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A template-based approach for parallel hexahedral two-refinement

Procedia Engineering

Owen, Steven J.; Shih, Ryan M.

In this work we provide a template-based approach for generating locally refined all-hex meshes. We focus specifically on refinement of initially structured grids utilizing a 2-refinement approach where uniformly refined hexes are subdivided into eight child elements. The refinement algorithm consists of identifying marked nodes that are used as the basis for a set of four simple refinement templates. The target application for 2-refinement is a parallel grid-based all-hex meshing tool for high performance computing in a distributed environment. The result is a parallel consistent locally refined mesh requiring minimal communication and where minimum mesh quality is greater than scaled Jacobian 0.4 prior to smoothing.

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TYPE Conference Poster YEAR 2015
OSTIScopus

Defeaturing CAD models using a geometry-based size field and facet-based reduction operators

Engineering with Computers

Quadros, William R.; Owen, Steven J.

We propose a method to automatically defeature a CAD model by detecting irrelevant features using a geometry-based size field and a method to remove the irrelevant features via facet-based operations on a discrete representation. A discrete B-Rep model is first created by obtaining a faceted representation of the CAD entities. The candidate facet entities are then marked for reduction using a geometry-based size field. This is accomplished by estimating local mesh sizes based on geometric criteria. If the field value at a facet entity goes below a user-specified threshold value then it is identified as an irrelevant feature and is marked for reduction. The reduction of marked facet entities is performed using various facet operators. Care is taken to retain a valid geometry and topology of the discrete model throughout the procedure. The original model is not altered as the defeaturing is performed on a separate discrete model. Associativity between the entities of the discrete model and that of original CAD model is maintained in order to decode the attributes and boundary conditions applied on the original CAD entities onto the mesh via the entities of the discrete model. Example models are presented to illustrate the effectiveness of the proposed approach. © Springer-Verlag London Limited 2012.

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TYPE Conference YEAR 2012
OSTIScopus

Parallel octree-based hexahedral mesh generation for eulerian to lagrangian conversion

Owen, Steven J.; Staten, Matthew L.

Computational simulation must often be performed on domains where materials are represented as scalar quantities or volume fractions at cell centers of an octree-based grid. Common examples include bio-medical, geotechnical or shock physics calculations where interface boundaries are represented only as discrete statistical approximations. In this work, we introduce new methods for generating Lagrangian computational meshes from Eulerian-based data. We focus specifically on shock physics problems that are relevant to ASC codes such as CTH and Alegra. New procedures for generating all-hexahedral finite element meshes from volume fraction data are introduced. A new primal-contouring approach is introduced for defining a geometric domain. New methods for refinement, node smoothing, resolving non-manifold conditions and defining geometry are also introduced as well as an extension of the algorithm to handle tetrahedral meshes. We also describe new scalable MPI-based implementations of these procedures. We describe a new software module, Sculptor, which has been developed for use as an embedded component of CTH. We also describe its interface and its use within the mesh generation code, CUBIT. Several examples are shown to illustrate the capabilities of Sculptor.

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TYPE SAND Report YEAR 2010
DOIOSTI

An adaptive grid-based all hexahedral meshing algorithm based on 2-refinement

Owen, Steven J.

Most adaptive mesh generation algorithms employ a 3-refinement method. This method, although easy to employ, provides a mesh that is often too coarse in some areas and over refined in other areas. Because this method generates 27 new hexes in place of a single hex, there is little control on mesh density. This paper presents an adaptive all-hexahedral grid-based meshing algorithm that employs a 2-refinement method. 2-refinement is based on dividing the hex to be refined into eight new hexes. This method allows a greater control on mesh density when compared to a 3-refinement procedure. This adaptive all-hexahedral meshing algorithm provides a mesh that is efficient for analysis by providing a high element density in specific locations and a reduced mesh density in other areas. In addition, this tool can be effectively used for inside-out hexahedral grid based schemes, using Cartesian structured grids for the base mesh, which have shown great promise in accommodating automatic all-hexahedral algorithms. This adaptive all-hexahedral grid-based meshing algorithm employs a 2-refinement insertion method. This allows greater control on mesh density when compared to 3-refinement methods. This algorithm uses a two layer transition zone to increase element quality and keeps transitions from lower to higher mesh densities smooth. Templates were introduced to allow both convex and concave refinement.

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TYPE Conference YEAR 2010
OSTI

A comparison of mesh morphing methods for shape optimization

Owen, Steven J.; Staten, Matthew L.

The ability to automatically morph an existing mesh to conform to geometry modifications is a necessary capability to enable rapid prototyping of design variations. This paper compares six methods for morphing hexahedral and tetrahedral meshes, including the previously published FEMWARP and LBWARP methods as well as four new methods. Element quality and performance results show that different methods are superior on different models. We recommend that designers of applications that use mesh morphing consider both the FEMWARP and a linear simplex based method.

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TYPE Conference YEAR 2010
OSTI

Unconstrained plastering : all-hexahedral mesh generation via advancing front geometry decomposition (2004-2008)

Kerr, Robert A.; Owen, Steven J.; Blacker, Ted D.

The generation of all-hexahedral finite element meshes has been an area of ongoing research for the past two decades and remains an open problem. Unconstrained plastering is a new method for generating all-hexahedral finite element meshes on arbitrary volumetric geometries. Starting from an unmeshed volume boundary, unconstrained plastering generates the interior mesh topology without the constraints of a pre-defined boundary mesh. Using advancing fronts, unconstrained plastering forms partially defined hexahedral dual sheets by decomposing the geometry into simple shapes, each of which can be meshed with simple meshing primitives. By breaking from the tradition of previous advancing-front algorithms, which start from pre-meshed boundary surfaces, unconstrained plastering demonstrates that for the tested geometries, high quality, boundary aligned, orientation insensitive, all-hexahedral meshes can be generated automatically without pre-meshing the boundary. Examples are given for meshes from both solid mechanics and geotechnical applications.

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TYPE Conference YEAR 2010
OSTI

Embedding features in a cartesian grid

Proceedings of the 18th International Meshing Roundtable, IMR 2009

Owen, Steven J.; Shepherd, Jason F.

Grid-based mesh generation methods have been available for many years and can provide a reliable method for meshing arbitrary geometries with hexahedral elements. The principal use for these methods has mostly been limited to biological-type models where topology that may incorporate sharp edges and curve definitions are not critical. While these applications have been effective, robust generation of hexahedral meshes on mechanical models, where the topology is typically of prime importance, impose difficulties that existing grid-based methods have not yet effectively addressed. This work introduces a set of procedures that can be used in resolving the features of a geometric model for grid-based hexahedral mesh generation for mechanical or topology-rich models.

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TYPE Conference YEAR 2009
OSTIScopus

pCAMAL: An embarrassingly parallel hexahedral mesh generator

Proceedings of the 16th International Meshing Roundtable, IMR 2007

Pébay, Philippe P.; Stephenson, Michael B.; Fortier, Leslie A.; Owen, Steven J.; Melander, Darryl J.

This paper describes a distributed-memory, embarrassingly parallel hexahedral mesh generator, pCAMAL (parallel CUBIT Adaptive Mesh Algorithm Library). pCAMAL utilizes the sweeping method following a serial step of geometry decomposition conducted in the CUBIT geometry preparation and mesh generation tool. The utility of pCAMAL in generating large meshes is illustrated, and linear speed-up under load-balanced conditions is demonstrated.

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TYPE Conference YEAR 2008
ScopusOSTI
Results 51–100 of 112
Results 51–100 of 112