Effect of Porous Surface on the Flat Plate Self-Noise

In this study, the effect of porous surface on the turbulent noise generated by a blunt trailing-edge of a flat plate is investigated. The three-dimensional turbulent flow over the flat plate (Rec=1.3×10 5 and M=0.06) is computed by incompressible large eddy simulation (LES) based on the volume-averaged Navier-Stokes equations, while the acoustic field is calculated by the linearized perturbed compressible equations (LPCE) coupled with LES solutions. The porous surface is applied to a small, selected area near the trailing-edge, where the Karman vortex shedding and eddy scattering produce dipole sounds. The computed results show that the trailing-edge with porosity e=0.25 and permeability (normalized) K * =0.01 yields a reduction of tonal peak by 13dB for zero angle of attack (α=0o), via breaking not only in the streamwise direction but also in the spanwise direction the spatial correlation of the wall pressure fluctuations (Rpp) near the trailing-edge. For the separated flow case (α=5o), the same configuration of the porous surface is found to weaken the pressure fluctuations at the trailing edge. It results in 3-10dB noise reduction over a wide range of frequency, via reducing the separated flow region over the upper surface of the plate.

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