Method to generate complex computational meshes efficiently

2011

To provide simulation software in the field of TCAD with the utmost flexibility regarding generation and adaptation of meshes, a generic and high-quality meshing library, ViennaMesh, has been developed. The library is coded in C++ and utilizes modern programming techniques to wrap tasks, like mesh generation and mesh adaptation, into functional objects, which can then be concatenated to form the desired meshing process. Additionally, a meta-selection environment provides the ability to select a mesh generation kernel based on properties already defined at compile time. Code examples are depicted and briefly discussed. Moreover, several enhancements to existing mesh adaptation methods have been made, which are demonstrated based on meshes provided by industrial partners.

Computers & Structures, 1988

Some recent efforts on the development of methods to ensun the robustness of automatic thracdimensional mesh generation techniques arc discuss& The topic arcas considered arc mesh entity classification, finite octrcc cell triangulation, and coarse mesh generation by element removal.

IEEE Antennas and Propagation Magazine, 1997

2002

This paper presents a description of the reorganization of a geometric modeler, MG, designed to support new capabilities of a topological module (CGC) that allows the detection of closed-off solid regions described by surface patches in non-manifold geometric models defined by NURBS. These patches are interactively created by the user by means of the modeler's graphics interface, and may result from parametric-surface intersection in which existing surface meshes are used as a support for a discrete definition of intersection curves. The geometry of realistic engineering objects is intrinsically complex, usually composed by several materials and regions. Therefore, automatic and adaptive meshing algorithms have become quite useful to increase the reliability of the procedures of a FEM numerical analysis. The present approach is concerned with two aspects of 3D FEM simulation: geometric modeling, with automatic multi-region detection, and support to automatic finite-element mesh generation.

Computer Methods in Applied Mechanics and Engineering, 2010

This paper describes an automatic and efficient approach to construct unstructured tetrahedral and hexahedral meshes for a composite domain made up of heterogeneous materials. The boundaries of these material regions form non-manifold surfaces. In earlier papers, we developed an octree-based isocontouring method to construct unstructured 3D meshes for a single-material (homogeneous) domain with manifold boundary. In this paper, we introduce the notion of a material change edge and use it to identify the interface between two or several different materials. A novel method to calculate the minimizer point for a cell shared by more than two materials is provided, which forms a non-manifold node on the boundary. We then mesh all the material regions simultaneously and automatically while conforming to their boundaries directly from volumetric data. Both material change edges and interior edges are analyzed to construct tetrahedral meshes, and interior grid points are analyzed for proper hexahedral mesh construction. Finally, edge-contraction and smoothing methods are used to improve the quality of tetrahedral meshes, and a combination of pillowing, geometric flow and optimization techniques is used for hexahedral mesh quality improvement. The shrink set of pillowing schemes is defined automatically as the boundary of each material region. Several application results of our multi-material mesh generation method are also provided.

2007

Abstract: This paper describes an approach to construct unstructured tetrahedral and hexa-hedral meshes for a domain with multiple materials. We have developed an octree-based iso-contouring method to construct unstructured 3D meshes for a single material domain. Based on it, we analyze each material change edge instead of sign change edge to figure out in-terfaces between two materials, and mesh each material region with conforming boundaries. Two kinds of surfaces, the boundary surface and the interface between two different material regions, are meshed and distinguished. Both material change edges and interior edges are an-alyzed to construct tetrahedral meshes, and interior grid points are analyzed for hexahedral mesh construction. Finally the edge-contraction and smoothing method is used to improve the quality of tetrahedral meshes, and a combination of pillowing, geometric flow and optimiza-tion techniques are used for hexahedral mesh quality improvement. The shrink set is def...

Engineering with Computers, 1996

HEXAR, a new software product developed at Cray Research, Inc., automatically generates good quality meshes directly from surface data produced by computeraided design (CAD) packages. The HEXAR automatic mesh generator is based on a proprietary and parallel algorithm that relies on pattern recognition, local mesh refinement and coarsening, and variational mesh smoothing techniques to create all-hexahedral volume meshes. HEXAR generates grids two to three orders of magnitude faster than current manual approaches. Although approximate by design, the resulting meshes have qualities acceptable by many commercial structural and CFD (computational fluid dynamics) software. HEXAR turns mesh generation into an automatic process .for most commercial engineerin 9 applications.

Research in Engineering Design, 1999

This paper presents a method to integrate in a better way the finite element method in the CAD/CAM process for two-dimensional problems, through efficient and automatic meshing and remeshing procedures. During the design step, the lack of integration between geometric modeling and numerical analysis remains a crucial problem and it still tends to restrain the use of finite element methods to a small number of engineers. Here we tackle the problem of the automatic remeshing of an object in the context of minor changes in its geometry and topology without restarting the mesh generation from the beginning. We have developed a mesh generator that is able to adapt a previous mesh, through two complementary strategies (for 2D cases) to a new geometry without destroying the whole initial discretization. We also present the possible extension of these concepts to three-dimensional problems.

