereas an obvious increase of ohmic heat has been observed with the rise of the porosity. A lower porosity or a faster flow shows a better uniformity of temperature distribution in
Leaving flatland: Diagnostics for Lagrangian coherent structures in three-dimensional flows
Sulman, Mohamed H. M.; Huntley, Helga S.; Lipphardt, B. L.; Kirwan, A. D.
2013-09-01
Finite-time Lyapunov exponents (FTLE) are often used to identify Lagrangian Coherent Structures (LCS). Most applications are confined to flows on two-dimensional (2D) surfaces where the LCS are characterized as curves. The extension to three-dimensional (3D) flows, whose LCS are 2D structures embedded in a 3D volume, is theoretically straightforward. However, in geophysical flows at regional scales, full prognostic computation of the evolving 3D velocity field is not computationally feasible. The vertical or diabatic velocity, then, is either ignored or estimated as a diagnostic quantity with questionable accuracy. Even in cases with reliable 3D velocities, it may prove advantageous to minimize the computational burden by calculating trajectories from velocities on carefully chosen surfaces only. When reliable 3D velocity information is unavailable or one velocity component is explicitly ignored, a reduced FTLE form to approximate 2D LCS surfaces in a 3D volume is necessary. The accuracy of two reduced FTLE formulations is assessed here using the ABC flow and a 3D quadrupole flow as test models. One is the standard approach of knitting together FTLE patterns obtained on adjacent surfaces. The other is a new approximation accounting for the dispersion due to vertical (u,v) shear. The results are compared with those obtained from the full 3D velocity field. We introduce two diagnostic quantities to identify situations when a fully 3D computation is required for an accurate determination of the 2D LCS. For the ABC flow, we found the full 3D calculation to be necessary unless the vertical (u,v) shear is sufficiently small. However, both methods compare favorably with the 3D calculation for the quadrupole model scaled to typical open ocean conditions.
Viscous dissipation and Joule heating effects in MHD 3D flow with heat and mass fluxes
Muhammad, Taseer; Hayat, Tasawar; Shehzad, Sabir Ali; Alsaedi, Ahmed
2018-03-01
The present research explores the three-dimensional stretched flow of viscous fluid in the presence of prescribed heat (PHF) and concentration (PCF) fluxes. Mathematical formulation is developed in the presence of chemical reaction, viscous dissipation and Joule heating effects. Fluid is electrically conducting in the presence of an applied magnetic field. Appropriate transformations yield the nonlinear ordinary differential systems. The resulting nonlinear system has been solved. Graphs are plotted to examine the impacts of physical parameters on the temperature and concentration distributions. Skin friction coefficients and local Nusselt and Sherwood numbers are computed and analyzed.
Three-dimensional simulation of a solid-liquid flow by the DEM-SPH method
Sun, Xiaosong; Sakai, Mikio; Yamada, Yoshinori
2013-09-01
In this paper, we describe a new Lagrangian-Lagrangian algorithm, which is referred to be the DEM-SPH method, for solid-liquid flows involving free surfaces. The DEM solid phase and the SPH liquid phase are coupled using the local averaging technique described by Lagrangian approaches, where both the continuity equation and the interaction force, i.e. drag force, are connected with the local mean voidage. Conservative forms of momentum transformation are derived for the DEM-SPH interaction via a variational approach. By introducing a correction to the SPH approximation with explicit inclusion of boundary information, arbitrary boundaries can be modeled without any extra wall particles, where the boundary is used commonly for both DEM and SPH phases. We deploy level-set distance functions to efficiently construct and evaluate this boundary model. To examine the validity of the present method, we perform three-dimensional simulations of a dynamic flow in a solid-liquid dam break and a quasi-steady flow in a rotating cylindrical tank; and we conduct validation experiments to justify the simulation results. In the dam-break problem, positions of wave fronts during the collapse are computed and compared with experimental measurements; for the circulating tank, some macroscopic aspects of the steady flow, e.g. the shape, dimension and velocity profile of the solid bed, are obtained for validation data. In both cases, the simulation results are in good agreement with those of the experiment. Consequently, the DEM-SPH method is proved to be adequate in modeling solid-liquid flows through this study.
Three-dimensional flow past a fixed or freely vibrating cylinder in the early turbulent regime
Gsell, Simon; Bourguet, Rémi; Braza, Marianna
2018-01-01
The three-dimensional structure of the flow downstream of a circular cylinder, either fixed or subjected to vortex-induced vibrations, is investigated by means of numerical simulation, at Reynolds number 3900, based on the cylinder diameter and current velocity. The flow exhibits pronounced fluctuations distributed along the span in all studied cases. Qualitatively, it is characterized by spanwise undulations of the shear layers separating from the body and the development of vortices elongated in the plane normal to its axis (planar vortices). A quantitative analysis of crossflow vorticity fluctuations in the spanwise direction reveals a peak of fluctuation amplitude in the near region (i.e., area of formation of the spanwise wake vortices) and opposite trends of the spanwise wavelength in the shear layer and wake regions; the wavelength tends to decrease as a function of the streamwise distance in the shear layers down to a minimum value close to 0.5 body diameters and then slowly increases further in the wake. The spanwise structure of the flow is differently altered in these two regions, once the cylinder vibrates. In the shear layer region, body motion is associated with an enhancement of planar vortex formation. The amplification of vorticity spanwise fluctuations in this region is accompanied by a reduction of the spanwise wavelength; it is found to decrease as a function of the instantaneous Reynolds number based on the instantaneous flow velocity seen by the moving body, following the global trend of the wavelength versus Reynolds number previously reported for fixed cylinders. In the wake region, the flow spanwise structure is essentially unaltered compared to the fixed body case, in spite of the major distortions of the streamwise and crossflow length scales.
Three dimensional flow structures and turbulence distribution in an urban environment
Monnier, Bruno
Understanding and controlling the dispersion of pollutants and contaminants in urban areas has become a major focus recently. Field measurements, numerical studies, and wind tunnel experiments have increased in number. Specifically, there is a growing need for a spatio-temporal description of such complex flow fields under well-controlled conditions, typically obtained in wind tunnel experiments. The reduced scale model of interest is a 4 by 3 array of cuboid blocks in an experimentally modeled, neutrally stratified, atmospheric boundary-layer. The use of Stereoscopic Particle Image Velocimetry (SPIV) allows for a three-dimensional description of this urban flow. A large amount of SPIV data is collected upstream and in each middle street of the urban environment allowing for a study of the flow evolution from street to street. Valuable information about the flow structures are presented along with the mechanisms responsible for contaminant transport and dispersion. The effects of small incidence angles of the incoming flow with respect to the urban array and the effects of streamwise spacing between streets on the flow characteristics are investigated. A major observation from this work is that a strong channeling effect is observed for incidence angles as small as 4.5° and is found to be comparable in strength to that observed in other investigations for much larger angles. A coupling between this channeling effect and the structures responsible for contaminant transport is revealed. An innovative method using sparse measurements to estimate the continuous temporal evolution of the dominant structures in the flow is investigated. Proper Orthogonal Decomposition is used to obtain a reduced-order representation (ROR) of the flow field. Sparse velocity measurements within the domain serve as input to measurement models that provide an estimation of the ROR of the velocity field. This ROR of the flow field could be regarded as the first that provides a temporal
International Nuclear Information System (INIS)
Morisada, Y.; Fujii, H.; Kawahito, Y.; Nakata, K.; Tanaka, M.
2011-01-01
Material flow during friction stir welding is crucial to obtaining sound joints. However, this phenomenon is still not fully understood despite many investigations and numerous models. In this study, the material flow is three-dimensionally visualized by X-ray radiography using a tiny spherical tungsten tracer. The movement of the tracer during the friction stir welding is observed by two pairs of X-ray transmission real-time imaging systems. The three-dimensional material flow is obtained by following the locus of the tracer.
Three-dimensional instabilities for the flow around a heaving foil
Sun, Liping; Deng, Jian; Shao, Xueming
2018-01-01
This paper investigates the three-dimensional instabilities of the flow past a periodically heaving airfoil. By comparison with a pitching foil [Deng et al., Phys. Rev. E 92, 063013 (2015), 10.1103/PhysRevE.92.063013], here we present distinctive characteristics for the heaving foil, particulary regarding its Floquet modes. By increasing the frequency (Sr), or equivalently decreasing the amplitude (AD) along the marginal stability curve in the (Sr ,AD ) phase space, the critical Floquet mode emerges sequentially as A, quasiperiodic (QP), and B. It is interesting to note that both modes A and B are synchronous with the base flow, in contrast to the quasiperiodic mode QP. To further investigate the instability across the marginal curve, we fix the frequency at Sr =0.187 , of which the critical Floquet mode is located in the synchronous regime, while varying AD around the critical point. We find that the dominant mode switches from mode A to mode B, while mode QP never becomes critical as we increase AD. We note that mode S, a subharmonic mode, can also be unstable, which, however, is not physically realizable, because the magnitude of its Floquet multiplier is always smaller than that of mode B. We have also studied the influence of various Reynolds numbers at the same critical point on the marginal stability curve, with the results resembling that by varying the amplitude AD.
Three-dimensional features of GAM zonal flows in the HL-2A tokamak
International Nuclear Information System (INIS)
Yan, L.W.; Cheng, J.; Hong, W.Y.; Zhao, K.J.; Lan, T.; Dong, J.Q.; Liu, A.D.; Yu, C.X.; Yu, D.L.; Qian, J.; Huang, Y.; Yang, Q.W.; Ding, X.T.; Liu, Y.; Pan, C.H.
2007-01-01
A novel design of the three-step Langmuir probe (TSLP) array has been developed to investigate the zonal flow (ZF) physics in the HL-2A tokamak. Three TSLP arrays are applied to measure the three-dimensional (3D) features of ZFs. They are separated by 65 mm in the poloidal and 800 mm in the toroidal directions, respectively. The 3D properties of the geodesic acoustic mode (GAM) ZFs are presented. The poloidal and toroidal modes of the radial electric fields of the GAM perturbations are simultaneously determined in the HL-2A tokamak for the first time. The modes have narrow radial wave numbers (k r ρ i = 0.03-0.07) and short radial scale lengths (2.4-4.2 cm). High coherence of both the GAM and the ambient turbulence separated by toroidal 22.5 0 along a magnetic field line is observed, which contrasts with the high coherence of the GAM and the low coherence of the ambient turbulence apart from the field line. The nonlinear three wave coupling between the turbulent fluctuations and the ZFs is a plausible mechanism for flow generation. The skewness and kurtosis spectra of the probability distribution function of the potential perturbations are contrasted with the corresponding bicoherence for the first time, which support the three wave coupling mechanism
Hayat, Tasawar; Ashraf, Muhammad Bilal; Alsulami, Hamed H; Alhuthali, Muhammad Shahab
2014-01-01
The objective of present research is to examine the thermal radiation effect in three-dimensional mixed convection flow of viscoelastic fluid. The boundary layer analysis has been discussed for flow by an exponentially stretching surface with convective conditions. The resulting partial differential equations are reduced into a system of nonlinear ordinary differential equations using appropriate transformations. The series solutions are developed through a modern technique known as the homotopy analysis method. The convergent expressions of velocity components and temperature are derived. The solutions obtained are dependent on seven sundry parameters including the viscoelastic parameter, mixed convection parameter, ratio parameter, temperature exponent, Prandtl number, Biot number and radiation parameter. A systematic study is performed to analyze the impacts of these influential parameters on the velocity and temperature, the skin friction coefficients and the local Nusselt number. It is observed that mixed convection parameter in momentum and thermal boundary layers has opposite role. Thermal boundary layer is found to decrease when ratio parameter, Prandtl number and temperature exponent are increased. Local Nusselt number is increasing function of viscoelastic parameter and Biot number. Radiation parameter on the Nusselt number has opposite effects when compared with viscoelastic parameter.
An Incompressible Three-Dimensional Multiphase Particle-in-Cell Model for Dense Particle Flows
Snider, D. M.
2001-07-01
A three-dimensional, incompressible, multiphase particle-in-cell method is presented for dense particle flows. The numerical technique solves the governing equations of the fluid phase using a continuum model and those of the particle phase using a Lagrangian model. Difficulties associated with calculating interparticle interactions for dense particle flows with volume fractions above 5% have been eliminated by mapping particle properties to an Eulerian grid and then mapping back computed stress tensors to particle positions. A subgrid particle, normal stress model for discrete particles which is robust and eliminates the need for an implicit calculation of the particle normal stress on the grid is presented. Interpolation operators and their properties are defined which provide compact support, are conservative, and provide fast solution for a large particle population. The solution scheme allows for distributions of types, sizes, and density of particles, with no numerical diffusion from the Lagrangian particle calculations. Particles are implicitly coupled to the fluid phase, and the fluid momentum and pressure equations are implicitly solved, which gives a robust solution.
Three-dimensional modeling of diesel engine intake flow, combustion and emissions-II
Energy Technology Data Exchange (ETDEWEB)
Reitz, R.D.; Rutland, C.J.
1993-09-01
A three-dimensional computer code, KIVA, is being modified to include state-of-the-art submodels for diesel engine flow and combustion. Improved and/or new submodels which have already been implemented and previously reported are: Wall heat transfer with unsteadiness and compressibility, laminar-turbulent characteristic time combustion with unburned HC and Zeldo`vich NO{sub x}, and spray/wall impingement with rebounding and sliding drops. Progress on the implementation of improved spray drop drag and drop breakup models, the formulation and testing of a multistep kinetics ignition model and preliminary soot modeling results are described in this report. In addition, the use of a block structured version of KIVA to model the intake flow process is described. A grid generation scheme has been developed for modeling realistic (complex) engine geometries, and computations have been made of intake flow in the ports and combustion chamber of a two-intake-valve engine. The research also involves the use of the code to assess the effects of subprocesses on diesel engine performance. The accuracy of the predictions is being tested by comparisons with engine experiments. To date, comparisons have been made with measured engine cylinder pressure, temperature and heat flux data, and the model results are in good agreement with the experiments. Work is in progress that will allow validation of in-cylinder flow and soot formation predictions. An engine test facility is described that is being used to provide the needed validation data. Test results have been obtained showing the effect of injection rate and split injections on engine performance and emissions.
Three-dimensional measurement of the laminar flow field inside a static mixer
Speetjens, Michel; Jilisen, Rene; Bloemen, Paul
2011-11-01
Static mixers are widely used in industry for laminar mixing of viscous fluids as e.g. polymers and food stuffs. Moreover, given the similarities in flow regime, static mixers often serve as model for compact mixers for process intensification and even for micro-mixers. This practical relevance has motivated a host of studies on the mixing characteristics of static mixers and their small-scale counterparts. However, these studies are primarily theoretical and numerical. Experimental studies, in contrast, are relatively rare and typically restricted to local 2D flow characteristics or integral quantities (pressure drop, residence-time distributions). The current study concerns 3D measurements on the laminar flow field inside a static mixer using 3D Particle-Tracking Velocimetry (3D-PTV) Key challenges to the 3D-PTV image-processing procedure are the optical distortion and degradation of the particle imagery due to light refraction and reflection caused by the cylindrical boundary and the internal elements. Ways to tackle these challenges are discussed and first successful 3D measurements in an actual industrial static mixer are presented.
Directory of Open Access Journals (Sweden)
Sanghyeon Kim
2018-02-01
Full Text Available In this study, cavitation flow around a hydrofoil and its radiated hydro-acoustic fields were numerically investigated, with an emphasis on the effects of viscous flux vectors. The full three-dimensional unsteady compressible Reynolds-averaged Navier–Stokes equations were numerically solved. The mass transfer model was adopted to model phase changes between liquid water and vapor. To resolve the numerical instability problem arising from the rapid changes in local density and speed of sound of the mixture, the preconditioning and dual-time stepping methods were employed. The filter-based turbulent model was applied to resolve the unstable cavitation flow field more accurately. In splitting the viscous terms, three approaches for dealing with viscous flux vectors were considered: the so-called viscous lagging, full viscous, and thin-layer models. Radiated hydro-acoustic waves were predicted by applying the Ffowcs Williams and Hawkings equations. The effects of the viscous flux vectors on the predicted flow fields and its radiated noise were then examined by comparing the hydro-dynamic forces, velocity distribution, volume fraction, far-field sound directivities, and sound spectrum of the three approaches. The results revealed that the thin-layer model can provide predictions as accurate as the full viscous model, but required less computational time.
International Nuclear Information System (INIS)
Klein, S A; Moran, J L; Posner, J D; Frakes, D H
2012-01-01
We present a diagnostic platform for measuring three-dimensional three-component (3D3C) velocity fields in microscopic volumes. The imaging system uses high-speed Nipkow spinning disk confocal microscopy. Confocal microscopy provides optical sectioning using pinhole spatial filtering which rejects light originating from out-of-focus objects. The system accomplishes volumetric scanning by rapid translation of the high numerical aperture objective using a piezo objective positioner. The motion of fluorescent microspheres is quantified using 3D3C super resolution particle-imaging velocimetry with instantaneous spatial resolutions of the order of 5 µm or less in all three dimensions. We examine 3D3C flow in a PDMS microchannel with an expanding section at 3D acquisition rates of 30 Hz, and find strong agreement with a computational model. Equations from the PIV and PTV literature adapted for a scanning objective provide estimates of maximum measurable velocity. The technique allows for isosurface visualization of 3D particle motion and robust high spatial resolution velocity measurements without requiring a calibration step or reconstruction algorithms. (paper)
Xiang, G.; Wang, C.; Teng, H.; Jiang, Z.
2018-03-01
This study explores the three-dimensional (3D) wave configurations induced by 3D asymmetrical intersecting compression wedges in supersonic and hypersonic inviscid flows. By using the "spatial dimension reduction" approach, the problem of 3D steady shock/shock interaction is converted to that of the interaction of two moving shock waves in the characteristic two-dimensional (2D) plane. Shock polar theory is used to analyze the shock configurations in asymmetrical situations. The results show that various shock configurations exist in 3D asymmetrical shock wave interactions, including regular interaction, transitioned regular interaction, single Mach interaction, inverse single Mach interaction, transitional double Mach interaction, weak shock interaction, and weak single Mach interaction. All of the above 3D steady shock/shock interactions have their corresponding 2D moving shock/shock interaction configurations. Numerical simulations are performed by solving the 3D inviscid Euler equations with the non-oscillatory, non-free parameters, dissipative (NND) numerical scheme, and good agreement with the theoretical analysis is obtained. Furthermore, the comparison of results show that the concept of the "virtual wall" in shock dynamics theory is helpful for understanding the mechanism of two-dimensional shock/shock interactions.
Pore-scale simulation of fluid flow and solute dispersion in three-dimensional porous media
Icardi, Matteo
2014-07-31
In the present work fluid flow and solute transport through porous media are described by solving the governing equations at the pore scale with finite-volume discretization. Instead of solving the simplified Stokes equation (very often employed in this context) the full Navier-Stokes equation is used here. The realistic three-dimensional porous medium is created in this work by packing together, with standard ballistic physics, irregular and polydisperse objects. Emphasis is placed on numerical issues related to mesh generation and spatial discretization, which play an important role in determining the final accuracy of the finite-volume scheme and are often overlooked. The simulations performed are then analyzed in terms of velocity distributions and dispersion rates in a wider range of operating conditions, when compared with other works carried out by solving the Stokes equation. Results show that dispersion within the analyzed porous medium is adequately described by classical power laws obtained by analytic homogenization. Eventually the validity of Fickian diffusion to treat dispersion in porous media is also assessed. © 2014 American Physical Society.
Three dimensional cerebral blood flow in patients with idiopathic Parkinson's disease
International Nuclear Information System (INIS)
Hata, Takashi
1987-01-01
Three dimensional local cerebral blood flow values were measured in 28 patients with idiopathic Parkinson's disease without dementia and 17 control subjects, by means of xenon enhanced CT method using low concentration cold xenon and autoradiographic strategy. The results demonstrated that local cerebral perfusion in the patients with Parkinson's disease decreased with close correlations with aging and severity of the clinical symptoms and signs. Stepwise multiregression analysis revealed that mean CBF values and 1-CBF values through thalamus and white matter decreased primarily depending on aging and degree of brain atrophy, whereas 1-CBF values through basal ganglia decreased depending on severity of disease. The spatial distributions of 1-CBF were maintained normally and symmetrically even in the severely affected cases or in those with hemiparkinsonism, therefore hyperfrontalities were well preserved in all of the patients. Acute intravenous administration of L-DOPA gave rise to a diffuse increase in 1-CBF only in the patients and the increment was more prominent in patients severely affected than in those mildly affected. It was concluded that reduction of 1-CBF in the basal ganglia and cortex may be attributed to hypometabolism in the mesostriatal and mesocortical dopaminergic system. (author)
Chung, Woo-Young; Choi, Byoung-Joo; Lim, Seong-Hoon; Matsuo, Yoshiki; Lennon, Ryan J; Gulati, Rajiv; Sandhu, Gurpreet S; Holmes, David R; Rihal, Charanjit S; Lerman, Amir
2015-06-01
Conventional coronary angiography (CAG) has limitations in evaluating lesions producing ischemia. Three dimensional quantitative coronary angiography (3D-QCA) shows reconstructed images of CAG using computer based algorithm, the Cardio-op B system (Paieon Medical, Rosh Ha'ayin, Israel). The aim of this study was to evaluate whether 3D-QCA can reliably predict ischemia assessed by myocardial fractional flow reserve (FFR) < 0.80. 3D-QCA images were reconstructed from CAG which also were evaluated with FFR to assess ischemia. Minimal luminal diameter (MLD), percent diameter stenosis (%DS), minimal luminal area (MLA), and percent area stenosis (%AS) were obtained. The results of 3D-QCA and FFR were compared. A total of 266 patients was enrolled for the present study. FFR for all lesions ranged from 0.57 to 1.00 (0.85 ± 0.09). Measurement of MLD, %DS, MLA, and %AS all were significantly correlated with FFR (r = 0.569, 0609, 0.569, 0.670, respectively, all P < 0.001). In lesions with MLA < 4.0 mm(2), %AS of more than 65.5% had a 80% sensitivity and a 83% specificity to predict FFR < 0.80 (area under curve, AUC was 0.878). 3D-QCA can reliably predict coronary lesions producing ischemia and may be used to guide therapeutic approach for coronary artery disease.
Kinoshita, Haruyuki; Kaneda, Shohei; Fujii, Teruo; Oshima, Marie
2007-03-01
This paper presents a micro-flow diagnostic technique, 'high-speed confocal micro-particle image velocimetry (PIV)', and its application to the internal flow measurement of a droplet passing through a microchannel. A confocal micro-PIV system has been successfully constructed wherein a high-speed confocal scanner is combined with the conventional micro-PIV technique. The confocal micro-PIV system enables us to obtain a sequence of sharp and high-contrast cross-sectional particle images at 2000 frames s(-1). This study investigates the confocal depth, which is a significant parameter to determine the out-of-plane measurement resolution in confocal micro-PIV. Using the present confocal micro-PIV system, we can measure velocity distributions of micro-flows in a 228 microm x 171 microm region with a confocal depth of 1.88 microm. We also propose a three-dimensional velocity measurement method based on the confocal micro-PIV and the equation of continuity. This method enables us to measure three velocity components in a three-dimensional domain of micro flows. The confocal micro-PIV system is applied to the internal flow measurement of a droplet. We have measured three-dimensional distributions of three-component velocities of a droplet traveling in a 100 microm (width) x 58 microm (depth) channel. A volumetric velocity distribution inside a droplet is obtained by the confocal micro-PIV and the three-dimensional flow structure inside the droplet is investigated. The measurement results suggest that a three-dimensional and complex circulating flow is formed inside the droplet.
VanderWal, D.J.; Goffart, D.; Klomp, E.M.; Hoogstraten, H.W; Janssen, L.P.B.M.
Three-dimensional flow simulations of kneading elements in an intermeshing corotating twin-screw extruder are performed by solving the Navier Stokes equations with a finite element package, Sepran. Instead of using the whole geometry of the 8-shaped barrel a simplified geometry is used, representing
Wal, D.J. van der; Goffart, D.; Klomp, E.M.; Hoogstraten, H.W.; Janssen, L.P.B.M.
1996-01-01
Three-dimensional flow simulations of kneading elements in an intermeshing corotating twin-screw extruder are performed by solving the Navier Stokes equations with a finite element package, Sepran. Instead of using the whole geometry of the 8-shaped barrel a simplified geometry is used, representing
Three-dimensional structure of clumpy outflow from supercritical accretion flow onto black holes
Kobayashi, Hiroshi; Ohsuga, Ken; Takahashi, Hiroyuki R.; Kawashima, Tomohisa; Asahina, Yuta; Takeuchi, Shun; Mineshige, Shin
2018-02-01
We perform global three-dimensional (3D) radiation-hydrodynamic (RHD) simulations of outflow from supercritical accretion flow around a 10 M⊙ black hole. We only solve the outflow part, starting from the axisymmetric 2D simulation data in a nearly steady state but with small perturbations in a sinusoidal form being added in the azimuthal direction. The mass accretion rate onto the black hole is ˜102LE/c2 in the underlying 2D simulation data, and the outflow rate is ˜10 LE/c2 (with LE and c being the Eddington luminosity and speed of light, respectively). We first confirm the emergence of clumpy outflow, which was discovered by the 2D RHD simulations, above the photosphere located at a few hundreds of Schwarzschild radii (rS) from the central black hole. As prominent 3D features we find that the clumps have the shape of a torn sheet, rather than a cut string, and that they are rotating around the central black hole with a sub-Keplerian velocity at a distance of ˜103 rS from the center. The typical clump size is ˜30 rS or less in the radial direction, and is more elongated in the angular directions, ˜ hundreds of rS at most. The sheet separation ranges from 50 to 150 rS. We expect stochastic time variations when clumps pass across the line of the sight of a distant observer. Variation timescales are estimated to be several seconds for a black hole with mass of ten to several tens of M⊙, in rough agreement with the observations of some ultra-luminous X-ray sources.
International Nuclear Information System (INIS)
Song, P P; Wei, M S; Shi, L; Ma, C C
2013-01-01
Three-dimensional numerical simulations of a scroll expander were performed with dynamic mesh technology. R245fa was selected as the working fluid in the simulations. The PISO algorithm was applied to solve the governing equations with RNG k-ε turbulent model. The distribution and variation of three-dimensional flow field inside the scroll expander were obtained. The research indicates that the flow field is nonuniform and asymmetrical distributions exist inside the expander. Vortex flows also exist in some working chambers. Dynamic clearance leakage flows and inlet orifice throttling have great effects on the flow field distribution. Transient output torque and the mass flux have periodic fluctuations during the working cycles
Approximation and stability of three-dimensional natural convection flows in a porous medium
International Nuclear Information System (INIS)
Janotto, Marie-Laurence
1991-01-01
The equations of the three-dimensional natural convection in a porous medium within a differentially heated horizontal walls cavity are solved by a pseudo-spectral method. First we will present the evolution of the two main modes according to two models of convection. A few asymptotic properties connected to the small and large eddies are set up and numerically validated. A new approximate inertial manifold is then proposed. The numerical scheme used is an exponential fitting algorithm the convergence of which is proved. We will present the physical mechanism at the origin of the un-stationary three-dimensional convection at high Rayleigh numbers. (author) [fr
Three-dimensional on-chip continuous-flow polymerase chain reaction employing a single heater.
Wu, Wenming; Lee, Nae Yoon
2011-06-01
Multi-step temperature control in a polymerase chain reaction (PCR) is a limiting factor in device miniaturization and portability. In this study, we propose the fabrication of a three-dimensional (3D) microdevice employing a single heater to minimize temperature control required for an on-chip continuous-flow PCR as well as the overall footprint by stacking the device in multi-layers. Two poly(dimethylsiloxane) (PDMS) layers with differing thicknesses are vertically stacked with their microchannel-engraved sides facing down. Through-holes are made in the thicker PDMS layer, which is sandwiched between a glass substrate at the bottom and the thinner PDMS layer at the top. In this way, a fluidic conduit is realized in a 3D configuration. The assembled 3D microdevice is then placed onto a heater glass-side down. The interface of the two PDMS layers displays a relatively lower temperature than that of the PDMS and glass layers due to the low thermal conductivity of the PDMS and its physical distance from the heater. The denaturation temperature can be controlled by adjusting the temperature of the heater, while the annealing/extension temperature can be controlled automatically by molding the thicker bottom PDMS layer into the appropriate thickness calculated using a numerical derivation proposed in this study. In this way, a cumbersome temperature measurement step is eliminated. DNA amplification was successfully carried out using the proposed 3D fluidic microdevice, and the intensity of the resulting amplicon was comparable to that obtained using a thermal cycler. This novel concept of adopting a single heating source greatly simplifies the temperature control issue present in an on-chip continuous-flow PCR. It also allows the use of a commercialized hot plate as a potential heat source, paving the way for device miniaturization and portability in a highly cost-effective manner. In this study, a simple and facile technique to make arrays of through-holes for the
International Nuclear Information System (INIS)
De Marchis, M.; Napoli, E.
2012-01-01
Highlights: ► 3D irregular rough surfaces produce higher effects than those observed over 2D. ► Effective slope is a geometrical parameter representative of the roughness effects. ► 3D rough surfaces enhance the turbulence isotropization. ► 2D and 3D irregular roughness partially support the wall similarity. ► Irregular rough surfaces shear some features with regular rough walls. - Abstract: Wall-resolved Large Eddy Simulation of fully developed turbulent channel flows over two different rough surfaces is performed to investigate on the effects of irregular 2D and 3D roughness on the turbulence. The two geometries are obtained through the superimposition of sinusoidal functions having random amplitudes and different wave lengths. In the 2D configuration the irregular shape in the longitudinal direction is replicated in the transverse one, while in the 3D case the sinusoidal functions are generated both in streamwise and spanwise directions. Both channel walls are roughened in such a way as to obtain surfaces with statistically equivalent roughness height, but different shapes. In order to compare the turbulence properties over the two rough walls and to analyse the differences with a smooth wall, the simulations are performed at the same Reynolds number Re τ = 395. The same mean roughness height h = 0.05δ (δ the half channel height) is used for the rough walls. The roughness function obtained with the 3D roughness is larger than in the 2D case, although the two walls share the same mean height. Thus, the considered irregular 3D roughness is more effective in reducing the flow velocity with respect to the 2D roughness, coherently with the literature results that identified a clear dependence of the roughness function on the effective slope (see ), higher in the generated 3D rough wall. The analysis of higher-order statistics shows that the effects of the roughness, independently on its two- or three-dimensional shape, are mainly confined in the inner
International Nuclear Information System (INIS)
Billaux, D.; Long, J.C.S.; Peterson, J.E. Jr.
1990-03-01
A model for channelized flow in three-dimensional, random networks of fractures has been developed. In this model, the fractures are disc-shaped discontinuities in an impermeable matrix. Within each fracture, flow occurs only in a network of random channels. The channels in each fracture can be generated independently with random distributions of length, conductivity, and orientation in the fracture plane. Boundary conditions are specified on the sides of a ''flow region,'' and at the intersections of the channels with interior ''holes'' specified by the user to simulate boreholes or drifts. This code is part of a set of programs used to generate two-dimensional or three-dimensional random fracture networks, plot them, compute flow through them and analyze the results. 8 refs., 13 figs
Three-dimensional multi-relaxation-time lattice Boltzmann front-tracking method for two-phase flow
International Nuclear Information System (INIS)
Xie Hai-Qiong; Zeng Zhong; Zhang Liang-Qi
2016-01-01
We developed a three-dimensional multi-relaxation-time lattice Boltzmann method for incompressible and immiscible two-phase flow by coupling with a front-tracking technique. The flow field was simulated by using an Eulerian grid, an adaptive unstructured triangular Lagrangian grid was applied to track explicitly the motion of the two-fluid interface, and an indicator function was introduced to update accurately the fluid properties. The surface tension was computed directly on a triangular Lagrangian grid, and then the surface tension was distributed to the background Eulerian grid. Three benchmarks of two-phase flow, including the Laplace law for a stationary drop, the oscillation of a three-dimensional ellipsoidal drop, and the drop deformation in a shear flow, were simulated to validate the present model. (paper)
Energy Technology Data Exchange (ETDEWEB)
Jang, Jer-Huan [Department of Mechanical Engineering, Northern Taiwan Institute of Science and Technology, Beitou, Taipei 11202 (China); Yan, Wei-Mon; Li, Hung-Yi; Tsai, Wei-Che [Department of Mechatronic Engineering, Huafan University, Shih-Ting, Taipei 22305 (China)
2008-01-15
In this paper, a three-dimensional numerical model of the proton exchange membrane fuel cells (PEMFCs) with conventional flow field designs (parallel flow field, Z-type flow field, and serpentine flow field) has been established to investigate the performance and transport phenomena in the PEMFCs. The influences of the flow field designs on the fuel utilization, the water removal, and the cell performance of the PEMFC are studied. The distributions of velocity, oxygen mass fraction, current density, liquid water, and pressure with the convention flow fields are presented. For the conventional flow fields, the cell performance can be enhanced by adding the corner number, increasing the flow channel length, and decreasing the flow channel number. The cell performance of the serpentine flow field is the best, followed by the Z-type flow field and then the parallel flow field. (author)
Roszelle, Breigh N.; Deutsch, Steven; Manning, Keefe B.
2010-01-01
In order to aid the ongoing concern of limited organ availability for pediatric heart transplants, Penn State has continued development of a pulsatile Pediatric Ventricular Assist Device (PVAD). Initial studies of the PVAD observed an increase in thrombus formation due to differences in flow field physics when compared to adult sized devices, which included a higher degree of three-dimensionality. This unique flow field brings into question the use of 2D planar particle image velocimetry (PIV...
In Vivo Three-Dimensional Velocity Vector Imaging and Volumetric Flow Rate Measurements
DEFF Research Database (Denmark)
Pihl, Michael Johannes; Stuart, Matthias Bo; Tomov, Borislav Gueorguiev
2013-01-01
The three-dimensional (3-D) Transverse Oscillation (TO) method is used to obtain 3-D velocity vector estimates in two orthogonal planes. The method is suitable for a real-time implementation. Data are acquired using a Vermon 3.0 MHz 32x32 element 2-D phased array and the experimental ultrasound s...
Montessori, A; Falcucci, G; Prestininzi, P; La Rocca, M; Succi, S
2014-05-01
We investigate the accuracy and performance of the regularized version of the single-relaxation-time lattice Boltzmann equation for the case of two- and three-dimensional lid-driven cavities. The regularized version is shown to provide a significant gain in stability over the standard single-relaxation time, at a moderate computational overhead.
Fiegel, Henning C; Havers, Joerg; Kneser, Ulrich; Smith, Molly K; Moeller, Tim; Kluth, Dietrich; Mooney, David J; Rogiers, Xavier; Kaufmann, Peter M
2004-01-01
Maintenance of liver-specific function of hepatocytes in culture is still difficult. Improved culture conditions may enhance the cell growth and function of cultured cells. We investigated the effect of three-dimensional culture under flow conditions, and the influence of surface modifications in hepatocyte cultures. Hepatocytes were harvested from Lewis rats. Cells were cultured on three-dimensional polymeric poly-lactic-co-glycolic acid (PLGA) matrices in static culture, or in a pulsatile flow-bioreactor system. Different surface modifications of matrices were investigated: coating with collagen I, collagen IV, laminin, or fibronectin; or uncoated matrix. Hepatocyte numbers, DNA content, and albumin secretion rate were assessed over the observation period. Culture under flow condition significantly enhanced cell numbers. An additional improvement of this effect was observed, when matrix coating was used. Cellular function also showed a significant increase (4- to 5-fold) under flow conditions when compared with static culture. Our data showed that culture under flow conditions improves cell number, and strongly enhances cellular function. Matrix modification by coating with extracellular matrix showed overall an additive stimulatory effect. Our conclusion is that combining three-dimensional culture under flow conditions and using matrix modification significantly improves culture conditions and is therefore attractive for the development of successful culture systems for hepatocytes.
Three-dimensional coating and rimming flow: a ring of fluid on a rotating horizontal cylinder
Leslie, G. A.
2013-01-29
The steady three-dimensional flow of a thin, slowly varying ring of Newtonian fluid on either the outside or the inside of a uniformly rotating large horizontal cylinder is investigated. Specifically, we study \\'full-ring\\' solutions, corresponding to a ring of continuous, finite and non-zero thickness that extends all of the way around the cylinder. In particular, it is found that there is a critical solution corresponding to either a critical load above which no full-ring solution exists (if the rotation speed is prescribed) or a critical rotation speed below which no full-ring solution exists (if the load is prescribed). We describe the behaviour of the critical solution and, in particular, show that the critical flux, the critical load, the critical semi-width and the critical ring profile are all increasing functions of the rotation speed. In the limit of small rotation speed, the critical flux is small and the critical ring is narrow and thin, leading to a small critical load. In the limit of large rotation speed, the critical flux is large and the critical ring is wide on the upper half of the cylinder and thick on the lower half of the cylinder, leading to a large critical load. We also describe the behaviour of the non-critical full-ring solution and, in particular, show that the semi-width and the ring profile are increasing functions of the load but, in general, non-monotonic functions of the rotation speed. In the limit of large rotation speed, the ring approaches a limiting non-uniform shape, whereas in the limit of small load, the ring is narrow and thin with a uniform parabolic profile. Finally, we show that, while for most values of the rotation speed and the load the azimuthal velocity is in the same direction as the rotation of the cylinder, there is a region of parameter space close to the critical solution for sufficiently small rotation speed in which backflow occurs in a small region on the upward-moving side of the cylinder. © 2013
Directory of Open Access Journals (Sweden)
Zhi-jian Wang
2013-01-01
Full Text Available The three-dimensional flow physical model of any stage of the 20BZ4 multistage centrifugal pump is built which includes inlet region, impeller flow region, guide-vane flow region and exit region. The three-dimensional unsteady turbulent flow numerical model is created based on Navier-Stoke solver and standard k-ε turbulent equations. The method of multireference frame (MRF and SIMPLE algorithm are used to simulate the flow in multistage centrifugal pump based on FLUENT software. The distributions of relative velocity, absolute velocity, static pressure, and total pressure in guide vanes and impellers under design condition are analyzed. The simulation results show that the flow in impeller is mostly uniform, without eddy, backflow, and separation flow, and jet-wake phenomenon appears only along individual blades. There is secondary flow at blade end and exit of guide vane. Due to the different blade numbers of guide vane and impeller, the total pressure distribution is asymmetric. This paper also simulates the flow under different working conditions to predict the hydraulic performances of centrifugal pump and external characteristics including flow-lift, flow-shaft power, and flow-efficiency are attained. The simulation results are compared with the experimental results, and because of the mechanical losses and volume loss ignored, there is a little difference between them.
Magnetic field effect in three-dimensional flow of an Oldroyd-B nanofluid over a radiative surface
Energy Technology Data Exchange (ETDEWEB)
Shehzad, S.A., E-mail: ali_qau70@yahoo.com [Department of Mathematics, Comsats Institute of Information Technology, Sahiwal 57000 (Pakistan); Abdullah, Z. [Department of Mathematics, Comsats Institute of Information Technology, Sahiwal 57000 (Pakistan); Abbasi, F.M. [Department of Mathematics, Comsats Institute of Information Technology, Islamabad 44000 (Pakistan); Hayat, T. [Department of Mathematics, Quaid-I-Azam University 45320, Islamabad 44000 (Pakistan); Nonlinear Analysis and Applied Mathematics (NAAM) Research Group, Faculty of Science, King Abdulaziz University, P. O. Box 80257, Jeddah 21589 (Saudi Arabia); Alsaedi, A. [Nonlinear Analysis and Applied Mathematics (NAAM) Research Group, Faculty of Science, King Abdulaziz University, P. O. Box 80257, Jeddah 21589 (Saudi Arabia)
2016-02-01
This article investigates the convective heat and mass conditions in three-dimensional flow of an Oldroyd-B nanofluid. The stretched flow is electrically conducting in the presence of an applied magnetic field. Thermal radiation effects are accounted in the energy equation. The governing nonlinear problems are computed for the convergent approximate solutions. Influences of different parameters on the dimensionless temperature and nanoparticle concentration fields are shown and examined. Quantities of physical interest namely local Nusselt and Sherwood numbers are computed and analyzed numerically. Comparison in a limiting case is made with the previous published result and an excellent agreement is noted. - Highlights: • Impact of magnetic field in three-dimensional flow is investigated. • Thermal radiation effects are accounted in the energy equation. • Convective type conditions of temperature and concentration are imposed. • The governing nonlinear problems are computed for the convergent approximate solutions. • Influences of different parameters are shown and examined.
Keslerová, Radka; Trdlička, David
2015-09-01
This work deals with the numerical modelling of steady flows of incompressible viscous and viscoelastic fluids through the three dimensional channel with T-junction. The fundamental system of equations is the system of generalized Navier-Stokes equations for incompressible fluids. This system is based on the system of balance laws of mass and momentum for incompressible fluids. Two different mathematical models for the stress tensor are used for simulation of Newtonian and Oldroyd-B fluids flow. Numerical solution of the described models is based on cetral finite volume method using explicit Runge-Kutta time integration.
Tellez Alvarez, Jackson David; Redondo, Jose Manuel; Sanchez, Jesu Mary
2016-04-01
fresh water in order to form density interfaces. The Reynolds number can be reduced adding Glicerine the set of dimensionless parameters define different conditions of both numeric and small scale laboratory applied often in modeling environmental flows. Fields of velocity, density and their gradients are computed using advanced visualization [8 9]. Visualizations are performed by PIV, Particle tracking and shadowgraph. When convective heating and cooling takes place the patterns depend on the parameter space region of the initial conditions We also map the different transitions between two and three dimensional convection in an enclosure with several complex driven flows. The size of the water tank is of 0.2 x 0.2 x 0.1 m and the heat sources or sinks can be regulated both in power and sign [2-4]. The thermal convective driven flows are generated by Seebeck and Peltier effects in 4 wall extended positions of 0.05 x 0.05 cm each. The parameter range of convective cell array varies strongly with the Topology of the boundary conditions. At present side heat fluxes are considered and estimated as a function of Rayleigh, Peclet and Nusselt numbers, [4-6] The evolution of the mixing fronts are compared and the topological characteristics of the merging of plumes and jets in different configurations presenting detailed comparison of the evolution of RM and RT, Jets and Plumes in overall mixing. The relation between structure functions, fractal analysis and spectral analysis can be very useful to determine the evolution of scales. Experimental and numerical results on the advance of a mixing or non-mixing front occurring at a density interface due to body forces [12] can be compared with the convective fronts. The evolution of the turbulent mixing layer and its complex configuration is studied taking into account the dependence on the initial modes at the early stages, Self-similar information [13]. Spectral and Fractal analysis on the images seems very useful in order to
Suzuki, Kohei; Omori, Takesi; Kajishima, Takeo
2014-11-01
Although the advantage of using arbitrarily-shaped polyhedral meshes for the industrial flow applications is clear, their employment to two-phase flows is rather limited due to the poor prediction accuracy of the existing numerical methods on such meshes. We present a numerical method based on VOF (Volume of Fluid) method which works on arbitrarily-shaped three-dimensional polyhedral meshes with little volume/shape error for the interface advection and with little curvature estimation error. To make the implementation in three-dimensional geometry feasible, we extend THINC (Tangent of Hyperbola Interface Capturing) method for polyhedral meshes which does not require laborious geometric arithmetics. In the oral presentation we will also show that the combination of RDF (Reconstructed Distance Function) algorithm and the carefully selected discretization procedure gives good performance in the interface curvature estimation.
Directory of Open Access Journals (Sweden)
Khansa Rubab
Full Text Available 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.
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.
International Nuclear Information System (INIS)
Wong, C.N.C.; Cheng, S.K.; Todreas, N.E.
1982-01-01
This report provides the HEATRAN user with programming and input information. HEATRAN is a computer program which is written to analyze the transient three dimensional single phase incompressible fluid flow and heat transfer problem. In this report, the programming information is given first. This information includes details concerning the code and structure. The description of the required input variables is presented next. Following the input description, the sample problems are described and HEATRAN's results are presented
Directory of Open Access Journals (Sweden)
Saeed Dinarvand
2012-01-01
Full Text Available The steady three-dimensional flow of condensation or spraying on inclined spinning disk is studied analytically. The governing nonlinear equations and their associated boundary conditions are transformed into the system of nonlinear ordinary differential equations. The series solution of the problem is obtained by utilizing the homotopy perturbation method (HPM. The velocity and temperature profiles are shown and the influence of Prandtl number on the heat transfer and Nusselt number is discussed in detail. The validity of our solutions is verified by the numerical results. Unlike free surface flows on an incline, this through flow is highly affected by the spray rate and the rotation of the disk.
Quasiconservation laws for compressible three-dimensional Navier-Stokes flow.
Gibbon, J D; Holm, D D
2012-10-01
We formulate the quasi-Lagrangian fluid transport dynamics of mass density ρ and the projection q=ω·∇ρ of the vorticity ω onto the density gradient, as determined by the three-dimensional compressible Navier-Stokes equations for an ideal gas, although the results apply for an arbitrary equation of state. It turns out that the quasi-Lagrangian transport of q cannot cross a level set of ρ. That is, in this formulation, level sets of ρ (isopycnals) are impermeable to the transport of the projection q.
Bishop, A. R.
