Unsteady Lift and Radiated Sound Generated by a 2-D Airfoil in a Single Stream Shear Layer

An airfoil subjected to turbulence in the approach stream radiates sound due to the unsteady lift. Prediction of the spectral density of the unsteady lift requires knowledge of the magnitude and correlation length of the chord normal, or upwash, component of velocity. Additionally, a lift function must be specified based on the geometry of the airfoil. The present research experimentally investigated the sound radiated from a thin airfoil placed in a single stream shear layer. The results indicated a substantial level of agreement between the measured and modeled sound spectra with deviations at low frequencies due to anisotropic turbulence. The high frequency magnitudes were found to match the predictions well only if a thickness correction was applied to the unsteady lift function.