Prediction of Transition and Compressibility Effects on Dynamic Stall over OA209 Airfoil

Abstract

The effects of boundary-layer transition and compressibility were numerically predicted for an OA209 airfoil in dynamic stall conditions. Effects of reduced frequency and Mach number on the generation of separation bubbles were investigated. Leading edge separations were found to correlate with the compressibility, relating to the beginning and ending of the stall process. The local Mach number in the leading edge was seen to decrease as the reduced frequency increases. The development of the dynamic stall vortex correlated with the reduced frequency, relating to the strength of the unsteady effect and stall characteristics. It was also found that the laminar separation bubble influences the strength of unsteady effects during the lift overshoot and the reattachment process.