Solution Adaptation of Unstructured Grids for Two-Dimensional Aerodynamic Computations

A solution-adaptive gridding technique applicable to the numerical solution of the Navier-Stokes equations using unstructured triangular grids is presented and evaluated. Grid adaptation is directed by a parameter based on undivided differences of density and Mach number normalized with their respective grid extrema. A new solution-dependent retriangulation algorithm locally restructures the grid to recover an anisotropic grid following adaptation. The artificial dissipation operator is modified to provide improved accuracy on irregular high aspect ratio triangular grids that may be created in some regions by the adaptive process. The technique is applied to several subsonic and transonic turbulent aerodynamic flows, including the flow over a three-element, high-lift configuration. Grid convergence studies are presented that demonstrate that the grid adaptation procedure leads to significant error reduction in lift and drag coefficient in most circumstances. The effectiveness of the adaptation is significantly improved as a result of the solution-dependent retriangulation and the improved artificial dissipation operator