bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical and experimental study of driven flow in a polar cavity
Authors: Fuchs L. , Tillmark N. 
Published: August 2005

AbstractA numerical and an experimental study of the flow of an incompressible fluid in a polar cavity is presented. The experiments included flow visualization, in two perpendicular planes, and quantitative measurements of the velocity field by a laser Doppler anemometer. Measurements were done for two ranges of Reynolds numbers; about 60 and about 350. The stream function‐vorticity form of the governing equations was approximated by upwind or central finite‐differences. Both types of finite‐difference approximations were solved by a multi‐grid method. Numerical solutions were computed on a sequence of grids and the relative accuracy of the solutions was studied. Our most accurate numerical solutions had an estimated error of 0.1 per cent and 1 per cent for Re = 60 and Re = 350, respectively. It was also noted that the solution to the second order finite difference equations was more accurate, compared to the solution to the first order equations, only if fine enough meshes were used. The possibility of using extrapolations to improve accuracy was also considered. Extrapolated solutions were found to be valid only if solutions computed on fine enough meshes were used. The numerical and the experimental results were found to be in very good agreement.
A method for predicting unsteady potential flow about an aerofoil
Authors: Vezza M. , Galbraith R. A. McD. 
Published: August 2005

AbstractA new model is presented for the calculation of the incompressible, inviscid flow around an arbitrary aerofoil undergoing unsteady motion. The technique was developed from the steady flow algorithm of Leishman and Galbraith1 in which use was made of a linear distribution of panel vorticity. The procedure is in the same class as that of Basu and Hancock2 but, because of the particular approach to the manner of specifying the shed vorticity, only a set of linear simultaneous equations needs be solved, unlike the method of Reference 2, complicated by the necessary solution of a quadratic.A brief history of unsteady flow modelling is given in the introduction, followed by the mathematical details of the current method. Results are presented and discussed for a number of cases which clearly illustrate relevant characteristics of unsteady flow.
Finite element analysis of incompressible laminar boundary layer flows
Authors: Kim Sang‐Wook , Payne F. R. 
Published: August 2005

AbstractA numerical procedure was developed to solve the two‐dimensional and axisymmetric incompressible laminar boundary layer equations using the semi‐discrete Galerkin finite element method. Linear Lagrangian, quadratic Lagrangian, and cubic Hermite interpolating polynomials were used for the finite element discretization; the first‐order, the second‐order backward difference approximation, and the Crank‐Nicolson method were used for the system of non‐linear ordinary differential equations; the Picard iteration and the Newton‐Raphson technique were used to solve the resulting non‐linear algebraic system of equations. Conservation of mass is treated as a constraint condition in the procedure; hence, it is integrated numerically along the solution line while marching along the time‐like co‐ordinate. Among the numerical schemes tested, the Picard iteration technique used with the quadratic Lagrangian polynomials and the second‐order backward difference approximation case turned out to be the most efficient to achieve the same accuracy. The advantages of the method developed lie in its coarse grid accuracy, global computational efficiency, and wide applicability to most situations that may arise in incompressible laminar boundary layer flows.
Added mass for fluid‐structure vibration problems
Authors: Jennings Alan 
Published: August 2005

AbstractThe problem of computing the vibration modes of a structure vibrating in a fluid is examined with specific application to ship hulls. In particular, methods which take proper account of the three‐dimensional nature of the water movements are described. Fluid singularities involving either a line doublet on the intersection of the water surface with the plane of symmetry or distributed sources on retracted boundaries are particularly effective at modelling the fluid flow and appear to give better numerical efficiencies than finite element or boundary element methods. The effects of the extra coefficients in the mass matrix arising from added mass on the various methods of eigensolution are discussed.
A coupled solution of the vorticity–velocity formulation of the incompressible Navier–Stokes equations
Authors: Farouk Bakhtier , Fusegi Toru 
Published: August 2005

AbstractA relatively novel formulation of the Navier‐Stokes equations is used for obtaining solutions of two dimensional incompressible fluid flow and convective heat transfer problems. A vorticity transport equation along with two Poisson equations for the velocity components and the energy equation are solved by a finite difference scheme. A coupled solution procedure is used for solving simultaneously the dependent variables along a line, using a block tridiagonal matrix algorithm. The formulation is found to be stable and has features that may be desirable for solving a wide variety of flow and heat transfer problems.
A three‐dimensional simulation of wind flow around buildings
Authors: Hanson T. , Summers D. M. , Wilson C. B. 
Published: August 2005

AbstractThe steady Navier–Stokes equation is solved to simulate the wind‐flow environment of three‐dimensional configurations of buildings. The method assumes an incident wind described by a power‐law velocity profile. A new method for controlling the two‐part nested solution iteration is introduced. The simulation is compared to some published wind‐tunnel measurements.
Numerical solution of the St. Venant equations with the MacCormack finite‐difference scheme
Authors: Garcia Reinaldo , Kahawita Rene A. 
Published: August 2005

