Comparison of Fixed and Adaptive Unstructured Grid Results for Drag Prediction Workshop 6

Fixed and adapted grid solutions on the NASA Common Research Model (CRM) in wing-body (WB) and wing-body-nacelle-pylon (WBNP) configurations are compared for three Reynolds-averaged Navier-Stokes flow solvers. The flow solvers were run on a sequence of fixed unstructured grids built for the 6th AIAA CFD Drag Prediction Workshop (DPW-6) and compared with solutions generated on solution adaptive grids. The fixed and adaptive mesh generation processes and resulting grids and solutions are presented and discussed. Both approaches achieve asymptotic grid convergence of less than two counts of drag. The fixed grid approach is based on gridding guidelines developed over many years of CFD application experience on similar applications and required an expert user several weeks of effort to develop a grid family conforming to the guidelines. In contrast, the adaptive grid approach is automatic, relying on an estimate of solution discretization error to guide grid construction. The adaptive grids were generated with less than 2 days of user interaction, requiring very few user decisions and almost no expert knowledge.