共查询到20条相似文献,搜索用时 125 毫秒
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本文基于一种先进的非结构化网格生成系统和对于有限元离散误差的分析,将网格单元修正的自适应分析方法应用于二维瞬动态问题的研究,由于有限元近似求解的精度很大程度取决于所离散的网格质量,并且动态问题的数值解在不同时段变化较大以及由于波动求解中半离散化方法所引入的离散化的弥散现象,而网格单元修正的自适应分析方法能够在不同时段形成最佳网格来进行计算,使有限元分析的可靠性和近似程度得到提高;文中对地下圆形隧道 相似文献
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有限元网格修正的自适应分析及其应用 总被引:1,自引:0,他引:1
本文在对有限元变量连续条件分析的基础上,将应力误差范数用于计算结果的误差估计,使非结构化网格生成系统与有限元计算有机地结合起来,并将网格单元修正的自适应分析应用于二维应力集中问题的研究,从而实现了有限元最佳化离散,提高了有限元数值求解的可靠性和近似程度。 相似文献
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一种新的无网格方法与有限元耦合法 总被引:1,自引:1,他引:0
本文分析了Belytschko和Huerta提出的无网格方法和有限元耦合法各自存在的问题,提出了一种新的无网格方法与有限元耦合法。Belytschko提出的方法的缺点是,无网格方法子域和有限元法子域的界面必须是规则的,交界域内有限元不能随意划分,交界域内无网格方法的节点也不能随意分布。Huerta提出的方法的缺点是对交界域内无网格方法的节点影响域可能无法覆盖交界域。本文提出的无网格方法与有限元耦合法解决了以上两种方法存在的问题,并保留了无网格方法随意配点的优点、交界面可以不规则、提高了无网格子域内的求解精度,从而提高问题的整体求解精度。然后,建立了弹性力学的无网格方法与有限元法的耦合法。最后给出了数值算例。 相似文献
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为提高三维体积成形有限元分析软件的计算精度、减少网格数量,基于六面体网格特性研究了六面体网格体积成形有限元分析系统的关键技术,通过对STL文件的索引重构建立了模具实体模型顶点和三角形面片拓扑连接关系,提出了一种局部坐标系建立方法保证触模和对称约束条件的正确施加,给出了相对速度和相对位置两种节点触模判断方法,并提出了调整触模节点位置的最短距离法,与初矢修正法和原长修正法比较,其调整距离短,体积损失小.基于以上技术,开发了基于三维六面体网格的体积成形有限元分析系统,对典型体积成形工艺进行了有限元模拟,并与Deform模拟结果进行对比,二者吻合较好,验证了所建立模型与相应处理技术的可行性. 相似文献
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网格曲面中孔洞的光滑填充算法研究 总被引:14,自引:0,他引:14
三角网格模型是几何描述的一种重要形式,有着广泛的应用。但三角网络模型常常会存在孔洞缺陷。这些孔洞的存在一方面影响视觉效果,另一方面会影响许多后续的操作,如快速原型制造、有限元分析等,因此有必要对这些孔洞进行修补。目前绝大多数孔洞填充算法是将网格模型中的孔洞提取成空间多边形,并对孔洞多边形进行三角化。这种处理方法的主要缺陷是没有考虑网格曲面在孔洞附近的几何形态,因而填充部分不能与整个曲面光滑地融为一体。笔者提出了一种三角网格曲面中孔洞的光滑填充算法。该算法根据孔洞周围网格曲面的几何信息来增加孔洞内部的采样点,然后再对增加的采样点进行三角化,较好地解决了填充部分与整体曲面光滑连接的问题。 相似文献
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N P Weatherill 《Sadhana》1991,16(1):1-45
In recent years there has been much research activity in the field of compressible flow simulation for aerodynamic applications.
