Third Drag Prediction Workshop Results Using the NSU3D Unstructured Mesh Solver

Results from the third AIAA drag prediction workshop on using the unstructured mesh Reynolds-averaged Navier-Stokes solver NSU3D are presented. Computations include a grid convergence study on a transonic wing-body and wing-body-fairing configuration at a fixed C L condition using grids up to 41 million points, as well as an incidence sweep (drag polar) at fixed Mach and Reynolds numbers. A second set of results on a pair of closely related wing geometries is also described, including a grid convergence study at a fixed incidence and an incidence sweep (drag polar) for both wing geometries. For all cases, approximate second-order-accurate grid convergence characteristics are demonstrated, with overall accuracy and efficiency comparable with other structured, overset, and unstructured workshop calculations. However, it is found that differing grid-converged results may be inferred based on different families of self-similar coarse and fine-grid sequences, particularly for values such as absolute drag at a fixed incidence. More consistent grid convergence for idealized drag values (omitting induced drag) is observed, thus validating the procedure of performing grid convergence studies at a fixed C L . These grid convergence issues are attributed to the large range of disparate scales that must be resolved in aerodynamic flows, and they point to the need for further advances in quantifying and resolving discretization errors for such problems.