Introduction

Air traffic has increased constantly in the past and will continue to grow. Consequently, the noise nuisance from aircraft has become a significant concern that has led to increasing interest in design of quiet aircraft and aero-engines. With modern high-bypass-ratio engines, jet noise has been significantly reduced and other engine noise sources have become dominant. The most significant of these sources is the tonal fan noise which propagates upstream through the engine intake and downstream through the bypass duct and radiates into the far-field. In order to obtain further reductions in engine noise, investigations into fan noise are necessary. The intention of this paper is to present approaches for the numerical simulation of tonal noise propagation and radiation which do not incur unreasonable computational expense. The techniques are formulated such that they can be used as tools for the design of low-noise engines through the provision of time-efficient far-field predictions for different fan noise sound sources. The results presented were originally achieved in various projects, including DFG SWING+, EC TurboNoiseCFD.