1994-01-01
This computer program calculates the flow field in the supersonic portion of a mixed-compression aircraft inlet at non-zero angle of attack. This approach is based on the method of characteristics for steady three-dimensional flow. The results of this program agree with those produced by the two-dimensional method of characteristics when axisymmetric flow fields are calculated. Except in regions of high viscous interaction and boundary layer removal, the results agree well with experimental data obtained for threedimensional flow fields. The flow field in a variety of axisymmetric mixed compression inlets can be calculated using this program. The bow shock wave and the internal shock wave system are calculated using a discrete shock wave fitting procedure. The internal flow field can be calculated either with or without the discrete fitting of the internal shock wave system. The influence of molecular transport can be included in the calculation of the external flow about the forebody and in the calculation of the internal flow when internal shock waves are not discretely fitted. The viscous and thermal diffussion effects are included by treating them as correction terms in the method of characteristics procedure. Dynamic viscosity is represented by Sutherland's law and thermal conductivity is represented as a quadratic function of temperature. The thermodynamic model used is that of a thermally and calorically perfect gas. The program assumes that the cowl lip is contained in a constant plane and that the centerbody contour and cowl contour are smooth and have continuous first partial derivatives. This program cannot calculate subsonic flow, the external flow field if the bow shock wave does not exist entirely around the forebody, or the internal flow field if the bow flow field is injected into the annulus. Input to the program consists of parameters to control execution, to define the geometry, and the vehicle orientation. Output consists of a list of parameters
DEFF Research Database (Denmark)
Park, Keunhwan; Tixier, A.; Christensen, A.H.
2018-01-01
experiments and theory on viscous flow in a simple bioinspired soft valve which illustrate essential features of interactions between hydrodynamic and elastic forces at low Reynolds numbers. The set-up comprises a sphere connected to a spring located inside a tapering cylindrical channel. The spring...... is aligned with the central axis of the channel and a pressure drop is applied across the sphere, thus forcing the liquid through the narrow gap between the sphere and the channel walls. The sphere's equilibrium position is determined by a balance between spring and hydrodynamic forces. Since the gap...... thickness h0, and viscosity η as Q ∼η-1 a1/2h05/2 (1 - Δp/Δpc)5/2Δp, where the critical pressure Δpc scales with spring constant k as Δpc ∼ kh0a-2. These predictions compared favourably to the results of our experiments with no free parameters....
International Nuclear Information System (INIS)
Bernard, J.P.; Haekkinen, J.; Sarkomaa, P.
1997-01-01
A number of numerical studies on three-dimensional flows in reactor vessels of nuclear power plants have been carried out recently. The main reason for this is the phenomenon of inherent boron dilution. These studies have been done for Loviisa nuclear power plant as well. This presentation focuses on the three dimensional modeling of Loviisa's lower plenum with the commercial CFX code. The investigations particularly deal with the modeling of the two perforated plates located at the bottom and just below the core of the vessel. The perforated plates can be modeled as porous media in the CFX code. The model has been validated against available experimental data. Velocity profiles around the plates, the pressure drop through the plates, and the simulation of mixing factors have been investigated specifically. (author)
Influence of viscous dissipation and radiation on MHD Couette flow ...
African Journals Online (AJOL)
The overall analysis of the study of these parameters in various degrees show an increase in the velocity profile of the fluid, while radiation parameter decreases the temperature profile; viscous dissipation and Reynolds number increase the temperature profile of the fluid. Key word: Couette flow, viscous dissipation, ...
Wang, Kai-Tong; Xing, Yanxia; Cheung, King Tai; Wang, Jian; Pan, Hui; Zhao, Hong-Kang
2017-10-01
We numerically study the focusing effect induced by a single p–n junction in three-dimensional topological insulators (3D TIs). It is found that, for either surface states or bulk states of 3D TIs, the corresponding electrons injected from the n/p region can be perfectly focused at the symmetric position in the p/n region. These results suggest that the focusing effect is a general phenomenon in materials which can be described by massless or massive Dirac equations. We also find that the focusing effect is robust against moderate random disorders. In the presence of external magnetic fields, the focusing effect remains good, but the position of the focus point oscillates periodically due to the finite size effect.
Statistics of highly heterogeneous flow fields confined to three-dimensional random porous media
Jin, C.; Langston, P. A.; Pavlovskaya, G. E.; Hall, M. R.; Rigby, S. P.
2016-01-01
We present a strong relationship between the microstructural characteristics of, and the fluid velocity fields confined to, three-dimensional random porous materials. The relationship is revealed through simultaneously extracting correlation functions Ru u(r ) of the spatial (Eulerian) velocity fields and microstructural two-point correlation functions S2(r ) of the random porous heterogeneous materials. This demonstrates that the effective physical transport properties depend on the characteristics of complex pore structure owing to the relationship between Ru u(r ) and S2(r ) revealed in this study. Further, the mean excess plot was used to investigate the right tail of the streamwise velocity component that was found to obey light-tail distributions. Based on the mean excess plot, a generalized Pareto distribution can be used to approximate the positive streamwise velocity distribution.
Energy Technology Data Exchange (ETDEWEB)
Hu, Rui
2017-09-03
Mixing, thermal-stratification, and mass transport phenomena in large pools or enclosures play major roles for the safety of reactor systems. Depending on the fidelity requirement and computational resources, various modeling methods, from the 0-D perfect mixing model to 3-D Computational Fluid Dynamics (CFD) models, are available. Each is associated with its own advantages and shortcomings. It is very desirable to develop an advanced and efficient thermal mixing and stratification modeling capability embedded in a modern system analysis code to improve the accuracy of reactor safety analyses and to reduce modeling uncertainties. An advanced system analysis tool, SAM, is being developed at Argonne National Laboratory for advanced non-LWR reactor safety analysis. While SAM is being developed as a system-level modeling and simulation tool, a reduced-order three-dimensional module is under development to model the multi-dimensional flow and thermal mixing and stratification in large enclosures of reactor systems. This paper provides an overview of the three-dimensional finite element flow model in SAM, including the governing equations, stabilization scheme, and solution methods. Additionally, several verification and validation tests are presented, including lid-driven cavity flow, natural convection inside a cavity, laminar flow in a channel of parallel plates. Based on the comparisons with the analytical solutions and experimental results, it is demonstrated that the developed 3-D fluid model can perform very well for a wide range of flow problems.
Rasskazov, Andrey; Chertovskih, Roman; Zheligovsky, Vladislav
2018-04-01
We introduce six families of three-dimensional space-periodic steady solenoidal flows, whose kinetic helicity density is zero at any point. Four families are analytically defined. Flows in four families have zero helicity spectrum. Sample flows from five families are used to demonstrate numerically that neither zero kinetic helicity density nor zero helicity spectrum prohibit generation of large-scale magnetic field by the two most prominent dynamo mechanisms: the magnetic α -effect and negative eddy diffusivity. Our computations also attest that such flows often generate small-scale field for sufficiently small magnetic molecular diffusivity. These findings indicate that kinetic helicity and helicity spectrum are not the quantities controlling the dynamo properties of a flow regardless of whether scale separation is present or not.
Yun, Keon-Young
For the computation of hypersonic flowfields about space vehicles in low earth orbits, where the local Knudsen numbers (Kn) lie in continuum-transition regime, a set of extended three-dimensional hydrodynamic equations are required which are more accurate than the Navier-Stokes equations and computationally more efficient than the Direct Simulation Monte Carlo (DSMC) computations in this regime. In this thesis, the three-dimensional augmented Burnett equations are derived from the Chapman-Enskog expansion of the Boltzmann equation to O(Kn 2) and adding the augmented terms (linear third-order super Burnett terms with coefficients determined from linearized stability analysis to ensure stability of the augmented Burnett equations to small wavelength disturbances). The three-dimensional augmented Burnett equations are applied to compute the three-dimensional hypersonic blunt body flows for various range of Knudsen numbers and Mach numbers. An explicit time-stepping scheme with Steger-Warming flux vector splitting is employed to discretize the convective flux terms. Stress and heat flux terms are central differenced. For the wall boundary conditions, the first-order Maxwell-Smoluchowski slip boundary conditions are employed. The computational results are compared with the Navier-Stokes solutions, the existing augmented Burnett solutions of Zhong, and the available DSMC results. The comparisons show that the difference between the Navier-Stokes and the augmented Burnett solutions is very small at Knudsen numbers less than 0.01; the difference becomes significant as the Knudsen number increases. The comparisons also show that the augmented Burnett solutions are much closer to the DSMC results in the continuum-transition regime than the Navier-Stokes calculations.
Kurt, Melike; Moored, Keith
2018-04-19
We present experiments that examine the modes of interaction, the collective performance and the role of three-dimensionality in two pitching propulsors in an in-line arrangement. Both two-dimensional foils and three-dimensional rectangular wings of $AR = 2$ are examined. \\kwm{In contrast to previous work, two interaction modes distinguished as the coherent and branched wake modes are not observed to be directly linked to the propulsive efficiency, although they are linked to peak thrust performance and minimum power consumption as previously described \\cite[]{boschitsch2014propulsive}.} \\kwm{In fact, in closely-spaced propulsors peak propulsive efficiency of the follower occurs near its minimum power and this condition \\kwm{ reveals a} branched wake mode. Alternatively, for propulsors spaced far apart peak propulsive efficiency of the follower occurs near its peak thrust and this condition \\kwm{reveals a} coherent wake mode.} By examining the collective performance, it is discovered that there is an optimal spacing between the propulsors to maximize the collective efficiency. For two-dimensional foils the optimal spacing of $X^* = 0.75$ and the synchrony of $\\phi = 2\\pi /3$ leads to a collective efficiency and thrust enhancement of 50\\% and 32\\%, respectively, as compared to two isolated foils. In comparison, for $AR = 2$ wings the optimal spacing of $X^* = 0.25$ and the synchrony of $\\phi = 7\\pi /6$ leads to a collective efficiency and thrust enhancement of 30\\% and 22\\%, respectively. In addition, at the optimal conditions the collective lateral force coefficients in both the two- and three-dimensional cases are negligible, while operating off these conditions can lead to non-negligible lateral forces. Finally, the peak efficiency of the collective and the follower are shown to have opposite trends with increasing spacing in two- and three-dimensional flows. This is correlated to the breakdown of the impinging vortex on the follower wing in three
Hayat, Tasawar; Aziz, Arsalan; Muhammad, Taseer; Alsaedi, Ahmed
2017-09-01
The present study elaborates three-dimensional flow of Williamson nanoliquid over a nonlinear stretchable surface. Fluid flow obeys Darcy–Forchheimer porous medium. A bidirectional nonlinear stretching surface generates the flow. Convective surface condition of heat transfer is taken into consideration. Further the zero nanoparticles mass flux condition is imposed at the boundary. Effects of thermophoresis and Brownian diffusion are considered. Assumption of boundary layer has been employed in the problem formulation. Convergent series solutions for the nonlinear governing system are established through the optimal homotopy analysis method (OHAM). Graphs have been sketched in order to analyze that how the velocity, temperature and concentration distributions are affected by distinct emerging flow parameters. Skin friction coefficients and local Nusselt number are also computed and discussed.
Takenaka, N; Fujii, T; Mizubata, M; Yoshii, K
1999-01-01
Three-dimensional void fraction distribution of air-water two-phase flow in a 4x4 rod-bundle near a spacer was visualized by fast neutron radiography using a CT method. One-dimensional cross sectional averaged void fraction distribution was also calculated. The behaviors of low void fraction (thick water) two-phase flow in the rod bundle around the spacer were clearly visualized. It was shown that the void fraction distributions were visualized with a quality similar to those by thermal neutron radiography for low void fraction two-phase flow which is difficult to visualize by thermal neutron radiography. It is concluded that the fast neutron radiography is efficiently applicable to two-phase flow studies.
Experimental investigation of three-dimensional flow structures in annular swirling jets
Percin, M.; Vanierschot, M.; Van Oudheusden, B.W.
2015-01-01
Annular jet flows are of practical interest in view of their occurrence in many industrial applications in the context of bluff-body combustors [1]. They feature different complex flow characteristics despite their simple geometry: a central recirculation zone (CRZ) as a result of flow separation
Three-dimensional calculation of the flow in the cold plenum of the Fast Breeder Reactor 1500 MW
International Nuclear Information System (INIS)
Chabard, J.P.; Daubert, O.; Gregoire, J.P.; Hemmerich, P.
1987-01-01
To solve thermalhydraulics problems which are rising for example on the various parts of nuclear reactors, several departments of the Direction des Etudes et Recherches are developing the N3S code, three-dimensional code using the finite element method. First, this paper presents the basic equations (Navies-Stokes with turbulence modelling and coupled with the thermal equation) and well suited algorithms to solve them. The industrial adequacy of the code is clearly demonstrated through the application to the computation of the flow in the cold plenum of the Fast Breeder Reactor 1500 MW on a mesh of about 20000 velocity nodes [fr
Directory of Open Access Journals (Sweden)
Tasawar Hayat
Full Text Available Here three dimensional (3D flow of second grade fluid has been studied in the presence of CattaneoâChristov double diffusion and heterogeneous-homogeneous reactions. Flow is bounded by a bidirectional linear stretchable surface. Generalized versions of Fourierâs and Fickâs law through CattaneoâChristov double diffusion are employed. Equal diffusion coefficients are considered for both autocatalyst and reactants. The conversion of partial differential system to nonlinear ordinary differential system has been done by employing appropriate transformations. The obtained nonlinear systems have been solved through the optimal homotopy analysis method (OHAM. Graphs have been displayed in order to examine how the velocities, temperature and concentration fields are affected by various pertinent parameters. Moreover the skin friction coefficients and heat and mass transfer rates have been computed and analyzed. Keywords: Three-dimensional flow, Second grade fluid, CattaneoâChristov double diffusion, Homogenous-heterogeneous reactions, OHAM
Directory of Open Access Journals (Sweden)
Jean-Paul Kone
2017-03-01
Full Text Available A review of published three-dimensional, computational fluid dynamics models for proton exchange membrane fuel cells that accounts for multiphase flow is presented. The models can be categorized as models for transport phenomena, geometry or operating condition effects, and thermal effects. The influences of heat and water management on the fuel cell performance have been repeatedly addressed, and these still remain two central issues in proton exchange membrane fuel cell technology. The strengths and weaknesses of the models, the modelling assumptions, and the model validation are discussed. The salient numerical features of the models are examined, and an overview of the most commonly used computational fluid dynamic codes for the numerical modelling of proton exchange membrane fuel cells is given. Comprehensive three-dimensional multiphase flow computational fluid dynamic models accounting for the major transport phenomena inside a complete cell have been developed. However, it has been noted that more research is required to develop models that include among other things, the detailed composition and structure of the catalyst layers, the effects of water droplets movement in the gas flow channels, the consideration of phase change in both the anode and the cathode sides of the fuel cell, and dissolved water transport.
Three dimensional flow field at confluent fixed-bed open channels
Schleiss, Anton; De Cesare, Giovanni; Franca, Mário J.; Pfister, Michael; Birjukova, Olga; Guillén Ludeña, Sebastián; Alegria, Francisco; Cardoso, Antonio H.
2014-01-01
River confluences are known for their marked 3D patterns and, due to the complexity of local flow features and bed morphology, they require particular consideration. Although there are studies on the flow structure in junctions of two streams, amore detailed description of the flow patterns is still required. The objective of this work is to contribute to such description at river confluence for concordant bed, where both main and tributary channel beds have the same elevation. For that purpo...
Mao, Xiaole; Nawaz, Ahmad Ahsan; Lin, Sz-Chin Steven; Lapsley, Michael Ian; Zhao, Yanhui; McCoy, J. Philip; El-Deiry, Wafik S.; Huang, Tony Jun
2012-01-01
In this work, we demonstrate an integrated, single-layer, miniature flow cytometry device that is capable of multi-parametric particle analysis. The device integrates both particle focusing and detection components on-chip, including a “microfluidic drifting” based three-dimensional (3D) hydrodynamic focusing component and a series of optical fibers integrated into the microfluidic architecture to facilitate on-chip detection. With this design, multiple optical signals (i.e., forward scatter, side scatter, and fluorescence) from individual particles can be simultaneously detected. Experimental results indicate that the performance of our flow cytometry chip is comparable to its bulky, expensive desktop counterpart. The integration of on-chip 3D particle focusing with on-chip multi-parametric optical detection in a single-layer, mass-producible microfluidic device presents a major step towards low-cost flow cytometry chips for point-of-care clinical diagnostics. PMID:22567082
International Nuclear Information System (INIS)
Yoon, Sang Youl; Kim, Kyung Chun
2003-01-01
The three-dimensional spatial structures of impeller flow created by a six bladed Rushton turbine have identified based on the volumetric velocity information from multi-plane stereoscopic PIV measurements. A total of 10 planes with 2 mm space and a 50 mm by 64 mm size of the field of view were targeted. To reduce the depth of focus, we adopted an angle offset configuration which satisfied the Scheimpflug condition. The distortion compensation procedure was utilized during the in situ calibration. Phase-locked instantaneous data were ensemble averaged and interpolated in order to obtain mean 3-D, volumetric velocity fields on a 60 degree sector of a cylindrical ring volume enclosing the turbine blade. Using the equi-vorticity surface rendering, the spatial structure of the trailing vortices was clearly demonstrated. Detail flow characteristics of the radial jet reported in previous studies of mixer flows were easily identified
He, Liping; Lu, Gang; Chen, Dachuan; Li, Wenjun; Lu, Chunsheng
2017-07-01
This paper investigates the three-dimensional (3D) injection molding flow of short fiber-reinforced polymer composites using a smoothed particle hydrodynamics (SPH) simulation method. The polymer melt was modeled as a power law fluid and the fibers were considered as rigid cylindrical bodies. The filling details and fiber orientation in the injection-molding process were studied. The results indicated that the SPH method could effectively predict the order of filling, fiber accumulation, and heterogeneous distribution of fibers. The SPH simulation also showed that fibers were mainly aligned to the flow direction in the skin layer and inclined to the flow direction in the core layer. Additionally, the fiber-orientation state in the simulation was quantitatively analyzed and found to be consistent with the results calculated by conventional tensor methods.
Sikarwar, Nidhi
multiple experiments or numerical simulations. Alternatively an inverse design method can be used. An adjoint optimization method can be used to achieve the optimum blowing rate. It is shown that the method works for both geometry optimization and active control of the flow in order to deflect the flow in desirable ways. An adjoint optimization method is described. It is used to determine the blowing distribution in the diverging section of a convergent-divergent nozzle that gives a desired pressure distribution in the nozzle. Both the direct and adjoint problems and their associated boundary conditions are developed. The adjoint method is used to determine the blowing distribution required to minimize the shock strength in the nozzle to achieve a known target pressure and to achieve close to an ideally expanded flow pressure. A multi-block structured solver is developed to calculate the flow solution and associated adjoint variables. Two and three-dimensional calculations are performed for internal and external of the nozzle domains. A two step MacCormack scheme based on predictor- corrector technique is was used for some calculations. The four and five stage Runge-Kutta schemes are also used to artificially march in time. A modified Runge-Kutta scheme is used to accelerate the convergence to a steady state. Second order artificial dissipation has been added to stabilize the calculations. The steepest decent method has been used for the optimization of the blowing velocity after the gradients of the cost function with respect to the blowing velocity are calculated using adjoint method. Several examples are given of the optimization of blowing using the adjoint method.
International Nuclear Information System (INIS)
Costa, Gustavo Koury
2004-11-01
Although incompressible fluid flows can be regarded as a particular case of a general problem, numerical methods and the mathematical formulation aimed to solve compressible and incompressible flows have their own peculiarities, in such a way, that it is generally not possible to attain both regimes with a single approach. In this work, we start from a typically compressible formulation, slightly modified to make use of pressure variables and, through augmenting the stabilising parameters, we end up with a simplified model which is able to deal with a wide range of flow regimes, from supersonic to low speed gas flows. The resulting methodology is flexible enough to allow for the simulation of liquid flows as well. Examples using conservative and pressure variables are shown and the results are compared to those published in the literature, in order to validate the method. (author)
Energy Technology Data Exchange (ETDEWEB)
Carrington, David Bradley [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Monayem, A. K. M. [Univ. of New Mexico, Albuquerque, NM (United States); Mazumder, H. [Univ. of New Mexico, Albuquerque, NM (United States); Heinrich, Juan C. [Univ. of New Mexico, Albuquerque, NM (United States)
2015-03-05
A three-dimensional finite element method for the numerical simulations of fluid flow in domains containing moving rigid objects or boundaries is developed. The method falls into the general category of Arbitrary Lagrangian Eulerian methods; it is based on a fixed mesh that is locally adapted in the immediate vicinity of the moving interfaces and reverts to its original shape once the moving interfaces go past the elements. The moving interfaces are defined by separate sets of marker points so that the global mesh is independent of interface movement and the possibility of mesh entanglement is eliminated. The results is a fully robust formulation capable of calculating on domains of complex geometry with moving boundaries or devises that can also have a complex geometry without danger of the mesh becoming unsuitable due to its continuous deformation thus eliminating the need for repeated re-meshing and interpolation. Moreover, the boundary conditions on the interfaces are imposed exactly. This work is intended to support the internal combustion engines simulator KIVA developed at Los Alamos National Laboratories. The model's capabilities are illustrated through application to incompressible flows in different geometrical settings that show the robustness and flexibility of the technique to perform simulations involving moving boundaries in a three-dimensional domain.
Mushtaq, Ammar; Mustafa, Meraj; Hayat, Tasawar; Alsaedi, Ahmed
2014-12-01
The steady laminar three-dimensional magnetohydrodynamic (MHD) boundary layer flow and heat transfer over a stretching sheet is investigated. The sheet is linearly stretched in two lateral directions. Heat transfer analysis is performed by utilizing a nonlinear radiative heat flux in Rosseland approximation for thermal radiation. Two different wall conditions, namely (i) constant wall temperature and (ii) prescribed surface temperature are considered. The developed nonlinear boundary value problems (BVPs) are solved numerically through fifth-order Runge-Kutta method using a shooting technique. To ascertain the accuracy of results the solutions are also computed by using built in function bvp4c of MATLAB. The behaviours of interesting parameters are carefully analyzed through graphs for velocity and temperature distributions. The dimensionless expressions of wall shear stress and heat transfer rate at the sheet are evaluated and discussed. It is seen that a point of inflection of the temperature function exists for sufficiently large values of wall to ambient temperature ratio. The solutions are in excellent agreement with the previous studies in a limiting sense. To our knowledge, the novel idea of nonlinear thermal radiation in three-dimensional flow is just introduced here.
Three-Dimensional Unsteady Flow Elicited by Finite Wings and Complex Configurations.
1987-01-01
flow. Anemometric measurements added quantitative magnitudes and spatial verification to the visualized flow structures. The experiments were designed... anemometric measurements were taken at each span location and chordwise at 0.00c(leading edge), 0.17c, 0.33c, 0.50c, 0.67c, 0.83c and 1.00c. " An X...The hot wire recorded the absolute velocity of the flow field during the cyclic motion history of the three wings. The anemometric measurements were
Three dimensional numerical simulation for air flow field in melt blowing
Xie, Sheng; Han, Wanli; Jiang, Guojun
2017-10-01
Melt blowing is one-step approach for producing microfibrous nonwovens. In this study, the characteristics of air flow field in different die melt blowing were studied. CFD simulation analysis was adopted to complete the air flow field simulation. The characteristics of the air flow fields in different die melt blowing were revealed and compared. Meanwhile, the fiber paths in these two melt-blowing processes are recorded with a high-speed camera. The fiber path profiles, especially the whipping, are obtained and presented.
Akutsu, Toshinosuke; Matsumoto, Akira
2010-12-01
The current design of the bileaflet valve, the leaflets of which open outside first, differs significantly from the natural valve whose leaflets open center first. This difference generates a completely different flow field in the bileaflet valve compared to that in the natural heart valve. In a previous study, it was demonstrated that the valve design greatly affects the aortic flow field as well as the circulatory flow inside sinuses of Valsalva, using saline solution as a working fluid. A limited discussion on the turbulence flow field that could be generated by the valve was provided. In this continuation of that study, therefore, a dynamic PIV study was conducted to analyze the influence of the heart valve design on the aortic flow field, and particularly on the turbulent profile. This study also aimed to determine the influence of the viscosity of the testing fluid. Three bileaflet prostheses-the St. Jude Medical (SJM), the On-X, and the MIRA valves-were tested under pulsatile flow conditions. Flow through the central orifice of the SJM valve was slower than that through the newer designs. The newer designs tend to show strong flow through all orifices. The On-X valve generates simple jet-type flow while the MIRA valve with circumferentially curved leaflets generates a strong but three-dimensionally diffuse flow, resulting in a more complex flow field downstream of the aortic valve with higher turbulence. A 180° orientation that is more popular clinically seems to provide a less diffuse flow than a 90° orientation. The effect of increasing the viscosity was found to be an increase in the flow velocity through the central orifice and a more organized flow field for all of the valves tested.
Three-Dimensional Subsurface Flow, Fate and Transport of Microbes and Chemicals (3DFATMIC) Model
This model simulates subsurface flow, fate and transport of contaminants that are undergoing chemical or biological transformations. The model is applicable to transient conditions in both saturated and unsaturated zones.
Directory of Open Access Journals (Sweden)
A.M. Rashad
2017-04-01
Full Text Available The present study explores the impact of anistropic slip on transient three dimensional MHD flow of Cobalt-kerosene ferrofluid over an inclined radiate stretching surface. The governing partial differential equations for this study are solved by the Thomas algorithm with finite-difference type. The impacts of several significant parameters on flow and heat transfer characteristics are exhibited graphically. The conclusion is revealed that the local Nusselt number is significantly promoted due to influence of thermal radiation whereas diminished with elevating the solid volume fraction, magnet parameter and slip factors. Further, the skin friction coefficients visualizes a considerable enhancement with boosting the magnet and radiation parameters, but a prominent reduction is recorded by elevating the solid volume fraction and slip factors.
Directory of Open Access Journals (Sweden)
Alexandr Kоshev
2014-12-01
Full Text Available The mathematical model of electrochemical processes distribution within the three-dimensional flow-through electrode for the system Fe(III/Fe(II/Fe is described in this paper, considering also the electrochemical reactions of hydrogen and molecular oxygen reduction. Possible dynamic changes in the parameters of electrode, electrolyte and the process are taken into account in the mathematical model, such as electro-conductivity of electrode material, electrolyte flow rate, material porosity and specific electrode surface, concentrations of electro-active substances and other characteristics within the local volume of electrode. Electrode and process characteristics are treated as time and coordinate functions within the electrode volume. The results of calculations and experimental studies of iron electro-reduction are given, the analysis of the numerical modeling is provided.
Hathaway, Michael D.; Chriss, Randall M.; Strazisar, Anthony J.; Wood, Jerry R.
1995-01-01
A laser anemometer system was used to provide detailed surveys of the three-dimensional velocity field within the NASA low-speed centrifugal impeller operating with a vaneless diffuser. Both laser anemometer and aerodynamic performance data were acquired at the design flow rate and at a lower flow rate. Floor path coordinates, detailed blade geometry, and pneumatic probe survey results are presented in tabular form. The laser anemometer data are presented in the form of pitchwise distributions of axial, radial, and relative tangential velocity on blade-to-blade stream surfaces at 5-percent-of-span increments, starting at 95-percent-of-span from the hub. The laser anemometer data are also presented as contour and wire-frame plots of throughflow velocity and vector plots of secondary velocities at all measurement stations through the impeller.
Study of Flow Deformation around Wind-Vane Mounted Three-Dimensional Hot-Wire Probes
DEFF Research Database (Denmark)
Rømer Rasmussen, K.; Larsen, Søren Ejling; Jørgensen, F. E.
1981-01-01
Open wind tunnel tests on several different sensor systems consisting of triaxial hot-wire probes mounted on wind vanes (DISA and Riso vanes) have shown that flow deformation around the hot-wire sensor introduces errors in the measured velocity components. Though changes in the horizontal...... components proved to be negligible, flow deformation resulted in an overestimation of the vertical component from 1.1 to 1.5, depending on the direction of the vertical component. Turbulence and mean value data were adjusted by use of a linear correction derived from the wind tunnel tests. Wind vane...... construction must strike a compromise between minor flow disturbance and sufficient probe support. The final version of the DISA vane resulted in an acceptable vertical correction of about 10%....
Numerical simulation analysis of three dimensional flow field in the lower plenum of CNP1000
International Nuclear Information System (INIS)
Liu Changwen; Jiang Xiaohua; Chen Weihong
2004-01-01
China National Nuclear Corporation (CNNC) proposed the CNP1000 design for Chinese market, which is a 1000MWe class nuclear power plant with three loops, in order to meet the electric power requirements of China and to fit the Chinese nuclear power development plan. This design, in which the number of fuel assembly is reasonably increased to 177 to lower the linear power density, has the characteristics of high safety and better economy. Comparing with the typical three-loop 1000MWe class nuclear power plant with 157 fuel assemblies, the reactor internals has been redesigned due to increasing of core diameter. NPIC has performed the hydraulic simulation test in order to validate the reactor internals design and analyze the reactor hydraulic characteristics. The aims of this paper are to analyze the effect of the new reactor internals design on the reactor thermal-hydraulic characteristics, particularly the flow distribution of the lower plenum and the core inlet flow distribution. The hydraulic tests were usually used to investigate the flow-rate distribution and flow resistance in the core. But the experimental periods were so long and the experiments were too expensive, especially for optimizing schemes. Along with the development of computer, computational fluid dynamics (CFD) became one kind of powerful means for research and engineering design. The flow distribution and pressure drop of the lower core plate can be obtained by numerical simulation of the 3-D flow field in the lower plenum. Through the comparison with the experiment data, not only the reactor internals design can be validated, but also the thermal hydraulic characteristics of the flow in the reactor vessel can be analyzed in detail. Computational fluid dynamics is the combination of neoteric hydrodynamics, numerical mathematics and computer science. It is a fringe subject with powerful vitality. CFD uses computer and discretization method to simulate the practical hydrodynamic problem. There are
Directory of Open Access Journals (Sweden)
Wei Fan
2016-01-01
Full Text Available Transmission loss (TL is often used to evaluate the acoustic attenuation performance of a silencer. In this work, a three-dimensional (3D finite element method (FEM is employed to calculate the TL of some representative silencers, namely, circular expansion chamber silencer and straight-through perforated pipe silencer. In order to account for the effect of mean flow that exists inside the silencer, the 3D FEM is used in conjunction with the Computational Fluid Dynamics (CFD simulation of the flow field. More concretely, the 3D mean flow field is computed by firstly using CFD, and then the obtained mean flow data are imported to an acoustic solution undertaken using FEM. The data transfer between the two steps is accomplished by mesh mapping. The results presented demonstrate good agreement between present TL predictions and previously published experimental and numerical works. Also, the details of the flow inside the silencers may be studied. Furthermore, the effect of mean flow velocity on acoustic attenuation performance of the silencers is investigated. It is concluded that for the studied silencers, in general, increasing flow velocity increases the TL and decreases the resonance peaks.
International Nuclear Information System (INIS)
Kumamaru, Hiroshige
2003-01-01
A three-dimensional numerical calculation has been performed on liquid-metal magnetohydrodynamic (MHD) flow through a rectangular channel in the outlet region of the magnetic field, including a region downstream the magnetic field section. The continuity equation, the momentum equation and the induction equation have been solved numerically by the finite difference method. Along the flow axis (i.e. the channel axis), the pressure decreases rapidly as a fully-developed MHD flow, drops more rapidly in the magnetic-field outlet-region, and finally decreases slowly as a normal non-MHD flow. The pressure recovery that was observed in the magnetic-field inlet-region does not appear in the magnetic-field outlet-region. The total pressure drop through the magnetic-field outlet-region is larger than that through the magnetic-field inlet-region. The flow velocity distribution also changes gradually from a flat profile of a fully-developed MHD flow to a parabolic profile of a non-MHD laminar flow. (author)
Shear-induced particle migration in one-, two-, and three-dimensional flows
Gao, C.; Gilchrist, J. F.
2008-02-01
We investigate the segregation resulting from the competition between advection and shear-induced migration of suspensions in steady open flows. Herringbone channels form a concentration profile deviating from the particle focusing found in straight channels. Transients can result from a buckling instability during the onset of migration when particle-depleted fluid is injected into particle-rich fluid. In chaotic flows, the better mixing found at low bulk volume fraction is not seen at higher bulk volume fraction. Thus, the ability of static mixers to reduce the effects of shear-induced migration is significantly limited.
A comparison of upwind schemes for computation of three-dimensional hypersonic real-gas flows
Gerbsch, R. A.; Agarwal, R. K.
1992-01-01
The method of Suresh and Liou (1992) is extended, and the resulting explicit noniterative upwind finite-volume algorithm is applied to the integration of 3D parabolized Navier-Stokes equations to model 3D hypersonic real-gas flowfields. The solver is second-order accurate in the marching direction and employs flux-limiters to make the algorithm second-order accurate, with total variation diminishing in the cross-flow direction. The algorithm is used to compute hypersonic flow over a yawed cone and over the Ames All-Body Hypersonic Vehicle. The solutions obtained agree well with other computational results and with experimental data.
Ryan, Kevin J.; Coletti, Filippo; Elkins, Christopher J.; Dabiri, John O.; Eaton, John K.
2016-03-01
Three-dimensional, three-component mean velocity fields have been measured around and downstream of a scale model vertical axis wind turbine (VAWT) operated at tip speed ratios (TSRs) of 1.25 and 2.5, in addition to a non-rotating case. The five-bladed turbine model has an aspect ratio (height/diameter) of 1 and is operated in a water tunnel at a Reynolds number based on turbine diameter of 11,600. Velocity fields are acquired using magnetic resonance velocimetry (MRV) at an isotropic resolution of 1/50 of the turbine diameter. Mean flow reversal is observed immediately behind the turbine for cases with rotation. The turbine wake is highly three-dimensional and asymmetric throughout the investigated region, which extends up to 7 diameters downstream. A vortex pair, generated at the upwind-turning side of the turbine, plays a dominant role in wake dynamics by entraining faster fluid from the freestream and aiding in wake recovery. The higher TSR case shows a larger region of reverse flow and greater asymmetry in the near wake of the turbine, but faster wake recovery due to the increase in vortex pair strength with increasing TSR. The present measurement technique also provides detailed information about flow in the vicinity of the turbine blades and within the turbine rotor. The details of the flow field around VAWTs and in their wakes can inform the design of high-density VAWT wind farms, where wake interaction between turbines is a principal consideration.
International Nuclear Information System (INIS)
Bettencourt, João H; López, Cristóbal; Hernández-García, Emilio
2013-01-01
In this paper, we use the finite-size Lyapunov exponent (FSLE) to characterize Lagrangian coherent structures in three-dimensional (3D) turbulent flows. Lagrangian coherent structures act as the organizers of transport in fluid flows and are crucial to understand their stirring and mixing properties. Generalized maxima (ridges) of the FSLE fields are used to locate these coherent structures. 3D FSLE fields are calculated in two phenomenologically distinct turbulent flows: a wall-bounded flow (channel flow) and a regional oceanic flow obtained by the numerical solution of the primitive equations where two-dimensional (2D) turbulence dominates. In the channel flow, autocorrelations of the FSLE field show that the structure is substantially different from the near wall to the mid-channel region and relates well to the more widely studied Eulerian coherent structure of the turbulent channel flow. The ridges of the FSLE field have complex shapes due to the 3D character of the turbulent fluctuations. In the oceanic flow, strong horizontal stirring is present and the flow regime is similar to that of 2D turbulence where the domain is populated by coherent eddies that interact strongly. This in turn results in the presence of high FSLE lines throughout the domain leading to strong non-local mixing. The ridges of the FSLE field are quasi-vertical surfaces, indicating that the horizontal dynamics dominates the flow. Indeed, due to rotation and stratification, vertical motions in the ocean are much less intense than horizontal ones. This suppression is absent in the channel flow, as the 3D character of the FSLE ridges shows. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Lyapunov analysis: from dynamical systems theory to applications’. (paper)
Development of a Three-Dimensional Unstructured Euler Solver for High-Speed Flows
Directory of Open Access Journals (Sweden)
Tudorel Petronel AFILIPOAE
2015-12-01
Full Text Available This paper addresses the solution of the compressible Euler equations on hexahedral meshes for supersonic and hypersonic flows. Spatial discretization is accomplished by a cell-centered finite-volume formulation which employs two different upwind schemes for the computation of convective fluxes. Second-order solutions are attained through a linear state reconstruction technique that yields highly resolved flows in smooth regions while providing a sharp and clean resolution of shocks. The solution gradients required for the higher-order spatial discretization are estimated by a least-square method while Venkatakrishnan limiter is employed to preserve monotonicity and avoid oscillations in the presence of shocks. Furthermore, solutions are advanced in time by an explicit third-order Runge-Kutta scheme and convergence to steady state is accelerated using implicit residual smoothing. Flow around a circular arc in a channel and flow past a circular cylinder are studied and results are presented for various Mach numbers together with comparisons to theoretical and experimental data where possible.
Three-dimensional flow and load characteristics of flexible revolving wings at low Reynolds number
van de Meerendonk, R.; Perçin, M.; van Oudheusden, B.W.
2016-01-01
This study explores the flow field and fluid-dynamic loads generated by revolving low-aspect-ratio flat plate wings undergoing a revolving motion starting from rest. Three wings with different degree of chordwise flexural stiffness (i.e., rigid, moderate flexibility and high flexibility) have been
The Three-Dimensional Velocity Distribution of Wide Gap Taylor-Couette Flow Modelled by CFD
Directory of Open Access Journals (Sweden)
David Shina Adebayo
2016-01-01
Full Text Available A numerical investigation is conducted for the flow between two concentric cylinders with a wide gap, relevant to bearing chamber applications. This wide gap configuration has received comparatively less attention than narrow gap journal bearing type geometries. The flow in the gap between an inner rotating cylinder and an outer stationary cylinder has been modelled as an incompressible flow using an implicit finite volume RANS scheme with the realisable k-ε model. The model flow is above the critical Taylor number at which axisymmetric counterrotating Taylor vortices are formed. The tangential velocity profiles at all axial locations are different from typical journal bearing applications, where the velocity profiles are quasilinear. The predicted results led to two significant findings of impact in rotating machinery operations. Firstly, the axial variation of the tangential velocity gradient induces an axially varying shear stress, resulting in local bands of enhanced work input to the working fluid. This is likely to cause unwanted heat transfer on the surface in high torque turbomachinery applications. Secondly, the radial inflow at the axial end-wall boundaries is likely to promote the transport of debris to the junction between the end-collar and the rotating cylinder, causing the build-up of fouling in the seal.
A three-dimensional dynamical model for channeled lava flow with nonlinear rheology
Filippucci, Marilena; Tallarico, Andrea; Dragoni, Michele
2010-05-01
Recent laboratory studies on the rheology of lava samples from different volcanic areas have highlighted that the apparent viscosity depends on a power of the strain rate. Several authors agree in attributing this dependence to the crystal content of the sample and to temperature. Starting from these results, in this paper we studied the effect of a power law rheology on a gravity-driven lava flow. The equation of motion is nonlinear in the diffusion term, and an analytical solution does not seem to be possible. The finite-volume method has been applied to solve numerically the equation governing the fully developed laminar flow of a power law non-Newtonian fluid in an inclined rectangular channel. The convergence, the stability, and the order of approximation were tested for the Newtonian rheology case, comparing the numerical solution with the available analytical solution. Results indicate that the assumption on the rheology, whether linear or nonlinear, strongly affects the velocity and/or the thickness of the lava channel both for channels with fixed geometry and for channels with constant flow rate. Results on channels with fixed geometry are confirmed by some simulations for real lava channels. Finally, the study of the Reynolds number indicates that gravity-driven lava channel flows are always in laminar regime, except for strongly nonlinear pseudoplastic fluids with low fluid consistency and at high slopes.
Mao, X.; Prommer, H.; Barry, D.A.; Langevin, C.D.; Panteleit, B.; Li, L.
2006-01-01
PHWAT is a new model that couples a geochemical reaction model (PHREEQC-2) with a density-dependent groundwater flow and solute transport model (SEAWAT) using the split-operator approach. PHWAT was developed to simulate multi-component reactive transport in variable density groundwater flow. Fluid density in PHWAT depends not on only the concentration of a single species as in SEAWAT, but also the concentrations of other dissolved chemicals that can be subject to reactive processes. Simulation results of PHWAT and PHREEQC-2 were compared in their predictions of effluent concentration from a column experiment. Both models produced identical results, showing that PHWAT has correctly coupled the sub-packages. PHWAT was then applied to the simulation of a tank experiment in which seawater intrusion was accompanied by cation exchange. The density dependence of the intrusion and the snow-plough effect in the breakthrough curves were reflected in the model simulations, which were in good agreement with the measured breakthrough data. Comparison simulations that, in turn, excluded density effects and reactions allowed us to quantify the marked effect of ignoring these processes. Next, we explored numerical issues involved in the practical application of PHWAT using the example of a dense plume flowing into a tank containing fresh water. It was shown that PHWAT could model physically unstable flow and that numerical instabilities were suppressed. Physical instability developed in the model in accordance with the increase of the modified Rayleigh number for density-dependent flow, in agreement with previous research. ?? 2004 Elsevier Ltd. All rights reserved.
Morphology and Three-Dimensional Inhalation Flow in Human Airways in Healthy and Diseased Subjects
Van de Moortele, Tristan
We investigate experimentally the relation between anatomical structure and respiratory function in healthy and diseased airways. Computed Tomography (CT) scans of human lungs are analyzed from the data base of a large multi-institution clinical study on Chronic Obstructive Pulmonary Disease (COPD). Through segmentation, the 3D volumes of the airways are determined at total lung capacity. A geometric analysis provides data on the morphometry of the airways, including the length and diameter of branches, the child-to-parent diameter ratio, and branching angles. While several geometric parameters are confirmed to match past studies for healthy subjects, previously unreported trends are reported on the length of branches. Specifically, in most dichotomous airway bifurcation, the branch of smaller diameter tends to be significantly longer than the one of larger diameter. Additionally, the branch diameter tends to be smaller in diseased airways than in healthy airways up to the 7th generation of bronchial branching. 3D fractal analysis is also performed on the airway volume. Fractal dimensions of 1.89 and 1.83 are found for healthy non-smokers and declining COPD subjects, respectively, furthering the belief that COPD (and lung disease in general) significantly affects the morphometry of the airways already in early stages of the disease. To investigate the inspiratory flow, 3D flow models of the airways are generated using Computer Aided Design (CAD) software and 3D printed. Using Magnetic Resonance Velocimetry (MRV), 3-component 3D flow fields are acquired for steady inhalation at Reynolds number Re 2000 defined at the trachea. Analysis of the flow data reveals that diseased subjects may experience greater secondary flow strength in their conducting airways, especially in deeper generations.
Forte, A.M.; Woodward, R.L.
1997-01-01
Joint inversions of seismic and geodynamic data are carried out in which we simultaneously constrain global-scale seismic heterogeneity in the mantle as well as the amplitude of vertical mantle flow across the 670 km seismic discontinuity. These inversions reveal the existence of a family of three-dimensional (3-D) mantle models that satisfy the data while at the same time yielding predictions of layered mantle flow. The new 3-D mantle models we obtain demonstrate that the buoyancy forces due to the undulations of the 670 km phase-change boundary strongly inhibit the vertical flow between the upper and lower mantle. The strong stabilizing effect of the 670 km topography also has an important impact on the predicted dynamic topography of the Earth's solid surface and on the surface gravity anomalies. The new 3-D models that predict strongly or partially layered mantle flow provide essentially identical fits to the global seismic data as previous models that have, until now, predicted only whole-mantle flow. The convective vertical transport of heat across the mantle predicted on the basis of the new 3-D models shows that the heat flow is a minimum at 1000 km depth. This suggests the presence at this depth of a globally defined horizon across which the pattern of lateral heterogeneity changes rapidly. Copyright 1997 by the American Geophysical Union.
Algabri, Y. A.; Rookkapan, S.; Chatpun, S.
2017-09-01
An abdominal aortic aneurysm (AAA) is considered a deadly cardiovascular disease that defined as a focal dilation of blood artery. The healthy aorta size is between 15 and 24 mm based on gender, bodyweight, and age. When the diameter increased to 30 mm or more, the rupture can occur if it is kept growing or untreated. Moreover, the proximal angular neck of aneurysm is categorized as a significant morphological feature with prime harmful effects on endovascular aneurysm repair (EVAR). Flow pattern in pathological vessel can influence the vascular intervention. The aim of this study is to investigate the blood flow behaviours in angular neck abdominal aortic aneurysm with simulated geometry based on patient’s information using computational fluid dynamics (CFD). The 3D angular neck AAA models have been designed by using SolidWorks Software. Consequently, CFD tools are used for simulating these 3D models of angular neck AAA in ANSYS FLUENT Software. Eventually, based on the results, we summarized that the CFD techniques have shown high performance in explaining and investigating the flow patterns for angular neck abdominal aortic aneurysm.
Breburda, C. S.; Griffin, B. P.; Pu, M.; Rodriguez, L.; Cosgrove, D. M. 3rd; Thomas, J. D.