In the 1970’s and 1980’s the advances in the numerical solution of the Full Potential and Euler equations made, in principle,
the inviscid flow simulation around complex aerodynamic shapes possible. At this stage much attention was focused on methods
capable of generating meshes on which such calculations could be performed.
In this paper an overview is presented of some techniques which have been developed to generate meshes for aerospace applications.
Structured mesh generation techniques are discussed and their application to complicated shapes utilising the multiblock approach
is highlighted. Unstructured mesh generation methods are also discussed with particular emphasis given to the Delaunay triangulation
method. Finally, the advantages and disadvantages of the structured and unstructured approaches are discussed and new work
is presented which attempts to utilise both these approaches in an efficient and flexible manner.
An erratum to this article is available at . 相似文献
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《IEEE transactions on magnetics》2009,45(3):992-995
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An AMG Preconditioner for Solving the Navier-Stokes Equations with a Moving Mesh Finite Element Method 下载免费PDF全文
AMG preconditioners are typically designed for partial differential equation
solvers and divergence-interpolation in a moving mesh strategy. Here we introduce an
AMG preconditioner to solve the unsteady Navier-Stokes equations by a moving mesh
finite element method. A $4P1$ − $P1$ element pair is selected based on the data structure
of the hierarchy geometry tree and two-layer nested meshes in the velocity and pressure. Numerical experiments show the efficiency of our approach. 相似文献
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Yasushi Ito P. Corey Shum Alan M. Shih Bharat K. Soni Kazuhiro Nakahashi 《International journal for numerical methods in engineering》2006,65(6):943-973
In this paper, we propose efficient and robust unstructured mesh generation methods based on computed tomography (CT) and magnetic resonance imaging (MRI) data, in order to obtain a patient‐specific geometry for high‐fidelity numerical simulations. Surface extraction from medical images is carried out mainly using open source libraries, including the Insight Segmentation and Registration Toolkit and the Visualization Toolkit, into the form of facet surface representation. To create high‐quality surface meshes, we propose two approaches. One is a direct advancing front method, and the other is a modified decimation method. The former emphasizes the controllability of local mesh density, and the latter enables semi‐automated mesh generation from low‐quality discrete surfaces. An advancing‐front‐based volume meshing method is employed. Our approaches are demonstrated with high‐fidelity tetrahedral meshes around medical geometries extracted from CT/MRI data. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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Majidreza Nazem Daichao Sheng John P. Carter 《International journal for numerical methods in engineering》2006,65(7):1002-1027
This paper first discusses alternative stress integration schemes in numerical solutions to large‐ deformation problems in hardening materials. Three common numerical methods, i.e. the total‐Lagrangian (TL), the updated‐Lagrangian (UL) and the arbitrary Lagrangian–Eulerian (ALE) methods, are discussed. The UL and the ALE methods are further complicated with three different stress integration schemes. The objectivity of these schemes is discussed. The ALE method presented in this paper is based on the operator‐split technique where the analysis is carried out in two steps; an UL step followed by an Eulerian step. This paper also introduces a new method for mesh refinement in the ALE method. Using the known displacements at domain boundaries and material interfaces as prescribed displacements, the problem is re‐analysed by assuming linear elasticity and the deformed mesh resulting from such an analysis is then used as the new mesh in the second step of the ALE method. It is shown that this repeated elastic analysis is actually more efficient than mesh generation and it can be used for general cases regardless of problem dimension and problem topology. The relative performance of the TL, UL and ALE methods is investigated through the analyses of some classic geotechnical problems. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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P. Surya Mohan Prasanth B. Nair Andy J. Keane 《International journal for numerical methods in engineering》2011,85(7):874-895
