DNS of leading-edge receptivity to sound

Abstract

Numerical simulations of leading-edge acoustic receptivity are performed for a flat plate with a modified-super-elliptic (MSB) leading edge. For small freestream amplitude, the agreement between Branch I receptivity coefficients predicted from the DNS and the experiments of Saric & White (1998) for acoustic waves at zero incidence is excellent. The effect of angle of incidence of the impinging wave is investigated and found to produce higher receptivity coefficients than in the symmetric case. The slope of leading-edge receptivity coefficient versus angle of incidence of the impinging wave is found to be less than 1/4 of the slope predicted by zero-thicknes s flatplate theory. However, there is excellent agreement between the DNS and finite-nose-radius theory of Hammerton & Kerschen (1996). These results clearly demonstrate the importance of including the effects of the finite nose radius in any receptivity study. Finally, downstream of the leading-edge region, linear stability theory is found to accurately reproduce the characteristics of the instability waves. At higher freestream forcing, an instability wave generated by nonlinear interaction is found at double the frequency of the forcing.