1998-01-01
OBJECTIVES: We sought to validate direct planimetry of mitral regurgitant orifice area from three-dimensional echocardiographic reconstructions. BACKGROUND: Regurgitant orifice area (ROA) is an important measure of the severity of mitral regurgitation (MR) that up to now has been calculated from hemodynamic data rather than measured directly. We hypothesized that improved spatial resolution of the mitral valve (MV) with three-dimensional (3D) echo might allow accurate planimetry of ROA. METHODS: We reconstructed the MV using 3D echo with 3 degrees rotational acquisitions (TomTec) using a transesophageal (TEE) multiplane probe in 15 patients undergoing MV repair (age 59 +/- 11 years). One observer reconstructed the prolapsing mitral leaflet in a left atrial plane parallel to the ROA and planimetered the two-dimensional (2D) projection of the maximal ROA. A second observer, blinded to the results of the first, calculated maximal ROA using the proximal convergence method defined as maximal flow rate (2pi(r2)va, where r is the radius of a color alias contour with velocity va) divided by regurgitant peak velocity (obtained by continuous wave [CW] Doppler) and corrected as necessary for proximal flow constraint. RESULTS: Maximal ROA was 0.79 +/- 0.39 (mean +/- SD) cm2 by 3D and 0.86 +/- 0.42 cm2 by proximal convergence (p = NS). Maximal ROA by 3D echo (y) was highly correlated with the corresponding flow measurement (x) (y = 0.87x + 0.03, r = 0.95, p proximal convergence measurements.
Lattice Boltzmann simulations of leukocyte rolling and deformation in a three-dimensional shear flow
Luo, Ye; Qi, Dewei; He, Guowei
2013-11-01
Lattice Boltzmann simulation is used to simulate the motion of a leukocyte in fluid. The cell membrane is built by lattice spring model. The interaction between the fluid flow and the solid surface is treated by immersed boundary method. Stochastic Monte Carlo method is used to deal with receptor/ligand interaction. It is shown that the model can correctly predict the characteristic ``stop-and-g'' motion of rolling leukocytes. Effects of cell deformation, shear rates, bonding force, microvilli distribution on rolling are studied and compared with experiments.
The three-dimensional flow in the chamber of a gas centrifuge with an installed obstacle
International Nuclear Information System (INIS)
Elsholz, E.
1977-01-01
The flow-field in a very fast rotating chamber under the presence of a stationarily installed obstacle is calculated numerically from the complete set of Navier-Stokes-equations. A special differential approximation applied, provides stable and non-oscillating solutions even within the region of very small Ekman-numbers. This type of approximation will be derived and its advantages are discussed. Finally, a numerical result is presented which includes strong radial density gradients and shows very clearly the compressible effects as well as the mechanism of vortex shedding generated by the obstacle. (orig.) [de
Three dimensional radiative flow of magnetite-nanofluid with homogeneous-heterogeneous reactions
Hayat, Tasawar; Rashid, Madiha; Alsaedi, Ahmed
2018-03-01
Present communication deals with the effects of homogeneous-heterogeneous reactions in flow of nanofluid by non-linear stretching sheet. Water based nanofluid containing magnetite nanoparticles is considered. Non-linear radiation and non-uniform heat sink/source effects are examined. Non-linear differential systems are computed by Optimal homotopy analysis method (OHAM). Convergent solutions of nonlinear systems are established. The optimal data of auxiliary variables is obtained. Impact of several non-dimensional parameters for velocity components, temperature and concentration fields are examined. Graphs are plotted for analysis of surface drag force and heat transfer rate.
Time-domain Green's Function Method for three-dimensional nonlinear subsonic flows
Tseng, K.; Morino, L.
1978-01-01
The Green's Function Method for linearized 3D unsteady potential flow (embedded in the computer code SOUSSA P) is extended to include the time-domain analysis as well as the nonlinear term retained in the transonic small disturbance equation. The differential-delay equations in time, as obtained by applying the Green's Function Method (in a generalized sense) and the finite-element technique to the transonic equation, are solved directly in the time domain. Comparisons are made with both linearized frequency-domain calculations and existing nonlinear results.
Existence of a secondary flow for a temperature dependent viscous ...
African Journals Online (AJOL)
We model a viscous fluid flowing between parallel plates. The viscosity depends on temperature. We investigate the properties of the velocity and we show that the temperature and velocity fields have two solutions. The existence of two velocity solutions is new. This means that there exist secondary flows. Journal of the ...
Unsteady Viscous Flow Past an Impulsively Started Porous Vertical ...
African Journals Online (AJOL)
This paper presents a new numerical approach for solving unsteady two dimensional boundary layer flow past an infinite vertical porous surface with the flow generated by Newtonian heating and impulsive motion in the presence of viscous dissipation and temperature dependent viscosity. The viscosity of the fluid under ...
Parametric analysis of three dimensional flow models applied to tidal energy sites in Scotland
Rahman, Anas; Venugopal, Vengatesan
2017-04-01
This paper presents a detailed parametric analysis on various input parameters of two different numerical models, namely Telemac3D and Delft3D, used for the simulation of tidal current flow at potential tidal energy sites in the Pentland Firth in Scotland. The motivation behind this work is to investigate the influence of the input parameters on the above 3D models, as the majority of past research has mainly focused on using the 2D depth-averaged flow models for this region. An extended description of the models setup, along with the utilised parameters is provided. The International Hydrographic Organisation (IHO) tidal gauges and Acoustic Doppler and Current Profiler (ADCP) measurements are used in calibrating model output to ensure the robustness of the models. Extensive parametric study on the impact of varying drag coefficients, roughness formulae and turbulence models has been investigated and reported. The results indicate that both Telemac3D and Delft3D models are able to produce excellent comparison against measured data; however, with Delft3D, the model parameters which provided higher correlation with the measured data, are found to be different from those reported in the previous literature, which could be attributed to the choice of boundary conditions and the mesh size.
International Nuclear Information System (INIS)
Li Ying; Zhou Wenxia; Zhang Jige; Wang Dezhong
2009-01-01
In order to achieve the level of self-design and domestic manufacture of the reactor coolant pump (nuclear main pump), the software FLUENT was used to simulate the three-dimensional flow through full passage of one nuclear main pump basing on RNG κ-ε turbulence model and SIMPLE algorithm. The distribution of pressure and velocity of the flow in the impeller's surface was analyzed in different working conditions. Moreover, the performance of the pump was predicted based on the simulation results. The results show that the distributions of pressure and velocity are reasonable in both the working and back face of the blade in the steady working condition. The pressure of the flow is increased from the inlet to the outlet of the pump, and shows the maximal value in the impeller region. Comparatively satisfactory efficiency and head value were obtained in the condition of the pump design. The shaft power of the nuclear main pump is gradually increased with the increase of the flow flux. These results are helpful in understanding the change of the internal flow field in the nuclear main pump, which is of some importance for the pre-exploration and theoretical research on the domestic manufacture of the nuclear main pump. (authors)
Roszelle, Breigh N; Deutsch, Steven; Manning, Keefe B
2010-02-01
In order to aid the ongoing concern of limited organ availability for pediatric heart transplants, Penn State has continued development of a pulsatile Pediatric Ventricular Assist Device (PVAD). Initial studies of the PVAD observed an increase in thrombus formation due to differences in flow field physics when compared to adult sized devices, which included a higher degree of three-dimensionality. This unique flow field brings into question the use of 2D planar particle image velocimetry (PIV) as a flow visualization technique, however the small size and high curvature of the PVAD make other tools such as stereoscopic PIV impractical. In order to test the reliability of the 2D results, we perform a pseudo-3D PIV study using planes both parallel and normal to the diaphragm employing a mock circulatory loop containing a viscoelastic fluid that mimics 40% hematocrit blood. We find that while the third component of velocity is extremely helpful to a physical understanding of the flow, particularly of the diastolic jet and the development of a desired rotational pattern, the flow data taken parallel to the diaphragm is sufficient to describe the wall shear rates, a critical aspect to the study of thrombosis and design of such pumps.
International Nuclear Information System (INIS)
Pandey, Pradeep; Nayak, A.K.; Vijayan, P.K.
2014-01-01
Three dimensional flow patterns appearing in geometries such as curved pipes and T-channel junctions have important applications and are attractive for research. Unlike the flow in a straight tube, fluid motion in a curved tube is not parallel to the axis of bend, owing to the presence of centrifugal effects. It is characterized by a secondary flow in a cross-sectional plane normal to the main flow. Consequently, secondary flow separation near the inner wall is observed in the developing region. The strength of the secondary flow is greatly influenced by the curvature ratio and in turn, a non-dimensional parameter called the Dean Number. Secondary flow increases flow resistance, resulting in a larger pressure drop along the bend. The location of the maximum axial velocity gets shifted towards the outer wall. Flow in a T-channel junction is also a configuration of great significance. The simulations of the present work show that flow at low Reynolds numbers (Re ≤ 115) is steady and symmetric. For low Reynolds numbers, flow in the downstream channel remains highly segregated about the centerline. The appearance of vortices in the T-channel junction does little to redistribute concentration when flow remains symmetric. With increasing Reynolds number, transition takes place towards asymmetric flow. The incoming flow field gets redistributed at the center-plane and the dividing streamline becomes increasingly distorted. The flow field is characterized by thin elongated fluid interfaces across which momentum diffusion takes place. Flow at higher Reynolds numbers (Re ≥ 250) becomes unsteady in which unstable stagnation stream traces move periodically leftward and rightward at top and bottom walls. Trajectories of mass-less particles show greater dwelling in the junction as compared to those of finite mass particle. The numerical simulation is carried out in the present work using ANUPRAVAHA, a general purpose CFD solver developed at IIT Kanpur in collaboration with
Multigrid methods for flow transition in three-dimensional boundary layers with surface roughness
Liu, Chaoqun; Liu, Zhining; Mccormick, Steve
1993-01-01
The efficient multilevel adaptive method has been successfully applied to perform direct numerical simulations (DNS) of flow transition in 3-D channels and 3-D boundary layers with 2-D and 3-D isolated and distributed roughness in a curvilinear coordinate system. A fourth-order finite difference technique on stretched and staggered grids, a fully-implicit time marching scheme, a semi-coarsening multigrid method associated with line distributive relaxation scheme, and an improved outflow boundary-condition treatment, which needs only a very short buffer domain to damp all order-one wave reflections, are developed. These approaches make the multigrid DNS code very accurate and efficient. This allows us not only to be able to do spatial DNS for the 3-D channel and flat plate at low computational costs, but also to do spatial DNS for transition in the 3-D boundary layer with 3-D single and multiple roughness elements, which would have extremely high computational costs with conventional methods. Numerical results show good agreement with the linear stability theory, the secondary instability theory, and a number of laboratory experiments. The contribution of isolated and distributed roughness to transition is analyzed.
Three-dimensional modeling of flow through fractured tuff at Fran Ridge
International Nuclear Information System (INIS)
Eaton, R.R.; Ho, C.K.; Glass, R.J.; Nicholl, M.J.; Arnold, B.W.
1996-01-01
Numerical studies have been made of an infiltration experiment at Fran Ridge using the TOUGH2 code to aid in the selection of computational models for performance assessment. The exercise investigates the capabilities of TOUGH2 to model transient flows through highly fractured tuff and provides a possible means of calibration. Two distinctly different conceptual models were used in the TOUGH2 code, the dual permeability model and the equivalent continuum model. The infiltration test modeled involved the infiltration of dyed ponded water for 36 minutes. The 205 gallon filtration of water observed in the experiment was subsequently modeled using measured Fran Ridge fracture frequencies, and a specified fracture aperture of 285 μm. The dual permeability formulation predicted considerable infiltration along the fracture network, which was in agreement with the experimental observations. As expected, minimal fracture penetration of the infiltrating water was calculated using the equivalent continuum model, thus demonstrating that this model is not appropriate for modeling the highly transient experiment. It is therefore recommended that the dual permeability model be given priority when computing high-flux infiltration for use in performance assessment studies
Three-dimensional modeling of flow through fractured tuff at Fran Ridge
International Nuclear Information System (INIS)
Eaton, R.R.; Ho, C.K.; Glass, RJ.; Nicholl, M.J.; Arnold, B.W.
1996-09-01
Numerical studies have been made of an infiltration experiment at Fran Ridge using the TOUGH2 code to aid in the selection of computational models for performance assessment. The exercise investigates the capabilities of TOUGH2 to model transient flows through highly fractured tuff and provides a possible means of calibration. Two distinctly different conceptual models were used in the TOUGH2 code, the dual permeability model and the equivalent continuum model. The infiltration test modeled involved the infiltration of dyed ponded water for 36 minutes. The 205 gallon infiltration of water observed in the experiment was subsequently modeled using measured Fran Ridge fracture frequencies, and a specified fracture aperture of 285 microm. The dual permeability formulation predicted considerable infiltration along the fracture network, which was in agreement with the experimental observations. As expected, al fracture penetration of the infiltrating water was calculated using the equivalent continuum model, thus demonstrating that this model is not appropriate for modeling the highly transient experiment. It is therefore recommended that the dual permeability model be given priority when computing high-flux infiltration for use in performance assessment studies
Three-Dimensional CFD Modeling of Transport Phenomena in a Cross-Flow Anode-Supported Planar SOFC
Directory of Open Access Journals (Sweden)
Zhonggang Zhang
2013-12-01
Full Text Available In this study, a three-dimensional computational fluid dynamics (CFD model is developed for an anode-supported planar SOFC from the Chinese Academy of Science Ningbo Institute of Material Technology and Engineering (NIMTE. The simulation results of the developed model are in good agreement with the experimental data obtained under the same conditions. With the simulation results, the distribution of temperature, flow velocity and the gas concentrations through the cell components and gas channels is presented and discussed. Potential and current density distributions in the cell and overall fuel utilization are also presented. It is also found that the temperature gradients exist along the length of the cell, and the maximum value of the temperature for the cross-flow is at the outlet region of the cell. The distribution of the current density is uneven, and the maximum current density is located at the interfaces between the channels, ribs and the electrodes, the maximum current density result in a large over-potential and heat source in the electrodes, which is harmful to the overall performance and working lifespan of the fuel cells. A new type of flow structure should be developed to make the current flow be more evenly distributed and promote most of the TPB areas to take part in the electrochemical reactions.
Energy Technology Data Exchange (ETDEWEB)
Mimouni, N.; Chikh, S.; Rahli, O. [Laboratoire LTPMP, Fac GMGP, USTHB, BP 32, Alia, Bab Ezzouar, Algiers (Algeria); Bennacer, R., E-mail: Rachid.Bennacer@ens-cachan.fr [LMT-ENS Cachan, 61 av. du président Wilson F-94235 Cachan Cedex (France)
2014-07-15
Two-dimensional (2D) and three-dimensional (3D) numerical simulations of double diffusion natural convection in an elongated enclosure filled with a binary fluid saturating a porous medium are carried out in the present work. The Boussinesq approximation is made in the formulation of the problem, and Neumann boundary conditions for temperature and concentration are adopted, respectively, on vertical and horizontal walls of the cavity. The used numerical method is based on the control volume approach, with the third order quadratic upstream interpolation scheme in approximating the advection terms. A semi implicit method algorithm is used to handle the velocity-pressure coupling. To avoid the excessively high computer time inherent to the solution of 3D natural convection problems, full approximation storage with full multigrid method is used to solve the problem. A wide range of the controlling parameters (Rayleigh-Darcy number Ra, lateral aspect ratio Ay, Lewis number Le, and the buoyancy ration N) is investigated. We clearly show that increasing the depth of the cavity (i.e., the lateral aspect ratio) has an important effect on the flow patterns. The 2D perfect parallel flows obtained for small lateral aspect ratio are drastically destabilized by increasing the cavity lateral dimension. This yields a 3D fluid motion with a much more complex flow pattern and the usually considered 2D parallel flow model cannot be applied.
Retrograde flow in the dural sinuses detected by three-dimensional time-of-flight MR angiography
International Nuclear Information System (INIS)
Uchino, Akira; Nomiyama, Keita; Takase, Yukinori; Nakazono, Takahiko; Tominaga, Yukiko; Imaizumi, Takeshi; Kudo, Sho
2007-01-01
Retrograde flow in the left dural sinuses is sometimes detected by three-dimensional time-of-flight (3D-TOF) magnetic resonance (MR) angiography. The purpose of this study was to evaluate the incidence of this phenomenon and its characteristic features on 3D-TOF MR angiograms. We retrospectively reviewed cranial MR angiography images of 1,078 patients examined at our institution. All images were obtained by the 3D-TOF technique with one of two 1.5-T scanners. Maximum intensity projection (MIP) images in the horizontal rotation view were displayed stereoscopically. We reviewed the source images, inferosuperior MIP images, and horizontal MIP images and identified retrograde flow in the dural sinuses. We found retrograde flow in the dural sinuses of 67 patients on the source images from 3D-TOF MR angiography; the incidence was 6.2%. In 47 of the 67 patients, retrograde flow was identified in the left inferior petrosal sinus, in 13, it was seen in the left sigmoid sinus, and in 6, it was seen in the left inferior petrosal and left sigmoid sinuses. The remaining patient had retrograde flow in the left inferior petrosal and left and right sigmoid sinuses. The mean age of the patients with retrograde flow was slightly greater than that of the patients without this phenomenon (70 years vs 63 years). Retrograde flow in the dural sinuses frequently occurs on the left side in middle-aged and elderly patients during 3D-TOF MR angiography performed with the patient in the supine position. This phenomenon should not be misdiagnosed as a dural arteriovenous fistula. (orig.)
Jusoh, R.; Nazar, R.; Pop, I.
2018-03-01
A reformulation of the three-dimensional flow of a nanofluid by employing Buongiorno's model is presented. A new boundary condition is implemented in this study with the assumption of nanoparticle mass flux at the surface is zero. This condition is practically more realistic since the nanoparticle fraction at the boundary is latently controlled. This study is devoted to investigate the impact of the velocity slip and suction to the flow and heat transfer characteristics of nanofluid. The governing partial differential equations corresponding to the momentum, energy, and concentration are reduced to the ordinary differential equations by utilizing the appropriate transformation. Numerical solutions of the ordinary differential equations are obtained by using the built-in bvp4c function in Matlab. Graphical illustrations displaying the physical influence of the several nanofluid parameters on the flow velocity, temperature, and nanoparticle volume fraction profiles, as well as the skin friction coefficient and the local Nusselt number are provided. The present study discovers the existence of dual solutions at a certain range of parameters. Surprisingly, both of the solutions merge at the stretching sheet indicating that the presence of the velocity slip affects the skin friction coefficients. Stability analysis is carried out to determine the stability and reliability of the solutions. It is found that the first solution is stable while the second solution is not stable.
Prasad, Dipak; Divito, Nicholas; Byers, Matthew; White, William; Benson, Michael; van Poppel, Bret; Elkins, Christopher; Containment Dispersion Team
2017-11-01
The dispersion of a scalar contaminant through an urban environment is complex to simulate and current modeling techniques lack detailed validation data necessary to assess accuracy. This work provides a detailed data set for Computational Fluid Dynamic simulations as well as an analysis of fluid flow and contaminant dispersion across two incident angles, 0 and 45 degrees from the freestream, across an array of cubical buildings, with one building in the center column three times as tall. The contaminant is injected from the base behind the tall building. Magnetic resonance imaging techniques are used to collect three-dimensional, time-averaged, three-component velocity and concentration field data. The flow is conducted in a water channel at a fully turbulent condition. The 0 degree case shows symmetrical velocity flow around each building with counter-rotating vortices immediately behind the tall building. Scalar contaminant dispersion in this array shows a rapid draw of higher concentration fluid up the back of the tall building, which is advected downstream. The 45 degree array shows similar patterns with vortices covering a larger area in the wake of the tall building. Analysis of the streamlines around the tall building indicate more `mechanical' dispersion due to the lateral spreading of the streamlines. These experiments should help improve prediction performance.
Directory of Open Access Journals (Sweden)
Yan Zhu
2016-05-01
Full Text Available Due to the high nonlinearity of the three-dimensional (3-D unsaturated-saturated water flow equation, using a fully 3-D numerical model is computationally expensive for large scale applications. A new unsaturated-saturated water flow model is developed in this paper based on the vertical/horizontal splitting (VHS concept to split the 3-D unsaturated-saturated Richards’ equation into a two-dimensional (2-D horizontal equation and a one-dimensional (1-D vertical equation. The horizontal plane of average head gradient in the triangular prism element is derived to split the 3-D equation into the 2-D equation. The lateral flow in the horizontal plane of average head gradient represented by the 2-D equation is then calculated by the water balance method. The 1-D vertical equation is discretized by the finite difference method. The two equations are solved simultaneously by coupling them into a unified nonlinear system with a single matrix. Three synthetic cases are used to evaluate the developed model code by comparing the modeling results with those of Hydrus1D, SWMS2D and FEFLOW. We further apply the model to regional-scale modeling to simulate groundwater table fluctuations for assessing the model applicability in complex conditions. The proposed modeling method is found to be accurate with respect to measurements.
Directory of Open Access Journals (Sweden)
Song-Gui Chen
2016-01-01
Full Text Available This paper presents a three-dimensional (3D parallel multiple-relaxation-time lattice Boltzmann model (MRT-LBM for Bingham plastics which overcomes numerical instabilities in the simulation of non-Newtonian fluids for the Bhatnagar–Gross–Krook (BGK model. The MRT-LBM and several related mathematical models are briefly described. Papanastasiou’s modified model is incorporated for better numerical stability. The impact of the relaxation parameters of the model is studied in detail. The MRT-LBM is then validated through a benchmark problem: a 3D steady Poiseuille flow. The results from the numerical simulations are consistent with those derived analytically which indicates that the MRT-LBM effectively simulates Bingham fluids but with better stability. A parallel MRT-LBM framework is introduced, and the parallel efficiency is tested through a simple case. The MRT-LBM is shown to be appropriate for parallel implementation and to have high efficiency. Finally, a Bingham fluid flowing past a square-based prism with a fixed sphere is simulated. It is found the drag coefficient is a function of both Reynolds number (Re and Bingham number (Bn. These results reveal the flow behavior of Bingham plastics.
A simple three-dimensional-focusing, continuous-flow mixer for the study of fast protein dynamics.
Burke, Kelly S; Parul, Dzmitry; Reddish, Michael J; Dyer, R Brian
2013-08-07
We present a simple, yet flexible microfluidic mixer with a demonstrated mixing time as short as 80 μs that is widely accessible because it is made of commercially available parts. To simplify the study of fast protein dynamics, we have developed an inexpensive continuous-flow microfluidic mixer, requiring no specialized equipment or techniques. The mixer uses three-dimensional, hydrodynamic focusing of a protein sample stream by a surrounding sheath solution to achieve rapid diffusional mixing between the sample and sheath. Mixing initiates the reaction of interest. Reactions can be spatially observed by fluorescence or absorbance spectroscopy. We characterized the pixel-to-time calibration and diffusional mixing experimentally. We achieved a mixing time as short as 80 μs. We studied the kinetics of horse apomyoglobin (apoMb) unfolding from the intermediate (I) state to its completely unfolded (U) state, induced by a pH jump from the initial pH of 4.5 in the sample stream to a final pH of 2.0 in the sheath solution. The reaction time was probed using the fluorescence of 1-anilinonaphthalene-8-sulfonate (1,8-ANS) bound to the folded protein. We observed unfolding of apoMb within 760 μs, without populating additional intermediate states under these conditions. We also studied the reaction kinetics of the conversion of pyruvate to lactate catalyzed by lactate dehydrogenase using the intrinsic tryptophan emission of the enzyme. We observe sub-millisecond kinetics that we attribute to Michaelis complex formation and loop domain closure. These results demonstrate the utility of the three-dimensional focusing mixer for biophysical studies of protein dynamics.
Viscous flows stretching and shrinking of surfaces
Mehmood, Ahmer
2017-01-01
This authored monograph provides a detailed discussion of the boundary layer flow due to a moving plate. The topical focus lies on the 2- and 3-dimensional case, considering axially symmetric and unsteady flows. The author derives a criterion for the self-similar and non-similar flow, and the turbulent flow due to a stretching or shrinking sheet is also discussed. The target audience primarily comprises research experts in the field of boundary layer flow, but the book will also be beneficial for graduate students.
Energy Technology Data Exchange (ETDEWEB)
Speetjens, M. F. M.; Demissie, E. A. [Department of Mechanical Engineering, Energy Technology Laboratory, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Metcalfe, G. [Commonwealth Scientific and Industrial Research Organisation (CSIRO), VIC 3190 Melbourne (Australia); Clercx, H. J. H. [Department of Applied Physics, Fluid Dynamics Laboratory, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands)
2014-11-15
Laminar mixing by the inline-mixing principle is a key to many industrial fluids-engineering systems of size extending from micrometers to meters. However, insight into fundamental transport phenomena particularly under the realistic conditions of three-dimensionality (3D) and fluid inertia remains limited. This study addresses these issues for inline mixers with cylindrical geometries and adopts the Rotated Arc Mixer (RAM) as a representative system. Transport is investigated from a Lagrangian perspective by identifying and examining coherent structures that form in the 3D streamline portrait. 3D effects and fluid inertia introduce three key features that are not found in simplified configurations: transition zones between consecutive mixing cells of the inline-mixing flow; local upstream flow (in certain parameter regimes); transition/inertia-induced breaking of symmetries in the Lagrangian equations of motion (causing topological changes in coherent structures). Topological considerations strongly suggest that there nonetheless always exists a net throughflow region between inlet and outlet of the inline-mixing flow that is strictly separated from possible internal regions. The Lagrangian dynamics in this region admits representation by a 2D time-periodic Hamiltonian system. This establishes one fundamental kinematic structure for the present class of inline-mixing flows and implies universal behavior in that all states follow from the Hamiltonian breakdown of one common integrable state. A so-called period-doubling bifurcation is the only way to eliminate transport barriers originating from this state and thus is a necessary (yet not sufficient) condition for global chaos. Important in a practical context is that a common simplification in literature, i.e., cell-wise fully-developed Stokes flow (“2.5D approach”), retains these fundamental kinematic properties and deviates from the generic 3D inertial case only in a quantitative sense. This substantiates its
International Nuclear Information System (INIS)
Speetjens, M. F. M.; Demissie, E. A.; Metcalfe, G.; Clercx, H. J. H.
2014-01-01
Laminar mixing by the inline-mixing principle is a key to many industrial fluids-engineering systems of size extending from micrometers to meters. However, insight into fundamental transport phenomena particularly under the realistic conditions of three-dimensionality (3D) and fluid inertia remains limited. This study addresses these issues for inline mixers with cylindrical geometries and adopts the Rotated Arc Mixer (RAM) as a representative system. Transport is investigated from a Lagrangian perspective by identifying and examining coherent structures that form in the 3D streamline portrait. 3D effects and fluid inertia introduce three key features that are not found in simplified configurations: transition zones between consecutive mixing cells of the inline-mixing flow; local upstream flow (in certain parameter regimes); transition/inertia-induced breaking of symmetries in the Lagrangian equations of motion (causing topological changes in coherent structures). Topological considerations strongly suggest that there nonetheless always exists a net throughflow region between inlet and outlet of the inline-mixing flow that is strictly separated from possible internal regions. The Lagrangian dynamics in this region admits representation by a 2D time-periodic Hamiltonian system. This establishes one fundamental kinematic structure for the present class of inline-mixing flows and implies universal behavior in that all states follow from the Hamiltonian breakdown of one common integrable state. A so-called period-doubling bifurcation is the only way to eliminate transport barriers originating from this state and thus is a necessary (yet not sufficient) condition for global chaos. Important in a practical context is that a common simplification in literature, i.e., cell-wise fully-developed Stokes flow (“2.5D approach”), retains these fundamental kinematic properties and deviates from the generic 3D inertial case only in a quantitative sense. This substantiates its
von Boetticher, Albrecht; McArdell, Brian; Rickenmann, Dieter; Hübl, Johannes; Scheidl, Christian
2014-05-01
Attempts to model debris flow material either as a granular or as a viscous matter can not account for the wide range of debris flow processes, leading to the development of two-phase models with one phase accounting for the fluid and the other for the grains. Within this group of models, depth-averaged approaches are wide-spread, but since the rheology of true material is sensitive to pressure and shear gradient, three dimensional simulations are necessary to predict flows in complex geometries. Phase interaction can be modelled by solving the Navier-Stokes equation system for each phase and linking the phases with drag force models. However, this is a numerically expensive way that introduces a number of free parameters because too little is known about drag of non-spherical grains in non-Newtonian fluids. The approach proposed here solves one phase-averaged Navier-stokes equation system by applying the Volume of Fluid method, while still allowing to account for the sensitivity of the local rheology to pressure and shear in dependency to phase concentrations. One phase with a Herschel-Bulkley rheology represents the interstitial fluid and can mix with a second phase with the Coulomb-viscoplastic rheology of Pudasaini (Birte et al. 2013) that represents the gravel. A third phase is kept separate and represents the air. This setup allows modelling key properties of debris flow processes like run out or impact in high detail. By linking the Herschel Bulkley parameters to water content, clay mineral proportion and grain size distribution (Kaitna et al. 2007, Yu et al. 2013), and the parameters of the Coulomb-viscoplastic rheology to the angle of repose of the gravel, a reduction to one free model parameter was achieved. The resulting model is tested with laboratory experiments for its capability to reproduce the sensitivity of debris flow material to water content and channel curvature. Existing large scale flume experiments are used to corroborate the model and
Creeping Viscous Flow around a Heat-Generating Solid Sphere
DEFF Research Database (Denmark)
Krenk, Steen
1981-01-01
The velocity field for creeping viscous flow around a solid sphere due to a spherically symmetric thermal field is determined and a simple thermal generalization of Stokes' formula is obtained. The velocity field due to an instantaneous heat source at the center of the sphere is obtained in close...... form and an application to the storage of heat-generating nuclear waste is discussed....
Thermosolutal MHD flow and radiative heat transfer with viscous ...
African Journals Online (AJOL)
This paper investigates double diffusive convection MHD flow past a vertical porous plate in a chemically active fluid with radiative heat transfer in the presence of viscous work and heat source. The resulting nonlinear dimensionless equations are solved by asymptotic analysis technique giving approximate analytic ...
Khan, Junaid Ahmad; Mustafa, Meraj; Hayat, Tasawar; Alsaedi, Ahmed
2014-01-01
This article studies the viscous flow and heat transfer over a plane horizontal surface stretched non-linearly in two lateral directions. Appropriate wall conditions characterizing the non-linear variation in the velocity and temperature of the sheet are employed for the first time. A new set of similarity variables is introduced to reduce the boundary layer equations into self-similar forms. The velocity and temperature distributions are determined by two methods, namely (i) optimal homotopy analysis method (OHAM) and (ii) fourth-fifth-order Runge-Kutta integration based shooting technique. The analytic and numerical solutions are compared and these are found in excellent agreement. Influences of embedded parameters on momentum and thermal boundary layers are sketched and discussed.
Son, Geunsoo; Kim, Dongsu; Kim, YoungDo; Lyu, Siwan; Kim, Seojun
2017-04-01
concentration by using acoustic backscatter. Cross-sectional ADCP measurements in a confluence were collected with high spatial resolution in order to analyze the details of spatial distribution in the perspective of the three-dimensional mixing patterns of flow and sediment, where backscatters (or SNR) measured from ADCPs were used to track sediment mixing assuming that it could be a surrogate to estimate the suspended sediment concentration. Raw backscatter data were corrected by considering the beam spreading and absorption by water. Also, an optical Laser diffraction instrument (LISST) was used to verify the method of acoustic backscatter and to collect the particle size distribution of main stream and tributary. In addition, image-based spatial distributions of sediment mixture in the confluence were monitored in various flow conditions by using an unmanned aerial vehicle (UAV), which were compared with the spatial distribution of acoustic backscatter. As results, we found that when acoustic backscatter and flow measurements by ADCPs were well processed, they could be proper indicators to identify the spatial patterns of the three-dimensional mixing process between two rivers.
International Nuclear Information System (INIS)
Czarnecki, J.B.; Faunt, C.C.; Gable, C.W.; Zyvoloski, G.A.
1996-01-01
Development of a preliminary three-dimensional model of the saturated zone at Yucca Mountain, the potential location for a high-level nuclear waste repository, is presented. The development of the model advances the technology of interfacing: (1)complex three-dimensional hydrogeologic framework modeling; (2) fully three-dimensional, unstructured, finite-element mesh generation; and (3) groundwater flow, heat, and transport simulation. The three-dimensional hydrogeologic framework model is developed using maps, cross sections, and well data. The framework model data are used to feed an automated mesh generator, designed to discretize irregular three-dimensional solids,a nd to assign materials properties from the hydrogeologic framework model to the tetrahedral elements. The mesh generator facilitated the addition of nodes to the finite-element mesh which correspond to the exact three-dimensional position of the potentiometric surface based on water-levels from wells. A ground water flow and heat simulator is run with the resulting finite- element mesh, within a parameter-estimation program. The application of the parameter-estimation program is designed to provide optimal values of permeability and specified fluxes over the model domain to minimize the residual between observed and simulated water levels
Dinarvand, S.; Hosseini, R.; Tamim, H.; Damangir, E.; Pop, I.
2015-07-01
An unsteady three-dimensional stagnation-point flow of a nanofluid past a circular cylinder with sinusoidal radius variation is investigated numerically. By introducing new similarity transformations for the velocity, temperature, and nanoparticle volume fraction, the basic equations governing the flow and heat and mass transfer are reduced to highly nonlinear ordinary differential equations. The resulting nonlinear system is solved numerically by the fourth-order Runge-Kutta method with the shooting technique. The thermophoresis and Brownian motion effects occur in the transport equations. The velocity, temperature, and nanoparticle concentration profiles are analyzed with respect to the involved parameters of interest, namely, unsteadiness parameter, Brownian motion parameter, thermophoresis parameter, Prandtl number, and Lewis number. Numerical values of the friction coefficient, diffusion mass flux, and heat flux are computed. It is found that the friction coefficient and heat transfer rate increase with increasing unsteadiness parameter (the highest heat transfer rate at the surface occurs if the thermophoresis and Brownian motion effects are absent) and decrease with increasing both thermophoresis and Brownian motion parameters. The present results are found to be in good agreement with previously published results.
International Nuclear Information System (INIS)
Smith, Brian L.
2007-01-01
The paper describes Computational Fluid Dynamics (CFD) calculations undertaken in support of analyses of three-dimensional flows that take place in the drywell volumes of advanced boiling water reactors with passive decay-heat removal systems. Data for comparison are taken from the 1/40th-scale European Simplified Boiling Water Reactor (ESBWR) mock-up facility PANDA under conditions of symmetric steam injection and asymmetric outflow. Steady-state simulations for pure steam conditions illustrate how the separate flow streams mix to ensure balanced outflow conditions to the condenser units. A transient calculation has also been performed to examine how air, assumed to be released from solution in the PANDA boiler, would ultimately accumulate in the separate condenser units. Results provide a possible explanation for the rundown in performance of one of the condensers, behaviour which was repeatedly observed in some of the earlier PANDA tests. The work also provides more general insights on how trace amounts of non-condensable gases may accumulate in passive cooling equipment
Hansen, Arthur G.
1958-01-01
Analysis is presented on the possible similarity solutions of the three-dimensional, laminar, incompressible, boundary-layer equations referred to orthogonal, curvilinear coordinate systems. Requirements of the existence of similarity solutions are obtained for the following: flow over developable surface and flow over non-developable surfaces with proportional mainstream velocity components.
Capillary and viscous perturbations to Helmholtz flows
Moore, M. R.
2014-02-21
Inspired by recent calculations by Thoraval et al. (Phys. Rev. Lett., vol. 108, 2012, p.Â 264506) relating to droplet impact, this paper presents an analysis of the perturbations to the free surface caused by small surface tension and viscosity in steady Helmholtz flows. In particular, we identify the regimes in which appreciable vorticity can be shed from the boundary layer to the bulk flow. © 2014 Cambridge University Press.
Viscous Flow with Large Fluid-Fluid Interface Displacement
DEFF Research Database (Denmark)
Rasmussen, Henrik Koblitz; Hassager, Ole; Saasen, Arild
1998-01-01
The arbitrary Lagrange-Euler (ALE) kinematic description has been implemented in a 3D transient finite element program to simulate multiple fluid flows with fluid-fluid interface or surface displacements. The description of fluid interfaces includes variable interfacial tension, and the formulation...... is useful in the simulation of low and intermediate Reynolds number viscous flow. The displacement of two immiscible Newtonian fluids in a vertical (concentric and eccentric) annulus and a (vertical and inclined)tube is simulated....
Modeling of brittle-viscous flow using discrete particles
Thordén Haug, Øystein; Barabasch, Jessica; Virgo, Simon; Souche, Alban; Galland, Olivier; Mair, Karen; Abe, Steffen; Urai, Janos L.
2017-04-01
Many geological processes involve both viscous flow and brittle fractures, e.g. boudinage, folding and magmatic intrusions. Numerical modeling of such viscous-brittle materials poses challenges: one has to account for the discrete fracturing, the continuous viscous flow, the coupling between them, and potential pressure dependence of the flow. The Discrete Element Method (DEM) is a numerical technique, widely used for studying fracture of geomaterials. However, the implementation of viscous fluid flow in discrete element models is not trivial. In this study, we model quasi-viscous fluid flow behavior using Esys-Particle software (Abe et al., 2004). We build on the methodology of Abe and Urai (2012) where a combination of elastic repulsion and dashpot interactions between the discrete particles is implemented. Several benchmarks are presented to illustrate the material properties. Here, we present extensive, systematic material tests to characterize the rheology of quasi-viscous DEM particle packing. We present two tests: a simple shear test and a channel flow test, both in 2D and 3D. In the simple shear tests, simulations were performed in a box, where the upper wall is moved with a constant velocity in the x-direction, causing shear deformation of the particle assemblage. Here, the boundary conditions are periodic on the sides, with constant forces on the upper and lower walls. In the channel flow tests, a piston pushes a sample through a channel by Poisseuille flow. For both setups, we present the resulting stress-strain relationships over a range of material parameters, confining stress and strain rate. Results show power-law dependence between stress and strain rate, with a non-linear dependence on confining force. The material is strain softening under some conditions (which). Additionally, volumetric strain can be dilatant or compactant, depending on porosity, confining pressure and strain rate. Constitutive relations are implemented in a way that limits the
Salama, Amgad
2013-09-01
In this work the problem of flow in three-dimensional, axisymmetric, heterogeneous porous medium domain is investigated numerically. For this system, it is natural to use cylindrical coordinate system, which is useful in describing phenomena that have some rotational symmetry about the longitudinal axis. This can happen in porous media, for example, in the vicinity of production/injection wells. The basic feature of this system is the fact that the flux component (volume flow rate per unit area) in the radial direction is changing because of the continuous change of the area. In this case, variables change rapidly closer to the axis of symmetry and this requires the mesh to be denser. In this work, we generalize a methodology that allows coarser mesh to be used and yet yields accurate results. This method is based on constructing local analytical solution in each cell in the radial direction and moves the derivatives in the other directions to the source term. A new expression for the harmonic mean of the hydraulic conductivity in the radial direction is developed. Apparently, this approach conforms to the analytical solution for uni-directional flows in radial direction in homogeneous porous media. For the case when the porous medium is heterogeneous or the boundary conditions is more complex, comparing with the mesh-independent solution, this approach requires only coarser mesh to arrive at this solution while the traditional methods require more denser mesh. Comparisons for different hydraulic conductivity scenarios and boundary conditions have also been introduced. © 2013 Elsevier B.V.
Large-scale computation of incompressible viscous flow by least-squares finite element method
Jiang, Bo-Nan; Lin, T. L.; Povinelli, Louis A.
1993-01-01
The least-squares finite element method (LSFEM) based on the velocity-pressure-vorticity formulation is applied to large-scale/three-dimensional steady incompressible Navier-Stokes problems. This method can accommodate equal-order interpolations and results in symmetric, positive definite algebraic system which can be solved effectively by simple iterative methods. The first-order velocity-Bernoulli function-vorticity formulation for incompressible viscous flows is also tested. For three-dimensional cases, an additional compatibility equation, i.e., the divergence of the vorticity vector should be zero, is included to make the first-order system elliptic. The simple substitution of the Newton's method is employed to linearize the partial differential equations, the LSFEM is used to obtain discretized equations, and the system of algebraic equations is solved using the Jacobi preconditioned conjugate gradient method which avoids formation of either element or global matrices (matrix-free) to achieve high efficiency. To show the validity of this scheme for large-scale computation, we give numerical results for 2D driven cavity problem at Re = 10000 with 408 x 400 bilinear elements. The flow in a 3D cavity is calculated at Re = 100, 400, and 1,000 with 50 x 50 x 50 trilinear elements. The Taylor-Goertler-like vortices are observed for Re = 1,000.
On the calculation of dynamic and heat loads on a three-dimensional body in a hypersonic flow
Bocharov, A. N.; Bityurin, V. A.; Evstigneev, N. M.; Fortov, V. E.; Golovin, N. N.; Petrovskiy, V. P.; Ryabkov, O. I.; Teplyakov, I. O.; Shustov, A. A.; Solomonov, Yu S.
2018-01-01
We consider a three-dimensional body in a hypersonic flow at zero angle of attack. Our aim is to estimate heat and aerodynamic loads on specific body elements. We are considering a previously developed code to solve coupled heat- and mass-transfer problem. The change of the surface shape is taken into account by formation of the iterative process for the wall material ablation. The solution is conducted on the multi-graphics-processing-unit (multi-GPU) cluster. Five Mach number points are considered, namely for M = 20-28. For each point we estimate body shape after surface ablation, heat loads on the surface and aerodynamic loads on the whole body and its elements. The latter is done using Gauss-type quadrature on the surface of the body. The comparison of the results for different Mach numbers is performed. We also estimate the efficiency of the Navier-Stokes code on multi-GPU and central processing unit architecture for the coupled heat and mass transfer problem.
Befus, K. M.; Kroeger, K. D.; Smith, C. G.; Swarzenski, P. W.
2017-12-01
Fresh groundwater discharge to coastal environments contribute to the physical and chemical conditions of coastal waters. At regional scales, groundwater fluxes remain poorly constrained, representing uncertainty in both water and chemical budgets that have implications for downstream ecosystem health and for how human activities alter coastal hydrologic processes. Coastal groundwater discharges remain widely unconstrained due to the interconnectedness of highly heterogeneous hydrogeologic frameworks and hydrologic conditions. We use regional-scale, three-dimensional groundwater flow models with the best available hydrostratigraphic framework data to calculate the magnitude of groundwater discharging from coastal aquifers to coastal waterbodies along the eastern U.S. In addition, we constrain the inland areas that contribute to coastal groundwater discharges using particle tracking. We find that 27 km3/yr of groundwater enters coastal waters of the eastern U.S. and Gulf of Mexico and was over 175,000 km2. The contributing areas to coastal groundwater discharge extended kilometers inland and often were supplied by recharge occurring tens of kilometers inland. These results suggest that coastal groundwater discharges rely on larger contributing areas and potentially transport more dissolved constituents than previously calculated, which are important factors for constraining the role of groundwater in coastal chemical budgets and its impacts on coastal ecosystems.
A three-dimensional two-phase flow model for a liquid-fed direct methanol fuel cell
Ge, Jiabin; Liu, Hongtan
A three-dimensional, two-phase, multi-component model has been developed for a liquid-fed DMFC. The modeling domain consists of the membrane, two catalyst layers, two diffusion layers, and two channels. Both liquid and gas phases are considered in the entire anode, including the channel, the diffusion layer and the catalyst layer; while at the cathode, two phases are considered in the gas diffusion layer and the catalyst layer but only single gas phase is considered in the channels. For electrochemical kinetics, the Tafel equation incorporating the effects of two phases is used at both the cathode and anode sides. At the anode side the presence of gas phase reduces the active catalyst areas, while at the cathode side the presence of liquid water reduces the active catalyst areas. The mixed potential effects due to methanol crossover are also included in the model. The results from the two-phase flow mode fit the experimental results better than those from the single-phase model. The modeling results show that the single-phase models over-predict methanol crossover. The modeling results also show that the porosity of the anode diffusion layer plays an important role in the DMFC performance. With low diffusion layer porosity, the produced carbon dioxide cannot be removed effectively from the catalyst layer, thus reducing the active catalyst area as well as blocking methanol from reaching the reaction zone. A similar effect exits in the cathode for the liquid water.
Xu, Hang; Fan, Tao; You, Xiang Cheng
2012-09-01
The steady, three dimensional mixed convection flow of a Cu-water nanofluid past a stretching sheet is investigated. The homogenous model is adopted to simplify the physical problem. With a set of similarity transformations, the governing equations are reduced to a set of ordinary differential equations, which are then solved by means of the homotopy analysis method (HAM). The novel HAM technique for the choice of the convergent control auxiliary parameters ħ and optimal parameters of the initial guesses, as well as the new approach of the computational errors are introduced. with the help of these novel methods, the highly accurate analytical approximations are obtained for both the velocity and the temperature profiles. Besides, the effects of the nanoparticle volume fraction φ on the local skin friction and the local Nusselt number are presented and discussed. It is found that the nanofluid can improve on the heat transfer characteristics to a large extent. As far as we know, this problem has not been considered before and the results are new and original.
Khan, Waqar Azeem; Khan, Masood; Malik, Rabia
2014-01-01
This article addresses the steady three-dimensional flow of an Oldroyd-B nanofluid over a bidirectional stretching surface with heat generation/absorption effects. Suitable similarity transformations are employed to reduce the governing partial differential equations into coupled nonlinear ordinary differential equations. These nonlinear ordinary differential equations are then solved analytically by using the homotpy analysis method (HAM). Graphically results are presented and discussed for various parameters, namely, Deborah numbers β1 and β2, heat generation/absorption parameter λ, Prandtl parameter Pr, Brownian motion parameters Nb, thermophoresis parameter Nt and Lewis number Le. We have seen that the increasing values of the Brownian motion parameter Nt and thermophoresis parameter Nt leads to an increase in the temperature field and thermal boundary layer thickness while the opposite behavior is observed for concentration field and concentration boundary layer thickness. To see the validity of the present work, the numerical results are compared with the analytical solutions obtained by Homotopy analysis method and noted an excellent agreement for the limiting cases.
