Predictive Limits of Acoustic Diffraction Theory for Rough Wall Flows
Predictive Limits of Acoustic Diffraction Theory for Rough Wall Flows
复制标题
粗糙壁流声学衍射理论的预测极限
DOI：
10.2514/1.j052561
复制
发表时间：
2014
期刊：
影响因子：
2.5
通讯作者：
S. Glegg
中科院分区：
文献类型：
--
作者：
W. N. Alexander;W. Devenport;S. Glegg
粗糙的墙壁会通过涡流脱落等局部效应或对流湍流流场的衍射产生噪音。众所周知，对于流体动力学光滑的表面，衍射占主导地位，对于边界层大小许多倍的障碍物，自噪声占主导地位，但到目前为止，状态之间的转变尚未得到彻底研究。在本文中，通过分析由尺寸范围从 h/δ=5 至 6% 和 14 至 18% 的离散粗糙度元素获取产生的远场噪声测量推断出的非定常阻力，研究了粗糙壁流的声学衍射理论的局限性。将测量的非稳态阻力光谱与衍射理论的理论预测光谱进行比较。结果表明，衍射理论的有效性不仅取决于相对湍流和粗糙度尺度，还取决于粗糙度高度与边界层厚度的比率。它还表明不稳定的阻力谱会产生......
Rough walls can produce noise through local effects such as vortex shedding or through diffraction of the convected turbulent flowfield. It is known that diffraction dominates for hydrodynamically smooth surfaces and self-noise dominates for obstructions many times the size of the boundary layer, but as of yet, the transition between regimes has not been thoroughly investigated. In this paper, the limits of acoustic diffraction theory for rough wall flows are examined by analyzing the unsteady drag inferred from measurement of the far-field noise produced by fetches of discrete roughness elements ranging in size from h/δ=5 to 6% and from 14 to 18%. Measured unsteady drag spectra are compared to theoretically predicted spectra from diffraction theory. It is shown that the effectiveness of diffraction theory is not solely dependent on the relative turbulence and roughness scales, but on the ratio of roughness height to boundary-layer thickness as well. It is also shown that the unsteady drag spectra produce...