独立覆盖流形法的通用计算公式和通用程序设计——(二)通用程序设计

苏海东, 杨震, 颉志强, 祁勇峰, 龚亚琦

长江科学院院报 ›› 2025, Vol. 42 ›› Issue (4) : 202-210.

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长江科学院院报 ›› 2025, Vol. 42 ›› Issue (4) : 202-210. DOI: 10.11988/ckyyb.20240113
独立覆盖流形法专栏

独立覆盖流形法的通用计算公式和通用程序设计——(二)通用程序设计

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General Formulas and Program Design for Manifold Method Based on Independent Covers Ⅱ: General Program Design

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摘要

在独立覆盖流形法通用计算公式的基础上,给出了计算程序的整体流程。对一维至三维各种几何形体(包括分区、条带和边界面)的积分方式进行总结,基于点、线、面、体的单纯形几何元素开发积分程序,实现网格形状的通用性。提出将积分模块与被积函数模块分开考虑的编程思路,然后再将两者任意组合,使程序具备了扩展性,有望实现偏微分方程求解的通用性。通过级数公式和相应的各种坐标以及坐标转换矩阵、级数矩阵的确定,实现了级数的通用性。所有计算参数都可以通过用户子程序输入公式,实现输入参数的通用性。最终可用较少的程序代码,实现弹性力学运动微分方程、传导方程、波动方程的一维至三维稳态和瞬态分析(含一类至三类边界条件)。

Abstract

Based on the general calculation formula of the manifold method based on independent covers presented in the previous article, we provide the flowchart of the calculation program. First, we summarize the integration methods for various geometric shapes (such as partitions, stripes, and boundary faces) that may appear in one- to three-dimensional spaces. On this basis, we develop integration programs according to simplex geometric elements of points, lines, faces, and bodies. This approach ensures the universality for any mesh shape. Next, we propose a programming strategy that separates the integration module from the integrand function module. The arbitrary combination of these two modules endows the program with extensibility and the potential to achieve universality in solving partial differential equations. Moreover, the universality of series is realized through the determination of series formulas, corresponding coordinates, coordinate transformation matrices, and series matrices. In addition, all calculation parameters can be input via formulas using user subroutines, thus achieving universality of input parameters. Ultimately, with relatively less program code, we can conduct one- to three- dimensional steady-state and transient analyses of the differential equations of motion in elasticity, conduction equations, and wave equations, including one to three types of boundary conditions.

关键词

偏微分方程 / 级数解 / 网格剖分 / 精确几何 / 独立覆盖 / 数值流形方法

Key words

partial differential equations / series solutions / mesh division / exact geometry / independent covers / numerical manifold method

引用本文

导出引用
苏海东, 杨震, 颉志强, . 独立覆盖流形法的通用计算公式和通用程序设计——(二)通用程序设计[J]. 长江科学院院报. 2025, 42(4): 202-210 https://doi.org/10.11988/ckyyb.20240113
SU Hai-dong, YANG Zhen, XIE Zhi-qiang, et al. General Formulas and Program Design for Manifold Method Based on Independent Covers Ⅱ: General Program Design[J]. Journal of Changjiang River Scientific Research Institute. 2025, 42(4): 202-210 https://doi.org/10.11988/ckyyb.20240113
中图分类号: O241.82 (偏微分方程的数值解法)   

参考文献

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苏海东. 独立覆盖流形法的通用计算公式和通用程序设计:(一)通用计算公式[J]. 长江科学院院报, 2025, 42(4):193-201,210.
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摘要
有限元网格形状要尽可能规则,网格之间必须通过结点连接,这些要求给复杂形状求解域的数值计算带来很大的前处理工作负担,而且实际的曲线边界一般要离散成有限单元能够描述的形式,难以模拟CAD模型的精确几何。针对这些问题,基于独立覆盖流形法提出任意形状且任意连接的覆盖网格,在CAE分析中模拟CAD模型的精确几何边界及其边界条件:将求解域划分为可包含曲线边的任意形状的块体网格,可以采用单纯形解析积分和数值积分2种方式进行块体积分;仅需在积分过程中考虑块体之间的窄条形(包括曲线条)的覆盖重叠区域,而不必在计算模型中生成这些条形;通过边界条实现本质边界条件的严格施加,包括曲线上的边界条件;给出2个数值算例验证了方法的有效性。任意形状的覆盖网格将为实现基于精确几何模型的数值计算及其完全自动化的前处理开辟新的路径。
(SU Hai-dong, FU Zhi, XIE Zhi-qiang. Numerical Computations Based on Cover Meshes with Arbitrary Shapes and on Exact Geometric Boundaries[J]. Journal of Yangtze River Scientific Research Institute, 2020, 37(7): 167-174.) (in Chinese)
Finite element meshes should keep regular shape as much as possible, and ensure correct connections through nodes. These requirements pose a great burden to the pre-processing procedure of numerical computations for solving domains with complex shapes. On the other hand, curve boundaries in practical situations are usually discretized into shapes which finite element meshes can describe, resulting in an imprecise simulation of exact geometry defined in CAD. In view of this, cover meshes with arbitrary shapes and arbitrary connections are implemented using Manifold Method based on independent covers. Exact geometric boundaries of CAD models and boundary conditions are simulated in CAE analyses. The solving domain is divided into block meshes with arbitrary shapes which can contain curve boundaries. And two approaches, including analytical integration method with simplexes and numerical integration method, can be used for the block integration. The thin strips for cover overlapping are considered only in the integration process, but are not necessarily involved in the generation of computation models. Essential boundary conditions are strictly applied through boundary strips, including the boundary conditions on curves. Moreover, two numerical examples are given to illustrate the validity of the method. Cover meshes with arbitrary shapes bring about a new path for numerical computations based on exact geometric models and automatic pre-processing procedures.
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(SU Hai-dong, SONG Wen-shuo, GONG Ya-qi, et al. General Formulas and Program Design for Manifold Method Based on Independent Covers Ⅲ: Example Verification[J]. Journal of Changjiang River Scientific Research Institute, 2025, 42(4):211-218.) (in Chinese)
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基金

国家自然科学基金项目(U2340229)

责任编辑: 黄玲
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