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Sample records for 3d stokes flow

  1. 3D Topology optimization of Stokes flow problems

    Gersborg-Hansen, Allan; Dammann, Bernd

    energy efficient devices for 2D Stokes flow. Creeping flow problems are described by the Stokes equations which model very viscous fluids at macro scales or ordinary fluids at very small scales. The latter gives the motivation for topology optimization problems based on the Stokes equations being a model......The present talk is concerned with the application of topology optimization to creeping flow problems in 3D. This research is driven by the fact that topology optimization has proven very successful as a tool in academic and industrial design problems. Success stories are reported from such diverse...

  2. Topology optimization of 3D Stokes flow problems

    Gersborg-Hansen, Allan

    test problems only. The motivation for considering topology optimization in 3D Stokes flow originates from micro fluidic systems. At small scales the Stokes equations are a reasonable mathematical model to use for the fluid behavior. Physically Stokes flow is an exotic inertia free flow, which in...... setting of standard analysis software which enables a credible performance check relevant before design manufacturing. Note that this requires a proper interpretation of a computed design used to generate a body fitted mesh. In addition issues related to the parallel solution of the linear algebra...

  3. SALE-3D, 3-D Fluid Flow, Navier Stokes Equation Using Lagrangian or Eulerian Method

    1 - Description of problem or function: SALE-3D calculates three- dimensional fluid flows at all speeds, from the incompressible limit to highly supersonic. An implicit treatment of the pressure calculation similar to that in the Implicit Continuous-fluid Eulerian (ICE) technique provides this flow speed flexibility. In addition, the computing mesh may move with the fluid in a typical Lagrangian fashion, be held fixed in an Eulerian manner, or move in some arbitrarily specified way to provide a continuous rezoning capability. This latitude results from use of an Arbitrary Lagrangian-Eulerian (ALE) treatment of the mesh. The partial differential equations solved are the Navier-Stokes equations and the mass and internal energy equations. The fluid pressure is determined from an equation of state and supplemented with an artificial viscous pressure for the computation of shock waves. The computing mesh consists of a three-dimensional network of arbitrarily shaped, six-sided deformable cells, and a variety of user-selectable boundary conditions are provided in the program. 2 - Method of solution: SALE3D uses an ICED-ALE technique, which combines the ICE method of treating flow speeds and the ALE mesh treatment to calculate three-dimensional fluid flow. The finite- difference approximations to the conservation of mass, momentum, and specific internal energy differential equations are solved in a sequence of time steps on a network of deformable computational cells. The basic hydrodynamic part of each cycle is divided into three phases: (1) an explicit solution of the Lagrangian equations of motion updating the velocity field by the effects of all forces, (2) an implicit calculation using Newton-Raphson iterative scheme that provides time-advanced pressures and velocities, and (3) the addition of advective contributions for runs that are Eulerian or contain some relative motion of grid and fluid. A powerful feature of this three-phases approach is the ease with which

  4. Topology optimization of 3D Stokes flow problems

    Gersborg-Hansen, Allan; Sigmund, Ole; Bendsøe, Martin P.

    The design of MEMS devices have benefitted from the topology optimization tool and complicated layout problems have been solved, see [1] for an overview. This research is aimed at micro fluidic devices known as micro-Total-Analysis-Systems (muTAS) where the main physical phenomena originate from...... examples relevant for optimal micro fluidic mixer design are shown where the design is planar - compliant with micro fabrication techniques - and where the designs are 3D. In addition issues related to the parallel solution of the linear algebra problems are discussed. The implementation uses the...

  5. 3-D thin layer navier-stokes solution of supersonic turbulent flow

    In this research, a 3-D Thin Layer Navier-Stokes (TLNS) code is developed. This code consists of several numerical algorithms for space and time discretization, together with appropriate turbulence modeling. The Roe method is used for the discretization of inviscid terms and the central scheme for viscous terms. The explicit time marching technique is applied, based on finite volume space discretization. This code can be employed in the range of laminar and turbulent flow. It is validated for a supersonic flow with mach number 3 around a tangent-o give with incidence angles of 6 deg and a secant-o give with incidence angles of 10 deg. The circumferential pressure distribution is compared with experimental and Euler code results and the results of TLNS are acceptable. The cross-sectional Mach number contours are also presented. In addition to an outer shock, a cross-flow shock wave is captured in the case of a 10 deg angle of incidence

  6. Computation of 3D steady Navier-Stokes flow with free-surface gravity waves

    Lewis, M. R.; Koren, Barry; Raven, H.C.

    2003-01-01

    In this paper an iterative method for the computation of stationary gravity-wave solutions is investigated, using a novel formulation of the free-surface (FS) boundary-value problem. This method requires the solution of a sequence of stationary Reynolds-Averaged Navier-Stokes subproblems employing the so-called quasi free-surface condition. The numerical performance of this new approach is investigated for two test cases. The first test case involves the computation of the 3D gravity-wave pat...

  7. Numerical solution of 3D Stokes problems

    Preconditions conjugate gradient algorithms for solving 3D Stokes problems by stable piecewise discontinuous pressure finite elements are presented. The emphasis is on the preconditioning schemes and their numerical implementation for use with Hermitian-based discontinuous pressure elements. For the piecewise constant discontinuous pressure elements, a variant implementation of the preconditioner proposed by Cahouet and Chabard for the continuous pressure elements is employed. For the piecewise linear discontinuous pressure elements, a new preconditioner is presented. Numerical examples are presented for the cubic lid driven cavity problem with two representative elements (i.e., the Q2-P0 and the Q2-P1 brick elements). Numerical results show that the preconditioning schemes are very effective in reducing the number of pressure iterations at very reasonable costs. It is also shown that they are insensitive to the mesh Reynolds number, except for nearly steady flows (Rem → 0), and are almost independent of mesh sizes. It is demonstrated that the schemes performed reasonably well on nonuniform meshes. 15 refs., 6 figs., 1 tab

  8. Persistence of Steady 3D Euler Solutions for 3D Navier-Stokes Equations

    Li, Y Charles

    2008-01-01

    In the classical plane Couette flow, certain 3D steady solution (the so-called lower branch state) of the Navier-Stokes equations has a nontrivial limit as the Reynolds number approaches infinity \\cite{WGW07}. The limit is a shear of the form ($U(y,z), 0, 0$) in velocity variables. On the other hand, all the shears of this form are solutions of the corresponding 3D Euler equations. This note derives a necessary condition for such a shear to be a limit shear. The condition is $\\int \\Dl U f(U) dy dz = 0$ for any function $f$ satisfying certain boundary condition. Similar conditions are also derived for plane Poiseuille flow and pipe Poiseuille flow, which correspond to similar limit shears as revealed in \\cite{Wal03} \\cite{Vis08}.

  9. A Tamed 3D Navier-Stokes Equation in Domains

    Zhang, Xicheng

    2008-01-01

    In this paper, we analyze a tamed 3D Navier-Stokes equation in uniform $C^2$-domains (not necessarily bounded), which obeys the scaling invariance principle, and prove the existence and uniqueness of strong solutions to this tamed equation. In particular, if there exists a bounded solution to the classical 3D Navier-Stokes equation, then this solution satisfies our tamed equation. Moreover, the existence of a global attractor for the tamed equation in bounded domains is also proved. As simple...

  10. Quasi-3D navier-stokes model for rotating airfoil

    Wen Zhong Shen; Noerkaer Soerensen, J.

    1999-02-01

    A quasi-3D model of the unsteady Navier-Stokes equations in a rotating frame of reference has been developed. The equations governing the flow past a rotating blade are approximated using an order of magnitude analysis on the spanwise derivatives. The model takes into account rotational effects and spanwise outflow at computing expenses in the order of what is typical for similar 2D calculations. Results are presented for both laminar and turbulent flows past blades in pure rotation. In the turbulent case the influence of small-scale turbulence is modelled by the one-equation Baldwin-Barth turbulence model. The computations demonstrate that the main influence of rotation is to increase the maximum lift. (au) 18 refs.

  11. On the Regularity for 3D Navier-Stokes Equation

    Lin, Qun

    2013-01-01

    In this paper we will prove that the vorticity belongs to $L^{\\infty}(0,T;L^2(\\Omega))$ for 3D incompressible Navier-Stokes equation with periodic initial-boundary value conditions, then the existence of a global smooth solution is obtained. Our approach is to construct a set of auxiliary problems to approximate the original one for vorticity equation.

  12. Investigations of Interaction of the Main Flow with Root and Tip Leakage Flows in an Axial Turbine Stage by Means of a Source/Sink Approach for a 3D Navier-Stokes Solver

    Piotr Lampart; Andrzej Gardzilewicz; Sergey Yershov; Andrey Rusanov

    2001-01-01

    The effect of interaction of the main flow with root and tip leakage flows on the performance of an high pressure (HP) stage of an impulse turbine is studied numerically. The flow in blade-to-blade channels and axial gaps is computed with the aid of a 3D Navier-Stokes solver FlowER. The numerical scheme is modified to include the some/sink-type boundary conditions in places at the endwalls referring to design locations of injection of leakage and windage flows into, or extract from, the blade-to-blade passage. The turbine stage is computed in three configurations. First, computations are made without tip leakage and windage flows with source/sink slots closed.Second, tip leakage slots are open. Third, both tip leakage and windage flow slots are open, and the obtained flow characteristics including kinetic energy losses in the stage are compared so as to estimate the interaction of the main and leakage flows.

  13. On the Dynamic Programming Approach for the 3D Navier-Stokes Equations

    The dynamic programming approach for the control of a 3D flow governed by the stochastic Navier-Stokes equations for incompressible fluid in a bounded domain is studied. By a compactness argument, existence of solutions for the associated Hamilton-Jacobi-Bellman equation is proved. Finally, existence of an optimal control through the feedback formula and of an optimal state is discussed

  14. 3D IBFV : Hardware-Accelerated 3D Flow Visualization

    Telea, Alexandru; Wijk, Jarke J. van

    2003-01-01

    We present a hardware-accelerated method for visualizing 3D flow fields. The method is based on insertion, advection, and decay of dye. To this aim, we extend the texture-based IBFV technique for 2D flow visualization in two main directions. First, we decompose the 3D flow visualization problem in a

  15. 3D vector flow imaging

    Pihl, Michael Johannes

    The main purpose of this PhD project is to develop an ultrasonic method for 3D vector flow imaging. The motivation is to advance the field of velocity estimation in ultrasound, which plays an important role in the clinic. The velocity of blood has components in all three spatial dimensions, yet...... conventional methods can estimate only the axial component. Several approaches for 3D vector velocity estimation have been suggested, but none of these methods have so far produced convincing in vivo results nor have they been adopted by commercial manufacturers. The basis for this project is the Transverse...... on the TO fields are suggested. They can be used to optimize the TO method. In the third part, a TO method for 3D vector velocity estimation is proposed. It employs a 2D phased array transducer and decouples the velocity estimation into three velocity components, which are estimated simultaneously based on 5...

  16. On the Statistical Properties of the 3D Incompressible Navier-Stokes-Voigt Model

    Levant, Boris; Titi, Edriss S

    2009-01-01

    The Navier-Stokes-Voigt (NSV) model of viscoelastic incompressible fluid has been recently proposed as a regularization of the 3D Navier-Stokes equations for the purpose of direct numerical simulations. In this work we investigate its statistical properties by employing phenomenological heuristic arguments, in combination with Sabra shell model simulations of the analogue of the NSV model. For large values of the regularizing parameter, compared to the Kolmogorov length scale, simulations exhibit multiscaling inertial range, and the dissipation range displaying low intermittency. These facts provide evidence that the NSV regularization may reduce the stiffness of direct numerical simulations of turbulent flows, with a small impact on the energy containing scales.

  17. Practical analytical solutions for benchmarking of 2-D and 3-D geodynamic Stokes problems with variable viscosity

    Popov, I. Yu.; Lobanov, I. S.; POPOV S.I.; Popov, A. I.; Gerya, T. V.

    2014-01-01

    Geodynamic modeling is often related with challenging computations involving solution of the Stokes and continuity equations under the condition of highly variable viscosity. Based on a new analytical approach we have developed particular analytical solutions for 2-D and 3-D incompressible Stokes flows with both linearly and exponentially variable viscosity. We demonstrate how these particular solutions can be converted into 2-D and 3-D test problems suitable for...

  18. Tamed 3D Navier-Stokes Equation: Existence, Uniqueness and Regularity

    Röckner, Michael; Zhang, Xicheng

    2007-01-01

    In this paper, we prove the existence and uniqueness of a smooth solution to a tamed 3D Navier-Stokes equation in the whole space. In particular, if there exists a bounded smooth solution to the classical 3D Navier-Stokes equation, then this solution satisfies our tamed equation. Moreover, using this renormalized equation we can give a new construction for a suitable weak solution of the classical 3D Navier-Stokes equation introduced in [Scheffer: Hausdorff measure and the Navier-Stokes equat...

  19. 3D analysis of Navier-Stokes in steady state of the behavior of the flow in the Inter stage 1 of a gas turbine Frame 7; Analisis de navier-stokes tridimensional en estado estable del comportamiento del flujo en la inter etapa 1 de una turbina de gas frame 7

    Henandez Rosete, Alejandro; Mazur C, Zdzislaw [Instituto de Investigaciones Electricas, Cuernavaca, Morelos (Mexico)

    2007-11-15

    The results of the simulation by CFD (Computacional Fluid Dynamics) realized to the first stage of a gas turbine GE Frame 7 are presented. The analysis includes the 3D modeling of the flow channel in the nozzle and the movable blade to know the velocities distributions, temperatures and pressures of the main hot gas flow that are developed in the Inter stage. The results are influenced by the imposed border conditions in the properties of the main flow, the rotation of the movable blade, as well as the simulation of cooling air injection in the nozzle. The present study focuses in the validation of the model of the meshes of the ensemble nozzle-blade, for later realize an analysis of conjugated heat transfer in a model with ceramic lining type heat barrier (THB) in the movable blade. The analysis is realized in a CFD commercial code oriented to turbo-machinery using the equations of unstable flows 3D of Navier Stokes. [Spanish] Se presentan los resultados de la simulacion por CFD (Computacional Fluid Dynamics) realizada a la primera etapa de una turbina de gas GE Frame 7. El analisis incluye la modelacion tridimensional del canal de flujo en la tobera y el alabe movil para conocer las distribuciones de las velocidades, temperaturas y presiones del flujo principal de gases calientes que se desarrollan en la inter etapa. Los resultados son influenciados por las condiciones de frontera impuestos en las propiedades del flujo principal, la rotacion del alabe movil, asi como la simulacion de inyeccion de aire de enfriamiento en la tobera. El presente estudio se enfoca en la validacion del modelo de la malla del conjunto tobera-alabe, para posteriormente realizar un analisis de transferencia de calor conjugada en un modelo con recubrimiento ceramico tipo barrera termica (TBC) en el alabe movil. El analisis es realizado en un codigo de CFD comercial orientado a turbomaquinaria utilizando las ecuaciones de flujos inestables 3D de Navier Stokes.

  20. Exponential mixing of the 3D stochastic Navier-Stokes equations driven by mildly degenerate noises

    Albeverio, S.; Debussche, A; Xu, L Lihu

    2009-01-01

    We prove the strong Feller property and exponential mixing for 3D stochastic Navier-Stokes equation driven by mildly degenerate noises (i.e. all but finitely many Fourier modes are forced) via Kolmogorov equation approach.

  1. Exponential Mixing of the 3D Stochastic Navier-Stokes Equations Driven by Mildly Degenerate Noises

    We prove the strong Feller property and exponential mixing for 3D stochastic Navier-Stokes equation driven by mildly degenerate noises (i.e. all but finitely many Fourier modes being forced) via a Kolmogorov equation approach.

  2. Well posedness of a stochastic hyperviscosity-regularized 3D Navier-Stokes equation

    Ferrario, B.

    2010-01-01

    We analyse the well posedness of a stochastic hyperviscosity-regularized 3D Navier-Stokes equation; this is the Navier-Stokes equation in which the Laplace operator is replaced by its a-power for a>1. We prove existence and uniqueness for this equation assuming a>= 5/4.

  3. Study of Tip-loss Using an Inverse 3D Navier-Stokes Method

    Mikkelsen, Robert; Sørensen, Jens Nørkær; Shen, Wen Zhong; Michelsen, Jess

    2003-01-01

    3D Navier-Stokes equations combined with the actuator line technique where blade loading is applied using an inverse method. The numerical simulations shows that the method captures the tip-correction when comparing with the theories of Prandtl and Goldstein, however, the accuracy of the obtained...... results reveal that further refinements still is needed. Keywords: Tip-loss; Actuator line; 3D Navier-Stokes methods....

  4. Kolmogorov's dissipation number and the number of degrees of freedom for the 3D Navier-Stokes equations

    Cheskidov, Alexey

    2015-01-01

    Kolmogorov's theory of turbulence predicts that only wavenumbers bellow some critical value, called Kolmogorov's dissipation number, are essential to describe the evolution of a three-dimensional fluid flow. A determining wavenumber, first introduced by Foias and Prodi for the 2D Navier-Stokes equations, is a mathematical analog of Kolmogorov's number. The purpose of this paper is to prove the existence of a time-dependent determining wavenumber for the 3D Navier-Stokes equations whose time average is bounded by Kolmogorov's dissipation wavenumber for all solutions on the global attractor whose intermittency is not extreme.

  5. 3D Navier-Stokes Time Accurate Solutions Using Multipartitioning Parallel Computation Methodology

    Zha, Ge-Cheng

    1998-01-01

    A parallel CFD code solving 3D time accurate Navier-Stokes equations with multipartitioning parallel Methodology is being developed in collaboration with Ohio State University within the Air Vehicle Directorate, at Wright Patterson Air Force Base. The advantage of the multipartitioning parallel method is that the domain decomposition will not introduce domain boundaries for the implicit operators. A ring structure data communication is employed so that the implicit time accurate method can be implemented for multi-processors with the same accuracy as for the single processor. No sub-iteration is needed at the domain boundaries. The code has been validated for some typical unsteady flows, which include Coutte Flow, flow passing a cylinder. The code now is being employed for a large scale time accurate wall jet transient flow computation. 'ne preliminary results are promising. The mesh has been refined to capture more details of the flow field. The mesh refinement computation is in progress and would be difficult to successfully implement without the parallel computation techniques used. A modified version of the code with more efficient inversion of the diagonalized block matrix is currently being tested.

  6. Exact Solutions on Twisted Rings for the 3D Navier-Stokes Equations

    Funaro, Daniele

    2011-01-01

    The problem of describing the behavior of the solutions to the Navier-Stokes equations in three space dimensions has always been borderline. From one side, due to the viscosity term, smooth data seem to produce solutions with an everlasting regular behavior. On the other hand, the lack of a convincing theoretical analysis suggests the existence of possible counterexamples. In particular, one cannot exclude the blowing up of solutions in finite time even in presence of smooth data. Here we give examples of explicit solutions of the non-homogeneous equations. These are defined on a Hill's type vortex where the flow is rotating and swirling at the same time, inducing the flux to spiraling at a central node. Despite the appearance, the solution still remains very regular at the agglomeration point. The analysis may lead to a better understanding of the subtle problem of characterizing the solution space of the 3D Navier-Stokes equations. For instance, this result makes more narrow the path to the search of counte...

  7. Higher derivatives estimate for the 3D Navier-Stokes equation

    Vasseur, Alexis F.

    2009-01-01

    In this article, a non linear family of spaces, based on the energy dissipation, is introduced. This family bridges an energy space (containing weak solutions to Navier-Stokes equation) to a critical space (invariant through the canonical scaling of the Navier-Stokes equation). This family is used to get uniform estimates on higher derivatives to solutions to the 3D Navier-Stokes equations. Those estimates are uniform, up to the possible blowing-up time. The proof uses blow-up techniques. Est...

  8. Regularity of transition semigroups associated to a 3D stochastic Navier-Stokes equation

    Flandoli, F.; Romito, M.

    2006-01-01

    A 3D stochastic Navier-Stokes equation with a suitable non degenerate additive noise is considered. The regularity in the initial conditions of every Markov transition kernel associated to the equation is studied by a simple direct approach. A by-product of the technique is the equivalence of all transition probabilities associated to every Markov transition kernel.

  9. Regularity Criteria For Strong Solutions To The 3D Navier-Stokes Equations

    Younsi, Abdelhafid

    2012-01-01

    In this paper, we study the regularity problem of the 3D incompressible Navier\\~nStokes equations. We prove that the strong solution exists globally for new regularity criteria. For negligible forces, we give an improvement of the known time interval of regularity obtained in [9].

  10. Topology optimization of mass distribution problems in Stokes flow

    Gersborg-Hansen, Allan; Berggren, Martin; Dammann, Bernd

    We consider topology optimization of mass distribution problems in 2D and 3D Stokes flow with the aim of designing devices that meet target outflow rates. For the purpose of validation, the designs have been post processed using the image processing tools available in FEMLAB. In turn, this has...

  11. Direct numerical simulation of 3D transitional fluid flows

    Full text: For the numerical simulation of the 2D-3D transitional homogeneous and stratified incompressible viscous fluid flows, characterizing by the full Navier-Stokes equations, the splitting on physical factors method is used. The explicit hybrid finite difference scheme of the method has the following behaviors: the second order of accuracy in space, minimum scheme viscosity and dispersion, workable in wide range of Reynolds and Froude numbers and monotonicity. The efficiency of the developed numerical method and the advanced performance of the supercomputers allowed simulating 2D-3D transitional uncompressible viscous fluid flows around the bluff bodies in particular around a cylinder. By the numerical simulation of the fluid flows around 3D circular cylinder it was found that the transition to 3D regime arrives at Re>200. At 200< Re<300 the mode A with wavelength 3.5 d<λ<4.0 d (where d is the diameter of the cylinder) for 3D structures along the axis of a cylinder was observed. At 300< Re<400 the mode B with wavelength 0.8 d<λ<0.9 d was observed. At Re=300 the both modes A and B were observed simultaneously. The regime with large dislocations previously discovered experimentally was first obtained numerically at 210< Re<260. This regime is characterized by flow phase dislocation along the axis of the cylinder and as the effect by the amplitude fall of the lift force coefficient and the variations in the drag coefficient. There was simulated numerically the initiation of the attached internal waves behind the circular cylinder and upstream disturbance area at low Froude and moderate Reynolds numbers. (author)

  12. Intermittency and regularity issues in 3D Navier-Stokes turbulence

    Gibbon, J. D.; Doering, Charles R.

    2004-01-01

    Two related open problems in the theory of 3D Navier-Stokes turbulence are discussed in this paper. The first is the phenomenon of intermittency in the dissipation field. Dissipation-range intermittency was first discovered experimentally by Batchelor and Townsend over fifty years ago. It is characterized by spatio-temporal binary behaviour in which long, quiescent periods in the velocity signal are interrupted by short, active `events' during which there are violent fluctuations away from th...

  13. On convergence of trajectory attractors of the 3D Navier-Stokes-α model as α approaches 0

    We study the relations between the long-time dynamics of the Navier-Stokes-α model and the exact 3D Navier-Stokes system. We prove that bounded sets of solutions of the Navier-Stokes-α model converge to the trajectory attractor A0 of the 3D Navier-Stokes system as the time approaches infinity and α approaches zero. In particular, we show that the trajectory attractor Aα of the Navier-Stokes-α model converges to the trajectory attractor A0 of the 3D Navier-Stokes system as α→0+. We also construct the minimal limit Amin(subset or equal A0) of the trajectory attractor Aα as α→0+ and prove that the set Amin is connected and strictly invariant. Bibliography: 35 titles.

  14. Numerical stability of coupling schemes in the 3d/0d modelling ofairflows and blood flows

    Fouchet-Incaux, Justine; Grandmont, Céline; Martin, Sebastien

    2014-01-01

    We consider models which are classically used in the simulation of airflows and blood flows andinvestigate the numerical stability of some discretization strategies. The geometrical complexity of the networksin which air/blood flows leads to a classical decomposition of two areas: a truncated 3D geometry correspondingto the largest contribution of the domain and a 0D part connected to the 3D part, modelling air/blood flowsin smaller airways/vessels. The resulting Navier-Stokes system in the 3...

  15. 3-D Viscous Flow Analysis of an Axial Flow Pump Impeller

    Steven M. Miner

    1997-01-01

    A commercial CFD code is used to compute the flow field within the first stage impeller of a two stage axial flow pump. The code solves the 3-D Reynolds Averaged Navier Stokes equations in a rotating cylindrical coordinate system using a standard k−ε turbulence model. Stage design parameters are, rotational speed 870 rpm, flow coefficient φ=0.12, head coefficient ψ=0.06, and specific speed 2.86 (8070 US). Results from the study include relative and absolute velocities, flow angles, and static...

  16. A lattice-Boltzmann scheme of the Navier-Stokes equations on a 3D cuboid lattice

    Min, Haoda; Peng, Cheng; Wang, Lian-Ping

    2015-11-01

    The standard lattice-Boltzmann method (LBM) for fluid flow simulation is based on a square (in 2D) or cubic (in 3D) lattice grids. Recently, two new lattice Boltzmann schemes have been developed on a 2D rectangular grid using the MRT (multiple-relaxation-time) collision model, by adding a free parameter in the definition of moments or by extending the equilibrium moments. Here we developed a lattice Boltzmann model on 3D cuboid lattice, namely, a lattice grid with different grid lengths in different spatial directions. We designed our MRT-LBM model by matching the moment equations from the Chapman-Enskog expansion with the Navier-Stokes equations. The model guarantees correct hydrodynamics. A second-order term is added to the equilibrium moments in order to restore the isotropy of viscosity on a cuboid lattice. The form and the coefficients of the extended equilibrium moments are determined through an inverse design process. An additional benefit of the model is that the viscosity can be adjusted independent of the stress-moment relaxation parameter, thus improving the numerical stability of the model. The resulting cuboid MRT-LBM model is then validated through benchmark simulations using laminar channel flow, turbulent channel flow, and the 3D Taylor-Green vortex flow.

  17. XML3D and Xflow: combining declarative 3D for the Web with generic data flows.

    Klein, Felix; Sons, Kristian; Rubinstein, Dmitri; Slusallek, Philipp

    2013-01-01

    Researchers have combined XML3D, which provides declarative, interactive 3D scene descriptions based on HTML5, with Xflow, a language for declarative, high-performance data processing. The result lets Web developers combine a 3D scene graph with data flows for dynamic meshes, animations, image processing, and postprocessing. PMID:24808080

  18. Long time decay for 3D Navier-Stokes equations in Sobolev-Gevrey spaces

    Jamel Benameur

    2016-04-01

    Full Text Available In this article, we study the long time decay of global solution to 3D incompressible Navier-Stokes equations. We prove that if $u\\in{\\mathcal C}([0,\\infty,H^1_{a,\\sigma}(\\mathbb{R}^3$ is a global solution, where $H^1_{a,\\sigma}(\\mathbb{R}^3$ is the Sobolev-Gevrey spaces with parameters $a>0$ and $\\sigma>1$, then $\\|u(t\\|_{H^1_{a,\\sigma}(\\mathbb{R}^3}$ decays to zero as time approaches infinity. Our technique is based on Fourier analysis.

  19. On the stochastic 3D-Lagrangian averaged Navier-Stokes Alpha-Model with finite delay

    Caraballo Garrido, Tomás; Márquez Durán, Antonio Miguel; Real Anguas, José

    2005-01-01

    Existence and uniqueness of solutions for a stochastic version of the 3D-Lagrangian averaged Navier-Stokes (LANS-®) equation in a bounded domain and containing some hereditary characteristics are proved.

  20. 3-D Viscous Flow Analysis of a Mixed Flow Pump Impeller

    Steven M. Miner

    2001-01-01

    This paper presents the results of a study using a coarse grid to analyze the flow in the impeller of a mixed flow pump. A commercial computational fluid dynamics code (FLOTRAN) is used to solve the 3-D Reynolds Averaged Navier Stokes equations in a rotating cylindrical coordinate system. The standard k-ε turbulence model is used. The mesh for this study uses 26,000 nodes and the model is run on a SPARCstation 20. This is in contrast to typical analyses using in excess of 100,000 nodes that a...

