摘要:

AbstractThe kinetic‐theory‐based solution methods for the Euler equations proposed by Pullin and Reitz are here extended to provide new finite volume numerical methods for the solution of the unsteady Navier–Stokes equations. Two approaches have been taken. In the first, the equilibrium interface method (EIM), the forward‐ and backward‐flowing molecular fluxes between two cells are assumed to come into kinetic equilibrium at the interface between the cells. Once the resulting equilibrium states at all cell interfaces are known, the evaluation of the Navier–Stokes fluxes is straightforward. In the second method, standard kinetic theory is used to evaluate the artificial dissipation terms which appear in Pullin's Euler solver. These terms are subtracted from the fluxes and the Navier–Stokes dissipative fluxes are added in. The new methods have been tested in a 1D steady flow to yield a solution for the interior structure of a shock wave and in a 2D unsteady boundary layer flow. The 1D solutions are shown to be remarkably accurate for cell sizes large compared to the length scale of the gradients in the flow and to converge to the exact solutions as the cell size is decreased. The steady‐state solutions obtained with EIM agree with those of other methods, yet require a considerably reduced compu

ISSN:0271-2091    

DOI:10.1002/fld.1650170302

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractA numerical model for the compressible Navier–Stokes equations using local mesh embedding is presented. The model solves for three‐dimensional turbulent flow using an algebraic mixing length model of turbulence. The technique of control volume upwinding is used to produce a novel treatment, whereby the hanging nodes on the mesh interfaces are left with null control volumes. This yields an efficient discretization scheme which ensures second‐order accuracy, flux conservation and stability at the mesh interfaces, whilst retaining a simple interpolative treatment for the hanging nodes. The discrete flow equations are solved using the semi‐implicit pressure correction method. The accuracy of the embedded mesh solver is demonstrated by modelling the three‐dimensional flow through a cascade of turbine vanes at design and off‐design conditions. Mesh embedding gives a saving of 48% in the number of nodes. The embedded mesh solutions compare well with fine structured mesh solutions and experimental measurements. The capability of the embedded mesh solver to perform solution adaptive calculations is demonstrated using a two‐dimensional mid‐height section of the cascade at the off‐desig

ISSN:0271-2091    

DOI:10.1002/fld.1650170303

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractAn evaluation of some numerical methods for turbulent reacting flows in furnace‐like geometries is carried out. The Reynolds averaged Navier–Stokes equations and the two‐equationk–ϵ model together with either finite‐rate or infinite‐rate reaction models are solved numerically. Either single‐ or multiple‐step reactions together with the ‘eddy dissipation concept’ (EDC) are used to model reacting flows with finite reaction rates. The numerical scheme is finite difference based, together with a multi‐grid method and a local grid refinement technique. These methods have been used to calculate the combustion of propane in a single‐ and multiple‐burner configurations. In the former case, the sensitivity of the solution to variations in some model parameters (determining the reaction rate) and numerical parameters (mesh spacing) has been studied. It is noted that different dependent variables exhibit different levels of sensitivity to the variation in model parameters. Thus, calibration and validation of models for reacting flows require that one compares the mostsensitivevariables. For engineering purposes, on the other hand, one may calibrate and validate models with respect to the mostrelevantvariables. Our conclusion is that since sensitivity of the temperature distribution is relatively mild, one can still use EDC‐like methods in engineering applications where details of the temperature f

ISSN:0271-2091    

DOI:10.1002/fld.1650170304

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe past decade has known an increasing interest in the solution of the Euler equations on unstructured grids due to the simplicity with which an unstructured grid can be tailored around very complex geometries and be adapted to the solution. It is desirable that the mesh can be generated with minimum input from the user, ideally, just specifying the boundary geometry and, perhaps, a function to prescribe some desired mesh size. The internal nodes should then be found automatically by the grid generation code. The approach we propose here combines the Delaunay triangulation with ideas from the advancing front method of Peraireet al.and Löhneret al. Both methods are briefly reviewed in Section 1. Our method uses a background grid to interpolate local mesh size parameters that is taken from the triangulation of the given boundary nodes. Geometric criteria are used to find a set of nodes in a frontal manner. This set is subsequently introduced into the existing mesh, thus providing an update Delaunay triangulation. The procedure is repeated until no more improvement of the grid can be achieved by inserting new nodes

ISSN:0271-2091    

DOI:10.1002/fld.1650170305

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe main objective of this paper is to investigate the ability of a two‐dimensional two‐fluid computer code to predict the phase separation in a T‐junction. A new semi‐implicit numerical scheme is developed for solving the two‐fluid model equations. Special attention is directed to the modelling of the constitutive for the interfacial friction term. Detailed distribution of void fraction, pressure and velocities are obtained for an air–water mixture in a vertical tee. Good agreement was obtained between the computer code results and the experimental data for the phase separation in the

ISSN:0271-2091    

DOI:10.1002/fld.1650170306

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

ISSN:0271-2091    

DOI:10.1002/fld.1650170301

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY