Trailing edge noise reduction using porous treatments

This paper provides an experimental investigation to better understand the mechanisms of flow interaction and sound generation over the blunt trailing-edges with different porous treatments. The noise generation characteristics have been examined using a flat plate equipped with a surface pressure transducer and was performed in an anechoic open jet wind tunnel. Two types of porous materials with different porosities and permeability constants were tested. To reveal the effect of porous treatment on the radiated noise, the far-fleld noise measurements have been carried out. Surface pressure fluctuation measurements have also been performed near the plate trailing-edge. In general, results have shown that the reduction in the sound pressure level is sensitive to the porosity and permeability of the porous materials. The far-fleld results have shown that the porous treatments can effectively eliminate the vortex shedding tonal peak, leading to a signiflcant noise reduction of about 35 dB by the highly permeable material. The results also have indicated that the development of the broadband hump seen in the near-fleld noise spectra for the highly permeable surface is only local to the plate surface and not observed in the far-fleld noise spectra. The directivity pattern of the radiated noise shows that the signiflcant noise reduction is observed at the vortex shedding frequency. Based on this research and recent works, it is believed that the porous materials have a high potential for various aerodynamic and aeroacoustic applications.