AbstractThis paper describes the use of the MacCormack explicit time‐spilitting scheme in the development of a two‐dimensional (in plan) hydraulic simulation model that solves the St. Venant equations. Various tests devised to assess the performance of the method have been performed and the results are reported.Finally, two industrial applications of the model are presented. The method has been found to be computationally efficient and warrants further development.
An efficient algorithm for solving the incompressible fluid flow equations
Authors: Theodossiou V. M. , Sousa A. C. M. 
Published: August 2005

AbstractThe present paper reports on a modified pressure implicit predictor corrector type scheme for solving the flow governing equations, in which a consistent formulation is combined with a multi‐grid solver for the pressure correction. In addition a parabolic sublayer (PSL) approach for the treatment of the flow in the vicinity of solid walls is critically evaluated in terms of accuracy and computational efficiency. The lid‐driven cavity flow is chosen as the test case and results are presented for Reynolds numbers ranging from 100 to 1000. Predictions with the proposed scheme indicate substantial computational savings and fairly good agreement when compared with previous work. The PSL approach reduces the computing time, but with increasing Reynolds numbers the accuracy of the solutions tends to deteriorate.
Magnetohydrodynamic flow in an infinite channel
Authors: Sezgin Münevver 
Published: August 2005

AbstractThe magnetohydrodynamic (MHD) flow of an incompressible, viscous, electrically conducting fluid in an infinite channel, under an applied magnetic field has been investigated. The MHD flow between two parallel walls is of considerable practical importance because of the utility of induction flowmeters. The walls of the channel are taken perpendicular to the magnetic field and one of them is insulated, the other is partly insulated, partly conducting. An analytical solution has been developed for the velocity field and magnetic field by reducing the problem to the solution of a Fredholm integral equation of the second kind, which has been solved numerically. Solutions have been obtained for Hartmann numbers M up to 200. All the infinite integrals obtained are transformed to finite integrals which contain modified Bessel functions of the second kind. So, the difficulties associated with the computation of infinite integrals with oscillating integrands which arise for large M have been avoided. It is found that, as M increases, boundary layers are formed near the nonconducting boundaries and in the interface region for both velocity and magnetic fields, and a stagnant region in front of the conducting boundary is developed for the velocity field. Selected graphs are given showing these behaviours.
A boundary collocation method for the solution of a flow problem in a complex three‐dimensional porous medium
Authors: Levin D. , Tal A. 
Published: August 2005

AbstractA flow problem in a complex three‐dimensional domain with a free surface and mixed‐type boundary conditions is solved by the boundary collocation method. The solution is expressed as a combination of source functions distributed all around the domain close to the boundary, plus a special basis function to take care of a corner singularity. The resulting procedure is compared with the boundary integral elements method and is found to be simpler and more flexible to implement and faster to compute.
Numerical solution of the transport equation for passive contaminants in three‐dimensional complex terrains
Authors: Glekas J. , Bergeles G. , Athanassiadis N. 
Published: August 2005

AbstractThis paper presents a numerical solution of the transport equation for heat and species in complex three‐dimensional spaces. The solution domain of the equation is transformed into a cube, as also is the governing equation; the resultant equation is solved in the transformed space via a finite difference technique. The validity of the developed computer code is tested by predicting test cases for which either analytical or reliable experimental results exist. Results are also presented for the rate of convergence of the method and the computer storage requirements, from which the validity, the flexibility and the economy of the developed method are proved for flows in real three‐dimensional complex terrains.
The consistent Galerkin FEM for computing derived boundary quantities in thermal and or fluids problems
Authors: Gresho Philip M. , Lee Robert L. , Sani Robert L. , Maslanik Miriam K. , Eaton Brian E. 
Published: August 2005

AbstractA consistent, accurate and reasonably simple method of obtaining derived quantities when the conventional Galerkin finite element method (GFEM) is used to obtain the primary quantities is defined and demonstrated, both theoretically and numerically.
Application of the centre implicit method for investigation of pressure transients in pipelines
Authors: Tan J. K. , Ng K. C. , Nathan G. K. 
Published: August 2005

AbstractThis paper investigates the application of the centre implicit method for the determination of the pressure transient in a pipeline, and compares the results with those obtained using the method of characteristics and an experimental investigation. The study shows that there are unique values for the stability criterion (ratio of the linear and time increments) and the artificial viscosity term (a damping factor) used in the numerical computation. The time step and the number of nodes required for the accuracy of the method have been considered. The centre implicit method can be readily adapted to transient flow with variable wave speed provided the established conditions are used.
Periodic solutions of rigid body–viscous flow interaction
Authors: Pattani P. G. , Olson M. D. 
Published: August 2005

