Linear acoustic solutions of propeller noise problems: analysis and treatment of transonic singularity

Three different patterns are used to show some characteristic features of sound pressure field generated by rotating blades at supersonic speed. The techniques are based on the solution of the Ffowcs Williams-Hawkings (FW-H) equation as proposed by Farassat in several papers. The first method is used here to provide the time history of the pressure perturbation: this exhibits, at particular nstants, very high intensity; the second one is applied to visualize areas on the blade surface where the acoustic source functions may be magnified by kinematic effects; the third method is finally exploited to recognize the influence of those effects on the resulting pressure waveform.