Noise Sources of Trailing-Edge Turbulence Controlled by Porous Media

Abstract

To reduce trailing-edge noise an investigation of a noise reduction technique based on porous media is presented. Large-eddy simulations (LES) and solutions of the acoustic perturbation equations (APE) are used to investigate the trailing-edge noise of a flat plate at a freestream Mach number 0.06 and a Reynolds number of 135000 based on the chord length and the freestream velocity. The acoustic fields are determined in a three dimensional domain to include the impact of the spanwise coherence length on the noise generation. The porous surface at the trailing edge covers an area in the spanwise times streamwise direction of 512 times 800 in inner wall units. The two-point correlation of the velocity components shows that the modified velocity field by the porous surface has a smaller correlation length and a smooth variation of the turbulence length at the trailing edge. The porous surface reduces the overall sound pressure level from 3dB to 8dB. The sound spectra possess a strong tone at the Strouhal number of fh/U∞ = 0.2 and the broadband spectrum follows the −2 power slope of the frequency. Due to the uniform porous surface the peak of the tone was decreased by 10dB.