Wall-Resolved Large-Eddy Simulation of Near-Stall Airfoil Flow at Rec=107

A wall-resolved large-eddy simulation (LES) of the near-stall flow around the Aerospatiale A-airfoil at Rec=1.0x10(7) is conducted. The present LES shows typical Reynolds-number effects compared to the previous LES at Rec=2.1x10(6), such as the increase in lift coefficient, decrease in boundary-layer thickness, delay of turbulent flow separation, and upstream shift of transition location. Among these Reynolds-number effects, the difference in the development of momentum displacement thickness is focused on and further analyzed based on the integral relation of the boundary layer. This analysis reveals that the different mechanisms of the laminar-turbulent transition between the two Reynolds-number cases cause an initial difference in the momentum displacement thickness. This initial difference is then amplified downstream by the deceleration effects of the mean flow. These results suggest that proper estimation of the laminar and transitional flows near the leading edge is crucial for predicting the trailing-edge stall phenomena and their dependency on the Reynolds number.