An Experimental Study of Circulation Control on an Elliptic Airfoil

Circulation control uses the Coanda effect to generate high lift but can produce significant acoustic self-noise. The purpose of the study is therefore to gain insight on the flow mechanisms responsible for the observed tonal and broadband noise reported in Wetzel et al. 2009. The results of high-resolution particle image velocimetry measurements of a 2-D, 20% thick elliptical circulation control airfoil with single-slot blowing are described. Data are presented for the following subset of test conditions: zero angle of attack, Rec = 0.65M, h/c = 0.0019, Cμ = 0, 0.015, and 0.057. Together with complementary Cp data, local flow scales are extracted from the velocity data to aid in identifying the contribution of each broadband noise source to the overall circulation control acoustic spectrum.