A parametric study of mean loading effects on airfoil gust interaction noise

The influence of airfoil mean loading parameters on the sound generated by interaction with short wavelength vorticity and entropy gusts is examined. It is found that there are two mean flow parameters of importance, the effective leading edge incidence angle and the airfoil lift coefficient. The former controls the total sound power level, while the latter has an important effect on the directivity pattern. For vorticity gusts, positive gust angles result in noise levels which increase with leading edge loading (LEL), while for negative gust angles an increase in LEL may actually reduce the noise level. For low levels of LEL, entropy gusts generate less sound than vorticity gusts, while for larger values of LEL, entropy gusts are at least as important as vorticity gusts.