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Computational study of aerofoil's self-noise when subject to leading edge jet blowing flow control

AIAA 2022-2920
Session: Airframe/High-Lift Noise IV: Misc & Acoustic/Fluid Dynamic Interaction IV: Active Control
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A computational study is carried to investigate the effect of fluid injection at the leading edge of a symmetric profile (NACA0018) on the source of the laminar boundary layer – vortex shedding (LBL-VS) noise. The Reynolds number as based on the chord length is set to 250k as applicable for small vertical axis wind turbines. Two computational methods are used: 2D Unsteady Reynolds Averaged Navier Stokes (URANS) and 3D Large Eddy Simulation (LES). Both yield very good agreement with reported experimental quasi-steady lift and drag coefficients particularly at pre-stall conditions for the range of reported fluid injection. LES results are used to study the vortex shedding showing suppression of the vortex shedding and thickening of the shedded wake for angle of attack (AoA) of 4° and 8°, when the fluid injection exceeded of the free stream which corresponds to a fluid injection momentum thickness Cu=5.4%. However, reducing Cu=0.5% actually enhanced the vortex shedding at AoA=8°. This was confirmed to enhance the Curle’s compact source as expressed by the time derivative of the lift coefficient, where an additional dominant mode was found for Cu=0.5%. The time-averaged Pressure and skin friction distributions along the profile are analysed to show the effects of the Cu on the lift coefficient and the occurrence of flow separation that can affect LBL-VS noise.