When creating a #CFD mesh there are three main categories of cell types that can be used— hexahedral, tetrahedral or polyhedral.
Hexahedral meshes are particularly efficient for wall-bounded flows and flows that are directional, for example flow in a pipe or around an airfoil, as they allow very fine wall-normal spacing without large face skewness. If skewness of these hexahedral cells is minimized, structured grids created with this cell type provide the fastest convergence, best accuracy, and a relatively low cell count. However, for more complex geometric configurations, considerable time and skill is required to create these structured grids.
Tetrahedral grids, on the other hand, lend themselves to automatic meshing of very complex fluid volumes however at the expense of very high cell counts (typically 3-4 times higher) and convergence can be challenging due to skewness, lack of neighbouring cells and the non-orthogonal nature of the resulting grid.
Finally, polyhedral meshes by their very nature have more neighbouring cells compared to tetrahedral cells and thus more easily capture gradients with far less cells and can even out-perform hexahedral meshes for recirculating flows.
#simulationsoftware #computationalfluiddynamics #meshing