Edge scattering of aerodynamic sound by a lightly loaded elastic half-plane
Edge scattering of aerodynamic sound by a lightly loaded elastic half-plane
复制标题
轻载弹性半平面对空气动力声的边缘散射
DOI：
--
复制
发表时间：
1975
期刊：
影响因子：
--
通讯作者：
P. Cannell
中科院分区：
文献类型：
--
作者：
P. Cannell
我们研究了当致密的湍流涡流靠近半无限长的受波面，但其边缘有多个声波波长时，辐射的声场。利用Lighthill声学类比将问题简化为平面声波对半无限弹性板的绕射问题。利用Wiener-Hopf技术，用轮廓积分精确地解决了这一问题。对于无因次流体载荷参数ϵ趋于零时的极限情况，给出了远声场的显式解。特别注意了耦合流体和平板振动的亚音速表面波模式。在低频段，邻近湍流涡流在平板中产生的大部分弹性波能以亚音速表面波模式传播而不受衰减。与板的边缘相互作用产生间接散射场，其强度表现出与边缘散射半平面的声场的典型的cos 2/θ(线θ=0定义半无限表面)的依赖关系。涡旋的声功率在其自由空间值上增加了系数ϵ2(MAs)-1，其中mas=cp/c表示真空中平板波的自然速度与声速的比率。在典型的航空应用中，在100赫兹的特征涡流频率下，e可高达18分贝。
We investigate the acoustic field radiated when a compact turbulent eddy lies close to a semi-infinite wave-bearing surface, but many acoustic wavelengths from its edge. The Lighthill acoustic analogy is used to reduce the problem to the simpler one of the diffraction of a plane sound wave by a semi-infinite elastic plate. This is solved exactly in terms of a contour integral by means of the Wiener-Hopf technique. An explicit solution for the far sound field is then developed for the limiting case when a non-dimensional fluid loading parameter ϵ tends to zero. Particular attention is paid to the subsonic surface wave modes which couple the fluid and plate vibrations. At low frequencies the bulk of the elastic wave energy induced in the plate by the adjacent turbulent eddy propagates without attenuation in a subsonic surface wave mode. Interaction with the edge of the plate induces an indirect scattered field whose intensity exhibits the dependence on cos2 ½θ(the line θ = 0 defines the semi-infinite surface) typical of the acoustic field of an edge scattering half-plane. The acoustic power of the eddy is increased over its free space value by a factor ϵ2(Mas)-1, where Mas = cp/c represents the ratio of the natural speed of plate waves in vacuo to the speed of sound. In typical aeronautical applications e can be as large as 18 dB at characteristic eddy frequencies of 100 Hz.