Numerical Investigation of Aerodynamic Hysteresis for Transonic Flow Over a Supercritical Airfoil

A computational study is performed to investigate transonic flow over supercritical airfoil RAE 2822. In this study, Reynolds averaged Navier Stokes equations (RANS) with Spalart-Allmaras turbulence model have been applied. Results have been well validated with available experimental data. Results showed that the coefficients of lift and drag are not single valued functions of angle of attack, rather they assume multiple values regarding the increasing or decreasing trend of angle of attack. Depending on the increasing and decreasing processes, the lift and drag coefficients differ at same angle of attack. Consequently a hysteresis loop is formed. This hysteresis is closely related to the laminar boundary layer separation and transitions on airfoil. The flow exhibits noticeable ability to remember its past history. This memory of the flow is responsible for the hysteresis.