  1. Invariant measures for the 3D Navier-Stokes-Voigt equations and their Navier-Stokes limit

    Ramos, Fabio

    2009-01-01

    The Navier-Stokes-Voigt model of viscoelastic incompressible fluid has been recently proposed as a regularization of the three-dimensional Navier-Stokes equations for the purpose of direct numerical simulations. Besides the kinematic viscosity parameter, $\

  2. Recent advances in Runge-Kutta schemes for solving 3-D Navier-Stokes equations

    Vatsa, Veer N.; Wedan, Bruce W.; Abid, Ridha

    1989-01-01

    A thin-layer Navier-Stokes has been developed for solving high Reynolds number, turbulent flows past aircraft components under transonic flow conditions. The computer code has been validated through data comparisons for flow past isolated wings, wing-body configurations, prolate spheroids and wings mounted inside wind-tunnels. The basic code employs an explicit Runge-Kutta time-stepping scheme to obtain steady state solution to the unsteady governing equations. Significant gain in the efficiency of the code has been obtained by implementing a multigrid acceleration technique to achieve steady-state solutions. The improved efficiency of the code has made it feasible to conduct grid-refinement and turbulence model studies in a reasonable amount of computer time. The non-equilibrium turbulence model of Johnson and King has been extended to three-dimensional flows and excellent agreement with pressure data has been obtained for transonic separated flow over a transport type of wing.

  3. 3D Navier-Stokes Simulations of a rotor designed for Maximum Aerodynamic Efficiency

    Johansen, Jeppe; Madsen, Helge. Aa.; Gaunaa, Mac; Bak, Christian; Sørensen, Niels

    2007-01-01

    The present paper describes the design of a three-bladed wind turbine rotor taking into account maximum aerodynamic efficiency only and not considering structural as well as offdesign issues. The rotor was designed assuming constant induction for most of the blade span, but near the tip region a...... constant load was assumed. The rotor design was obtained using an Actuator Disc model and was subsequently verified using both a free wake Lifting Line method and a full 3D Navier-Stokes solver. Excellent agreement was obtained using the three models. Global mechanical power coefficient, CP, reached a...... value of slightly above 0.51, while global thrust coefficient, CT, was 0.87. The local power coefficient, Cp, increased to slightly above the Betz limit on the inner part of the rotor as well as the local thrust coefficient, Ct, increased to a value above 1.1. This agrees well with the theory of de...

  4. Parallel computation of 3-D Navier-Stokes flowfields for supersonic vehicles

    Ryan, James S.; Weeratunga, Sisira

    1993-01-01

    Multidisciplinary design optimization of aircraft will require unprecedented capabilities of both analysis software and computer hardware. The speed and accuracy of the analysis will depend heavily on the computational fluid dynamics (CFD) module which is used. A new CFD module has been developed to combine the robust accuracy of conventional codes with the ability to run on parallel architectures. This is achieved by parallelizing the ARC3D algorithm, a central-differenced Navier-Stokes method, on the Intel iPSC/860. The computed solutions are identical to those from conventional machines. Computational speed on 64 processors is comparable to the rate on one Cray Y-MP processor and will increase as new generations of parallel computers become available.

  5. Simulations of soluble surfactants in 3D multiphase flow

    Muradoglu, Metin; Tryggvason, Gretar

    2014-10-01

    A finite-difference/front-tracking method is developed for simulations of soluble surfactants in 3D multiphase flows. The interfacial and bulk surfactant concentration evolution equations are solved fully coupled with the incompressible Navier-Stokes equations. A non-linear equation of state is used to relate interfacial surface tension to surfactant concentration at the interface. Simple test cases are designed to validate different parts of the numerical algorithm and the computational results are found to be in a good agreement with the analytical solutions. The numerical algorithm is parallelized using a domain-decomposition method. It is then applied to study the effects of soluble surfactants on the motion of buoyancy-driven bubbles in a straight square channel in nearly undeformable (spherical) and deformable (ellipsoidal) regimes. Finally the method is used to examine the effects of soluble surfactants on the lateral migration of bubbles in a pressure-driven channel flow. It is found that surfactant-induced Marangoni stresses counteract the shear-induced lift force and can reverse the lateral bubble migration completely, i.e., the contaminated bubble drifts away from the channel wall and stabilizes at the center of the channel when the surfactant-induced Marangoni stresses are sufficiently large.

  6. Preliminary examples of 3D vector flow imaging

    Pihl, Michael Johannes; Stuart, Matthias Bo; Tomov, Borislav Gueorguiev;

    2013-01-01

    This paper presents 3D vector flow images obtained using the 3D Transverse Oscillation (TO) method. The method employs a 2D transducer and estimates the three velocity components simultaneously, which is important for visualizing complex flow patterns. Data are acquired using the experimental...... ultrasound scanner SARUS on a flow rig system with steady flow. The vessel of the flow-rig is centered at a depth of 30 mm, and the flow has an expected 2D circular-symmetric parabolic prole with a peak velocity of 1 m/s. Ten frames of 3D vector flow images are acquired in a cross-sectional plane orthogonal...... acquisition as opposed to magnetic resonance imaging (MRI). The results demonstrate that the 3D TO method is capable of performing 3D vector flow imaging....

  7. Grounding line dynamics inferred from a 3D full-Stokes model solving the contact problem

    Favier, Lionel; Gagliardini, Olivier; Durand, Gael; Zwinger, Thomas

    2010-05-01

    The mass balance of marine ice-sheets, such as the West Antarctic Ice Sheet, is mostly controlled by their grounding line dynamics. Most numerical models simulating marine ice-sheets involve simplifications and do not include all the stress gradients. First results obtained with a 3D full-Stokes model for the grounded ice-sheet / floating ice-shelf transition, using the finite-element code Elmer/Ice, are presented. The initial geometry, which takes into account a dome and a calving front, has been laterally extruded from a previously investigated 2D flowline geometry. The grounding line migration is computed by solving the contact problem between the ice and the rigid downward sloping bedrock, where a non linear friction law is applied in the two horizontal directions. The evolutions of the sea-air and sea-ice interfaces are determined by the solution of a local transport equation. The consistency between the 3D model and the analogous results of the flowline model is shown by comparing the results in the basic extruded case, with no normal flux through lateral boundaries. Thereafter, spatially non uniform perturbations are introduced, to simulate the grounding line dynamics under fully three-dimensional perturbations.

  8. 3D Flow reconstruction using ultrasound PIV

    Poelma, C.; Mari, J. M.; Foin, N.; Tang, M.-X.; Krams, R; Caro, C.G.; Weinberg, P.D.; Westerweel, J.

    2009-01-01

    Ultrasound particle image velocimetry (PIV) can be used to obtain velocity fields in non-transparent geometries and/or fluids. In the current study, we use this technique to document the flow in a curved tube, using ultrasound contrast bubbles as flow tracer particles. The performance of the technique is first tested in a straight tube, with both steady laminar and pulsatile flows. Both experiments confirm that the technique is capable of reliable measurements. A number of adaptations are int...

  9. 3-D numerical modelling of flow around a groin

    Miller, R.; Roulund, A.; Sumer, B. Mutlu;

    2003-01-01

    A 3-D flow code, EllipSys3D, has been implemented to simulate the 3-D flow around a groin in steady current. The k  turbulence model has been used for closure. Two kinds of groins are considered: (1) A vertical-wall groin, and (2) A groin with a side slope. Steady-flow simulations were conducted....... The paper reports early results of the investigation. The simulations capture main features of the flow around the groin. The horseshoe vortex in front of the vertical-wall groin is resolved. The vortex shedding at the head is not resolved because no transient flow simulations have been conducted at...

  10. Anomalous dissipation and energy cascade in 3D inviscid flows

    Dascaliuc, Radu

    2011-01-01

    Adopting the setting for the study of existence and scale locality of the energy cascade in 3D viscous flows in physical space introduced in [arXiv:1101.2193] to 3D inviscid flows, it is shown that the anomalous dissipation is indeed capable of triggering the cascade which then continues ad infinitum, confirming Onsager's predictions.

  11. The new high resolution method of Godunov`s type for 3D viscous flow calculations

    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)

  12. Regimes of nonlinear depletion and regularity in the 3D Navier–Stokes equations

    The periodic 3D Navier–Stokes equations are analyzed in terms of dimensionless, scaled, L2m-norms of vorticity Dm (1 ⩽ m < ∞). The first in this hierarchy, D1, is the global enstrophy. Three regimes naturally occur in the D1 − Dm plane. Solutions in the first regime, which lie between two concave curves, are shown to be regular, owing to strong nonlinear depletion. Moreover, numerical experiments have suggested, so far, that all dynamics lie in this heavily depleted regime [1]; new numerical evidence for this is presented. Estimates for the dimension of a global attractor and a corresponding inertial range are given for this regime. However, two more regimes can theoretically exist. In the second, which lies between the upper concave curve and a line, the depletion is insufficient to regularize solutions, so no more than Leray's weak solutions exist. In the third, which lies above this line, solutions are regular, but correspond to extreme initial conditions. The paper ends with a discussion on the possibility of transition between these regimes. (paper)

  13. Regularity for 3D Navier-Stokes equations in terms of two components of the vorticity

    Sadek Gala

    2010-10-01

    Full Text Available We establish regularity conditions for the 3D Navier-Stokes equation via two components of the vorticity vector. It is known that if a Leray-Hopf weak solution $u$ satisfies $$ ilde{omega}in L^{2/(2-r}(0,T;L^{3/r}(mathbb{R}^3quad hbox{with }0

  14. On the Regularity of the Solutions for Cauchy Problem of Incompressible 3D Navier-Stokes Equation

    Lin, Qun

    2013-01-01

    In this paper we will prove that the vorticity belongs to $L^{\\infty}(0, T; L^2(R^3))$ for the Cauchy problem of 3D incompressible Navier-Stokes equation, then the existence of a global smooth solution is obtained. Our approach is to construct a set of auxiliary problems to approximate the original one for vorticity equation.

  15. Lattice Boltzmann Method for 3-D Flows with Curved Boundary

    Mei, Renwei; Shyy, Wei; Yu, Dazhi; Luo, Li-Shi

    2002-01-01

    In this work, we investigate two issues that are important to computational efficiency and reliability in fluid dynamics applications of the lattice, Boltzmann equation (LBE): (1) Computational stability and accuracy of different lattice Boltzmann models and (2) the treatment of the boundary conditions on curved solid boundaries and their 3-D implementations. Three athermal 3-D LBE models (D3QI5, D3Ql9, and D3Q27) are studied and compared in terms of efficiency, accuracy, and robustness. The boundary treatment recently developed by Filippova and Hanel and Met et al. in 2-D is extended to and implemented for 3-D. The convergence, stability, and computational efficiency of the 3-D LBE models with the boundary treatment for curved boundaries were tested in simulations of four 3-D flows: (1) Fully developed flows in a square duct, (2) flow in a 3-D lid-driven cavity, (3) fully developed flows in a circular pipe, and (4) a uniform flow over a sphere. We found that while the fifteen-velocity 3-D (D3Ql5) model is more prone to numerical instability and the D3Q27 is more computationally intensive, the 63Q19 model provides a balance between computational reliability and efficiency. Through numerical simulations, we demonstrated that the boundary treatment for 3-D arbitrary curved geometry has second-order accuracy and possesses satisfactory stability characteristics.

  16. Uniform regularity and vanishing dissipation limit for the full compressible Navier-Stokes system in 3-D bounded domain

    Yong, Wang

    2015-01-01

    In the present paper, we study the uniform regularity and vanishing dissipation limit for the full compressible Navier-Stokes system whose viscosity and heat conductivity are allowed to vanish at different order. The problem is studied in a 3-D bounded domain with Navier-slip type boundary conditions \\eqref{1.9}. It is shown that there exists a unique strong solution to the full compressible Navier-Stokes system with the boundary conditions \\eqref{1.9} in a finite time interval which is indep...

  17. Localization of small obstacles in Stokes flow

    We want to detect small obstacles immersed in a fluid flowing in a larger bounded domain Ω in the three-dimensional case. We assume that the fluid motion is governed by the steady-state Stokes equations. We make a measurement on a part of the exterior boundary ∂Ω and then take a Kohn–Vogelius approach to locate these obstacles. We use here the notion of the topological derivative in order to determine the number of objects and their rough locations. Thus we first establish an asymptotic expansion of the solution of the Stokes equations in Ω when we add small obstacles inside. Then, we use it to find a topological asymptotic expansion of the considered Kohn–Vogelius functional which gives us the formula of its topological gradient. Finally, we make some numerical simulations exploring the efficiency and the limits of this method. (paper)

  18. Parallel Processor for 3D Recovery from Optical Flow

    Jose Hugo Barron-Zambrano

    2009-01-01

    Full Text Available 3D recovery from motion has received a major effort in computer vision systems in the recent years. The main problem lies in the number of operations and memory accesses to be performed by the majority of the existing techniques when translated to hardware or software implementations. This paper proposes a parallel processor for 3D recovery from optical flow. Its main feature is the maximum reuse of data and the low number of clock cycles to calculate the optical flow, along with the precision with which 3D recovery is achieved. The results of the proposed architecture as well as those from processor synthesis are presented.

  19. Numerical analysis of 3-D potential flow in centrifugal turbomachines

    Daiguji, H.

    1983-09-01

    A numerical method is developed for analysing a three-dimensional steady incompressible potential flow through an impeller in centrifugal turbomachines. The method is the same as the previous method which was developed for the axial flow turbomachines, except for some treatments in the downstream region. In order to clarify the validity and limitation of the method, a comparison with the existing experimental data and numerical results is made for radial flow compressor impellers. The calculated blade surface pressure distributions almost coincide with the quasi-3-D calculation by Krimerman and Adler (1978), but are different partly from the quasi-3-D calculation using one meridional flow analysis. It is suggested from this comparison that the flow through an impeller with high efficiency near the design point can be predicted by this fully 3-D numerical method.

  20. Effect of vorticity coherence on energy-enstrophy bounds for the 3D Navier-Stokes equations

    Dascaliuc, Radu; Jolly, Michael S

    2015-01-01

    Bounding curves in the energy,enstrophy-plane are derived for the 3D Navier-Stokes equations under an assumption on coherence of the vorticity direction. The analysis in the critical case where the direction is H\\"older continuous with exponent $r=1/2$ results in a curve with extraordinarily large maximal enstrophy (exponential in Grashof), in marked contrast to the subcritical case, $r>1/2$ (algebraic in Grashof).

  1. On the Coupling of Incompressible Stokes or Navier–Stokes and Darcy Flows Through Porous Media

    Girault, V.

    2012-11-03

    In this chapter, we present the theoretical analysis of coupled incompressible Navier-Stokes (or Stokes) flows and Darcy flows with the Beavers-Joseph-Saffman interface condition. We discuss alternative interface and porous media models. We review some finite element methods used by several authors in this coupling and present numerical experiments.

  2. Asymptotic behaviour of the non-autonomous 3D Navier-Stokes problem with coercive force

    Vorotnikov, Dmitry

    2010-01-01

    We construct pullback attractors to the weak solutions of the three-dimensional Dirichlet problem for the incompressible Navier-Stokes equations in the case when the external force may become unbounded as time goes to plus or minus infinity.

  3. Numerical simulation of a 3-D flow within a storage area hexagonal modular pavement systems

    This numerical study has been performed to predict the flow patterns and characteristics within a storage area Hexagonal Modular Pavement Systems. Throughout the design and planning period for future construction are increasingly integrating computational fluid dynamics (CFD) into the process. A commercially known software, FLOW-3D, is applied to numerically solve the Navier-stokes equations for solution domains which are separated into three regions with overlapping boundaries to efficiently accommodate the grid resolutions, namely the honeycomb shaped modular, gravel and combined honeycomb shaped modular with gravel fill. The filtration of the fluid within the interstices of a permeable pavement is evaluated by integrating the Reynolds Averaged Navier-Stokes equations (RANS) inside the voids rather than making use of the widespread porous media approach. In conclusion, the results from numerical simulation are generally well agreed with the existing data and flow information such as flow patterns at increased flow, discharge rate and pressure is obtained to be used for engineering design purpose. Overall, the potential for FLOW-3D to model various geometries and configurations appears great. It should be noted that CFD should not be considered a complete replacement for physical modelling; however, it can definitely be used as a supplementary tool throughout the pavement design process.

  4. Serrin blow-up criterion for strong solutions to the 3-D compressible nematic liquid crystal flows with vacuum

    Qiao Liu

    2013-01-01

    In this article, we extend the well-known Serrin's blow-up criterion for solutions of the 3-D incompressible Navier-Stokes equations to the 3-D compressible nematic liquid crystal flows where the initial vacuum is allowed. It is proved that for the initial-boundary value problem of the 3-D compressible nematic liquid crystal flows in a bounded domain, the strong solution exists globally if the velocity satisfies the Serrin's condition and $L^1(0,T;L^{infty})$-norm of the gradient of th...

  5. Serrin blow-up criterion for strong solutions to the 3-D compressible nematic liquid crystal flows with vacuum

    Qiao Liu

    2013-04-01

    Full Text Available In this article, we extend the well-known Serrin's blow-up criterion for solutions of the 3-D incompressible Navier-Stokes equations to the 3-D compressible nematic liquid crystal flows where the initial vacuum is allowed. It is proved that for the initial-boundary value problem of the 3-D compressible nematic liquid crystal flows in a bounded domain, the strong solution exists globally if the velocity satisfies the Serrin's condition and $L^1(0,T;L^{infty}$-norm of the gradient of the velocity is bounded.

  6. 3D Printed Micro Free-Flow Electrophoresis Device.

    Anciaux, Sarah K; Geiger, Matthew; Bowser, Michael T

    2016-08-01

    The cost, time, and restrictions on creative flexibility associated with current fabrication methods present significant challenges in the development and application of microfluidic devices. Additive manufacturing, also referred to as three-dimensional (3D) printing, provides many advantages over existing methods. With 3D printing, devices can be made in a cost-effective manner with the ability to rapidly prototype new designs. We have fabricated a micro free-flow electrophoresis (μFFE) device using a low-cost, consumer-grade 3D printer. Test prints were performed to determine the minimum feature sizes that could be reproducibly produced using 3D printing fabrication. Microfluidic ridges could be fabricated with dimensions as small as 20 μm high × 640 μm wide. Minimum valley dimensions were 30 μm wide × 130 μm wide. An acetone vapor bath was used to smooth acrylonitrile-butadiene-styrene (ABS) surfaces and facilitate bonding of fully enclosed channels. The surfaces of the 3D-printed features were profiled and compared to a similar device fabricated in a glass substrate. Stable stream profiles were obtained in a 3D-printed μFFE device. Separations of fluorescent dyes in the 3D-printed device and its glass counterpart were comparable. A μFFE separation of myoglobin and cytochrome c was also demonstrated on a 3D-printed device. Limits of detection for rhodamine 110 were determined to be 2 and 0.3 nM for the 3D-printed and glass devices, respectively. PMID:27377354

  7. Vertical Flow Lithography for Fabrication of 3D Anisotropic Particles.

    Habasaki, Shohei; Lee, Won Chul; Yoshida, Shotaro; Takeuchi, Shoji

    2015-12-22

    A microfluidics-based method for the 3D fabrication of anisotropic particles is reported. The method uses a vertical microchannel where tunable light patterns solidify photocurable resins for stacking multiple layers of the resins, thus enabling an application of stereolithography concepts to conventional flow lithography. Multilayered, tapered, and angular compartmental microparticles are demonstrated. PMID:26551590

  8. Investigating dynamic stall, 3-D and rotational effects on wind turbine blades by means of an unsteady quasi-3D Navier-Stokes solver

    Chaviaropoulos, P.K. [CRES-Center for Renewable Energy Sources, Pikermi Attiki (Greece)

    1997-08-01

    The blade element codes provide surprisingly accurate predictions of the aerodynamic loads provided that they are `fed` with proper lift and drag - incidence curves for the profiles mounted on the rotor blades. The evident question is how one can obtain such data. It is common experience that the use of the mostly available steady two-dimensional profile data may lead to serious discrepancies between measured and simulated loads. Although several correction techniques have been proposed as a remedy during the last years, from simplified dynamic stall models suitably tuned for wind turbines to 3-D correction schemes for profile data, the problem is by no means over-passed. Especially for the three-dimensional effects it seems that part of the difficulty is due to our limited understanding of the physical mechanism which is responsible for the extra loading of the inner part of the blades. Recognizing the importance of the above aspects two relevant Joule projects have been launched, the concluded `Dynamic Stall and 3-D Effects` JOU2-CT93-0345 and the ongoing `VISCWIND` JOR3-CT95-0007 project. Part of the activities in the first and all the activities in the second project are devoted to the identification and quantification of the dynamic stall and three-dimensional effects experienced by the wind turbine blades using Navier-Stokes computations. The contribution of CRES in these two projects is briefly presented in this paper. (EG)

  9. The 3D Flow Field Around an Embedded Planet

    Fung, Jeffrey; Wu, Yanqin

    2015-01-01

    Understanding the 3D flow topology around a planet embedded in its natal disk is crucial to the study of planet formation. 3D modifications to the well-studied 2D flow topology have the potential to resolve longstanding problems in both planet migration and accretion. We present a detailed analysis of the 3D isothermal flow field around a 5 Earth-mass planet on a fixed circular orbit, simulated using our high-resolution multi-GPU hydrodynamics code PEnGUIn. We show that, overall, the horseshoe region has a columnar structure extending vertically much beyond the Hill sphere of the planet. This columnar structure is only broken for some of the widest horseshoe streamlines, along which high altitude fluid descends and converges rapidly toward the planet, enters its Bondi sphere, performs one horseshoe turn, and exits radially in the midplane. A portion of this flow gathers enough speed to exit the horseshoe region altogether. We call this newly identified feature the "transient" horseshoe flow. As the flow conti...

  10. Analysis of the velocity tracking control problem for the 3D evolutionary Navier-Stokes equations

    Casas Rentería, Eduardo; Chrysafinos, Konstantinos

    2016-01-01

    The velocity tracking problem for the evolutionary Navier–Stokes equations in three dimensions is studied. The controls are of distributed type and are submitted to bound constraints. The classical cost functional is modified so that a full analysis of the control problem is possible. First and second order necessary and sufficient optimality conditions are proved. A fully discrete scheme based on a discontinuous (in time) Galerkin approach, combined with conforming finite element subspaces i...

  11. On Energy Cascades in the Forced 3D Navier-Stokes Equations

    Dascaliuc, R.; Grujić, Z.

    2016-06-01

    We show—in the framework of physical scales and (K_1,K_2)-averages—that Kolmogorov's dissipation law combined with the smallness condition on a Taylor length scale is sufficient to guarantee energy cascades in the forced Navier-Stokes equations. Moreover, in the periodic case we establish restrictive scaling laws—in terms of Grashof number—for kinetic energy, energy flux, and energy dissipation rate. These are used to improve our sufficient condition for forced cascades in physical scales.

  12. Sufficiency Class for Global (in Time) Solutions to the 3D-Navier-Stokes Equations

    Gill, Tepper L.; Zachary, Woodford W

    2007-01-01

    A well-known unsolved problem (in the classical theory of fluid mechanics) is to identify a set of initial velocities, which may depend on the viscosity, the body forces and possibly the boundary of the fluid that will allow global in time solutions to the three-dimensional Navier-Stokes equations. (These equations describe the time evolution of the fluid velocity and pressure of an incompressible viscous homogeneous Newtonian fluid in terms of a given initial velocity and given external body...

  13. 3D modelling of edge parallel flow asymmetries

    The issue of parallel flows asymmetries in the edge plasma is tackled with a new first principle transport and turbulence code. TOKAM-3D is a 3D full-torus fluid code that can be used both in diffusive and turbulent regimes and covers either exclusively closed flux surfaces or both open and closed field lines in limiter geometry. Two independent mechanisms susceptible to lead to large amplitude asymmetric parallel flows are evidenced. Global ExB drifts coupled with the presence of the limiter break the poloidal symmetry and can generate large amplitude parallel flows even with poloidally uniform transport coefficients. On the other hand, turbulent transport in the edge exhibits a strong ballooning of the radial particle flux generating an up-down m = 1, n = 0 structure on the parallel velocity. The combination of both mechanisms in complete simulations leads to a poloidal and radial distribution of the parallel velocity comparable to experimental results.

  14. The 3D Flow Field Around an Embedded Planet

    Fung, Jeffrey; Artymowicz, Pawel; Wu, Yanqin

    2015-10-01

    3D modifications to the well-studied 2D flow topology around an embedded planet have the potential to resolve long-standing problems in planet formation theory. We present a detailed analysis of the 3D isothermal flow field around a 5 Earth-mass planet on a fixed circular orbit, simulated using our graphics processing unit hydrodynamics code PEnGUIn. We find that, overall, the horseshoe region has a columnar structure extending vertically much beyond the Hill sphere of the planet. This columnar structure is only broken for some of the widest horseshoe streamlines, along which high altitude fluid descends rapidly into the planet’s Bondi sphere, performs one horseshoe turn, and exits the Bondi sphere radially in the midplane. A portion of this flow exits the horseshoe region altogether, which we refer to as the “transient” horseshoe flow. The flow continues as it rolls up into a pair of up-down symmetric horizontal vortex lines shed into the wake of the planet. This flow, unique to 3D, affects both planet accretion and migration. It prevents the planet from sustaining a hydrostatic atmosphere due to its intrusion into the Bondi sphere, and leads to a significant corotation torque on the planet, unanticipated by 2D analysis. In the reported simulation, starting with a {{Σ }}˜ {r}-3/2 radial surface density profile, this torque is positive and partially cancels with the negative differential Lindblad torque, resulting in a factor of three slower planet migration rate. Finally, we report 3D effects can be suppressed by a sufficiently large disk viscosity, leading to results similar to 2D.

  15. On the physics of shear flows in 3D geometry

    Recent experiments have shown the importance of multi-scale (long-range) mechanisms in the transition to improved confinement regimes and the key role of electric fields to amplify them. Flows driven by turbulence might explain such experimental observation, which would imply to consider the importance of 3-D effects on the energy transfer between flows and turbulence. Comparative studies in different magnetic configurations (tokamaks vs stellarators), diagnostic development and large-scale simulation are needed to assess the importance of multi-scale physics in the development of sheared flows. (author)

  16. Comparison of OpenFOAM and EllipSys3D for neutral atmospheric flow over complex terrain

    Cavar, Dalibor; Réthoré, Pierre-Elouan; Bechmann, Andreas; Sørensen, Niels N.; Martinez, Benjamin, Jr; Zahle, Frederik; Berg, Jacob; Kelly, Mark C.

    2016-01-01

    The flow solvers OpenFOAM and EllipSys3D are compared in the case of neutral atmospheric flow over terrain using the test cases of Askervein and Bolund hills. Both solvers are run using the steady-state Reynolds-averaged Navier–Stokes k– turbulence model. One of the main modeling differences between the two solvers is the wall-function approach. The Open-FOAM v.1.7.1 uses a Nikuradse’s sand roughness model, while EllipSys3D uses a model based on the atmosphericroughness length. It is found th...

  17. Numerical Investigation of 3D Flow Around Two Tandem Cylinders

    Kalvig, Ragnhild Birgitte Hidle

    2015-01-01

    Circular cylinders in tandem arrangement are used in many marine applications like dual pipelines and dual risers. Turbulent flow in 3D around two tandem cylinders is simulated numerically using Large Eddy Simulation (LES) with a Smagorinsky subgrid scale model. The Reynolds number based on the cylinder diameter of 1 meter and free stream velocity of $U=1.31$ m/s is 13100, which is in the subcritical flow regime. The center-to-center spacing between the cylinders is $S/D=5$. The software used...

  18. A Computational Model for Suspended Large Rigid Bodies in 3D Unsteady Viscous Flows

    Xiao, Feng

    1999-11-01

    A 3D numerical model for computing large rigid objects suspended in fluid flow has been developed. Rather than calculating the surface pressure upon the solid body, we evaluate the net force and torque based on a volume force formulation. The total effective force is obtained by summing up the forces at the Eulerian grids occupied by the rigid body. The effects of the moving bodies are coupled to the fluid flow by imposing the velocity field of the bodies to the fluid. A Poisson equation is used to compute the pressure over the whole domain. The objects are identified by color functions and calculated by the PPM scheme and a tangent function transformation which scales the transition region of the computed interface to a compact thickness. The model is then implemented on a parallel computer of distributed memory and validated with Stokes and low Reynolds number flows.

