Direct numerical simulation of leading-edge receptivity to sound

Numerical simulations of leading-edge acoustic receptivity are performed fo r a Rat plate with a modified-super-elliptic leading edge. For small freest ream amplitude the agreement between branch I receptivity coefficients pred icted from the direct numerical simulation (DNS) and the experiments for ac oustic waves at zero incidence is excellent. The effect of angle of inciden ce of the impinging wave is investigated and found to produce higher recept ivity coefficients than in the symmetric case. The slope of leading-edge re ceptivity coefficient vs angle of incidence of the impinging wave is found to be less than a of the slope predicted by zero-thickness Rat-plate theory . However, there is excellent agreement between the DNS and finite-nose-rad ius theory. These results clearly demonstrate the importance of including t he effects of the finite nose radius in any receptivity study. Finally, dow nstream of the leading-edge region linear stability theory is found to repr oduce accurately the characteristics of the instability waves. At higher fr eestream forcing, an instability wave generated by nonlinear interaction is found at double the frequency of the forcing.