摘要:

Comprehensive numerical solutions of the steady state incompressible viscous flow over a three-dimensional backward-facing step up to Re = 800 are presented*. The results are obtained by the least-squares finite clement method (LSFEM) which is based on the velocity-pressurc-vorticity formulation. The computed model is of the same size as that of Armaly's experiment. Three-dimensional phenomena are observed even at low Reynolds number. The calculated values of the prima ry reattachment length are in good agreement with experimental results.

ISSN:1061-8562    

DOI:10.1080/10618569508904515

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A numerical procedure based on a least-squares finite element method (LSFEM) and Jacobi conjugate gradient method (JCG) is presented for the numerical solution of fluid flow and transport problems. Unlike many finite element methods, the LSFEM does not involve any upwinding factor. Furthermore, the LSFEM leads to a symmetric and positive definite linear system of equations which can be solved satisfactorily by a preconditioned conjugate gradient method. Four examples, lid-driven cavity flow, thermally-driven cavity flow, Rayleigh-Bénard convection and doubly-diffusive flow, are presented to validate the preconditioned conjugate gradient method. A comparison of the least-squares finite element method and theGalerkin finite clement method (GFEM) is also given. Finally, we demonstrate that the least-squares finite element method with the Jacobi conjugate gradient iterative technique is a promising approach to solve three-dimensional fluid flow and transport problems.

ISSN:1061-8562    

DOI:10.1080/10618569508904516

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The paper presents a finite element model for the solution of the three-dimensional, time-dependent Navier-Stokes equations. Isoparametric brick elements are used, with tri-linear interpolation for both velocity and pressure. A fractional-step algorithm is applied, and the advection-diffusion part of the system is solved using a two-step Taylor-Galerkin formulation. The pressure is computed from a Poisson equation, which is solved numerically using a preconditioned conjugate gradient method.

ISSN:1061-8562    

DOI:10.1080/10618569508904517

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This paper presents the numerical simulation of the gas-solid combustion physics in a gun tube with a mobile projectile by means of a flux-corrected transport nonlinear filtering scheme. The analysis is based on a one-dimensional formulation of the two-phase flowfield with the space-sharing interspersed continuum assumption. Apart from the Nobel-Abel equation of slate account the interphase drag and intergranular stress between the solid-gas phase are taken into account. The computer code has been used effectively to study the pressure-wave propagation and flame dynamics in a gun barrel containing granular solid propellants.

ISSN:1061-8562    

DOI:10.1080/10618569508904518

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A numerical procedure for the solution of the 3-D Navier-Stokes equations is developed and implemented for analyzing time-dependent incompressible viscous flows past arbitrary shapes. The equations are discretized using a finite element Galerkjn formulation with a streamwise upwinding option. The discretization in time is performed with fractional steps on the momentum equations to obtain the fractional step velocity field explicitly. The pressure field at each time level is obtained from an auxiliary potential function with the solution of a Poisson's equation, where an element-by-element (EBE) iteration procedure with preconditioned conjugate gradient (PCG) is employed. The method is used to study laminar flow past a circular cylinder with a swept bump. The flow field is solved for two different Reynolds numbers and the drag coefficient histories are obtained for the cylinder. The steady-state values of the drag coefficients show the 3-D relief effects on the cylinder. The computations are performed on an IBM 3090VF. The vectorization of the EBE algorithm allows a drastic reduction in terms of CPU time for each time step.

ISSN:1061-8562    

DOI:10.1080/10618569508904519

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The influence of the choice of transport and chemical models on the numerical simulation of hypersonic flows in chemical non-equilibrium is investigated. A coupled Euler/boundary layer method is employed, which facilitates the incorporation of different models and simplifies the calculation of the resulting flowfields. By considering hypersonic flows with different freestream conditions, it is shown that for flows dominated by chemical reactions, the computed flowfields can be sensitive to the choice of model. This sensitivity must be taken into account when defining test cases for the validation of numerical simulations of hypersonic re-entry flows.

ISSN:1061-8562    

DOI:10.1080/10618569508904520

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

An unsteady, compressible, two dimensional Navier-Stokes solver has been developed for the Connection Machine (CM-2 and CM-5). The solver has been applied to the computations of subsonic viscous flow past a pitching airfoil at Rec = 1044, (based on airfoil chord length) M∞ = 0.2, non-dimensional pitching rate Ωυ+ = 0.2 and 0.4. The algorithm for solving the Navier-Stokes equations is based on an unstructured grid of triangles. Roe's flux difference split method is employed for the inviseid fluxes. A discrete representation of Gauss' theorem is used for the viscous fluxes and heat transfer. A four stage modified Runge-Kutta algorithm is employed for the temporal integration. The algorithm is second order accurate in space and time. The implementation of the algorilhm on the Connection Machine and the investigation of the incipient boundary layer separation for a pitching airfoil are presented. The investigation of the effect of pitching rate on incipient boundary layer separation for a pitching airfoil shows that increasingly Ωυ+delays the formation of the three recirculating regions near the leading edge and results in higher values of the lift and drag coefficients.

ISSN:1061-8562    

DOI:10.1080/10618569508904521

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Several solution acceleration techniques, used to obtain steady-state CFD solutions as quickly as possible, are applied to an upwind Euler scheme to evaluate their effectiveness. Generalized minimal residual (GMRES), multigrid (MG), and ADI are compared to a four-stage Runge-Kutta scheme using several grids. The use of different acceleration schemes combinations of produces a complementary effect: the convergence becomes relatively independent of both size and quality of the grid.

ISSN:1061-8562    

DOI:10.1080/10618569508904522

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The nearshore zone is the area where the action of waves and currents on the sea bed is most intense, and where thermal stratification plays an important role in the transport of momentum, heat and pollutants. Therefore, in recent years this topic has drawn the attention of various investigations using analytical, experimental or numerical methods. The coastal water surface can be thought to be agitated by the uniform wind shear stress under flow field with thermal stratified density if the on-shore and off-shore wind blowing over the coastal water surface is assumed to be uniform. The physical properties that enter into the governing equations, which both describe the problem and are also essential to the solution of the phenomena of interest, are the eddy viscosity and the eddy diffusivity. The nonlinear governing equation is simplified in this present work by using the Boussinesq Approximation. A quadratic upwind finite volume method employing contravariant velocities as dependent variables is applied to the simulation of a three-dimensional steady state laminar incompressible flow. The flux terms in the basic equations were discretized via the QUICK1scheme for internal nodes and power-law scheme for the boundary nodes. The resulting algebraic equations were solved in a decoupled manner by the SIMPLEC2solution algorithm. A numerical method was then utilized in calculating the flow conditions for ratios of shear stress region and depth, and for different obstacles near the shoreline. Two circulation forms would be formed when the distance of the obstacle (Ex. breakwater) from the coast is equal to the depth. The cellular circulation in the lower layer would become gradually weakened with an increasing distance of the obstacle from the coast. If the eddy viscosity and eddy diffusivity are considered, the cellular circulation in the lower layer would also become gradually weakened. The cellular circulation would arise both behind and in front of the coastal structures, if the terrains with sedimentary obstacles are considered. The cellular circulation in the low layer would also tend to gradually disappear; however, the tendency of weakening is more apparent than the former. The effects of the cellular circulation in the lower layer would make it difficult to transport oxygen, heat and pollutants. Finally, the Coriolis force effect would be taken into consideration and therefore, its order of influence could be indicated.

ISSN:1061-8562    

DOI:10.1080/10618569508904523

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor