摘要:

Spurious entropy is often used as a criterion by which the accuracy of a numerical solution of the Euler equations may be judged. In the case of subcritical, compressible flows, we have been able to develop a mathematical theory relating the observed spurious entropy to its local generation. Moreover, the theory may be expressed in terms of the finite volume residual for the Euler equations and hence related to the theory of adaptive finite element methods. We have analysed the formula for the local generation of the spurious entropy and have shown it to be made up of terms of very simple form for which the effect of mesh quality can be assessed. In order to demonstrate the effectiveness of the theory in the context of adaptive grid generation, the local estimator is coupled with an existing mesh movement algorithm, with much improved results being obtained.

ISSN:1061-8562    

DOI:10.1080/10618569808961684

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A new approach for optimal shape design based on a CAD-free framework for shape and unstructured mesh deformations, automatic differentiation for the gradient computation and mesh adaption by metric control is presented. The CAD-free framework is shown to be particularly convenient for optimization when the mesh connectivities and control space size are variable during optimization. Constrained optimizations for subsonic, transonic and supersonic regimes have been investigated.

ISSN:1061-8562    

DOI:10.1080/10618569808961685

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A numerical scheme for the prediction of free surface flows is presented and investigated. The method is based on an adaptive grid Eulerian finite-volume method, where non-orthogonal boundary-fitted moving grids are employed to follow the free surface. The underlying flow solver consists in a pressure-correction scheme of SIMPLE type with multigrid acceleration, which is iteratively combined with the moving grid technique. Several numerical examples are considered to illustrate the capabilities of the approach.

ISSN:1061-8562    

DOI:10.1080/10618569808961686

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This paper is concerned with the development of a numerical method for the computation of two-dimensional time-dependent free-surface problems where surface tension cannot be neglected. The imposition of a surface tension force in a finite element method requires the evaluation of a line integral where the curvature R of the interface has to be accurately evaluated. In this paper, we demonstrate how this line integral can be replaced by a volume integral over the entire domain avoiding the explicit computation of R. The proposed method is then applied to the computation of the complex deformation of a drop of a viscous fluid immersed in another fluid and submitted to a shearing flow field.

ISSN:1061-8562    

DOI:10.1080/10618569808961687

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A comparative study of low-Re wall-distance-free (WDF) turbulence models in incompressible flows is presented. The study includes the WDF k-ϵ and the three-equation WDF k-ϵ-γ as well as two k-ϵ models which invoke the distance from the wall. The models are implemented in conjunction with a characteristics-based method and an implicit unfactored scheme. Comparison with direct-numerical-simulation data reveals that the WDF models provide much more accurate results for the dissipation rate, especially in the near wall region. A grid refinement study further reveals that the models which explicitly involve the distance from the wall cannot capture the correct turbulence dissipation rate behaviour in the near-wall region even on the finest grid, where grid-independent solution is achieved. However, the low-Re WDF models require slightly more iterations than the other k - ϵ models to converge. Results are presented for channel, flat plate and backward-facing step flows.

ISSN:1061-8562    

DOI:10.1080/10618569808961688

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A fully conservative zonal interface algorithm for overlapped (Chimera) grid has been extended to handle moving body flows. To ensure flow conservation, the motion of the computational grid needs to be taken into account. Several new issues arising from moving and deforming grids, e.g., vanishing and new-born cell problems, are addressed with a cell-merging-unmerging technique. The grid velocities are determined in a way which satisfies free-stream preserving (the Geometric Conservation Laws)The flow solver is based on a fully implicit, cell-centered finite volume discretization with MUSCL reconstruction and Roe's approximate Riemann solver. The interface algorithm is first validated by tackling the case of supersonic flow over a cylinder. Then several moving body flow problems are simulated using the current approach to demonstrate its capabilities.

ISSN:1061-8562    

DOI:10.1080/10618569808961689

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor