Effect of trailing-edge bevel on the aeroacoustics of a flat-plate

Abstract

An experimental study was conducted to investigate the effect of the bevel angle on the radiated noise and the associated flow-field over the trailing-edge. The bevel angle of the trailing-edge was adjusted over a broad range of angles to demonstrate the aeroacoustic properties of the attached and separated boundary layers. The far-field noise results obtained from the beamforming array were assessed in conjunction with the associated flow-field. Far-field measurement results show an increased level of radiated noise for a range of bevel angles where the flow remains attached compared to the baseline flat-plate case without a bevel angle. Near-field measurements are presented in terms of pressure coefficients, unsteady surface pressure results, turbulence properties of the boundary layer, and corresponding spectral properties of these quantities. The near-field measurement results indicate that introducing a bevel angle yields a region of favorable pressure gradient on the flat-plate and bevel, which accelerates the flow and reduces the size of structures in the boundary layer up until the mid-bevel region, which then decelerates toward the trailing-edge. This change increases the energy content of surface pressure fluctuations as well as the energy content of the velocity field over the trailing-edge and wake, which, in turn, results in an increased radiated far-field noise as supported by beamforming results. Furthermore, at a sufficiently high bevel angle, where pronounced flow separation occurs, the lack of interaction between trailing-edge and shear layer leads to a significant reduction in the radiated far-field noise compared to that of the baseline flat-plate.