Investigations on the Application of Various Surface Treatments for Trailing Edge Noise Reduction on a Flat Plate

Abstract

In the present study, a range of different surface treatments is considered for the attenuation of flat plate trailing edge noise through reducing the power spectral density of the unsteady surface pressure fluctuations near the trailing edge. This approach is inspired by the recent studies on finlets, which have proven the trailing edge noise reduction capability of these treatments. To investigate the development of the boundary layer turbulence, measurements of the unsteady surface pressure along the center line and the span of the flat plate are presented. Particular focus is set on the formation and development of turbulence structures in front of and within the treated area. Far-field noise measurement results suggest that the conventional finlets are the most suitable surface treatment to efficiently reduce the trailing edge noise. However, in terms of reducing the unsteady pressure loading on the surface, other configurations produce comparable effects, nevertheless they increase the far-field noise level. The beamforming maps for discrete frequencies suggest that additional noise likely originates from the treatments themselves. Investigations of the static and unsteady surface pressure fields reveal further possible mechanisms related to the overall noise increase. The outcomes of this study thus inform about surface treatment design features important for effective far-field noise reduction.