adapt: massively parallel directional refinement The generation of a high quality mesh for a complex geometry remains a pacing issue in high-fidelity flow simulation. les places strict requirements on mesh resolution, element quality, and even the level of allowed mesh anisotropy. In addition, les meshes are often too large to conveniently manage on even a high-end workstation. adapt is a massively parallel tool developed in Cascade’s solver infrastructure that gives the user detailed control over the local mesh resolution in their grid. The underlying parallel refinement algorithm can refine elements locally to match a target length scale. This target length scale can vary throughout the domain, and can even be different in each direction. Specification of the target length scale can come from expert knowledge of the problem, a desired mesh size limited based
on compute resources, or even from a solution on an unadapted or partially adapted mesh. Different from other adaptation tools, adapt’s patent-pending directional refinement algorithm only refines elements in the direction or directions necessary to meet target lengthscale requirements, dramatically reducing the overall mesh size and also preventing the addition of stiffness to the problem due to excessively small elements. The adapt tool also provides a surface projection algorithm to respect non-planar mesh boundaries during refinement, ensuring accurate representation of the underlying geometry, and allowing the use of very coarse grids as a starting point. adapt has been applied to a wide variety of problems to produce fully-unstructured meshes in parallel at sizes up to 1 billion elements.
Top left: adapt was applied to the block-structured mesh around a fan blade to produce target mesh resolutions in both the blade and tip gap regions. Top right: Starting from a very coarse mesh, adapt was used to produce a target mesh resolution for a nozzle with chevrons. In both cases the curvature of the underlying geometry is respected using adapt’s projection algorithm.
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