  19. Optimal propulsive flapping in Stokes flows

    Swimming fish and flying insects use the flapping of fins and wings to generate thrust. In contrast, microscopic organisms typically deform their appendages in a wavelike fashion. Since a flapping motion with two degrees of freedom is able, in theory, to produce net forces from a time-periodic actuation at all Reynolds numbers, we compute in this paper the optimal flapping kinematics of a rigid spheroid in a Stokes flow. The hydrodynamics for the force generation and energetics of the flapping motion is solved exactly. We then compute analytically the gradient of a flapping efficiency in the space of all flapping gaits and employ it to derive numerically the optimal flapping kinematics as a function of the shape of the flapper and the amplitude of the motion. The kinematics of optimal flapping are observed to depend weakly on the flapper shape and are very similar to the figure-eight motion observed in the motion of insect wings. Our results suggest that flapping could be a exploited experimentally as a propulsion mechanism valid across the whole range of Reynolds numbers. (paper)

  20. Optimal propulsive flapping in Stokes flows

    Was, Loic

    2014-01-01

    Swimming fish and flying insects use the flapping of fins and wings to generate thrust. In contrast, microscopic organisms typically deform their appendages in a wavelike fashion. Since a flapping motion with two degrees of freedom is able, in theory, to produce net forces from a time-periodic actuation at all Reynolds number, we compute in this paper the optimal flapping kinematics of a rigid spheroid in a Stokes flow. The hydrodynamics for the force generation and energetics of the flapping motion is solved exactly. We then compute analytically the gradient of a flapping efficiency in the space of all flapping gaits and employ it to derive numerically the optimal flapping kinematics as a function of the shape of the flapper and the amplitude of the motion. The kinematics of optimal flapping are observed to depend weakly on the flapper shape and are very similar to the figure-eight motion observed in the motion of insect wings. Our results suggest that flapping could be a exploited experimentally as a propul...

  1. Optimal propulsive flapping in Stokes flows.

    Was, Loïc; Lauga, Eric

    2014-03-01

    Swimming fish and flying insects use the flapping of fins and wings to generate thrust. In contrast, microscopic organisms typically deform their appendages in a wavelike fashion. Since a flapping motion with two degrees of freedom is able, in theory, to produce net forces from a time-periodic actuation at all Reynolds numbers, we compute in this paper the optimal flapping kinematics of a rigid spheroid in a Stokes flow. The hydrodynamics for the force generation and energetics of the flapping motion is solved exactly. We then compute analytically the gradient of a flapping efficiency in the space of all flapping gaits and employ it to derive numerically the optimal flapping kinematics as a function of the shape of the flapper and the amplitude of the motion. The kinematics of optimal flapping are observed to depend weakly on the flapper shape and are very similar to the figure-eight motion observed in the motion of insect wings. Our results suggest that flapping could be a exploited experimentally as a propulsion mechanism valid across the whole range of Reynolds numbers. PMID:24343130

  2. Mesh Resolution Effect on 3D RANS Turbomachinery Flow Simulations

    Yershov, Sergiy

    2016-01-01

    The paper presents the study of the effect of a mesh refinement on numerical results of 3D RANS computations of turbomachinery flows. The CFD solver F, which based on the second-order accurate ENO scheme, is used in this study. The simplified multigrid algorithm and local time stepping permit decreasing computational time. The flow computations are performed for a number of turbine and compressor cascades and stages. In all flow cases, the successively refined meshes of H-type with an approximate orthogonalization near the solid walls were generated. The results obtained are compared in order to estimate their both mesh convergence and ability to resolve the transonic flow pattern. It is concluded that for thorough studying the fine phenomena of the 3D turbomachinery flows, it makes sense to use the computational meshes with the number of cells from several millions up to several hundred millions per a single turbomachinery blade channel, while for industrial computations, a mesh of about or less than one mil...

  3. Challenges in Lagrangian transport and predictability in 3D flows

    Branicki, M.; Wiggins, S.; Kirwan, A. D.; Malek-Madani, R.

    2011-12-01

    The interplay between the geometrical theory of dynamical systems and the trajectory-based description of aperiodically time-dependent fluid flows has led to significant advances in understanding the role of chaotic transport in geophysical flows at scales dominated by advection. Lagrangian transport analysis utilizing either the time-dependent geometry of intersecting stable and unstable manifolds of the so-called Distinguished Hyperbolic Trajectories (DHT), or ridges of finite-time Lyapunov exponent fields (LCS), provide a much needed and complementary insight into ephemeral mechanisms responsible for the existence of `leaky' transport barriers and 'leaky' mesoscale eddies. However, to date most oceanic applications have been confined to 2D analysis of near surface regions in 'perfect' flows not accounting for model or measurement error, and with the tacit assumption of negligible vertical velocities. I will systematically address issues concerning the regimes of applicability of two-dimensional analysis in 3D aperiodically time-dependent flows, as well as outstanding challenges in fully 3D Lagrangian transport analysis. Even for perfect horizontal velocities, little is known about the vertical extent of stable/unstable manifolds associated with DHTs and/or other special structures relevant to stratified 3D flows. In particular, their sensitivity to errors in the vertical velocities and data assimilation methods has been little studied. Rigorous results regarding the above issues will be illustrated by revealing and mathematically tractable toy models, as well as examples from a detailed study in an eddy-rich region from the Gulf of Mexico and the Mediterranean. New ways of quantifying the uncertainty in Lagrangian predictions will also be presented.

  4. 3-D NUMERICAL SIMULATIONS OF FLOW LOSS IN HELICAL CHANNEL

    ZHAO Ling-zhi; PENG Yan; LU Fang; LI Jian; LI Ran; LIU Bao-lin

    2012-01-01

    The flow loss of a helical channel Magnetohydrodynamic (MHD) thruster without MHD effect was numerically studied with 3-D simulations,and a flow loss coefficient ξ was defined to quantify the flow loss and its influencing factors were studied.The results show that ξ decreases in a first-order exponential manner with the pitch of a helical wall and the Reynolds number,and it declines slowly when t / T > 0.2 and Re > 105,a flow guide makes the flow more smooth and uniform,especially in the flow guide and helical wall sub-regions and thus reduces the flow loss greatly,by about 30% with the averaged value of ξ from 0.0385to 0.027,a rectifier weakens the helical flow and strengthens the axial one in the rectifier and outlet sub-regions,thus reduces the rotational kinetic pressure with the averaged value of ξ declining about 4% from 0.0385 to 0.037,and ξ decreases with a rectifier's axial length when Re > 105.

  5. Laminar Validation Cases for the Incompressible Flow Model in ALE3D

    Ortega, J

    2002-07-16

    To benchmark the incompressible flow model in ALE3D, two test cases are conducted. The first case of two-dimensional flow over a flat plate is selected because it provides a straightforward example to determine whether or not ALE3D can grow a boundary layer by viscous diffusion. The benefit of the flat plate problem is that under certain conditions, the governing Navier-Stokes equations can be simplified and solved with numerical techniques, providing an independent result that can be compared with the solution from ALE3D. The second test case is that of two-dimensional, laminar flow about a circular cylinder. This test case is selected because it provides the complexity of an unsteady bluff-body wake in which vorticity is periodically shed from the surface of the cylinder. Since this canonical flow problem has been studied extensively both experimentally and computationally, the results from ALE3D can be compared with those presented in the literature. The results for the flat plate case demonstrate that the implicit time integration scheme results in an approximate twenty-four-fold reduction of the simulation time over that of the explicit time integration scheme. On the other hand, a problematic trend is observed in the explicit time integration scheme used in the flat plate case. The errors in both the velocity and shear stress are not reduced through grid refinement as one might expect. Another trend that raises concern with the flat plate problem is the sensitivity of the velocity and shear stress to the outlet zero natural boundary condition. In all of the flat plate simulations, at least one of the calculated quantities varies quite noticeably near the outlet of the flow domain. For the case of a circular cylinder in which an explicit time integration scheme is employed, both the drag coefficient and Strouhal number demonstrate trends of converging to a solution that compares favorably with results from other studies in the literature.

  6. A numerical study of the transition to oscillatory flow in 3D lid-driven cubic cavity flows

    Chiu, Shang-Huan; He, Jiwen; Guo, Aixia; Glowinski, Roland

    2016-01-01

    In this article, three dimensional (3D) lid-driven cubic cavity flows have been studied numerically for various values of Reynolds number ($Re$). The numerical solution of the Navier-Stokes equations modeling incompressible viscous fluid flow in a cubic cavity is obtained via a methodology combining a first order accurate operator-splitting, $L^2$-projection Stokes solver, a wave-like equation treatment of the advection and finite element methods. The numerical results obtained for Re$=$400, 1000, and 3200 show a good agreement with available numerical and experimental results in literature. Simulation results predict that the critical Re$_{cr}$ for the transition from steady flow to oscillatory (a Hopf bifurcation) is somewhere in [1870, 1875] for the mesh size $h=1/96$. Via studying the flow field distortion of fluid flow at Re before and after Re$_{cr}$, the occurrence of the first pair of Taylor-G\\"ortler-like vortices is connected to the flow field distortion at the transition from steady flow to oscilla...

  7. Approximate controllability of Lagrangian trajectories of the 3D Navier–Stokes system by a finite-dimensional force

    In the Eulerian approach, the motion of an incompressible fluid is usually described by the velocity field which is given by the Navier–Stokes system. The velocity field generates a flow in the space of volume-preserving diffeomorphisms. The latter plays a central role in the Lagrangian description of a fluid, since it allows to identify the trajectories of the individual particles. In this paper, we show that the velocity field of the fluid and the corresponding flow of diffeomorphisms can be simultaneously approximately controlled using a finite-dimensional external force. The proof is based on some methods from the geometric control theory introduced by Agrachev and Sarychev. (paper)

  8. A parallel block multi-level preconditioner for the 3D incompressible Navier-Stokes equations

    The development of robust and efficient algorithms for both steady-state simulations and fully implicit time integration of the Navier-Stokes equations is an active research topic. To be effective, the linear subproblems generated by these methods require solution techniques that exhibit robust and rapid convergence. In particular, they should be insensitive to parameters in the problem such as mesh size, time step, and Reynolds number. In this context, we explore a parallel preconditioner based on a block factorization of the coefficient matrix generated in an Oseen nonlinear iteration for the primitive variable formulation of the system. The key to this preconditioner is the approximation of a certain Schur complement operator by a technique first proposed by Kay, Loghin, and Wathen [SIAM J. Sci. Comput., 2002] and Silvester, Elman, Kay, and Wathen [J. Comput. Appl. Math. 128 (2001) 261]. The resulting operator entails subsidiary computations (solutions of pressure Poisson and convection-diffusion subproblems) that are similar to those required for decoupled solution methods; however, in this case these solutions are applied as preconditioners to the coupled Oseen system. One important aspect of this approach is that the convection-diffusion and Poisson subproblems are significantly easier to solve than the entire coupled system, and a solver can be built using tools developed for the subproblems. In this paper, we apply smoothed aggregation algebraic multigrid to both subproblems. Previous work has focused on demonstrating the optimality of these preconditioners with respect to mesh size on serial, two-dimensional, steady-state computations employing geometric multi-grid methods; we focus on extending these methods to large-scale, parallel, three-dimensional, transient and steady-state simulations employing algebraic multigrid (AMG) methods. Our results display nearly optimal convergence rates for steady-state solutions as well as for transient solutions over a

  9. INS3D - NUMERICAL SOLUTION OF THE INCOMPRESSIBLE NAVIER-STOKES EQUATIONS IN THREE-DIMENSIONAL GENERALIZED CURVILINEAR COORDINATES (IBM VERSION)

    Kwak, D.

    1994-01-01

    INS3D computes steady-state solutions to the incompressible Navier-Stokes equations. The INS3D approach utilizes pseudo-compressibility combined with an approximate factorization scheme. This computational fluid dynamics (CFD) code has been verified on problems such as flow through a channel, flow over a backwardfacing step and flow over a circular cylinder. Three dimensional cases include flow over an ogive cylinder, flow through a rectangular duct, wind tunnel inlet flow, cylinder-wall juncture flow and flow through multiple posts mounted between two plates. INS3D uses a pseudo-compressibility approach in which a time derivative of pressure is added to the continuity equation, which together with the momentum equations form a set of four equations with pressure and velocity as the dependent variables. The equations' coordinates are transformed for general three dimensional applications. The equations are advanced in time by the implicit, non-iterative, approximately-factored, finite-difference scheme of Beam and Warming. The numerical stability of the scheme depends on the use of higher-order smoothing terms to damp out higher-frequency oscillations caused by second-order central differencing. The artificial compressibility introduces pressure (sound) waves of finite speed (whereas the speed of sound would be infinite in an incompressible fluid). As the solution converges, these pressure waves die out, causing the derivation of pressure with respect to time to approach zero. Thus, continuity is satisfied for the incompressible fluid in the steady state. Computational efficiency is achieved using a diagonal algorithm. A block tri-diagonal option is also available. When a steady-state solution is reached, the modified continuity equation will satisfy the divergence-free velocity field condition. INS3D is capable of handling several different types of boundaries encountered in numerical simulations, including solid-surface, inflow and outflow, and far

  10. Chemical oxygen-iodine laser (COIL) beam quality predictions using 3D Navier-Stokes (MINT) and wave optics (OCELOT) codes

    Lampson, Alan I.; Plummer, David N.; Erkkila, John H.; Crowell, Peter G.; Helms, Charles A.

    1998-05-01

    This paper describes a series of analyses using the 3-d MINT Navier-Stokes and OCELOT wave optics codes to calculate beam quality in a COIL laser cavity. To make this analysis tractable, the problem was broken into two contributions to the medium quality; that associated with microscale disturbances primarily from the transverse iodine injectors, and that associated with the macroscale including boundary layers and shock-like effects. Results for both microscale and macroscale medium quality are presented for the baseline layer operating point in terms of single pass wavefront error. These results show that the microscale optical path difference effects are 1D in nature and of low spatial order. The COIL medium quality is shown to be dominated by macroscale effects; primarily pressure waves generated from flow/boundary layer interactions on the cavity shrouds.

  11. An efficient finite volume TVD scheme for steady-state solutions of the 3-D compressible Euler/Navier-Stokes equations

    The formulation and validation of an efficient spatially second-order accurate finite volume total variation diminishing (TVD) scheme in general curvilinear coordinates for the 3-D compressible Navier-Stokes equations in strong conservation law form is presented. Approximate factorization and flux splitting are not utilized; therefore the associated extra, unwanted numerical dissipation is avoided, especially in complex viscous problems. A general line relaxation procedure is used to accelerate the convergence rate for geometrically complex steady-state problems since it is completely vectorizable. The implicit operator is cast in a delta-form using a TVD preconditioning matrix. The explicit part is evaluated using the same finite-volume TVD procedures developed by the authors in previous publications. This procedure preserves the high-resolution TVD characteristics in the steady state even at high CFL numbers. Numerical results are presented which demonstrate the efficiency, accuracy, and convergence characteristics for single and multi-body inviscid and turbulent flows. 21 refs

  12. Application of the least-squares finite element method on the simulations of 3D incompressible free surface flows

    This paper presents the simulation of 3D free surface flows by the two-phase least-squares finite element method (LSFEM). It is believed that this is the first time the LSFEM be extended from a 2D model to a 3D one and applied to investigate the 3D free surface flow phenomena. The dynamic and kinematic boundary conditions of free surface are described in an Eulerian coordinate system. The governing 3D Navier-Stokes equations in association with the color function are solved by the element-by-element scheme. In this simulation, the volume of fluid (VOF) method and continuous stress force (CSF) models are applied for the determination of the interface between the two phases of liquid and gas. The free surface position at each time step is determined by the distribution of the color function. The formation of the 3D model is carefully examined; and the quantitative comparisons of the 3D numerical simulations with experimental measurements and previous 2D numerical results are verified in good agreement. For the partial dam-break flows, it is shown that the two-phase LSFEM can effectively simulate the 3D flows. The unsteady water surface profiles of dam-break flow moving over an obstacle and the liquid drop are also simulated in this study. A 3D two-phase LSFEM has been established and carefully justified by some benchmark free surface flows. The method will be useful for the actual application to the two-phase flows with two immiscible fluids, such as liquid-gas flow, and metallurgic flow.

  13. Electroosmotic flow through a microparallel channel with 3D wall roughness.

    Chang, Long; Jian, Yongjun; Buren, Mandula; Sun, Yanjun

    2016-02-01

    In this paper, a perturbation method is introduced to study the EOF in a microparallel channel with 3D wall roughness. The corrugations of the two walls are periodic sinusoidal waves of small amplitude in two directions either in phase or half-period out of phase. Based on linearized Poisson-Boltzmann equation, Laplace equation, and the Navier-Stokes equations, the perturbation solutions of velocity, electrical potential, and volume flow rate are obtained. By using numerical computation, the influences of the wall corrugations on the mean velocity are analyzed. The variations of electrical potential, velocity profile, mean velocity, and their dependences on the wave number α and β of wall corrugations in two directions, the nondimensional electrokinetic width K, and the zeta potential ratio between the lower wall and the upper wall ς are analyzed graphically. PMID:26333852

  14. Multilevel local refinement and multigrid methods for 3-D turbulent flow

    Liao, C.; Liu, C. [UCD, Denver, CO (United States); Sung, C.H.; Huang, T.T. [David Taylor Model Basin, Bethesda, MD (United States)

    1996-12-31

    A numerical approach based on multigrid, multilevel local refinement, and preconditioning methods for solving incompressible Reynolds-averaged Navier-Stokes equations is presented. 3-D turbulent flow around an underwater vehicle is computed. 3 multigrid levels and 2 local refinement grid levels are used. The global grid is 24 x 8 x 12. The first patch is 40 x 16 x 20 and the second patch is 72 x 32 x 36. 4th order artificial dissipation are used for numerical stability. The conservative artificial compressibility method are used for further improvement of convergence. To improve the accuracy of coarse/fine grid interface of local refinement, flux interpolation method for refined grid boundary is used. The numerical results are in good agreement with experimental data. The local refinement can improve the prediction accuracy significantly. The flux interpolation method for local refinement can keep conservation for a composite grid, therefore further modify the prediction accuracy.

  15. An explicit Runge-Kutta method for 3D turbulent incompressible flows

    Sung, Chao-Ho; Lin, Cheng-Wen; Hung, C. M.

    1988-01-01

    A computer code has been developed to solve for the steady-state solution of the 3D incompressible Reynolds-averaged Navier-Stokes equations. The approach is based on the cell-center, central-difference, finite-volume formulation and an explicit one-step, multistage Runge-Kutta time-stepping scheme. The Baldwin-Lomax turbulence model is used. Techniques to accelerate the rate of convergence to a steady-state solution include the preconditioned method, the local time stepping, and the implicit residual smoothing. Improvements in computational efficiency have been demonstrated in several areas. This numerical procedure has been used to simulate the turbulent horseshoe vortex flow around an airfoil/flat-plate juncture.

  16. Progress Toward Overset-Grid Moving Body Capability for USM3D Unstructured Flow Solver

    Pandyna, Mohagna J.; Frink, Neal T.; Noack, Ralph W.

    2005-01-01

    A static and dynamic Chimera overset-grid capability is added to an established NASA tetrahedral unstructured parallel Navier-Stokes flow solver, USM3D. Modifications to the solver primarily consist of a few strategic calls to the Donor interpolation Receptor Transaction library (DiRTlib) to facilitate communication of solution information between various grids. The assembly of multiple overlapping grids into a single-zone composite grid is performed by the Structured, Unstructured and Generalized Grid AssembleR (SUGGAR) code. Several test cases are presented to verify the implementation, assess overset-grid solution accuracy and convergence relative to single-grid solutions, and demonstrate the prescribed relative grid motion capability.

  17. Energy flow in passive and active 3D cochlear model

    Wang, Yanli; Steele, Charles [Department of Mechanical Engineering, Stanford University, Stanford, California (United States); Puria, Sunil [Department of Mechanical Engineering, Stanford University, Stanford, California (United States); Department of Otolaryngology, Head and Neck Surgery, Stanford University, Stanford, California (United States)

    2015-12-31

    Energy flow in the cochlea is an important characteristic of the cochlear traveling wave, and many investigators, such as von Békésy and Lighthill, have discussed this phenomenon. Particularly after the discovery of the motility of the outer hair cells (OHCs), the nature of the power gain of the cochlea has been a fundamental research question. In the present work, direct three-dimensional (3D) calculations of the power on cross sections of the cochlea and on the basilar membrane are performed based on a box model of the mouse cochlea. The distributions of the fluid pressure and fluid velocity in the scala vestibuli are presented. The power output from the OHCs and the power loss due to fluid viscous damping are calculated along the length of the cochlea. This work provides a basis for theoretical calculations of the power gain of the OHCs from mechanical considerations.

  18. Energy flow in passive and active 3D cochlear model

    Wang, Yanli; Puria, Sunil; Steele, Charles

    2015-12-01

    Energy flow in the cochlea is an important characteristic of the cochlear traveling wave, and many investigators, such as von Békésy and Lighthill, have discussed this phenomenon. Particularly after the discovery of the motility of the outer hair cells (OHCs), the nature of the power gain of the cochlea has been a fundamental research question. In the present work, direct three-dimensional (3D) calculations of the power on cross sections of the cochlea and on the basilar membrane are performed based on a box model of the mouse cochlea. The distributions of the fluid pressure and fluid velocity in the scala vestibuli are presented. The power output from the OHCs and the power loss due to fluid viscous damping are calculated along the length of the cochlea. This work provides a basis for theoretical calculations of the power gain of the OHCs from mechanical considerations.

  19. Energy flow in passive and active 3D cochlear model

    Energy flow in the cochlea is an important characteristic of the cochlear traveling wave, and many investigators, such as von Békésy and Lighthill, have discussed this phenomenon. Particularly after the discovery of the motility of the outer hair cells (OHCs), the nature of the power gain of the cochlea has been a fundamental research question. In the present work, direct three-dimensional (3D) calculations of the power on cross sections of the cochlea and on the basilar membrane are performed based on a box model of the mouse cochlea. The distributions of the fluid pressure and fluid velocity in the scala vestibuli are presented. The power output from the OHCs and the power loss due to fluid viscous damping are calculated along the length of the cochlea. This work provides a basis for theoretical calculations of the power gain of the OHCs from mechanical considerations

  20. Reynolds-stress model prediction of 3-D duct flows

    Gerolymos, G A

    2014-01-01

    The paper examines the impact of different modelling choices in second-moment closures by assessing model performance in predicting 3-D duct flows. The test-cases (developing flow in a square duct [Gessner F.B., Emery A.F.: {\\em ASME J. Fluids Eng.} {\\bf 103} (1981) 445--455], circular-to-rectangular transition-duct [Davis D.O., Gessner F.B.: {\\em AIAA J.} {\\bf 30} (1992) 367--375], and \\tsn{S}-duct with large separation [Wellborn S.R., Reichert B.A., Okiishi T.H.: {\\em J. Prop. Power} {\\bf 10} (1994) 668--675]) include progressively more complex strains. Comparison of experimental data with selected 7-equation models (6 Reynolds-stress-transport and 1 scale-determining equations), which differ in the closure of the velocity/pressure-gradient tensor $\\Pi_{ij}$, suggests that rapid redistribution controls separation and secondary-flow prediction, whereas, inclusion of pressure-diffusion modelling improves reattachment and relaxation behaviour.

  1. Stokes flow through a tube with bumpy wall

    Wang, C. Y.

    2006-07-01

    The Stokes flow through a tube with a bumpy wall is solved through a perturbation in the small amplitude of the three-dimensional bumps. The solution can be expressed in terms of modified Bessel functions. For given area or volume of a bump, there exists an optimum circumferential wave number and an optimum aspect ratio for which the flow rate is maximized.

  2. Navier-Stokes Flow in Cylindrical Elastic Tubes

    Taha Sochi

    2015-01-01

    Analytical expressions correlating the volumetric flow rate to the inlet and outlet pressures are derived for the time-independent flow of Newtonian fluids in cylindrically-shaped elastic tubes using a one-dimensional Navier-Stokes flow model with two pressure-area constitutive relations. These expressions for elastic tubes are the equivalent of Poiseuille and Poiseuille-type expressions for rigid tubes which were previously derived for the flow of Newtonian and non-Newtonian fluids under var...

  3. Flow of Navier-Stokes Fluids in Cylindrical Elastic Tubes

    Sochi, Taha

    2013-01-01

    Analytical expressions correlating the volumetric flow rate to the inlet and outlet pressures are derived for the time-independent flow of Newtonian fluids in cylindrically-shaped elastic tubes using a one-dimensional Navier-Stokes flow model with two pressure-area constitutive relations. These expressions for elastic tubes are the equivalent of Poiseuille and Poiseuille-type expressions for rigid tubes which were previously derived for the flow of Newtonian and non-Newtonian fluids under var...

  4. Large-eddy simulation of 3D turbulent flow past a complete marine hydrokinetic turbine

    Kang, S.; Sotiropoulos, F.

    2011-12-01

    A high-resolution computational framework was recently developed by Kang et al (Adv. Water Resour., submitted) for simulating three-dimensional (3D), turbulent flow past real-life, complete marine hydrokinetic (MHK) turbine configurations. In this model the complex turbine geometry is resolved by employing the curvilinear immersed boundary (CURVIB) method, which solves the 3D unsteady incompressible Navier-Stokes equations in generalized curvilinear domains with embedded arbitrarily complex, moving and/or stationary immersed boundaries (Ge and Sotiropoulos, 2007). Turbulence is simulated using the large-eddy simulation (LES) approach adapted in the context of the CURVIB method, with a wall model based on solving the simplified boundary layer equations used to reconstruct boundary conditions near all solid surfaces (Kang et al., 2011). The model can resolve the flow patterns generated by the rotor and all stationary components of the turbine as well as the interactions of the flow structures with the channel bed. We apply this model to carry out LES of the flow past the model-size hydrokinetic turbine deployed in the St. Anthony Falls Laboratory main channel. The mean velocities and second-order turbulence statistics measured in the downstream wake using acoustic Doppler velocimetry (ADV) are compared with the LES results. The comparisons show that the computed mean velocities and turbulent stresses are in good agreement with the measurements. The high-resolution LES data are used to explore physically important downstream flow characteristics such as the time-averaged wake structure, recovery of cross-sectionally averaged power potential, near-bed scour potential, etc. This work is supported by Verdant Power.

  5. Slip flow through a converging microchannel: experiments and 3D simulations

    An experimental and 3D numerical study of gaseous slip flow through a converging microchannel is presented in this paper. The measurements reported are with nitrogen gas flowing through the microchannel with convergence angles (4°, 8° and 12°), hydraulic diameters (118, 147 and 177 µm) and lengths (10, 20 and 30 mm). The measurements cover the entire slip flow regime and a part of the continuum and transition regimes (the Knudsen number is between 0.0004 and 0.14); the flow is laminar (the Reynolds number is between 0.5 and 1015). The static pressure drop is measured for various mass flow rates. The overall pressure drop increases with a decrease in the convergence angle and has a relatively large contribution of the viscous component. The numerical solutions of the Navier–Stokes equations with Maxwell’s slip boundary condition explore two different flow behaviors: uniform centerline velocity with linear pressure variation in the initial and the middle part of the microchannel and flow acceleration with nonlinear pressure variation in the last part of the microchannel. The centerline velocity and the wall shear stress increase with a decrease in the convergence angle. The concept of a characteristic length scale for a converging microchannel is also explored. The location of the characteristic length is a function of the Knudsen number and approaches the microchannel outlet with rarefaction. These results on gaseous slip flow through converging microchannels are observed to be considerably different than continuum flow. (paper)

  6. A free software for pore-scale modelling: solving Stokes equation for velocity fields and permeability values in 3D pore geometries

    Gerke, Kirill; Vasilyev, Roman; Khirevich, Siarhei; Karsanina, Marina; Collins, Daniel; Korost, Dmitry; Mallants, Dirk

    2015-04-01

    In this contribution we introduce a novel free software which solves the Stokes equation to obtain velocity fields for low Reynolds-number flows within externally generated 3D pore geometries. Provided with velocity fields, one can calculate permeability for known pressure gradient boundary conditions via Darcy's equation. Finite-difference schemes of 2nd and 4th order of accuracy are used together with an artificial compressibility method to iteratively converge to a steady-state solution of Stokes' equation. This numerical approach is much faster and less computationally demanding than the majority of open-source or commercial softwares employing other algorithms (finite elements/volumes, lattice Boltzmann, etc.) The software consists of two parts: 1) a pre and post-processing graphical interface, and 2) a solver. The latter is efficiently parallelized to use any number of available cores (the speedup on 16 threads was up to 10-12 depending on hardware). Due to parallelization and memory optimization our software can be used to obtain solutions for 300x300x300 voxels geometries on modern desktop PCs. The software was successfully verified by testing it against lattice Boltzmann simulations and analytical solutions. To illustrate the software's applicability for numerous problems in Earth Sciences, a number of case studies have been developed: 1) identifying the representative elementary volume for permeability determination within a sandstone sample, 2) derivation of permeability/hydraulic conductivity values for rock and soil samples and comparing those with experimentally obtained values, 3) revealing the influence of the amount of fine-textured material such as clay on filtration properties of sandy soil. This work was partially supported by RSF grant 14-17-00658 (pore-scale modelling) and RFBR grants 13-04-00409-a and 13-05-01176-a.

