ON THE PREDICTION OF “BUZZ-SAW” NOISE IN AERO-ENGINE INLET DUCTS

“Buzz-saw” noise radiated from an aero-engine inlet duct occurs when the relative speed of the inlet flow impinging on the fan blades is supersonic. The pressure field attached to a supersonic ducted fan, in a direction normal to the shock fronts, closely resembles a sawtooth waveform. The non-linear propagation of a high-amplitude sawtooth waveform spiralling around a duct is calculated by two numerical simulation models. The models and their validation are discussed critically. Results are presented comparing the numerical simulations with experimental data. Overall there is good agreement comparing the results of the simulations with the experimental data, and in particular, the “Buzz-saw” noise in a hard-walled aero-engine inlet duct is successfully predicted.