Directory of Open Access Journals (Sweden)
Ahmadreza Baghaie
Full Text Available Scanning Electron Microscope (SEM as one of the major research and industrial equipment for imaging of micro-scale samples and surfaces has gained extensive attention from its emerge. However, the acquired micrographs still remain two-dimensional (2D. In the current work a novel and highly accurate approach is proposed to recover the hidden third-dimension by use of multi-view image acquisition of the microscopic samples combined with pre/post-processing steps including sparse feature-based stereo rectification, nonlocal-based optical flow estimation for dense matching and finally depth estimation. Employing the proposed approach, three-dimensional (3D reconstructions of highly complex microscopic samples were achieved to facilitate the interpretation of topology and geometry of surface/shape attributes of the samples. As a byproduct of the proposed approach, high-definition 3D printed models of the samples can be generated as a tangible means of physical understanding. Extensive comparisons with the state-of-the-art reveal the strength and superiority of the proposed method in uncovering the details of the highly complex microscopic samples.
Viscous flow over spinning cones at angle of attack.
Lin, T. C.; Rubin, S. G.
1973-01-01
A numerical finite-difference method is developed for evaluating the Magnus coefficients on spinning cones in laminar flow. The merged layer, the strong interaction region, and the downstream boundary layer are all considered. The numerical method is a predictor-corrector scheme developed for three-dimensional flows with or without crossflow diffusion. This method is particularly useful in problems in which a symmetry plane does not exist. Several contributions to the Magnus force and moments are considered. These include asymmetries in displacement thickness, centrifugal force and crossflow shear, and the effects of crossflow separation and vortex formation. Comparisons are made with experimental data and other analyses.
Three-dimensional fluid mechanics of particulate two-phase flows in U-bend and helical conduits
Tiwari, Prashant; Antal, Steven P.; Podowski, Michael Z.
2006-04-01
The results of numerous studies performed to date have shown that the performance of various hydraulic systems can be significantly improved by using curved conduit geometries instead of straight tubes. In particular, the formation of Dean vortices, which enhance the development of centrifugal instabilities, has been identified as a factor behind reducing the near-wall concentration buildup in particulate flow devices (e.g., in membrane filtration modules). Still, several issues regarding the effect of conduit curvature on local multidimensional phenomena governing fluid flow still remain open. A related issue is concerned with the impact that conduit geometry makes on the concentration distribution of a dispersed phase in two-phase flows in general, and in particulate flows (solid/liquid or solid/gas suspensions) in particular. It turns out that only very limited efforts have been made in the past to understand the fluid mechanics of such flows via advanced computer simulations. The purpose of this paper is to present the results of full three-dimensional (3D) theoretical and numerical analyses of single- and two-phase dilute particle/liquid flows in U-bend and helical curved conduits. The numerical analysis is based on computational fluid dynamics (CFD) simulations performed using a state-of-the-art multiphase flow computer code, NPHASE. The major issues discussed in the first part of the paper are concerned with the effect of curved/coiled geometry on the evolution of flow field and the associated wall shear. It has been demonstrated that the primary curvature (a common factor for both the U-bend and helix geometries) may cause a substantial asymmetry in the radial distribution of the main flow velocity. This, in turn, leads to a significant, albeit highly nonuniform, increase in the wall shear stress. Specifically, the wall shear around the outer half of tube circumference may become twice the corresponding value for a straight tube, and gradually decrease to
Kordilla, Jannes; Noffz, Torsten; Dentz, Marco; Geyer, Tobias; Tartakovsky, Alexandre M.
2017-11-01
In this work, we study gravity-driven flow of water in the presence of air on a synthetic surface intersected by a horizontal fracture and investigate the importance of droplet and rivulet flow modes on the partitioning behavior at the fracture intersection. We present laboratory experiments, three-dimensional smoothed particle hydrodynamics (SPH) simulations using a heavily parallelized code, and a theoretical analysis. The flow-rate-dependent mode switching from droplets to rivulets is observed in experiments and reproduced by the SPH model, and the transition ranges agree in SPH simulations and laboratory experiments. We show that flow modes heavily influence the "bypass" behavior of water flowing along a fracture junction. Flows favoring the formation of droplets exhibit a much stronger bypass capacity compared to rivulet flows, where nearly the whole fluid mass is initially stored within the horizontal fracture. The effect of fluid buffering within the horizontal fracture is presented in terms of dimensionless fracture inflow so that characteristic scaling regimes can be recovered. For both cases (rivulets and droplets), the flow within the horizontal fracture transitions into a Washburn regime until a critical threshold is reached and the bypass efficiency increases. For rivulet flows, the initial filling of the horizontal fracture is described by classical plug flow. Meanwhile, for droplet flows, a size-dependent partitioning behavior is observed, and the filling of the fracture takes longer. For the case of rivulet flow, we provide an analytical solution that demonstrates the existence of classical Washburn flow within the horizontal fracture.
Kim, Jinyong; Luo, Gang; Wang, Chao-Yang
2017-10-01
3D fine-mesh flow-fields recently developed by Toyota Mirai improved water management and mass transport in proton exchange membrane (PEM) fuel cell stacks, suggesting their potential value for robust and high-power PEM fuel cell stack performance. In such complex flow-fields, Forchheimer's inertial effect is dominant at high current density. In this work, a two-phase flow model of 3D complex flow-fields of PEMFCs is developed by accounting for Forchheimer's inertial effect, for the first time, to elucidate the underlying mechanism of liquid water behavior and mass transport inside 3D complex flow-fields and their adjacent gas diffusion layers (GDL). It is found that Forchheimer's inertial effect enhances liquid water removal from flow-fields and adds additional flow resistance around baffles, which improves interfacial liquid water and mass transport. As a result, substantial improvements in high current density cell performance and operational stability are expected in PEMFCs with 3D complex flow-fields, compared to PEMFCs with conventional flow-fields. Higher current density operation required to further reduce PEMFC stack cost per kW in the future will necessitate optimizing complex flow-field designs using the present model, in order to efficiently remove a large amount of product water and hence minimize the mass transport voltage loss.
Numerical modeling of the motion of deformable ellipsoidal objects in slow viscous flows
Jiang, Dazhi
2007-03-01
An algorithm for modeling the strain and rotation of deformable ellipsoidal objects in viscous flows based on Eshelby's (1957. Proceedings of the Royal Society of London A241, 376-396) theory is presented and is implemented in a fully graphic mathematics application (Mathcad ®, http://www.mathsoft.com). The algorithm resolves all singular cases encountered in modeling large finite deformations. The orientation of ellipsoidal objects is specified in terms of polar coordinate angles which are easily converted to the trend and plunge angles of the three principal axes rather than the Euler angles. With the Mathcad worksheets presented in the supplementary data associated with this paper, one can model the strain and rotation paths of individual deformable objects and the development of preferred orientation and shape fabrics for a population of deformable objects in any homogeneous viscous flow. The shape and preferred orientation fabrics for a population of deformable objects can be presented in both a three-dimensional form and a two-dimensional form, allowing easy comparison between field data and model predictions. The full graphic interface of Mathcad ® makes using the worksheets as easy as using a spreadsheet. The modeler can interact fully with the computation and customize the type and format of the output data to best fit the purpose of the investigation and to facilitate the comparison of model predictions with geological observations.
Viscous anisotropic hydrodynamics for the Gubser flow
Martinez, M.; McNelis, M.; Heinz, U.
2017-11-01
In this work we describe the dynamics of a highly anisotropic system undergoing boost-invariant longitudinal and azimuthally symmetric radial expansion (Gubser flow) for arbitrary shear viscosity to entropy density ratio. We derive the equations of motion of dissipative anisotropic hydrodynamics by applying to this situation the moments method recently derived by Molnár et al. (MNR) [E. Molnar, H. Niemi, and D. H. Rischke, "Derivation of anisotropic dissipative fluid dynamics from the Boltzmann equation," Phys. Rev. D93 no. 11, (2016) 114025, arxiv:arXiv:1602.00573 [nucl-th], E. Molnar, H. Niemi, and D. H. Rischke, "Closing the equations of motion of anisotropic fluid dynamics by a judicious choice of a moment of the Boltzmann equation," Phys. Rev. D94 no. 12, (2016) 125003, arxiv:arXiv:1606.09019 [nucl-th
Numerical solution of inviscid and viscous flow around the profile
Slouka, Martin; Kozel, Karel; Prihoda, Jaromir
2015-05-01
This work deals with the 2D numerical solution of inviscid compressible flow and viscous compressible laminar and turbulent flow around the profile. In a case of turbulent flow algebraic Baldwin-Lomax model is used and compared with Wilcox's k-ω model. Calculations are done in GAMM channel computational domain with 10% DCA profile and in turbine cascade computational domain with 8% DCA profile. Numerical methods are based on a finite volume solution and compared with experimental measurements for 8% DCA profile.
Numerical solution of inviscid and viscous flow around the profile
Directory of Open Access Journals (Sweden)
Slouka Martin
2015-01-01
Full Text Available This work deals with the 2D numerical solution of inviscid compressible flow and viscous compressible laminar and turbulent flow around the profile. In a case of turbulent flow algebraic Baldwin-Lomax model is used and compared with Wilcox’s k-ω model. Calculations are done in GAMM channel computational domain with 10% DCA profile and in turbine cascade computational domain with 8% DCA profile. Numerical methods are based on a finite volume solution and compared with experimental measurements for 8% DCA profile.
A semi-elliptic analysis of internal viscous flows
International Nuclear Information System (INIS)
Ghia, U.; Ramamurti, R.; Ghia, K.N.
1986-01-01
The increased demands placed presently on the performance of compressors and turbines of gas-turbine engines have, for some time, pointed the need for accurate analysis of viscous flows in turbomachinery. With the recent developments of advanced computational facilities, much effort has been made to respond to this need. Various mathematical formulations, grid systems and numerical techniques have been developed for the numerical solution of the viscous flow equations (Refs. 1-4). The full Navier-Stokes equations as well as their corresponding thin-layer approximate form have been employed in H- as well as C-grids, using explicit or implicit methods, including convergence enhancement techniques based on multi-grid methodology. Nevertheless, obtaining converged solutions for general geometries on acceptably refined grids remains a computationally demanding task. The present paper discusses a reduced form on the governing equations which can capture much of the physics, while requiring less computer resources than the full Navier-Stokes equations
Huang, M.; Bisht, G.; Zhou, T.; Chen, X.; Dai, H.; Hammond, G. E.; Riley, W. J.; Downs, J.; Liu, Y.; Zachara, J. M.
2016-12-01
A fully coupled three-dimensional surface and subsurface land model is developed and applied to a site along the Columbia River to simulate three-way interactions among river water, groundwater, and land surface processes. The model features the coupling of the Community Land Model version 4.5 (CLM4.5) and a massively-parallel multi-physics reactive tranport model (PFLOTRAN). The coupled model (CLM-PFLOTRAN) is applied to a 400m×400m study domain instrumented with groundwater monitoring wells in the Hanford 300 Area along the Columbia River. CLM-PFLOTRAN simulations are performed at three different spatial resolutions over the period 2011-2015 to evaluate the impact of spatial resolution on simulated variables. To demonstrate the difference in model simulations with and without lateral subsurface flow, a vertical-only CLM-PFLOTRAN simulation is also conducted for comparison. Results show that the coupled model is skillful in simulating stream-aquifer interactions, and the land-surface energy partitioning can be strongly modulated by groundwater-river water interactions in high water years due to increased soil moisture availability caused by elevated groundwater table. In addition, spatial resolution does not seem to impact the land surface energy flux simulations, although it is a key factor for accurately estimating the mass exchange rates at the boundaries and associated biogeochemical reactions in the aquifer. The coupled model developed in this study establishes a solid foundation for understanding co-evolution of hydrology and biogeochemistry along the river corridors under historical and future hydro-climate changes.
Decker, Jeremy D.; Swain, Eric D.; Stith, Bradley M.; Langtimm, Catherine A.
2013-01-01
Everglades restoration activities may cause changes to temperature and salinity stratification at the Port of the Islands (POI) marina, which could affect its suitability as a cold weather refuge for manatees. To better understand how the Picayune Strand Restoration Project (PSRP) may alter this important resource in Collier County in southwestern Florida, the USGS has developed a three-dimensional hydrodynamic model for the marina and canal system at POI. Empirical data suggest that manatees aggregate at the site during winter because of thermal inversions that provide warmer water near the bottom that appears to only occur in the presence of salinity stratification. To study these phenomena, the environmental fluid dynamics code simulator was used to represent temperature and salinity transport within POI. Boundary inputs were generated using a larger two-dimensional model constructed with the flow and transport in a linked overland-aquifer density-dependent system simulator. Model results for a representative winter period match observed trends in salinity and temperature fluctuations and produce temperature inversions similar to observed values. Modified boundary conditions, representing proposed PSRP alterations, were also tested to examine the possible effect on the salinity stratification and temperature inversion within POI. Results show that during some periods, salinity stratification is reduced resulting in a subsequent reduction in temperature inversion compared with the existing conditions simulation. This may have an effect on POI’s suitability as a passive thermal refuge for manatees and other temperature-sensitive species. Additional testing was completed to determine the important physical relationships affecting POI’s suitability as a refuge.
Energy Technology Data Exchange (ETDEWEB)
Finn, John M., E-mail: finn@lanl.gov [T-5, Applied Mathematics and Plasma Physics, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
2015-03-15
Properties of integration schemes for solenoidal fields in three dimensions are studied, with a focus on integrating magnetic field lines in a plasma using adaptive time stepping. It is shown that implicit midpoint (IM) and a scheme we call three-dimensional leapfrog (LF) can do a good job (in the sense of preserving KAM tori) of integrating fields that are reversible, or (for LF) have a “special divergence-free” (SDF) property. We review the notion of a self-adjoint scheme, showing that such schemes are at least second order accurate and can always be formed by composing an arbitrary scheme with its adjoint. We also review the concept of reversibility, showing that a reversible but not exactly volume-preserving scheme can lead to a fractal invariant measure in a chaotic region, although this property may not often be observable. We also show numerical results indicating that the IM and LF schemes can fail to preserve KAM tori when the reversibility property (and the SDF property for LF) of the field is broken. We discuss extensions to measure preserving flows, the integration of magnetic field lines in a plasma and the integration of rays for several plasma waves. The main new result of this paper relates to non-uniform time stepping for volume-preserving flows. We investigate two potential schemes, both based on the general method of Feng and Shang [Numer. Math. 71, 451 (1995)], in which the flow is integrated in split time steps, each Hamiltonian in two dimensions. The first scheme is an extension of the method of extended phase space, a well-proven method of symplectic integration with non-uniform time steps. This method is found not to work, and an explanation is given. The second method investigated is a method based on transformation to canonical variables for the two split-step Hamiltonian systems. This method, which is related to the method of non-canonical generating functions of Richardson and Finn [Plasma Phys. Controlled Fusion 54, 014004 (2012
Weed, Richard Allen; Sankar, L. N.
1994-01-01
An increasing amount of research activity in computational fluid dynamics has been devoted to the development of efficient algorithms for parallel computing systems. The increasing performance to price ratio of engineering workstations has led to research to development procedures for implementing a parallel computing system composed of distributed workstations. This thesis proposal outlines an ongoing research program to develop efficient strategies for performing three-dimensional flow analysis on distributed computing systems. The PVM parallel programming interface was used to modify an existing three-dimensional flow solver, the TEAM code developed by Lockheed for the Air Force, to function as a parallel flow solver on clusters of workstations. Steady flow solutions were generated for three different wing and body geometries to validate the code and evaluate code performance. The proposed research will extend the parallel code development to determine the most efficient strategies for unsteady flow simulations.
Developments in the simulation of compressible inviscid and viscous flow on supercomputers
International Nuclear Information System (INIS)
Steger, J.L.; Buning, P.G.; Tel Aviv Univ., Israel)
1985-01-01
In anticipation of future supercomputers, finite difference codes are rapidly being extended to simulate three-dimensional compressible flow about complex configurations. Some of these developments are reviewed. The importance of computational flow visualization and diagnostic methods to three-dimensional flow simulation is also briefly discussed. 46 references
Orr, Matthew W.
This investigation concerns the design, analysis, and initial testing of a new, two-component wall shear gage for 3D, high-temperature flows. This gage is a direct-measuring, non-nulling design with a round head surrounded by a small gap. Two flexure wheels are used to allow small motions of the floating head. Fiber-optic displacement sensors measure how far the polished faces of counterweights on the wheels move in relation to a fixed housing as the primary measurement system. No viscous damping was required. The gage has both fiber-optic instrumentation and strain gages mounted on the flexures for validation of the newer fiber optics. The sensor is constructed of Haynes RTM 230RTM, a high-temperature nickel alloy. The gage housing is made of 316 stainless steel. All components of the gage in pure fiber-optic form can survive to a temperature of 1073 K. The bonding methods of the backup strain gages limit their maximum temperature to 473 K. The dynamic range of the gage is from 0--500 Pa (0--10g) and higher shears can be measured by changing the floating head size. Extensive use of finite element modeling was critical to the design and analysis of the gage. Static structural, modal, and thermal analyses were performed on the flexures using the ANSYS finite element package. Static finite element analysis predicted the response of the flexures to a given load, and static calibrations using a direct force method confirmed these results. Finite element modal analysis results were within 16.4% for the first mode and within 30% for the second mode when compared with the experimentally determined modes. Vibration characteristics of the gage were determined from experimental free vibration data after the gage was subjected to an impulse. Uncertainties in the finished geometry make this level of error acceptable. A transient thermal analysis examined the effects of a very high heat flux on the exposed head of the gage. The 100,000 W/m2 heat flux used in this analysis is
International Nuclear Information System (INIS)
Cole, C.R.; Wurstner, S.K.; Williams, M.D.; Thorne, P.D.; Bergeron, M.P.
1997-12-01
A three-dimensional numerical model of groundwater flow and transport, based on the Coupled Fluid Energy, and Solute Transport (CFEST) code, was developed for the Hanford Site to support the Hanford Groundwater Project (HGWP), managed by Pacific Northwest National Laboratory. The model was developed to increase the understanding and better forecast the migration of several contaminant plumes being monitored by the HGWP, and to support the Hanford Site Composite Analysis for low-level waste disposal in the 200-Area Plateau. Recent modeling efforts have focused on continued refinement of an initial version of the three-dimensional model developed in 1995 and its application to simulate future transport of selected contaminant plumes in the aquifer system. This version of the model was updated using a more current version of the CFEST code called CFEST96. Prior to conducting simulations of contaminant transport with the three-dimensional model, a previous steady-state, two-dimensional model of the unconfined aquifer system was recalibrated to 1979 water-table conditions with a statistical inverse method implemented in the CFEST-INV computer code. The results of the recalibration were used to refine the three-dimensional conceptual model and to calibrate it with a conceptualization that preserves the two-dimensional hydraulic properties and knowledge of the aquifer's three-dimensional properties for the same 1979 water-table conditions. The transient behavior of the three-dimensional flow model was also calibrated by adjusting model storage properties (specific yield) until transient water-table predictions approximated observed water-table elevations between 1979 and 1996
Energy Technology Data Exchange (ETDEWEB)
Cole, C.R.; Wurstner, S.K.; Williams, M.D.; Thorne, P.D.; Bergeron, M.P.
1997-12-01
A three-dimensional numerical model of groundwater flow and transport, based on the Coupled Fluid Energy, and Solute Transport (CFEST) code, was developed for the Hanford Site to support the Hanford Groundwater Project (HGWP), managed by Pacific Northwest National Laboratory. The model was developed to increase the understanding and better forecast the migration of several contaminant plumes being monitored by the HGWP, and to support the Hanford Site Composite Analysis for low-level waste disposal in the 200-Area Plateau. Recent modeling efforts have focused on continued refinement of an initial version of the three-dimensional model developed in 1995 and its application to simulate future transport of selected contaminant plumes in the aquifer system. This version of the model was updated using a more current version of the CFEST code called CFEST96. Prior to conducting simulations of contaminant transport with the three-dimensional model, a previous steady-state, two-dimensional model of the unconfined aquifer system was recalibrated to 1979 water-table conditions with a statistical inverse method implemented in the CFEST-INV computer code. The results of the recalibration were used to refine the three-dimensional conceptual model and to calibrate it with a conceptualization that preserves the two-dimensional hydraulic properties and knowledge of the aquifer`s three-dimensional properties for the same 1979 water-table conditions. The transient behavior of the three-dimensional flow model was also calibrated by adjusting model storage properties (specific yield) until transient water-table predictions approximated observed water-table elevations between 1979 and 1996.
Goffart, D.; Wal, D.J. van der; Klomp, E.M.; Hoogstraten, H.W.; Janssen, L.P.B.M.; Breysse, L.; Trolez, Y.
1996-01-01
A three-dimensional modeling of the transporting elements in a self-wiping corotating twin-screw extruder has been carried out by using the finite element package Sepran. This simulation uses the 3D geometry of the channel rolled over the twin-screw, which consists of the intermeshing and normal
Visualization of bacterial flagella dynamics in a viscous shear flow
Ali, Jamel; Kim, Minjun
2016-11-01
We report on the dynamics of tethered bacterial flagella in an applied viscous shear flow and analyze their behavior using image processing. Flagellin proteins were repolymerized into flagellar filaments functionalized with biotin at their proximal end, and allowed to self-assemble within a micro channel coated with streptavidin. It was observed that all attached flagellar filaments aligned with the steady shear flow of various polymeric solutions. Furthermore it was observed that many of the filaments were stretched, and at elevated flow rates began to undergo polymorphic transformations, which were initiated at one end of the flagellum. When undergoing a change to a different helical form the flagellum was observed to transform to an oppositely handed helix, as to counteract the viscous torque imparted by the shear flow. It was also observed that some flagellar filaments did not undergo polymorphic transformations, but rotated about their helical axis. The rate of this rotation appears to be a function of the applied flow rate. These results expand on previous experimental work and aid in the development of a novel platform that harnesses the autonomic response of a 'forest' of bacterial flagella for engineering applications. This work was funded by NSF Grant CMMI-1000255, KEIT MOTIE Grant No. 10052980, and with Government support under and awarded by DoD, Air Force Office of Scientific Research, National Defense Science and Engineering Graduate (NDSEG) Fellowship, 32 CFR 168a.
Three dimensional vortices and interfaces in Hele-Shaw cells
International Nuclear Information System (INIS)
Pumir, A.
1987-06-01
A model of nonviscous flow, based on the Biot-Savart equations is used to examine the existence of singularities in three dimensional, incompressible, hydrodynamic equations. The results suggest a fairly simple physical mechanism, which could lead to the formation of singularities in the nonviscous case: two vortex tubes with opposite circulations pair up and stretch each other, until the radii of the vortex cores become extremely small, causing a divergence of the vorticity. The cases of a perfect and a slightly viscous fluid are considered. The results are unclear as to whether the vorticity of a slightly viscous fluid can become infinite or not, and whether singularities exist. The dynamics of hydrodynamic interfaces are also investigated. The propagation of bubbles in a slightly viscous fluid, in a Hele-Shaw cell are described [fr
Clark, Heather
Blunt trailing edge airfoils offer structural and aerodynamic advantages in modern wind turbine and aircraft applications. However, penalties are introduced concurrently by vortex shedding at separation. In particular, the adverse effects of increased drag and unsteady loading motivate the development of a control strategy for the blunt trailing edge wake. Closed-loop control is pursued for its potentially greater effectiveness and efficiency, relative to open-loop forcing. Toward this aim, the thesis addresses the need for estimation of the state from limited measurements. The wake of a blunt trailing edge body is investigated experimentally through simultaneous measurements of velocity and the spanwise distribution of fluctuating surface pressure. Passive forcing is implemented with an array of vortex generators that are arranged according to the characteristic wavelength of the dominant small-scale instability. The guiding considerations for the analysis and discussion are physical characterization and the development of estimation strategies based on surface pressure. Joint examination of the measured variables through reduced-order modelling, wavelet analysis, and conditional averaging yields insight regarding the unsteady, three-dimensional nature of the flow. The investigation of forcing is focused upon the influence of the perturbation on the surface pressure and the performance of estimation models in the modified wake. It is found that low-frequency amplitude modulation of the pressure results from variation of both the magnitude of velocity fluctuations and the vortex formation length. The forcing regularizes the shedding in time and space, as evidenced by the attenuated modulation and enhanced spanwise coherence of the amplitude and phase. Examination of this behaviour confirms the connection between amplitude modulation and vortex dislocations in bluff body wakes. Several properties of the estimation approaches hold in general. It is shown that the
Parallel discrete vortex methods for viscous flow simulation
Takeda, Kenji
In this thesis a parallel discrete vortex method is developed in order to investigate the long-time behaviour of bluff body wakes. The method is based on inviscid theory, and its extension to include viscous effects is a far from trivial problem. In this work four grid-free viscous models are directly compared to assess their accuracy and efficiency. The random walk, diffusion velocity, corrected core-spreading and vorticity redistribution methods are compared for simulating unbounded fluid flows, and for flows past an impulsively started cylinder at Reynolds numbers between 550 and 9500. The code uses a common core, so that the only free parameters are those directly related to the viscous models. The vorticity redistribution method encompasses all of the advantages of a purely Lagrangian method and incorporates a dynamic regridding scheme to maintain accurate discretisation of the vorticity field. This is used to simulate long-time flow past an impulsively started cylinder for Reynolds numbers 100, 150 and 1000. The code is fully parallel and achieves good speedup on both commodity and proprietary supercomputer systems. At Reynolds numbers below 150 the breakdown of the primary vortex street has been simulated. Results reveal a merging process, causing relaxation to a parallel shear flow. This itself sheds vortices, creating a secondary wake of increased wavelength. At Reynolds number 1000 the cylinder wake becomes chaotic, forming distinct vortex couples. These couples self-convect and can travel upstream. This has a destabilising effect on the vortex street, inducing merging, formation of tripolar and quadrupolar structures and, ultimately, spontaneous ejection of vortex couples upstream of the initial disturbance.
Thermal stability for a reactive viscous flow in a slab
Okoya, S S
2002-01-01
The paper deals with the effect of dimensionless non - Newtonian coefficient on the thermal stability of a reactive viscous liquid in steady flow between parallel heated plates. It is assumed that the liquid is symmetrically heated and the flow fully developed. Approximate analytical solution is obtained for the velocity of the flow and the criterion for which this solution is valid is determined. After the velocity distribution is known, the temperature distribution may be calculated. Criticality and disappearance of criticality (transition values) are obtained in the following cases: (i) Bimolecular (ii) Arrhenius and (iii) Sensitized temperature dependence. We have observed that nonlinear effect from velocity and temperature fields introduced decaying for the transitional values of the dimensionless central temperature. Other effects of this nonlinearity are reported. We also give results for the plane - Couette flow problem. The results help to enhance understanding of the interplay between Newtonian and ...
Energy Technology Data Exchange (ETDEWEB)
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.
International Nuclear Information System (INIS)
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
Song-Gui Chen; Chuan-Hu Zhang; Yun-Tian Feng; Qi-Cheng Sun; Feng Jin
2016-01-01
This paper presents a three-dimensional (3D) parallel multiple-relaxation-time lattice Boltzmann model (MRT-LBM) for Bingham plastics which overcomes numerical instabilities in the simulation of non-Newtonian fluids for the Bhatnagar–Gross–Krook (BGK) model. The MRT-LBM and several related mathematical models are briefly described. Papanastasiou’s modified model is incorporated for better numerical stability. The impact of the relaxation parameters of the model is studied in detail. The MRT-L...
Voss, Clifford I.; Simmons, Craig T.; Robinson, Neville I.
2010-01-01
This benchmark for three-dimensional (3D) numerical simulators of variable-density groundwater flow and solute or energy transport consists of matching simulation results with the semi-analytical solution for the transition from one steady-state convective mode to another in a porous box. Previous experimental and analytical studies of natural convective flow in an inclined porous layer have shown that there are a variety of convective modes possible depending on system parameters, geometry and inclination. In particular, there is a well-defined transition from the helicoidal mode consisting of downslope longitudinal rolls superimposed upon an upslope unicellular roll to a mode consisting of purely an upslope unicellular roll. Three-dimensional benchmarks for variable-density simulators are currently (2009) lacking and comparison of simulation results with this transition locus provides an unambiguous means to test the ability of such simulators to represent steady-state unstable 3D variable-density physics.
Viscous flow solutions with a cubic spline approximation
Rubin, S. G.; Graves, R. A., Jr.
1975-01-01
A cubic spline approximation is used for the solution of several problems in fluid mechanics. This procedure provides a high degree of accuracy even with a nonuniform mesh, and leads to a more accurate treatment of derivative boundary conditions. The truncation errors and stability limitations of several typical integration schemes are presented. For two-dimensional flows a spline-alternating-direction-implicit (SADI) method is evaluated. The spline procedure is assessed and results are presented for the one-dimensional nonlinear Burgers' equation, as well as the two-dimensional diffusion equation and the vorticity-stream function system describing the viscous flow in a driven cavity. Comparisons are made with analytic solutions for the first two problems and with finite-difference calculations for the cavity flow.
Directory of Open Access Journals (Sweden)
Fiaz Ur Rehman
2018-03-01
Full Text Available In the present paper a theoretical investigation is performed to analyze heat and mass transport enhancement of water-based nanofluid for three dimensional (3D MHD stagnation-point flow caused by an exponentially stretched surface. Water is considered as a base fluid. There are three (3 types of nanoparticles considered in this study namely, CuO (Copper oxide, Fe3O4 (Magnetite, and Al2O3 (Alumina are considered along with water. In this problem we invoked the boundary layer phenomena and suitable similarity transformation, as a result our three dimensional non-linear equations of describing current problem are transmuted into nonlinear and non-homogeneous differential equations involving ordinary derivatives. We solved the final equations by applying homotopy analysis technique. Influential outcomes of aggressing parameters involved in this study, effecting profiles of temperature field and velocity are explained in detail. Graphical results of involved parameters appearing in considered nanofluid are presented separately. It is worth mentioning that Skin-friction along x and y-direction is maximum for Copper oxide-water nanofluid and minimum for Alumina-water nanofluid. Result for local Nusselt number is maximum for Copper oxide-water nanofluid and is minimum for magnetite-water nanofluid. Keywords: Heat transfer, Nanofluids, Stagnation-point flow, Three-dimensional flow, Nano particles, Boundary layer
Rheology of granular flows immersed in a viscous fluid
International Nuclear Information System (INIS)
Amarsid, Lhassan
2015-01-01
We investigate the behavior of granular materials immersed in a viscous fluid by means of extensive simulations based on the Discrete Element Method for particle dynamics coupled with the Lattice Boltzmann method for the fluid. We show that, for a broad range of parameters such as shear rate, confining stress and viscosity, the internal friction coefficient and packing fraction are well described by a single 'visco-inertial' dimensionless parameter combining inertial and Stokes numbers. The frictional behavior under constant confining pressure is mapped into a viscous behavior under volume-controlled conditions, leading to the divergence of the effective normal and shear viscosities in inverse square of the distance to the critical packing fraction. The results are in excellent agreement with the experimental data of Boyer et al. (2011). The evolution of the force network in terms of connectivity and anisotropy as a function of the visco-inertial number, indicates that the increase of frictional strength is a direct consequence of structural anisotropy enhanced by both fluid viscosity and grain inertia. In view of application to a potential nuclear accident, we also study the fragmentation and flow of confined porous aggregates in a fluid under the action of local overpressures and pressure gradients as well as gravity-driven flow of immersed particles in an hourglass. (author)
Dynamics of flexible fibers transported in confined viscous flows
Cappello, Jean; Duprat, Camille; Du Roure, Olivia; Nagel, Mathias; Gallaire, François; Lindner, Anke
2017-11-01
The dynamics of elongated objects has been extensively studied in unbounded media as for example the sedimentation of fibers at low Reynolds numbers. It has recently been shown that these transport dynamics are strongly modified by bounding walls. Here we focus on the dynamics of flexible fibers confined by the top and bottom walls of a microchannel and transported in pressure-driven flows. We combine well-controlled microfluidic experiments and simulations using modified Brinkmann equations. We control shape, orientation, and mechanical properties of our fibers using micro-fabrication techniques and in-situ characterization methods. These elastic fibers can be deformed by viscous and pressure forces leading to very rich transport dynamics coupling lateral drift with shape evolution. We show that the bending of a perpendicular fiber is proportional to an elasto-viscous number and we fully characterize the influence of the confinement on the deformation of the fiber. Experiments on parallel flexible fibers reveal the existence of a buckling threshold. The European Research Council is acknowledged for funding the work through a consolidator Grant (ERC PaDyFlow 682367).
Kinetic theory model for the flow of a simple gas from a three-dimensional axisymmetric nozzle
Riley, B. R.
1991-01-01
A system of nonlinear integral equations equivalent to the Krook kinetic equations for the steady state is the mathematical basis used to develop a computer code to model the flowfields for low-thrust three-dimensional axisymmetric nozzles. The method of characteristics is used to solve numerically by an iteration process the approximated Boltzmann equation for the number density, temperature, and velocity profiles of a simple gas as it expands into a vacuum. Results predict backscatter and show the effect of the nozzle wall boundary layer on the external flowfields.
Poehler, Thorsten; Kunte, Robert; Hoenen, Herwart; Jeschke, Peter; Wissdorf, Walter; Brockmann, Klaus J; Benter, Thorsten
2011-11-01
In this study, the validation and analysis of steady state numerical simulations of the gas flows within a multi-purpose ion source (MPIS) are presented. The experimental results were obtained with particle image velocimetry (PIV) measurements in a non-scaled MPIS. Two-dimensional time-averaged velocity and turbulent kinetic energy distributions are presented for two dry gas volume flow rates. The numerical results of the validation simulations are in very good agreement with the experimental data. All significant flow features have been correctly predicted within the accuracy of the experiments. For technical reasons, the experiments were conducted at room temperature. Thus, numerical simulations of ionization conditions at two operating points of the MPIS are also presented. It is clearly shown that the dry gas volume flow rate has the most significant impact on the overall flow pattern within the APLI source; far less critical is the (larger) nebulization gas flow. In addition to the approximate solution of Reynolds-Averaged Navier-Stokes equations, a transport equation for the relative analyte concentration has been solved. The results yield information on the three-dimensional analyte distribution within the source. It becomes evident that for ion transport into the MS ion transfer capillary, electromagnetic forces are at least as important as fluid dynamic forces. However, only the fluid dynamics determines the three-dimensional distribution of analyte gas. Thus, local flow phenomena in close proximity to the spray shield are strongly impacting on the ionization efficiency.
Passive Control of Viscous Flow via Elastic Snap-Through
Gomez, Michael; Moulton, Derek E.; Vella, Dominic
2017-10-01
We demonstrate the passive control of viscous flow in a channel by using an elastic arch embedded in the flow. Depending on the fluid flux, the arch may "snap" between two states—constricting and unconstricting—that differ in hydraulic conductivity by up to an order of magnitude. We use a combination of experiments at a macroscopic scale and theory to study the constricting and unconstricting states, and determine the critical flux required to transition between them. We show that such a device may be precisely tuned for use in a range of applications, and, in particular, has potential as a passive microfluidic fuse to prevent excessive fluxes in rigid-walled channels.
International Nuclear Information System (INIS)
Bottoni, M.; Dorr, B.; Homann, C.; Struwe, D.
1983-07-01
The computer programme BACCHUS implemented at KfK includes a steady-state version, a two-dimensional and a three-dimensional transient single-phase flow version describing the thermal-hydraulic behaviour of the coolant (sodium or water) in bundle geometry under nominal or accident conditions. All versions are coupled with a pin model describing the temperature distribution in fuel (or electrical heaters) and cladding. The report describes the programme from the viewpoints of the geometrical model, the mathematical foundations and the numerical treatment of the basic equations. Although emphasis is put on the three-dimensional version, the two-dimensional and the steady state versions are also documented in self-consistent sections. (orig.) [de
A Viscous-Inviscid Interaction Model for Rotor Aerodynamics
DEFF Research Database (Denmark)
Filippone, Antonino; Sørensen, Jens Nørkær
1994-01-01
A numerical model for the viscous-inviscid interactive computations ofrotor flows is presented. The basic methodology for deriving the outer inviscid solution is a fully three-dimensional boundary element method.The inner viscous domain, i.e. the boundary layer, is described by the two-dimensiona...
Senthilkumar, M.; Elango, L.
A three-dimensional mathematical model to simulate regional groundwater flow was used in the lower Palar River basin, in southern India. The study area is characterised by heavy ion of groundwater for agricultural, industrial and drinking water supplies. There are three major pumping stations on the riverbed apart from a number of wells distributed over the area. The model simulates groundwater flow over an area of about 392 km2 with 70 rows, 40 columns, and two layers. The model simulated a transient-state condition for the period 1991-2001. The model was calibrated for steady- and transient-state conditions. There was a reasonable match between the computed and observed heads. The transient model was run until the year 2010 to forecast groundwater flow under various scenarios of overpumping and less recharge. Based on the modelling results, it is shown that the aquifer system is stable at the present rate of pumping, excepting for a few locations along the coast where the groundwater head drops from 0.4 to 1.81 m below sea level during the dry seasons. Further, there was a decline in the groundwater head by 0.9 to 2.4 m below sea level in the eastern part of the area when the aquifer system was subjected to an additional groundwater withdrawal of 2 million gallons per day (MGD) at a major pumping station. Les modèles mathématiques en trois dimensions de l'écoulement souterrain régional sont très utiles pour la gestion des ressources en eau souterraine, car ils permettent une évaluation des composantes des processus hydrologiques et fournissent une description physique de l'écoulement de l'eau dans un aquifère. Une telle modélisation a été entreprise sur une partie du bassin inférieur de la rivière Palar, dans le sud de l'Inde. La zone d'étude est caractérisée par des prélèvements importants d'eau souterraine pour l'agriculture, l'industrie et l'eau potable. Il existe trois grandes stations de pompage sur la rivière en plus d'un certain nombre
Instability of a cantilevered flexible plate in viscous channel flow
Balint, T. S.; Lucey, A. D.
2005-10-01
The stability of a flexible cantilevered plate in viscous channel flow is studied as a representation of the dynamics of the human upper airway. The focus is on instability mechanisms of the soft palate (flexible plate) that cause airway blockage during sleep. We solve the Navier Stokes equations for flow with Reynolds numbers up to 1500 fully coupled with the dynamics of the plate motion solved using finite-differences. The study is 2-D and based upon linearized plate mechanics. When both upper and lower airways are open, the plate is found to lose its stability through a flutter mechanism and a critical Reynolds number exists. When one airway is closed, the plate principally loses its stability through a divergence mechanism and a critical flow speed exists. However, below the divergence-onset flow speed, flutter can exist for low levels of structural damping in the flexible plate. Our results serve to extend understanding of flow-induced instability of cantilevered flexible plates and will ultimately improve the diagnosis and treatment of upper-airway disorders.
Bounds on fluid permeability for viscous flow through porous media
International Nuclear Information System (INIS)
Berryman, J.G.
1985-01-01
General properties of variational bounds on Darcy's constant for slow viscous flow through porous media are studied. The bounds are also evaluated numerically for the penetrable sphere model. The bound of Doi depending on two-point correlations and the analytical bound of Weissberg and Prager give comparable results in the low density limit but the analytical bound is superior for higher densities. Prager's bound depending on three-point correlation functions is worse than the analytical bound at low densities but better (although comparable to it) at high densities. A procedure for methodically improving Prager's three point bound is presented. By introducing a Gaussian trial function, the three-point bound is improved by an order of magnitude for moderate values of porosity. The new bounds are comparable in magnitude to the Kozeny--Carman empirical relation for porous materials
Viscous flow in the near-Venusian plasma wake
International Nuclear Information System (INIS)
Perez-de-Tejada, H.; Dryer, M.; Vaisberg, O.L.
1977-01-01
The acquisiton of the Venera 9 and 10 plasma probe data has provided further support for the notion that the shocked solar wind in the flank regions of the Venusian ionosheath interacts viscously with the local ionospheric plasma and that the resulting mixing region is rapidly forced into the planetary umbra. The measured velocities and flow directions suggest that the deflection of the mixing layer downstream of the terminator proceeds at a fast pace, as was predicted from the analysis of a suitable MHD analog proposed by Perez-de-Tejada and Dryer (1976). By measuring the apparent displacement of the mixing region within the planetary umbra with respect to the position of the undeviated ionopause (calculated from the inviscid flow model of Spreiter et al, (1970) it is possible to obtain an order-of-magnitude estimate of the equivalent kinematic viscosity coefficient of the flow in the region. Some speculative comments are also given in regard to the behavior of the flow in the Venusian plasma wake, in particular, to the implications that the penetration of the mixing layer into the umbra may have for the formation of the nighttime Venusian ionosphere
Numerical modeling of the motion of rigid ellipsoidal objects in slow viscous flows: A new approach
Jiang, Dazhi
2007-02-01
A simple algorithm for modeling the rotation of rigid ellipsoidal objects in viscous flows based on Jeffery's (1922, Proceedings of the Royal Society of London A102, 161-179) theory is presented and is implemented in a fully graphic mathematics application Mathcad ® ( http://www.mathsoft.com). The orientation of ellipsoidal objects is specified in terms of polar coordinate angles that can be easily converted to the trend and plunge angles of the three principal axes rather than the Euler angles. With the Mathcad worksheets presented in the supplementary data associated with this paper, modeling the rotation paths of individual rigid objects, the development of inclusion trail geometry within syn-kinematic porphyroblasts, and the development of preferred orientation and shape fabrics for a population of rigid objects becomes as easy a task as using a spreadsheet. The shape and preferred orientation fabrics for a population of rigid objects can be presented in both a three-dimensional form and a two-dimensional form, allowing easy comparison between field data and model predictions. The modeler can customize the type and format of the output to best fit the purpose of the investigation and to facilitate the comparison of model predictions with geological observations. Application examples are presented for various types of modeling involving rigid objects.
Saaid, Hicham; Segers, Patrick; Novara, Matteo; Claessens, Tom; Verdonck, Pascal
2018-03-01
The characterization of flow patterns in the left ventricle may help the development and interpretation of flow-based parameters of cardiac function and (patho-)physiology. Yet, in vivo visualization of highly dynamic three-dimensional flow patterns in an opaque and moving chamber is a challenging task. This has been shown in several recent multidisciplinary studies where in vivo imaging methods are often complemented by in silico solutions, or by in vitro methods. Because of its distinctive features, particle image velocimetry (PIV) has been extensively used to investigate flow dynamics in the cardiovascular field. However, full volumetric PIV data in a dynamically changing geometry such as the left ventricle remain extremely scarce, which justifies the present study. An investigation of the left ventricle flow making use of a customized cardiovascular simulator is presented; a multiplane scanning-stereoscopic PIV setup is used, which allows for the measurement of independent planes across the measurement volume. Due to the accuracy in traversing the illumination and imaging systems, the present setup allows to reconstruct the flow in a 3D volume performing only one single calibration. The effects of the orientation of a prosthetic mitral valve in anatomical and anti-anatomical configurations have been investigated during the diastolic filling time. The measurement is performed in a phase-locked manner; the mean velocity components are presented together with the vorticity and turbulent kinetic energy maps. The reconstructed 3D flow structures downstream the bileaflet mitral valve are shown, which provides additional insight of the highly three-dimensional flow.
Fang, Hongwei
1996-02-01
Based on the tensor analysis of water-sediment two-phase flow, the basic model equations for clear water flow and sediment-laden flow are deduced in the general curve coordinates for natural water variable-density turbulent flow. Furthermore, corresponding boundary conditions are also presented in connection with the composition and movement of non-uniform bed material. The theoretical results are applied to the calculation of the float open caisson in the construction period and good results are obtained.
Guermond, J. L.
2011-05-04
The purpose of this paper is to validate a new highly parallelizable direction splitting algorithm. The parallelization capabilities of this algorithm are illustrated by providing a highly accurate solution for the start-up flow in a three-dimensional impulsively started lid-driven cavity of aspect ratio 1×1×2 at Reynolds numbers 1000 and 5000. The computations are done in parallel (up to 1024 processors) on adapted grids of up to 2 billion nodes in three space dimensions. Velocity profiles are given at dimensionless times t=4, 8, and 12; at least four digits are expected to be correct at Re=1000. © 2011 John Wiley & Sons, Ltd.
