Trailing Edge Noise in Shear Flow

Dynamic stall is an aeroacoustic phenomenon that occurs when rapid changes in the aerofoil’s AoA can potentially cause separation in the flow, sudden drops in the lift coefficient and produce excessive unwanted noise. This is an important issue for the development of next-generation electric propulsion and energy production. In this paper, we will be considering the attached flow/weak stall situation which occurs at low angles of attack. We are building upon recent work where Goldstein’s formulation of Rapid Distortion Theory has been used in symmetric shear flow problems with a small Mach number. For our purposes, we consider the case where this shear flow is asymmetric, representing light stall, and is disturbed by a vortical disturbance within the boundary layer of the aerofoil. These problems were solved using the scalar Wiener-Hopf technique and after deforming to steepest descent contours, the far-field is composed of three parts: steepest descent, critical boundary layer and wake modal contributions. The effects of the boundary layer profile on acoustic directivity will be presented. This work is part of a larger project, joint with colleagues from the University of Bristol and Queen Mary University of London conducting experimental and computational studies respectively, which will provide strong guidance for our analytical modelling.