AbstractThis paper describes the work on extending the finite element method to cover interactions between a viscous flow and a moving body. The problem configuration of interest is that of an arbitrarily shaped body undergoing a simple harmonic motion in an otherwise undisturbed incompressible fluid. The finite element modelling is based on a primitive variables representation of the Navier‐Stokes equations using curved isoparametric elements. The non‐linear boundary conditions on the moving body are obtained using Taylor series expansion to approximate the velocities at the fixed finite element grid points. The method of averaging is used to analyse the resulting periodic motion of the fluid. The stability of the periodic solutions is studied by introducing small perturbations and applying Floquet theory. Numerical results are obtained for several example body shapes and compared with published experimental results. Good agreement is obtained for the basic non‐linear phenomenon of steady streaming.
Three‐dimensional hydrodynamics on finite elements. Part I: Linearized harmonic model
Authors: Lynch Daniel R. , Werner Francisco E. 
Published: August 2005

AbstractThe linearized three‐dimensional hydrodynamic equations are solved numerically for periodic motions, subject to a linear slip condition at the bottom. The structure of the linearized equations allows an exact uncoupling of the horizontal and vertical computations, so that they may be achieved sequentially rather than simultaneously, and without iteration. The solution strategy involves simple horizontal C° finite elements for the description of free surface elevation. Vertical variations in velocity may be treated analytically for some special variations of viscosity with depth; more generally the finite element method is employed with one‐dimensional linear elements. Because of the uncoupling, the entire three‐dimensional solution scales as a two‐dimensional vertically averaged problem. The limiting two‐dimensional problem may be solved as a Helmholtz‐type problem for elevation alone, using established techniques.Solutions for test problems are compared with known analytic solutions. Some simple gridding rules are established for the vertical discretization. Finally, a field application is shown involving the tidal response of the Lake Maracaibo (Venezuela) system.
Fast finite difference solution for steady‐state Navier‐Stokes equations using the BID method
Authors: Mittal R. C. , Sharma P. K. 
Published: August 2005

AbstractA first biharmonic boundary value problem is obtained by combining the coupled steady‐state Navier‐Stokes equations in their stream‐function‐vorticity formulation. This biharmonic boundary value problem is solved by a fast biharmonic solver developed by the authors wherein the idea of preconditioned conjugate gradient method is used. The biharmonic driver (BID) method using this solver has been found fast converging, and produces accurate results up to moderately large Reynolds numbers. Also, the mesh size does not affect the convergence rate.
Computer simulation of turbulence in internal combustion engines
Authors: Shah P. , Markatos N. C. 
Published: August 2005

AbstractThe paper presents two‐ and three‐dimensional computations of the in‐cylinder turbulent flow in a diesel engine. The mathematical formulation is presented first, with emphasis on the modifications made to the standard k‐ε model of turbulence, to account for rapid compression/expansion, and on the k‐w model also used in the computations. Then, the results of two‐and three‐dimensional transient calculations are presented and compared with experimental data. It is realized that two‐dimensional computations may be of little value to real engines, which would probably require three‐dimensional analyses. However, two‐dimensional studies are still useful in allowing the testing of new ideas easily and economically. It is concluded that the standard k‐ε model may lead to poor predictions when used for internal combustion (IC) engine simulations, and that the modified model leads to more reasonable length‐scale distributions, and it improves significantly the overall agreement of velocity predictions with experiment. The effect of the k‐ε modification is apparent in both the two‐ and three‐dimensional simulations. It is also demonstrated that the k‐w model provides better turbulence predictions than the unmodified k‐ε model, for the cases considered, and that a similar modification of the k‐w model, to account for rapid compression/expansion, might improve its predictions even further.
Recent progress in the development and understanding of SUPG methods with special reference to the compressible Euler and Navier‐Stokes equations
Authors: Hughes Thomas J. R. 
Published: August 2005

AbstractSUPG methods were originally developed for the scalar advection‐diffusion equation and the incompressible Navier‐Stokes equations. In the last few years successful extensions have been made to symmetric advective‐diffusive systems and, in particular, the compressible Euler and Navier‐Stokes equations. New procedures have been introduced to improve resolution of discontinuities and thin layers. In this paper a brief overview is presented of recent progress in the development and understanding of SUPG methods.
Forces on oscillating bodies in viscous fluid
Authors: Pattani P. G. , Olson M. D. 
Published: August 2005