International Journal for Numerical Methods in Engineering, 1989

This paper introduces a two-stage algorithm for the automatic conversion of solid models into finitc element meshes. In Stage 1 the solid is approximated by a collection of variably sized cells generated by recursive spatial decomposition and stored in a logical tree. In Stage 2 the approximating cell structure, which includes cells that are wholly inside the solid (IN) as well as cells that are neither inside nor outside (NIO), is transformed into a finite element model. I N cells are directly mapped into finite elements while NIO cells are dccornposed according to their topologically complexity through either template mapping or recursive element extraction. Although specifically designed for adaptive remeshing, the algorithm is of general use and can be implemented in any Solid Modelling System that supports Boolean operations on solids and maintains a complete boundary representation. Core algorithms for Stages 1 and 2 are rigorously developed to insure their applicability within a genuinely automatic procedure. Specific issues related to boundary evaluation and decomposition procedures are identified and discussed. The implementation of the algorithm into an experimental system based on the PADL-2 solid modcller is described. The paper concludes with a comparative study of existing meshing algorithms based on recursive spatial decompositions.

J. Comput. Sci., 2018

The finite element method is a very reliable and precise technique for solving partial differential equations in three-dimensional domains, with relevant applications in several areas. However, 3D simulations by FEM require computer programs for solid modeling and automatic mesh generation and there are few examples of open source codes available and dedicated to these tasks. Unfortunately, these open source codes are not usually conceived to operate together in an integrated fashion, showing distinct life cycles and different origins, which may result in contradictory specifications. In this study, a method is proposed to integrate solid modeling and automatic mesh generation with focus on open source codes and how the quality of FEM simulations can be improved by the improvement of the mesh. The method was structured in desired features for the solid construction and in integration strategies for an automatic mesh generation. The approach was tested in nontrivial domains and with ...

IEEE Transactions on Magnetics, 1990

Devoted to the mesh generation of 3DD-domains, this paper briefly describes difleerent approaches actually in progress. A new method is introduced which can be seen as a variant of the Delaunay-Vomnoi's tessellation coupled with a control of the given boundary used to defined the domain to be meshed.

International Journal for Numerical Methods in Engineering, 1994

Fully automatic three-dimensional mesh generation is an essential and increasingly crucial requirement for finite element solution of partial derivative equations. The results of numerical simulation, more precisely the convergence and accuracy of numerical solutions, closely depends on the quality of the underlying mesh. This work introduces a fully automatic finite element mesh algorithm with simplexes (tetrahedra), adapted to complex geometries described by disctete data. This paper is divided in four sections: (a) brief introduction to discrete geometry is given, as well as the basic definition of the domain of interest; (b) description of the voxel approach to tetrahedronization. The tetrahedronization process uses a divide-and-conquer method, which provides small elements on the boundary of the domain of interest. Voxels of the domain are subdivided according to an automatic procedure, which preserves the topology. Specific rules were introduced which allow reducing the number of voxel configurations to be treated, and consequently the computation time; (c) presentation of results and performances of the mesh algorithms. The resulting algorithm demonstrates an n logn growth rate with respect to the number of elements; (d) optimization of the mesh generation process at hand of a 'finite-octree' type of explicit controlling space.

Computers & Structures, 2009

A new, efficient 3D mesh-generation algorithm, HeMUT (Hexahedral Mesh for Urban Terrains), is presented. HeMUT is developed under .NET and builds unstructured/structured hexahedral meshes. The algorithm focuses on urban terrains and on the mesh generation for the simulation of toxic gases dispersion (finite-element). HeMUT is fully automated, multi-threading and takes advantage of terrain. In addition, it distributes the nodes on the domain by employing a method based on process-design considerations. These features decrease the computational effort and at the same time differentiate this algorithm from all other similar ones. In comparison with a commercial software HeMUT performed well.

Proceedings of the 16th International Meshing Roundtable, 2008

This paper describes an approach to construct unstructured tetrahedral and hexahedral meshes for a domain with multiple materials. In earlier works, we developed an octreebased isocontouring method to construct unstructured 3D meshes for a single-material domain. Based on this methodology, we introduce the notion of material change edge and use it to identify the interface between two or several materials. We then mesh each material region with conforming boundaries. Two kinds of surfaces, the boundary surface and the interface between two different material regions, are distinguished and meshed. Both material change edges and interior edges are analyzed to construct tetrahedral meshes, and interior grid points are analyzed for hexahedral mesh construction. Finally the edge-contraction and smoothing method is used to improve the quality of tetrahedral meshes, and a combination of pillowing, geometric flow and optimization techniques is used for hexahedral mesh quality improvement. The shrink set is defined automatically as the boundary of each material region. Several application results in different research fields are shown.

2004

This document serves the final report for the grant titled "Surface Generation and Cartesian Mesh Support". This completed work was in algorithmic research into automatically generating surface triangulations from CAD geometries. NASA's OVERFLOW and Cavt3D simulation packages use surface triangulations as an underlying geometry description and the ability to automatically generate these from CAD files (without translation) substantially reduces both the wall-clock time and expertise required to get geometry out of CAD and into mesh generation. This surface meshing was exercised greatly during the Shuttle investigation during the last year with success. The secondary efforts performed in this grant involve work on a visualization system cut-cell handling for Cartesian Meshes with embedded boundaries.