We present stochastic projection schemes for approximating the solution of a class of deterministic linear elliptic partial differential equations defined on random domains. The key idea is to carry out spatial discretization using a combination of finite element methods and stochastic mesh representations. We prove a result to establish the conditions that the input uncertainty model must satisfy to ensure the validity of the stochastic mesh representation and hence the well posedness of the problem. Finite element spatial discretization of the governing equations using a stochastic mesh representation results in a linear random algebraic system of equations in a polynomial chaos basis whose coefficients of expansion can be non‐intrusively computed either at the element or the global level. The resulting randomly parametrized algebraic equations are solved using stochastic projection schemes to approximate the response statistics. The proposed approach is demonstrated for modeling diffusion in a square domain with a rough wall and heat transfer analysis of a three‐dimensional gas turbine blade model with uncertainty in the cooling core geometry. The numerical results are compared against Monte–Carlo simulations, and it is shown that the proposed approach provides high‐quality approximations for the first two statistical moments at modest computational effort. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Mark F. Adams 《Computational Mechanics》2007,39(4):497-507
Algebraic multigrid (AMG) methods have proven to be effective for solving the linear algebraic system of equations that arise
from many classes of unstructured discretized elliptic PDEs. Standard AMG methods, however, are not suitable for shifted linear
systems from elliptic PDEs, such as discretized Helmholtz operators, due to the indefiniteness of the system and the presence
of low energy modes which are difficult for multigrid methods to resolve effectively. This paper investigates simple methods
to adapt existing standard AMG methods to these shifted systems from direct frequency response analyses in solid mechanics. 相似文献
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Alfio Borzì Giuseppe Borzì 《International journal for numerical methods in engineering》2006,65(8):1186-1196
Three algebraic multigrid (AMG) methods for solving generalized eigenvalue problems are presented. The first method combines modern AMG techniques with a non‐linear multigrid approach and nested iteration strategy. The second method is a preconditioned inverse iteration with linear AMG preconditioner. The third method is an enhancement of the previous one, namely the locally optimal block preconditioned conjugate gradient. Efficiency and accuracy of solutions computed by these AMG eigensolvers are validated on standard benchmarks where part of the spectrum is known. In particular, the problem of isospectral drums is addressed. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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Shengyin Wang Michael Y. Wang 《International journal for numerical methods in engineering》2006,65(11):1892-1922
Level set methods are becoming an attractive design tool in shape and topology optimization for obtaining efficient and lighter structures. In this paper, a dynamic implicit boundary‐based moving superimposed finite element method (s‐version FEM or S‐FEM) is developed for structural topology optimization using the level set methods, in which the variational interior and exterior boundaries are represented by the zero level set. Both a global mesh and an overlaying local mesh are integrated into the moving S‐FEM analysis model. A relatively coarse fixed Eulerian mesh consisting of bilinear rectangular elements is used as a global mesh. The local mesh consisting of flexible linear triangular elements is constructed to match the dynamic implicit boundary captured from nodal values of the implicit level set function. In numerical integration using the Gauss quadrature rule, the practical difficulty due to the discontinuities is overcome by the coincidence of the global and local meshes. A double mapping technique is developed to perform the numerical integration for the global and coupling matrices of the overlapped elements with two different co‐ordinate systems. An element killing strategy is presented to reduce the total number of degrees of freedom to improve the computational efficiency. A simple constraint handling approach is proposed to perform minimum compliance design with a volume constraint. A physically meaningful and numerically efficient velocity extension method is developed to avoid the complicated PDE solving procedure. The proposed moving S‐FEM is applied to structural topology optimization using the level set methods as an effective tool for the numerical analysis of the linear elasticity topology optimization problems. For the classical elasticity problems in the literature, the present S‐FEM can achieve numerical results in good agreement with those from the theoretical solutions and/or numerical results from the standard FEM. For the minimum compliance topology optimization problems in structural optimization, the present approach significantly outperforms the well‐recognized ‘ersatz material’ approach as expected in the accuracy of the strain field, numerical stability, and representation fidelity at the expense of increased computational time. It is also shown that the present approach is able to produce structures near the theoretical optimum. It is suggested that the present S‐FEM can be a promising tool for shape and topology optimization using the level set methods. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献