The Effects of Low Level Free Stream Turbulence on the Aerodynamic Efficiency of Two Dimensional Wings

Lift and pitching moment coefficients are determined for a symmetrical NACA 0012 and an asymmetrical NASA LS(1)-0417 for free stream turbulent intensities, u_rms /U equal to 0.005 and 0.015. The tests are performed at Reynolds numbers based on chord length equal to 150,000 and 500,000 in an open return, closed test section type wind tunnel. Velocity information is obtained via laser Doppler and hot wire anemometry techniques. The lift coefficients, C_ℓ for both airfoils decrease approximately 15% at each angle of attack at the higher turbulence level. The maximum C_ℓ, however, is increased as is the stall angle. Also, the pitching moment coefficients became more positive with respect to the quarter chord.

The integral scale of the free stream turbulence is approximately 1.5 cm.