Experimentelle Untersuchungen des Klappenseitenkantenlärms

• Experimental study on flap side edge noise

Tiedemann, Christian; Henke, Rolf (Thesis advisor)

Aachen : Publikationsserver der RWTH Aachen University (2009)
Dissertation / PhD Thesis

Aachen, Techn. Hochsch., Diss., 2009

Abstract

This thesis deals with the mechanisms being responsible for flap side-edge noise. Beside acoustic properties of this noise source, which are studied by a microphone array, detailed measurements of the flow field around a flap side-edge are conducted. At first the steady flow field of a reference wing flap model is getting measured. Surface flow is estimated in a next step by oil flow visualization. These results are used to define planes for Particle-Image Velocimetry measurements which will take place afterwards. Both, the mean flow field and the instantaneous flow field are analysed to obtain information on the mechanisms of sound generation. These results are compared with the results of microphone array measurements. The microphone array is used to resolve the sound source distribution along the flap side-edge. Particle-Image Velocimetry and microphone array measurements are usually not done in parallel but rather during different experiments. Combining these two results (acoustic results and flow field measurements) shall improve the knowledge about flap side-edge noise generation and shall help to develop ideas about its generation process in general. The plausibility of these ideas is tested by specific modifications of the flap side-edge. Afterwards more realistic configurations are studied by adding cavities to the flap side-edge as can often be seen on real aircrafts. Cavity depth is varied to obtain information on this parameters influence regarding noise generation. Finally, the noise reduction method of adding brushes on the flap side-edge is analyzed. Specific parameters of the brushes are modified to see their influence on flap side-edge noise generation.