摘要:

AbstractSeveral difference schemes approximating a mathematical model of river pollution are investigated and their truncation error, stability and monotonicity conditions are shown. Based on numerical experiments, the classical six‐point schemes and some new modified box schemes are compared. The latter proved to be not only faster but also more accurate for practically used step length

ISSN:0271-2091    

DOI:10.1002/fld.1650211202

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractIn this study, we examine the numerical simulation of transient viscoelastic flows with two moving free surfaces. A modified Galerkin finite element method is implemented to the two‐dimensional non‐steady motion of the fluid of the Oldroyd‐B type. The fluid is initially placed between two parallel plates and bounded by two straight free boundaries. In this Lagrangian finite element method, the spatial mesh deforms in time along with the moving free boundaries. The unknown shape of the free surfaces is determined with the flow fieldu, v, τ, pby the deformable finite element method, combined with a predictor‐corrector scheme in an uncoupled fashion. The moving free surfaces and fluid motion of both Newtonian and non‐Newtonian flows are investigated. The results include the influence of surface tension, fluid inertia and

ISSN:0271-2091    

DOI:10.1002/fld.1650211203

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe volume‐of‐fluid (VOF) method is a simple and robust technique for simulating free surface flows with large deformations and intersecting free surfaces. Earlier implementations used Laplace's formula for the normal stress boundary condition at the interface between the liquid and vapour phases. We have expanded the interfacial boundary conditions to include the viscous component of the normal stress in the liquid phase and, in a limited manner, to allow the pressure in the vapour phase to vary. Included are sample computations that show the accuracy of added third‐order‐accurate differencing schemes for the convective terms in the Navier‐Stokes equation (NSE), the viscous terms in the normal stress at the interface and the solution of potential flow in the vapour phase coupled with the solution of the NSE in the liquid phase. With these modifications we show that the VOF method can accurately predict the instability of a thin viscous sheet flowing through a stagnant vap

ISSN:0271-2091    

DOI:10.1002/fld.1650211204

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractVarious tests have been carried out in order to compare the performances of several methods used to solve the non‐symmetric linear systems of equations arising from implicit discretizations of CFD problems, namely the scalar advection‐diffusion equation and the compressible Euler equations. The iterative schemes under consideration belong to three families of algorithms: relaxation (Jacobi and Gauss‐Seidel), gradient and Newton methods. Two gradient methods have been selected: a Krylov subspace iteration method (GMRES) and a non‐symmetric extension of the conjugate gradient method (CGS). Finally, a quasi‐Newton method has also been considered (Broyden). The aim of this paper is to provide indications of which appears to be the most adequate method according to the particular circumstances as well as to discuss the implementation aspects of ea

ISSN:0271-2091    

DOI:10.1002/fld.1650211205

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA generalized formulation is applied to implement the quadratic upstream interpolation (QUICK) scheme, the second‐order upwind (SOU) scheme and the second‐order hybrid scheme (SHYBRID) on non‐uniform grids. The implementation method is simple. The accuracy and efficiency of these higher‐order schemes on non‐uniform grids are assessed. Three well‐known bench mark convection‐diffusion problems and a fluid flow problem are revisited using non‐uniform grids. These are: (1) transport of a scalar tracer by a uniform velocity field; (2) heat transport in a recirculating flow; (3) two‐dimensional non‐linear Burgers equations; and (4) a two‐dimensional incompressible Navier‐Stokes flow which is similar to the classical lid‐driven cavity flow. The known exact solutions of the last three problems make it possible to thoroughly evaluate accuracies of various uniform and non‐uniform grids. Higher accuracy is obtained for fewer grid points on non‐uniform grids. The order of accuracy of the examined schemes is maintained for some tested problems if the distribution of non‐uniform

ISSN:0271-2091    

DOI:10.1002/fld.1650211206

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

ISSN:0271-2091    

DOI:10.1002/fld.1650211207

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

ISSN:0271-2091    

DOI:10.1002/fld.1650211201

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY