Numerical Investigation of Fluid Injection to Reduce Trailing-Edge Noise

点击翻译按钮获取中文摘要

The EU Vision 2020 expects a 10dB noise reduction per aircraft operation. That is, at landing besides engine noise especially airframe noise generated by high-lift devices and landing gears has to be reduced since it is an equally significant noise source. Due to the disparity of the flow characteristics of high-lift devices, which represent a slender body, and landing gears, which consist of blunt bodies, only the noise reduction of the slender-body problem will be considered in this proposal. As a generic configuration the trailing edge of the flat plate of finite thickness is used to numerically analyze the potential to reduce the noise when an “acoustically soft” trailing edge is designed. To be more precise, the discontinuity experienced by an eddy in convecting over the edge is to be lowered to decrease the intensity of edge scattering. This reduction of the discontinuity is to be realized by injecting an additional fluid upstream of the edge to generate a near-wall flow structure that resembles a softer surface as the edge is approached and by injecting fluid right at the blunt trailing edge to decrease the shear stress in the free-shear layer. The well-established hybrid LES-APE method is applied to analyze the mechanisms such that the overall objective of a frequency and directivity independent noise reduction is achieved.