The Effect of Turbulence on the Aerodynamics of Low Reynolds Number Wings

Tests on 3-D and nominally 2-D airfoils are presented relevant to micro air vehicle (MAV) flight. Thin, pressure-tapped, flat airfoils were testing at a Reynolds number of 75000 under a range of turbulence characteristics. Turbulence intensity was varied from 1.2 to 12.6% and the longitudinal integral length scale was varied from 0.17 to 1.21m. The overall trend when the intensity was increased was to reduce the lift curve slope but increase the maximum lift coefficient. When the length scale was increased and the intensity was held nominally constant, the lift curve slope increased and the maximum lift coefficient reduced. The largest variation in lift with increasing intensity was found at between 5 and 10 degrees where a reduction in lift of up to 28% was found. Spectograms of the pressure fluctuations gave insight into the behavior of the laminar separation bubble under the influence of turbulence.