摘要:

AbstractA simple technique is presented for the numerical solution of two‐dimensional time‐dependent flows, either laminar or turbulent, involving multiple free surfaces of arbitrary configuration. The governing equations are the Reynolds equations for incompressible fluids with Boussinesq closure, thek‐ and ϵ‐equations and an additional equation describing the fluid configuration. This technique can potentially describe the propagation, deformation and overturning of pre‐breaking waves and the mean flow, surface configuration and turbulence field after breaking. The properties of the method are illustrated by several calculational examples. The main parts of the algorithm are optimized for vector processing in a form suitable for installation in supercomputer

ISSN:0271-2091    

DOI:10.1002/fld.1650150202

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe steady incompressible laminar flow field over a 6:1 prolate spheroid at 10° incidence and a Reynolds number of 1·6 × 106is investigated numerically by solving a reduced set of the Navier‐Stokes equations. The present study moves one step beyond the boundary layer approximation by relaxing the requirement of an imposed pressure field to permit the calculation of both attached and longitudinal vortical flow fields. The results shed light on the flow properties over slender bodies at intermediate incidence. The longitudinal vortex is found to be weak relative to vortex‐dominated flows. Nevertheless, it has pronounced effects on the flow near the surface and on global features of the flow field. A displacement velocity which describes the effect of the vortical flow on the outer inviscid flow is defined. The line on the spheroid where the displacement velocity vanishes closely follows the projection of the vortex centreline on the surface of the spheroid. It is demonstrated numerically that the convergence of the skin friction lines is not a unique criterion for identifying a vorte

ISSN:0271-2091    

DOI:10.1002/fld.1650150203

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe background of this paper is the study of transport of pollutants by groundwater flow when released from a repository in a rock salt formation. Flow in regions surrounding such formations may be strongly influenced by variations in salt concentrations, a factor requiring special attention in the development of realistic mathematical models for predicting transport of pollutants. Indispensable for this development are advanced numerical methods. The aim of this paper is to illustrate the application of such a method to a class of non‐linear brine transport problems in one space dimension. Our method is based on the method of lines for solving time‐dependent partial differential equations. The method is of the finite difference type, implicit and thus applicable to wide classes of (one‐space‐dimensional) partial differential equation systems. The main feature of the method, however, is that it can automatically move the spatial grid for evolving time and thus is able to refine the grid in regions with large, special transitions. The grid refinement has provea to be a very valuable facility in the numerical modelling of brine transport problems involving low and high salt concentrations. From the user's point of view an additional advantage of the moving grid method is that it can be implemented in advanced, user‐oriented method‐of‐lines software packages based on implicit stiff ODE solvers. In the brine transport application discussed here we have used the p

ISSN:0271-2091    

DOI:10.1002/fld.1650150204

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractA compact, finite volume, time‐marching scheme for the two‐dimensional Navier‐Stokes equations of viscous fluid flow is presented. The scheme is designed for unstructured (locally refined) quadrilateral meshes. An earlier inviscid equation (Euler) scheme is employed for the convective terms and the emphasis is on treatment of the viscous terms. An essential feature of the algorithm is that all necessary operations are restricted to within each cell, which is very important when dealing with unstructured grids. Numerical issues which have to be addressed when developing a Navier‐Stokes scheme are investigated. These issues are not limited to the particular Navier‐Stokes scheme developed in the present work but are general problems. Specifically, the extent of the numerical molecule, which is related to the compactness of the scheme and to its suitability for unstructured grids, is examined. An approach which considers suppression of odd‐even mode decoupling of the solution when designing a scheme is presented. In addition, accuracy issues related to grid stretching as well as boundary layer solution contamination due to artificial dissipation are addressed. Although the above issues are investigated with respect to the specific scheme presented, the conclusions are valid for an entire class of finite volume algorithms. The Navier‐Stokes solver is validated through test cases which involve comparisons with analytical, numerical and experimental results. The solver is coupled to an adaptive algorithm for high‐Reynolds‐number aerofoil

ISSN:0271-2091    

DOI:10.1002/fld.1650150205

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractAn extension of the Osher upwind scheme to non‐equilibrium reacting flows is presented, Owing to the presence of source terms, the Riemann problem is no longer self‐similar and therefore its approximate solution becomes tedious. With simplicity in mind, a linearized approach which avoids an iterative solution is used to define the intermediate states and sonic points. The source terms are treated explicitly. Numerical computations are presented to demonstrate the feasibility, efficiency and accuracy of the proposed method. The test problems include a ZND (Zeldovich‐Neumann‐Doring) detonation problem for which spurious numerical solutions which propagate at mesh speed have been observed on coarse grids. With the present method, a change of limiter causes the solution to change from the physically correct CJ detonation solution to the spurious weak detonation s

ISSN:0271-2091    

DOI:10.1002/fld.1650150206

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThis paper presents a non‐iterative numerical technique for computing time‐dependent gas‐droplet flows. The method is a fully interacting combination of Eulerian fluid and Lagrangian particle calculations. The interaction calculations between the two phases are formulated on a pressure‐velocity‐coupling procedure based on the operator‐splitting technique. This procedure eliminates the global iterations required in the conventional particle‐source‐in‐cell (PSIC) procedure. Turbulent dispersion calculations are treated by a stochastic procedure. Numerical calculations and comparisons with available experimental data as well as efficiency assessments are given for some sprays typical of spray combus

ISSN:0271-2091    

DOI:10.1002/fld.1650150207

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

ISSN:0271-2091    

DOI:10.1002/fld.1650150208

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

ISSN:0271-2091    

DOI:10.1002/fld.1650150201

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY