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561.
A shock wave implosion in an axisymmetric chamber with a convex bounding wall is studied experimentally, analytically and
numerically. The converging shock front area in this geometry shrinks quickly as the shock wave approaches the center point.
The analytical theory predicts that the corresponding rate of post-shock pressure and density increase in this case exceeds
essentially that achieved in the classical cylindrical or spherical shock implosions, hence, the phenomenon is referred to
as “super-spherical cumulation”. The experiments confirm higher intensity of the super-spherical implosion compared with the
cylindrical one, both driven by identical high-current pulsed electric discharges. The converging shock stability is analyzed
in the framework of the CCW theory. The numerical results obtained using a locally-adaptive unstructured grid technique agree
well with the theoretical predictions of the converging shock wave intensity.
Received 28 January 1998 / Accepted 6 November 1998 相似文献
562.
Dong-yangShi Shi-pengMao Shao-chunChen 《计算数学(英文版)》2005,23(3):261-274
The main aim of this paper is to study the error estimates of a nonconforming finite element with some superconvergence results under anisotropic meshes. The anisotropic interpolation error and consistency error estimates are obtained by using some novel approaches and techniques, respectively. Furthermore, the superclose and a superconvergence estimate on the central points of elements are also obtained without the regularity assumption and quasi-uniform assumption requirement on the meshes. Finally, a numerical test is carried out, which coincides with our theoretical analysis. 相似文献
563.
564.
非结构网格的生成及新型数据类型的应用 总被引:3,自引:0,他引:3
本文基于 Delaunay三角化方法及局部重组的阵面推进法,给出了任意形状平面区域的非结构化网格剖分方法。文中对加点方法及数据结构和存取模式进行了改进,同时应用链表结构、动态数组和派生类型的数据变量,对算法进行优化,节省了计算内存,提高了网格的生成效率。本文研究为特殊计算区域的三维非结构化网格的生成提供了基本方法。 相似文献
565.
In this paper an implicit fractional step method for the solution of the two-dimensional, time-dependent, incompressible Navier-Stokes equations is presented. The current method was developed for use on an unstructured grid made up of triangles. The basic principles of this method are that the evaluation of the time evolution is split into intermediate steps and that for the spatial discretization of the flow equations a finite volume discretization on an unstructured triangular mesh is used. The present approach has been used to simulate viscous, laminar flows for various Reynolds numbers in test cases such as a backward-facing step, a square cavity and a channel with wavy boundaries. 相似文献
566.
In this paper we present a second order finite volume method for the resolution of the bidimensional ideal MHD equations on adaptively refined triangular meshes. Our numerical flux function is based on a multidimensional extension of the Roe scheme proposed by Cargo and Gallice for the 1D MHD system. If the mesh is only composed of triangles, our scheme is proved to be weakly consistent with the condition …B=0. This property fails on a cartesian grid. The efficiency of our refinement procedure is shown on 2D MHD shock capturing simulations. Numerical results are compared in case of the interaction of a supersonic plasma with a cylinder on the adapted grid and several non-refined grids. We also present a mass loading simulation which corresponds to a 2D version of the interaction between the solar wind and a comet. 相似文献
567.
F. Fang C. C. Pain I. M. Navon M. D. Piggott G. J. Gorman P. E. Farrell P. A. Allison A. J. H. Goddard 《国际流体数值方法杂志》2009,60(7):709-732
Inflow and outflow boundary conditions are essential for the application of computational fluid dynamics to many engineering scenarios. In this paper we present a new boundary condition implementation that enables the simulation of flow through permeable boundaries in the Lagrangian mesh‐free method, smoothed particle hydrodynamics (SPH). Each permeable boundary is associated with an inflow or outflow zone outside the domain, in which particles are created or removed as required. The analytic boundary condition is applied by prescribing the appropriate variables for particles in an inflow or outflow zone, and extrapolating other variables from within the domain. Characteristic‐based non‐reflecting boundary conditions, described in the literature for mesh‐based methods, can be implemented within this framework. Results are presented for simple one‐dimensional flows, quasi‐one‐dimensional compressible nozzle flow, and two‐dimensional flow around a cylinder at Reynolds numbers of 40 and 100 and a Mach number of 0.1. These results establish the capability of SPH to model flows through open domains, opening a broad new class of applications. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
568.
S. Morigi 《Applied mathematics and computation》2009,215(4):1561-1572
This paper investigates a parameterization method for polygonal meshes which is able to improve map distortion exploiting local curvature of the surface mesh. Parametrization is an important tool in geometric modelling and computer graphics applications such as, for example, texture mapping, shape morphing, and remeshing. The paper presents a feature-sensitive scheme which is based on a stretch-minimizing strategy which iterates the shape-preserving parameterization taking into account the influence of the curvature on the mesh stretch. In particular, the main goal is to provide a distortion in the parametrization driven by the curvature directions, in such a way that strong distortion correspond to area with mean curvature approaching to zero. Computed examples demonstrate the effectiveness of the proposed method using geometric measures on angle, edge and area stretching, and illustrate the high quality of the mesh parameterizations produced. 相似文献
569.
570.
Yu Wang Songhe Song Zhijun Tan Desheng Wang 《Journal of computational physics》2009,228(17):6333-6348
This paper presents an adaptive method for variational curve smoothing based on level set implementation. A suitable cost functional is minimized via solving the derived Euler–Lagrangian equation, of which the discretization is conducted on unstructured triangular meshes by employing a simple and effective finite volume scheme. Through adaptive refinement of the mesh, the geometry features of the given curve can be well resolved in a cost-effective way. Various numerical experiments demonstrate the effectiveness and efficiency of the proposed approach. 相似文献