AbstractThis paper describes a method for determining the fluid forces on oscillating bodies in viscous fluid when the corresponding flow problem has been solved using the finite element method. These forces are characterized by the concept of added mass, added damping and added force. Numerical results are obtained for several example body shapes. Comparison is made with exact analytical results and other finite element results for the limiting cases of Stoke's flow and inviscid flow, and good agreement is obtained. The results for finite values of the body amplitude parameter β show the appearance of added force from the steady streaming component of the flow for asymmetric bodies. Results are also obtained for the associated flow where the fluid remote from a fixed body is oscillating.
Some fast 3D finite element solvers for the generalized Stokes problem
Authors: Cahouet J. , Chabard J.‐P. 
Published: August 2005

AbstractThis paper is devoted to a comparison of various iterative solvers for the Stokes problem, based on the preconditioned Uzawa approach. In the first section the basic equations and general results of gradient‐like methods are recalled. Then a new class of preconditioners, whose optimality will be shown, is introduced. In the last section numerical experiments and comparisons with multigrid methods prove the quality of these schemes, whose discretization is detailed.
Space conservation law in finite volume calculations of fluid flow
Authors: Demirdžić I. , Perić M. 
Published: August 2005

AbstractIn the numerical solutions of fluid flow problems in moving co‐ordinates, an additional conservation equation, namely the space conservation law, has to be solved simultaneously with the mass, momentum and energy conservation equations. In this paper a method of incorporating the space conservation law into a finite volume procedure is proposed and applied to a number of test cases. The results show that the method is efficient and produces accurate results for all grid velocities and time steps for which temporal accuracy suffices. It is also demonstrated, by analysis and test calculations, that not satisfying the space conservation law in a numerical solution procedure introduces errors in the form of artificial mass sources. These errors can be made negligible only by choosing a sufficiently small time step, which sometimes may be smaller than required by the temporal discretization accuracy.
The stability of spectral schemes for the large eddy simulation of channel flows
Authors: Leslie D. C. , Gao S. 
Published: August 2005

AbstractIn a spectral LES code it is not possible to treat the actual eddy viscosity implicitly. We have therefore examined the effect on stability of adding a constant pseudo‐viscosity to the implicit term and subtracting it from the explicit term: stability limits have been derived theoretically and verified computationally for two different treatments of the explicit term. We have also studied the effect of a stochastic temporal variation of the eddy viscosity.
Onset of transition in boundary layers
Authors: Herbert Thorwald 
Published: August 2005

AbstractLaminar‐turbulent transition in boundary layers involves a cascade of weak and strong instabilities. In the model considered here the first instability occurs with respect to two‐dimensional TS waves and causes streamwise, nearly periodic concentrations of vorticity. Linear stability analysis of this periodic flow leads to Floquet systems of equations. These systems support different classes of three‐dimensional disturbances which may initiate different routes to transition. Numerical solutions by use of accurate spectral methods reveal the spectrum of eigenmodes, growth rates and disturbance velocities. The characteristics of this secondary instability are in good agreement with results of experiments and computer simulations of transition. Non‐linear self‐interaction of the rapidly growing three‐dimensional disturbances can sustain or enhance the vital periodic accumulations of spanwise vorticity once their amplitude exceeds some threshold. This feedback loop is considered to be the key to the transition process. Owing to the broad‐band nature of secondary instability, however, the prediction of transition in practice requires additional insight into the ‘natural’ disturbance background. The sensitivity of the transition process to initial data in a broad band of frequencies and spanwise wave numbers poses new challenges for non‐linear theories and numerical simulations.
The application of multigrid to Navier‐Stokes simulation of 3D flow in axial and radial flow turbomachinery
Authors: Dawes W. N. 
Published: August 2005

AbstractThis paper describes the implementation of a 3D Navier‐Stokes solver within the framework of a multigrid strategy. The ability of multigrid to improve and sustain code performance over a range of mesh sizes and a variety of difficult flow problems is investigated. The code is applied to the study of the shock‐induced boundary layer separation on a channel hump, the flow in a 2D cascade of compressor blades, the secondary flow development in a linear cascade of gas turbine blades and the Eckardt backswept centrifugal impeller. In each case multigrid leads to significantly improved performance.
On finite element approximations of the streamfunction‐vorticity and velocity‐vorticity equations
Authors: Gunzburger Max D. , Peterson Janet S. 
Published: August 2005

AbstractWe consider finite element methods for vorticity formulations of viscous incompressible flows. In two‐dimensional settings the familiar streamfunction‐vorticity formulation is examined. We focus on its accuracy, especially when using low‐order elements, and on its use with a variety of boundary conditions and in multiply connected domains. In three dimensions the velocity‐vorticity formulation is shown to be preferable, and a promising algorithm using this formulation is presented. We close by considering the recovery of the pressure field once the streamfunction or velocity fields are known. In particular we describe and analyse an algorithm for recovering the pressure which is based on well known methods for the primitive variable formulation and which requires no boundary conditions on the pressure at solid walls.