Automatic Hex-Dominant Mesh Generation for Complex Flow Configurations

A method for automatically generating hex-dominant meshes for Computational Fluid Dynamics (CFD) applications is presented in this article. Two important regions of the mesh for any CFD simulation are the interior mesh and the boundary layer mesh. The interior mesh needs to be fine in the critical flow regions to ensure accurate solutions. The proposed method uses Bubble Mesh algorithm which packs bubbles inside the geometry to generate the mesh nodes. Algorithm was tested for sample flow problems and improvements were made to interior and boundary layer mesh generation methods. The interior mesh is generated using directionality and sizing control functions specified on the points of a 3D grid generated over the entire geometry. This offers a flexible control over mesh sizing and local mesh refinement. Boundary layer mesh is important to accurately model the physics of boundary layer near the geometry walls. In the proposed method, boundary elements in the mesh are split into multiple divisions with the first division having the smallest thickness to ensure it lies inside the physical boundary layer. The rest of the layers expand linearly in thickness until they match in value with the interior mesh size. Hex-dominant meshes were created for two different flow geometries. Flow simulations were performed in open-source code OpenFOAM and predictions were compared with available experimental data.