Prediction Of High-Speed Rotor Noise With A Kirchhoff Formula

A new methodology has been developed to predict the impulsive noise generated by a transonic rotor blade. The formulation uses a full-potential finite-difference method to obtain the pressure field close to the blade. A Kirchhoff integral formulation is then used to extend these finite-dilference results into the far-field. This Kirchhoff foumula is written in a blade-fixed coordinate system. It requires initial data across a plane at the sonic radius. This data is provided by the finite-diference solution. Acoustic pressure predictions show excellent agreement with hover experimental data for two hover cases of 0. 88 and 0. 90 tip Mach number. The latter of which has delocalized transonic fiow. These results represent the first successful prediction technique for peak pressure amplitudes using a computational code.