  7. A free software for pore-scale modelling: solving Stokes equation for velocity fields and permeability values in 3D pore geometries

    Gerke, Kirill

    2015-04-01

    In this contribution we introduce a novel free software which solves the Stokes equation to obtain velocity fields for low Reynolds-number flows within externally generated 3D pore geometries. Provided with velocity fields, one can calculate permeability for known pressure gradient boundary conditions via Darcy\\'s equation. Finite-difference schemes of 2nd and 4th order of accuracy are used together with an artificial compressibility method to iteratively converge to a steady-state solution of Stokes\\' equation. This numerical approach is much faster and less computationally demanding than the majority of open-source or commercial softwares employing other algorithms (finite elements/volumes, lattice Boltzmann, etc.) The software consists of two parts: 1) a pre and post-processing graphical interface, and 2) a solver. The latter is efficiently parallelized to use any number of available cores (the speedup on 16 threads was up to 10-12 depending on hardware). Due to parallelization and memory optimization our software can be used to obtain solutions for 300x300x300 voxels geometries on modern desktop PCs. The software was successfully verified by testing it against lattice Boltzmann simulations and analytical solutions. To illustrate the software\\'s applicability for numerous problems in Earth Sciences, a number of case studies have been developed: 1) identifying the representative elementary volume for permeability determination within a sandstone sample, 2) derivation of permeability/hydraulic conductivity values for rock and soil samples and comparing those with experimentally obtained values, 3) revealing the influence of the amount of fine-textured material such as clay on filtration properties of sandy soil. This work was partially supported by RSF grant 14-17-00658 (pore-scale modelling) and RFBR grants 13-04-00409-a and 13-05-01176-a.

  8. On 3D Lagrangian Navier-Stokes $\\alpha$ model with a Class of Vorticity-Slip Boundary conditions

    Xiao, Yuelong; Xin, Zhouping

    2012-01-01

    This paper concerns the 3-dimensional Lagrangian Navier-Stokes $\\alpha$ model and the limiting Navier-Stokes system on smooth bounded domains with a class of vorticity-slip boundary conditions and the Navier-slip boundary conditions. It establishes the spectrum properties and regularity estimates of the associated Stokes operators, the local well-posedness of the strong solution and global existence of weak solutions for initial boundary value problems for such systems. Furthermore, the vanis...

  9. Drop deformation in stokes flow through converging channels

    Wrobel, LC; Soares, D.; Das Bhaumik, CL

    2009-01-01

    This work presents an application of a direct BEM formulation for drop deformation and interaction in Stokes flows through converging channels. Parametric studies are conducted to investigate the effect, on drop deformation, of the channel’s convergence ratio, the drop-fluid viscosity ratio, the interfacial tension and the initial relative position of the drops.

  10. Ewald summation for the rotlet singularity of Stokes flow

    Klinteberg, Ludvig af

    2016-01-01

    Ewald summation is an efficient method for computing the periodic sums that appear when considering the Green's functions of Stokes flow together with periodic boundary conditions. We show how Ewald summation, and accompanying truncation error estimates, can be easily derived for the rotlet, by considering it as a superposition of electrostatic force calculations.

  11. Discretizations in isogeometric analysis of Navier-Stokes flow

    Nielsen, Peter Nørtoft; Gersborg, Allan Roulund; Gravesen, Jens;

    2011-01-01

    This paper deals with isogeometric analysis of 2-dimensional, steady state, incompressible Navier-Stokes flow subjected to Dirichlet boundary conditions. We present a detailed description of the numerical method used to solve the boundary value problem. Numerical inf-sup stability tests for the...

  12. On the stability threshold for the 3D Couette flow in Sobolev regularity

    Bedrossian, Jacob; Masmoudi, Nader

    2015-01-01

    We study Sobolev regularity disturbances to the periodic, plane Couette flow in the 3D incompressible Navier-Stokes equations at high Reynolds number $\\textbf{Re}$. Our goal is to estimate how the stability threshold scales in $\\textbf{Re}$: the largest the initial perturbation can be while still resulting in a solution that does not transition away from Couette flow. In this work we prove that initial data which satisfies $\\| u_{in} \\|_{H^\\sigma} \\leq \\delta\\textbf{Re}^{-3/2}$ for any $\\sigma > 9/2$ and some $\\delta = \\delta(\\sigma) > 0$ depending only on $\\sigma$, is global in time, remains within $O(\\textbf{Re}^{-1/2})$ of the Couette flow in $L^2$ for all time, and converges to the class of "2.5 dimensional" streamwise-independent solutions referred to as streaks for times $t \\gtrsim \\textbf{Re}^{1/3}$. Numerical experiments performed by Reddy et. al. with "rough" initial data estimated a threshold of $\\sim \\textbf{Re}^{-31/20}$, which shows very close agreement with our estimate.

  13. Shear-free boundary in Stokes flow

    Amaranath, T.; S. D. Nigam; Palaniappan, D.

    1996-01-01

    A theorem of Harper for axially symmetric flow past a sphere which is a stream surface, and is also shear-free, is extended to flow past a doubly-body ð”… consisting of two unequal, orthogonally intersecting spheres. Several illustrative examples are given. An analogue of Faxen's law for a double-body is observed.

  14. Numerical solution of compressible subsonic flows in 3D channel

    Pořízková, P.; Kozel, K.; Horáček, Jaromír

    Prague : Institute of Thermomechanics ASCR, v. v. i., 2013 - (Zolotarev, I.), s. 37-42 ISBN 978-80-87012-49-9. [Interaction and Feedbacks 2013 /20./. Prague (CZ), 26.11.2013-27.11.2013] R&D Projects: GA ČR(CZ) GAP101/11/0207 Institutional support: RVO:61388998 Keywords : finite volume method * aeroacoustics * Navier-Stokes equations Subject RIV: BI - Acoustics

  15. Numerical 3D Model of Viscous Turbulent Flow in One Stage Gas Turbine and Its Experimental Validation

    Yu.V. STARODUBTSEV; I.G. GOGOLEV; V.G. SOLODOV

    2005-01-01

    @@ The paper describes 3D numerical Reynolds Averaged Navier-Stokes (RANS) model and approximate sector approach for viscous turbulent flow through flow path of one stage axial supercharge gas turbine of marine diesel engine. Computational data are tested by comparison with experimental data. The back step flow path opening and tip clearance jet are taken into account.This approach could be applied for variety of turbine theory and design tasks: for offer optimal design in order to minimize kinetic energy stage losses; for solution of partial supply problem; for analysis of flow pattern in near extraction stages; for estimation of rotational frequency variable forces on blades; for sector vane adjustment (with thin leading edges mainly), for direct flow modeling in the turbine etc. The development of this work could be seen in the direction of unsteady stage model application.

  16. Numerical Calculations of 3-D High-Lift Flows and Comparison with Experiment

    Compton, William B, III

    2015-01-01

    Solutions were obtained with the Navier-Stokes CFD code TLNS3D to predict the flow about the NASA Trapezoidal Wing, a high-lift wing composed of three elements: the main-wing element, a deployed leading-edge slat, and a deployed trailing-edge flap. Turbulence was modeled by the Spalart-Allmaras one-equation turbulence model. One case with massive separation was repeated using Menter's two-equation SST (Menter's Shear Stress Transport) k-omega turbulence model in an attempt to improve the agreement with experiment. The investigation was conducted at a free stream Mach number of 0.2, and at angles of attack ranging from 10.004 degrees to 34.858 degrees. The Reynolds number based on the mean aerodynamic chord of the wing was 4.3 x 10 (sup 6). Compared to experiment, the numerical procedure predicted the surface pressures very well at angles of attack in the linear range of the lift. However, computed maximum lift was 5% low. Drag was mainly under predicted. The procedure correctly predicted several well-known trends and features of high-lift flows, such as off-body separation. The two turbulence models yielded significantly different solutions for the repeated case.

  17. Coupling nonlinear Stokes and Darcy flow using mortar finite elements

    Ervin, Vincent J.

    2011-11-01

    We study a system composed of a nonlinear Stokes flow in one subdomain coupled with a nonlinear porous medium flow in another subdomain. Special attention is paid to the mathematical consequence of the shear-dependent fluid viscosity for the Stokes flow and the velocity-dependent effective viscosity for the Darcy flow. Motivated by the physical setting, we consider the case where only flow rates are specified on the inflow and outflow boundaries in both subdomains. We recast the coupled Stokes-Darcy system as a reduced matching problem on the interface using a mortar space approach. We prove a number of properties of the nonlinear interface operator associated with the reduced problem, which directly yield the existence, uniqueness and regularity of a variational solution to the system. We further propose and analyze a numerical algorithm based on mortar finite elements for the interface problem and conforming finite elements for the subdomain problems. Optimal a priori error estimates are established for the interface and subdomain problems, and a number of compatibility conditions for the finite element spaces used are discussed. Numerical simulations are presented to illustrate the algorithm and to compare two treatments of the defective boundary conditions. © 2010 Published by Elsevier B.V. on behalf of IMACS.

  18. Numerical simulation of 3D flows in atmospheric boundary layer

    Šimonek, Jiří; Kozel, K.; Jaňour, Zbyněk

    Praha : Ústav termomechaniky AV ČR, v. v. i, 2012 - (Šimurda, D.; Kozel, K.), s. 93-96 ISBN 978-80-87012-40-6. [Topical Problems of Fluid Mechanics 2012 . Praha (CZ), 15.02. 2012 -17.02. 2012 ] R&D Projects: GA ČR GAP101/12/1271 Institutional research plan: CEZ:AV0Z20760514 Keywords : numerical solution * atmospheric boundary layer * Navier-Stokes equation s Subject RIV: DG - Athmosphere Sciences, Meteorology

  19. The Numerical Investigation on Vortex Flow Behavior Using FLOW-3D

    Jafar Chapokpour

    2012-01-01

    Full Text Available In this paper a numerical investigation is given for a Rankine type vortex flow inside the cylindrical vortex chamber using FLOW-3D. The FLOW-3D is a general purpose computational fluid dynamics (CFD package. The fluid motion is described with non-linear, transient, second-order differential equations. Additionally the free surface also exists in many simulations carried out with FLOW-3D because flow parameters and materials properties, such as density, velocity and pressure experience a discontinuity at it. After analysis of the vortex by mentioned details, the finding of time-averaged velocity components, turbulent components, turbulence dissipation, in the 2D briefed sections of chamber were depicted. It was found that there are different flow patterns like clockwise/anticlockwise vortices and some sink points combined with each other in different time intervals, decaying and generating along the time. Also the turbulence intensity and dissipations around the boundary conditions of chamber like central flushing discharge are higher than the flow body. It was also found that this CFD package was not able to simulate thoroughly the central air core of chamber after filling of chamber. This analysis is validated by comparison with previous experimental data that was measured in vortex settling basin.

  20. Effects of Presence, Copresence, and Flow on Learning Outcomes in 3D Learning Spaces

    Hassell, Martin D.; Goyal, Sandeep; Limayem, Moez; Boughzala, Imed

    2012-01-01

    The level of satisfaction and effectiveness of 3D virtual learning environments were examined. Additionally, 3D virtual learning environments were compared with face-to-face learning environments. Students that experienced higher levels of flow and presence also experienced more satisfaction but not necessarily more effectiveness with 3D virtual…

  1. Application of a recent solution of the Navier–Stokes equation to flow on the surface of a globe

    Highlights: • An exact solution of the 3D Navier–Stokes equation is simplified to 2D on the surface of a globe. • An initial velocity along the equator produces two symmetric flows towards the poles. • The velocity flows are arrived at without the use of numerical iterations speeding up the simulation. - Abstract: We reduce an exact solution of the 3D Navier–Stokes equation (Muriel, 2011) [1] to two dimensions to model flow on the surface of a globe, producing the following results: (a) an analytic discovery of the time evolution of two streams, one each above and below the equator, (b) analytic speed-up of modeling bypassing iterative numerical simulation

  2. Partial Averaged Navier-Stokes approach for cavitating flow

    Zhang, L.; Zhang, Y. N.

    2015-01-01

    Partial Averaged Navier Stokes (PANS) is a numerical approach developed for studying practical engineering problems (e.g. cavitating flow inside hydroturbines) with a resonance cost and accuracy. One of the advantages of PANS is that it is suitable for any filter width, leading a bridging method from traditional Reynolds Averaged Navier-Stokes (RANS) to direct numerical simulations by choosing appropriate parameters. Comparing with RANS, the PANS model will inherit many physical nature from parent RANS but further resolve more scales of motion in great details, leading to PANS superior to RANS. As an important step for PANS approach, one need to identify appropriate physical filter-width control parameters e.g. ratios of unresolved-to-total kinetic energy and dissipation. In present paper, recent studies of cavitating flow based on PANS approach are introduced with a focus on the influences of filter-width control parameters on the simulation results.

  3. Application of the parallel BDDC preconditioner to the Stokes flow

    Šístek, Jakub; Sousedík, Bedřich; Burda, P.; Mandel, J.; Novotný, J.

    2011-01-01

    Roč. 46, č. 1 (2011), s. 429-435. ISSN 0045-7930 R&D Projects: GA AV ČR IAA100760702; GA ČR GA106/08/0403 Institutional research plan: CEZ:AV0Z10190503; CEZ:AV0Z20760514 Keywords : BDDC * domain decomprosition * iterative substructuring * Stokes flow Subject RIV: BA - General Mathematics Impact factor: 1.810, year: 2011 http://www.sciencedirect.com/science/article/pii/S0045793011000053

  4. 3D pressure imaging of an aircraft propeller blade-tip flow by phase-locked stereoscopic PIV

    Ragni, D.; Oudheusden, B.W. van; Scarano, F. [Delft University of Technology, Faculty of Aerospace Engineering, Delft (Netherlands)

    2012-02-15

    The flow field at the tip region of a scaled DHC Beaver aircraft propeller, running at transonic speed, has been investigated by means of a multi-plane stereoscopic particle image velocimetry setup. Velocity fields, phase-locked with the blade rotational motion, are acquired across several planes perpendicular to the blade axis and merged to form a 3D measurement volume. Transonic conditions have been reached at the tip region, with a revolution frequency of 19,800 rpm and a relative free-stream Mach number of 0.73 at the tip. The pressure field and the surface pressure distribution are inferred from the 3D velocity data through integration of the momentum Navier-Stokes equation in differential form, allowing for the simultaneous flow visualization and the aerodynamic loads computation, with respect to a reference frame moving with the blade. The momentum and pressure data are further integrated by means of a contour-approach to yield the aerodynamic sectional force components as well as the blade torsional moment. A steady Reynolds averaged Navier-Stokes numerical simulation of the entire propeller model has been used for comparison to the measurement data. (orig.)

  5. Stereo Scene Flow for 3D Motion Analysis

    Wedel, Andreas

    2011-01-01

    This book presents methods for estimating optical flow and scene flow motion with high accuracy, focusing on the practical application of these methods in camera-based driver assistance systems. Clearly and logically structured, the book builds from basic themes to more advanced concepts, culminating in the development of a novel, accurate and robust optic flow method. Features: reviews the major advances in motion estimation and motion analysis, and the latest progress of dense optical flow algorithms; investigates the use of residual images for optical flow; examines methods for deriving mot

  6. Numerical method for calculation of 3D viscous turbomachine flow taking into account stator/rotor unsteady interaction

    Rusanov, A.V.; Yershov, S.V. [Institute of Mechanical Engineering Problems of National Academy of Sciences of Ukraine Kharkov (Ukraine)

    1997-12-31

    The numerical method is suggested for the calculation of the 3D periodically unsteady viscous cascade flow evoked by the aerodynamics interaction of blade rows. Such flow is described by the thin-layer Reynolds-averaged unsteady Navier-Stokes equations. The turbulent effects are simulated with the modified Baldwin-Lomax turbulence model. The problem statement allows to consider an unsteady flow through either a single turbo-machine stage or a multi stage turbomachine. The sliding mesh techniques and the time-space non-oscillatory square interpolation are used in axial spacings to calculate the flow in a computational domain that contains the reciprocally moving elements. The gasdynamical equations are integrated numerically with the implicit quasi-monotonous Godunov`s type ENO scheme of the second or third order of accuracy. The suggested numerical method is incorporated in the FlowER code developed by authors for calculations of the 3D viscous compressible flows through multi stage turbomachines. The numerical results are presented for unsteady turbine stage throughflows. The method suggested is shown to simulate qualitatively properly the main unsteady cascade effects in particular the periodically blade loadings, the propagation of stator wakes through rotor blade passage and the unsteady temperature flowfields for stages with cooled stator blades. (author) 21 refs.

  7. Stokes Flow with Slip and Kuwabara Boundary Conditions

    Sunil Datta; Satya Deo

    2002-08-01

    The forces experienced by randomly and homogeneously distributed parallel circular cylinder or spheres in uniform viscous flow are investigated with slip boundary condition under Stokes approximation using particle-in-cell model technique and the result compared with the no-slip case. The corresponding problem of streaming flow past spheroidal particles departing but little in shape from a sphere is also investigated. The explicit expression for the stream function is obtained to the first order in the small parameter characterizing the deformation. As a particular case of this we considered an oblate spheroid and evaluate the drag on it.

  8. Analytical Solution For Navier-Stokes Equations In Two Dimensions For Laminar Incompressible Flow

    Otarod, Saeed.; Otarod, Davar

    2006-01-01

    The Navier-Stokes equations describing laminar flow of an incompressible fluid will be solved. Different group of general solutions for Navier stokes equations governing Laminar incompressible fluids will be derived.

  9. On Approximation and Computation of Navier-Stokes Flow

    VARNHORN Werner; ZANGER Florian

    2013-01-01

    We present an approximation method for the non-stationary nonlinear incompressible Navier-Stokes equations in a cylindrical domain (0,T)×G,where G (C) IR3is a smoothly bounded domain.Our method is applicable to general three-dimensional flow without any symmetry restrictions and relies on existence,uniqueness and representation results from mathematical fluid dynamics.After a suitable time delay in the nonlinear convective term v·▽v we obtain globally (in time) uniquely solvable equations,which-by using semi-implicit time differences-can be transformed into a finite number of Stokes-type boundary value problems.For the latter a boundary element method based on a corresponding hydrodynamical potential theory is carried out.The method is reported in short outlines ranging from approximation theory up to numerical test calculations.

  10. Parallel Simulation of 3-D Turbulent Flow Through Hydraulic Machinery

    徐宇; 吴玉林

    2003-01-01

    Parallel calculational methods were used to analyze incompressible turbulent flow through hydraulic machinery. Two parallel methods were used to simulate the complex flow field. The space decomposition method divides the computational domain into several sub-ranges. Parallel discrete event simulation divides the whole task into several parts according to their functions. The simulation results were compared with the serial simulation results and particle image velocimetry (PIV) experimental results. The results give the distribution and configuration of the complex vortices and illustrate the effectiveness of the parallel algorithms for numerical simulation of turbulent flows.

  11. Implementation for blow up of tornado-type solutions for complex version of 3D Navier-Stokes system

    Arnold, M D

    2008-01-01

    We consider Cauchy problem for Fourier transformation of 3-dimensional Navier-Stokes system with zero external force. Using initial data purposed by Dong Li and Ya.G.Sinai we implement self-similar regime producing fast growing behavior of the energy of solution while time tends to critical value.

  12. A Navier-Stokes Approximation of the 3D Euler Equation with the Zero Flux on the Boundary

    Bellout, H.; Neustupa, Jiří

    2008-01-01

    Roč. 10, č. 4 (2008), s. 531-553. ISSN 1422-6928 R&D Projects: GA ČR GA201/05/0005 Institutional research plan: CEZ:AV0Z10190503 Keywords : Euler equation s * Navier - Stokes equation s Subject RIV: BA - General Mathematics Impact factor: 0.940, year: 2008

  13. Numerical experiments with 2D and 3D transonic flows

    Trefilík, J.; Huml, J.; Kozel, Karel; Příhoda, Jaromír

    Fukuoka: Kyushu University, 2012 - (Beneš, M.; Kimura, M.; Yazaki, S.), s. 1-14. (36). ISSN 1881-4042. [The Czech–Japanese Seminar in Applied Mathematics 2010. Praha (CZ), 30.08.2010-04.09.2010] R&D Projects: GA ČR(CZ) GAP101/10/1329 Institutional research plan: CEZ:AV0Z20760514 Keywords : inviscid flow * viscous flow * turbulence modelling * finite volume method Subject RIV: BK - Fluid Dynamics

  14. New 3-D flow interpolation method on moving ADCP data

    Tsubaki, R.; Kawahara, Y.; Muto, Y.; Fujita, I.

    2012-05-01

    A simple but accurate interpolation procedure for obtaining the three-dimensional distribution of three-component velocity data, from moving acoustic doppler current profiler (ADCP) observation data, is proposed. For understanding actual flow structure within a river with complex bathymetry, the three-dimensional mean velocity field provides a basic picture of the flow. For obtaining the three-dimensional distribution of three-component velocity data, in this work, anisotropic gridding was introduced in order to remove the random component of measured velocity data caused by the turbulence of the flow and measurement error. A continuity correction based on the pressure equation was used to reduce both random and systematic errors. The accuracy of the developed method was evaluated using three-dimensional flow simulation data from a detached-eddy simulation (DES). By using the procedure developed, the complex flow structure surrounding the spur dikes section in the Uji River was successfully visualized and explored. The proposed method shows superiorities in both accuracy and consistency for the interpolated velocity field, as compared to the kriging and inverse-distance weighted (IDW) methods.

  15. Laser direct writing 3D structures for microfluidic channels: flow meter and mixer

    Lin, Chih-Lang; Liu, Yi-Jui; Lin, Zheng-Da; Wu, Bo-Long; Lee, Yi-Hsiung; Shin, Chow-Shing; Baldeck, Patrice L.

    2015-03-01

    The 3D laser direct-writing technology is aimed at the modeling of arbitrary three-dimensional (3D) complex microstructures by scanning a laser-focusing point along predetermined trajectories. Through the perspective technique, the details of designed 3D structures can be properly fabricated in a microchannel. This study introduces a direct reading flow meter and a 3D passive mixer fabricated by laser direct writing for microfluidic applications. The flow meter consists of two rod-shaped springs, a pillar, an anchor, and a wedge-shaped indicator, installed inside a microfluidic channel. The indicator is deflected by the flowing fluid while restrained by the spring to establish an equilibrium indication according to the flow rate. The measurement is readily carried out by optical microscopy observation. The 3D passive Archimedes-screw-shaped mixer is designed to disturb the laminar flow 3D direction for enhancing the mixing efficiency. The simulation results indicate that the screw provides 3D disturbance of streamlines in the microchannel. The mixing demonstration for fluids flowing in the micrchannel approximately agrees with the simulation result. Thanks to the advantage of the laser direct writing technology, this study performs the ingenious applications of 3D structures for microchannels.

  16. CFD study of flow accelerated corrosion in 3D elbows

    Highlights: • Calculated the MTC effects under the FAC operating conditions of Indian power plant. • The validation of MTC results with the experimental data of NPP has been carried out. • The vortical flow behavior is captured in terms of vortex corelines. • The close proximity effect is analyzed. • These results will help to developing the targeted inspection plans of failures. - Abstract: The objective of this paper is to examine the last step of the mechanistic model of wall thinning degradation mechanism i.e., convective mass transfer in feeder pipes under different environments of nuclear power plants (NPP). In the present study, the flow and mass transfer of demineralised water in carbon steel pipes such as single and double elbow was simulated under Indian NPP feeder water system conditions. The numerical simulations of mass transfer results are compared with the wall thickness measurement data of feeder pipes of Indian and CANDU NPP. The eddy structures and their interactions with the wall and the formation of vortex corelines were examined to analyze the flow changes in double elbow pipe. These vortex corelines appeared at the downstream of the bends. The intensity of these vortex corelines has been calculated by plotting the helicity along the vortex coreline. Due to the formation of vortex corelines and resulting flow changes, the mass transfer coefficient (MTC) varies circumferentially. MTC is the most important parameter to predict the highly susceptible FAC locations. For the MTC analysis, the Chilton–Colburn analogy in terms of wall shear stress was used. From this analogy, the effecting behavior of flow and geometrical parameters such as Reynolds number (Re) and the close proximity of bends, respectively, on MTC are studied. The locations of maximum MTC are calculated for both the single elbow of 73° and 90° and the double elbow of 90° and are shown in terms of contours. The flow singularity exists at the elbows; specifically in the

  17. An Oseen Two-Level Stabilized Mixed Finite-Element Method for the 2D/3D Stationary Navier-Stokes Equations

    Peihua Qin; Dongxiu Xie; Xin Zhao; Aiwen Wang

    2012-01-01

    We investigate an Oseen two-level stabilized finite-element method based on the local pressure projection for the 2D/3D steady Navier-Stokes equations by the lowest order conforming finite-element pairs (i.e., ${Q}_{1}-{P}_{0}$ and ${P}_{1}-{P}_{0}$ ). Firstly, in contrast to other stabilized methods, they are parameter free, no calculation of higher-order derivatives and edge-based data structures, implemented at the element level with minimal cost. In addition, the Oseen two-level stabilize...

  18. Soliton metrics for two-loop renormalization group flow on 3D unimodular Lie groups

    Glickenstein, David; Wu, Liang

    2015-01-01

    The two-loop renormalization group flow is studied via the induced bracket flow on 3D unimodular Lie groups. A number of steady solitons are found. Some of these steady solitons come from maximally symmetric metrics that are steady, shrinking, or expanding solitons under Ricci flow, while others are not obviously related to Ricci flow solitons.

  19. Torsional oscillations of a sphere in a Stokes flow

    Box, F; Mullin, T

    2014-01-01

    The results of an experimental investigation of a sphere performing torsional oscillations in a Stokes flow are presented. A novel experimental set up was developed which enabled the motion of the sphere to be remotely controlled through application of an oscillatory magnetic field. The response of the sphere to the applied field was characterised in terms of the viscous, magnetic and gravitational torques acting on the sphere. A mathematical model of the system was developed and good agreement was found between experimental and theoretical results. The flow resulting from the motion of the sphere was measured and the fluid velocity was found to have an inverse square dependence on radial distance from the sphere. Agreement between measurements and the analytical solution for the fluid velocity indicates that the flow may be considered Stokesian.

  20. Simulation of 3D Flow in Turbine Blade Rows including the Effects of Coolant Ejection

    Jian-Jun LIU; Bai-Tao AN; Yun-Tao ZENG

    2008-01-01

    This paper describes the numerical simulation of three-dimensional viscous flows in air-cooled turbine blade rows with the effects of coolant ejection. A TVD Navier-Stokes flow solver incorporated with Baldwin-Lomax turbulence model and multi-grid convergence acceleration algorithm are used for the simulation. The influences of coolant ejection on the main flow are accounted by volumetric coolant source terms. Numerical results for a four-stage turbine are presented and discussed.

