A COMPARISON OF COMPUTATIONAL AEROACOUSTIC PREDICTION METHODS

This paper compares two methods for predicting the noise from helicopt er rotors in forward flight. Both methods use a computational fluid dy namics (CFD) solver for the Euler equations to predict the aerodynamic and acoustic solutions in the near field. The first method propagates the near-field noise using the acoustic analogy without quadrupole te rms. The second method uses a Kirchhoff integration to propagate the n ear-field rotor noise to the far held. Computed results from both meth ods are compared with each other and with experimental data for test c ases with both high-speed impulsive and blade-vortex interaction noise . Computed results show that both methods give similar results for cas es where there is no transonic flow over the rotor blades. For higher- speed cases with transonic flow, the Kirchhoff method gives more accur ate results. Both acoustic prediction methods require similar computat ional resources, but these requirements are small when compared to tho se of the CFD now solver.