Understanding abrupt wing stall with computational fluid dynamics

This paper describes the computational-fluid-dynamics efforts and lessons learned during the four-year Abrupt Wing Stall national research program. The paper details the complex nature of the transonic flows encountered by modern U.S. fighter and attack aircraft during transonic maneuvering conditions. Topics include grid resolution, computational memory and processor requirements, turbulence modeling, steady and unsteady calculations, and Reynolds-averaged Navier-Stokes solutions compared with detached-eddy simulations for this highly complex, viscously dominated, shock-induced, massively separated class of flow. Examples include results obtained for F/A-18C, AV-8B, preproduction F/A-18E, and F-16C aircraft undergoing transonic maneuvering conditions. Various flap settings have been modeled and the computational results compared with extensive wind-tunnel data. The comparisons illustrate the results obtained from both structured and unstructured codes. The utility and accuracy of the various computational solvers is evaluated by qualitative comparisons of surface oil flow and pressure-sensitive-paint results obtained in wind tunnels for some of the models as well as by detailed quantitative pressure coefficient data where experimental results exist. Static lift coefficients are compared between the codes as well as the experimental data for each of the aircraft considered in this study.