  1. Numerical simulation of 3D backward facing step flows at various Reynolds numbers

    Louda Petr

    2015-01-01

    Full Text Available The work deals with the numerical simulation of 3D turbulent flow over backward facing step in a narrow channel. The mathematical model is based on the RANS equations with an explicit algebraic Reynolds stress model (EARSM. The numerical method uses implicit finite volume upwind discretization. While the eddy viscosity models fail in predicting complex 3D flows, the EARSM model is shown to provide results which agree well with experimental PIV data. The reference experimental data provide the 3D flow field. The simulations are compared with experiment for 3 values of Reynolds number.

  2. Approximate analytic solutions to 3D unconfined groundwater flow within regional 2D models

    Luther, K.; Haitjema, H. M.

    2000-04-01

    We present methods for finding approximate analytic solutions to three-dimensional (3D) unconfined steady state groundwater flow near partially penetrating and horizontal wells, and for combining those solutions with regional two-dimensional (2D) models. The 3D solutions use distributed singularities (analytic elements) to enforce boundary conditions on the phreatic surface and seepage faces at vertical wells, and to maintain fixed-head boundary conditions, obtained from the 2D model, at the perimeter of the 3D model. The approximate 3D solutions are analytic (continuous and differentiable) everywhere, including on the phreatic surface itself. While continuity of flow is satisfied exactly in the infinite 3D flow domain, water balance errors can occur across the phreatic surface.

  3. Blow-up criterions of strong solutions to 3D compressible Navier-Stokes equations with vacuum

    Wen, Huanyao; Zhu, Changjiang

    2011-01-01

    In the paper, we establish a blow-up criterion in terms of the integrability of the density for strong solutions to the Cauchy problem of compressible isentropic Navier-Stokes equations in \\mathbb{R}^3 with vacuum, under the assumptions on the coefficients of viscosity: \\frac{29\\mu}{3}>\\lambda. This extends the corresponding results in [20, 36] where a blow-up criterion in terms of the upper bound of the density was obtained under the condition 7\\mu>\\lambda. As a byproduct, the restriction 7\\...

  4. Are the incompressible 3d Navier-Stokes equations locally ill-posed in the natural energy space?

    Jia, Hao; Šverák, Vladimír

    2013-01-01

    An important open problem in the theory of the Navier-Stokes equations is the uniqueness of the Leray-Hopf weak solutions with $L^2$ initial data. In this paper we give sufficient conditions for non-uniqueness in terms of spectral properties of a natural linear operator associated to scale-invariant solutions recently constructed in \\cite{JiaSverak}. If the spectral conditions are satisfied, non-uniqueness and ill-posedness can appear for quite benign compactly supported data, just at the bor...

  5. A geometric measure-type regularity criterion for solutions to the 3D Navier–Stokes equations

    A local anisotropic geometric measure-type condition on the super-level sets of solutions to the 3D NSE preventing the formation of a finite-time singularity is presented; essentially, local one-dimensional sparseness of the regions of intense fluid activity in a very weak sense. (paper)

  6. A front-tracking/front-capturing method for the simulation of 3D multi-fluid flows with free surfaces

    A method for simulating incompressible, imiscible, unsteady, Newtonian, multi-fluid flows with free surfaces is described. A sharp interface separates fluids of different density and viscosity. Surface and interfacial tensions are also considered and the required curvature is geometrically approximated at the fronts by a least squares quadratic fitting. To remove small undulations at the fronts, a mass-conserving filter is employed. The numerical method employed to solve the Navier-Stokes equations is based on the GENSMAC-3D front-tracking method. The velocity field is computed using a finite-difference scheme on an Eulerian grid. The free-surface and the interfaces are represented by an unstructured Lagrangian grid moving through an Eulerian grid. The method was validated by comparing the numerical results with analytical results for a number of simple problems. Complex numerical simulations show the capability and emphasize the robustness of this new method

  7. 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

  8. The application of a 3D PTV algorithm to a mixed convection flow

    Kieft, R.N.; Schreel, K.R.A.M.; Van der Plas, G.A.J.; Rindt, C.C.M. [Energy Technology Division, Department of Mechanical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands)

    2002-10-01

    A 3D particle-tracking velocimetry (PTV) algorithm is applied to the wake flow behind a heated cylinder. The method is tested in advance with respect to its accuracy and performance. In the accuracy tests, its capability to locate particles in 3D space is tested. It appears that the algorithm can determine the particle position with an accuracy of less than 0.5 camera pixels, equivalent to 0.3 mm in the present test situation. The performance tests show that for particles located in a 2D plane, the algorithm can track the particles with a vector yield reaching 100%, which means that a velocity vector can be determined for almost all particles detected. The calculated velocity vectors for this situation have a standard deviation of less than 1%. The performance is also tested on a mixed convection flow behind a heated cylinder in which the 2D flow transits into a 3D flow. As there is no exact solution of such a flow available, the 3D PTV results are compared with visualisation results. The results show that the 3D PTV method can capture the main features of the 3D transition of the 2D vortex street. (orig.)

  9. Assessing cerebrospinal fluid flow connectivity using 3D gradient echo phase contrast velocity encoded MRI

    The aim of this study is to investigate the feasibility of using three-directional velocity encoded 3D gradient echo (GE) phase contrast (PC) imaging to assess cerebrospinal fluid (CSF) flow connectivity in the human brain. Five healthy volunteers were scanned using low velocity sensitivity (Venc = 0.04–0.05 m s−1). Flow–time curves were compared to standard 2D PC scans. The 3D data were used to reconstruct in vivo CSF flow volumes based on time-averaged phase-difference information, and the patency of the CSF flow pathways was assessed using nearest-neighbour connectivity. A pulsatile flow phantom was used to gauge the measurement accuracy of the CSF flow volumes at low flow velocities. Flow connectivity from the lateral ventricles down to the cisterna magna was successfully demonstrated in all volunteers. The phantom tests showed a good distinction between the flow cavities and the background noise. 3D PC imaging results in CSF flow waveforms with similar pulsatility but underestimated peak velocities compared to 2D PC data. 3D time-resolved velocity encoded GE imaging has successfully been applied to assess CSF flow connectivity in normal subjects

  10. Navier-Stokes Computations With One-Equation Turbulence Model for Flows Along Concave Wall Surfaces

    Wang, Chi R.

    2005-01-01

    This report presents the use of a time-marching three-dimensional compressible Navier-Stokes equation numerical solver with a one-equation turbulence model to simulate the flow fields developed along concave wall surfaces without and with a downstream extension flat wall surface. The 3-D Navier- Stokes numerical solver came from the NASA Glenn-HT code. The one-equation turbulence model was derived from the Spalart and Allmaras model. The computational approach was first calibrated with the computations of the velocity and Reynolds shear stress profiles of a steady flat plate boundary layer flow. The computational approach was then used to simulate developing boundary layer flows along concave wall surfaces without and with a downstream extension wall. The author investigated the computational results of surface friction factors, near surface velocity components, near wall temperatures, and a turbulent shear stress component in terms of turbulence modeling, computational mesh configurations, inlet turbulence level, and time iteration step. The computational results were compared with existing measurements of skin friction factors, velocity components, and shear stresses of the developing boundary layer flows. With a fine computational mesh and a one-equation model, the computational approach could predict accurately the skin friction factors, near surface velocity and temperature, and shear stress within the flows. The computed velocity components and shear stresses also showed the vortices effect on the velocity variations over a concave wall. The computed eddy viscosities at the near wall locations were also compared with the results from a two equation turbulence modeling technique. The inlet turbulence length scale was found to have little effect on the eddy viscosities at locations near the concave wall surface. The eddy viscosities, from the one-equation and two-equation modeling, were comparable at most stream-wise stations. The present one

  11. Propulsion of micro-structures in Oscillatory Stokes Flow

    Jo, Ikhee; Huang, Yangyang; Zimmerman, Walter; Kanso, Eva

    2015-11-01

    Drug delivery often necessitates specific site-targeting within the human body. The use of micro and/or nano devices swimming through the bloodstream provides an attractive mechanism for targeted drug targeting, however the design and practical implementation of such devices remain very challenging. Inspired by flapping wings, we construct a two-dimensional wedge-like device, consisting of two links connected by a linear torsional spring and released in an oscillatory Stokes flow. We vary the stiffness and rest angle of the linear spring and the oscillation amplitude and frequency of the background flow to explore the behavior of the device. We find that the device achieves a net displacement, or propulsion, in oscillatory flows even when no elastic energy is stored initially, thus breaking Purcell's scallop's theorem. More importantly, the vehicle tends to align with the background flow under perturbations. We conclude by commenting on how to control the parameters of the device and the fluid to achieve desired behavior of the device. These findings may have significant implications on the design of micro devices in viscous fluids.

  12. The computation of steady 3-D separated flows over aerodynamic bodies at incidence and yaw

    Pulliam, T. H.; Pan, D.

    1986-01-01

    This paper describes the implementation of a general purpose 3-D NS code and its application to simulated 3-D separated vortical flows over aerodynamic bodies. The thin-layer Reynolds-averaged NS equations are solved by an implicit approximate factorization scheme. The pencil data structure enables the code to run on very fine grids using only limited incore memories. Solutions of a low subsonic flow over an inclined ellipsoid are compared with experimental data to validate the code. Transonic flows over a yawed elliptical wing at incidence are computed and separations occurred at different yaw angles are discussed.

  13. 3D-printed devices for continuous-flow organic chemistry

    Vincenza Dragone

    2013-05-01

    Full Text Available We present a study in which the versatility of 3D-printing is combined with the processing advantages of flow chemistry for the synthesis of organic compounds. Robust and inexpensive 3D-printed reactionware devices are easily connected using standard fittings resulting in complex, custom-made flow systems, including multiple reactors in a series with in-line, real-time analysis using an ATR-IR flow cell. As a proof of concept, we utilized two types of organic reactions, imine syntheses and imine reductions, to show how different reactor configurations and substrates give different products.

  14. 3D-printed devices for continuous-flow organic chemistry

    Vincenza Dragone; Victor Sans; Rosnes, Mali H; Kitson, Philip J.; Leroy Cronin

    2013-01-01

    We present a study in which the versatility of 3D-printing is combined with the processing advantages of flow chemistry for the synthesis of organic compounds. Robust and inexpensive 3D-printed reactionware devices are easily connected using standard fittings resulting in complex, custom-made flow systems, including multiple reactors in a series with in-line, real-time analysis using an ATR-IR flow cell. As a proof of concept, we utilized two types of organic reactions, imine syntheses and im...

  15. Dual local and non-local cascades in 3D turbulent Beltrami flows

    Herbert, E; Daviaud, F; Dubrulle, B.; Nazarenko, S.; A. Naso

    2012-01-01

    We discuss the possibility of dual local and non-local cascades in a 3D turbulent Beltrami flow, with inverse energy cascade and direct helicity cascade, by analogy with 2D turbulence. We discuss the corresponding energy spectrum in both local and non-local case. Comparison with a high Reynolds number turbulent von Karman flow is provided and discussed.

  16. The performance & flow visualization studies of three-dimensional (3-D) wind turbine blade models

    Sutrisno, Prajitno, Purnomo, W., Setyawan B.

    2016-06-01

    Recently, studies on the design of 3-D wind turbine blades have a less attention even though 3-D blade products are widely sold. In contrary, advanced studies in 3-D helicopter blade tip have been studied rigorously. Studies in wind turbine blade modeling are mostly assumed that blade spanwise sections behave as independent two-dimensional airfoils, implying that there is no exchange of momentum in the spanwise direction. Moreover, flow visualization experiments are infrequently conducted. Therefore, a modeling study of wind turbine blade with visualization experiment is needed to be improved to obtain a better understanding. The purpose of this study is to investigate the performance of 3-D wind turbine blade models with backward-forward swept and verify the flow patterns using flow visualization. In this research, the blade models are constructed based on the twist and chord distributions following Schmitz's formula. Forward and backward swept are added to the rotating blades. Based on this, the additional swept would enhance or diminish outward flow disturbance or stall development propagation on the spanwise blade surfaces to give better blade design. Some combinations, i. e., b lades with backward swept, provide a better 3-D favorable rotational force of the rotor system. The performance of the 3-D wind turbine system model is measured by a torque meter, employing Prony's braking system. Furthermore, the 3-D flow patterns around the rotating blade models are investigated by applying "tuft-visualization technique", to study the appearance of laminar, separated, and boundary layer flow patterns surrounding the 3-dimentional blade system.

  17. Stokes Flow over Composite Sphere: Liquid Core with Permeable Shell

    bharat raj jaiswal

    2015-01-01

    Full Text Available This paper presents an analytical study of an infinite expanse of uniform flow of steady axisymmetric Stokes flow of an incompressible Newtonian fluid around the spherical drop of Reiner-Rivlin liquid coated with the permeable layer with the assumption that the liquid located outside the capsule penetrates into the permeable layer, but it is not mingled with the liquid located in the internal concave of capsule. The flow inside the permeable layer is described by the Brinkman equation. The viscosity of the permeable medium is assumed to be same as pure liquid. The stream function solution for the outer flow field is obtained in terms of modified Bessel functions and Gegenbauer functions, and for the inner flow field, the stream function solution is obtained by expanding the stream function in terms of S. The flow fields are determined explicitly by matching the boundary conditions at the pure liquid-porous interface, porous-Reiner-Rivlin liquid interface, and uniform velocity at infinity. The drag force experienced by the capsule is evaluated, and its variation with regard to permeability parameter a, dimensionless parameter S, ratio of viscosities l2, and thickness of permeable layer d is studied and graphs plotted against these parameters. Several cases of interest are deduced from the present analysis. It is observed that the cross-viscosity increases the drag force, whereas the thickness d decreases the drag on capsule. It is also observed that the drag force is increasing or decreasing function of permeability parameter for l2 < 1.

  18. Completion of PCFLOW3D Model for Simulation of Flow and Dispersion of Pollutants

    Kovšca, Jasna

    2007-01-01

    An upgrade of the three-dimensional baroclinic mathematical model PCFLOW3D with a new turbulence model Smagorinsky-vertical is presented. Several test cases were made to compare this new turbulence model with other turbulence models already built in the PCFLOW3D model. Additional verifications of the test results were performed using the commercial software CORMIX of which main purpose is to simulate the near field areas of pollution inflows. CORMIX is restricted to steady flow...

  19. Ultrarapid Detection of Pathogenic Bacteria Using a 3D Immunomagnetic Flow Assay

    Lee, Wonjae; Kwon, Donghoon; Chung, Boram; Jung, Gyoo Yeol; Au, Anthony; Folch, Albert; Jeon, Sangmin

    2014-01-01

    We developed a novel 3D immunomagnetic flow assay for the rapid detection of pathogenic bacteria in a large-volume food sample. Antibody-functionalized magnetic nanoparticle clusters (AbMNCs) were magnetically immobilized on the surfaces of a 3D-printed cylindrical microchannel. The injection of a Salmonella-spiked sample solution into the microchannel produced instant binding between the AbMNCs and the Salmonella bacteria due to their efficient collisions. Nearly perfect capture of the AbMNC...

  20. Quantification of blood perfusion using 3D power Doppler: an in-vitro flow phantom study

    Raine-Fenning, N J [School of Human Development, Queens Medical Centre, University of Nottingham, Nottingham (United Kingdom); Ramnarine, K V [Department of Medical Physics, University Hospitals of Leicester NHS Trust, Leicester (United Kingdom); Nordin, N M [School of Human Development, Queens Medical Centre, University of Nottingham, Nottingham (United Kingdom); Campbell, B K [School of Human Development, Queens Medical Centre, University of Nottingham, Nottingham (United Kingdom)

    2004-01-01

    Three-dimensional (3D) power Doppler data is increasingly used to assess and quantify blood flow and tissue perfusion. The objective of this study was to assess the validity of common 3D power Doppler 'vascularity' indices by quantification in well characterised in-vitro flow models. A computer driven gear pump was used to circulate a steady flow of a blood mimicking fluid through various well characterised flow phantoms to investigate the effect of the number of flow channels, flow rate, depth dependent tissue attenuation, blood mimic scatter particle concentration and ultrasound settings. 3D Power Doppler data were acquired with a Voluson 530D scanner and 7.5 MHz transvaginal transducer (GE Kretz). Virtual Organ Computer-aided Analysis software (VOCAL) was used to quantify the vascularisation index (VI), flow index (FI) and vascularisation-flow index (VFI). The vascular indices were affected by many factors, some intuitive and some with more complex or unexpected relationships (e.g. VI increased linearly with an increase in flow rate, blood mimic scatter particle concentration and number of flow channels, and had a complex dependence on pulse repetition frequency). Use of standardised settings and appropriate calibration are required in any attempt at relating 'vascularity indices' with flow.

  1. A 3D model of a reverse vortex flow gliding arc reactor

    Trenchev, G.; Kolev, St.; Bogaerts, A.

    2016-06-01

    In this computational study, a gliding arc plasma reactor with a reverse-vortex flow stabilization is modelled for the first time by a fluid plasma description. The plasma reactor operates with argon gas at atmospheric pressure. The gas flow is simulated using the k-ε Reynolds-averaged Navier–Stokes turbulent model. A quasi-neutral fluid plasma model is used for computing the plasma properties. The plasma arc movement in the reactor is observed, and the results for the gas flow, electrical characteristics, plasma density, electron temperature, and gas temperature are analyzed.

  2. Numerical simulation of complex 3D compressible viscous flows through rotating blade passage

    Despotović M.; Babić Milun; Milovanović D.; Šušteršič Vanja

    2003-01-01

    This paper describes a three-dimensional compressible Navier-Stokes code, which has been developed for analysis of turbocompressor blade rows and other internal flows. Despite numerous numerical techniques and statement that Computational Fluid Dynamics has reached state of the art, issues related to successful simulations represent valuable database of how particular tech­nique behave for a specifie problem. This paper deals with rapid numerical method accurate enough to be used as a design ...

  3. Numerical prediction of 3-D periodic flow unsteadiness in a centrifugal pump under part-load condition

    裴吉; 袁寿其; 李晓俊; 袁建平

    2014-01-01

    Numerical simulation and 3-D periodic flow unsteadiness analysis for a centrifugal pump with volute are carried out in whole flow passage, including the impeller with twisted blades, the volute and the side chamber channels under a part-load condition. The pressure fluctuation intensity coefficient (PFIC) based on the standard deviation method, the time-averaged velocity unsteadi-ness intensity coefficient (VUIC) and the time-averaged turbulence intensity coefficient (TIC) are defined by averaging the results at each grid node for an entire impeller revolution period. Therefore, the strength distributions of the periodic flow unsteadiness based on the unsteady Reynolds-averaged Navier-Stokes (URANS) equations can be analyzed directly and in detail. It is shown that under the des.0.6Q condition, the pressure fluctuation intensity is larger near the blade pressure side than near the suction side, and a high fluctuation intensity can be observed at the beginning section of the spiral of the volute. The flow velocity unsteadiness intensity is larger near the blade suction side than near the pressure side. A strong turbulence intensity can be found near the blade suction side, the impeller shroud side as well as in the side chamber. The leakage flow has a significant effect on the inflow of the impeller, and can increase both the flow velocity unsteadiness intensity and the turbulence intensity near the wall. The accumulative flow unstea-diness results of an impeller revolution can be an important aspect to be considered in the centrifugal pump optimum design for ob-taining a more stable inner flow of the pump and reducing the flow-induced vibration and noise in certain components.

  4. Effects of Texture Component Orientation on Orientation Flow Visibility for 3-D Shape Perception

    Michelle L Fowler; Andrea Li

    2013-01-01

    In images of textured 3-D surfaces, orientation flows created by the texture components parallel to the surface slant play a critical role in conveying the surface slant and shape. This study examines the visibility of these orientation flows in complex patterns. Specifically, we examine the effect of orientation of neighboring texture components on orientation flow visibility. Complex plaids consisting of gratings equally spaced in orientation were mapped onto planar and curved surfaces. The...

  5. High fidelity digital inline holographic method for 3D flow measurements.

    Toloui, Mostafa; Hong, Jiarong

    2015-10-19

    Among all the 3D optical flow diagnostic techniques, digital inline holographic particle tracking velocimetry (DIH-PTV) provides the highest spatial resolution with low cost, simple and compact optical setups. Despite these advantages, DIH-PTV suffers from major limitations including poor longitudinal resolution, human intervention (i.e. requirement for manually determined tuning parameters during tracer field reconstruction and extraction), limited tracer concentration, and expensive computations. These limitations prevent this technique from being widely used for high resolution 3D flow measurements. In this study, we present a novel holographic particle extraction method with the goal of overcoming all the major limitations of DIH-PTV. The proposed method consists of multiple steps involving 3D deconvolution, automatic signal-to-noise ratio enhancement and thresholding, and inverse iterative particle extraction. The entire method is implemented using GPU-based algorithm to increase the computational speed significantly. Validated with synthetic particle holograms, the proposed method can achieve particle extraction rate above 95% with fake particles less than 3% and maximum position error below 1.6 particle diameter for holograms with particle concentration above 3000 particles/mm3. The applicability of the proposed method for DIH-PTV has been further validated using the experiment of laminar flow in a microchannel and the synthetic tracer flow fields generated using a DNS turbulent channel flow database. Such improvements will substantially enhance the implementation of DIH-PTV for 3D flow measurements and enable the potential commercialization of this technique. PMID:26480377

  6. A moving mesh algorithm for 3-D regional groundwater flow with water table and seepage face

    Knupp, P.

    A numerical algorithm is described for solving the free-surface groundwater flow equations in 3-D large-scale unconfined aquifers with strongly heterogeneous conductivity and surface recharge. The algorithm uses a moving mesh to track the water-table as it evolves according to kinematic and seepage face boundary conditions. Both steady-state and transient algorithms are implemented in the SECO-Flow 3-D code and demonstrated on stratigraphy based on the Delaware Basin of south-eastern New Mexico.

  7. 3-D NUMERICAL SIMULATION OF FLOW THROUGH AN ORIFICE SPILL-WAY TUNNEL

    2002-01-01

    A Large Eddy Simulation (LES) approachbased on the weakly compressible hydrodynamic equation with a single-plase fluid model for the cavitation flow has been de-veloped and employed in simulating 3-D unsteady viscous flowthrough an orifice type spillwy tunnel. The finite volume ap-proach in space and the predictor-corrector method in timehave been used to the numerical discretization, and the "Lawof wall" is applied at the solid boundary. The velocity, pres-sure fields and the cavitation phenomenon are obtained, thecomputational results show that 3-D LES approach can givemore realistic flow field prediction of the orifice type spillwaytunnel.

  8. A study of flow mixing in a PWR vessel in asymmetric cooldown faults using the FLOW3D code

    The Harwell computational fluid dynamics code, FLOW3D has been used to simulate a flow mixing test in the Oconee-1 reactor. The object was to test the ability of FLOW3D to describe thermal mixing in a PWR pressure vessel for the conditions of an over-cooling fault. The code produced reasonable estimates of the thermal diffusion observed in the Oconee test, with a tendency to underpredict mixing. However, the test exhibited gross swirl and asymmetric mixing which was not predicted by FLOW3D. Sensitivity studies to investigate the effects of downcomer ovality, inlet flow vorticity and flow imbalance between loops, have not revealed the source of the observed asymmetries

  9. Thermal structure and basal sliding parametrisation at Pine Island Glacier – a 3-D full-Stokes model study

    N. Wilkens

    2014-09-01

    Full Text Available Pine Island Glacier is one of the fastest changing glaciers in the Antarctic Ice Sheet and therefore in scientific focus. The glacier holds enough ice to raise global sea level significantly (∼0.5 m, when fully melted. The question addressed by numerous modelling studies of the glacier focuses on whether the observed changes are a start for an uncontrolled and accelerating retreat. The movement of the glacier is, in the fast flowing areas, dominated by basal motion. In modelling studies the parametrisation of the basal motion is therefore crucial. Inversion methods are commonly applied to reproduce the complex surface flow structure at Pine Island Glacier, which use information of the observed surface velocity field, to constrain basal sliding. We introduce two different approaches of combining a physical parameter, the basal roughness, with basal sliding parametrisations. This way basal sliding is connected again to its original formulation. We show that the basal roughness is an important and helpful parameter to consider and that many features of the flow structure could be reproduced with these approaches.

  10. Effects of texture component orientation on orientation flow visibility for 3-D shape perception.

    Michelle L Fowler

    Full Text Available In images of textured 3-D surfaces, orientation flows created by the texture components parallel to the surface slant play a critical role in conveying the surface slant and shape. This study examines the visibility of these orientation flows in complex patterns. Specifically, we examine the effect of orientation of neighboring texture components on orientation flow visibility. Complex plaids consisting of gratings equally spaced in orientation were mapped onto planar and curved surfaces. The visibility of the component that creates the orientation flows was quantified by measuring its contrast threshold (CT while varying the combination of neighboring components present in the pattern. CTs were consistently lowest only when components closest in orientation to that of the orientation flows were subtracted from the pattern. This finding suggests that a previously reported frequency-selective cross-orientation suppression mechanism involved with the perception of 3-D shape from texture is affected by proximity in orientation of concurrent texture components.

  11. 3-D Vector Flow Using a Row-Column Addressed CMUT Array

    Holbek, Simon; Christiansen, Thomas Lehrmann; Engholm, Mathias;

    2016-01-01

    cells, and second, elements areaccessed by row and/or column indices. The 62+62 2-D row-column addressed prototype CMUT probe was usedfor vector flow estimation by transmitting focused ultrasound into a flow-rig with a fully developed parabolicflow. The beam-to-flow angle was 90◦. The received data was...... characteristic parabolic velocity profile was estimated with a peak velocity of 0.48m/s ± 0.02 m/s in reference to the expected 0.54 m/s. The results presented are the first 3-D vector flow estimates obtained with a row-column CMUT probe, which demonstrates that the CMUT technology is feasiblefor 3-D flow...

  12. One-layer microfluidic device for hydrodynamic 3D self-flow-focusing operating in low flow speed

    Daghighi, Yasaman; Gnyawali, Vaskar; Strohm, Eric M.; Tsai, Scott S. H.; Kolios, Michael C.

    2016-03-01

    Hydrodynamic 3D flow-focusing techniques in microfluidics are categorized as (a) sheathless techniques which require high flow rates and long channels, resulting in high operating cost and high flow rates which are inappropriate for applications with flow rate limitations, and (b) sheath-flow based techniques which usually require excessive sheath flow rate to achieve hydrodynamic 3D flow-focusing. Many devices based on these principles use complicated fabrication methods to create multi-layer microchannels. We have developed a sheath-flow based microfluidic device that is capable of hydrodynamic 3D self-flow-focusing. In this device the main flow (black ink) in a low speed, and a sheath flow, enter through two inlets and enter a 180 degree curved channel (300 × 300 μm cross-section). Main flow migrates outwards into the sheath-flow due to centrifugal effects and consequently, vertical focusing is achieved at the end of the curved channel. Then, two other sheath flows horizontally confine the main flow to achieve horizontal focusing. Thus, the core flow is three-dimensionally focused at the center of the channel at the downstream. Using centrifugal force for 3D flow-focusing in a single-layer fabricated microchannel has been previously investigated by few groups. However, their demonstrated designs required high flow speed (>1 m/s) which is not suitable for many applications that live biomedical specie are involved. Here, we introduce a new design which is operational in low flow speed (microfluidic device can be used in detecting, counting and isolating cells in many biomedical applications.

  13. New P3D Hydraulic Fracturing Model Based on the Radial Flow

    鲁连军; 孙逢春; 肖海华; 安申法

    2004-01-01

    Pseudo three-dimension (P3D) hydraulic fracturing models often overpredict the fracture height for a poorly contained fracture. To solve this problem, a new method is presented in shaping the P3D fracture geometry on the basis of the fundamental theory and the original 1D fluid flow is replaced with a more representatively radial flow. The distribution of the fluid in the modified fluid field is analyzed and a sound explanation to the problem is given. Due to the consideration of the fluid flow in the vertical direction, the modified model can predict the fracture height much better. To validate the rationality of the radial fluid flow assumption, the distribution of the fluid in the modified fluid field is simulated with the plane potential flow by using finite element method. And the results agree effectively with those from the assumption. Through comparing with the full 3D model, the results show that this new P3D model can be used to aid the fracturing design and predict the fracture height under poorly contained situation.

