摘要:

A numerical method for the computation of topological and geometric properties of iso-surfaces with and without boundaries is developed. It is based on triangulation and provides the Euler characteristic, the number of disjoint surface parts and geometric properties such as surface area and integrals of vector and tensor fluxes over the surface. A quantitative measure for the intrinsic topology of level surfaces is constructed using the Euler number, that is suitable for solutions of the Navier-Stokes equations. The numerical accuracy of the method is shown to be satisfactory.

ISSN:1061-8562    

DOI:10.1080/10618569708940796

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

An unstructured 3D Euler solver is parallelized on a Thinking Machine Corporation Connection Machine 5, distributed memory computer with vectorizing capability. In this paper, the SIMD strategy is employed through the use of the CM Fortran language and the CMSSL scientific library. The performance of the CMSSL mesh partitioner is evaluated and the overall efficiency of the parallel flow solver is discussed.

ISSN:1061-8562    

DOI:10.1080/10618569708940797

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

We study the numerical solution of optimal control problems associated with the two-dimensional viscous incompressible flows which are governed by the Navier-Stokes equations. Although the techniques apply to more general settings, the presentation is confined to the objectives of minimizing the vorticity in the steady-state case with distributed controls and tracking the velocity field in the nonstationary case with piecewise distributed controls. In the steady-state case, we develop a systematic way to use the Lagrange multiplier rules to derive an optimality system of equations from which an optimal solution can be computed; finite element methods are used to find approximate solutions for the optimality system of equations. In the time-dependent case, a piecewise-in-time optimal control approach is proposed and the fully discrete approximation algorithm for solving the piecewise optimal control problem is defined. Numrical results are presented for both the steady-state and time-dependent optimal control problems.

ISSN:1061-8562    

DOI:10.1080/10618569708940798

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Rigorous methods are presented for the derivation of all terms in the equations for the Reynolds stresses and dissipation components, from finite-volume large-eddy simulations of turbulence performed on staggered meshes. The methods are designed to produce exact balance to machine accuracy in the computed budgets, and yield a single term representing the statistical convergence error for each computed budget. Aspects of these budgets are presented for boundary-layer simulations, demonstrating the utility of the method.

ISSN:1061-8562    

DOI:10.1080/10618569708940799

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

This paper presents a new Arbitrary Lagrangiae-Eulerian (ALE) finite element method for the analysis of three-dimensional large-amplitude sloshing problems. The present method is composed of three phases, i.e., Phase 1: Purely Lagrangian calculation. Phase 2: Remeshing procedure and Phase 3: Rezoning procedure. By applying these procedures, the present method has succeeded in overcoming the main difficulty of computation in the large-amplitude sloshing analysis. In the Lagrengian calculation, a new fractional step method that satisfies the free-surface boundary condition has been applied, and treatment of the free surface on the multi-sloped wall boundary has been advanced. In the remeshing procedure, a method based on boundary-fitted coordinates is introduced. Numerical results are compared with experimental results, and it is shown that this method is sufficiently accurate to calculate the three-dimensional sloshing. Furthermore, a numerical example of large-amplitude sloshing in a tank with roofs and chamfers illustrates the validity of the method for the computation of large-amplitude sloshing waves whose free surface configuration is a double-valued function.

ISSN:1061-8562    

DOI:10.1080/10618569708940800

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

In this paper, a sixth-order spatially accurate and fourth-order temporally accurate finite-difference scheme is employed to study a spatially developing mixing layer. We examine the spatial growth rate of the boundary layer, its dependence on density and velocity ratios and compare our results with experimental trends reported in the literature. We show that as surmised by other workers and also experimentally found, that rate of growth of the mixing layer is proportional to the ratio of the difference of the velocities in the two streams normalized by the sum of the velocities in the two streams.

ISSN:1061-8562    

DOI:10.1080/10618569708940801

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor