Airframe related aeroacoustics of transport aircraft� -research into prediction and reduction of sound radiation-�

Kurzfassung

As the sound generation in turbofan engines has decreased the significance of airframe related sound has increased. For example in landing approach the sound associated with the airframe may even dominate the overall sound radiation of an aircraft. The influence of the airframe on aerosound is threefold: i) Airframe components subjected to either their own turbulent boundary layer flow or to installation related turbulent flow act as sources of sound, ii) The aerodynamic influence of the airframe may considerably change the sound generation of the propulsion system, in particular of propellers, iii) the airframe may change the radiation characteristics of engine noise due to reflection and diffraction of the sound waves at the aircraft surface as well as refraction and scattering effects of the vortical flow in its vicinity. The presentation gives an overview about prominent sources of airframe component noise as well as acoustic and source installation effects related to the airframe. Results of research at DLR are presented on the numerical and experimental simulation of airframe component noise along with noise reduction technology. Recent work on aeroacoustic installation effects and their significance for exterior and interior noise will be discussed as well.