Quality improvements in extruded meshes using topologically adaptive generalized elements

Abstract

In this dissertation, a novel method to extrude near-body meshes from surface meshes of arbitrary topology that exploits topologically adaptive generalized elements to improve mesh quality is presented. Specifically, an advancing layer algorithm to generate nearbody meshes which are appropriate for viscous fluid flows is discussed. First, an orthogonal two-layer algebraic reference mesh is generated. The reference mesh is then smoothed using a locally three-dimensional Poisson-type mesh generation equation that is generalized to smooth extruded meshes of arbitrary surface topology. Local quality improvement operations such as edge collapse, face refinement, and local reconnection are performed in each layer to drive the mesh toward isotropy. An automatic marching thickness reduction algorithm is used to extrude from multiple geometries in close proximity. A global face refinement algorithm is used to improve the transition from the extruded mesh to the void-filling tetrahedral mesh. A few example meshes along with quality plots are presented to demonstrate the efficacy of the algorithms developed. ACKNOWLEDGMENTSThe author wishes to express his sincere appreciation to Dr. David S. Thompson, who acted as a major advisor and the director of my dissertation. His constant support and encouragement has given me an opportunity to learn, and grow professionally. I am indebted for his suggestions and guidance through out the dissertation work. It is hard to find enough words to express my appreciation for his patience shown towards me in many issues and guiding me to go in proper direction.I want to thank my committee members Dr.

On the use of general elements in fluid dynamics simulations

“…However, Knupp [22] points out that facebased element quality estimates may not be adequate in some cases. We have made a preliminary The near-body mesh generation algorithm of Chalasani and Thompson [7] is an advancing layertype approach that generates a semistructured mesh by extruding from a surface mesh of arbitrary topology. Since generating surface meshes is labour intensive, the objective was to develop a mesh extrusion algorithm that would work with any 'reasonable' surface mesh.…”

“…One application of general elements that has received interest in the literature is their use locally in extruded meshes to improve quality [4][5][6][7]. Such an extruded mesh is typically employed as the near-body component of a hybrid mesh [8,9] near viscous boundaries.…”

“…In this paper, we describe two mesh generation strategies that utilize general elements [7,13] as well as how a specific flow solver [3] is structured to handle general elements. We present results for two configurations to demonstrate the effectiveness of our approach and make recommendations for future work.…”

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“…The meshes generated by the solid mesher are not appropriate for fluid simulation since highly anisotropic elements are desirable for simulating viscous fluid flows in regions near no-slip boundaries, i.e., boundary layers. Therefore, we use the Generalized 3D Mesher [6,5], which generates high-quality meshes consisting of extruded triangular prisms, tetrahedral elements, and generalized prisms, starting from the surface mesh. This code was implemented by David Thompson's group at Mississippi State University (MSU), and it is one of the pre-existing components used in our project.…”

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“…For such problems, topological adaptivity -using cell types that are locally appropriate for the region being discretized -offers an attractive alternative to traditional structured multi-block grids or unstructured tetrahedral meshes. Chalasani et al [6,5] have exploited this idea to generate high quality meshes consisting of extruded triangular prisms, tetrahedral elements, and generalized prisms.…”