Anisotropic Grid Adaptation on Unstructured Meshes

A grid adaptation method based on the solution Hessian is described. Adaptation is implemented by minimizing the differences between the cell edge lengths in a metric space. Grid refinement, coarsening, connectivity modifications and point movement are used to adapt the grid. Particular attention is given to points of inflection and zero gradient where the Hessian goes to zero and to solutions discontinuities across which the Hessian does not exist. Appropriate control of these critical points enables the generation of anisotropic cells that are aligned with dominant solution features. Representative results for boundary layers and high Reynolds number flows at subsonic, transonic and supersonic conditions are given to demonstrate the method.