A 3D unstructured Navier-Stokes solver with multigrid on adaptive hexahedral meshes

A 3D Navier-Stokes server for unstructured meshes consisting of hexahedra only is presented. An efficient adaptation algorithm allows to build up the meshes from a very coarse level. A cell-centered approach is used which allows to deal with hanging nodes. The management of the unstructured data and of the adaptation is facilitated by using Fortran 90. The use of hexahedra allows to incorporate numerical schemes, developed for structured codes, with a minimum of changes and avoids the use of more expensive reconstruction type schemes. Multigrid and residual smoothing are used for enhanced efficiency. The multigrid is based on a zonal coarse approach, avoiding problems with conservation along boundaries between unrefined and refined regions. Results art: shown for a 2D and a 3D Navier-Stokes test case.