Correlating a High-Lift Airfoil Performance with Turbulence Strain Rate

The performance of a high-lift airfoil (S1223) has been correlated to the free-stream turbulence strain rate at Reynolds numbers Re = 55,000, 75,000 and 100,000 in a wind tunnel. A comprehensive examination of the lift/drag data, wake velocity deficits, wake turbulence level and power density spectra revealed that the flow patterns above and below the airfoil are significantly altered and the boundary layer separation is delayed to higher angles of attack with increasing turbulence strain rate. That is to say, high straining turbulent wind tends to improve the airfoil performance by suppressing the stall and lowering the drag, at a small cost of a marginally reduced maximum lift coefficient.