Effects of non-linear eddy-airfoil interactions on the acoustic radiation of a thin wing

Abstract

We study the combined effects of flow unsteadiness (incident vorticity) and external forcing (leading edge animation) on the vibroacoustic radiation of a thin rigid wing. Applying potential flow theory, non-linear coupling between wing motion and flow vorticity trajectory is calculated using the method of conformal mapping. At first, the dynamical problem is formulated and studied. The dynamical description then serves as an effective source term to evaluate the acoustic field. The formulation of the aeroacoustic problem is based on a compact-body acoustic analogy, thus avoiding the traditional difficulty in obtaining the weak acoustic far field from direct numerical simulations. The results identify the airfoil as a dipole-type source, and analyse the significance of non-linear eddy-airfoil coupling on the system acoustic signature. The effect of adding elastic degrees of freedom to the wing, in the form of “passive” linear and torsional springs, is analysed as a mean for monitoring the system acoustic radiation.