Shock-Wave Radiation from a Supersonic Ducted Rotor

Abstract

Over the subsonic speed range, the pressure field attached to a ducted rotor decays rapidly with distance away from the rotor. This exponential decay, coupled with the low radiation efficiency of a subsonically rotating pressure pattern, is generally sufficient to bring the radiated sound power well below that produced by interaction of the rotor with disturbances in the flow. This is particularly true for multibladed rotors as used in aircraft-engine fans and compressors, and accounts for the importance of rotor-stator interaction as a source of noise at subsonic tip speeds.