UBC Theses and Dissertations
Anisotropic advancing layer mesh generation Earle, Nicholas
The use of computational fluid dynamics (CFD) is now a ubiquitous part of of the engineering design process, especially in aerodynamic applications. The CFD process requires a high-quality volume mesh on which to perform the simulation. However, mesh generation is typically a choke point for the process, and is often the most time-consuming step. This emphasizes the need for robust, automatic mesh generation tools that can reliably produce high-quality meshes. Advancing layer (AL) meshing is one method of mesh generation in which mesh elements are extruded off of the surface mesh one layer at a time. AL meshes are preferred for their unmatched cell alignment, orthogonality, and fraction of prismatic elements. However, two limitations of a standard AL scheme are the handling of complex corners and highly anisotropic surface meshes. This thesis, first, presents a solution to the problem of complex corners, where extruding a single vertex is inadequate. The solution presented is a robust method that essentially modifies the surface mesh by extruding in multiple directions at the corner, then creating adjacent cells, and filling holes. From here it is possible to extrude the mesh as usual. Second, an extension of the AL method is presented which enables extrusion from highly anisotropic surface meshes. Anisotropy is characterized by the use of highly stretched cells in specific areas where the flow physics produce large gradients in one direction but not in one or both of the others, a wing for example. Anisotropic cells allow for the desired mesh resolution but at a fraction of the cell count. The method presented extrudes layers while maintaining the anisotropic pseudo-structure and aspect ratio of the surface mesh and allows for a smooth transition back to regular isotropic extrusion. It is accomplished by exploiting the anisotropic pseudo-structure to decimate entire lines of vertices at once and adjusting the smoothing algorithm to maintain distance ratios between neighbouring vertices. This method demonstrates AL's ability to produce high-quality anisotropic meshes, opening a wide array of meshing possibilities.
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