边界层厚度对腔体气动声学特性影响数值模拟

发布时间：2018-09-03 12:59

【摘要】：为了研究来流边界层厚度对开式腔体气动声学特性的影响,基于分离涡模拟方法,计算了来流马赫数为2.0条件下,不同来流边界层厚度与腔体深度比时,长深比为5.88的腔体流动特性,得到了该腔体声压级的频谱特性.计算结果表明:随着来流边界层厚度增加,形成的剪切层稳定性增强,失稳后上下摆动幅度减少,失稳生成的大尺度涡与超声速主流的相互作用减弱,使得大尺度涡发展到腔体后缘时所具有的平动动能和转动动能降低.大尺度涡撞击腔体后缘在腔体内形成的气动噪声的声压级降低,最大减小幅度达7.5dB.同时各阶模态的频率也发生偏移,偏移值在100Hz左右.基于新的假设重新推导了Rossiter公式,明确了经验常数的物理意义,并以此解释了频率偏移现象.
[Abstract]:In order to study the effect of the thickness of the incoming flow boundary layer on the aerodynamic acoustical characteristics of the open cavity, the ratio of the thickness of the boundary layer to the depth of the cavity is calculated when the Mach number of the incoming flow is 2.0, based on the separation vortex simulation method. The flow characteristics of the cavity with a aspect ratio of 5.88 are obtained, and the spectral characteristics of the sound pressure level of the cavity are obtained. The results show that the stability of the shear layer increases with the increase of the thickness of the boundary layer, the amplitude of fluctuation decreases after instability, and the interaction between the large scale vortex generated by instability and the main stream of supersonic velocity weakens. The translational kinetic energy and rotational kinetic energy of the large scale vortex developing to the rear edge of the cavity are reduced. The sound pressure level of the aerodynamic noise formed in the cavity by large-scale vortex impingement on the rear edge of the cavity is reduced to 7.5 dB. At the same time, the frequency of each mode is offset, the offset value is about 100Hz. Based on the new hypothesis, the Rossiter formula is rededuced, the physical meaning of the empirical constant is clarified, and the phenomenon of frequency offset is explained.
【作者单位】：北京交通大学土木建筑工程学院;中国航空工业集团公司沈阳飞机设计研究所;
【基金】：国家自然科学基金(11172283)
【分类号】：V211.3

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