Anisotropic adaptation and multigrid for hybrid grids

An anisotropic refinement method for 2D and 3D hybrid grids is presented and applied to viscous flow problems. The algorithm is unique in that it is not limited to a particular grid structure, e.g. hexahedral elements, but allows the anisotropic division of hexahedra and prisms in 3D, quadrilaterals in 2D and the isotropic division of the other element types. At the core of the method is a novel surface tessellation of an element with hanging nodes which guarantees mesh consistency also in the case of arbitrary directional refinement over an arbitrary number of levels. The efficiency of the anisotropic refinement algorithm is evaluated on viscous flow testcases. The resulting grid sequence is compared to an element‐collapse sequence for its suitability for directionally coarsened multigrid.