  14. Modeling blood flow circulation in intracranial arterial networks: a comparative 3D/1D simulation study.

    Grinberg, L; Cheever, E; Anor, T; Madsen, J R; Karniadakis, G E

    2011-01-01

    We compare results from numerical simulations of pulsatile blood flow in two patient-specific intracranial arterial networks using one-dimensional (1D) and three-dimensional (3D) models. Specifically, we focus on the pressure and flowrate distribution at different segments of the network computed by the two models. Results obtained with 1D and 3D models with rigid walls show good agreement in massflow distribution at tens of arterial junctions and also in pressure drop along the arteries. The 3D simulations with the rigid walls predict higher amplitude of the flowrate and pressure temporal oscillations than the 1D simulations with compliant walls at various segments even for small time-variations in the arterial cross-sectional areas. Sensitivity of the flow and pressure with respect to variation in the elasticity parameters is investigated with the 1D model. PMID:20661645

  15. 3D Simulation of Velocity Profile of Turbulent Flow in Open Channel with Complex Geometry

    Kamel, Benoumessad; Ilhem, Kriba; Ali, Fourar; Abdelbaki, Djebaili

    Simulation of open channel flow or river flow presents unique challenge to numerical simulators, which is widely used in the applications of computational fluid dynamics. The prediction is extremely difficult because the flow in open channel is usually transient and turbulent, the geometry is irregular and curved, and the free-surface elevation is varying with time. The results from a 3D non-linear k- ɛ turbulence model are presented to investigate the flow structure, the velocity distribution and mass transport process in a meandering compound open channel and a straight open channel. The 3D numerical model for calculating flow is set up in cylinder coordinates in order to calculate the complex boundary channel. The finite volume method is used to disperse the governing equations and the SIMPLE algorithm is applied to acquire the coupling of velocity and pressure. The non-linear k- ɛ turbulent model has good useful value because of taking into account the anisotropy and not increasing the computational time. The main contributions of this study are developing a numerical method that can be applied to predict the flow in river bends with various bend curvatures and different width-depth ratios. This study demonstrates that the 3D non-linear k- ɛ turbulence model can be used for analyzing flow structures, the velocity distribution and pollutant transport in the complex boundary open channel, this model is applicable for real river and wetland problem.

  16. Implementation and testing of the CFDS-FLOW3D code

    FLOW3D is a multi-purpose, transient fluid dynamics and heat transfer code developed by Computational Fluid Dynamics Services (CFDS), a branch of AEA Technology, based at Harwell. The code is supplied with a SUN-based operating environment consisting of an interactive grid generator SOPHIA and a post-processor JASPER for graphical display of results. Both SOPHIA and JASPER are extensions of the support software originally written for the ASTEC code, also promoted by CFDS. The latest release of FLOW3D contains well-tested turbulence and combustion models and, in a less-developed form, a multi-phase modelling potential. This document describes briefly the modelling capabilities of FLOW3D (Release 3.2) and outlines implementation procedures for the VAX, CRAY and CONVEX computer systems. Additional remarks are made concerning the in-house support programs which have been specially written in order to adapt existing ASTEC input data for use with FLOW3D; these programs operate within a VAX-VMS environment. Three sample calculations have been performed and results compared with those obtained previously using the ASTEC code, and checked against other available data, where appropriate. (author) 35 figs., 3 tabs., 42 refs

  17. A Closed Form Solution to Segment 3D Motion Using Straight-line Optical Flow

    ZHANG Jing; SHI Fan-huai; MA Wen-juan; LIU Yun-cai

    2008-01-01

    A closed form solution to the problem of segmenting multiple 3D motion models was proposed fromstraight-line optical flow. It introduced the multibody line optical flow constraint (MLOFC), a polynomial equation relating motion models and line parameters. The motion models can be obtained analytically as the derivative of the MLOFC at the corresponding line measurement, without knowing the motion model associated with that line. Experiments on real and synthetic sequences were also presented.

  18. Comparison of Tomo-PIV and 3D-PTV for microfluidic flows

    Two 3D-3C velocimetry techniques for micro-scale measurements are compared: tomographic particle image velocimetry (Tomo-PIV) and 3D particle-tracking velocimetry (3D-PTV). Both methods are applied to experimental data from a confined shear-driven liquid droplet over a moving surface. The droplet has 200 μm height and 2 mm diameter. Micro 3D-PTV and Tomo-PIV are used to obtain the tracer particle distribution and the flow velocity field for the same set of images. It is shown that the reconstructed particle distributions are distinctly different, where Tomo-PIV returns a nearly uniform distribution over the height of the volume, as expected, and PTV reveals a clear peak in the particle distribution near the plane of focus. In Tomo-PIV, however, the reconstructed particle peak intensity decreases in proportion to the distance from the plane of focus. Due to the differences in particle distributions, the measured flow velocities are also different. In particular, we observe Tomo-PIV to be in closer agreement with mass conservation. Furthermore, the random noise level is found to increase with distance to the plane of focus at a higher rate for 3D-PTV as compared to Tomo-PIV. Thus, for a given noise threshold value, the latter method can measure reliably over a thicker volume. (paper)

  19. In vivo analysis of physiological 3D blood flow of cerebral veins

    Schuchardt, Florian; Schroeder, Laure; Baeuerle, Jochen; Harloff, Andreas [University Medical Centre, Department of Neurology, Freiburg (Germany); Anastasopoulos, Constantin [University Medical Center, Department of Neuropaediatrics and Muscle Disorders, Freiburg (Germany); University Medical Centre, Department of Neuroradiology, Freiburg (Germany); Markl, Michael [Northwestern University, Department of Radiology, Feinberg School of Medicine and McCormick School of Engineering, Chicago, IL (United States); Hennemuth, Anja; Drexl, Johann [Fraunhofer MEVIS, Bremen (Germany); Valdueza, Jose M. [Neurological Center, Segeberger Kliniken, Bad Segeberg (Germany); Mader, Irina [University Medical Centre, Department of Neuroradiology, Freiburg (Germany)

    2015-08-15

    To visualize and quantify physiological blood flow of intracranial veins in vivo using time-resolved, 3D phase-contrast MRI (4D flow MRI), and to test measurement accuracy. Fifteen healthy volunteers underwent repeated ECG-triggered 4D flow MRI (3 Tesla, 32-channel head coil). Intracranial venous blood flow was analysed using dedicated software allowing for blood flow visualization and quantification in analysis planes at the superior sagittal, straight, and transverse sinuses. MRI was evaluated for intra- and inter-observer agreement and scan-rescan reproducibility. Measurements of the transverse sinuses were compared with transcranial two-dimensional duplex ultrasound. Visualization of 3D blood flow within cerebral sinuses was feasible in 100 % and within at least one deep cerebral vein in 87 % of the volunteers. Blood flow velocity/volume increased along the superior sagittal sinus and was lower in the left compared to the right transverse sinus. Intra- and inter-observer reliability and reproducibility of blood flow velocity (mean difference 0.01/0.02/0.02 m/s) and volume (mean difference 0.0002/-0.0003/0.00003 l/s) were good to excellent. High/low velocities were more pronounced (8 % overestimation/9 % underestimation) in MRI compared to ultrasound. Four-dimensional flow MRI reliably visualizes and quantifies three-dimensional cerebral venous blood flow in vivo and is promising for studies in patients with sinus thrombosis and related diseases. (orig.)

  20. Magnetic resonance velocity mapping of 3D cerebrospinal fluid flow dynamics in hydrocephalus: preliminary results

    Stadlbauer, Andreas [Landesklinikum St. Poelten, MR Physics Group, Department of Radiology, St. Poelten (Austria); University of Erlangen-Nuremberg, Department of Neurosurgery, Erlangen (Germany); Salomonowitz, Erich [Landesklinikum St. Poelten, MR Physics Group, Department of Radiology, St. Poelten (Austria); Brenneis, Christian [Landesklinikum St. Poelten, Department of Neurology, St. Poelten (Austria); Ungersboeck, Karl [Landesklinikum St. Poelten, Department of Neurosurgery, St. Poelten (Austria); Riet, Wilma van der [European MRI Consultancy (EMRIC), Strasbourg (France); Buchfelder, Michael; Ganslandt, Oliver [University of Erlangen-Nuremberg, Department of Neurosurgery, Erlangen (Germany)

    2012-01-15

    To investigate the detectability of CSF flow alterations in the ventricular system of patients with hydrocephalus using time-resolved 3D MR velocity mapping. MR velocity mapping was performed in 21 consecutive hydrocephalus patients and 21 age-matched volunteers using a 3D phase-contrast (PC) sequence. Velocity vectors and particle path lines were calculated for visualisation of flow dynamics. CSF flow was classified as ''hypomotile flow'' if it showed attenuated dynamics and as ''hypermotile flow'' if it showed increased dynamics compared with volunteers. Diagnostic efficacy was compared with routine 2D cine PC-MRI. Seven patients showed hypomotile CSF flow: six had non-communicating hydrocephalus due to aqueductal stenosis. One showed oscillating flow between the lateral ventricles after craniotomy for intracranial haemorrhage. Seven patients showed normal flow: six had hydrocephalus ex vacuo due to brain atrophy. One patient who underwent ventriculostomy 10 years ago showed a flow path through the opening. Seven patients showed hypermotile flow: three had normal pressure hydrocephalus, three had dementia, and in one the diagnosis remained unclear. The diagnostic efficacy of velocity mapping was significantly higher except for that of aqueductal stenosis. Our approach may be useful for diagnosis, therapy planning, and follow-up of different kinds of hydrocephalus. (orig.)

  1. Structural elements and collapse regimes in 3D flows on a slope

    The mechanisms and structural elements of an instability whose development results in the collapse of flow fragments have been studied in the scope of the Hamilton version of the “shallow water” 3D model on a slope. The study indicated that the 3D model differs from its 2D analog in a more varied set of collapsing solutions. In particular, the solutions describing anisotropic collapse, during which the area of a collapsing fragment in contact with the slope contracts into a segment rather than a point, exist together with the solutions describing radially symmetric (isotropic) collapse.

  2. Flow Exergy as a Lagrangian for the Navier-Stokes Equations for Incompressible Flow

    Enrico Sciubba

    2004-09-01

    Full Text Available

    A novel variational derivation of the Navier-Stokes equations for incompressible flows is presented and discussed. The Lagrangian density is obtained from the exergy balance equation written for both the (Lagrangian steady and quasi-stationary isothermal flows of an incompressible fluid. The exergy of a fluid mass (composed of a kinetic, a pressure-work, a diffusive, and a dissipative portion, the latter being the result of viscous irreversibility is derived first, and it is then shown that a formal minimisation of the exergy variation (i.e. destruction generates, without recurring to “local potentials”, the Navier-Stokes equations of motion under the given assumptions. The acceleration being held constant, the proposed variational method can be classified as a “restricted” principle.

    The problem is also briefly discussed both in its historical perspective and in its possible formal and practical implications.

  3. Navier-Stokes solver using Green's functions I: channel flow and plane Couette flow

    Viswanath, Divakar

    2012-01-01

    Numerical solvers of the incompressible Navier-Stokes equations have reproduced turbulence phenomena such as the law of the wall, the dependence of turbulence intensities on the Reynolds number, and experimentally observed properties of turbulence energy production. In this article, we begin a sequence of investigations whose eventual aim is to derive and implement numerical solvers that can reach higher Reynolds numbers than is currently possible. Every time step of a Navier-Stokes solver in effect solves a linear boundary value problem. The use of Green's functions leads to numerical solvers which are highly accurate in resolving the boundary layer, which is a source of delicate but exceedingly important physical effects at high Reynolds numbers. The use of Green's functions brings with it a need for careful quadrature rules and a reconsideration of time steppers. We derive and implement Green's function based solvers for the channel flow and plane Couette flow geometries. The solvers are validated by repro...

  4. Computational fluid dynamics simulations of blood flow regularized by 3D phase contrast MRI

    Rispoli, Vinicius C; Nielsen, Jon; Nayak, Krishna S;

    2015-01-01

    BACKGROUND: Phase contrast magnetic resonance imaging (PC-MRI) is used clinically for quantitative assessment of cardiovascular flow and function, as it is capable of providing directly-measured 3D velocity maps. Alternatively, vascular flow can be estimated from model-based computation fluid...... approach in regularizing 3D flow fields is evaluated. METHODS: The proposed algorithm incorporates both a Newtonian fluid physics model and a linear PC-MRI signal model. The model equations are solved numerically using a modified CFD algorithm. The numerical solution corresponds to the optimal solution of...... dynamics (CFD) calculations. CFD provides arbitrarily high resolution, but its accuracy hinges on model assumptions, while velocity fields measured with PC-MRI generally do not satisfy the equations of fluid dynamics, provide limited resolution, and suffer from partial volume effects. The purpose of this...

  5. A fast and accurate method to predict 2D and 3D aerodynamic boundary layer flows

    A quasi-simultaneous interaction method is applied to predict 2D and 3D aerodynamic flows. This method is suitable for offshore wind turbine design software as it is a very accurate and computationally reasonably cheap method. This study shows the results for a NACA 0012 airfoil. The two applied solvers converge to the experimental values when the grid is refined. We also show that in separation the eigenvalues remain positive thus avoiding the Goldstein singularity at separation. In 3D we show a flow over a dent in which separation occurs. A rotating flat plat is used to show the applicability of the method for rotating flows. The shown capabilities of the method indicate that the quasi-simultaneous interaction method is suitable for design methods for offshore wind turbine blades

  6. Parallel Adaptive Computation of Blood Flow in a 3D ``Whole'' Body Model

    Zhou, M.; Figueroa, C. A.; Taylor, C. A.; Sahni, O.; Jansen, K. E.

    2008-11-01

    Accurate numerical simulations of vascular trauma require the consideration of a larger portion of the vasculature than previously considered, due to the systemic nature of the human body's response. A patient-specific 3D model composed of 78 connected arterial branches extending from the neck to the lower legs is constructed to effectively represent the entire body. Recently developed outflow boundary conditions that appropriately represent the downstream vasculature bed which is not included in the 3D computational domain are applied at 78 outlets. In this work, the pulsatile blood flow simulations are started on a fairly uniform, unstructured mesh that is subsequently adapted using a solution-based approach to efficiently resolve the flow features. The adapted mesh contains non-uniform, anisotropic elements resulting in resolution that conforms with the physical length scales present in the problem. The effects of the mesh resolution on the flow field are studied, specifically on relevant quantities of pressure, velocity and wall shear stress.

  7. 3D flow past transonic turbine cascade SE 1050 — Experiment and numerical simulations

    Šimurda, D.; Fürst, J.; Luxa, M.

    2013-08-01

    This paper is concerned with experimental and numerical research on 3D flow past prismatic turbine cascade SE1050 (known in QNET network as open test case SE1050). The primary goal was to assess the influence of the inlet velocity profile on the flow structures in the interblade channel and on the flow field parameters at the cascade exit and to compare these findings to results of numerical simulations. Investigations of 3D flow past the cascade with non-uniform inlet velocity profile were carried out both experimentally and numerically at subsonic ( M 2is = 0.8) and at transonic ( M 2is = 1.2) regime at design angle of incidence. Experimental data was obtained using a traversing device with a five-hole conical probe. Numerically, the 3D flow was simulated by open source code OpenFOAM and in-house code. Analyses of experimental data and CFD simulations have revealed the development of distinctive vortex structures resulting from non-uniform inlet velocity profile. Origin of these structures results in increased loss of kinetic energy and spanwise shift of kinetic energy loss coefficient distribution. Differences found between the subsonic and the transonic case confirm earlier findings available in the literature. Results of CFD and experiments agree reasonably well.

  8. Numerical modelling of gravel unconstrained flow experiments with the DAN3D and RASH3D codes

    Sauthier, Claire; Pirulli, Marina; Pisani, Gabriele; Scavia, Claudio; Labiouse, Vincent

    2015-12-01

    Landslide continuum dynamic models have improved considerably in the last years, but a consensus on the best method of calibrating the input resistance parameter values for predictive analyses has not yet emerged. In the present paper, numerical simulations of a series of laboratory experiments performed at the Laboratory for Rock Mechanics of the EPF Lausanne were undertaken with the RASH3D and DAN3D numerical codes. They aimed at analysing the possibility to use calibrated ranges of parameters (1) in a code different from that they were obtained from and (2) to simulate potential-events made of a material with the same characteristics as back-analysed past-events, but involving a different volume and propagation path. For this purpose, one of the four benchmark laboratory tests was used as past-event to calibrate the dynamic basal friction angle assuming a Coulomb-type behaviour of the sliding mass, and this back-analysed value was then used to simulate the three other experiments, assumed as potential-events. The computational findings show good correspondence with experimental results in terms of characteristics of the final deposits (i.e., runout, length and width). Furthermore, the obtained best fit values of the dynamic basal friction angle for the two codes turn out to be close to each other and within the range of values measured with pseudo-dynamic tilting tests.

  9. A 3D pseudospectral algorithm to simulate rotating flows in cylindrical cavities

    Peres, Noele; Poncet, Sébastien; Serre, Eric

    2012-01-01

    When simulating flows in cylindrical rotating cavities a difficulty arises from the singularities appearing on the axis. Its singularities are due to the presence of terms 1/r^n (n = 1, 2) in the Navier-Stokes equations, where r is the radial dis-tance. To avoid evaluating differential equation coefficients which are infinite at that point, the grid must exclude the origin or specific pole conditions must be imposed. An efficient and accurate pseudo-spectral method has been here developed usi...

  10. Delft3D-FLOW on PRACE infrastructures for real life hydrodynamic applications.

    Donners, John; Genseberger, Menno; Jagers, Bert; de Goede, Erik; Mourits, Adri

    2013-04-01

    PRACE, the Partnership for Advanced Computing in Europe, offers access to the largest high-performance computing systems in Europe. PRACE invites and helps industry to increase their innovative potential through the use of the PRACE infrastructure. This poster describes different efforts to assist Deltares with porting the open-source simulation software Delft3D-FLOW to PRACE infrastructures. Analysis of the performance on these infrastructures has been done for real life flow applications. Delft3D-FLOW is a 2D and 3D shallow water solver which calculates non-steady flow and transport phenomena resulting from tidal and meteorological forcing on a curvilinear, boundary fitted grid in Cartesian or spherical coordinates. It also includes a module which sediment transport (both suspended and bed total load) and morphological changes for an arbitrary number of cohesive and non-cohesive fractions. As Delft3D-FLOW has been developed over several decades, with a variety of functionality and over 350k lines of source code, porting to PRACE infrastructures needs some effort. At the moment Delft3D-FLOW uses MPI with domain decomposition in one direction as its parallellisation approach. Because it is hard to identify scaling issues if one immediately starts with a complex case with many features enabled, different cases with increasing complexity have been used to investigate scaling of this parallellisation approach on several PRACE platforms. As a base reference case we started with a schematic high-resolution 2D hydrodynamic model of the river Waal that turned out to be surprisingly well-suited to the highly-parallel PRACE machines. Although Delft3D-FLOW employs a sophisticated build system, several modifications were required to port it to most PRACE systems due to the use of specific, highly-tuned compilers and MPI-libraries. After this we moved to a 3D hydrodynamic model of Rotterdam harbour that includes sections of the rivers Rhine and Meuse and a part of the North

  11. Numerical and experimental investigation of the 3D free surface flow in a model Pelton turbine

    This investigation focuses on the numerical and experimental analysis of the 3D free surface flow in a Pelton turbine. In particular, two typical flow conditions occurring in a full scale Pelton turbine - a configuration with a straight inlet as well as a configuration with a 90 degree elbow upstream of the nozzle - are considered. Thereby, the effect of secondary flow due to the 90 degree bending of the upstream pipe on the characteristics of the jet is explored. The hybrid flow field consists of pure liquid flow within the conduit and free surface two component flow of the liquid jet emerging out of the nozzle into air. The numerical results are validated against experimental investigations performed in the laboratory of the Institute of Fluid Mechanics (FLM). For the numerical simulation of the flow the in-house unstructured fully parallelized finite volume solver solver3D is utilized. An advanced interface capturing model based on the classic Volume of Fluid method is applied. In order to ensure sharp interface resolution an additional convection term is added to the transport equation of the volume fraction. A collocated variable arrangement is used and the set of non-linear equations, containing fluid conservation equations and model equations for turbulence and volume fraction, are solved in a segregated manner. For pressure-velocity coupling the SIMPLE and PISO algorithms are implemented. Detailed analysis of the observed flow patterns in the jet and of the jet geometry are presented.

  12. Selecting 3D Chaotic Flow States for Accelerated DNA Replication in Micro Scale Convective PCR

    Priye, Aashish; Hassan, Yassin; Ugaz, Victor

    2016-01-01

    Micro-scale flow in cylindrical geometries can harness chaotic advection to perform complex thermally activated biochemical reactions such as the polymerase chain reaction (PCR). We have applied a 3D computational fluid dynamics model to resolve the complex flow patterns in such geometries. The resulting 3D flow trajectories are then used as input to a kinetic model to resolve the time evolution of DNA replication process. A simple mass action kinetic model was developed to couple these biochemical reactions with the intricate flow. Residence time analysis of virtual particles in the flow revealed that the flow has a strong chaotic component in wider geometries in comparison with taller geometries (quasi periodic motion). This work shows, for the first time that the chaotic aspect of the flow field plays a key role in determining the strength of the coupling between the reactions and the flow. Our model can quantify the doubling times of these reactions capturing the lag, exponential and plateau phases of PCR...

  13. Wavelet-based adaptive numerical simulation of unsteady 3D flow around a bluff body

    de Stefano, Giuliano; Vasilyev, Oleg

    2012-11-01

    The unsteady three-dimensional flow past a two-dimensional bluff body is numerically simulated using a wavelet-based method. The body is modeled by exploiting the Brinkman volume-penalization method, which results in modifying the governing equations with the addition of an appropriate forcing term inside the spatial region occupied by the obstacle. The volume-penalized incompressible Navier-Stokes equations are numerically solved by means of the adaptive wavelet collocation method, where the non-uniform spatial grid is dynamically adapted to the flow evolution. The combined approach is successfully applied to the simulation of vortex shedding flow behind a stationary prism with square cross-section. The computation is conducted at transitional Reynolds numbers, where fundamental unstable three-dimensional vortical structures exist, by well-predicting the unsteady forces arising from fluid-structure interaction.

  14. PIV measurements in a microfluidic 3D-sheathing structure with three-dimensional flow behaviour

    Klank, Henning; Goranovic, Goran; Kutter, Jörg Peter; Gjelstrup, Henrik; Michelsen, J.; Westergaard, C.H.

    2002-01-01

    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. 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...

  15. Computation of aircraft component flow fields at transonic Mach numbers using a three-dimensional Navier-Stokes algorithm

    Shrewsbury, George D.; Vadyak, Joseph; Schuster, David M.; Smith, Marilyn J.

    1989-01-01

    A computer analysis was developed for calculating steady (or unsteady) three-dimensional aircraft component flow fields. This algorithm, called ENS3D, can compute the flow field for the following configurations: diffuser duct/thrust nozzle, isolated wing, isolated fuselage, wing/fuselage with or without integrated inlet and exhaust, nacelle/inlet, nacelle (fuselage) afterbody/exhaust jet, complete transport engine installation, and multicomponent configurations using zonal grid generation technique. Solutions can be obtained for subsonic, transonic, or hypersonic freestream speeds. The algorithm can solve either the Euler equations for inviscid flow, the thin shear layer Navier-Stokes equations for viscous flow, or the full Navier-Stokes equations for viscous flow. The flow field solution is determined on a body-fitted computational grid. A fully-implicit alternating direction implicit method is employed for the solution of the finite difference equations. For viscous computations, either a two layer eddy-viscosity turbulence model or the k-epsilon two equation transport model can be used to achieve mathematical closure.

  16. 3D mathematical model for suspended load transport by turbulent flows and its applications

    LU Yongjun; DOU Guoren; HAN Longxi; SHAO Xuejun; YANG Xianghua

    2004-01-01

    This paper presents a 3D mathematical model for suspended load transport in turbulent flows. Based on Dou's stochastic theory of turbulent flow, numerical schemes of Reynolds stresses for anisotropic turbulent flows were obtained. A refined wall function was employed to treat solid wall boundaries. The equations for 2D suspended load motion and sorting of bed material have been expanded into 3D cases. Numerical results are validated by the measured data of the Gezhouba Project, and proved to be in good agreement with the experimental. The present method has been employed to simulate sediment erosion and deposition in the dam area of Three Gorges Project, and for the operation of the project, siltation process and deposition pattern in the near-dam area of the reservoir, size distribution of the deposits and bed material, and flow fields and sediment concentration fields at different time and elevations are predicted. The predicted results are close to the experimental observations in physical model studies. Thus, a new method is established for 3D simulation of sediment motion in dam areas of multi-purpose water projects.

  17. Quasi 3D modeling of water flow and solute transport in vadose zone and groundwater

    Yakirevich, A.; Kuznetsov, M.; Weisbrod, N.; Pachepsky, Y. A.

    2013-12-01

    The complexity of subsurface flow systems calls for a variety of concepts leading to the multiplicity of simplified flow models. One commonly used simplification is based on the assumption that lateral flow and transport in unsaturated zone is insignificant unless the capillary fringe is involved. In such cases the flow and transport in the unsaturated zone above groundwater level can be simulated as a 1D phenomenon, whereas through groundwater they are viewed as 2D or 3D phenomena. A new approach for a numerical scheme for 3D variably saturated flow and transport is presented. A Quasi-3D approach allows representing flow in the 'vadose zone - aquifer' system by a series of 1D Richards' equations solved in variably-saturated zone and by 3D-saturated flow equation in groundwater (modified MODFLOW code). The 1D and 3D equations are coupled at the phreatic surface in a way that aquifer replenishment is calculated using the Richards' equation, and solving for the moving water table does not require definition of the specific yield parameter. The 3D advection-dispersion equation is solved in the entire domain by the MT3D code. Using implicit finite differences approximation to couple processes in the vadose zone and groundwater provides mass conservation and increase of computational efficiency. The above model was applied to simulate the impact of irrigation on groundwater salinity in the Alto Piura aquifer (Northern Peru). Studies on changing groundwater quality in arid and semi-arid lands show that irrigation return flow is one of the major factors contributing to aquifer salinization. Existing mathematical models do not account explicitly for the solute recycling during irrigation on a daily scale. Recycling occurs throughout the unsaturated and saturated zones, as function of the solute mass extracted from pumping wells. Salt concentration in irrigation water is calculated at each time step as a function of concentration of both surface water and groundwater

  18. Modeling 3-D flow in the mantle wedge with complex slab geometries: Comparisons with seismic anisotropy

    Kincaid, C. R.; MacDougall, J. G.; Druken, K. A.; Fischer, K. M.

    2010-12-01

    Understanding patterns in plate scale mantle flow in subduction zones is key to models of thermal structure, dehydration reactions, volatile distributions and magma generation and transport in convergent margins. Different patterns of flow in the mantle wedge can generate distinct signatures in seismological observables. Observed shear wave fast polarization directions in several subduction zones are inconsistent with predictions of simple 2-D wedge corner flow. Geochemical signatures in a number of subduction zones also indicate 3-D flow and entrainment patterns in the wedge. We report on a series of laboratory experiments on subduction driven flow to characterize spatial and temporal variability in 3-D patterns in flow and shear-induced finite strain. Cases focus on how rollback subduction, along-strike dip changes in subducting plates and evolving gaps or tears in subduction zones control temporal-spatial patterns in 3-D wedge flow. Models utilize a glucose working fluid with a temperature dependent viscosity to represent the upper 2000 km of the mantle. Subducting lithosphere is modeled with two rubber-reinforced continuous belts. Belts pass around trench and upper/lower mantle rollers. The deeper rollers can move laterally to allow for time varying dip angle. Each belt has independent speed control and dip adjustment, allowing for along-strike changes in convergence rate and the evolution of slab gaps. Rollback is modeled using a translation system to produce either uniform and asymmetric lateral trench motion. Neutral density finite strain markers are distributed throughout the fluid and used as proxies for tracking the evolution of anisotropy through space and time in the evolving flow fields. Particle image velocimetry methods are also used to track time varying 3-D velocity fields for directly calculating anisotropy patterns. Results show that complex plate motions (rollback, steepening) and morphologies (gaps) in convergent margins produce flows with

  19. Numerical simulation of complex 3D compressible viscous flows through rotating blade passage

    Despotović M.

