On trailing edge noise with application in hydroacoustics

David Nigro (University of Manchester)

ATB Frank Adams 1,

The scattering of blade boundary layer pressure fluctuations into acoustic waves at the trailing edge, also called trailing edge noise, is of primary interest to the aerospace/marine industry as it is the main contribution to broadband self-noise for a subsonic propeller.

Extensive studies are available in the literature but mainly applied to aeroacoustics. These take advantage of the ‘slow’ speed of sound in air in order to use fast approximative models based on, for example, the Schwarzschild technique as in Amiet [1976] or Roger and Moreau [2005]. The model is based on the gust response function of a single blade. However, in water, the speed of sound is five times greater than in air, making the approximations of those models invalid at low to mid frequencies. An alternative approach, which is appropriate at low frequency for a finite chord aerofoil, involves the application of Mathieu functions and unsteady thin aerofoil theory. In this talk, it will be shown how the single blade problem can be recast into two wave scattering problems, and solved using several tools of diffraction theory.

 

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