Open rotor centrebody scattering

Abstract

This paper investigates the effect of acoustic scattering from the centrebody of an advanced open rotor engine. The physical mechanisms governing the scattering process are investigated and formulae for predicting noise levels are presented. It is found that centrebody scattering has a negligible effect on rotor-alone tones produced by a subsonic rotor, however, the scattering effect can be significant for rotor-alone tones produced by a supersonic rotor and certain rotor–rotor interaction tones. The paper concludes with an analysis which shows that the centrebody scattered field may be significantly reduced by applying an acoustic liner to the centrebody surface.