    2003-01-01

    Full Text Available This paper describes a three-dimensional compressible Navier-Stokes code, which has been developed for analysis of turbocompressor blade rows and other internal flows. Despite numerous numerical techniques and statement that Computational Fluid Dynamics has reached state of the art, issues related to successful simulations represent valuable database of how particular tech­nique behave for a specifie problem. This paper deals with rapid numerical method accurate enough to be used as a design tool. The mathematical model is based on System of Favre averaged Navier-Stokes equations that are written in relative frame of reference, which rotates with constant angular velocity around axis of rotation. The governing equations are solved using finite vol­ume method applied on structured grids. The numerical procedure is based on the explicit multistage Runge-Kutta scheme that is coupled with modem numerical procedures for convergence acceleration. To demonstrate the accuracy of the described numer­ical method developed software is applied to numerical analysis of flow through impeller of axial turbocompressor, and obtained results are compared with available experimental data.

  20. 3D Particle image velocimetry test of inner flow in a double blade pump impeller

    Liu, Houlin; Wang, Kai; Yuan, Shouqi; Tan, Minggao; Wang, Yong; Ru, Weimin

    2012-05-01

    The double blade pump is widely used in sewage treatment industry, however, the research on the internal flow characteristics of the double blade pump with particle image velocimetry (PIV) technology is very little at present. To reveal inner flow characteristics in double blade pump impeller under off-design and design conditions, inner flows in a double blade pump impeller, whose specific speed is 111, are measured under the five off-design conditions and design condition by using 3D PIV test technology. In order to ensure the accuracy of the 3D PIV test, the external trigger synchronization system which makes use of fiber optic and equivalent calibration method are applied. The 3D PIV relative velocity synthesis procedure is compiled by using Visual C++ 2005. Then absolute velocity distribution and relative velocity distribution in the double blade pump impeller are obtained. Test results show that vortex exists in each condition, but the location, size and velocity of vortex core are different. Average absolute velocity value of impeller outlet increases at first, then decreases, and then increases again with increase of flow rate. Again average relative velocity values under 0.4, 0.8, and 1.2 design condition are higher than that under 1.0 design condition, while under 0.6 and 1.4 design condition it is lower. Under low flow rate conditions, radial vectors of absolute velocities at impeller outlet and blade inlet near the pump shaft decrease with increase of flow rate, while that of relative velocities at the suction side near the pump shaft decreases. Radial vectors of absolute velocities and relative velocities change slightly under the two large flow rate conditions. The research results can be applied to instruct the hydraulic optimization design of double blade pumps.

  1. Nonlinear analysis of chaotic flow in a 3D closed-loop pulsating heat pipe

    Pouryoussefi, S M

    2016-01-01

    Numerical simulation has been conducted for the chaotic flow in a 3D closed-loop pulsating heat pipe (PHP). Heat flux and constant temperature boundary conditions were applied for evaporator and condenser sections, respectively. Water and ethanol were used as working fluids. Volume of Fluid (VOF) method has been employed for two-phase flow simulation. Spectral analysis of temperature time series was carried out using Power Spectrum Density (PSD) method. Existence of dominant peak in PSD diagram indicated periodic or quasi-periodic behavior in temperature oscillations at particular frequencies. Correlation dimension values for ethanol as working fluid was found to be higher than that for water under the same operating conditions. Similar range of Lyapunov exponent values for the PHP with water and ethanol as working fluids indicated strong dependency of Lyapunov exponent to the structure and dimensions of the PHP. An O-ring structure pattern was obtained for reconstructed 3D attractor at periodic or quasi-peri...

  2. Sand transverse dune aerodynamics: 3D Coherent Flow Structures from a computational study

    Bruno, Luca

    2015-01-01

    The engineering interest about dune fields is dictated by the their interaction with a number of human infrastructures in arid environments. The aerodynamic behaviour of sand dunes in atmospheric boundary layer belongs to the class of bluff bodies. Because of their simple geometry and their frequent occurrence in desert area, transverse sand dunes are usually adopted in literature as a benchmark to investigate dune aerodynamics by means of both computational or experimental approach, usually in nominally 2D setups. The writers suspect the flow in the wake is characterised by 3D features and affected by wind tunnel setup - e.g. blockage effect, duct side wall boundary layer, incoming velocity profile - when experimental studies are carried out. The present study aims at evaluating the 3D flow features of an idealised transverse dune under different setup conditions by means of computational simulations and to compare the obtained results with experimental measurements.

  3. Influence of Underhood Flow on Engine Cooling Using 1-D And 3-D Approach

    Bolehovský Ondřej; Novotný Jan

    2015-01-01

    This work deals with numerical simulation of complete cooling system of internal combustion engine (GT-SUITE), which also involves the simulation of flow in underhood using the computationally undemanding simulation. A detailed model of the internal combustion engine is extended to a cooling circuit model which is then coupled to a simplified underhood model which is created with the help of GT-COOL application as a 3-D model and afterwards transferred to a 1-D form. The approaches, one using...

  4. 3D-printing of Redox flow batteries for energy storage: a rapid prototype laboratory cell

    Arenas-Martinez, L.F.; Walsh, F.C.; Ponce de Leon, C.

    2015-01-01

    Although interest in redox flow batteries (RFBs) for energy storage has grown over the last few years, implementation of RFB technology has been slow and challenging. Recent developments in 3D-printing of materials enable a transforming technology for fast, reproducible and documented cell manufacture. This technology can give an improved engineering approach to cell design and fabrication, needed to fulfil requirements for lower cost, longer lifetime hardware capable of efficient reliable pe...

  5. Numerical Calculation of the Flow Inside Pump Impellers Using 3D Euler Equations

    SARIOĞLU, Kemal; Ayder, Erkan

    1999-01-01

    The flow pattern inside an impeller should be determined for maximum efficiency and performance. The effects of the design parameters on the pump performance can be determined using numerical calculations instead of empirical equations. Incompressible 3D time-dependent Euler equations, written in a conservative form, are used. An artificial pressure term is added to preserve the hyperbolic character of the equations. A finite-volume technique is used for space discretization. A fou...

  6. Rotary slanted single wire CTA – a useful tool for 3D flows investigations

    Jonáš P.

    2013-01-01

    The procedure is described of experimental investigation of a statistically stationary generally nonisothermal 3D flow by means of a constant temperature anemometer (CTA) using single slanted heated wire, rotary round the fixed axis. The principle of this procedure is quite clear. The change of the heated wire temperature modifies ratio of CTA sensitivities to temperature and velocity fluctuations. Turning the heated wire through a proper angle changes the sensitivity to components of the ins...

  7. Empirical Modeling of Spatial 3D Flow Characteristics Using a Remote-Controlled ADCP System: Monitoring a Spring Flood

    Claude Flener; Yunsheng Wang; Leena Laamanen; Elina Kasvi; Jenni-Mari Vesakoski; Petteri Alho

    2015-01-01

    The use of acoustic Doppler current profilers (ADCP) for measuring streamflow and discharge is becoming increasingly widespread. The spatial distribution of flow patterns is useful data in studying riverine habitats and geomorphology. Until now, most flow mapping has focused on measurements along a series of transects in a channel. Here, we set out to measure, model and analyze the 3D flow characteristics of a natural river over a continuous areal extent, quantifying flow velocity, 3D flow di...

  8. Ultrarapid detection of pathogenic bacteria using a 3D immunomagnetic flow assay.

    Lee, Wonjae; Kwon, Donghoon; Chung, Boram; Jung, Gyoo Yeol; Au, Anthony; Folch, Albert; Jeon, Sangmin

    2014-07-01

    We developed a novel 3D immunomagnetic flow assay for the rapid detection of pathogenic bacteria in a large-volume food sample. Antibody-functionalized magnetic nanoparticle clusters (AbMNCs) were magnetically immobilized on the surfaces of a 3D-printed cylindrical microchannel. The injection of a Salmonella-spiked sample solution into the microchannel produced instant binding between the AbMNCs and the Salmonella bacteria due to their efficient collisions. Nearly perfect capture of the AbMNCs and AbMNCs-Salmonella complexes was achieved under a high flow rate by stacking permanent magnets with spacers inside the cylindrical separator to maximize the magnetic force. The concentration of the bacteria in solution was determined using ATP luminescence measurements. The detection limit was better than 10 cfu/mL, and the overall assay time, including the binding, rinsing, and detection steps for a 10 mL sample took less than 3 min. To our knowledge, the 3D immunomagnetic flow assay described here provides the fastest high-sensitivity, high-capacity method for the detection of pathogenic bacteria. PMID:24856003

  9. Flow structure of the solids in a 3-D gas-liquid-solid fluidized bed

    Larachi, F.; Cassanello, M.; Chaouki, J.; Guy, C. [Ecole Polytechnique, Montreal, Quebec (Canada). Dept. of Chemical Engineering

    1996-09-01

    Gas-liquid-solid fluidized systems have made inroads into a variety of industrial applications from heavy oil, petroleum resid, and synthetic crude processing to fermentation and aerobic biological wastewater treatment. Local and macroscopic solids flow structure and kinematics in a 3-D gas-liquid-solid fluidized bed were studied using a noninvasive radioactive-particle tracking (RPT) technique. Based on the multisite detection of {gamma} radiations emitted from a single radiolabeled tracer particle freely moving in the fluidized bed, RPT permitted the authors to obtain fast sampling of 3-D trajectories of the tracer, whose physical properties were similar to those of the solids inventory. These trajectories showed the detailed motion sequences of the solid particles as entrained in the bubble wakes, fluctuating randomly or sinking deterministically in the liquid-solid emulsion. Based on measurements done in the vortical-spiral flow regime, the dynamic solids flow structure inside a three-phase fluidized bed can be viewed as a three-zone core-annulus-annulus structure: a central fast-bubble flow region with the particles swirling upward; a vortical flow region around the velocity inversion point with the particles momentarily captured in emulsion vortices; and a relatively bubble-free descending flow region where the particles spiral down between the velocity inversion point and vessel walls. The flow structure of dense fluidized beds are similar to the flow structure of liquid and/or solid in lean fluidized beds. Measured distributions of local ensemble-averaged particle velocities and turbulence intensities were consistent with the existence of a toroidal recirculatory solids flow pattern in the bed. Measured mean circumferential ensemble-averaged radial velocity was essentially zero throughout most of the bed. The solids flow turbulence field was nonisotropic, as radial turbulence intensities were generally lower than longitudinal turbulence intensities.

  10. NUMERICAL SIMULATION OF 3-D FLOW FIELD IN ARCIFORM PLUNGE POOL

    2002-01-01

    The 3-D complex turbulent flow fields in aplunge pool with arciform bottom are simulated by using thek-ε model in body-fitted coordinates. The calculated results re-veal the flow characteristics in the arciform plunge pool underthe different flood discharge conditions, which can not be easi-ly obtained in the physical model test because the measure-ment of the complex velocity is very difficult. The calculatedflow fields are helpful to understand in depth the hydrauliccharacteristics of plunge pool. The calculated and the meas-ured pressure distributions on the pool bottom are comparedand in good agreement.

  11. Nonhydrostatic granular flow over 3-D terrain: New Boussinesq-type gravity waves?

    Castro-Orgaz, Oscar; Hutter, Kolumban; Giraldez, Juan V.; Hager, Willi H.

    2015-01-01

    granular mass flow is a basic step in the prediction and control of natural or man-made disasters related to avalanches on the Earth. Savage and Hutter (1989) pioneered the mathematical modeling of these geophysical flows introducing Saint-Venant-type mass and momentum depth-averaged hydrostatic equations using the continuum mechanics approach. However, Denlinger and Iverson (2004) found that vertical accelerations in granular mass flows are of the same order as the gravity acceleration, requiring the consideration of nonhydrostatic modeling of granular mass flows. Although free surface water flow simulations based on nonhydrostatic depth-averaged models are commonly used since the works of Boussinesq (1872, 1877), they have not yet been applied to the modeling of debris flow. Can granular mass flow be described by Boussinesq-type gravity waves? This is a fundamental question to which an answer is required, given the potential to expand the successful Boussinesq-type water theory to granular flow over 3-D terrain. This issue is explored in this work by generalizing the basic Boussinesq-type theory used in civil and coastal engineering for more than a century to an arbitrary granular mass flow using the continuum mechanics approach. Using simple test cases, it is demonstrated that the above question can be answered in the affirmative way, thereby opening a new framework for the physical and mathematical modeling of granular mass flow in geophysics, whereby the effect of vertical motion is mathematically included without the need of ad hoc assumptions.

  12. Flow measurements in a model centrifugal pump by 3-D PIV

    Yang, H.; Xu, H. R.; Liu, C.

    2012-11-01

    PIV (Particle Image Velocimetry), as an non-intrusive flow measurements technology, is widely used to investigate the flow fields in many areas. 3-D (three Dimensional) PIV has seldom been used to measure flow field in rotational impeller of centrifugal pump due to the difficulty of calibration in samll space. In this article, a specially manufactured water tank was used to perform the calibration for 3-D PIV measurement. The instantaneous absolute velocity in one impeller passage was obtained by merging of three sub zones and the relative velocity was acquired by velocity decomposition. The result shows that, when the pump runs at the condition of design flow rate, the radial component velocity Wr appears a concave distribution except the condition of R=45 mm. With the increase of radius, the circumference location of the minimum radial component velocity Wr moves from the pressure side to the suction side. At the same time, the tangential component velocity Wθ on the suction side decreases gradually with the increase of radius, while the component on the pressure side increases gradually. The secondary flow in different radius section has also been shown. At last, the error of PIV measurements was analyzed, which shows that the test results are accurate and the measured data is reliable.

  13. 3D MHD free surface fluid flow simulation based on magnetic-field induction equations

    The purpose of this paper is to present our recent efforts on 3D MHD model development and our results based on the technique derived from induced-magnetic-field equations. Two important features are utilized in our numerical method to obtain convergent solutions. First, a penalty factor is introduced in order to force the local divergence free condition of the magnetic fields. The second is that we extend the insulating wall thickness to ensure that the induced magnetic field at its boundaries is null. These simulation results for lithium film free surface flows under NSTX outboard mid-plane magnetic field configurations have shown that 3D MHD effects from a surface normal field gradient cause return currents to interact with surface normal fields and produce unfavorable MHD forces. This leads to a substantial change in flow pattern and a reduction in flow velocity, with most of the flow spilling over one side of the chute. These critical phenomena can not be revealed by 2D models. Additionally, a design which overcomes these undesired flow characteristics is obtained

  14. Empirical Modeling of Spatial 3D Flow Characteristics Using a Remote-Controlled ADCP System: Monitoring a Spring Flood

    Claude Flener

    2015-01-01

    Full Text Available The use of acoustic Doppler current profilers (ADCP for measuring streamflow and discharge is becoming increasingly widespread. The spatial distribution of flow patterns is useful data in studying riverine habitats and geomorphology. Until now, most flow mapping has focused on measurements along a series of transects in a channel. Here, we set out to measure, model and analyze the 3D flow characteristics of a natural river over a continuous areal extent, quantifying flow velocity, 3D flow directions, volumes, water depth and their changes over time. We achieved multidimensional spatial flow measurements by deploying an ADCP on a remotely-controlled boat, combined with kinematic GNSS positioning and locally-monitored water level data. We processed this data into a 3D point cloud of accurately positioned individual 3D flow measurements that allows the visual analysis of flow velocities, directions and channel morphology in 3D space. We demonstrate how this allows monitoring changes of flow patterns with a time series of flow point clouds measured over the period of a spring flood in Finnish Lapland. Furthermore, interpolating the raw point cloud onto a 3D matrix allows us to quantify volumetric flow while reducing noise in the data. We can now quantify the volumes of water moving at certain velocities in a given reach and their location in 3D space, allowing, for instance, the monitoring of the high-velocity core and its changes over time.

  15. Analytical solution of Stokes flow near corners and applications to numerical solution of Navier-Stokes equations with high precision

    Burda, P.; Novotný, Jaroslav; Šístek, Jakub

    Praha : Matematický ústav AV ČR, v.v.i, 2012 - (Brandts, J.; Chleboun, J.; Korotov, S.; Segeth, K.; Šístek, J.; Vejchodský, T.), s. 43-54 ISBN 978-80-85823-60-8. [Applications of Math ematics 2012. Prague (CZ), 02.05.2012-05.05.2012] R&D Projects: GA ČR GA106/08/0403 Institutional support: RVO:67985840 ; RVO:61388998 Keywords : Stokes flow * singularities * corners * asymptotic solution Subject RIV: BA - General Math ematics http://www. math .cas.cz/~am2012/proceedings/contributions/burda.pdf

  16. A Numerical Method for Solving the 3D Unsteady Incompressible Navier-Stokes Equations in Curvilinear Domains with Complex Immersed Boundaries.

    Ge, Liang; Sotiropoulos, Fotis

    2007-08-01

    A novel numerical method is developed that integrates boundary-conforming grids with a sharp interface, immersed boundary methodology. The method is intended for simulating internal flows containing complex, moving immersed boundaries such as those encountered in several cardiovascular applications. The background domain (e.g the empty aorta) is discretized efficiently with a curvilinear boundary-fitted mesh while the complex moving immersed boundary (say a prosthetic heart valve) is treated with the sharp-interface, hybrid Cartesian/immersed-boundary approach of Gilmanov and Sotiropoulos [1]. To facilitate the implementation of this novel modeling paradigm in complex flow simulations, an accurate and efficient numerical method is developed for solving the unsteady, incompressible Navier-Stokes equations in generalized curvilinear coordinates. The method employs a novel, fully-curvilinear staggered grid discretization approach, which does not require either the explicit evaluation of the Christoffel symbols or the discretization of all three momentum equations at cell interfaces as done in previous formulations. The equations are integrated in time using an efficient, second-order accurate fractional step methodology coupled with a Jacobian-free, Newton-Krylov solver for the momentum equations and a GMRES solver enhanced with multigrid as preconditioner for the Poisson equation. Several numerical experiments are carried out on fine computational meshes to demonstrate the accuracy and efficiency of the proposed method for standard benchmark problems as well as for unsteady, pulsatile flow through a curved, pipe bend. To demonstrate the ability of the method to simulate flows with complex, moving immersed boundaries we apply it to calculate pulsatile, physiological flow through a mechanical, bileaflet heart valve mounted in a model straight aorta with an anatomical-like triple sinus. PMID:19194533

  17. RV functional imaging: 3-D echo-derived dynamic geometry and flow field simulations.

    Pasipoularides, Ares D; Shu, Ming; Womack, Michael S; Shah, Ashish; Von Ramm, Olaf; Glower, Donald D

    2003-01-01

    We describe a novel functional imaging approach for quantitative analysis of right ventricular (RV) blood flow patterns in specific experimental animals (or humans) using real-time, three-dimensional (3-D) echocardiography (RT3D). The method is independent of the digital imaging modality used. It comprises three parts. First, a semiautomated segmentation aided by intraluminal contrast medium locates the RV endocardial surface. Second, a geometric scheme for dynamic RV chamber reconstruction applies a time interpolation procedure to the RT3D data to quantify wall geometry and motion at 400 Hz. A volumetric prism method validated the dynamic geometric reconstruction against simultaneous sonomicrometric canine measurements. Finally, the RV endocardial border motion information is used for mesh generation on a computational fluid dynamics solver to simulate development of the early RV diastolic inflow field. Boundary conditions (tessellated endocardial surface nodal velocities) for the solver are directly derived from the endocardial geometry and motion information. The new functional imaging approach may yield important kinematic information on the distribution of instantaneous velocities in the RV diastolic flow field of specific normal or diseased hearts. PMID:12388220

  18. 3D Simulation of Flow with Free Surface Based on Adaptive Octree Mesh System

    Li Shaowu; Zhuang Qian; Huang Xiaoyun; Wang Dong

    2015-01-01

    The technique of adaptive tree mesh is an effective way to reduce computational cost through automatic adjustment of cell size according to necessity. In the present study, the 2D numerical N-S solver based on the adaptive quadtree mesh system was extended to a 3D one, in which a spatially adaptive octree mesh system and multiple parti-cle level set method were adopted for the convenience to deal with the air-water-structure multiple-medium coexisting domain. The stretching process of a dumbbell was simulated and the results indicate that the meshes are well adaptable to the free surface. The collapsing process of water column impinging a circle cylinder was simulated and from the results, it can be seen that the processes of fluid splitting and merging are properly simulated. The interaction of sec-ond-order Stokes waves with a square cylinder was simulated and the obtained drag force is consistent with the result by the Morison’s wave force formula with the coefficient values of the stable drag component and the inertial force component being set as 2.54.

  19. Simulation of a 3D unsteady flow in an axial turbine stage

    Straka Petr

    2012-04-01

    Full Text Available The contribution deals with a numerical simulation of an unsteady flow in an axial turbine stage. The solution is performed using an in-house numerical code developed in the Aeronautical and Test Institute, Plc. in Prague. The numerical code is based on a finite volume discretization of governing equations (Favre averaged Navier-Stokes equations and a two-equations turbulence model. The temporal integration is based on the implicit second-order backward Euler formula, which is realized through the iteration process in dual time. The proposed numerical method is used for solution of the 3D, unsteady, viscous turbulent flow of a perfect gas in the axial turbine stage. The flow path consists of an input nozzle, stator blade-wheel, rotor blade-wheel, a shroud-seal gap and a diffuser. Attention is paid to the influence of a secondary flow structures, such as generated vortices and flow in shroud-seal gap.

  20. Intrathoracic tumour motion estimation from CT imaging using the 3D optical flow method

    Guerrero, Thomas [Division of Radiation Oncology, University of Texas M D Anderson Cancer Center, Houston, TX 77030 (United States); Zhang, Geoffrey [Division of Radiation Oncology, University of Texas M D Anderson Cancer Center, Houston, TX 77030 (United States); Huang Tzungchi [Division of Radiation Oncology, University of Texas M D Anderson Cancer Center, Houston, TX 77030 (United States); Lin Kaping [Department of Electrical Engineering, Chung-Yuan University, Taipei, Taiwan (China)

    2004-09-07

    The purpose of this work was to develop and validate an automated method for intrathoracic tumour motion estimation from breath-hold computed tomography (BH CT) imaging using the three-dimensional optical flow method (3D OFM). A modified 3D OFM algorithm provided 3D displacement vectors for each voxel which were used to map tumour voxels on expiration BH CT onto inspiration BH CT images. A thoracic phantom and simulated expiration/inspiration BH CT pairs were used for validation. The 3D OFM was applied to the measured inspiration and expiration BH CT images from one lung cancer and one oesophageal cancer patient. The resulting displacements were plotted in histogram format and analysed to provide insight regarding the tumour motion. The phantom tumour displacement was measured as 1.20 and 2.40 cm with full-width at tenth maximum (FWTM) for the distribution of displacement estimates of 0.008 and 0.006 cm, respectively. The maximum error of any single voxel's motion estimate was 1.1 mm along the z-dimension or approximately one-third of the z-dimension voxel size. The simulated BH CT pairs revealed an rms error of less than 0.25 mm. The displacement of the oesophageal tumours was nonuniform and up to 1.4 cm, this was a new finding. A lung tumour maximum displacement of 2.4 cm was found in the case evaluated. In conclusion, 3D OFM provided an accurate estimation of intrathoracic tumour motion, with estimated errors less than the voxel dimension in a simulated motion phantom study. Surprisingly, oesophageal tumour motion was large and nonuniform, with greatest motion occurring at the gastro-oesophageal junction.

  1. Intrathoracic tumour motion estimation from CT imaging using the 3D optical flow method

    Guerrero, Thomas; Zhang, Geoffrey; Huang, Tzung-Chi; Lin, Kang-Ping

    2004-09-01

    The purpose of this work was to develop and validate an automated method for intrathoracic tumour motion estimation from breath-hold computed tomography (BH CT) imaging using the three-dimensional optical flow method (3D OFM). A modified 3D OFM algorithm provided 3D displacement vectors for each voxel which were used to map tumour voxels on expiration BH CT onto inspiration BH CT images. A thoracic phantom and simulated expiration/inspiration BH CT pairs were used for validation. The 3D OFM was applied to the measured inspiration and expiration BH CT images from one lung cancer and one oesophageal cancer patient. The resulting displacements were plotted in histogram format and analysed to provide insight regarding the tumour motion. The phantom tumour displacement was measured as 1.20 and 2.40 cm with full-width at tenth maximum (FWTM) for the distribution of displacement estimates of 0.008 and 0.006 cm, respectively. The maximum error of any single voxel's motion estimate was 1.1 mm along the z-dimension or approximately one-third of the z-dimension voxel size. The simulated BH CT pairs revealed an rms error of less than 0.25 mm. The displacement of the oesophageal tumours was nonuniform and up to 1.4 cm, this was a new finding. A lung tumour maximum displacement of 2.4 cm was found in the case evaluated. In conclusion, 3D OFM provided an accurate estimation of intrathoracic tumour motion, with estimated errors less than the voxel dimension in a simulated motion phantom study. Surprisingly, oesophageal tumour motion was large and nonuniform, with greatest motion occurring at the gastro-oesophageal junction. Presented at The IASTED Second International Conference on Biomedical Engineering (BioMED 2004), Innsbruck, Austria, 16-18 February 2004.

  2. Intrathoracic tumour motion estimation from CT imaging using the 3D optical flow method

    The purpose of this work was to develop and validate an automated method for intrathoracic tumour motion estimation from breath-hold computed tomography (BH CT) imaging using the three-dimensional optical flow method (3D OFM). A modified 3D OFM algorithm provided 3D displacement vectors for each voxel which were used to map tumour voxels on expiration BH CT onto inspiration BH CT images. A thoracic phantom and simulated expiration/inspiration BH CT pairs were used for validation. The 3D OFM was applied to the measured inspiration and expiration BH CT images from one lung cancer and one oesophageal cancer patient. The resulting displacements were plotted in histogram format and analysed to provide insight regarding the tumour motion. The phantom tumour displacement was measured as 1.20 and 2.40 cm with full-width at tenth maximum (FWTM) for the distribution of displacement estimates of 0.008 and 0.006 cm, respectively. The maximum error of any single voxel's motion estimate was 1.1 mm along the z-dimension or approximately one-third of the z-dimension voxel size. The simulated BH CT pairs revealed an rms error of less than 0.25 mm. The displacement of the oesophageal tumours was nonuniform and up to 1.4 cm, this was a new finding. A lung tumour maximum displacement of 2.4 cm was found in the case evaluated. In conclusion, 3D OFM provided an accurate estimation of intrathoracic tumour motion, with estimated errors less than the voxel dimension in a simulated motion phantom study. Surprisingly, oesophageal tumour motion was large and nonuniform, with greatest motion occurring at the gastro-oesophageal junction

  3. Bifurcations and degenerate periodic points in a 3D chaotic fluid flow

    Smith, Lachlan D; Lester, Daniel R; Metcalfe, Guy

    2016-01-01

    Analysis of the periodic points of a conservative periodic dynamical system uncovers the basic kinematic structure of the transport dynamics, and identifies regions of local stability or chaos. While elliptic and hyperbolic points typically govern such behaviour in 3D systems, degenerate (parabolic) points play a more important role than expected. These points represent a bifurcation in local stability and Lagrangian topology. In this study we consider the ramifications of the two types of degenerate periodic points that occur in a model 3D fluid flow. (1) Period-tripling bifurcations occur when the local rotation angle associated with elliptic points is reversed, creating a reversal in the orientation of associated Lagrangian structures. Even though a single unstable point is created, the bifurcation in local stability has a large influence on local transport and the global arrangement of manifolds as the unstable degenerate point has three stable and three unstable directions, similar to hyperbolic points, ...

