1 Fast and Accurate Use of Unstructured CFD Methods to Assess Performance and Aerodynamic Heating of Reusable Launch Vehicles in Hypersonic Flight

program to benchmark computational fluid dynamic (CFD) predicted aerodynamic and aerothermal environments for Reusable Launch Vehicles (RLVs) in hypersonic flight. The defining experimental database was acquired at mostly laminar flow conditions near Mach 14 with a representative RLV model in AEDC Hypervelocity Tunnel Number 9 during the fall of 2007. The CFD calculations were performed using unstructured grids at two levels of fidelity—an Euler analysis to obtain a preliminary estimate of vehicle performance and static stability, and a Navier-Stokes analysis to refine aerodynamic and stability predictions, and to estimate surface heating. The surface grids were generated manually, but robust batch volume grid generators were employed to complete the meshing process. Initial flow solutions with a Riemann solver were contaminated by carbuncle instabilities. However, the meshes were revised to capture the shock within a prismatic layer, resulting in stable and accurate solutions. The Navier-Stokes predictions replicated wind tunnel results with exceptional accuracy for both the macro forces and moments as well as the local surface pressure and heat transfer measurements, but only when the mesh was constructed to avoid carbuncle instabilities. Nomenclature AFRL = Air Force Research Laboratory AoA = angle of attack CD = drag coefficient (wind axis) CFL = Courant, Friedrichs, Lewy parameter, u * t / x CL = lift coefficient (wind axis) CM = pitching moment coefficient (wind axis) Cp = center of pressure DoD = Department of Defense L/D = lift to drag rati