Effect of passive porous surface on the trailing-edge noise

Abstract

This study numerically investigates the effect of porous surfaces on the turbulent noise generated by a blunt trailing-edge of a flat plate. The three-dimensional turbulent flow over the flat plate (Re-c = 1.3 x 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 (LPCEs) coupled with LES. The porous surface is applied to a small, selected area near the trailing-edge where vortex shedding and edge-scattering of convecting eddies generate dipole noise. The computed results show that the trailing-edge with porosity epsilon=0.25 and permeability (normalized) K* = 0.01 yields a reduction of the tonal peak by 13 dB for the zero angle of attack (alpha = 0 degrees) case, via breaking not only in the streamwise direction but also in the spanwise direction, the spatial correlation of the wall pressure fluctuations near the trailing-edge. For the separated flow case (alpha = 5 degrees), the porous surface is found to weaken the pressure fluctuations at the trailing-edge and results in 3 similar to 10 dB noise reduction over a wide range of frequency, via interrupting the edge-scattering and reducing the separated flow region over the upper surface of the plate. (C) 2011 American Institute of Physics. [doi:10.1063/1.3662447]