Slat Noise Reduction Based on Turbulence Attenuation Downstream of Shear-layer Reattachment
Kazuomi Yamamoto, Mitsuhiro Murayama, Kazuhide Isotani, Yosuke Ueno, Kensuke Hayashi, Tohru Hirai
Abstract
This study investigates a slat noise reduction method based on turbulence attenuation downstream of the shear-layer reattachment by increasing the distance between the reattachment point of the shear-layer in the slat cove and the slat trailing edge. Parametric studies using a very large eddy simulation are conducted for many modified slat geometries that combine two different approaches. One is to extend the slat chord near the trailing edge, and the other is to attach a bump on the slat lower surface. The trailing edge extensions well reduce the pressure disturbance at the slat trailing edge and considerably reduce the noise level in lower frequency range where the narrow band peaks are dominant. The bump with a smaller radius of curvature, which is about 20% of the slat chord length, rapidly attenuates the pressure disturbance downstream of the reattachment point, resulting in reductions of higher frequency broadband noise as well. In the case of 30P30N geometry, it is found that even smaller slat modifications can achieve a noise reduction of almost 10 dB. The physics of noise reduction mechanism and its general characteristics are also described from the obtained results.