International Nuclear Information System (INIS)
Onuma, Kazuhiro; Terada, Kenji; Matsumura, Katsuhide; Koyama, Toshihiro; Yajima, Kazuaki
2008-01-01
Demonstration test of underground cavern type disposal facilities is planed though carrying out construction of full scale engineering barrier system which simulated in the underground space in full scale and under actual environment. This test consists of three part, these are construction test, performance test and measurement test. Behavior of near field rock mass is measured about hydrological behavior under and after construction to evaluate effect at test facility. To make plan of pore pressure measurement, three dimensional groundwater flow analysis has been carried out. Based on comparison of analysis before and after test, detail plan has been studied. (author)
International Nuclear Information System (INIS)
Lee, Wu Sang; Kim, Dae Hyun; Min, Jae Hong; Chung Jin Taek
2007-01-01
Endwall losses contribute significantly to the overall losses in modern turbomachinery, especially when aerodynamic airfoil load and pressure ratio are increased. Hence, reducing the extend and intensity of the secondary flow structures helps to enhance overall efficiency. From the large range of viable approaches, a promising combination positioning and height of endwall contouring was chosen. The objective of this study is to document the three-dimensional flow in a turbine cascade in terms of streamwise vorticity, total pressure loss distribution and static pressure distribution on the endwall and blade surface and to propose an appropriate positioning and height of the endwall contouring which show best secondary, overall loss reduction among the simulated endwall. The flow through the gas turbine were numerically analyzed using three dimensional Navier-Stroke equations with a commercial CFD code ANSYS CFX-10. The result shows that the overall loss is reduced near the flat endwall rather than contoured endwall, and the case of contoured endwall installed at 30% from leading edge with height of 25% for span showed best performance
Bilal Ashraf, M.; Alsaedi, A.; Hayat, T.; Shehzad, S. A.
2017-06-01
Heat and mass transfer effects in the three-dimensional mixed convection flow of a viscoelastic fluid with internal heat source/sink and chemical reaction have been investigated in the present work. The flow generation is because of an exponentially stretching surface. Magnetic field normal to the direction of flow is considered. Convective conditions at the surface are also encountered. Appropriate similarity transformations are utilized to reduce the boundary layer partial differential equations into the ordinary differential equations. The homotopy analysis method is used to develop the solution expressions. Impacts of different controlling parameters such as ratio parameter, Hartman number, internal heat source/sink, chemical reaction, mixed convection, concentration buoyancy parameter and Biot numbers on the velocity, temperature and concentration profiles are analyzed. The local Nusselt and Sherwood numbers are sketched and examined.
Three-dimensional neuroimaging
International Nuclear Information System (INIS)
Toga, A.W.
1990-01-01
This book reports on new neuroimaging technologies that are revolutionizing the study of the brain be enabling investigators to visualize its structure and entire pattern of functional activity in three dimensions. The book provides a theoretical and practical explanation of the new science of creating three-dimensional computer images of the brain. The coverage includes a review of the technology and methodology of neuroimaging, the instrumentation and procedures, issues of quantification, analytic protocols, and descriptions of neuroimaging systems. Examples are given to illustrate the use of three-dimensional enuroimaging to quantitate spatial measurements, perform analysis of autoradiographic and histological studies, and study the relationship between brain structure and function
Weinhart, Thomas; Hartkamp, R.; Thornton, Anthony Richard; Luding, Stefan
Dry, frictional, steady-state granular flows down an inclined, rough surface are studied with discrete particle simulations. From this exemplary flow situation, macroscopic fields, consistent with the conservation laws of continuum theory, are obtained from microscopic data by time-averaging and
Weinhart, Thomas; Hartkamp, Remco; Thornton, Anthony Richard; Luding, Stefan
2013-01-01
Dry, frictional, steady-state granular flows down an inclined, rough surface are studied with discrete particle simulations. From this exemplary flow situation, macroscopic fields, consistent with the conservation laws of continuum theory, are obtained from microscopic data by time-averaging and
DEFF Research Database (Denmark)
Motosuke, Masahiro; Jensen, Thomas Glasdam; Zhuang, Guisheng
2011-01-01
A miniaturized flow cytometry incorporating both fluidic and optical systems has a great possibility for portable biochemical sensing or point-of-care diagnostics. This paper presents a simple microfluidic flow cytometer combining reliable 3D hydrodynamic focusing and optical detection without op...... to be applied as a portable platform of cytometer chip....
International Nuclear Information System (INIS)
Zhu, H P; Yu, A B
2004-01-01
Granular flow in a cylindrical hopper with flat bottom is investigated based on the results generated by the discrete element method. The dependence of flow behaviour on the geometric and physical parameters of the hopper and particles, such as the orifice size and wall roughness of hoppers, and frictional and damping coefficients between particles, is analysed to establish the spatial and statistical distributions of microdynamic variables related to flow and force structures such as velocity, porosity, coordination number, and interaction forces between particles and between particles and walls. It is shown from the velocity field that there are four different zones in the hopper flow: a stagnant zone, a plug flow zone, a converging flow zone, and a transition zone from plug flow to converging flow. The Beverloo equation can describe the relationship between discharge rate and orifice size; however, the constants in the equation may vary with the wall friction coefficient, particle friction and damping coefficients. The flow and force structures of particles in the hopper are spatially non-uniform. In particular, porosity is high in the region near the orifice and low in the upper part and around the bottom corner of the hopper, whilst the coordination number has an opposite distribution. Large contact forces are experienced by particles around the bottom corner whereas small forces are experienced by particles in the upper part and the region near the orifice. However, there is a region above the orifice where particles experience the maximum total interaction forces between particles; the forces gradually propagate from this region into the bed and have a minimum value in the central upper part. The velocity distribution, flow and force structures are affected by the geometric and physical parameters of the hopper and particles
Yamaguchi, H.; Takamori, K.; Perrier, P.; Graur, I.; Matsuda, Y.; Niimi, T.
2016-01-01
The viscous slip coefficient for helium-argon binary gas mixture is extracted from the experimental values of the mass flow rate through a microtube. The mass flow rate is measured by the constant-volume method. The viscous slip coefficient was obtained by identifying the measured mass flow rate through a microtube with the corresponding analytical expression, which is a function of the Knudsen number. The measurements were carried out in the slip flow regime where the first-order slip bounda...
Modeling and control of flow-induced vibrations of a flexible hydrofoil in viscous flow
Caverly, Ryan James; Li, Chenyang; Chae, Eun Jung; Forbes, James Richard; Young, Yin Lu
2016-06-01
In this paper, a reduced-order model (ROM) of the flow-induced vibrations of a flexible cantilevered hydrofoil is developed and used to design an active feedback controller. The ROM is developed using data from high-fidelity viscous fluid-structure interaction (FSI) simulations and includes nonlinear terms to accurately capture the effect of lock-in. An active linear quadratic Gaussian (LQG) controller is designed based on a linearization of the ROM and is implemented in simulation with the ROM and the high-fidelity viscous FSI model. A controller saturation method is also presented that ensures that the control force applied to the system remains within a prescribed range. Simulation results demonstrate that the LQG controller successfully suppresses vibrations in both the ROM and viscous FSI simulations using a reasonable amount of control force.
DEFF Research Database (Denmark)
Hansen, Kim Granly
axial velocity, and pressure drop provided as a blind test in connection with the 10th International Workshop on Two-Phase Flow Prediction held in Merseburg, Germany, 2002. The simulated profiles are in good qualitative agreement with the experiments, but the extend of the radial solid segregation...... to a blind-test in connection to the 10th international workshop on two-phase flow prediction held in Merseburg, Germany, 2002. The results are validated against experimental findings of particle mass flux across the riser and pressure profile along the riser. The calculations show good agreement...... of the particulate phase is modeled using the kinetic theory for granular flow, and the gas phase turbulence is modeled using a Sub-Grid-Scale model. A computational study of a cold flowing CFB riser has been performed. The results have been compared to experimental findings of particle volume fraction, particle...
Energy Technology Data Exchange (ETDEWEB)
Solodov, V.G. [Kharkov State Automobile and Highway Technical University, Theoretical Mechanics and Hydraulics Department, Kharkov (Ukraine)
1997-12-31
The article describes numerical models and some results of numerical simulation of self-excited oscillatory flow regimes through exhaust diffusers of large steam turbines, operating as a part of compartment (jointly with last stage). The modelling is based on a model of ideal gas flow and full nonstationary 3D formulation and 2nd time and space order explicit Godunov`s scheme. (author) 11 refs.
Energy Technology Data Exchange (ETDEWEB)
Jugdutt, B.I.; Hutchins, G.M.; Bulkley, B.H.; Becker, L.C.
1979-11-01
Myocardial infarcts were examined in dogs to determine the spatial distribution of infarction in the region at risk and the relation between infarction and collateral blood flow. Permanent occlusion of the left circumflex (LC) coronary artery at a constant site was made in 27 conscious dogs that were sacrificed 2 days later. The anatomic region at risk was defined by postmortem coronary arteriography as the volume of the occluded LC coronary bed. The masses of the left ventricle (LV), infarct (I) and risk region (R) were calculated from planimetered areas of weighted bread-loaf sections of LV. Infarct size was directly related to the mass of the risk region (I = 0.53 R - 9.87; r = 0.97; p < 0.001). There was no infarction when R was less than about 20 g or 20% of the LV. The infarcts were mainly subendocardial and tapered from base to apex of the LV; 34% of the risk region became infarcted at the base compared with 22% at the apex. In all dogs, a significant rim of noninfarcted myocardium was identified at lateral aspects of the risk region, even at the endocardial surface. Using 9-..mu.. radioactive microspheres, initial postocclusion flow at the margin of the infarct, but well within the risk region, was higher than at the center, and outer flows were higher than inner flows. Postocclusion flow was even higher in the noninfarcted rim within the risk region, but was still significantly less than flow to normal, nonrisk areas. Collateral flows throughout the risk region increased during the first hour after occlusion, and were even higher at 2 days.Epicardially and laterally within the anatomic risk region there is a substantial amount of tissue that does not infarct despite initally reduced blood flow.
International Nuclear Information System (INIS)
Jugdutt, B.I.; Hutchins, G.M.; Bulkley, B.H.; Becker, L.C.
1979-01-01
Myocardial infarcts were examined in dogs to determine the spatial distribution of infarction in the region at risk and the relation between infarction and collateral blood flow. Permanent occlusion of the left circumflex (LC) coronary artery at a constant site was made in 27 conscious dogs that were sacrificed 2 days later. The anatomic region at risk was defined by postmortem coronary arteriography as the volume of the occluded LC coronary bed. The masses of the left ventricle (LV), infarct (I) and risk region (R) were calculated from planimetered areas of weighted bread-loaf sections of LV. Infarct size was directly related to the mass of the risk region (I = 0.53 R - 9.87; r = 0.97; p < 0.001). There was no infarction when R was less than about 20 g or 20% of the LV. The infarcts were mainly subendocardial and tapered from base to apex of the LV; 34% of the risk region became infarcted at the base compared with 22% at the apex. In all dogs, a significant rim of noninfarcted myocardium was identified at lateral aspects of the risk region, even at the endocardial surface. Using 9-μ radioactive microspheres, initial postocclusion flow at the margin of the infarct, but well within the risk region, was higher than at the center, and outer flows were higher than inner flows. Postocclusion flow was even higher in the noninfarcted rim within the risk region, but was still significantly less than flow to normal, nonrisk areas. Collateral flows throughout the risk region increased during the first hour after occlusion, and were even higher at 2 days.Epicardially and laterally within the anatomic risk region there is a substantial amount of tissue that does not infarct despite initally reduced blood flow
Mateo Villanueva, P. A.; Hradisky, M.
2010-12-01
Simulations of fluvial flows are strongly influenced by geometric complexity and overall uncertainty on measured flow variables, including those assumed to be well known boundary conditions. Often, 2D steady-state models are used for computational simulations of flows at the scale of natural rivers. Such models have been successfully incorporated in iRIC (formerly MD_SWMS), one of the widely used quasi-3D CFD solvers to perform studies of environmental flows. iRIC aids in estimating such quantities as surface roughness and shear stress, which, in turn, can be used to estimate sediment transport. However, the computational results are inherently limited in accuracy because of restricting the computations to 2D, or quasi-3D, space, which can affect the values of these predictions. In the present work we perform computer-based simulations of fluvial flows using OpenFOAM, a free, open source fully 3D CFD software package, and compare our results to predictions obtained from iRIC. First, we study the suitability of OpenFOAM as the main CFD solver to analyze fluvial flows and validate our results for two well documented rectangular channel configurations: the first case consists of a large aspect-ratio channel (ratio of depth over width 0.017, ratio of depth over length 0.0019) with a rectangular obstacle mounted at the bottom wall; the second case involves a large aspect-ratio channel (ratio of depth over width 0.1, ratio of depth over length 0.0025) with cubic obstacles mounted at the lower wall (one obstacle) and upper wall (two obstacles). Secondly, we apply our model to simulation or river at natural scale and compare our results to the output obtained from iRIC to quantify the differences in velocity profiles and other flow parameters when comparable solution techniques are used. Steady-state, RANS k-epsilon models are employed for all simulations.
De Grazia, D.; Moxey, D.; Sherwin, S. J.; Kravtsova, M. A.; Ruban, A. I.
2018-02-01
In this paper we study the boundary-layer separation produced in a high-speed subsonic boundary layer by a small wall roughness. Specifically, we present a direct numerical simulation (DNS) of a two-dimensional boundary-layer flow over a flat plate encountering a three-dimensional Gaussian-shaped hump. This work was motivated by the lack of DNS data of boundary-layer flows past roughness elements in a similar regime which is typical of civil aviation. The Mach and Reynolds numbers are chosen to be relevant for aeronautical applications when considering small imperfections at the leading edge of wings. We analyze different heights of the hump: The smaller heights result in a weakly nonlinear regime, while the larger result in a fully nonlinear regime with an increasing laminar separation bubble arising downstream of the roughness element and the formation of a pair of streamwise counterrotating vortices which appear to support themselves.
Hayat, Tasawar; Qayyum, Sajid; Shehzad, Sabir Ali; Alsaedi, Ahmed
2018-03-01
The present research article focuses on three-dimensional flow of viscoelastic(second grade) nanofluid in the presence of Cattaneo-Christov double-diffusion theory. Flow caused is due to stretching sheet. Characteristics of heat transfer are interpreted by considering the heat generation/absorption. Nanofluid theory comprises of Brownian motion and thermophoresis. Cattaneo-Christov double-diffusion theory is introduced in the energy and concentration expressions. Such diffusions are developed as a part of formulating the thermal and solutal relaxation times framework. Suitable variables are implemented for the conversion of partial differential systems into a sets of ordinary differential equations. The transformed expressions have been explored through homotopic algorithm. Behavior of sundry variables on the velocities, temperature and concentration are scrutinized graphically. Numerical values of skin friction coefficients are also calculated and examined. Here thermal field enhances for heat generation parameter while reverse situation is noticed for heat absorption parameter.
Directory of Open Access Journals (Sweden)
Jigisha U. Pandya
2012-01-01
Full Text Available The behavior of the non-linear-coupled systems arising in axially symmetric hydromagnetics flow between two horizontal plates in a rotating system is analyzed, where the lower is a stretching sheet and upper is a porous solid plate. The equations of conservation of mass and momentum are transformed to a system of coupled nonlinear ordinary differential equations. These equations for the velocity field are solved numerically by using quintic spline collocation method. To solve the nonlinear equation, quasilinearization technique has been used. The numerical results are presented through graphs, in which the effects of viscosity, through flow, magnetic flux, and rotational velocity on velocity field are discussed.
Thielicke, William; Stamhuis, Eize J.
The effect of airfoil design parameters, such as airfoil thickness and camber, are well understood in steady-state aerodynamics. But this knowledge cannot be readily applied to the flapping flight in insects and birds: flow visualizations and computational analyses of flapping flight have identified
DEFF Research Database (Denmark)
Motosuke, Masahiro; Jensen, Thomas Glasdam; Zhuang, Guisheng
2011-01-01
optical fibers in a monolithic architecture fabricated by a single photolithographic process. The vertical flow focusing is achieved by the optimized inlet geometry in a PDMS lid onto the substrate with detection channel and integrated optics. The simplified approach indicates the possibility...
International Nuclear Information System (INIS)
Cohen, Andrew J.B.
1999-01-01
Numerical simulations of groundwater flow at Yucca Mountain, Nevada are used to investigate how the faulted hydrogeologic structure influences groundwater flow from a proposed high-level nuclear waste repository. Simulations are performed using a 3-D model that has a unique grid block discretization to accurately represent the faulted geologic units, which have variable thicknesses and orientations. Irregular grid blocks enable explicit representation of these features. Each hydrogeologic layer is discretized into a single layer of irregular and dipping grid blocks, and faults are discretized such that they are laterally continuous and displacement varies along strike. In addition, the presence of altered fault zones is explicitly modeled, as appropriate. The model has 23 layers and 11 faults, and approximately 57,000 grid blocks and 200,000 grid block connections. In the past, field measurement of upward vertical head gradients and high water table temperatures near faults were interpreted as indicators of upwelling from a deep carbonate aquifer. Simulations show, however, that these features can be readily explained by the geometry of hydrogeologic layers, the variability of layer permeabilities and thermal conductivities, and by the presence of permeable fault zones or faults with displacement only. In addition, a moderate water table gradient can result from fault displacement or a laterally continuous low permeability fault zone, but not from a high permeability fault zone, as others postulated earlier. Large-scale macrodispersion results from the vertical and lateral diversion of flow near the contact of high and low permeability layers at faults, and from upward flow within high permeability fault zones. Conversely, large-scale channeling can occur due to groundwater flow into areas with minimal fault displacement. Contaminants originating at the water table can flow in a direction significantly different than that of the water table gradient, and isolated
Energy Technology Data Exchange (ETDEWEB)
Gupta, S.K.; Cole, C.R.; Bond, F.W.
1979-12-01
The Assessment of Effectiveness of Geologic Isolation Systems (AEGIS) Program is developing and applying the methodology for assessing the far-field, long-term post-closure safety of deep geologic nuclear waste repositories. AEGIS is being performed by Pacific Northwest Laboratory (PNL) under contract with the Office of Nuclear Waste Isolation (OWNI) for the Department of Energy (DOE). One task within AEGIS is the development of methodology for analysis of the consequences (water pathway) from loss of repository containment as defined by various release scenarios. Analysis of the long-term, far-field consequences of release scenarios requires the application of numerical codes which simulate the hydrologic systems, model the transport of released radionuclides through the hydrologic systems to the biosphere, and, where applicable, assess the radiological dose to humans. Hydrologic and transport models are available at several levels of complexity or sophistication. Model selection and use are determined by the quantity and quality of input data. Model development under AEGIS and related programs provides three levels of hydrologic models, two levels of transport models, and one level of dose models (with several separate models). This document consists of the description of the FE3DGW (Finite Element, Three-Dimensional Groundwater) Hydrologic model third level (high complexity) three-dimensional, finite element approach (Galerkin formulation) for saturated groundwater flow.
Ur Rehman, Fiaz; Nadeem, Sohail; Ur Rehman, Hafeez; Ul Haq, Rizwan
2018-03-01
In the present paper a theoretical investigation is performed to analyze heat and mass transport enhancement of water-based nanofluid for three dimensional (3D) MHD stagnation-point flow caused by an exponentially stretched surface. Water is considered as a base fluid. There are three (3) types of nanoparticles considered in this study namely, CuO (Copper oxide), Fe3O4 (Magnetite), and Al2O3 (Alumina) are considered along with water. In this problem we invoked the boundary layer phenomena and suitable similarity transformation, as a result our three dimensional non-linear equations of describing current problem are transmuted into nonlinear and non-homogeneous differential equations involving ordinary derivatives. We solved the final equations by applying homotopy analysis technique. Influential outcomes of aggressing parameters involved in this study, effecting profiles of temperature field and velocity are explained in detail. Graphical results of involved parameters appearing in considered nanofluid are presented separately. It is worth mentioning that Skin-friction along x and y-direction is maximum for Copper oxide-water nanofluid and minimum for Alumina-water nanofluid. Result for local Nusselt number is maximum for Copper oxide-water nanofluid and is minimum for magnetite-water nanofluid.
Directory of Open Access Journals (Sweden)
Nicolai eKoebernick
2015-05-01
Full Text Available Split root experiments have the potential to disentangle water transport in roots and soil, enabling the investigation of the water uptake pattern of a root system. Interpretation of the experimental data assumes that water flow between the split soil compartments does not occur. Another approach to investigate root water uptake is by numerical simulations combining soil and root water flow depending on the parameterization and description of the root system. Our aim is to demonstrate the synergisms that emerge from combining split root experiments with simulations. We show how growing root architectures derived from temporally repeated X-ray CT scanning can be implemented in numerical soil-plant models. Faba beans were grown with and without split layers and exposed to a single drought period during which plant and soil water status were measured. Root architectures were reconstructed from CT scans and used in the model R-SWMS (root-soil water movement and solute transport to simulate water potentials in soil and roots in 3D as well as water uptake by growing roots in different depths. CT scans revealed that root development was considerably lower with split layers compared to without. This coincided with a reduction of transpiration, stomatal conductance and shoot growth. Simulated predawn water potentials were lower in the presence of split layers. Simulations showed that this was caused by an increased resistance to vertical water flow in the soil by the split layers. Comparison between measured and simulated soil water potentials proved that the split layers were not perfectly isolating and that redistribution of water from the lower, wetter compartments to the drier upper compartments took place, thus water losses were not equal to the root water uptake from those compartments. Still, the layers increased the resistance to vertical flow which resulted in lower simulated collar water potentials that led to reduced stomatal conductance and
Salama, Amgad
2014-08-25
Numerical simulation of flow and heat transfer in two adjacent channels is conducted with one of the channels partially blocked. This system simulates typical channels of a material testing reactor. The blockage is assumed due to the buckling of one of the channel plates inward along its width. The blockage ratio considered in this work is defined as the ratio between the cross-sectional area of the blocked and the unblocked channel. In this work, we consider a blockage ratio of approximately 40%. However, the blockage is different along the width of the channel, ranging from 0% at the end of the channel to 90% in the middle. The channel walls are sandwiching volumetric heat sources that vary spatially as chopped cosine functions. Interesting patterns are highlighted and investigated. The reduction in the flow area of one channel results in the flow redistributing among the two channels according to the changes in their hydraulic conductivities. The results of the numerical simulations show that the maximum wall temperature in the blocked channel is well below the boiling temperature at the operating pressure.
Speetjens, Michel; Demissie, Esubalew; Metcalfe, Guy; Clercx, Herman
2014-11-01
Laminar inline mixing is key to many industrial systems. However, insight into fundamental transport phenomena in case of 3D conditions and fluid inertia remains limited. This is studied for inline mixers with a cylindrical geometry. Said effects introduce three key features absent in simplified configurations: smooth transition between mixing cells; local upstream flow; symmetry breaking. Topological considerations imply a net throughflow region strictly separated from possible internal regions. The Lagrangian dynamics in this region admits representation by a 2D time-periodic Hamiltonian system. This establishes one fundamental kinematic structure for the present class of inline-mixing flows and implies universal behavior. All states follow from Hamiltonian breakdown of one common integrable state. Period-doubling bifurcation is the only way to eliminate transport barriers originating from the integrable state and thus necessary for global chaos. Important in a practical context is that a common simplification, i.e. cell-wise developed Stokes flow, retains these fundamental kinematic properties and deviates from the 3D inertial case essentially only in a quantitative sense. This substantiates its suitability for (at least first exploratory) studies on mixing properties. Dutch Technology Foundation Grant STW 11054.
Directory of Open Access Journals (Sweden)
Sang Soon Hwang
2008-03-01
Full Text Available Modeling and simulation for heat and mass transport in micro channel are beingused extensively in researches and industrial applications to gain better understanding of thefundamental processes and to optimize fuel cell designs before building a prototype forengineering application. In this study, we used a single-phase, fully three dimensionalsimulation model for PEMFC that can deal with both anode and cathode flow field forexamining the micro flow channel with electrochemical reaction. The results show thathydrogen and oxygen were solely supplied to the membrane by diffusion mechanism ratherthan convection transport, and the higher pressure drop at cathode side is thought to becaused by higher flow rate of oxygen at cathode. And it is found that the amount of water incathode channel was determined by water formation due to electrochemical reaction pluselectro-osmotic mass flux directing toward the cathode side. And it is very important tomodel the back diffusion and electro-osmotic mass flux accurately since the two flux wasclosely correlated each other and greatly influenced for determination of ionic conductivityof the membrane which directly affects the performance of fuel cell.
Lee, Pil Hyong; Han, Sang Seok; Hwang, Sang Soon
2008-03-03
Modeling and simulation for heat and mass transport in micro channel are beingused extensively in researches and industrial applications to gain better understanding of thefundamental processes and to optimize fuel cell designs before building a prototype forengineering application. In this study, we used a single-phase, fully three dimensionalsimulation model for PEMFC that can deal with both anode and cathode flow field forexamining the micro flow channel with electrochemical reaction. The results show thathydrogen and oxygen were solely supplied to the membrane by diffusion mechanism ratherthan convection transport, and the higher pressure drop at cathode side is thought to becaused by higher flow rate of oxygen at cathode. And it is found that the amount of water incathode channel was determined by water formation due to electrochemical reaction pluselectro-osmotic mass flux directing toward the cathode side. And it is very important tomodel the back diffusion and electro-osmotic mass flux accurately since the two flux wasclosely correlated each other and greatly influenced for determination of ionic conductivityof the membrane which directly affects the performance of fuel cell.
Allouche, M H; Millet, S; Botton, V; Henry, D; Ben Hadid, H; Rousset, F
2015-12-01
Squire's theorem, which states that the two-dimensional instabilities are more dangerous than the three-dimensional instabilities, is revisited here for a flow down an incline, making use of numerical stability analysis and Squire relationships when available. For flows down inclined planes, one of these Squire relationships involves the slopes of the inclines. This means that the Reynolds number associated with a two-dimensional wave can be shown to be smaller than that for an oblique wave, but this oblique wave being obtained for a larger slope. Physically speaking, this prevents the possibility to directly compare the thresholds at a given slope. The goal of the paper is then to reach a conclusion about the predominance or not of two-dimensional instabilities at a given slope, which is of practical interest for industrial or environmental applications. For a Newtonian fluid, it is shown that, for a given slope, oblique wave instabilities are never the dominant instabilities. Both the Squire relationships and the particular variations of the two-dimensional wave critical curve with regard to the inclination angle are involved in the proof of this result. For a generalized Newtonian fluid, a similar result can only be obtained for a reduced stability problem where some term connected to the perturbation of viscosity is neglected. For the general stability problem, however, no Squire relationships can be derived and the numerical stability results show that the thresholds for oblique waves can be smaller than the thresholds for two-dimensional waves at a given slope, particularly for large obliquity angles and strong shear-thinning behaviors. The conclusion is then completely different in that case: the dominant instability for a generalized Newtonian fluid flowing down an inclined plane with a given slope can be three dimensional.
Three-dimensional simulation of vortex breakdown
Kuruvila, G.; Salas, M. D.
1990-01-01
The integral form of the complete, unsteady, compressible, three-dimensional Navier-Stokes equations in the conservation form, cast in generalized coordinate system, are solved, numerically, to simulate the vortex breakdown phenomenon. The inviscid fluxes are discretized using Roe's upwind-biased flux-difference splitting scheme and the viscous fluxes are discretized using central differencing. Time integration is performed using a backward Euler ADI (alternating direction implicit) scheme. A full approximation multigrid is used to accelerate the convergence to steady state.
International Nuclear Information System (INIS)
Töger, Johannes; Carlsson, Marcus; Söderlind, Gustaf; Arheden, Håkan; Heiberg, Einar
2011-01-01
Functional and morphological changes of the heart influence blood flow patterns. Therefore, flow patterns may carry diagnostic and prognostic information. Three-dimensional, time-resolved, three-directional phase contrast cardiovascular magnetic resonance (4D PC-CMR) can image flow patterns with unique detail, and using new flow visualization methods may lead to new insights. The aim of this study is to present and validate a novel visualization method with a quantitative potential for blood flow from 4D PC-CMR, called Volume Tracking, and investigate if Volume Tracking complements particle tracing, the most common visualization method used today. Eight healthy volunteers and one patient with a large apical left ventricular aneurysm underwent 4D PC-CMR flow imaging of the whole heart. Volume Tracking and particle tracing visualizations were compared visually side-by-side in a visualization software package. To validate Volume Tracking, the number of particle traces that agreed with the Volume Tracking visualizations was counted and expressed as a percentage of total released particles in mid-diastole and end-diastole respectively. Two independent observers described blood flow patterns in the left ventricle using Volume Tracking visualizations. Volume Tracking was feasible in all eight healthy volunteers and in the patient. Visually, Volume Tracking and particle tracing are complementary methods, showing different aspects of the flow. When validated against particle tracing, on average 90.5% and 87.8% of the particles agreed with the Volume Tracking surface in mid-diastole and end-diastole respectively. Inflow patterns in the left ventricle varied between the subjects, with excellent agreement between observers. The left ventricular inflow pattern in the patient differed from the healthy subjects. Volume Tracking is a new visualization method for blood flow measured by 4D PC-CMR. Volume Tracking complements and provides incremental information compared to particle
Directory of Open Access Journals (Sweden)
S. S. Motsa
2010-01-01
Full Text Available The numerical solution of magnetohydrodynamic (MHD and rotating flow over a porous shrinking sheet is obtained by the new approach known as spectral homotopy analysis method (SHAM. Using a similarity transformation, the governing equations for the momentum are reduced to a set of ordinary differential equations and are solved by the SHAM approach to determine velocity distributions and shear stress variations for different governing parameters. The SHAM results are analysed and validated against numerical results obtained using MATLAB's built-in bvp4c routine, and good agreement is observed.
Viscous heating in fluids with temperature-dependent viscosity: implications for magma flows
Directory of Open Access Journals (Sweden)
A. Costa
2003-01-01
Full Text Available Viscous heating plays an important role in the dynamics of fluids with strongly temperature-dependent viscosity because of the coupling between the energy and momentum equations. The heat generated by viscous friction produces a local temperature increase near the tube walls with a consequent decrease of the viscosity which may dramatically change the temperature and velocity profiles. These processes are mainly controlled by the Peclét number, the Nahme number, the flow rate and the thermal boundary conditions. The problem of viscous heating in fluids was investigated in the past for its practical interest in the polymer industry, and was invoked to explain some rheological behaviours of silicate melts, but was not completely applied to study magma flows. In this paper we focus on the thermal and mechanical effects caused by viscous heating in tubes of finite lengths. We find that in magma flows at high Nahme number and typical flow rates, viscous heating is responsible for the evolution from Poiseuille flow, with a uniform temperature distribution at the inlet, to a plug flow with a hotter layer near the walls. When the temperature gradients induced by viscous heating are very pronounced, local instabilities may occur and the triggering of secondary flows is possible. For completeness, this paper also describes magma flow in infinitely long tubes both at steady state and in transient phase.
Arakane, S.; Mizoshiri, M.; Sakurai, J.; Hata, S.
2017-05-01
We have demonstrated the fabrication of two types of thermal flow sensors with Cu-rich and Cu2O-rich microheaters using femtosecond laser-induced reduction of CuO nanoparticles. The microheaters in the shape of microbridge structures were formed to thermally isolate from the substrates by four layer-by-layer laminations of two-dimensional micropatterns. First, we evaluated the patterning properties such as dispensing coating conditions and degree of reduction for the selective fabrication of three-dimensional Cu-rich and Cu2O-rich microstructures. Then, a hot-film flow sensor with a Cu-rich microheater and a calorimetric flow sensor with a Cu2O-rich microheater were fabricated using their respective appropriate laser irradiation conditions. The hot-film sensor with the Cu-rich microbridge single heater enabled us to measure the flow rate in a wide range of 0-450 cc min-1. Although a large temperature dependence of the Cu2O-rich microbridge heaters caused a large error for the hot-film flow sensors with single heaters, they showed higher heat-resistance and generated heat with a lower drive power. The temperature coefficient of resistance of the Cu2O-rich microstructures had a semiconductor-like large absolute value and was less than -4.6 × 10-8 °C-1. The higher temperature sensitivity of the Cu2O-rich microstructures was useful for thermal detection. Based on these advantages, a calorimetric flow sensor composed of the Cu2O-rich microbridge single heater and two Cu2O-rich thermal detectors was proposed and fabricated. The calorimetric flow sensor was driven by a circuit for measuring the temperature difference. The Cu2O-rich flow sensor could detect bi-directional flow with a small output error.
Jamieson, E. C.; Rennie, C. D.; Townsend, R. D.
2009-05-01
Stream barbs (a type of submerged groyne or spur dike) are low-profile linear rock structures that prevent the erosion of stream banks by redirecting high velocity flow away from the bank. Stream barbs are becoming a popular method for stream bank protection as they can be built at a relatively low cost and provide added ecological benefit. The design and construction of stream barbs in Sawmill Creek, a small urban stream in the city of Ottawa, Canada, will serve as a demonstration project for the use of barbs as a bank stabilization technique that will contribute to the rehabilitation of urban creeks while reducing erosion threats to property and infrastructure. As well as providing bank protection, these structures promote vegetated stream banks, create resting pools and scour holes for fish habitat, and increase bio-diversity for aquatic species. Despite these benefits, stream barbs are not a common means of stream bank protection in Canada, due largely to a lack of suitable design guidelines. The overall goal of stream habitat restoration in incising channel systems should be to accelerate natural processes of channel equilibrium recovery, riparian re-vegetation, and stream-floodplain interaction. Incorporating stream barbs, instead of traditional bank protection measures, attempts to achieve these goals. A three-dimensional numerical model: 'Simulation in Intakes with Multiblock option' (SSIIM), was used to model the effects of placing a series of stream barbs along an unstable section of Sawmill Creek. The average bankfull depth, width, and discharge of the creek are 1.2 m, 7.5 m, and 9 m3/s respectively. The model was used to assess various design alternatives for a series of seven stream barbs at two consecutive channel bends requiring stabilization measures along their outer banks. Design criteria were principally based on the reduction of velocity, shear stress and subsequent erosion at the outside bank of each bend, and on the relocation of a new thalweg
Energy Technology Data Exchange (ETDEWEB)
Yassin Hassan
2001-11-30
Develop a state-of-the-art non-intrusive diagnostic tool to perform simultaneous measurements of both the temporal and three-dimensional spatial velocity of the two phases of a bubbly flow. These measurements are required to provide a foundation for studying the constitutive closure relations needed in computational fluid dynamics and best-estimate thermal hydraulic codes employed in nuclear reactor safety analysis and severe accident simulation. Such kinds of full-field measurements are not achievable through the commonly used point-measurement techniques, such as hot wire, conductance probe, laser Doppler anemometry, etc. The results can also be used in several other applications, such as the dynamic transport of pollutants in water or studies of the dispersion of hazardous waste.
International Nuclear Information System (INIS)
Aizaki, Hideki; Nagamori, Seishi; Matsuda, Mami; Kawakami, Hayato; Hashimoto, Osamu; Ishiko, Hiroaki; Kawada, Masaaki; Matsuura, Tomokazu; Hasumura, Satoshi; Matsuura, Yoshiharu; Suzuki, Tetsuro; Miyamura, Tatsuo
2003-01-01
Lack of efficient culture systems for hepatitis C virus (HCV) has been a major obstacle in HCV research. Human liver cells grown in a three-dimensional radial-flow bioreactor were successfully infected following inoculation with plasma from an HCV carrier. Subsequent detection of increased HCV RNA suggested viral replication. Furthermore, transfection of HCV RNA transcribed from full-length cDNA also resulted in the production and release of HCV virions into supernatant. Infectivity was shown by successful secondary passage to a new culture. Introduction of mutations in RNA helicase and polymerase regions of HCV cDNA abolished virus replication, indicating that reverse genetics of this system is possible. The ability to replicate and detect the extracellular release of HCV might provide clues with regard to the persistent nature of HCV infection. It will also accelerate research into the pathogenicity of HCV, as well as the development of prophylactic agents and new therapy
International Nuclear Information System (INIS)
Yassin Hassan
2001-01-01
Develop a state-of-the-art non-intrusive diagnostic tool to perform simultaneous measurements of both the temporal and three-dimensional spatial velocity of the two phases of a bubbly flow. These measurements are required to provide a foundation for studying the constitutive closure relations needed in computational fluid dynamics and best-estimate thermal hydraulic codes employed in nuclear reactor safety analysis and severe accident simulation. Such kinds of full-field measurements are not achievable through the commonly used point-measurement techniques, such as hot wire, conductance probe, laser Doppler anemometry, etc. The results can also be used in several other applications, such as the dynamic transport of pollutants in water or studies of the dispersion of hazardous waste
Directory of Open Access Journals (Sweden)
S. Bilal
Full Text Available Present work is communicated to identify characteristics of magnetohydrodynamic (MHD three dimensional boundary layer flow of Williamson fluid confined by a bidirectional stretched surface. Conductivity of working fluid is assumed to be temperature dependent. Generative/absorptive heat transfer is also taken into account. Mathematical model is formulated in the form of partial expressions and then transmuted into ordinary differential equations with the help of newfangled set of similarity transformations. The resulting non-linear differential system of equations is solved numerically with the aid of Runge-Kutta algorithm supported by shooting method. Flow features are exemplified quantitatively through graphs. Scintillating results for friction factor and convective heat transfer are computed and scrutinized tabularly. Furthermore, the accuracy of present results is tested with existing literature and we found an excellent agreement. It is inferred that velocity along x-direction mounts whereas along y-direction depreciates for incrementing values of stretching ratio parameter. Moreover, it is also elucidated that non-linearity index tends to decrement the velocity and thermal distributions of fluid flow. Keywords: MHD flow, Williamson fluid, Variable thermal conductivity, Heat absorption/generation, Bidirectional non-linear stretching
Three dimensional system integration
Papanikolaou, Antonis; Radojcic, Riko
2010-01-01
Three-dimensional (3D) integrated circuit (IC) stacking is the next big step in electronic system integration. It enables packing more functionality, as well as integration of heterogeneous materials, devices, and signals, in the same space (volume). This results in consumer electronics (e.g., mobile, handheld devices) which can run more powerful applications, such as full-length movies and 3D games, with longer battery life. This technology is so promising that it is expected to be a mainstream technology a few years from now, less than 10-15 years from its original conception. To achieve thi
Three-dimensional metamaterials
Burckel, David Bruce [Albuquerque, NM
2012-06-12
A fabrication method is capable of creating canonical metamaterial structures arrayed in a three-dimensional geometry. The method uses a membrane suspended over a cavity with predefined pattern as a directional evaporation mask. Metallic and/or dielectric material can be evaporated at high vacuum through the patterned membrane to deposit resonator structures on the interior walls of the cavity, thereby providing a unit cell of micron-scale dimension. The method can produce volumetric metamaterial structures comprising layers of such unit cells of resonator structures.
International Nuclear Information System (INIS)
Stadlbauer, Andreas; Riet, Wilma van der; Crelier, Gerard; Salomonowitz, Erich
2010-01-01
Purpose: To assess the feasibility and potential limitations of the acceleration techniques SENSE and k-t BLAST for time-resolved three-dimensional (3D) velocity mapping of aortic blood flow. Furthermore, to quantify differences in peak velocity versus heart phase curves. Materials and methods: Time-resolved 3D blood flow patterns were investigated in eleven volunteers and two patients suffering from aortic diseases with accelerated PC-MR sequences either in combination with SENSE (R = 2) or k-t BLAST (6-fold). Both sequences showed similar data acquisition times and hence acceleration efficiency. Flow-field streamlines were calculated and visualized using the GTFlow software tool in order to reconstruct 3D aortic blood flow patterns. Differences between the peak velocities from single-slice PC-MRI experiments using SENSE 2 and k-t BLAST 6 were calculated for the whole cardiac cycle and averaged for all volunteers. Results: Reconstruction of 3D flow patterns in volunteers revealed attenuations in blood flow dynamics for k-t BLAST 6 compared to SENSE 2 in terms of 3D streamlines showing fewer and less distinct vortices and reduction in peak velocity, which is caused by temporal blurring. Solely by time-resolved 3D MR velocity mapping in combination with SENSE detected pathologic blood flow patterns in patients with aortic diseases. For volunteers, we found a broadening and flattering of the peak velocity versus heart phase diagram between the two acceleration techniques, which is an evidence for the temporal blurring of the k-t BLAST approach. Conclusion: We demonstrated the feasibility of SENSE and detected potential limitations of k-t BLAST when used for time-resolved 3D velocity mapping. The effects of higher k-t BLAST acceleration factors have to be considered for application in 3D velocity mapping.
Bilal, S.; Khalil-ur-Rehman; Malik, M. Y.; Hussain, Arif; Khan, Mair
Present work is communicated to identify characteristics of magnetohydrodynamic (MHD) three dimensional boundary layer flow of Williamson fluid confined by a bidirectional stretched surface. Conductivity of working fluid is assumed to be temperature dependent. Generative/absorptive heat transfer is also taken into account. Mathematical model is formulated in the form of partial expressions and then transmuted into ordinary differential equations with the help of newfangled set of similarity transformations. The resulting non-linear differential system of equations is solved numerically with the aid of Runge-Kutta algorithm supported by shooting method. Flow features are exemplified quantitatively through graphs. Scintillating results for friction factor and convective heat transfer are computed and scrutinized tabularly. Furthermore, the accuracy of present results is tested with existing literature and we found an excellent agreement. It is inferred that velocity along x-direction mounts whereas along y-direction depreciates for incrementing values of stretching ratio parameter. Moreover, it is also elucidated that non-linearity index tends to decrement the velocity and thermal distributions of fluid flow.
Energy Technology Data Exchange (ETDEWEB)
West, O.R.; Toran, L.E.
1994-04-01
Modeling the movement of hazardous waste in groundwater was identified by the US Department of Energy (DOE) as one of the grand challenges in scientific computation. In recognition of this need, DOE has provided support for a group of scientists from several national laboratories and universities to conduct research and development in groundwater flow and contaminant transport modeling. This group is part of a larger consortium of researchers, collectively referred to as the Partnership in Computational Science (PICS), that has been charged with the task of applying high-performance computational tools and techniques to grand challenge areas identified by DOE. One of the goals of the PICS Groundwater Group is to develop a new three-dimensional groundwater flow and transport code that is optimized for massively parallel computers. An existing groundwater flow code, 3DFEMWATER, was parallelized in order to serve as a benchmark for these new models. The application of P-FEM, the parallelized version of 3DFEMWATER, to a real field site is the subject of this report.
International Nuclear Information System (INIS)
West, O.R.; Toran, L.E.
1994-04-01
Modeling the movement of hazardous waste in groundwater was identified by the US Department of Energy (DOE) as one of the grand challenges in scientific computation. In recognition of this need, DOE has provided support for a group of scientists from several national laboratories and universities to conduct research and development in groundwater flow and contaminant transport modeling. This group is part of a larger consortium of researchers, collectively referred to as the Partnership in Computational Science (PICS), that has been charged with the task of applying high-performance computational tools and techniques to grand challenge areas identified by DOE. One of the goals of the PICS Groundwater Group is to develop a new three-dimensional groundwater flow and transport code that is optimized for massively parallel computers. An existing groundwater flow code, 3DFEMWATER, was parallelized in order to serve as a benchmark for these new models. The application of P-FEM, the parallelized version of 3DFEMWATER, to a real field site is the subject of this report
Energy Technology Data Exchange (ETDEWEB)
Takeuchi, Ryo; Katayama, Shigenori; Takeda, Naoya; Fujita, Katsuzo [Nishi-Kobe Medical Center (Japan); Yonekura, Yoshiharu [Fukui Medical Univ., Matsuoka (Japan); Konishi, Junji [Kyoto Univ. (Japan). Graduate School of Medicine
2003-03-01
The previously reported three-dimensional stereotaxic region of interest (ROI) template (3DSRT-t) for the analysis of anatomically standardized technetium-99m-L,L-ethyl cysteinate dimer ({sup 99m}Tc-ECD) single photon emission computed tomography (SPECT) images was modified for use in a fully automated regional cerebral blood flow (rCBF) quantification software, 3DSRT, incorporating an anatomical standardization engine transplanted from statistical parametric mapping 99 and ROIs for quantification based on 3DSRT-t. Three-dimensional T{sub 2}-weighted magnetic resonance images of 10 patients with localized infarcted areas were compared with the ROI contour of 3DSRT, and the positions of the central sulcus in the primary sensorimotor area were also estimated. All positions of the 20 lesions were in strict accordance with the ROI delineation of 3DSRT. The central sulcus was identified on at least one side of 210 paired ROIs and in the middle of 192 (91.4%) of these 210 paired ROIs among the 273 paired ROIs of the primary sensorimotor area. The central sulcus was recognized in the middle of more than 71.4% of the ROIs in which the central sulcus was identifiable in the respective 28 slices of the primary sensorimotor area. Fully automated accurate ROI delineation on anatomically standardized images is possible with 3DSRT, which enables objective quantification of rCBF and vascular reserve in only a few minutes using {sup 99m}Tc-ECD SPECT images obtained by the resting and vascular reserve (RVR) method. (author)
International Nuclear Information System (INIS)
Takeuchi, Ryo; Katayama, Shigenori; Takeda, Naoya; Fujita, Katsuzo; Yonekura, Yoshiharu; Konishi, Junji
2003-01-01
The previously reported three-dimensional stereotaxic region of interest (ROI) template (3DSRT-t) for the analysis of anatomically standardized technetium-99m-L,L-ethyl cysteinate dimer ( 99m Tc-ECD) single photon emission computed tomography (SPECT) images was modified for use in a fully automated regional cerebral blood flow (rCBF) quantification software, 3DSRT, incorporating an anatomical standardization engine transplanted from statistical parametric mapping 99 and ROIs for quantification based on 3DSRT-t. Three-dimensional T 2 -weighted magnetic resonance images of 10 patients with localized infarcted areas were compared with the ROI contour of 3DSRT, and the positions of the central sulcus in the primary sensorimotor area were also estimated. All positions of the 20 lesions were in strict accordance with the ROI delineation of 3DSRT. The central sulcus was identified on at least one side of 210 paired ROIs and in the middle of 192 (91.4%) of these 210 paired ROIs among the 273 paired ROIs of the primary sensorimotor area. The central sulcus was recognized in the middle of more than 71.4% of the ROIs in which the central sulcus was identifiable in the respective 28 slices of the primary sensorimotor area. Fully automated accurate ROI delineation on anatomically standardized images is possible with 3DSRT, which enables objective quantification of rCBF and vascular reserve in only a few minutes using 99m Tc-ECD SPECT images obtained by the resting and vascular reserve (RVR) method. (author)
Numerical simulation of energy equation with viscous dissipation for compressible flow over cones
International Nuclear Information System (INIS)
Asif, M.; Chughtai, I.R.
