자유유동 난류강도에 따른 익형 위 후류유도 경계층 천이의 거동

Abstract

Wake-induced boundary-layer transition on a NACA0012 airfoil with zero angle of attack is experimentally investigated in periodically passing wakes under the moderate level of free-stream turbulence. The periodic wakes are generated by rotating circular cylinders clockwise or counterclockwise around the airfoil. The free-stream turbulence is produced by a grid upstream of the rotating cylinder, and its intensities at the leading edge of the airfoil are 0.5 and 3.5%, respectively. The Reynolds number (Rec) based on chord length (C) of the airfoil is , and Strouhal number (Stc) of the passing wake is about 1.4. Time- and phase-averaged streamwise mean velocities and turbulence fluctuations are measured with a single hot-wire probe, and especially, the corresponding wall skin friction is evaluated using a computational Preston tube method. The patch under the high free-stream turbulence $(Tu_{\infty}