Kestrel KCFD and FUN3D Results for the Fourth High Lift Prediction Workshop

Abstract

US Air Force digital engineering initiatives require accurate aerodynamic predictions at the edges of the flight envelope, with the ultimate goal to support certification by analysis. AIAA workshops provide an opportunity to exercise DoD tools and processes using community-wide geometry, test cases, and experimental data to understand the tools’ strengths and weaknesses. Results for the Fourth AIAA High Lift Prediction Workshop using the HPCMP CREATETM-AV Kestrel KCFD and NASA FUN3D flow solvers are presented. The accuracy of maximum lift predictions for these flow solvers is mixed. KCFD reasonably predicts the maximum lift using a large, customized mesh, the SARC-DDES turbulence model, and a small time step (resulting in computationally expensive simulations). Other turbulence models and meshes result in under-prediction of the maximum lift due to over prediction of separation on the nacelle (likely due to under-resolution of the chine vortex) and wing root. KCFD under predicts lift at lower angles of attack due to over-prediction of separation on the wing flaps. FUN3D under-predicts lift at the highest angles of attack due to over-prediction of separation on the wing tips (caused by breakdown of the slat bracket wakes), but accurately predicts lift at the lower angles-of-attack. FUN3D results are limited because of problems with some of the provided meshes.