1998-01-01
A finite volume discretization technique has been used to solve the energy equation with viscous dissipation. The effects of viscous heat dissipation for Mach numbers 1.5 and 2.0, at an angle of attack of 0 degree, over sharp and blunt cones have been studied. Algebraic equations have been solved using line-by-line Tda method. Supersonic flow over cones has been analyzed and discussed with and without considering the viscous dissipation effects. It has been found that the effects of viscous dissipation increase with the increase in Mach number. Viscous dissipation affects the temperature distribution of the body. However, the temperature difference in these cases was insignificant. This may be due to the fact that these analysis have been done at 0 km altitude. (author)
Thermosolutal MHD flow and radiative heat transfer with viscous ...
African Journals Online (AJOL)
porous plate in a chemically active fluid with radiative heat transfer in the presence of viscous work and heat source. The resulting nonlinear dimensionless equations are solved by asymptotic analysis technique giving approximate analytic solutions for the steady velocity, temperature and concentration. The parameters ...
McDonald, James G.; Groth, Clinton P. T.
2013-09-01
The ability to predict continuum and transition-regime flows by hyperbolic moment methods offers the promise of several advantages over traditional techniques. These methods offer an extended range of physical validity as compared with the Navier-Stokes equations and can be used for the prediction of many non-equilibrium flows with a lower expense than particle-based methods. Also, the hyperbolic first-order nature of the resulting partial differential equations leads to mathematical and numerical advantages. Moment equations generated through an entropy-maximization principle are particularly attractive due to their apparent robustness; however, their application to practical situations involving viscous, heat-conducting gases has been hampered by several issues. Firstly, the lack of closed-form expressions for closing fluxes leads to numerical expense as many integrals of distribution functions must be computed numerically during the course of a flow computation. Secondly, it has been shown that there exist physically realizable moment states for which the entropy-maximizing problem on which the method is based cannot be solved. Following a review of the theory surrounding maximum-entropy moment closures, this paper shows that both of these problems can be addressed in practice, at least for a simplified one-dimensional gas, and that the resulting flow predictions can be surprisingly good. The numerical results described provide significant motivations for the extension of these ideas to the fully three-dimensional case.
Energy Technology Data Exchange (ETDEWEB)
Le Corre, Jean-Marie, E-mail: lecorrjm@westinghouse.co [Westinghouse Electric Sweden AB, 72163 Vaesteras (Sweden); Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213 (United States); Yao, Shi-Chune [Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213 (United States); Amon, Cristina H. [Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213 (United States); Faculty of Applied Science and Engineering, University of Toronto, Toronto, ON M5S 1A4 (Canada)
2010-02-15
Based on a review of visual observations at or near critical heat flux (CHF) under subcooled flow boiling conditions and consideration of CHF triggering mechanisms, presented in a companion paper [Le Corre, J.M., Yao, S.C., Amon, C.H., 2010. Two-phase flow regimes and mechanisms of critical heat flux under subcooled flow boiling conditions. Nucl. Eng. Des.], a model using a two-dimensional transient thermal analysis of the heater undergoing nucleation was developed to mechanistically predict CHF in the case of a bubbly flow regime. The model simulates the spatial and temporal heater temperature variations during nucleation at the wall, accounting for the stochastic nature of the boiling phenomena. It is postulated that a high local wall superheat occurring underneath a nucleating bubble at the time of bubble departure can prevent wall rewetting at CHF (Leidenfrost effect). The model has also the potential to evaluate the post-DNB heater temperature up to the point of heater melting. Validation of the proposed model was performed using detailed measured wall boiling parameters near CHF, thereby bypassing most needed constitutive relations. It was found that under limiting nucleation conditions; a peak wall temperature at the time of bubble departure can be reached at CHF preventing wall cooling by quenching. The simulations show that the resulting dry patch can survive the surrounding quenching events, preventing further nucleation and leading to a fast heater temperature increase. The model was applied at CHF conditions in simple geometry coupled with one-dimensional and three-dimensional (CFD) codes. It was found that, within the range where CHF occurs under bubbly flow conditions (as defined in Le Corre et al., 2010), the local wall superheat underneath nucleating bubbles is predicted to reach the Leidenfrost temperature. However, a better knowledge of statistical variations in wall boiling parameters would be necessary to correctly capture the CHF trends with
Directory of Open Access Journals (Sweden)
Arheden Håkan
2011-04-01
Full Text Available Abstract Background Functional and morphological changes of the heart influence blood flow patterns. Therefore, flow patterns may carry diagnostic and prognostic information. Three-dimensional, time-resolved, three-directional phase contrast cardiovascular magnetic resonance (4D PC-CMR can image flow patterns with unique detail, and using new flow visualization methods may lead to new insights. The aim of this study is to present and validate a novel visualization method with a quantitative potential for blood flow from 4D PC-CMR, called Volume Tracking, and investigate if Volume Tracking complements particle tracing, the most common visualization method used today. Methods Eight healthy volunteers and one patient with a large apical left ventricular aneurysm underwent 4D PC-CMR flow imaging of the whole heart. Volume Tracking and particle tracing visualizations were compared visually side-by-side in a visualization software package. To validate Volume Tracking, the number of particle traces that agreed with the Volume Tracking visualizations was counted and expressed as a percentage of total released particles in mid-diastole and end-diastole respectively. Two independent observers described blood flow patterns in the left ventricle using Volume Tracking visualizations. Results Volume Tracking was feasible in all eight healthy volunteers and in the patient. Visually, Volume Tracking and particle tracing are complementary methods, showing different aspects of the flow. When validated against particle tracing, on average 90.5% and 87.8% of the particles agreed with the Volume Tracking surface in mid-diastole and end-diastole respectively. Inflow patterns in the left ventricle varied between the subjects, with excellent agreement between observers. The left ventricular inflow pattern in the patient differed from the healthy subjects. Conclusion Volume Tracking is a new visualization method for blood flow measured by 4D PC-CMR. Volume Tracking
Role of viscous dissipation in the dynamics of lava flows with power-law rheology
Piombo, A.; Dragoni, M.
2011-09-01
We model a lava flow as a one-dimensional flow of a pseudoplastic fluid with viscous dissipation. The flow is horizontally unbounded and is driven downslope by the gravity force. We consider a power-law constitutive equation and we take into account the temperature dependence of the rheological parameters. Given an effusion rate and an initial temperature at the eruption vent, the flow is assumed to cool down by heat radiation. We calculate the heat produced by viscous dissipation as a function of lava temperature and effusion rate. The cooling rate is calculated as a function of the surface temperature and flow rate. Viscous dissipation reduces the cooling rate by an amount which is independent of flow rate. We evaluate the effect of viscous dissipation on the flow thickness and velocity. The effect of dissipation is to decrease the flow thickness and to increase the flow velocity. The effect on flow thickness is greater for smaller flow rates, while the effect on velocity is greater for larger effusion rates. In principle, the model provides a method for estimating the flow rate from in-field measurements of distances and temperatures.
Hill, M. C.; Belcher, W. R.; Sweetkind, D. S.; Faunt, C.
2014-12-01
The Death Valley regional groundwater flow system encompasses a proposed site for a high-level nuclear waste repository of the United States of America, the Nevada National Security Site (NNSS), where nuclear weapons were tested, and National Park and BLM properties, and provides water for local communities. The model was constructed using a three-dimensional hydrogeologic framework and has been used as a resource planning mechanism by the many stakeholders involved, including four United States (U.S) federal agencies (U.S. Department of Energy, National Park Service, Bureau of Land Management, and U.S. Fish and Wildlife Service) and local counties, towns, and residents. One of the issues in recent model development is simulation of insufficient water to regional discharge areas which form springs in valleys near the center of the system. Given what seems to be likely rock characteristics and geometries at depth, insufficient water is simulated to reach the discharge areas. This "surprise" thus challenges preconceived notions about the system. Here we use the hydrogeologic model to hypothesize alternatives able to produce the observed flow and use the groundwater simulation to test the hypotheses with other available data. Results suggest that the transmissivity measurements need to be used carefully because wells in this system are never fully penetrating, that multiple alternatives are able to produce the springflow, and that one most likely alternative cannot be identified given available data. Consequences of the alternatives are discussed.
Flow dynamical behavior and performance of a micro viscous pump with unequal inlet and outlet areas
Directory of Open Access Journals (Sweden)
Chenhui Hu
2016-01-01
Full Text Available The micro viscous pump is an important type of fluidic device. Optimizing the working performance of the pump is crucial for its wider application. A micro viscous pump design with unequal inlet and outlet areas is proposed in this paper. The flow field of the viscous pump is investigated using 2D laminar simulations. The mass flow rate and driving power are studied with different opening angles. The effects of the Reynolds number and the pressure load on the working performance are discussed in detail. Flow structures and vortex evolution are analyzed. With larger inlet and outlet areas, a higher mass flow rate is obtained and less driving power is achieved. A high pressure load results in a reduction in mass flow rate and an increase in driving power. Pumps with large opening angles are more susceptive to the Reynolds number and the pressure load. The adverse impact of the pressure load can be reduced by increasing the rotor speed. The vortex structure is affected by the geometric and operating parameters in the flow field. The flow dynamical behavior of the viscous pump exerts significant influence on its pumping ability. The present work gives rise to performance improvements for the micro viscous pump.
Kordilla, J.; Bresinsky, L. T.
2017-12-01
The physical mechanisms that govern preferential flow dynamics in unsaturated fractured rock formations are complex and not well understood. Fracture intersections may act as an integrator of unsaturated flow, leading to temporal delay, intermittent flow and partitioning dynamics. In this work, a three-dimensional Pairwise-Force Smoothed Particle Hydrodynamics (PF-SPH) model is being applied in order to simulate gravity-driven multiphase flow at synthetic fracture intersections. SPH, as a meshless Lagrangian method, is particularly suitable for modeling deformable interfaces, such as three-phase contact dynamics of droplets, rivulets and free-surface films. The static and dynamic contact angle can be recognized as the most important parameter of gravity-driven free-surface flow. In SPH, surface tension and adhesion naturally emerges from the implemented pairwise fluid-fluid (sff) and solid-fluid (ssf) interaction force. The model was calibrated to a contact angle of 65°, which corresponds to the wetting properties of water on Poly(methyl methacrylate). The accuracy of the SPH simulations were validated against an analytical solution of Poiseuille flow between two parallel plates and against laboratory experiments. Using the SPH model, the complex flow mode transitions from droplet to rivulet flow of an experimental study were reproduced. Additionally, laboratory dimensionless scaling experiments of water droplets were successfully replicated in SPH. Finally, SPH simulations were used to investigate the partitioning dynamics of single droplets into synthetic horizontal fractures with various apertures (Δdf = 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0 mm) and offsets (Δdoff = -1.5, -1.0, -0.5, 0, 1.0, 2.0, 3.0 mm). Fluid masses were measured in the domains R1, R2 and R3. The perfect conditions of ideally smooth surfaces and the SPH inherent advantage of particle tracking allow the recognition of small scale partitioning mechanisms and its importance for bulk flow
SLIPPER PERFORMANCE INVESTIGATION IN AXIAL PISTON PUMPS AND MOTORS-FLOW AND VISCOUS POWER LOSSES
Directory of Open Access Journals (Sweden)
A. Osman KURBAN
1997-01-01
Full Text Available In this study, the slippers being the most effective on the performance of swash plate type axial piston pumps and motors, which is a good example of hydrodynamic-hydrostatic bearing applications, have been investigated. With respect to this, having derived the viscous moment loss, viscous flow leakage loss and power loss equations, the variations of these parameters under different operating conditions have been examined experimentally.
Qin, J. J.; Jones, M.; Shiota, T.; Greenberg, N. L.; Firstenberg, M. S.; Tsujino, H.; Zetts, A. D.; Sun, J. P.; Cardon, L. A.; Odabashian, J. A.;
2000-01-01
AIM: The aim of this study was to investigate the feasibility and accuracy of using symmetrically rotated apical long axis planes for the determination of left ventricular (LV) volumes with real-time three-dimensional echocardiography (3DE). METHODS AND RESULTS: Real-time 3DE was performed in six sheep during 24 haemodynamic conditions with electromagnetic flow measurements (EM), and in 29 patients with magnetic resonance imaging measurements (MRI). LV volumes were calculated by Simpson's rule with five 3DE methods (i.e. apical biplane, four-plane, six-plane, nine-plane (in which the angle between each long axis plane was 90 degrees, 45 degrees, 30 degrees or 20 degrees, respectively) and standard short axis views (SAX)). Real-time 3DE correlated well with EM for LV stroke volumes in animals (r=0.68-0.95) and with MRI for absolute volumes in patients (r-values=0.93-0.98). However, agreement between MRI and apical nine-plane, six-plane, and SAX methods in patients was better than those with apical four-plane and bi-plane methods (mean difference = -15, -18, -13, vs. -31 and -48 ml for end-diastolic volume, respectively, Pmeasurement methods of real-time 3DE correlated well with reference standards for calculating LV volumes. Balancing accuracy and required time for these LV volume measurements, the apical six-plane method is recommended for clinical use.
Numerical simulations of heat transfer in an annular fuel channel with three-dimensional spacer ribs set up periodically under a fully developed turbulent flow
International Nuclear Information System (INIS)
Takase, Kazuyuki; Akino, Norio
1996-06-01
Thermal-hydraulic characteristics of an annular fuel channel with spacer ribs for high temperature gas-cooled reactors were analyzed numerically by three-dimensional heat transfer computations under a fully developed turbulent flow. The two-equations κ-ε turbulence model was applied to the present turbulent analysis. In particular, the κ-ε turbulence model constants and the turbulent Prandtl number were improved from the previous standard values proposed by Jones and Launder in order to obtain heat transfer predictions with higher accuracy. Consequently, heat transfer coefficients and friction factors in the spacer-ribbed fuel channel were predicted with sufficient accuracy in the range of Reynolds number exceeding 3000. It was clarified quantitatively from the present study that main mechanism for the heat transfer augmentation in the spacer-ribbed fuel channel was combined effects of the turbulence promoter effect by the spacer ribs and the velocity acceleration effect by a reduction in the channel cross-section. (author)
Shyam, Vikram; Ameri, Ali; Luk, Daniel F.; Chen, Jen-Ping
2010-01-01
Unsteady three-dimensional RANS simulations have been performed on a highly loaded transonic turbine stage and results are compared to steady calculations as well as experiment. A low Reynolds number k- turbulence model is employed to provide closure for the RANS system. A phase-lag boundary condition is used in the periodic direction. This allows the unsteady simulation to be performed by using only one blade from each of the two rows. The objective of this paper is to study the effect of unsteadiness on rotor heat transfer and to glean any insight into unsteady flow physics. The role of the stator wake passing on the pressure distribution at the leading edge is also studied. The simulated heat transfer and pressure results agreed favorably with experiment. The time-averaged heat transfer predicted by the unsteady simulation is higher than the heat transfer predicted by the steady simulation everywhere except at the leading edge. The shock structure formed due to stator-rotor interaction was analyzed. Heat transfer and pressure at the hub and casing were also studied. Thermal segregation was observed that leads to the heat transfer patterns predicted by steady and unsteady simulations to be different.
Three dimensional energy profile:
International Nuclear Information System (INIS)
Kowsari, Reza; Zerriffi, Hisham
2011-01-01
The provision of adequate, reliable, and affordable energy has been considered as a cornerstone of development. More than one-third of the world's population has a very limited access to modern energy services and suffers from its various negative consequences. Researchers have been exploring various dimensions of household energy use in order to design strategies to provide secure access to modern energy services. However, despite more than three decades of effort, our understanding of household energy use patterns is very limited, particularly in the context of rural regions of the developing world. Through this paper, the past and the current trends in the field of energy analysis are investigated. The literature on rural energy and energy transition in developing world has been explored and the factors affecting households' decisions on energy use are listed. The and the factors affecting households' decisions on energy use are listed. The gaps identified in the literature on rural household energy analysis provide a basis for developing an alternative model that can create a more realistic view of household energy use. The three dimensional energy profile is presented as a new conceptual model for assessment of household energy use. This framework acts as a basis for building new theoretical and empirical models of rural household energy use. - Highlights: ► Reviews literature on household energy, energy transitions and decision-making in developing countries. ► Identifies gaps in rural household energy analysis and develops a new conceptual framework. ► The 3-d energy profile provides a holistic view of household energy system characteristics. ► Illustrates the use of the framework for understanding household energy transitions.
Three-dimensional echocardiography
International Nuclear Information System (INIS)
Buck, Thomas
2011-01-01
Presents tips and tricks for beginners and experts Provides educational material for 3D training courses Features comprehensively illustrated cases Includes an accompanying DVD with video clips of all sample cases Three-dimensional echocardiography is the most recent fundamental advancement in echocardiography. Since real-time 3D echocardiography became commercially available in 2002, it has rapidly been accepted in echo labs worldwide. This book covers all clinically relevant aspects of this fascinating new technology, including a comprehensive explanation of its basic principles, practical aspects of clinical application, and detailed descriptions of specific uses in the broad spectrum of clinically important heart disease. The book was written by a group of well-recognized international experts in the field, who have not only been involved in the scientific and clinical evolution of 3D echocardiography since its inception but are also intensively involved in expert training courses. As a result, the clear focus of this book is on the practical application of 3D echocardiography in daily clinical routine with tips and tricks for both beginners and experts, accompanied by more than 150 case examples comprehensively illustrated in more than 800 images and more than 500 videos provided on a DVD. In addition to an in-depth review of the most recent literature on real-time 3D echocardiography, this book represents an invaluable reference work for beginners and expert users of 3D echocardiography. - Tips and tricks for beginners and experts - Educational material for 3D training courses - Comprehensively illustrated cases - DVD with video clips of all sample cases.
Ibrahim, Wubshet
2018-03-01
This article numerically examines three dimensional boundary layer flow of a rotating Powell-Eyring nanofluid. In modeling heat transfer processes, non-Fourier heat flux theory and for mass transfer non-Fick's mass flux theory are employed. This theory is recently re-initiated and it becomes the active research area to resolves some drawback associated with the famous Fourier heat flux and mass flux theory. The mathematical model of the flow problem is a system of non-linear partial differential equations which are obtained using the boundary layer analysis. The non-linear partial differential equations have been transformed into non-linear high order ordinary differential equations using similarity transformation. Employing bvp4c algorithm from matlab software routine, the numerical solution of the transformed ordinary differential equations is obtained. The governing equations are constrained by parameters such as rotation parameter λ , the non-Newtonian parameter N, dimensionless thermal relaxation and concentration relaxation parameters δt and δc . The impacts of these parameters have been discussed thoroughly and illustrated using graphs and tables. The findings show that thermal relaxation time δt reduces the thermal and concentration boundary layer thickness. Further, the results reveal that the rotational parameter λ has the effect of decreasing the velocity boundary layer thickness in both x and y directions. Further examination pinpoints that the skin friction coefficient along x-axis is an increasing and skin friction coefficient along y-axis is a decreasing function of rotation parameter λ . Furthermore, the non-Newtonian fluid parameter N has the characteristic of reducing the amount of local Nusselt numbers -f″ (0) and -g″ (0) both in x and y -directions.
Caldwell, Joanne N; Matsuda-Nakamura, Mayumi; Taylor, Nigel A S
2016-02-01
The inter-relationships between mean body and local skin temperatures have previously been established for controlling hand and foot blood flows. Since glabrous skin contains many arteriovenous anastomoses, it was important to repeat those experiments on non-glabrous regions using the same sample and experimental conditions. Mild hypothermia (mean body temperature 31.4 °C), normothermia (control: 36.0 °C) and moderate hyperthermia (38.3 °C) were induced and clamped (climate chamber and water-perfusion garment) in eight males. Within each condition, five localised thermal treatments (5, 15, 25, 33, 40 °C) were applied to the left forearm and right calf. Steady-state forearm and calf blood flows were measured (venous occlusion plethysmography) for each of the resulting 15 combinations of clamped mean body and local skin temperatures. Under the normothermic clamp, cutaneous blood flows averaged 4.2 mL 100 mL(-1) min(-1) (±0.28: forearm) and 5.4 mL 100 mL(-1) min(-1) (±0.27: calf). When mildly hypothermic, these segments were unresponsive to localised thermal stimuli, but tracked those changes when normothermic and moderately hyperthermic. For deep-body (oesophageal) temperature elevations, forearm blood flow increased by 5.1 mL 100 mL(-1) min(-1) °C(-1) (±0.9) relative to normothermia, while the calf was much less responsive: 3.3 mL 100 mL(-1) min(-1) °C(-1) (±1.5). Three-dimensional surfaces revealed a qualitative divergence in the control of calf blood flow, with vasoconstrictor tone apparently being released more gradually. These descriptions reinforce the importance of deep-tissue temperatures in controlling cutaneous perfusion, with this modulation being non-linear at the forearm and appearing linear for the calf.
Viscous flow behavior and workability of Mg-Cu-(Ag)-Gd bulk metallic glasses
International Nuclear Information System (INIS)
Chang, Y.C.; Huang, J.C.; Tang, C.W.; Chang, C.I.; Jang, J.S.C.
2008-01-01
The thermomechanical properties and viscous flow behaviors of the Mg 65 Cu 25-x Ag x Gd 10 (x=0, 3, 10at%, namely, Mg 65 Cu 25 Gd 10 , Mg 65 Cu 22 Ag 3 Gd 10 , and Mg 65 Cu 15 Ag 10 Gd 10 ) bulk metallic glasses in the supercooled viscous region under the loading condition were investigated using the thermomechanical analyzer. In this study, the supercooled viscous temperature windows, the minimum viscosity, the fragility parameter, and the deformability parameter would all be degraded with increasing Ag addition, leading to the negative factors for the micro-forming and nano-imprinting practices. The base Mg 65 Cu 25 Gd 10 alloy appears to be more promising than the Ag containing alloys when the viscous forming is under consideration. (author)
Numerical solution of inviscid and viscous laminar and turbulent flow around the airfoil
Directory of Open Access Journals (Sweden)
Slouka Martin
2016-01-01
Full Text Available This work deals with the 2D numerical solution of inviscid compressible flow and viscous compressible laminar and turbulent flow around the profile. In a case of turbulent flow algebraic Baldwin-Lomax model is used and compared with Wilcox k-omega model. Calculations are done for NACA 0012 and RAE 2822 airfoil profile for the different angles of upstream flow. Numerical results are compared and discussed with experimental data.
Numerical solution of inviscid and viscous laminar and turbulent flow around the airfoil
Slouka, Martin; Kozel, Karel
2016-03-01
This work deals with the 2D numerical solution of inviscid compressible flow and viscous compressible laminar and turbulent flow around the profile. In a case of turbulent flow algebraic Baldwin-Lomax model is used and compared with Wilcox k-omega model. Calculations are done for NACA 0012 and RAE 2822 airfoil profile for the different angles of upstream flow. Numerical results are compared and discussed with experimental data.
Three-dimensional ICT reconstruction
International Nuclear Information System (INIS)
Zhang Aidong; Li Ju; Chen Fa; Sun Lingxia
2005-01-01
The three-dimensional ICT reconstruction method is the hot topic of recent ICT technology research. In the context, qualified visual three-dimensional ICT pictures are achieved through multi-piece two-dimensional images accumulation by, combining with thresholding method and linear interpolation. Different direction and different position images of the reconstructed pictures are got by rotation and interception respectively. The convenient and quick method is significantly instructive to more complicated three-dimensional reconstruction of ICT images. (authors)
Three-dimensional ICT reconstruction
International Nuclear Information System (INIS)
Zhang Aidong; Li Ju; Chen Fa; Sun Lingxia
2004-01-01
The three-dimensional ICT reconstruction method is the hot topic of recent ICT technology research. In the context qualified visual three-dimensional ICT pictures are achieved through multi-piece two-dimensional images accumulation by order, combining with thresholding method and linear interpolation. Different direction and different position images of the reconstructed pictures are got by rotation and interception respectively. The convenient and quick method is significantly instructive to more complicated three-dimensional reconstruction of ICT images. (authors)
Numerical Simulation of 3D Viscous MHD Flows
National Research Council Canada - National Science Library
Golovachov, Yurii P; Kurakin, Yurii A; Schmidt, Alexander A; Van Wie, David M
2003-01-01
.... Flows in hypersonic intakes are considered. Preliminary results showed that local MHD interaction in the inlet part of the intake model was the most effective for control over plasma flow field...
Improved numerical methods for turbulent viscous flows aerothermal modeling program, phase 2
Karki, K. C.; Patankar, S. V.; Runchal, A. K.; Mongia, H. C.
1988-01-01
The details of a study to develop accurate and efficient numerical schemes to predict complex flows are described. In this program, several discretization schemes were evaluated using simple test cases. This assessment led to the selection of three schemes for an in-depth evaluation based on two-dimensional flows. The scheme with the superior overall performance was incorporated in a computer program for three-dimensional flows. To improve the computational efficiency, the selected discretization scheme was combined with a direct solution approach in which the fluid flow equations are solved simultaneously rather than sequentially.
Viscous shock layer solutions for turbulent flow of radiating gas mixtures in chemical equilibrium
Anderson, E. C.; Moss, J. N.
1975-01-01
The viscous shock layer equations for hypersonic laminar and turbulent flows of radiating or nonradiating gas mixtures in chemical equilibrium are presented for two-dimensional and axially symmetric flow fields. Solutions are obtained using an implicit finite difference scheme and results are presented for hypersonic flow over spherically blunted cone configurations at free stream conditions representative of entry into the atmosphere of Venus. These data are compared with solutions obtained using other methods of analysis.
Viscous-shock-layer solutions for turbulent flow of radiating gas mixtures in chemical equilibrium
Anderson, E. C.; Moss, J. N.
1975-01-01
The viscous-shock-layer equations for hypersonic laminar and turbulent flows of radiating or nonradiating gas mixtures in chemical equilibrium are presented for two-dimensional and axially-symmetric flow fields. Solutions were obtained using an implicit finite-difference scheme and results are presented for hypersonic flow over spherically-blunted cone configurations at freestream conditions representative of entry into the atmosphere of Venus. These data are compared with solutions obtained using other methods of analysis.
Viscous flow solutions for slender bodies of revolution at incidence
Vatsa, Veer N.
1991-01-01
Flow over slender prolate spheroids at incidence is examined. The incidence angle is chosen high enough to cause streamwise separation of the flow in addition to crossflow separation generally observed at lower incidence angles. The freestream Mach number for the cases investigated here is subsonic, thus precluding the use of parabolized procedures. Laminar, transitional and turbulent flow cases are investigated.
Theory of viscous transonic flow over airfoils at high Reynolds number
Melnik, R. E.; Chow, R.; Mead, H. R.
1977-01-01
This paper considers viscous flows with unseparated turbulent boundary layers over two-dimensional airfoils at transonic speeds. Conventional theoretical methods are based on boundary layer formulations which do not account for the effect of the curved wake and static pressure variations across the boundary layer in the trailing edge region. In this investigation an extended viscous theory is developed that accounts for both effects. The theory is based on a rational analysis of the strong turbulent interaction at airfoil trailing edges. The method of matched asymptotic expansions is employed to develop formal series solutions of the full Reynolds equations in the limit of Reynolds numbers tending to infinity. Procedures are developed for combining the local trailing edge solution with numerical methods for solving the full potential flow and boundary layer equations. Theoretical results indicate that conventional boundary layer methods account for only about 50% of the viscous effect on lift, the remaining contribution arising from wake curvature and normal pressure gradient effects.
Directory of Open Access Journals (Sweden)
S. Srinivas
2016-01-01
Full Text Available The present work investigates the effects of thermal-diffusion and diffusion-thermo on MHD flow of viscous fluid between expanding or contracting rotating porous disks with viscous dissipation. The partial differential equations governing the flow problem under consideration have been transformed by a similarity transformation into a system of coupled nonlinear ordinary differential equations. An analytical approach, namely the homotopy analysis method is employed in order to obtain the solutions of the ordinary differential equations. The effects of various emerging parameters on flow variables have been discussed numerically and explained graphically. Comparison of the HAM solutions with the numerical solutions is performed.
Deformation and transport of micro-fibers and helices in viscous flows
Lindner, Anke
Fluid-structure interactions between flexible objects and viscous flows are, to a large extent, governed by the shape of the flexible object. Using microfabrication methods, we obtain complex ``particles'' in fiber and helix form with perfect control not only over the material properties, but also the particle geometry. We then perform an experimental study on the deformation and transport of these particles in microfluidic flows. Fibers are shown to drift laterally in confined flows due to the transport anisotropy of the elongated object. When these fibers interact with lateral walls, complex dynamics are observed, such as fiber oscillation. Fiber flexibility modifies these dynamics. Flexible microhelices are easily stretched by a viscous flow and we characterize the overall shape as a function of the frictional properties. The deformation of these helices is well-described by non-linear finite extensibility. Due to the non-uniform distribution of the pitch of a helix subject to viscous drag, linear and nonlinear behavior is identified along the contour length of a single helix. When a polymer solution is used for the viscous flow, an interesting multiscale problem arises and the typical polymer size needs to be compared not only to the global size of the helix, but also to the dimensions of the ribbon.
Anderson, B. H.; Putt, C. W.; Giamati, C. C.
1981-01-01
Color coding techniques used in the processing of remote sensing imagery were adapted and applied to the fluid dynamics problems associated with turbofan mixer nozzles. The computer generated color graphics were found to be useful in reconstructing the measured flow field from low resolution experimental data to give more physical meaning to this information and in scanning and interpreting the large volume of computer generated data from the three dimensional viscous computer code used in the analysis.
Topological Fluid Dynamics For Free and Viscous Surfaces
DEFF Research Database (Denmark)
Balci, Adnan
In an incompressible fluid flow, streamline patterns and their bifurcations are investigated close to wall for two-dimensional system and close to free and viscous surfaces in three-dimensional system. Expanding the velocity field in a Taylor series, we conduct a local analysis at the given...
Zhao, Y.; Lao, Liyun; Yeung, H.
2015-01-01
Slug flow characteristics in highly viscous liquid and gas flow are studied experimentally in a horizontal pipe with 0.074 m ID and 17 m length. Results of flow regime map, liquid holdup and pressure gradient are discussed and liquid viscosity effects are investigated. Applicable correlations which are developed to predict liquid holdup in slug body for low viscosity flow are assessed with high viscosity liquids. Furthermore, a mechanistic model is developed for predicting the characteristics...
Elbaz, M.S.M.M.
2016-01-01
Despite one might intuitively think that blood inflows inside the human heart in a straight path, direct imaging of cardiac blood flow showed that, actually, cardiac blood inflows in a swirling motion forming what is called vortex flow pattern. In fact, blood inflow forms a pair of counter-rotating
Interaction of high-speed compressible viscous flow and structure by adaptive finite element method
International Nuclear Information System (INIS)
Limtrakarn, Wiroj; Dechaumphai, Pramote
2004-01-01
Interaction behaviors of high-speed compressible viscous flow and thermal-structural response of structure are presented. The compressible viscous laminar flow behavior based on the Navier-Stokes equations is predicted by using an adaptive cell-centered finite-element method. The energy equation and the quasi-static structural equations for aerodynamically heated structures are solved by applying the Galerkin finite-element method. The finite-element formulation and computational procedure are described. The performance of the combined method is evaluated by solving Mach 4 flow past a flat plate and comparing with the solution from the finite different method. To demonstrate their interaction, the high-speed flow, structural heat transfer, and deformation phenomena are studied by applying the present method to Mach 10 flow past a flat plate
Three dimensional moire pattern alignment
Juday, Richard D. (Inventor)
1991-01-01
An apparatus is disclosed for determining three dimensional positioning relative to a predetermined point utilizing moire interference patterns such that the patterns are complementary when viewed on axis from the predetermined distance. Further, the invention includes means for determining rotational positioning in addition to three dimensional translational positioning.
Davis, Daniel R.
1997-01-01
Discusses the implications of the three-dimensional sign proposed by Harris (1990) for general linguistic theory and the philosophy of language. The article places the principal characteristics of the three-dimensional sign (contextuality, cotemporality, communicational relevance, and experiential grounding) against those of the two-dimensional…
Cross-coupling effects in chemically non-equilibrium viscous compressible flows
International Nuclear Information System (INIS)
Kustova, E.V.; Giordano, D.
2011-01-01
Graphical abstract: Self-cosistent kinetic-theory description of chemical-reaction rates and mean normal stress in one-temperature viscous compressible gas flows. Reaearch highlights: → In chemically non-equilibrium viscous compressible flows, the rate of each reaction depends on the velocity divergence and rates of all other reactions. → Cross effects between the rates of chemical reactions and normal mean stress can be found in the symmetric form and expressed in terms of the reaction affinities. → In the case of small affinities, the entropy production is unconditionally non-negative; in the case of finite affinities, the entropy production related to the scalar forces has no definite sign. - Abstract: A closed self-consistent description of a one-temperature non-equilibrium reacting flow is presented on the basis of the kinetic theory methods. A general case including internal degrees of freedom, dissociation-recombination and exchange reactions, and arbitrary values of affinities of chemical reactions is considered. Chemical-reaction rates and mean normal stress in viscous compressible flows are studied and a symmetric cross coupling between these terms is found. It is shown that the rate of each chemical reaction and the mean normal stress depend on velocity divergence and affinities of all chemical reactions; the law of mass action is violated in viscous flows. The results obtained in the frame of linear irreversible thermodynamics can be deduced from the proposed model for the particular case of small affinities. The reciprocal Onsager-Casimir relations are verified, the symmetry of kinetic coefficients is demonstrated, and the entropy production in a viscous flow is studied.
Stokes flow of micropolar fluid past a viscous fluid spheroid with non ...
Indian Academy of Sciences (India)
The Stokes axisymmetric flow of an incompressible micropolar fluid past a viscous fluid spheroid whose shape deviates slightly from that of a sphere is studied analytically. The boundary conditions used are the vanishing of the normal velocities, the continuity of the tangential velocities, continuity of shear stresses and ...
MHD flow and heat transfer of a viscous reacting fluid over a ...
African Journals Online (AJOL)
This paper presents a boundary layer flow analysis for a viscous, incompressible, electrically conducting reacting fluid over a stretching sheet in the presence of a magnetic field. It is shown that the Hartmann, Prandtl and the Eckert numbers have effect on the velocity and temperature fields. Journal of the Nigerian ...
Kruyt, Nicolaas P.; Cuvelier, C.; Segal, A.; van der Zanden, J.
1988-01-01
In this paper a total linearization method is derived for solving steady viscous free boundary flow problems (including capillary effects) by the finite element method. It is shown that the influence of the geometrical unknown in the totally linearized weak formulation can be expressed in terms of
MHD flow and heat transfer of a viscous reacting fluid over a ...
African Journals Online (AJOL)
... layer flow analysis for a viscous, incompressible, electrically conducting reacting fluid over a stretching sheet in the presence of a magnetic field. It is shown that the Hartmann, Prandtl and the Eckert numbers have effect on the velocity and temperature fields. Journal of the Nigerian Association of Mathematical Physics, ...
Two Experiments to Approach the Boltzmann Factor: Chemical Reaction and Viscous Flow
Fazio, Claudio; Battaglia, Onofrio R.; Guastella, Ivan
2012-01-01
In this paper we discuss a pedagogical approach aimed at pointing out the role played by the Boltzmann factor in describing phenomena usually perceived as regulated by different mechanisms of functioning. Experimental results regarding some aspects of a chemical reaction and of the viscous flow of some liquids are analysed and described in terms…
Czech Academy of Sciences Publication Activity Database
Deuring, P.; Kračmar, Stanislav; Nečasová, Šárka; Wittwer, P.
2015-01-01
Roč. 1, č. 2 (2015), s. 325-333 ISSN 2296-9020 R&D Projects: GA ČR GA16-03230S Institutional support: RVO:67985840 Keywords : whole space * viscous incompressible flow * rotating body Subject RIV: BA - General Mathematics http://www.orthogonal-editions.com/V1p231-418.pdf
Directory of Open Access Journals (Sweden)
Anna Maria Pellegrino
2017-12-01
Full Text Available This paper refers to complex granular-fluid mixtures involved into geophysical flows, such as debris and hyper-concentrated flows. For such phenomena, the interstitial fluids play a role when they are in the viscous regime. Referring to experiments on granular-fluid mixture carried out with pressure imposed annular shear cell, we study the rheological behaviour of dense mixture involving both spheres and irregular-shaped particles. For the case of viscous suspensions with irregular grains, a significant scatter of data from the trend observed for mixtures with spherical particles was evident. In effect, the shape of the particles likely plays a fundamental role in the flow dynamics, and the constitutive laws proposed by the frictional theory for the spheres are no longer valid. Starting from the frictional approach successfully applied to suspension of spheres, we demonstrate that also in case of irregular particles the mixture rheology may be fully characterized by the two relationships involving friction coefficient µ and volume concentration Ф as a function of the dimensionless viscous number Iv. To this goal, we provided a new consistent general model, referring to the volume fraction law and friction law, which accounts for the particle shape. In this way, the fitting parameters reduce just to the static friction angle µ1, and the two parameters, k and fs related to the grain shape. The resulting general model may apply to steady fully developed flows of saturated granular fluid mixture in the viscous regime, no matter of granular characteristics.
Practical application of viscous-flow calculations for the simulation of manoeuvring ships
Toxopeus, S.L.
2011-01-01
The present work was initiated in order to improve traditional manoeuvring simulations based on empirical equations to model the forces and moments on the ship. With the evolution of the capability of viscous-flow solvers to predict forces and moments on ships, it was decided to develop a practical
International Nuclear Information System (INIS)
Martin, A.; Alvarez, D.; Cases, F.; Stelletta, S.
1997-06-01
This report explains the last results about the mixing in the 900 MW PWR vessels. The accurate fluid flow transient, induced by the RCP starting-up, is represented. In a first time, we present the Thermalhydraulic Finite Element Code N3S used for the 3D numerical computations. After that, results obtained for one reactor operation case are given. This case is dealing with the transient mixing of a clear plug in the vessel when one primary pump starts-up. A comparison made between two injection modes; a steady state fluid flow conditions or the accurate RCP transient fluid flow conditions. The results giving the local minimum of concentration and the time response of the mean concentration at the core inlet are compared. The results show the real importance of the unsteadiness characteristics of the fluid flow transport of the clear water plug. (author)
Energy Technology Data Exchange (ETDEWEB)
Martin, A.; Alvarez, D.; Cases, F.; Stelletta, S. [Electricite de France (EDF), 78 - Chatou (France). Lab. National d`Hydraulique
1997-06-01
This report explains the last results about the mixing in the 900 MW PWR vessels. The accurate fluid flow transient, induced by the RCP starting-up, is represented. In a first time, we present the Thermalhydraulic Finite Element Code N3S used for the 3D numerical computations. After that, results obtained for one reactor operation case are given. This case is dealing with the transient mixing of a clear plug in the vessel when one primary pump starts-up. A comparison made between two injection modes; a steady state fluid flow conditions or the accurate RCP transient fluid flow conditions. The results giving the local minimum of concentration and the time response of the mean concentration at the core inlet are compared. The results show the real importance of the unsteadiness characteristics of the fluid flow transport of the clear water plug. (author) 12 refs.
Mixed convective flow of immiscible viscous fluids confined between ...
African Journals Online (AJOL)
The effect of these parameters on the physical characteristics such as Nusselt number and skin friction at the walls is studied. It is found that Grashof number, viscosity ratio and width ratio enhance the flow whereas, conductivity ratio reduces the flow. Rate of heat transfer and skin friction for varying parameters is also shown ...
Viscous dissipation effect on the flow through a horizontal porous ...
African Journals Online (AJOL)
It is observed that high Darcy number leads to a higher velocity and that velocity is parabolic while reversal flow takes place at low Darcy number, while at very low Darcy number, oscillation and instabilities of flow is observed. It is also observed that as the brinkman number increases the temperature profile increases.
Imaging unsteady three-dimensional transport phenomena
Indian Academy of Sciences (India)
2014-01-05
Jan 5, 2014 ... physical domains with unsteady processes can be accommodated. Optical methods promise to breach the holy grail of measurements by extracting unsteady three-dimensional data in applications related to transport phenomena. Keywords. Optical measurement; fluid flow and transport; refractive index ...
Directory of Open Access Journals (Sweden)
Mukesh Kumar Awasthi
2013-01-01
Full Text Available The instability of a thin sheet of viscous and dielectric liquid moving in the same direction as an air stream in the presence of a uniform horizontal electric field has been carried out using viscous potential flow theory. It is observed that aerodynamic-enhanced instability occurs if the Weber number is much less than a critical value related to the ratio of the air and liquid stream velocities, viscosity ratio of two fluids, the electric field, and the dielectric constant values. Liquid viscosity has stabilizing effect in the stability analysis, while air viscosity has destabilizing effect.
Energy Technology Data Exchange (ETDEWEB)
Bisht, Gautam; Huang, Maoyi; Zhou, Tian; Chen, Xingyuan; Dai, Heng; Hammond, Glenn E.; Riley, William J.; Downs, Janelle L.; Liu, Ying; Zachara, John M.
2017-01-01
A fully coupled three-dimensional surface and subsurface land model is developed and applied to a site along the Columbia River to simulate three-way interactions among river water, groundwater, and land surface processes. The model features the coupling of the Community Land Model version 4.5 (CLM4.5) and a massively parallel multiphysics reactive transport model (PFLOTRAN). The coupled model, named CP v1.0, is applied to a 400 m × 400 m study domain instrumented with groundwater monitoring wells along the Columbia River shoreline. CP v1.0 simulations are performed at three spatial resolutions (i.e., 2, 10, and 20 m) over a 5-year period to evaluate the impact of hydroclimatic conditions and spatial resolution on simulated variables. Results show that the coupled model is capable of simulating groundwater–river-water interactions driven by river stage variability along managed river reaches, which are of global significance as a result of over 30 000 dams constructed worldwide during the past half-century. Our numerical experiments suggest that the land-surface energy partitioning is strongly modulated by groundwater–river-water interactions through expanding the periodically inundated fraction of the riparian zone, and enhancing moisture availability in the vadose zone via capillary rise in response to the river stage change. Meanwhile, CLM4.5 fails to capture the key hydrologic process (i.e., groundwater–river-water exchange) at the site, and consequently simulates drastically different water and energy budgets. Furthermore, spatial resolution is found to significantly impact the accuracy of estimated the mass exchange rates at the boundaries of the aquifer, and it becomes critical when surface and subsurface become more tightly coupled with groundwater table within 6 to 7 meters below the surface. Inclusion of lateral subsurface flow influenced both the surface energy budget and subsurface transport processes as a result of river-water intrusion
Directory of Open Access Journals (Sweden)
G. Bisht
2017-12-01
Full Text Available A fully coupled three-dimensional surface and subsurface land model is developed and applied to a site along the Columbia River to simulate three-way interactions among river water, groundwater, and land surface processes. The model features the coupling of the Community Land Model version 4.5 (CLM4.5 and a massively parallel multiphysics reactive transport model (PFLOTRAN. The coupled model, named CP v1.0, is applied to a 400 m × 400 m study domain instrumented with groundwater monitoring wells along the Columbia River shoreline. CP v1.0 simulations are performed at three spatial resolutions (i.e., 2, 10, and 20 m over a 5-year period to evaluate the impact of hydroclimatic conditions and spatial resolution on simulated variables. Results show that the coupled model is capable of simulating groundwater–river-water interactions driven by river stage variability along managed river reaches, which are of global significance as a result of over 30 000 dams constructed worldwide during the past half-century. Our numerical experiments suggest that the land-surface energy partitioning is strongly modulated by groundwater–river-water interactions through expanding the periodically inundated fraction of the riparian zone, and enhancing moisture availability in the vadose zone via capillary rise in response to the river stage change. Meanwhile, CLM4.5 fails to capture the key hydrologic process (i.e., groundwater–river-water exchange at the site, and consequently simulates drastically different water and energy budgets. Furthermore, spatial resolution is found to significantly impact the accuracy of estimated the mass exchange rates at the boundaries of the aquifer, and it becomes critical when surface and subsurface become more tightly coupled with groundwater table within 6 to 7 meters below the surface. Inclusion of lateral subsurface flow influenced both the surface energy budget and subsurface transport processes as a result
Bisht, Gautam; Huang, Maoyi; Zhou, Tian; Chen, Xingyuan; Dai, Heng; Hammond, Glenn E.; Riley, William J.; Downs, Janelle L.; Liu, Ying; Zachara, John M.
