摘要:

The unsteady structure of a supersonic jet is highly three dimensional, though the mean flow is axisymmetric. In simulating a circular jet, the centerline represents a computational boundary. As such, spurious modes can be generated near centerline, unless special attention is given to the behavior of the 3D structure near the centerline. Improper treatment of the dependent variables near the centerline results in the solution diverging or being suitable only for small amplitude excitation. With a careful treatment of the centerline formulation, no spurious mode is generated. The results show that a near linear disturbance growth is obtained, as the linear stability theory indicates. At high levels of excitation, nonlinear development of disturbances is evident and saturation is reached downstream.

ISSN:1061-8562    

DOI:10.1080/10618560008940893

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The accuracy of MUSCL upwind and Yee-Roe-Davis symmetric TVD schemes for simulating low Mach number flow is studied through a numerical experiment of the 2-D lid driven cavity problem. The steady slate solution is reached by using a marching approach based on the pseudocompressibilty method in conjunction with implicit approximate factorization. A finite volume discretization of the conservation equations is used with a four level multigrid method to accelerate the convergence. The tests performed which were in the range of 100 ≤ Re ≤ 5000, show that the Yee-Roe-Davis symmetric scheme generates results in very good agreement with the benchmark results over this range of Re. The MUSCL upwind scheme accuracy deteriorates with the increasing Re.

ISSN:1061-8562    

DOI:10.1080/10618560008940894

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Among the various numerical schemes developed since the ’80s for the computation of the compressible Euler equations, the vast majority produce in certain cases spurious pressure glitches at sonic points. This flaw is particularly visible in the computation of transonic expansions and leads lo unphysical “expansion shocks” when the flow undergoes rapid change of direction.

ISSN:1061-8562    

DOI:10.1080/10618560008940895

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The two-dimensional vortex-in-cell method is used in the simulation of a spatially growing mixing layer at a high Reynolds number. Criteria, showing that the vortex grid density plays a role in obtaining a converged solution, are presented. Numerical experiments are conducted to test the criteria by varying the number of vortices and the grid sizes. The effects on the momentum thickness and on the peak values of the root-mean-square velocity fluctuations, and negative cross-stream correlation are discussed in terms of the vortex grid density.

ISSN:1061-8562    

DOI:10.1080/10618560008940896

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Evolution of the vortices of monopole and dipole types in a viscous fluid is considered numerically. Theory and numerical results are compared for some particular exact solutions. A good agreement is obtained for the dipole vortices (viscous Chaplygin-Lamb vortices) moving with variable velocities due to viscosity. For the monopole type vortices, the agreement is more or less good only at an initial stage of their evolution; while in the long-lime asymptotics the law of vorticity decay other than the theoretical one is discovered. The reason for such a discrepancy is discussed. The interactions of dipole vortices with each other and with rigid boundaries are studied too. The stability of dipole vortices with complex internal structures is considered briefly.

ISSN:1061-8562    

DOI:10.1080/10618560008940897

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

In the present work, we carry out a finite element analysis of visco-elastic flows for the multi-mode Giesekus model at high shear rales flow. We have already proposed a new numerical scheme suitable for the analysis of visco-elastic fluids in the previous paper. It is mainly composed of two parts: the MUSCL (Monotone Upstream-centered Scheme for Conservation Law)-TVD (Total Variation Diminishing) for the numerical analysis of the constitutive equation and the GSMAC (Generalized Simplified Maker and Cell)-FEM (Finite Element Method) for the momentum equation. We apply the new scheme for the flows through the contraction plane for the multi-mode Giesekus model that considers eight relaxation modes. It shows suitable matching with experimental data at low shear rates, and we confirm that the results are stable at high shear rates.

ISSN:1061-8562    

DOI:10.1080/10618560008940898

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor