摘要
Self-sustained oscillation and the sound radiation of flow over an open cavity is of great importance in nature and industry.Influences of filled porous media in the cavity are investigated numerically by using a lattice Boltzmann method in two-dimensional space.It is shown that the outcomes of the porous patch depend on the location of the patch and the original flow mode,namely shear layer(SL)and wake mode(WM).For SL flow,the porous patch either damps the vortical flow or suppresses the generation of the secondary vortex sheet on the wall.The later effect destabilizes the SL.Consequently,the radiated sound is reduced as the patch is on the trailing edge,and increased with porous patch on the floor,respectively.For flow in WM,a transition from WM to SL mode is found when the porous patch is set either on the floor or behind the leading wall.In the cases,the recirculating flow on large scale is blocked significantly due to the porous patch,therefore,the WM flow is not sustained.On the other hand,the porous patch on the trailing edge slightly weakens the sound due to dissipation.The study shows that assembling of porous media in the flow field decreases the radiated sound level only if it is done carefully.
要空腔流动的自持振荡和声辐射在自然界和工业中具有重要意义.采用二维格子Boltzmann方法数值研究了空腔中填充多孔介质的影响.结果表明,多孔填充物的减噪结果取决于填充物的位置和原始流动模式,即剪切层(SL)和尾流模式(WM).对于SL流,多孔填充物要么抑制涡流,要么抑制壁面二次涡片的产生.后期效应会破坏剪切层的稳定性.因此,当填充物位于后缘时,声辐射减小,而底部的多孔填充物则使声辐射增大.对于WM中的流动,当多孔填充物设置在底部或前壁后时,会发现从WM模式到SL模式的过渡.在这种情况下,由于多孔填充物的存在,大规模的再循环流被显著阻断,因此,WM流无法持续.另一方面,后缘上的多孔填充物由于耗散而使声辐射略微减弱.研究表明,在流场中组装多孔介质可以降低声辐射等级.
作者
Ruqian Guo
Xiaopeng Chen
Zhenhua Wan
Haibao Hu
Shuai Cui
郭汝乾;陈效鹏;万振华;胡海豹;崔率(School of Mechanics,Civil Engineering and Architecture,Northwestern Pnlytechnical University,Xi'an 710129,China;School of Marine Science and Technology,Northwestern Polytechnical University,Xi'an 710072,China;Department of Modern Mechanics,University of Science and Technology of China,Hefei 230027,China)
基金
supported by the National Natural Science Foundation of China(Grant No.11872315)
the Natural Science Basic Research Program of Shaanxi(Grant No.2019JM-105).