2017-12-01
A fully coupled three-dimensional surface and subsurface land model is developed and applied to a site along the Columbia River to simulate three-way interactions among river water, groundwater, and land surface processes. The model features the coupling of the Community Land Model version 4.5 (CLM4.5) and a massively parallel multiphysics reactive transport model (PFLOTRAN). The coupled model, named CP v1.0, is applied to a 400 m × 400 m study domain instrumented with groundwater monitoring wells along the Columbia River shoreline. CP v1.0 simulations are performed at three spatial resolutions (i.e., 2, 10, and 20 m) over a 5-year period to evaluate the impact of hydroclimatic conditions and spatial resolution on simulated variables. Results show that the coupled model is capable of simulating groundwater-river-water interactions driven by river stage variability along managed river reaches, which are of global significance as a result of over 30 000 dams constructed worldwide during the past half-century. Our numerical experiments suggest that the land-surface energy partitioning is strongly modulated by groundwater-river-water interactions through expanding the periodically inundated fraction of the riparian zone, and enhancing moisture availability in the vadose zone via capillary rise in response to the river stage change. Meanwhile, CLM4.5 fails to capture the key hydrologic process (i.e., groundwater-river-water exchange) at the site, and consequently simulates drastically different water and energy budgets. Furthermore, spatial resolution is found to significantly impact the accuracy of estimated the mass exchange rates at the boundaries of the aquifer, and it becomes critical when surface and subsurface become more tightly coupled with groundwater table within 6 to 7 meters below the surface. Inclusion of lateral subsurface flow influenced both the surface energy budget and subsurface transport processes as a result of river-water intrusion into the
Supersonic Laminar Viscous Flow Past a Cone at Angle of Attack in Spinning and Coning Motion
Agarwal, Ramesh; Rakich, John V.
1982-01-01
Computational results obtained with a parabolic Navier-Stokes marching code are presented for supersonic viscous flow past a pointed cone at angle of attack undergoing a combined spinning and coning motion. The code takes into account the asymmetries in the flowfield resulting from the motion and computes the asymmetric shock shape, crossflow and streamwise shear, heat transfer, crossflow separation and vortex structure. The side force and moment are also computed. Reasonably good agreement is obtained with the side force measurements of Schiff and Tobak. Comparison is also made with the only available numerical inviscid analysis. It is found that the asymmetric pressure loads due lo coning motion are much larger than all other viscous forces due lo spin and coning, making viscous forces negligible in the combined motion.
Bistability of heat transfer of a viscous liquid under conditions of flow channel
International Nuclear Information System (INIS)
Melkikh, A.V.; Seleznev, V.D.
2001-01-01
The heat exchange model for a viscous liquid flowing under the pressure drop effect in a tube, surrounded by the medium with a lower temperature, is considered. It is shown that the system bistable behavior is possible by availability of the liquid viscosity exponential dependence on the temperature and by negligible dissipative heat release. The transitions between cold and hot flows in this case should proceed by a jump. The liquid and channel parameters, whereby the bistability may be observed, are determined [ru
Waves of pressure in viscous incompressible fluid
Prosviryakov, E. Yu.
2017-12-01
A three-dimensional non-stationary flow of a viscous incompressible fluid in the infinite space is examined. The description of possible shapes of pressure is based on the equation for the axial component of velocity, which is an exact consequence of the basic equations. New analytical exact solutions to the Navier-Stokes equations for periodic and localized traveling waves have been found.
Collective dynamics of particles from viscous to turbulent flows
2017-01-01
The book surveys the state-of-the-art methods that are currently available to model and simulate the presence of rigid particles in a fluid flow. For particles that are very small relative to the characteristic flow scales and move without interaction with other particles, effective equations of motion for particle tracking are formulated and applied (e.g. in gas-solid flows). For larger particles, for particles in liquid-solid flows and for particles that interact with each other or possibly modify the overall flow detailed model are presented. Special attention is given to the description of the approximate force coupling method (FCM) as a more general treatment for small particles, and derivations in the context of low Reynolds numbers for the particle motion as well as application at finite Reynolds numbers are provided. Other topics discussed in the book are the relation to higher resolution immersed boundary methods, possible extensions to non-spherical particles and examples of applications of such met...
Improvements of Critical Heat Flux Models Based on the Viscous Potential Flow Theory
International Nuclear Information System (INIS)
Kim, Byoung Jae; Lee, Jong Hyuk; Kim, Kyung Doo
2014-01-01
The absence of fluid viscosities in most existing models may be attributed to the fact that inviscid flow analyses are performed for the model development. For example, the hydrodynamic theory and macrolayer dryout models rely on the Rayleigh-Taylor, Kelvin-Helmholtz, and capillary instabilities for inviscid fluids. However, as the viscosities of two fluids become closer, none of them cannot be neglected. Moreover, the gas viscosity effect cannot be neglected on the condition that the gas layer is thin. Nevertheless, the previous studies neglected the viscous effect. Recently, Kim et al. showed that for the model development of critical heat flux and minimum film boiling, the Rayleigh-Taylor instability should be analyzed with a thin layer of viscous gas instead of a thick layer of inviscid gas. The decrease of the most unstable wavelength was shown to improve the prediction accuracy of critical heat flux models for various fluids, particularly at elevated pressures. In addition, the most dangerous wavelength and the most rapid growth rate for viscous thin films are shown to be applicable to the minimum heat flux condition. Kim et al. touch only the most unstable wavelength for developing critical heat flux models. The critical heat flux is inversely proportional to the square root of the most unstable wavelength (Zuber, Guan et al). Here, we notice that the existing critical heat flux models make use of the Kelvin-Helmholtz instability of inviscid flows. The Kelvin-Helmholtz instability determines the maximum vapor escape velocity (Zuber) and the initial liquid macrolayer thickness (Haramura and Katto). Therefore, there is a room for improving the prediction accuracy by the help of the Kelvin-Helmholtz instability of viscous fluids. The Kelvin-Helmholtz instability arises when the different fluid layers are in relative motion. Usually, a uniform flow is considered in each fluid layer, allowing a velocity discontinuity at the interface. Therefore, in general, the
Improved numerical methods for turbulent viscous recirculating flows
Turan, A.; Vandoormaal, J. P.
1988-01-01
The performance of discrete methods for the prediction of fluid flows can be enhanced by improving the convergence rate of solvers and by increasing the accuracy of the discrete representation of the equations of motion. This report evaluates the gains in solver performance that are available when various acceleration methods are applied. Various discretizations are also examined and two are recommended because of their accuracy and robustness. Insertion of the improved discretization and solver accelerator into a TEACH mode, that has been widely applied to combustor flows, illustrates the substantial gains to be achieved.
Numerical modelling of compressible viscous flow in turbine cascades
Louda, P.; Kozel, K.; Příhoda, J.
2014-03-01
The work deals with mathematical models of turbulent flow through turbine cascade in 2D and 3D. It is based on the Favre-averaged Navier-Stokes equations with SST or EARSM turbulence models. A two-equation model of transition to turbulence is considered too. The solution is obtained by implicit AUSM finite volume method. The 2D and 3D results are shown flow through the SE1050 cascade including simulation of a range of off-design angles of attack.
Mixed convective flow of immiscible viscous fluids confined between ...
African Journals Online (AJOL)
user
wavy channel was first treated analytically by Burns and Parks (1967), who expressed the stream function as a Fourier series under the assumption of Stokes flow. Following this, Goldstein and Sparrow (1977) were the first to use the naphthalene technique to measure local and average heat transfer coefficients in a ...
Numerical Simulation of 3D Viscous MHD Flows
National Research Council Canada - National Science Library
Golovachov, Yurii P; Kurakin, Yurii A; Schmidt, Alexander A; Van Wie, David M
2003-01-01
.... In such a case, 3D effects may be significant in the flow structure. The objective of the present paper is to investigate numerically the phenomena of shock wave interaction with boundary layer under the influence of the localised MHD effects.
Implicit time-accurate simulation of viscous flow
van Buuren, R.; Kuerten, Johannes G.M.; Geurts, Bernardus J.
2001-01-01
Implicit time integration was studied in the context of unsteady shock-boundary layer interaction flow. With an explicit second-order Runge-Kutta scheme, a reference solution to compare with the implicit second-order Crank-Nicolson scheme was determined. The time step in the explicit scheme is
Viscous dissipation effect on the flow of a thermodependent Herschel-Bulkley fluid
Directory of Open Access Journals (Sweden)
Labsi Nabila
2015-01-01
Full Text Available The present study concerns the numerical analysis of both hydrodynamic and thermal properties of a Herschel-Bulkley fluid flow in a pipe. The flow, which involves forced heat transfer convection, is steady and takes place within a pipe of circular cross section with uniform wall temperature. The Herschel-Bulkley model with the Papanastasiou regularization is used and flow index values of 1 and 1.5 are considered. The study focuses on the effect of neglecting both viscous dissipation and temperature dependence of the fluid consistency on its hydrodynamic and thermal properties. For that purpose, we investigate both wall heating (Br0 as well as the exponential temperature dependence of the consistency. The results show that neglecting both of these parameters results in more than a 50% underestimation of the heat transfer due to the viscous nature of this kind of fluid.
Karki, K. C.; Mongia, H. C.; Patankar, Suhas V.; Runchal, A. K.
1987-01-01
The objective of this effort is to develop improved numerical schemes for predicting combustor flow fields. Various candidate numerical schemes were evaluated, and promising schemes were selected for detailed assessment. The criteria for evaluation included accuracy, computational efficiency, stability, and ease of extension to multidimensions. The candidate schemes were assessed against a variety of simple one- and two-dimensional problems. These results led to the selection of the following schemes for further evaluation: flux spline schemes (linear and cubic) and controlled numerical diffusion with internal feedback (CONDIF). The incorporation of the flux spline scheme and direct solution strategy in a computer program for three-dimensional flows is in progress.
Stokes’ and Lamb's viscous drag laws
Eames, I.; Klettner, C. A.
2017-03-01
Since Galileo used his pulse to measure the time period of a swinging chandelier in the 17th century, pendulums have fascinated scientists. It was not until Stokes' (1851 Camb. Phil. Soc. 9 8-106) (whose interest was spurred by the pendulur time pieces of the mid 19th century) treatise on viscous flow that a theoretical framework for the drag on a sphere at low Reynolds number was laid down. Stokes' famous drag law has been used to determine two fundamental physical constants—the charge on an electron and Avogadro's constant—and has been used in theories which have won three Nobel prizes. Considering its illustrious history it is then not surprising that the flow past a sphere and its two-dimensional analog, the flow past a cylinder, form the starting point of teaching flow past a rigid body in undergraduate level fluid mechanics courses. Usually starting with the two-dimensional potential flow past a cylinder, students progress to the three-dimensional potential flow past a sphere. However, when the viscous flow past rigid bodies is taught, the three-dimensional example of a sphere is first introduced, and followed by (but not often), the two-dimensional viscous flow past a cylinder. The reason why viscous flow past a cylinder is generally not taught is because it is usually explained from an asymptotic analysis perspective. In fact, this added mathematical complexity is why the drag on a cylinder was only solved in 1911, 60 years after the drag on a sphere. In this note, we show that the viscous flow past a cylinder can be explained without the need to introduce any asymptotic analysis while still capturing all the physical insight of this classic fluid mechanics problem.
Flow of viscous fluid along an exponentially stretching curved surface
Directory of Open Access Journals (Sweden)
N.F. Okechi
Full Text Available In this paper, we present the boundary layer analysis of flow induced by rapidly stretching curved surface with exponential velocity. The governing boundary value problem is reduced into self-similar form using a new similarity transformation. The resulting equations are solved numerically using shooting and Runge-Kutta methods. The numerical results depicts that the fluid velocity as well as the skin friction coefficient increases with the surface curvature, similar trend is also observed for the pressure. The dimensionless wall shear stress defined for this problem is greater than that of a linearly stretching curved surface, but becomes comparably less for a surface stretching with a power-law velocity. In addition, the result for the plane surface is a special case of this study when the radius of curvature of the surface is sufficiently large. The numerical investigations presented in terms of the graphs are interpreted with the help of underlying physics of the fluid flow and the consequences arising from the curved geometry. Keywords: Boundary layer flow, Curved surface, Exponential stretching, Curvature
Kandula, M.; Pearce, D. G.
1991-01-01
A steady incompressible three-dimensional viscous flow analysis has been conducted for the Space Shuttle external tank/orbiter propellant feed line disconnect flapper valves with upstream elbows. The Navier-Stokes code, INS3D, is modified to handle interior obstacles and a simple turbulence model. The flow solver is tested for stability and convergence in the presence of interior flappers. An under-relaxation scheme has been incorporated to improve the solution stability. Important flow characteristics such as secondary flows, recirculation, vortex and wake regions, and separated flows are observed. Computed values for forces, moments, and pressure drop are in satisfactory agreement with water flow test data covering a maximum tube Reynolds number of 3.5 million. The predicted hydrodynamical stability of the flappers correlates well with the measurements.
Goal-oriented model adaptivity for viscous incompressible flows
van Opstal, T. M.
2015-04-04
© 2015, Springer-Verlag Berlin Heidelberg. In van Opstal et al. (Comput Mech 50:779–788, 2012) airbag inflation simulations were performed where the flow was approximated by Stokes flow. Inside the intricately folded initial geometry the Stokes assumption is argued to hold. This linearity assumption leads to a boundary-integral representation, the key to bypassing mesh generation and remeshing. It therefore enables very large displacements with near-contact. However, such a coarse assumption cannot hold throughout the domain, where it breaks down one needs to revert to the original model. The present work formalizes this idea. A model adaptive approach is proposed, in which the coarse model (a Stokes boundary-integral equation) is locally replaced by the original high-fidelity model (Navier–Stokes) based on a-posteriori estimates of the error in a quantity of interest. This adaptive modeling framework aims at taking away the burden and heuristics of manually partitioning the domain while providing new insight into the physics. We elucidate how challenges pertaining to model disparity can be addressed. Essentially, the solution in the interior of the coarse model domain is reconstructed as a post-processing step. We furthermore present a two-dimensional numerical experiments to show that the error estimator is reliable.
Fully developed viscous and viscoelastic flows in curved pipes
Fan, Yurun; Tanner, Roger I.; Phan-Thien, Nhan
2001-08-01
Some h-p finite element computations have been carried out to obtain solutions for fully developed laminar flows in curved pipes with curvature ratios from 0.001 to 0.5. An Oldroyd-3-constant model is used to represent the viscoelastic fluid, which includes the upper-convected Maxwell (UCM) model and the Oldroyd-B model as special cases. With this model we can examine separately the effects of the fluid inertia, and the first and second normal-stress differences. From analysis of the global torque and force balances, three criteria are proposed for this problem to estimate the errors in the computations. Moreover, the finite element solutions are accurately confirmed by the perturbation solutions of Robertson & Muller (1996) in the cases of small Reynolds/Deborah numbers.
Hypersonic Laminar Viscous Flow Past Spinning Cones at Angle of Attack
Agarwal, Ramesh; Rakich, John V.
1982-01-01
Computational results are presented for hypersonic viscous flow past spinning sharp and blunt cones of angle of attack, obtained with a parabolic Navier-Stokes marching code. The code takes into account the asymmetries in the flowfield resulting from spinning motion and computes the asymmetric shock shape, cross-flow and streamwise shear, heat transfer, cross-flow separation, and vortex structure. The Magnus force and moments are also computed. Comparisons are made with other theoretical analyses based on boundary-layer and boundary-region equations, and an anomaly is discovered in the displacement thickness contribution to the Magnus force when compared with boundary-layer results.
Viscous flow computations with the lattice-Boltzmann equation method
Yu, Dazhi
2002-09-01
The lattice Boltzmann equation (LBE) method is a kinetics-based approach for fluid flow computations, and it is amenable to parallel computing. Compared to the well-established Navier-Stokes (NS) approaches, critical issues remain with the LBE method, noticeably flexible spatial resolution, boundary treatments, and dispersion and relaxation time mode. Those issues are addressed in this dissertation with improved practice presented. At the formulation level, both the single-relaxation-time (SRT) and multiple-relaxation-time (MRT) models are analyzed. The SRT model involves no artificial parameters, with a constant relaxation time regulating the physical value of fluid viscosity. The MRT model allows different relaxation time scales for different variables. Computational assessment shows that the MRT model has advantages over the SRT model in maintaining stability, reducing the oscillation, and improving the convergence rate in the computation. A multi-block method is developed for both the SRT and MRT model to facilitate flexible spatial resolutions according to the flow structures. The formulae for information exchange at the interface between coarse and fine grids are derived to ensure the mass and momentum conservation while maintaining the second-order accuracy. A customized time matching between coarse and fine grids is also presented to ensure smooth exchange information. Results show that the multi-block method can greatly increase the computational efficiency of the LBE method without losing the accuracy. Two methods of force evaluation in LBE are examined: one based on stress integration on the solid boundary and the other momentum exchange between fluid and solid. The momentum exchange method is found to be simpler to implement while the integration of stress requires evaluation of the detailed surface geometry and extrapolation of stress-related variables to the same surface. The momentum exchange method performs better overall. Improved treatments for
A Gas-kinetic Discontinuous Galerkin Method for Viscous Flow Equations
International Nuclear Information System (INIS)
Liu, Hongwei; Xu, Kun
2007-01-01
This paper presents a Runge-Kutta discontinuous Galerkin (RKDG) method for viscous flow computation. The construction of the RKDG method is based on a gas-kinetic formulation, which not only couples the convective and dissipative terms together, but also includes both discontinuous and continuous representation in the flux evaluation at the cell interface through a simple hybrid gas distribution function. Due to the intrinsic connection between the gaskinetic BGK model and the Navier-Stokes equations, the Navier-Stokes flux is automatically obtained by the present method. Numerical examples for both one dimensional (10) and two dimensional(20) compressible viscous flows are presented to demonstrate the accuracy and shock capturing capability of the current RKDG method
On the research of flow around obstacle using the viscous Cartesian grid technique
Directory of Open Access Journals (Sweden)
Liu Yan-Hua
2012-01-01
Full Text Available A new 2-D viscous Cartesian grid is proposed in current research. It is a combination of the existent body-fitted grid and Cartesian grid technology. On the interface of the two different type of grid, a fined triangular mesh is used to connect the two grids. Tests with flow around the cylinder and aerofoil NACA0012 show that the proposed scheme is easy for implement with high accuracy.
Analysis of three-dimensional transonic compressors
Bourgeade, A.
1984-01-01
A method for computing the three-dimensional transonic flow around the blades of a compressor or of a propeller is given. The method is based on the use of the velocity potential, on the hypothesis that the flow is inviscid, irrotational and isentropic. The equation of the potential is solved in a transformed space such that the surface of the blade is mapped into a plane where the periodicity is implicit. This equation is in a nonconservative form and is solved with the help of a finite difference method using artificial time. A computer code is provided and some sample results are given in order to demonstrate the influence of three-dimensional effects and the blade's rotation.
Comparing two methods of simulating mirco-scale viscous flows in a porous channel
Gao, Hui; Han, Jie; Jin, Yan; Wang, Lian-Ping
2007-11-01
Water flows in natural soil porous media are important to colloid-facilitated transport of contaminants and other phenomena with groundwater as the carrier. The 3D micro-scale flow is complicated due to the complex geometry. The transport and deposition of colloids in such flows are affected by several physical and chemical forces involved. In this talk, we first compare two methods of simulating viscous flows in both 2D and 3D channels filled with glass-bead particles. The first method is Physalis developed by Prosperetti's group, at Johns Hopkins, based on solving the Navier-Stokes equation using a combination of numerical solution and local analytical Stokes flow representation. The second method is a meso-scale approach by solving a lattice Boltzmann equation. Specific implementation issues will be discussed. The two methods yield almost identical flows. Preliminary simulation results as well as parallel experimental results on colloid deposition in the porous channel will also be presented.
Flow harmonics from self-consistent particlization of a viscous fluid
Wolff, Zack; Molnar, Denes
2017-10-01
The quantitative extraction of quark-gluon plasma (QGP) properties from heavy-ion data, such as its specific shear viscosity η /s , typically requires comparison to viscous hydrodynamic or "hybrid" hydrodynamics + transport simulations. In either case, one has to convert the fluid to hadrons, yet without additional theory input the conversion is ambiguous for dissipative fluids. Here, shear viscous phase-space corrections calculated using linearized transport theory are applied in Cooper-Frye freeze-out to quantify the effects on anisotropic flow coefficients vn(pT) at the energies available at both the BNL Relativistic Heavy Ion Collider and the CERN Large Hadron Collider. Expanding upon our previous flow harmonics studies [D. Molnar and Z. Wolff, Phys. Rev. C 95, 024903 (2017), 10.1103/PhysRevC.95.024903; Z. Wolff and D. Molnar, J. Phys.: Conf. Ser. 535, 012020 (2014), 10.1088/1742-6596/535/1/012020], we calculate pion and proton v2(pT) , v4(pT) , and v6(pT) , but here we incorporate a hadron gas that is chemically frozen below a temperature of 175 MeV and use hypersurfaces from realistic viscous hydrodynamic simulations. For additive quark model cross sections and relative phase-space corrections with p3 /2 momentum dependence rather than the quadratic Grad form, we find at moderately high transverse momentum noticeably higher v4(pT) and v6(pT) for protons than for pions. In addition, the value of η /s deduced from elliptic flow data differs by nearly 50% from the value extracted using the naive "democratic Grad" form of freeze-out distributions. To facilitate the use of the self-consistent viscous corrections calculated here in hydrodynamic and hybrid calculations, we also present convenient parametrizations of the corrections for the various hadron species.
Energy Technology Data Exchange (ETDEWEB)
Ogawa, H.; Matsui, Y.; Kimura, S. [Nissan Motor Co. Ltd. Tokyo (Japan)
1997-10-01
To reduce the exhaust emissions and fuel consumption of direct-injection diesel engines, it is essential to optimize the fuel injection equipment closely related to combustion and emission characteristics. In this study, three-dimensional computation has been applied to investigate the effects of the injection nozzle specifications (e.g., sac volume, round shape at the inlet of the nozzle hole) and needle tip deviation on internal flow characteristics. The computational results revealed that the effects of the nozzle specifications and needle tip deviation with a smaller needle lift on internal flow characteristics and a general approach to optimize the injection nozzle specifications were obtained. 3 refs., 10 figs., 1 tab.
Computational modelling of the flow of viscous fluids in carbon nanotubes
International Nuclear Information System (INIS)
Khosravian, N; Rafii-Tabar, H
2007-01-01
Carbon nanotubes will have extensive application in all areas of nano-technology, and in particular in the field of nano-fluidics, wherein they can be used for molecular separation, nano-scale filtering and as nano-pipes for conveying fluids. In the field of nano-medicine, nanotubes can be functionalized with various types of receptors to act as bio-sensors for the detection and elimination of cancer cells, or be used as bypasses and even neural connections. Modelling fluid flow inside nanotubes is a very challenging problem, since there is a complex interplay between the motion of the fluid and the stability of the walls. A critical issue in the design of nano-fluidic devices is the induced vibration of the walls, due to the fluid flow, which can promote structural instability. It has been established that the resonant frequencies depend on the flow velocity. We have studied, for the first time, the flow of viscous fluids through multi-walled carbon nanotubes, using the Euler-Bernoulli classical beam theory to model the nanotube as a continuum structure. Our aim has been to compute the effect of the fluid flow on the structural stability of the nanotubes, without having to consider the details of the fluid-walls interaction. The variations of the resonant frequencies with the flow velocity are obtained for both unembedded nanotubes, and when they are embedded in an elastic medium. It is found that a nanotube conveying a viscous fluid is more stable against vibration-induced buckling than a nanotube conveying a non-viscous fluid, and that the aspect ratio plays the same role in both cases
Paul, Tanaji; Harimkar, Sandip P.
2017-07-01
The viscous flow behavior of Fe-based amorphous alloy powder during isochronal spark plasma sintering was analyzed under the integrated theoretical background of the Arrhenius and directional structural relaxation models. A relationship between viscous flow activation energy and heating rate was derived. An extension of the pertinent analysis to Ti-based amorphous alloys confirmed the broad applicability of such a relationship for predicting the activation energy for sintering below the glass transition temperature (T g) of the amorphous alloy powders.
Entropy resistance analyses of a two-stream parallel flow heat exchanger with viscous heating
International Nuclear Information System (INIS)
Cheng Xue-Tao; Liang Xin-Gang
2013-01-01
Heat exchangers are widely used in industry, and analyses and optimizations of the performance of heat exchangers are important topics. In this paper, we define the concept of entropy resistance based on the entropy generation analyses of a one-dimensional heat transfer process. With this concept, a two-stream parallel flow heat exchanger with viscous heating is analyzed and discussed. It is found that the minimization of entropy resistance always leads to the maximum heat transfer rate for the discussed two-stream parallel flow heat exchanger, while the minimizations of entropy generation rate, entropy generation numbers, and revised entropy generation number do not always. (general)
Sturdza, Peter (Inventor); Martins-Rivas, Herve (Inventor); Suzuki, Yoshifumi (Inventor)
2014-01-01
A fluid-flow simulation over a computer-generated surface is generated using a quasi-simultaneous technique. The simulation includes a fluid-flow mesh of inviscid and boundary-layer fluid cells. An initial fluid property for an inviscid fluid cell is determined using an inviscid fluid simulation that does not simulate fluid viscous effects. An initial boundary-layer fluid property a boundary-layer fluid cell is determined using the initial fluid property and a viscous fluid simulation that simulates fluid viscous effects. An updated boundary-layer fluid property is determined for the boundary-layer fluid cell using the initial fluid property, initial boundary-layer fluid property, and an interaction law. The interaction law approximates the inviscid fluid simulation using a matrix of aerodynamic influence coefficients computed using a two-dimensional surface panel technique and a fluid-property vector. An updated fluid property is determined for the inviscid fluid cell using the updated boundary-layer fluid property.
International Nuclear Information System (INIS)
Chee, Yi Shen; Ting, Tiew Wei; Hung, Yew Mun
2015-01-01
The effect of thermal asymmetrical boundaries on entropy generation of viscous dissipative flow of forced convection in thermal non-equilibrium porous media is analytically studied. The two-dimensional temperature, Nusselt number and entropy generation contours are analysed comprehensively to provide insights into the underlying physical significance of the effect on entropy generation. By incorporating the effects of viscous dissipation and thermal non-equilibrium, the first-law and second-law characteristics of porous-medium flow are investigated via various pertinent parameters, i.e. heat flux ratio, effective thermal conductivity ratio, Darcy number, Biot number and averaged fluid velocity. For the case of symmetrical wall heat flux, an optimum condition with a high Nusselt number and a low entropy generation is identified at a Darcy number of 10 −4 , providing an ideal operating condition from the second-law aspect. This type of heat and fluid transport in porous media covers a wide range of engineering applications, involving porous insulation, packed-bed catalytic process in nuclear reactors, filtration transpiration cooling, and modelling of transport phenomena of microchannel heat sinks. - Highlights: • Effects of thermal asymmetries on convection in porous-medium are studied. • Exergetic effectiveness of porous media with thermal asymmetries is investigated. • 2-D temperature, Nusselt number and entropy generation contours are analyzed. • Significance of viscous dissipation in entropy generation is scrutinized. • Significance of thermal non-equilibrium in entropy generation is studied
Directory of Open Access Journals (Sweden)
D.K. Tiwari
2015-09-01
Full Text Available A linear analysis of capillary instability of a cylindrical interface in the presence of axial magnetic field has been carried out when there is heat and mass transfer across the interface. Both fluids are taken as incompressible, viscous and magnetic with different kinematic viscosities and different magnetic permeabilities. Viscous potential flow theory is used for the investigation and a dispersion relation that accounts for the growth of axisymmetric waves is derived. Stability criterion is given by critical value of applied magnetic field as well as critical wave number and stability is discussed theoretically as well as numerically. Various graphs are drawn showing the effect of various physical parameters such as magnetic field strength, heat transfer capillary number, and permeability ratio, on the stability of the system. It has been observed that the axial magnetic field and heat and mass transfer both have stabilizing effect on the stability of the system.
International Nuclear Information System (INIS)
Belcher, W.R.; Faunt, C.C.; D'Agnese, F.A.
2002-01-01
The U.S. Geological Survey, in cooperation with the Department of Energy and other Federal, State, and local agencies, is evaluating the hydrogeologic characteristics of the Death Valley regional ground-water flow system. The ground-water flow system covers and area of about 100,000 square kilometers from latitude 35 degrees to 38 degrees 15 minutes North to longitude 115 degrees to 118 degrees West, with the flow system proper comprising about 45,000 square kilometers. The Death Valley regional ground-water flow system is one of the larger flow systems within the Southwestern United States and includes in its boundaries the Nevada Test Site, Yucca Mountain, and much of Death Valley. Part of this study includes the construction of a three-dimensional hydrogeologic framework model to serve as the foundation for the development of a steady-state regional ground-water flow model. The digital framework model provides a computer-based description of the geometry and composition of the hydro geologic units that control regional flow. The framework model of the region was constructed by merging two previous framework models constructed for the Yucca Mountain Project and the Environmental Restoration Program Underground Test Area studies at the Nevada Test Site. The hydrologic characteristics of the region result from a currently arid climate and complex geology. Interbasinal regional ground-water flow occurs through a thick carbonate-rock sequence of Paleozoic age, a locally thick volcanic-rock sequence of Tertiary age, and basin-fill alluvium of Tertiary and Quaternary age. Throughout the system, deep and shallow ground-water flow may be controlled by extensive and pervasive regional and local faults and fractures. The framework model was constructed using data from several sources to define the geometry of the regional hydrogeologic units. These data sources include (1) a 1:250,000-scale hydrogeologic-map compilation of the region; (2) regional-scale geologic cross
Finite element analysis of transient viscous flow with free surface using filling pattern technique
International Nuclear Information System (INIS)
Kim, Ki Don; Yang, Dong Yol; Jeong, Jun Ho
2001-01-01
The filling pattern technique based on the finite element method and Eulerian mesh advancement approach has been developed to analyze incompressible transient viscous flow with free surfaces. The governing equation for flow analysis is Navier-Stokes equation including inertia and gravity effects. The penalty and predictor-corrector methods are used effectively for finite element formulation. The flow front surface and the volume inflow rate are calculated using the filling pattern technique to select an adequate pattern among four filling patterns at each triangular control volume. Using the proposed numerical technique, the collapse of a dam has been analyzed to predict flow phenomenon of fluid and the predicted front positions versus time have been compared with the reported experimental result
The new high resolution method of Godunov`s type for 3D viscous flow calculations
Energy Technology Data Exchange (ETDEWEB)
Yershov, S.V.; Rusanov, A.V. [Ukranian National Academy of Sciences, Kahrkov (Ukraine)
1996-12-31
The numerical method is suggested for the calculations of the 3D viscous compressible flows described by the thin-layer Reynolds-averaged Navier-Stokes equations. The method is based on the Godunov`s finite-difference scheme and it uses the ENO reconstruction suggested by Harten to achieve the uniformly high-order accuracy. The computational efficiency is provided with the simplified multi grid approach and the implicit step written in {delta} -form. The turbulent effects are simulated with the Baldwin - Lomax turbulence model. The application package FlowER is developed to calculate the 3D turbulent flows within complex-shape channels. The numerical results for the 3D flow around a cylinder and through the complex-shaped channels show the accuracy and the reliability of the suggested method. (author)
Computation of supersonic viscous flows over ogive-cylinders at angle of attack
Rakich, J. V.; Vigneron, Y. C.; Agarwal, R.
1979-01-01
The parabolic Navier-Stokes (PNS) marching finite-difference method is applied to 3-D viscous flow over pointed ogive-cylinders, and to turbulent flow over a cone. Ogive computations were performed using the new technique recently reported by Vigneron, Rakich, and Tannehill. Comparison is made with experiment and inviscid computations. The present results show that this method, which neglects part of the pressure gradient in the x-momentum equation, is nevertheless valid for flows with a strong favorable pressure gradient. In addition, turbulent separated flow over a cone has been computed using the older PNS code due to Lubard and Helliwell. It is found that one must freeze the turbulent eddy-viscosity model upstream of 3-D separation to get agreement with experiment.
Ellingson, William A.; Forster, George A.
1999-11-02
Apparatus and a method for controlling the flow rate of viscous materials through a nozzle includes an apertured main body and an apertured end cap coupled together and having an elongated, linear flow channel extending the length thereof. An end of the main body is disposed within the end cap and includes a plurality of elongated slots concentrically disposed about and aligned with the flow channel. A generally flat cam plate having a center aperture is disposed between the main body and end cap and is rotatable about the flow channel. A plurality of flow control vane assemblies are concentrically disposed about the flow channel and are coupled to the cam plate. Each vane assembly includes a vane element disposed adjacent the end of the flow channel. Rotation of the cam plate in a first direction causes a corresponding rotation of each of the vane elements for positioning the individual vane elements over the aperture in the end cap blocking flow through the flow channel, while rotation in an opposite direction removes the vane elements from the aperture and positions them about the flow channel in a nested configuration in the full open position, with a continuous range of vane element positions available between the full open and closed positions.
Equilibrium: three-dimensional configurations
International Nuclear Information System (INIS)
Anon.
1987-01-01
This chapter considers toroidal MHD configurations that are inherently three-dimensional. The motivation for investigation such complicated equilibria is that they possess the potential for providing toroidal confinement without the need of a net toroidal current. This leads to a number of advantages with respect to fusion power generation. First, the attractive feature of steady-state operation becomes more feasible since such configurations no longer require a toroidal current transformer. Second, with zero net current, one potentially dangerous class of MHD instabilities, the current-driven kink modes, is eliminated. Finally, three-dimensional configurations possess nondegenerate flux surfaces even in the absence of plasma pressure and plasma current. Although there is an enormous range of possible three-dimensional equilibria, the configurations of interest are accurately described as axisymmetric tori with superimposed helical fields; furthermore, they possess no net toroidal current. Instead, two different and less obvious restoring forces are developed: the helical sideband force and the toroidal dipole current force. Each is discussed in detail in Chapter 7. A detailed discussion of the parallel current constraint, including its physical significance, is given in section 7.2. A general analysis of helical sideband equilibria, along with a detailed description of the Elmo bumpy torus, is presented in sections 7.3 and 7.4. A general description of toroidal dipole-current equilibria, including a detailed discussion of stellarators, heliotrons, and torsatrons, is given in sections 7.5 and 7.6
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.
Numerical study of the viscous heat-conducting gas flow in a long shock tube
Kudryavtsev, Alexey; Khotyanovsky, Dmitry
2017-10-01
The results of numerical simulations of the propagation of the shock wave in a cylindrical shock tube of large length are presented. The results of the numerical computations agree well with the experimental data of Duff. The effects of viscous friction and heat conduction cause significant difference of the shock wave velocity from its inviscid theoretical value. The results of the computations at the considered flow parameters show that the shock wave and the contact surface, starting from a certain moment of time, propagate with equal speeds.
Two experiments to approach the Boltzmann factor: chemical reaction and viscous flow
International Nuclear Information System (INIS)
Fazio, Claudio; Battaglia, Onofrio R; Guastella, Ivan
2012-01-01
In this paper we discuss a pedagogical approach aimed at pointing out the role played by the Boltzmann factor in describing phenomena usually perceived as regulated by different mechanisms of functioning. Experimental results regarding some aspects of a chemical reaction and of the viscous flow of some liquids are analysed and described in terms of macroscopic variables whose temperature dependence is proportional to the Boltzmann factor. A description of a workshop implementing the approach in the framework of an undergraduate course for engineering education and some preliminary results about its pedagogical relevance are then reported. (paper)
Influences of viscous losses and end effects on liquid metal flow in electromagnetic pumps
International Nuclear Information System (INIS)
Kim, Hee Reyoung; Seo, Joon Ho; Hong, Sang Hee; Cho, Su won; Nam, Ho Yun; Cho, Man
1996-01-01
Analyses of the viscous and end effects on electromagnetic (EM) pumps of annular linear induction type for the sodium coolant circulation in Liquid Metal Fast Breeder Reactors have been carried out based on the MHD laminar flow analysis and the electromagnetic field theory. A one-dimensional MHD analysis for the liquid metal flowing through an annular channel has been performed on the basis of a simplified model of equivalent current sheets instead of three-phase currents in the discrete primary windings. The calculations show that the developed pressure difference resulted from electromagnetic and viscous forces in the liquid metal is expressed in terms of the slip, and that the viscous loss effects are negligible compared with electromagnetic driving forces except in the low-slip region where the pumps operate with very high flow velocities comparable with the synchronous velocity of the electromagnetic fields, which is not applicable to the practical EM pumps. A two-dimensional electromagnetic field analysis based on an equivalent current sheet model has found the vector potentials in closed form by means of the Fourier transform method. The resultant magnetic fields and driving forces exerted on the liquid metal reveal that the end effects due to finiteness of the pump length are formidable. In addition, a two-dimensional numerical analysis for vector potentials has been performed by the SOR iterative method on a realistic EM pump model with discretely-distributed currents in the primary windings. The numerical computations for the distributions of magnetic fields and developed pressure differences along the pump axial length also show considerable end effects at both inlet and outlet ends, especially at high flow velocities. Calculations of each magnetic force contribution indicate that the end effects are originated from the magnetic force caused by the induced current (υxB) generated by the liquid metal movement across the magnetic field rather than the one
Solving high Reynolds-number viscous flows by the general BEM and domain decomposition method
Wu, Yongyan; Liao, Shijun
2005-01-01
In this paper, the domain decomposition method (DDM) and the general boundary element method (GBEM) are applied to solve the laminar viscous flow in a driven square cavity, governed by the exact Navier-Stokes equations. The convergent numerical results at high Reynolds number Re = 7500 are obtained. We find that the DDM can considerably improve the efficiency of the GBEM, and that the combination of the domain decomposition techniques and the parallel computation can further greatly improve the efficiency of the GBEM. This verifies the great potential of the GBEM for strongly non-linear problems in science and engineering.
An implicit multigrid algorithm for computing hypersonic, chemically reacting viscous flows
International Nuclear Information System (INIS)
Edwards, J.R.
1996-01-01
An implicit algorithm for computing viscous flows in chemical nonequilibrium is presented. Emphasis is placed on the numerical efficiency of the time integration scheme, both in terms of periteration workload and overall convergence rate. In this context, several techniques are introduced, including a stable, O(m 2 ) approximate factorization of the chemical source Jacobian and implementations of V-cycle and filtered multigrid acceleration methods. A five species-seventeen reaction air model is used to calculate hypersonic viscous flow over a cylinder at conditions corresponding to flight at 5 km/s, 60 km altitude and at 11.36 km/s, 76.42 km altitude. Inviscid calculations using an eleven-species reaction mechanism including ionization are presented for a case involving 11.37 km/s flow at an altitude of 84.6 km. Comparisons among various options for the implicit treatment of the chemical source terms and among different multilevel approaches for convergence acceleration are presented for all simulations
Viscous potential flow analysis of magnetohydrodynamic interfacial stability through porous media
International Nuclear Information System (INIS)
Obied Allah, M.H.
2013-01-01
In the view of viscous potential flow theory, the hydromagnetic stability of the interface between two infinitely conducting, incompressible plasmas, streaming parallel to the interface and subjected to a constant magnetic field parallel to the streaming direction will be considered. The plasmas are flowing through porous media between two rigid planes and surface tension is taken into account. A general dispersion relation is obtained analytically and solved numerically. For Kelvin-Helmholtz instability problem, the stability criterion is given by a critical value of the relative velocity. On the other hand, a comparison between inviscid and viscous potential flow solutions has been made and it has noticed that viscosity plays a dual role, destabilizing for Rayleigh-Taylor problem and stabilizing for Kelvin-Helmholtz. For Rayleigh-Taylor instability, a new dispersion relation has been obtained in terms of a critical wave number. It has been found that magnetic field, surface tension, and rigid planes have stabilizing effects, whereas critical wave number and porous media have destabilizing effects. (author)
Tidal Modulation of Ice-shelf Flow: a Viscous Model of the Ross Ice Shelf
Brunt, Kelly M.; MacAyeal, Douglas R.
2014-01-01
Three stations near the calving front of the Ross Ice Shelf, Antarctica, recorded GPS data through a full spring-neap tidal cycle in November 2005. The data revealed a diurnal horizontal motion that varied both along and transverse to the long-term average velocity direction, similar to tidal signals observed in other ice shelves and ice streams. Based on its periodicity, it was hypothesized that the signal represents a flow response of the Ross Ice Shelf to the diurnal tides of the Ross Sea. To assess the influence of the tide on the ice-shelf motion, two hypotheses were developed. The first addressed the direct response of the ice shelf to tidal forcing, such as forces due to sea-surface slopes or forces due to sub-ice-shelf currents. The second involved the indirect response of ice-shelf flow to the tidal signals observed in the ice streams that source the ice shelf. A finite-element model, based on viscous creep flow, was developed to test these hypotheses, but succeeded only in falsifying both hypotheses, i.e. showing that direct tidal effects produce too small a response, and indirect tidal effects produce a response that is not smooth in time. This nullification suggests that a combination of viscous and elastic deformation is required to explain the observations.
Directory of Open Access Journals (Sweden)
Norfifah Bachok
Full Text Available The steady boundary layer flow of a viscous and incompressible fluid over a moving vertical flat plate in an external moving fluid with viscous dissipation is theoretically investigated. Using appropriate similarity variables, the governing system of partial differential equations is transformed into a system of ordinary (similarity differential equations, which is then solved numerically using a Maple software. Results for the skin friction or shear stress coefficient, local Nusselt number, velocity and temperature profiles are presented for different values of the governing parameters. It is found that the set of the similarity equations has unique solutions, dual solutions or no solutions, depending on the values of the mixed convection parameter, the velocity ratio parameter and the Eckert number. The Eckert number significantly affects the surface shear stress as well as the heat transfer rate at the surface.
Energy Technology Data Exchange (ETDEWEB)
Maher, A.R.; Al-Baghdadi, S. [International Technological Univ., London (United Kingdom). Dept. of Mechanical Engineering; Haroun, A.K.; Al-Janabi, S. [Babylon Univ., Babylon (Iraq). Dept. of Mechanical Engineering
2007-07-01
Fuel cell technology is expected to play an important role in meeting the growing demand for distributed generation because it can convert the chemical energy of a clean fuel directly into electrical energy. An operating fuel cell has varying local conditions of temperature, humidity, and power generation across the active area of the fuel cell in 3D. This paper presented a model that was developed to improve the basic understanding of the transport phenomena and thermal stresses in PEM fuel cells, and to investigate the behaviour of polymer membrane under hygro and thermal stresses during the cell operation. This comprehensive 3D, multiphase, non-isothermal model accounts for the major transport phenomena in a PEM fuel cell, notably convective and diffusive heat and mass transfer; electrode kinetics; transport and phase change mechanism of water; and potential fields. The model accounts for the liquid water flux inside the gas diffusion layers by viscous and capillary forces and can therefore predict the amount of liquid water inside the gas diffusion layers. This study also investigated the key parameters affecting fuel cell performance including geometry, materials and operating conditions. The model considers the many interacting, complex electrochemical, transport phenomena, thermal stresses and deformation that cannot be studied experimentally. It was concluded that the model can provide a computer-aided tool for the design and optimization of future fuel cells with much higher power density and lower cost. 21 refs., 2 tabs., 14 figs.
Hansen, A.J.
1993-01-01
The report documents modifications to the U.S. Geological Survey's modular three-dimensional finite-difference ground-water flow model used for a regional aquifer-system analysis of the Columbia Plateau. The report, which describes the concepts and mathematical basis for the modifications, is intended for potential users who are familiar with the original modular model. The modifications permit flow from a layer to any adjacent layer, allow the model to retain a cell of a layer that has been cut completely through by a canyon, and allow placing ground-water flow barriers on only specified branch conductances; a special version of the modified model uses a convergent grid. The report describes the data-input items that this modified model must read.
Three-dimensional analysis of the Pratt and Whitney alternate design SSME fuel turbine
Kirtley, K. R.; Beach, T. A.; Adamczyk, J. J.
1991-01-01
The three dimensional viscous time-mean flow in the Pratt and Whitney alternate design space shuttle main engine fuel turbine is simulated using the average passage Navier-Stokes equations. The migration of secondary flows generated by upstream blade rows and their effect on the performance of downstream blade rows is studied. The present simulation confirms that the flow in this two stage turbine is highly three dimensional and dominated by the tip leakage flow. The tip leakage vortex generated by the first blade persists through the second blade and adversely affects its performance. The greatest mixing of the inlet total temperature distortion occurs in the second vane and is due to the large leakage vortex generated by the upstream rotor. It is assumed that the predominant spanwise mixing mechanism in this low aspect ratio turbine is the radial transport due to the deterministically unsteady vortical flow generated by upstream blade rows. A by-product of the analysis is accurate pressure and heat loads for all blade rows under the influence of neighboring blade rows. These aero loads are useful for advanced structural analysis of the vanes and blades.
Three-dimensional turbopump flowfield analysis
Sharma, O. P.; Belford, K. A.; Ni, R. H.
1992-01-01
A program was conducted to develop a flow prediction method applicable to rocket turbopumps. The complex nature of a flowfield in turbopumps is described and examples of flowfields are discussed to illustrate that physics based models and analytical calculation procedures based on computational fluid dynamics (CFD) are needed to develop reliable design procedures for turbopumps. A CFD code developed at NASA ARC was used as the base code. The turbulence model and boundary conditions in the base code were modified, respectively, to: (1) compute transitional flows and account for extra rates of strain, e.g., rotation; and (2) compute surface heat transfer coefficients and allow computation through multistage turbomachines. Benchmark quality data from two and three-dimensional cascades were used to verify the code. The predictive capabilities of the present CFD code were demonstrated by computing the flow through a radial impeller and a multistage axial flow turbine. Results of the program indicate that the present code operated in a two-dimensional mode is a cost effective alternative to full three-dimensional calculations, and that it permits realistic predictions of unsteady loadings and losses for multistage machines.
Paniconi, C.; Troch, P.A.A.; Loon, van E.E.; Hilberts, A.G.J.
