Effect of leading-edge geometry and aerodynamic loading on receptivity to acoustic disturbances.

A theoretical analysis is presented for the effects of the nose radius and aerodynamic loading of a body on leading-edge receptivity. We consider linear, time-harmonic disturbances to a two-dimensional, low Mach number flow past a cambered airfoil with parabolic leading edge. Asymptotic methods based on large Reynolds number are used, supplemented by numerical results. The body nose radius enters the theory through a Strouhal number S, and the mean aerodynamic loading enters the theory through a leading-edge loading parameter μ. For most values of μ, the receptivity level decreases with increasing S. At fixed S, the introduction of modest aerodynamic loading produces a reduction in receptivity, but as the loading is increased towards the point at which the mean boundary-layer flow separates, a marked increase in receptivity coefficient is observed. Obliquely incident acoustic waves are found to produce much higher receptivity levels than parallel waves.