  4. Holographic measurement of wall stress distribution and 3D flow over a surface textured by microfibers

    Bocanegra, Humberto; Gorumlu, Seder; Aksak, Burak; Castillo, Luciano; Sheng, Jian

    2015-11-01

    Understanding how fluid flow interacts with micro-textured surfaces is crucial for a broad range of key biological processes and engineering applications including particle dispersion, pathogenic infections, and drag manipulation by surface topology. Existing methods, such as μPIV, suffers from low spatial resolution and fail to track tracer particle motion very close to a rough surface and within roughness elements. In this paper, we present a technique that combines high speed digital holographic microscopy (DHM) with a correlation based de-noising algorithm to overcome the optical interference generated by surface roughness and to capture a large number of 3D particle trajectories. It allows us to obtain a 3D velocity field with an uncertainty of 0.01% and 2D wall shear stress distribution at the resolution of ~ 65 μPa. Applying the technique to a microfluidics with a surface textured by microfibers, we find that the flow is three-dimensional and complex. While the microfibers affect the velocity flow field locally, their presence is felt globally in terms of wall shear stresses. The study of effect of microfiber patterns and flow characteristics on skin frictions are ongoing and will be reported.

  5. 3D numerical investigation of turbulent flow through lateral intake in open channel

    The flow at a channel bifurcation is turbulent, highly three-dimensional (3D) and has many complex features. There is transverse motion accompanying the main flow and an extensive separation zone that develops in the branch channel. This zone causes hydraulic and sedimentation problems that must be known before designing the system. This necessitates a deeper insight into the flow patterns and shear stress distributions near the solid boundaries. This paper reports a 3D numerical investigation of flow pattern and shear stress distribution at a lateral intake in an open channel. Simulations are done on rectangular channel geometry, with smooth bed and sidewalls. The CFD model uses the standard k-ε and k-ω model of Wilcox turbulence closure schemes as implemented in the FLUENT code. The simulation results were compared with available experimental data. It was found that both turbulence models used accurately predicted velocity profiles in the main channel but in the branch channel, the k-ω model is performed better than the k-ε turbulence model. (author)

  6. Surfactant-induced migration of a spherical drop in Stokes flow

    Hanna, James A.; Vlahovska, Petia M.

    2009-01-01

    In Stokes flows, symmetry considerations dictate that a neutrally-buoyant spherical particle will not migrate laterally with respect to the local flow direction. We show that a loss of symmetry due to flow-induced surfactant redistribution leads to cross-stream drift of a spherical drop in Poiseuille flow. We derive analytical expressions for the migration velocity in the limit of small non-uniformities in the surfactant distribution, corresponding to weak-flow conditions or a high-viscosity ...

  7. A continuous flow microfluidic calorimeter: 3-D numerical modeling with aqueous reactants

    Sen, Mehmet A., E-mail: mehmet.sen@mathworks.com [Northeastern University, Department of Mechanical and Industrial Engineering, 360 Hungtington Avenue, 334 Snell Engineering Center, Boston, MA 02115 (United States); Kowalski, Gregory J., E-mail: gkowal@coe.neu.edu [Northeastern University, Department of Mechanical and Industrial Engineering, 360 Hungtington Avenue, 334 Snell Engineering Center, Boston, MA 02115 (United States); Fiering, Jason, E-mail: jfiering@draper.com [Charles Stark Draper Laboratory, 555 Technology Square, Cambridge, MA 02139 (United States); Larson, Dale, E-mail: dlarson@draper.com [Charles Stark Draper Laboratory, 555 Technology Square, Cambridge, MA 02139 (United States)

    2015-03-10

    Highlights: • A co-flow microreactor is modeled in flow, reaction/diffusion, and thermal domains. • Analysis shows how arrayed temperature sensors can provide enthalpy of reaction. • Optical plasmonic temperature sensors could be arrayed suitably for calorimetry. • The reactor studied has a volume of 25 nL. - Abstract: A computational analysis of the reacting flow field, species diffusion and heat transfer processes with thermal boundary layer effects in a microchannel reactor with a coflow configuration was performed. Two parallel adjacent streams of aqueous reactants flow along a wide, shallow, enclosed channel in contact with a substrate, which is affixed to a temperature controlled plate. The Fluent computational fluid dynamics package solved the Navier–Stokes, mass transport and energy equations. The energy model, including the enthalpy of reaction as a nonuniform heat source, was validated by calculating the energy balance at several control volumes in the microchannel. Analysis reveals that the temperature is nearly uniform across the channel thickness, in the direction normal to the substrate surface; hence, measurements made by sensors at or near the surface are representative of the average temperature. Additionally, modeling the channel with a glass substrate and a silicone cover shows that heat transfer is predominantly due to the glass substrate. Finally, using the numerical results, we suggest that a microcalorimeter could be based on this configuration, and that temperature sensors such as optical nanohole array sensors could have sufficient spatial resolution to determine enthalpy of reaction.

  8. Predictions of bubbly flows in vertical pipes using two-fluid models in CFDS-FLOW3D code

    Banas, A.O.; Carver, M.B. [Chalk River Laboratories (Canada); Unrau, D. [Univ. of Toronto (Canada)

    1995-09-01

    This paper reports the results of a preliminary study exploring the performance of two sets of two-fluid closure relationships applied to the simulation of turbulent air-water bubbly upflows through vertical pipes. Predictions obtained with the default CFDS-FLOW3D model for dispersed flows were compared with the predictions of a new model (based on the work of Lee), and with the experimental data of Liu. The new model, implemented in the CFDS-FLOW3D code, included additional source terms in the {open_quotes}standard{close_quotes} {kappa}-{epsilon} transport equations for the liquid phase, as well as modified model coefficients and wall functions. All simulations were carried out in a 2-D axisymmetric format, collapsing the general multifluid framework of CFDS-FLOW3D to the two-fluid (air-water) case. The newly implemented model consistently improved predictions of radial-velocity profiles of both phases, but failed to accurately reproduce the experimental phase-distribution data. This shortcoming was traced to the neglect of anisotropic effects in the modelling of liquid-phase turbulence. In this sense, the present investigation should be considered as the first step toward the ultimate goal of developing a theoretically sound and universal CFD-type two-fluid model for bubbly flows in channels.

  9. The 3-D CFD modeling of gas turbine combustor-integral bleed flow interaction

    Chen, D. Y.; Reynolds, R. S.

    1993-01-01

    An advanced 3-D Computational Fluid Dynamics (CFD) model was developed to analyze the flow interaction between a gas turbine combustor and an integral bleed plenum. In this model, the elliptic governing equations of continuity, momentum and the k-e turbulence model were solved on a boundary-fitted, curvilinear, orthogonal grid system. The model was first validated against test data from public literature and then applied to a gas turbine combustor with integral bleed. The model predictions agreed well with data from combustor rig testing. The model predictions also indicated strong flow interaction between the combustor and the integral bleed. Integral bleed flow distribution was found to have a great effect on the pressure distribution around the gas turbine combustor.

  10. Unsteady Reynolds Averaged Navier-Stokes and Large Eddy Simulations of Flows across Staggered Tube Bundle for a VHTR Lower Plenum Design

    In this work, behavior of unsteady and oscillating flow through a typical tube bundle array are analyzed by unsteady computations: 2D unsteady Reynolds averaged Navier-Stokes (URANS) and 3D Large Eddy Simulation (LES) and the results are compared with existing experimental data. In order to confirm appropriateness and limitations of CFD applications in the Korean VHTR design, two types of unsteady computations are performed such as 2D unsteady Reynolds averaged Navier-Stokes (URANS) and 3D Large Eddy Simulation (LES) for the existing tube bundle array. The velocity component profiles are compared with the experimental data and it is concluded that the URANS with the standard k-ω model is reasonably appropriate for cost-effective VHTR lower plenum analysis. Nevertheless, if more accurate results are needed, the LES-Smagorinsky computation is recommended considering limitations in the time averaged RANS in capturing small eddies

  11. Complex 3D Blood Flow Pathways in Two Cases of Aorta to Right Heart Fistulae: a 4D Flow MRI study

    Thakrar, Darshit; Popescu, Andrada; Gupta, Suraj; de Freitas, Andrew; Russell, Hyde; Carr, James; Markl, Michael

    2013-01-01

    We present an analysis of 3D blood flow in two cases of Sinus of Valsalva to right heart fistulae based on 4D flow MRI. Despite similar underlying pathology, 3D visualization revealed intricate differences in flow patterns connecting the systemic and pulmonary circulation. The cases illustrates the potential of 4D flow MRI to complement the evaluation of complex structural heart disease by assessing complex flow dynamics and providing quantitative information of flow ratios and flow rates.

  12. Matching-index-of-refraction of transparent 3D printing models for flow visualization

    Song, Min Seop; Choi, Hae Yoon; Seong, Jee Hyun; Kim, Eung Soo, E-mail: kes7741@snu.ac.kr

    2015-04-01

    Matching-index-of-refraction (MIR) has been used for obtaining high-quality flow visualization data for the fundamental nuclear thermal-hydraulic researches. By this method, distortions of the optical measurements such as PIV and LDV have been successfully minimized using various combinations of the model materials and the working fluids. This study investigated a novel 3D printing technology for manufacturing models and an oil-based working fluid for matching the refractive indices. Transparent test samples were fabricated by various rapid prototyping methods including selective layer sintering (SLS), stereolithography (SLA), and vacuum casting. As a result, the SLA direct 3D printing was evaluated to be the most suitable for flow visualization considering manufacturability, transparency, and refractive index. In order to match the refractive indices of the 3D printing models, a working fluid was developed based on the mixture of herb essential oils, which exhibit high refractive index, high transparency, high density, low viscosity, low toxicity, and low price. The refractive index and viscosity of the working fluid range 1.453–1.555 and 2.37–6.94 cP, respectively. In order to validate the MIR method, a simple test using a twisted prism made by the SLA technique and the oil mixture (anise and light mineral oil) was conducted. The experimental results show that the MIR can be successfully achieved at the refractive index of 1.51, and the proposed MIR method is expected to be widely used for flow visualization studies and CFD validation for the nuclear thermal-hydraulic researches.

  13. Matching-index-of-refraction of transparent 3D printing models for flow visualization

    Matching-index-of-refraction (MIR) has been used for obtaining high-quality flow visualization data for the fundamental nuclear thermal-hydraulic researches. By this method, distortions of the optical measurements such as PIV and LDV have been successfully minimized using various combinations of the model materials and the working fluids. This study investigated a novel 3D printing technology for manufacturing models and an oil-based working fluid for matching the refractive indices. Transparent test samples were fabricated by various rapid prototyping methods including selective layer sintering (SLS), stereolithography (SLA), and vacuum casting. As a result, the SLA direct 3D printing was evaluated to be the most suitable for flow visualization considering manufacturability, transparency, and refractive index. In order to match the refractive indices of the 3D printing models, a working fluid was developed based on the mixture of herb essential oils, which exhibit high refractive index, high transparency, high density, low viscosity, low toxicity, and low price. The refractive index and viscosity of the working fluid range 1.453–1.555 and 2.37–6.94 cP, respectively. In order to validate the MIR method, a simple test using a twisted prism made by the SLA technique and the oil mixture (anise and light mineral oil) was conducted. The experimental results show that the MIR can be successfully achieved at the refractive index of 1.51, and the proposed MIR method is expected to be widely used for flow visualization studies and CFD validation for the nuclear thermal-hydraulic researches

  14. Regional cerebral blood flow in pure dysarthria. A 3D-SSP study

    Pure dysarthria from brain infarction is a rare condition, and its pathophysiology remains unclear. To clarify the underlying mechanism of pure dysarthria, we investigated the lesion sites and regional cerebral blood flow in patients with pure dysarthria. We examined 18 consecutive patients with pure dysarthria (9 men and 9 women; mean age, 71 years) who underwent MRI and cerebral blood flow studies. To visualize the regional cerebral blood flow, we generated Z score images using the three-dimensional stereotactic surface projection (3D-SSP) method with single-photon emission computed tomography (SPECT) and N-isopropyl-p [123I]iodoamphetamine. Data on the brain surface perfusion extracted by the 3D-SSP analysis were compared between the pure dysarthria (PD) patients and 9 control subjects. MRI revealed multiple lacunar infarctions involving the internal capsule and/or corona radiata in 11 patients, left internal capsule-corona radiata infarction in 4 patients, and pontine infarction in 3 patients. SPECT with 3D-SSP demonstrated bilateral frontal cortical hypoperfusion in all patients, particularly in the anterior opercular region. Based on intergroup comparisons, the PD group exhibited pronounced cortical hypoperfusion in the opercular and medial frontal regions, left more than right. In conclusion, pure dysarthria is considered to originate from frontal cortical hypoperfusion, mainly in the anterior opercular and medial frontal regions, which is probably due to interruption of the corticosubcortical neural networks relevant to speech expression and articulation. In addition, it is suggested that left hemispheric lesions may make a greater contribution to the development of pure dysarthria than do right ones. (author)

  15. Influence of Underhood Flow on Engine Cooling Using 1-D And 3-D Approach

    Bolehovský Ondřej

    2015-12-01

    Full Text Available This work deals with numerical simulation of complete cooling system of internal combustion engine (GT-SUITE, which also involves the simulation of flow in underhood using the computationally undemanding simulation. A detailed model of the internal combustion engine is extended to a cooling circuit model which is then coupled to a simplified underhood model which is created with the help of GT-COOL application as a 3-D model and afterwards transferred to a 1-D form. The approaches, one using 1-D solution of arrangement of the heat exchangers and the other 3-D approach using the underhood model, were investigated in two steady states corresponding to various vehicle speeds and engine load. These simulations have shown the inappropriateness of 1-D approach when solving the flow in the heat exchangers in the underhood and helped to explore a relatively undemanding method of flow simulation in the underhood, which enables to detect the interaction between the models of the cooling system and the internal combustion engine and the issue of arrangement of the heat exchangers in the underhood.

  16. 3D Numerical Simulation of Overbank Flow in Non-Orthogonal Curvilinear Coordinates

    ZHANG Ming-liang; SHEN Yong-ming; WU Xiu-guang

    2005-01-01

    The velocity field in meandering compound channels with overbank flow is highly three dimensional. To date, its features have been investigated experimentally and little research has been undertaken to investigate the feasibility of reproducing these velocity fields with computer models. If computer modeling were to prove successful in this context, it could become a useful prediction technique and research tool to enhance our understanding of natural river dynamics. A 3-D k-ε turbulence hydrodynamic model in curvilinear coordinates is established to simulate the overbank flow. The body-fitted coordinate is adopted in the horizontal plane, the part grid is adopted in the vertical direction, and the wall-function method is employed to simulate the bed resistance. The model is applied to the simulation of the meandering channel with straight flood plain banks, and the main velocities and secondary velocities for both the longitudinal and cross sections are presented. Comparison and analysis show that the results of simulation are fit to reflect the results of experiment. These results show the application value of the model to 3D overbank flow.

  17. Vascular centerline extraction in 3D MR angiograms for phase contrast MRI blood flow measurement

    Hernandez Hoyos, M. [CREATIS, CNRS 5515 et INSERM U630 Research Unit, INSA de Lyon, 69 - Villeurbanne (France); Universidad de los Andes, Bogota (Colombia). Grupo Imagine, Grupo de Ingenieria Biomedica; Orlowski, P.; Piatkowska-Janko, E.; Bogorodzki, P. [Warsaw Univ. of Tech. (Poland). ZEJM-BINSK, Inst. of Radioelectronics; Orkisz, M. [CREATIS, CNRS 5515 et INSERM U630 Research Unit, INSA de Lyon, 69 - Villeurbanne (France)

    2006-03-15

    The accuracy of 2D phase contrast (PC) magnetic resonance angiography (MRA) depends on the alignment between the vessels and the imaging plane. PC MRA imaging of blood flow is challenging when the flow in several vessels is to be evaluated with one acquisition. For this purpose, semi-automatic determination of the plane most perpendicular to several vessels is proposed based on centerlines extracted from 3D MRA. Arterial centerlines are extracted from 3D MRA based on iterative estimation-prediction, multi-scale analysis of image moments, and a second-order shape model. The optimal plane is determined by minimizing misalignment between its normal vector and the centerlines' tangent vectors. The method was evaluated on a phantom and on 35 patients, by seeking the optimal plane for cerebral blood flow quantification simultaneously in internal carotids and vertebral arteries. In the phantom, difference of orientation and of height between known and calculated planes was 1.2 and 2.5 mm, respectively. In the patients, all but one centerline were correctly extracted and the misalignment of the plane was within 12 per artery. Semi-automatic centerline extraction simplifies and automates determination of the plane orthogonal to one vessel, thereby permitting automatic simultaneous minimization of the misalignment with several vessels in PC MRA. (orig.)

  18. Vascular centerline extraction in 3D MR angiograms for phase contrast MRI blood flow measurement

    The accuracy of 2D phase contrast (PC) magnetic resonance angiography (MRA) depends on the alignment between the vessels and the imaging plane. PC MRA imaging of blood flow is challenging when the flow in several vessels is to be evaluated with one acquisition. For this purpose, semi-automatic determination of the plane most perpendicular to several vessels is proposed based on centerlines extracted from 3D MRA. Arterial centerlines are extracted from 3D MRA based on iterative estimation-prediction, multi-scale analysis of image moments, and a second-order shape model. The optimal plane is determined by minimizing misalignment between its normal vector and the centerlines' tangent vectors. The method was evaluated on a phantom and on 35 patients, by seeking the optimal plane for cerebral blood flow quantification simultaneously in internal carotids and vertebral arteries. In the phantom, difference of orientation and of height between known and calculated planes was 1.2 and 2.5 mm, respectively. In the patients, all but one centerline were correctly extracted and the misalignment of the plane was within 12 per artery. Semi-automatic centerline extraction simplifies and automates determination of the plane orthogonal to one vessel, thereby permitting automatic simultaneous minimization of the misalignment with several vessels in PC MRA. (orig.)

  19. Quasi 3D refined simulation of flow and pollutant transport in a meandering River Reach

    Li-ren Yu

    2013-03-01

    Full Text Available This paper reports a quasi 3D numerical simulation in a meandering river reach of the Yellow River, aiming to develop a tool for modeling turbulent flows and pollutant transport in complex natural waters. The recently built depth-averaged two-equation turbulence model, together with and models, were used to close non-simplified quasi 3D hydrodynamic fundamental governing equations. The discretized equations were solved by advanced multi-grid iterative method under non-orthogonal body-fitted coarse and fine two-levels’ grids with collocated variable arrangement. Except for steady flow and transport computation, the processes of contaminant inpouring and plume development, caused by the side-discharge from a tribytary, also have been investigated numerically. The used three closure approaches are suitable for modeling strong mixing turbulence. The established model with higher order of magnitude of transported variable provides a possibility to elevate the computational precision. Based on the developed mathematical model, a CFD (Computational Fluid Dynamics software, namely Q3drm1.0, was developed. This numerical tool focuses on the refined simulations of the steady and unsteady problems of flow and temperature/contaminant transports in complicated computational domains with the strong ability to deal with different discharge situations: side-discharge, point-source discharge/point-sink, and area-source discharge from the slope along bank. In this article, the study of side-discharge is presented only.

  20. PIV measurement of the flow field in a domestic refrigerator model: Comparison with 3D simulations

    Ben Amara, S.; Laguerre, O.; Flick, D. [UMR Genie Industriel Alimentaire (Cemagref-AgroParisTech-INRA) - Cemagref, Parc de Tourvoie, BP 44, 92185 Antony Cedex (France); Charrier-Mojtabi, M.-C.; Lartigue, B. [Universite Paul Sabatier, Laboratoire PHASE, E.A. 3208, 118 route de Narbonne, 31062 Toulouse Cedex 4 (France)

    2008-12-15

    PIV (particle image velocimetry) measurements of flow field due to natural convection in a parallelepipedic enclosure representing a domestic refrigerator model (scale 1) have been undertaken in order to determine the thickness of the hydrodynamic boundary layers and to study the flow motions depending on the boundary conditions applied on the vertical walls. One of the vertical walls is maintained at a negative and constant temperature either on the totality or on one part of its surface: this wall acts as the evaporator. The other walls are in contact with external air at constant temperature. The velocity measurements have been made in the symmetry plane of the enclosure. Unsteady recirculations have been observed at the bottom of the cavity. The influence of both the temperature and the dimension of the cold wall has been studied. Numerical simulations using CFD software (Fluent) have been then performed. In the numerical model, we assumed that the temperature of the evaporator is constant while an uniform global heat transfer coefficient has been used to describe the heat exchange with the external air at constant temperature. We considered laminar 3D flows and took into account the heat transfer by radiation between the different walls of the cavity. The results obtained with the 3D numerical simulations are in quite good agreement with the experimental airflow measurements using the PIV technique. (author)

  1. Simulation of the 3D viscoelastic free surface flow by a parallel corrected particle scheme

    Jin-Lian, Ren; Tao, Jiang

    2016-02-01

    In this work, the behavior of the three-dimensional (3D) jet coiling based on the viscoelastic Oldroyd-B model is investigated by a corrected particle scheme, which is named the smoothed particle hydrodynamics with corrected symmetric kernel gradient and shifting particle technique (SPH_CS_SP) method. The accuracy and stability of SPH_CS_SP method is first tested by solving Poiseuille flow and Taylor-Green flow. Then the capacity for the SPH_CS_SP method to solve the viscoelastic fluid is verified by the polymer flow through a periodic array of cylinders. Moreover, the convergence of the SPH_CS_SP method is also investigated. Finally, the proposed method is further applied to the 3D viscoelastic jet coiling problem, and the influences of macroscopic parameters on the jet coiling are discussed. The numerical results show that the SPH_CS_SP method has higher accuracy and better stability than the traditional SPH method and other corrected SPH method, and can improve the tensile instability. Project supported by the Natural Science Foundation of Jiangsu Province, China (Grant Nos. BK20130436 and BK20150436) and the Natural Science Foundation of the Higher Education Institutions of Jiangsu Province, China (Grant No. 15KJB110025).

  2. Pipe Flow and Wall Turbulence Using a Modified Navier-Stokes Equation

    L. Jirkovsky; A. Muriel

    2012-01-01

    We use a derived incompressible modified Navier-Stokes equation to model pipe flow and wall turbulence. We reproduce the observed flattened paraboloid velocity profiles of turbulence that cannot be obtained directly using standard incompressible Navier-Stokes equation. The solutions found are in harmony with multi-valued velocity fields as a definition of turbulence. Repeating the procedure for the flow of turbulent fluid between two parallel flat plates we find similar flattened velocity profiles. We extend the analysis to the turbulent flow along a single wall and compare the results with experimental data and the established controversial yon Karman logarithmic law of the wall.

  3. On the Modelling of Steady Generalized Newtonian Flows in a 3D Coronary Bypass

    Vimmr, Jan; Jonášová, Alena

    2008-01-01

    Blood's non-Newtonian behaviour is investigated in an idealized coronary 3D bypass model, which includes both the proximal and distal parts of the occluded native artery and the connected end-to-side bypass graft. Considering the blood to be a generalized Newtonian fluid, the shear-dependent viscosity is given by two well-known macroscopic non-Newtonian models (the Carreau-Yasuda model and the modified Cross model). Both non-Newtonian steady flow fields are analyzed with regard to the bypass ...

  4. Quantification of smoothing requirement for 3D optic flow calculation of volumetric images

    Bab-Hadiashar, Alireza; Tennakoon, Ruwan B.; de Bruijne, Marleen

    2013-01-01

    Complexities of dynamic volumetric imaging challenge the available computer vision techniques on a number of different fronts. This paper examines the relationship between the estimation accuracy and required amount of smoothness for a general solution from a robust statistics perspective. We show...... that a (surprisingly) small amount of local smoothing is required to satisfy both the necessary and sufficient conditions for accurate optic flow estimation. This notion is called 'just enough' smoothing, and its proper implementation has a profound effect on the preservation of local information in processing 3D...

  5. Rotary slanted single wire CTA - a useful tool for 3D flows investigations

    Jonáš, P.

    2013-04-01

    The procedure is described of experimental investigation of a statistically stationary generally nonisothermal 3D flow by means of a constant temperature anemometer (CTA) using single slanted heated wire, rotary round the fixed axis. The principle of this procedure is quite clear. The change of the heated wire temperature modifies ratio of CTA sensitivities to temperature and velocity fluctuations. Turning the heated wire through a proper angle changes the sensitivity to components of the instantaneous velocity vector. Some recommendations are presented based on long time experiences, e.g. on the choice of probe, on the probe calibration, to the measurement organization and to the evaluation of results.

  6. Rotary slanted single wire CTA – a useful tool for 3D flows investigations

    Jonáš P.

    2013-04-01

    Full Text Available The procedure is described of experimental investigation of a statistically stationary generally nonisothermal 3D flow by means of a constant temperature anemometer (CTA using single slanted heated wire, rotary round the fixed axis. The principle of this procedure is quite clear. The change of the heated wire temperature modifies ratio of CTA sensitivities to temperature and velocity fluctuations. Turning the heated wire through a proper angle changes the sensitivity to components of the instantaneous velocity vector. Some recommendations are presented based on long time experiences, e.g. on the choice of probe, on the probe calibration, to the measurement organization and to the evaluation of results.

  7. 3-D slug flow heat transfer analysis of coupled coolant cells in finite LMFBR bundles

    A three-dimensional single region slug flow heat transfer analysis for finite LMFBR rod bundles using a classical analytical solution method has been performed. According to the isolated single cell analysis, the results show that the peripheral clad temperature variation as well as the thermal entrance length are strongly dependent upon the degree of irregularity displayed by various coolant geometries. Since under the present LMFBR conditions, fully-developed temperature fields may hardly be established in such characteristic rod bundle regions, a 3-D heat transfer analysis seems to be mandatory. This implies that the results of fully developed heat transfer analyses are by far too conservative

  8. Numerical Investigation of Nozzle Geometry Effect on Turbulent 3-D Water Offset Jet Flows

    Negar Mohammad Aliha

    2016-01-01

    Full Text Available Using the Yang-Shih low Reynolds k-ε turbulence model, the mean flow field of a turbulent offset jet issuing from a long circular pipe was numerically investigated. The experimental results were used to verify the numerical results such as decay rate of streamwise velocity, locus of maximum streamwise velocity, jet half width in the wall normal and lateral directions, and jet velocity profiles. The present study focused attention on the influence of nozzle geometry on the evolution of a 3D incompressible turbulent offset jet. Circular, square-shaped, and rectangular nozzles were considered here. A comparison between the mean flow characteristics of offset jets issuing from circular and square-shaped nozzles, which had equal area and mean exit velocity, were made numerically. Moreover, the effect of aspect ratio of rectangular nozzles on the main features of the flow was investigated. It was shown that the spread rate, flow entrainment, and mixing rate of an offset jet issuing from circular nozzle are lower than square-shaped one. In addition, it was demonstrated that the aspect ratio of the rectangular nozzles only affects the mean flow field of the offset jet in the near field (up to 15 times greater than equivalent diameter of the nozzles. Furthermore, other parameters including the wall shear stress, flow entrainment and the length of potential core were also investigated.

  9. Method of internal 3D flow field numerical simulation for hydrodynamic torque converter

    Tao SHANG; Dingxuan ZHAO; Yuankun ZHANG; Xiangen GUO; Xiangzhong SHI

    2008-01-01

    To enhance the performance of a hydrody-namic torque converter and thoroughly understand the trait of inside flow, a numerical simulation method of internal 3D flow for the three-element centrifugal hydrodynamic torque converter was systematically researched and expatiated in this paper. First, the internal flow field of each impeller was calculated. The curves that illustrate the relationships between the pressure differences of the inlet and outlet versus flux were drawn. Second, the concurrent working point of each impeller was approximately estimated. Finally, a calculation was performed considering the influence on each impeller. The flow field of a working point was solved by multiple calculations and the actual working condition was gradually determined. The pressure and velocity distributions of the flow field were proposed. The performance parameters of the hydrodynamic torque converter were predicted. The calculation method, and the proposed pressure and velocity distribution of the flow field, have practical significance for the design and improvement of a hydrodynamic torque converter.

  10. Analytical solution of rotationally symmetric Stokes flow near corners

    Burda, P.; Novotný, Jaroslav; Šístek, Jakub

    Praha : Matematický ústav AV ČR, v.v.i, 2013 - (Brandts, S.; Korotov, S.; Křížek, M.; Šístek, J.; Vejchodský, T.), s. 13-20 ISBN 978-80-85823-61-5. [Applications of Math ematics 2013. Prague (CZ), 15.05.2013-18.05.2013] Institutional support: RVO:67985840 ; RVO:61388998 Keywords : Stokes problem * rotationally symmetric domains Subject RIV: BA - General Math ematics http://www. math .cas.cz/~am2013/proceedings/contributions/burda.pdf