用自适应流线网格计算定常超声速流场

提出一个用自适应流线网格计算定常超声速流场的数值方法。Friedrichs-Lax格式推广到任意四边形网格,在迭代过程中得到速度场后,从流线方程计算流线的位置,最后算出由本方法得到高分辨率结果     

GENERALIZED DIFFERENCE METHODS ON ARBITRARY QUADRILATERAL NETWORKS

1.IntroductionConsidertheboundaryvalueproblemofthePoissonequationwherefiisaconvexpolygonregon;r~OfftheboundaryofOandf(x,y)aknownfunctiononfi.Thegeneralizeddifferencemethodsonquadrilateralnetworksforellipticequationsareproposedin[11],'wheretheconverge...     

Routing multiterminal nets on a hexagonal grid

Channel routing is a vital task in the layout design of VLSI circuits. Multiterminal channel routing is different from two-terminal one. While the later is quite understood, the former still poses the difficulty. In this paper, we investigate the multiterminal channel routing problem in a hexagonal model, whose grid is composed of horizontal tracks, right tracks (with slope +60°), and left tracks (with slope −60°). We present an efficient algorithm for routing multiterminal nets on a channel of width d + 3, where d is the problem density. Furthermore, we can wire the layout produced by the router using four layers and there are no overlaps among different layers. This improves the previous known results [15, 19].     

正交曲线坐标系下紊流数学模型的曲率修正

考虑弯曲边界曲率效应对水流水力特性的影响,建立了正交曲线坐标系下的素流数学模型。通过计算实例说明,该数学模型能够很好地帷有复杂边界的流线弯曲水流的水力特性。     

PISO算法在求解方柱绕流非定常尾迹中的应用

应用PISO算法及非交错斜交网格技术,编制了求解二维定常、非定常流动的通用程序。计算分析了定常不可压缩Couette流动以及水平通道内方柱绕流尾迹的非定常流动,并详细分析了不同时刻方柱后尾迹的旋涡结构及发展过程,得到了合理的结果。验证了非迭代PISO算法及非交错斜交网格在分析非定常流动中的有效性,为进一步开展非定常流动的数值分析奠定了基础．     

The implementation of an aeronautical CFD flow code onto distributed memory parallel systems

The parallelization of an industrially important in‐house computational fluid dynamics (CFD) code for calculating the airflow over complex aircraft configurations using the Euler or Navier–Stokes equations is presented. The code discussed is the flow solver module of the SAUNA CFD suite. This suite uses a novel grid system that may include block‐structured hexahedral or pyramidal grids, unstructured tetrahedral grids or a hybrid combination of both. To assist in the rapid convergence to a solution, a number of convergence acceleration techniques are employed including implicit residual smoothing and a multigrid full approximation storage scheme (FAS). Key features of the parallelization approach are the use of domain decomposition and encapsulated message passing to enable the execution in parallel using a single programme multiple data (SPMD) paradigm. In the case where a hybrid grid is used, a unified grid partitioning scheme is employed to define the decomposition of the mesh. The parallel code has been tested using both structured and hybrid grids on a number of different distributed memory parallel systems and is now routinely used to perform industrial scale aeronautical simulations. Copyright © 2000 John Wiley & Sons, Ltd.     

AN ADAPTIVE FINITE ELEMENT SCHEME FOR HYDRAULIC FRACTURING WITH PROPPANT TRANSPORT

A mathematical model and adaptive finite element scheme are developed for describing the distribution of proppant in a propagating hydraulic fracture. The governing equation for proppant concentration is derived by applying the conservation law of mass to the proppant and to the proppant-laden fluid. Shah's empirical equation, which relates the proppant concentration and the indices of the non-Newtonian fluid, is used to describe the proppant-laden fluid. The proppant distribution inside a hydraulic fracture can then be obtained by solving the proppant concentration equation together with the governing equations of fluid and elasticity for a hydraulic fracturing. A novel moving grid scheme is developed that combines grid point insertion with redistribution. Four examples corresponding to different in situ stress distributions are computed to demonstrate the scheme. © 1997 by John Wiley & Sons, Ltd.     

A fast algorithm to solve viscous two-phase flow in an axisymmetric rocket nozzle

A numerically fast algorithm has been developed to solve the viscous two-phase flow in an axisymmetric rocket nozzle. A Eulerian–Eulerian approach is employed in the computation to couple the gas–particle flow. Turbulence closure is achieved using a Baldwin–Lomax model. The numerical procedure employs a multistage time-stepping Runge–Kutta scheme in conjunction with a finite volume method and is made computationally fast for the axisymmetric nozzle. The present numerical scheme is applied to compute the flow field inside JPL and AGARD nozzles. © 1998 John Wiley & Sons, Ltd.     

On some variational acceleration techniques and related methods for local refinement

This paper shows that the well-known variational acceleration method described by Wachspress (E. Wachspress, Iterative Solution of Elliptic Systems and Applications to the Neutron Diffusion Equations of Reactor Physics, Prentice-Hall, Englewood Cliffs, NJ, 1966) and later generalized to multilevels (known as the additive correction multigrid method (B.R Huthchinson and G.D. Raithby, Numer. Heat Transf., 9 , 511–537 (1986))) is similar to the FAC method of McCormick and Thomas (S.F McCormick and J.W. Thomas, Math. Comput., 46 , 439–456 (1986)) and related multilevel methods. The performance of the method is demonstrated for some simple model problems using local refinement and suggestions for improving the performance of the method are given. © 1998 John Wiley & Sons, Ltd.     

Three-dimensional incompressible Navier–Stokes equations on non-orthogonal staggered grids using the velocity–vorticity formulation

This paper is concerned with the numerical resolution of the incompressible Navier–Stokes equations in the velocity–vorticity form on non-orthogonal structured grids. The discretization is performed in such a way, that the discrete operators mimic the properties of the continuous ones. This allows the discrete equivalence between the primitive and velocity–vorticity formulations to be proved. This last formulation can thus be seen as a particular technique for solving the primitive equations. The difficulty associated with non-simply connected computational domains and with the implementation of the boundary conditions are discussed. One of the main drawback of the velocity–vorticity formulation, relative to the additional computational work required for solving the additional unknowns, is alleviated. Two- and three-dimensional numerical test cases validate the proposed method. © 1998 John Wiley & Sons, Ltd.