Experimental Characterization of the Effects of Freestream Turbulence Intensity on the SD7003 Airfoil at Low Reynolds Numbers

The effect of freestream turbulence intensities ranging from Tu = 1.26% to Tu = 3.2% is studied. Skin friction measurements made on the surface of the airfoil using oil film interferometry (OFI) show that, in general, the effect of the increased Tu is to inhibit separation of the laminar boundary layer. With increased Tu, the near-wall flow experiences strong deceleration in the adverse pressure gradient, but does not reverse as it does in the baseline case where Tu = 0.05%. The Cp distribution resulting from this decelerated fluid is similar in appearance to that of a laminar separation bubble. OFI results also show that laminar separation initiates a more rapid transition process than does higher turbulence intensity: transition of the boundary layer occurs over a shorter distance with Tu = 1.26% than it does with Tu = 2.19% due to the presence of a LSB at the lower turbulence intensity.M.A.S