2003-01-01
The Boussinesq equation for subsurface flow in an idealized sloping aquifer of unit width has recently been extended to hillslopes of arbitrary geometry by incorporating the hillslope width function w(x) into the governing equation, where x is the flow distance along the length of the hillslope [
Energy Technology Data Exchange (ETDEWEB)
Costa, Gustavo Koury
2004-11-15
Although incompressible fluid flows can be regarded as a particular case of a general problem, numerical methods and the mathematical formulation aimed to solve compressible and incompressible flows have their own peculiarities, in such a way, that it is generally not possible to attain both regimes with a single approach. In this work, we start from a typically compressible formulation, slightly modified to make use of pressure variables and, through augmenting the stabilising parameters, we end up with a simplified model which is able to deal with a wide range of flow regimes, from supersonic to low speed gas flows. The resulting methodology is flexible enough to allow for the simulation of liquid flows as well. Examples using conservative and pressure variables are shown and the results are compared to those published in the literature, in order to validate the method. (author)
Brix, Lau; Ringgaard, Steffen; Rasmusson, Allan; Sørensen, Thomas Sangild; Kim, W Yong
2009-02-20
Two-dimensional, unidirectionally encoded, cardiovascular magnetic resonance (CMR) velocity mapping is an established technique for the quantification of blood flow in large vessels. However, it requires an operator to correctly align the planes of acquisition. If all three directional components of velocity are measured for each voxel of a 3D volume through the phases of the cardiac cycle, blood flow through any chosen plane can potentially be calculated retrospectively. The initial acquisition is then more time consuming but relatively operator independent. To compare the curves and volumes of flow derived from conventional 2D and comprehensive 3D flow acquisitions in a steady state flow model, and in vivo through planes transecting the ascending aorta and pulmonary trunk in 10 healthy volunteers. Using a 1.5 T Phillips Intera CMR system, 3D acquisitions used an anisotropic 3D segmented k-space phase contrast gradient echo sequence with a short EPI readout, with prospective ECG and diaphragm navigator gating. The 2D acquisitions used segmented k-space phase contrast with prospective ECG and diaphragm navigator gating. Quantitative flow analyses were performed retrospectively with dedicated software for both the in vivo and in vitro acquisitions. Analysis of in vitro data found the 3D technique to have overestimated the continuous flow rate by approximately 5% across the entire applied flow range. In vivo, the 2D and the 3D techniques yielded similar volumetric flow curves and measurements. Aortic flow: (mean +/- SD), 2D = 89.5 +/- 13.5 ml & 3D = 92.7 +/- 17.5 ml. Pulmonary flow: 2D = 98.8 +/- 18.4 ml & 3D = 94.9 +/- 19.0 ml). Each in vivo 3D acquisition took about 8 minutes or more. Flow measurements derived from the 3D and 2D acquisitions were comparable. Although time consuming, comprehensive 3D velocity acquisition could be relatively operator independent, and could potentially yield information on flow through several retrospectively chosen planes, for
Real three-dimensional biquadrics
Energy Technology Data Exchange (ETDEWEB)
Krasnov, Vyacheslav A [P.G. Demidov Yaroslavl State University, Yaroslavl (Russian Federation)
2010-09-07
We find the topological types of biquadrics (complete intersections of two real four-dimensional quadrics). The rigid isotopy classes of real three-dimensional biquadrics were described long ago: there are nine such classes. We find the correspondence between the topological types of real biquadrics and their rigid isotopy classes, and show that only two rigid isotopy classes have the same topological type. One of these classes consists of real GM-varieties and the other contains no GM-varieties. We also study the sets of real lines on real biquadrics.
Three-dimensional positioning with optofluidic microscope
DEFF Research Database (Denmark)
Vig, Asger Laurberg; Marie, Rodolphe; Jensen, Eric
2010-01-01
This paper reports on-chip based optical detection with three-dimensional spatial resolution by integration of an optofluidic microscope (OFM) in a microfluidic pinched flow fractionation (PFF) separation device. This setup also enables on-chip particle image velocimetry (PIV). The position...... a conventional fluorescence microscope as readout. The size separated microspheres are detected by OFM with an accuracy of ≤ 0.92 μm. The position in the height of the channel and the velocity of the separated microspheres are detected with an accuracy of 1.4 μm and 0.08 mm/s respectively. Throughout...
Bekezhanova, V. B.; Goncharova, O. N.
2017-09-01
The solution of special type of the Boussinesq approximation of the Navier - Stokes equations is used to simulate the two-layer evaporative fluid flows. This solution is the 3D generalization of the Ostroumov - Birikh solution of the equations of free convection. Modeling of the 3D fluid flows is performed in an infinite channel of the rectangular cross section without assumption of the axis-symmetrical character of the flows. Influence of gravity and evaporation on the dynamic and thermal phenomena in the system is studied. The fluid flow patterns are determined by various thermal, mechanical and structural effects. Numerical investigations are performed for the liquid - gas system like ethanol - nitrogen and HFE-7100 - nitrogen under conditions of normal and low gravity. The solution allows one to describe a formation of the thermocapillary rolls and multi-vortex structures in the system. Alteration of topology and character of the flows takes place with change of the intensity of the applied thermal load, thermophysical properties of working media and gravity action. Flows with translational, translational-rotational or partially reverse motion can be formed in the system.
On the viscous dissipation modeling of thermal fluid flow in a porous medium
Salama, Amgad
2011-02-24
The problem of viscous dissipation and thermal dispersion in saturated porous medium is numerically investigated for the case of non-Darcy flow regime. The fluid is induced to flow upward by natural convection as a result of a semi-infinite vertical wall that is immersed in the porous medium and is kept at constant higher temperature. The boundary layer approximations were used to simplify the set of the governing, nonlinear partial differential equations, which were then non-dimensionalized and solved using the finite elements method. The results for the details of the governing parameters are presented and investigated. It is found that the irreversible process of transforming the kinetic energy of the moving fluid to heat energy via the viscosity of the moving fluid (i.e.; viscous dissipation) resulted in insignificant generation of heat for the range of parameters considered in this study. On the other hand, thermal dispersion has shown to disperse heat energy normal to the wall more effectively compared with the normal diffusion mechanism. © 2011 Springer-Verlag.
Viscous surface flow induced on Ti-based bulk metallic glass by heavy ion irradiation
Energy Technology Data Exchange (ETDEWEB)
Zhang, Kun [Key Laboratory of Microgravity (National Microgravity Laboratory), Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190 (China); Hu, Zheng [Key Laboratory of Microgravity (National Microgravity Laboratory), Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190 (China); Science and Technology on Vehicle Transmission Laboratory, China North Vehicle Research Institute, Beijing 100072 (China); Li, Fengjiang [Key Laboratory of Microgravity (National Microgravity Laboratory), Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190 (China); Wei, Bingchen, E-mail: weibc@imech.ac.cn [Key Laboratory of Microgravity (National Microgravity Laboratory), Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190 (China)
2016-12-30
Highlights: • Obvious smoothing and roughening phases on the Ti-based MG surface resulted, which correspond respectively to the normal and off-normal incidence angles. • Atomic force microscopy confirms two types of periodic ripples distributed evenly over the rough surface. • The irradiation-induced viscosity of MG is about 4×10{sup 12} Pa·s, which accords with the theoretical prediction for metallic glasses close to glass transition temperature. • Surface-confined viscous flow plays a dominant quantitative role, which is due to radiation-induced softening of the low-viscosity surface layer. - Abstract: Ti-based bulk metallic glass was irradiated by a 20 MeV Cl{sup 4+} ion beam under liquid-nitrogen cooling, which produced remarkable surface smoothing and roughening that respectively correspond to normal and off-normal incidence angles of irradiation. Atomic force microscopy confirms two types of periodic ripples distributed evenly over the rough glass surface. In terms of mechanism, irradiation-induced viscosity agrees with the theoretical prediction for metallic glasses near glass transition temperature. Here, a model is introduced, based on relaxation of confined viscous flow with a thin liquid-like layer, that explains both surface smoothing and ripple formation. This study demonstrates that bulk metallic glass has high morphological instability and low viscosity under ion irradiation, which assets can pave new paths for metallic glass applications.
Yang, Jiecheng; Wu, Chuan-Yu; Adams, Michael
2014-02-01
Air flow and particle-particle/wall impacts are considered as two primary dispersion mechanisms for dry powder inhalers (DPIs). Hence, an understanding of these mechanisms is critical for the development of DPIs. In this study, a coupled DEM-CFD (discrete element method-computational fluid dynamics) is employed to investigate the influence of air flow on the dispersion performance of the carrier-based DPI formulations. A carrier-based agglomerate is initially formed and then dispersed in a uniformed air flow. It is found that air flow can drag API particles away from the carrier and those in the downstream air flow regions are prone to be dispersed. Furthermore, the influence of the air velocity and work of adhesion are also examined. It is shown that the dispersion number (i.e., the number of API particles detached from the carrier) increases with increasing air velocity, and decreases with increasing the work of adhesion, indicating that the DPI performance is controlled by the balance of the removal and adhesive forces. It is also shown that the cumulative Weibull distribution function can be used to describe the DPI performance, which is governed by the ratio of the fluid drag force to the pull-off force.
Directory of Open Access Journals (Sweden)
Jiecheng Yang
2014-02-01
Full Text Available Air flow and particle–particle/wall impacts are considered as two primary dispersion mechanisms for dry powder inhalers (DPIs. Hence, an understanding of these mechanisms is critical for the development of DPIs. In this study, a coupled DEM–CFD (discrete element method–computational fluid dynamics is employed to investigate the influence of air flow on the dispersion performance of the carrier-based DPI formulations. A carrier-based agglomerate is initially formed and then dispersed in a uniformed air flow. It is found that air flow can drag API particles away from the carrier and those in the downstream air flow regions are prone to be dispersed. Furthermore, the influence of the air velocity and work of adhesion are also examined. It is shown that the dispersion number (i.e., the number of API particles detached from the carrier increases with increasing air velocity, and decreases with increasing the work of adhesion, indicating that the DPI performance is controlled by the balance of the removal and adhesive forces. It is also shown that the cumulative Weibull distribution function can be used to describe the DPI performance, which is governed by the ratio of the fluid drag force to the pull-off force.
Yang, Jiecheng; Wu, Chuan-Yu; Adams, Michael
2014-01-01
Air flow and particle–particle/wall impacts are considered as two primary dispersion mechanisms for dry powder inhalers (DPIs). Hence, an understanding of these mechanisms is critical for the development of DPIs. In this study, a coupled DEM–CFD (discrete element method–computational fluid dynamics) is employed to investigate the influence of air flow on the dispersion performance of the carrier-based DPI formulations. A carrier-based agglomerate is initially formed and then dispersed in a uniformed air flow. It is found that air flow can drag API particles away from the carrier and those in the downstream air flow regions are prone to be dispersed. Furthermore, the influence of the air velocity and work of adhesion are also examined. It is shown that the dispersion number (i.e., the number of API particles detached from the carrier) increases with increasing air velocity, and decreases with increasing the work of adhesion, indicating that the DPI performance is controlled by the balance of the removal and adhesive forces. It is also shown that the cumulative Weibull distribution function can be used to describe the DPI performance, which is governed by the ratio of the fluid drag force to the pull-off force. PMID:26579364
Lubricant-impregnated surfaces for drag reduction in viscous laminar flow
Solomon, Brian; Khalil, Karim; Varanasi, Kripa; MIT Team
2013-11-01
For the first time, we explore the potential of lubricant impregnated surfaces (LIS) in reducing drag. LIS, inspired by the surface of the Nepenthes pitcher plant, have been introduced as a novel way of functionalizing a surface. LIS are characterized by extremely low contact angle hysteresis and have been show to effectively repel various liquids including water, oils, ketchup and blood. Motivated by the slippery nature of such surfaces, we explore the potential of LIS to reduce drag in internal flows. We observe a reduction in drag for LIS surfaces in a viscous laminar drag flow and model the impact of relevant system parameters (lubricant viscosity, working fluid viscosity, solid fraction, depth of texture, etc.).
Stability of Stationary Viscous Incompressible Flow Around a Rigid Body Performing a Translation
Deuring, Paul
2017-11-01
Suppose a rigid body moves steadily and without rotation in a viscous incompressible fluid, and the flow around the body is steady, too. Such a flow is usually described by the stationary Navier-Stokes system with Oseen term, in an exterior domain. An Oseen term arises because the velocity field is scaled in such a way that it vanishes at infinity. In the work at hand, such a velocity field, denoted by U, is considered as given. We study a solution of the incompressible evolutionary Navier-Stokes system with the same right-hand side and the same Dirichlet boundary conditions as the stationary problem, and with U+u_0 as initial data, where u_0 is a H^1 -function. Under the assumption that the H^1 -norm of u_0 is small (u_0 a "perturbation of U") and that the eigenvalues of a certain linear operator have negative real part, we show that \\Vert \
Simulation of Free Airfoil Vibrations in Incompressible Viscous Flow — Comparison of FEM and FVM
Directory of Open Access Journals (Sweden)
Petr Sváček
2012-01-01
Full Text Available This paper deals with a numerical solution of the interaction of two-dimensional (2-D incompressible viscous flow and a vibrating profile NACA 0012 with large amplitudes. The laminar flow is described by the Navier-Stokes equations in the arbitrary Lagrangian-Eulerian form. The profile with two degrees of freedom (2-DOF can rotate around its elastic axis and oscillate in the vertical direction. Its motion is described by a nonlinear system of two ordinary differential equations. Deformations of the computational domain due to the profile motion are treated by the arbitrary Lagrangian-Eulerianmethod. The finite volume method and the finite element method are applied, and the numerical results are compared.
Dong, Guanyu
2018-03-01
In order to analyze the microscopic stress field acting on residual oil droplets in micro pores, calculate its deformation, and explore the hydrodynamic mechanism of viscous-elastic fluids displacing oil droplets, the viscous-elastic fluid flow equations in micro pores are established by choosing the Upper Convected Maxwell constitutive equation; the numerical solutions of the flow field are obtained by volume control and Alternate Direction Implicit methods. From the above, the velocity field and microscopic stress field; the forces acting on residual oil droplets; the deformations of residual oil droplets by various viscous-elastic displacing fluids and at various Wiesenberg numbers are calculated and analyzed. The result demonstrated that both the normal stress and horizontal force acting on the residual oil droplets by viscous-elastic fluids are much larger compared to that of inelastic fluid; the distribution of normal stress changes abruptly; under the condition of the same pressure gradient in the system under investigation, the ratio of the horizontal forces acting on the residual oil droplets by different displacing fluids is about 1:8:20, which means that under the above conditions, the driving force on a oil droplet is 20 times higher for a viscous-elastic fluid compared to that of a Newtonian Fluid. The conclusions are supportive of the mechanism that viscous-elastic driving fluids can increase the Displacement Efficiency. This should be of help in designing new chemicals and selecting Enhanced Oil Recovery systems.
Hydrodynamics of Highly Viscous Flow past a Compound Particle: Analytical Solution
Directory of Open Access Journals (Sweden)
Longhua Zhao
2016-11-01
Full Text Available To investigate the translation of a compound particle in a highly viscous, incompressible fluid, we carry out an analytic study on flow past a fixed spherical compound particle. The spherical object is considered to have a rigid kernel covered with a fluid coating. The fluid within the coating has a different viscosity from that of the surrounding fluid and is immiscible with the surrounding fluid. The inertia effect is negligible for flows both inside the coating and outside the object. Thus, flows are in the Stokes regime. Taking advantage of the symmetry properties, we reduce the problem in two dimensions and derive the explicit formulae of the stream function in the polar coordinates. The no-slip boundary condition for the rigid kernel and the no interfacial mass transfer and force equilibrium conditions at fluid interfaces are considered. Two extreme cases: the uniform flow past a sphere and the uniform flow past a fluid drop, are reviewed. Then, for the fluid coating the spherical object, we derive the stream functions and investigate the flow field by the contour plots of stream functions. Contours of stream functions show circulation within the fluid coating. Additionally, we compare the drag and the terminal velocity of the object with a rigid sphere or a fluid droplet. Moreover, the extended results regarding the analytical solution for a compound particle with a rigid kernel and multiple layers of fluid coating are reported.
Three-Dimensional Navier-Stokes Calculations Using the Modified Space-Time CESE Method
Chang, Chau-lyan
2007-01-01
The space-time conservation element solution element (CESE) method is modified to address the robustness issues of high-aspect-ratio, viscous, near-wall meshes. In this new approach, the dependent variable gradients are evaluated using element edges and the corresponding neighboring solution elements while keeping the original flux integration procedure intact. As such, the excellent flux conservation property is retained and the new edge-based gradients evaluation significantly improves the robustness for high-aspect ratio meshes frequently encountered in three-dimensional, Navier-Stokes calculations. The order of accuracy of the proposed method is demonstrated for oblique acoustic wave propagation, shock-wave interaction, and hypersonic flows over a blunt body. The confirmed second-order convergence along with the enhanced robustness in handling hypersonic blunt body flow calculations makes the proposed approach a very competitive CFD framework for 3D Navier-Stokes simulations.
Energy Technology Data Exchange (ETDEWEB)
D' Agnese, F.A.; O' Brien, G.M.; Faunt, C.C.; Belcher, W.R.; San Juan, Carma
2002-11-22
In the early 1990's, two numerical models of the Death Valley regional ground-water flow system were developed by the U.S. Department of Energy. In general, the two models were based on the same basic hydrogeologic data set. In 1998, the U.S. Department of Energy requested that the U.S. Geological Survey develop and maintain a ground-water flow model of the Death Valley region in support of U.S. Department of Energy programs at the Nevada Test Site. The purpose of developing this ''second-generation'' regional model was to enhance the knowledge and understanding of the ground-water flow system as new information and tools are developed. The U.S. Geological Survey also was encouraged by the U.S. Department of Energy to cooperate to the fullest extent with other Federal, State, and local entities in the region to take advantage of the benefits of their knowledge and expertise. The short-term objective of the Death Valley regional ground-water flow system project was to develop a steady-stat e representation of the predevelopment conditions of the ground-water flow system utilizing the two geologic interpretations used to develop the previous numerical models. The long-term objective of this project was to construct and calibrate a transient model that simulates the ground-water conditions of the study area over the historical record that utilizes a newly interpreted hydrogeologic conceptual model. This report describes the result of the predevelopment steady-state model construction and calibration.
Hawkins, T. T.; Brand, B. D.; Sarrochi, D.; Pollock, N.
2016-12-01
One of the greatest challenges volcanologists face is the ability to extrapolate information about eruption dynamics and emplacement conditions from deposits. Pyroclastic density current (PDC) deposits are particularly challenging given the wide range of initial current conditions, (e.g., granular, fluidized, concentrated, dilute), and rapid flow transformations due to interaction with evolving topography. Analysis of particle shape-fabric can be used to determine flow direction, and may help to understand the rheological characteristics of the flows. However, extracting shape-fabric information from outcrop (2D) apparent fabric is limited, especially when outcrop exposure is incomplete or lacks context. To better understand and quantify the complex flow dynamics reflected in PDC deposits, we study the complete shape-fabric data in 3D using oriented samples. In the field, the prospective sample is carved from the unconsolidated deposit in blocks, the dimensions of which depend on the average clast size in the sample. The sample is saturated in situ with a water-based sodium silicate solution, then wrapped in plaster-soaked gauze to form a protective cast. The orientation of the sample is recorded on the block faces. The samples dry for five days and are then extracted in intact blocks. In the lab, the sample is vacuum impregnated with sodium silicate and cured in an oven. The fully lithified sample is first cut along the plan view to identify orientations of the long axes of the grains (flow direction), and then cut in the two plains perpendicular to grain elongation. 3D fabric analysis is performed using high resolution images of the cut-faces using computer assisted image analysis software devoted to shape-fabric analysis. Here we present the results of samples taken from the 18 May 1980 PDC deposit facies, including massive, diffuse-stratified and cross-stratified lapilli tuff. We show a relationship between the strength of iso-orientation of the elongated
Study of high viscous multiphase phase flow in a horizontal pipe
Baba, Yahaya D.; Aliyu, Aliyu M.; Archibong, Archibong-Eso; Almabrok, Almabrok A.; Igbafe, A. I.
2018-03-01
Heavy oil accounts for a major portion of the world's total oil reserves. Its production and transportation through pipelines is beset with great challenges due to its highly viscous nature. This paper studies the effects of high viscosity on heavy oil two-phase flow characteristics such as pressure gradient, liquid holdup, slug liquid holdup, slug frequency and slug liquid holdup using an advanced instrumentation (i.e. Electrical Capacitance Tomography). Experiments were conducted in a horizontal flow loop with a pipe internal diameter (ID) of 0.0762 m; larger than most reported in the open literature for heavy oil flow. Mineral oil of 1.0-5.0 Pa.s viscosity range and compressed air were used as the liquid and gas phases respectively. Pressure gradient (measured by means differential pressure transducers) and mean liquid holdup was observed to increase as viscosity of oil is increased. Obtained results also revealed that increase in liquid viscosity has significant effects on flow pattern and slug flow features.
Computational study of three-dimensional wake structure
International Nuclear Information System (INIS)
Himeno, R.; Shirayama, S.; Kamo, K.; Kuwahara, K.
1986-01-01
Three-dimensional wake structure is studied by numerically solving the incompressible Navier-Stokes equations. Results are visualized by a three-dimensional color graphic system. It was found that a pair of vortex tubes separated from a body plays the most important role in the wake. Near the body vortex tubes are rather stable, however, they gradually become unsteady as they flow down
Viscous Flow Behaviour of Karanja Oil Based Bio-lubricant Base Oil.
Sharma, Umesh Chandra; Sachan, Sadhana; Trivedi, Rakesh Kumar
2018-01-01
Karanja oil (KO) is widely used for synthesis of bio-fuel karanja oil methyl ester (KOME) due to its competitive price, good energy values and environmentally friendly combustion properties. Bio-lubricant is another value added product that can be synthesized from KO via chemical modification. In this work karanja oil trimethylolpropane ester (KOTMPE) bio-lubricant was synthesized and evaluated for its viscous flow behaviour. A comparison of viscous flow behaviours of natural KO and synthesized bio-fuel KOME and bio-lubricant KOTMPE was also made. The aim of this comparison was to validate the superiority of KOTMPE bio-lubricant over its precursors KO and KOME in terms of stable viscous flow at high temperature and high shear rate conditions usually encountered in engine operations and industrial processes. The free fatty acid (FFA) content of KO was 5.76%. KOME was synthesized from KO in a two-step, acid catalyzed esterification followed by base catalyzed transesterification, process at 65°C for 5 hours with oil-methanol ratio 1:6, catalysts H 2 SO 4 and KOH (1 and 1.25% w/w KO, respectively). In the final step, KOTMPE was prepared from KOME via transesterification with trimethylolpropane (TMP) at 150°C for 3 hours with KOME-TMP ratio 4:1 and H 2 SO 4 (2% w/w KOME) as catalyst. The viscosity versus temperature studies were made at 0-80°C temperatures in shear rate ranges of 10-1000 s -1 using a Discovery Hybrid Rheometer, model HR-3 (TA instruments, USA). The study found that viscosities of all three samples decreased with increase in temperature, though KOTMPE was able to maintain a good enough viscosity at elevated temperatures due to chemical modifications in its molecular structure. The viscosity index (VI) value for KOTMPE was 206.72. The study confirmed that the synthesized bio-lubricant KOTMPE can be used at high temperatures as a good lubricant, though some additives may be required to improve properties other than viscosity.
Ota, Miho; Sato, Noriko; Sone, Daichi; Ogura, Jun; Kunugi, Hiroshi
2017-01-01
Although aromatherapy is widely used, the pharmacology of the essential oils remains undiscovered. The present study assessed the effect of (-)-linalool, the main contained material of lavender, on the brain function. Healthy male volunteers calculated the regional cerebral blood flow (CBF) before and after inhalation of (-)-linalool, and CBF changes were evaluated. There were significant CBF reductions in the right superior temporal gyrus to insula, anterior cingulate cortex after inhalation. The previous study detected the regulatory influence of (-)-linalool on the glutamatergic transmission. The effect of (-)-linalool on the ACC and insula would cause the sedative and anxiolytic activity.
Chyczewski, Thomas Stanley, Jr.
A national interest in High Speed Civil Transports (HSCT) coupled with strict airport noise regulations has prompted the scientific community to investigate new and improved noise prediction strategies. Meeting these airport regulations is considered to be a major design challenge for the HSCT. In light of this effort, a direct simulation strategy for predicting supersonic jet noise is developed in this thesis. Direct simulations are quickly becoming the method of choice due to their generality and ever decreasing expense associated with the development of parallel processors. Supersonic jet noise is known to be dominated by the growth and decay of large scale turbulent structures. The direct simulation approach used here consists of solving the full Navier Stokes equations using high order finite difference techniques to simulate the evolution of these structures and the noise they radiate to the acoustic near field. This near field solution is then extrapolated to the far field using a Kirchhoff method. The numerical algorithm uses a fourth order Runge -Kutta method for the time integration. The spatial derivatives are approximated by a sixth order central scheme. A sixth order filter is used at each interior mesh point to damp frequencies that cannot be resolved by the spatial scheme. Second order filtering is provided only where required for stability. It is found to be confined to specific locations in the jet core and should have no effect on the acoustic solution. Characteristic based nonreflecting conditions are used to minimize reflections at the far field boundaries and have proven to be effective. Additional boundary conditions are required in the form of it model for the nozzle exit flow. The characteristics of the nozzle exit flow can have a significant impact on the noise radiation. This dependence is unfortunate since comprehensive experimental data is not available in this region of the jet. A model is developed here that addresses a variety of
DEFF Research Database (Denmark)
Hansen, Kim Granly; Solberg, Tron; Hjertager, Bjørn Helge
2004-01-01
concentration in the 10.85 m high riser by the use of a UV detector system. Furthermore a pressure drop profile was reported. Comparison between measured and simulated time averaged ozone concentration at different elevations in the riser shows good agreement. The 3D representation of the reactor geometry gives......The isothermal decomposition of ozone has been implemented in the CFD code FLOTRACS-MP-3D. The code is a 3D multiphase computational fluid dynamics code with an Eulerian description of both gas and particle phase. The turbulent motion of the particulate phase is modeled using the kinetic theory...... for granular flow, and the gas phase turbulence is modeled using a Sub-Grid-Scale model, cf. Ibsen et al. (2001). The decomposition reaction is studied in a 3D representation of a 0.254 m i.d. riser, which has been studied experimentally by Ouyang et al. (1993). The authors obtained profiles of ozone...
THE THREE DIMENSIONAL THERMAL HYDRAULIC CODE BAGIRA.
Energy Technology Data Exchange (ETDEWEB)
KALINICHENKO,S.D.; KOHUT,P.; KROSHILIN,A.E.; KROSHILIN,V.E.; SMIRNOV,A.V.
2003-05-04
BAGIRA - a thermal-hydraulic program complex was primarily developed for using it in nuclear power plant simulator models, but is also used as a best-estimate analytical tool for modeling two-phase mixture flows. The code models allow consideration of phase transients and the treatment of the hydrodynamic behavior of boiling and pressurized water reactor circuits. It provides the capability to explicitly model three-dimensional flow regimes in various regions of the primary and secondary circuits such as, the mixing regions, circular downcomer, pressurizer, reactor core, main primary loops, the steam generators, the separator-reheaters. In addition, it is coupled to a severe-accident module allowing the analysis of core degradation and fuel damage behavior. Section II will present the theoretical basis for development and selected results are presented in Section III. The primary use for the code complex is to realistically model reactor core behavior in power plant simulators providing enhanced training tools for plant operators.
Energy Technology Data Exchange (ETDEWEB)
Otsuyama, S. [West Japan Railway Company, Osaka (Japan); Yang, X. [Kanazawa University, Ishikawa (Japan); Okajima, A. [Kanazawa University, Ishikawa (Japan). Faculty of Engineering
1999-11-25
Three dimensional computations were performed using the KIVA-3 code to investigate the unsteady compressible turbulent flows about a practical train passing through a single-track tunnel. Both length of the train/tunnel and speed of the train were considered to investigate their effects on the train-tunnel interaction. In order to understand the whole process of the train-tunnel aerodynamic interaction, we studied the formation and propagation of the pressure waves, the reflection and radiation of the waves at the tunnel portals and the histories of aerodynamic forces on the train. The experimental results were compared well with the computational data. The code can be used to predict the aerodynamic phenomena of the train-tunnel system. (author)
A Parallel Multigrid Solver for Viscous Flows on Anisotropic Structured Grids
Prieto, Manuel; Montero, Ruben S.; Llorente, Ignacio M.; Bushnell, Dennis M. (Technical Monitor)
2001-01-01
This paper presents an efficient parallel multigrid solver for speeding up the computation of a 3-D model that treats the flow of a viscous fluid over a flat plate. The main interest of this simulation lies in exhibiting some basic difficulties that prevent optimal multigrid efficiencies from being achieved. As the computing platform, we have used Coral, a Beowulf-class system based on Intel Pentium processors and equipped with GigaNet cLAN and switched Fast Ethernet networks. Our study not only examines the scalability of the solver but also includes a performance evaluation of Coral where the investigated solver has been used to compare several of its design choices, namely, the interconnection network (GigaNet versus switched Fast-Ethernet) and the node configuration (dual nodes versus single nodes). As a reference, the performance results have been compared with those obtained with the NAS-MG benchmark.
Modified rational Legendre approach to laminar viscous flow over a semi-infinite flat plate
International Nuclear Information System (INIS)
Tajvidi, T.; Razzaghi, M.; Dehghan, M.
2008-01-01
A numerical method for solving the classical Blasius' equation is proposed. The Blasius' equation is a third order nonlinear ordinary differential equation , which arises in the problem of the two-dimensional laminar viscous flow over a semi-infinite flat plane. The approach is based on a modified rational Legendre tau method. The operational matrices for the derivative and product of the modified rational Legendre functions are presented. These matrices together with the tau method are utilized to reduce the solution of Blasius' equation to the solution of a system of algebraic equations. A numerical evaluation is included to demonstrate the validity and applicability of the method and a comparison is made with existing results
Numerical Investigation of Viscous Flow Velocity Field around a Marine Cavitating Propeller
Directory of Open Access Journals (Sweden)
Zhifeng Zhu
2014-11-01
Full Text Available Velocity field around a ship cavitating propeller is investigated based on the viscous multiphase flow theory. Using a hybrid grid, the unsteady Navier-stokes (N-S and the bubble dynamics equations are solved in this paper to predict the velocity in a propeller wake and the vapor volume fraction on the back side of propeller blade for a uniform inflow. Compared with experimental results, the numerical predictions of cavitation and axial velocity coincide with the measured data. The evolution of tip vortex is shown, and the interaction between the tip vortex of the current blade and the wake of the next one occurs in the far propeller wake. The frequency of velocity signals changes from shaft rate to blade rate. The phenomena reflect the instability of propeller wake.
Self-organization of two-dimensional incompressible viscous flow in a friction-free box
Energy Technology Data Exchange (ETDEWEB)
Kondoh, Y.; Yoshizawa, M.; Nakano, A. [Gunma Univ., Kiryu (Japan). Faculty of Engineering; Yabe, T.
1995-10-01
The process by which self-organization occurs for two-dimensional incompressible viscous flow in a friction-free box is investigated theoretically with the use of numerical simulations. It is shown by an eigenfunction spectrum analysis that two basic processes for the self-organization are the spectrum transfer by nonlinear couplings and the selective dissipation among the eigenmodes of the dissipative operator, and they yield spectrum accumulation at the lowest eigenmode. It is also clarified that an important process during nonlinear self-organization is an interchange between the dominant operators, which leads to a final self-similar coherent structure, determined uniquely by the lowest eigenmode of the dissipative operator. (author).
Improved flux calculations for viscous incompressible flow by the variable penalty method
International Nuclear Information System (INIS)
Kheshgi, H.; Luskin, M.
1985-01-01
The Navier-Stokes system for viscous, incompressible flow is considered, taking into account a replacement of the continuity equation by the perturbed continuity equation. The introduction of the approximation allows the pressure variable to be eliminated to obtain the system of equations for the approximate velocity. The penalty approximation is often applied to numerical discretizations since it provides a reduction in the size and band-width of the system of equations. Attention is given to error estimates, and to two numerical experiments which illustrate the error estimates considered. It is found that the variable penalty method provides an accurate solution for a much wider range of epsilon than the classical penalty method. 8 references
Directory of Open Access Journals (Sweden)
Habibi Matin Meisam
2014-01-01
Full Text Available Forced convection boundary layer magneto-hydrodynamic (MHD flow of a nanofluid over a permeable stretching plate is studied in this paper. The effects of suction-injection and viscous dissi1pation are taken into account. The nanofluid model includes Brownian motion and thermophoresis effects. The governing momentum, energy and nanofluid solid volume fraction equations are solved numerically using an implicit finite difference scheme known as Keller-box method and the results are compared with available numerical data. The results for the dimensionless velocity, dimensionless temperature, dimensionless nanofluid solid volume fraction, reduced Nusselt and reduced Sherwood numbers are presented illustrating the effects of magnetic parameter, suction-injection parameter, Brownian motion parameter, thermophoresis parameter, Prandtl number, Eckert number and Lewis number.
Toroidal Lagrangian Flow Structues in highly viscous fluids by moving bent rods
Chtcheprov, Pavel; Camassa, Roberto; Holz, David; Marron, David; Martindale, James; McLaughlin, Richard; Vicci, Leandra; Zhao, Longhua
2010-11-01
Motile cilia play a large role in fluid motion across the surface of ciliates. Flows caused by the cilia move debris and mucus through mass beat patterns controlled by the motor proteins while rotating about the basal body that attaches the cilium to the cell surface. This study approximates the cilium as a slender body rotating about a point of contact of one of its ends in a viscous fluid. The bent rod sweeps out a virtual cone with a chord connecting both ends. The bend of the rod, the cone angle, the angle between the central axis to the normal plane, and the angle of rotation of the bent rod about its chord affect the flow patterns in a Stokes fluid. The slender body theory allows for an asymptotic solution of the Lagrangian trajectories and flow patterns caused by the precessing rod, which can be directly compared to experimental data. Altering the above parameters produces different toroidal flow structures. Using 3D stereo calibration, accurate quantified comparisons of epicyclic particle trajectories in short and long time are made against the model predictions.
Agarwal, R.; Rakich, J. V.
1978-01-01
Computational results obtained with a parabolic Navier-Stokes marching code are presented for supersonic viscous flow past a pointed cone at angle of attack undergoing a combined spinning and coning motion. The code takes into account the asymmetries in the flow field resulting from the motion and computes the asymmetric shock shape, crossflow and streamwise shear, heat transfer, crossflow separation and vortex structure. The side force and moment are also computed. Reasonably good agreement is obtained with the side force measurements of Schiff and Tobak. Comparison is also made with the only available numerical inviscid analysis. It is found that the asymmetric pressure loads due to coning motion are much larger than all other viscous forces due to spin and coning, making viscous forces negligible in the combined motion.
MATHEMATICAL MODEL NON-ISOTHERMAL FLOW HIGHLY VISCOUS MEDIA CHANNELS MATRIX EXTRUDER
Directory of Open Access Journals (Sweden)
A. S. Sidorenko
2015-01-01
Full Text Available We consider a one-dimensional steady flow of highly viscous medium in a cylindrical channel with Dissipation and dependence of the viscosity on the temperature. It is assumed that a relatively small intervals of temperature variation of the dynamic viscosity with a sufficient degree of accuracy can be assumed to be linear. The model was based on the equations of hydrodynamics and the heat transfer fluid. In the task channel wall temperature is assumed constant. An approximate solution of the problem, according to which the distribution of velocity, pressure and temperature is sought in the form of an expansion in powers of the dimensionless transverse coordinates. A special case, when the ratio of the velocity distribution, pressure and temperature is allowed to restrict the number of terms in the expansion as follows: for speed - the first 3 to the pressure - the first two for the temperature - the first 5. The expressions to determine the temperature profile of the medium in the channel and characterization dissipative heating. To simulate the process of heat transfer highly viscous media developed a program for personal electronic computers. The calculation was performed using experimental research data melt flow grain mixture of buckwheat and soybeans for the load speed of 0.08 mm / s. The method of computer simulation carried out checks on the adequacy of the solutions to the real process of heat transfer. Analysis of the results indicates that for small values of the length of the channel influence dissipation function appears mainly at the wall. By increasing the reduced length of this phenomenon applies to all section of the channel. At high temperature profile along the channel length is determined entirely by dissipation. In the case of heat transfer due to frictional heat only, the form of curves of temperature distribution is a consequence of the interaction effects of heating due to viscous shear effects cooling by conduction. The
Directory of Open Access Journals (Sweden)
Yuliang Zhao
2018-03-01
Full Text Available Our group has reported that Melan-A cells and lymphocytes undergo self-rotation in a homogeneous AC electric field, and found that the rotation velocity of these cells is a key indicator to characterize their physical properties. However, the determination of the rotation properties of a cell by human eyes is both gruesome and time consuming, and not always accurate. In this paper, a method is presented to more accurately determine the 3D cell rotation velocity and axis from a 2D image sequence captured by a single camera. Using the optical flow method, we obtained the 2D motion field data from the image sequence and back-project it onto a 3D sphere model, and then the rotation axis and velocity of the cell were calculated. After testing the algorithm on animated image sequences, experiments were also performed on image sequences of real rotating cells. All of these results indicate that this method is accurate, practical, and useful. Furthermore, the method presented there can also be used to determine the 3D rotation velocity of other types of spherical objects that are commonly used in microfluidic applications, such as beads and microparticles.
Gresse, Marceau; Vandemeulebrouck, Jean; Byrdina, Svetlana; Chiodini, Giovanni; Revil, André; Johnson, Timothy C.; Ricci, Tullio; Vilardo, Giuseppe; Mangiacapra, Annarita; Lebourg, Thomas; Grangeon, Jacques; Bascou, Pascale; Metral, Laurent
2017-11-01
The Solfatara volcano is the main degassing area of the Campi Flegrei caldera, characterized by 60 years of unrest. Assessing such renewal activity is a challenging task because hydrothermal interactions with magmatic gases remain poorly understood. In this study, we decipher the complex structure of the shallow Solfatara hydrothermal system by performing the first 3-D, high-resolution, electrical resistivity tomography of the volcano. The 3-D resistivity model was obtained from the inversion of 43,432 resistance measurements performed on an area of 0.68 km2. The proposed interpretation of the multiphase hydrothermal structures is based on the resistivity model, a high-resolution infrared surface temperature image, and 1,136 soil CO2 flux measurements. In addition, we realized 27 soil cation exchange capacity and pH measurements demonstrating a negligible contribution of surface conductivity to the shallow bulk electrical conductivity. Hence, we show that the resistivity changes are mainly controlled by fluid content and temperature. The high-resolution tomograms identify for the first time the structure of the gas-dominated reservoir at 60 m depth that feeds the Bocca Grande fumarole through a 10 m thick channel. In addition, the resistivity model reveals a channel-like conductive structure where the liquid produced by steam condensation around the main fumaroles flows down to the Fangaia area within a buried fault. The model delineates the emplacement of the main geological structures: Mount Olibano, Solfatara cryptodome, and tephra deposits. It also reveals the anatomy of the hydrothermal system, especially two liquid-dominated plumes, the Fangaia mud pool and the Pisciarelli fumarole, respectively.
Three dimensional magnetic abacus memory.
Zhang, ShiLei; Zhang, JingYan; Baker, Alexander A; Wang, ShouGuo; Yu, GuangHua; Hesjedal, Thorsten
2014-08-22
Stacking nonvolatile memory cells into a three-dimensional matrix represents a powerful solution for the future of magnetic memory. However, it is technologically challenging to access the data in the storage medium if large numbers of bits are stacked on top of each other. Here we introduce a new type of multilevel, nonvolatile magnetic memory concept, the magnetic abacus. Instead of storing information in individual magnetic layers, thereby having to read out each magnetic layer separately, the magnetic abacus adopts a new encoding scheme. It is inspired by the idea of second quantisation, dealing with the memory state of the entire stack simultaneously. Direct read operations are implemented by measuring the artificially engineered 'quantised' Hall voltage, each representing a count of the spin-up and spin-down layers in the stack. This new memory system further allows for both flexible scaling of the system and fast communication among cells. The magnetic abacus provides a promising approach for future nonvolatile 3D magnetic random access memory.
Three-Dimensional Laser Microvision
Shimotahira, Hiroshi; Iizuka, Keigo; Chu, Sun-Chun; Wah, Christopher; Costen, Furnie; Yoshikuni, Yuzo
2001-04-01
A three-dimensional (3-D) optical imaging system offering high resolution in all three dimensions, requiring minimum manipulation and capable of real-time operation, is presented. The system derives its capabilities from use of the superstructure grating laser source in the implementation of a laser step frequency radar for depth information acquisition. A synthetic aperture radar technique was also used to further enhance its lateral resolution as well as extend the depth of focus. High-speed operation was made possible by a dual computer system consisting of a host and a remote microcomputer supported by a dual-channel Small Computer System Interface parallel data transfer system. The system is capable of operating near real time. The 3-D display of a tunneling diode, a microwave integrated circuit, and a see-through image taken by the system operating near real time are included. The depth resolution is 40 m; lateral resolution with a synthetic aperture approach is a fraction of a micrometer and that without it is approximately 10 m.
Three dimensional imaging of otoliths
International Nuclear Information System (INIS)
Barry, B.; Markwitz, A.; David, B.
2008-01-01
Otoliths are small structures in fish ears made of calcium carbonate which carry a record of the environment in which the fish live. Traditionally, in order to study their microchemistry by a scanning technique such as PIXE the otoliths have been either ground down by hand or thin sectioned to expose the otolith core. However this technique is subject to human error in judging the core position. In this study we have scanned successive layers of otoliths 50 and 100 μm apart by removing the otolith material in a lapping machine which can be set to a few μm precision. In one study by comparing data from otoliths from the two ears of a freshwater species we found that polishing by hand could miss the core and thus give misleading results as to the life cycle of the fish. In another example we showed detail in a marine species which could be used to build a three dimensional picture of the Sr distribution. (author)
Three dimensional magnetic abacus memory
Zhang, Shilei; Zhang, Jingyan; Baker, Alexander; Wang, Shouguo; Yu, Guanghua; Hesjedal, Thorsten
2015-03-01
Stacking nonvolatile memory cells into a three-dimensional matrix represents a powerful solution for the future of magnetic memory. However, it is technologically challenging to access the individual data in the storage medium if large numbers of bits are stacked on top of each other. Here we introduce a new type of multilevel, nonvolatile magnetic memory concept, the magnetic abacus. Instead of storing information in individual magnetic layers, thereby having to read out each magnetic layer separately, the magnetic abacus adopts a new encoding scheme which envisages a classical abacus with the beads operated by electron spins. It is inspired by the idea of second quantization, dealing with the memory state of the entire stack simultaneously. Direct read operations are implemented by measuring the artificially engineered `quantized' Hall voltage, representing a count of the spin-up and spin-down layers in the stack. This concept of `second quantization of memory' realizes the 3D memory architecture with superior reading and operation efficiency, thus is a promising approach for future nonvolatile magnetic random access memory.
Buckling of thin viscous sheets with inhomogenous viscosity under extensional flows
Srinivasan, Siddarth; Wei, Zhiyan; Mahadevan, L.
2016-11-01
We investigate the dynamics, shape and stability of a thin viscous sheet subjected to an extensional flow under an imposed non-uniform temperature field. Using finite element simulations, we first solve for the stretching flow to determine the pre-buckling sheet thickness and in-plane flow velocities. Next, we use this solution as the base state and solve the linearized partial differential equation governing the out-of-plane deformation of the mid-surface as a function of two dimensionless operating parameters: the normalized stretching ratio α and a dimensionless width of the heating zone β. We show the sheet can become unstable via a buckling instability driven by the development of localized compressive stresses, and determine the global shape and growth rates of the most unstable mode. The growth rate is shown to exhibit a transition from stationary to oscillatory modes in region upstream of the heating zone. Finally, we investigate the effect of surface tension and present an operating diagram that indicates regions of the parameter space that minimizes or entirely suppresses the instability while achieving desired outlet sheet thickness. Therefore, our work is directly relevant to various industrial processes including the glass redraw & float-glass method.
Viscous flow in and around a cavity surrounded by a concentric permeable patch
Palaniappan, D.
2017-11-01
Steady viscous incompressible fluid flow in and around a spherical fluid cavity of radius a surrounded by a permeable patch with thickness b - a is investigated in the limit of low-Reynolds number. Our model uses the Stokes equations in the pure fluid regions and the Darcy law in the concentric permeable patch. Analytic solutions for the velocity and pressure fields are derived in singularity form involving the key parameters such as the Darcy permeability coefficient k and the thickness of the permeable layer. The Faxen law for the hydrodynamical drag acting on the concentric spherical geometry due to an arbitrary incident flow is extracted from our singularity solutions. It is found that the thickness of the permeable layer and the permeability play a crucial role in controlling the drag. An expression for the mass of the fluid that enters the outer sphere is calculated by integrating the exterior radial velocity field. The hydrodynamic force on the concentric spherical shell due to the flow induced by a Stokeslet is also derived from our general expressions. Several special cases of interest are deduced from our exact analysis. The results are of some interest in the prediction of forces exerted on the walls in certain biological models with permeable layers. I request you to place my presentation on the 19th (Sunday) as I have to give final exams on Monday. Thank you.