摘要
受控小扰动对流动稳定性与流场结构的调制作用具有潜在价值,但机理和失稳过程目前尚未完全明确。采用格子Boltzmann数值方法,对声场扰动条件下平行剪切流失稳过程开展了直接模拟研究,探讨了流动失稳的机理。研究表明,点源声场作用下的剪切流失稳形式依赖于激励声波的波长—文中定义为长波模式和短波模式,声波振幅的空间分布不均匀性是剪切层失稳的重要诱因。在短波模式下,受多普勒效应影响,剪切层上下两侧声波叠加效应导致流动上游区域压力脉动的波包结构;该结构的波长与剪切层失稳波长匹配,诱导流动失稳发生。在长波模式下,剪切层上声源垂直入射区首先失稳,剪切层对声波反射的方向选择性导致声压波动振幅分布的对称性破缺,且失稳区压力波动波长随时间推进而逐渐减小。当该波长落入剪切层失稳波长范围内时,剪切层流动开始失稳。
Controlled instability of parallel shear flows induced by weak disturbances is of great academic and pragmatic importance in fluid dynamics and industrial applications.However,the underline mechanism is still not fully understood yet.Consequently,this paper intends to explore the mechanism of sound-induced shear flow instability by a lattice Boltzmann simulation.It is found that the spatial inhomogeniety of sound-wave amplitudes plays a key role in the instability process.There are two types of developing of Kelvin-Helmholtz instability depending on the wave length of sound wave,namely the long-and short-wave modes.In the shortwave mode,the Doppler effect causes deviation of wave number of the sound in the upper and lower layers,respectively.The interference between the sound waves generates sound wave packets in the shear layer,which further induces flow instability if the length scale of the wave packet matches the unstable wave length of the shear layer.In the long-wave mode,unstable waves develop below the sound source.Sound waves are reflected by the shear layer nonuniformly.The symmetric distribution of the sound pressure is broken.On the other hand,the wave length of the distributed pressure wave decreases with time due to nonlinearity.
作者
陈效鹏
崔率
万振华
胡海豹
CHEN Xiaopeng;CUI Shuai;WAN Zhenhua;HU Haibao(School of Marine Science and Technology,Northwestern Polytechnical University,Xi’an 710072,China;School of Mechanics,Civil Engineering and Architecture,Northwestern Polytechnical University,Xi’an 710072,China;Key Laboratory of Aerodynamic Noise Control,China Aerodynamics Research and Development Center,Mianyang 621000,China;Department of Modern Mechanics,University of Science and Technology of China,Hefei 230027,China)
出处
《空气动力学学报》
CSCD
北大核心
2022年第3期130-139,I0003,共11页
Acta Aerodynamica Sinica
基金
国家自然科学基金(11872315,52071272,12102357,12102358)
基础前沿项目(JCKY2018-18)
陕西省自然科学基础研究计划资助项目(2020JC-18)
河南省水下智能装备重点实验室开放基金(KL01B2101)
气动噪声控制重点实验室开放课题(ANCL20210303)。
