超声速空腔流激振荡与声学特性研究

基于高速风洞试验研究了超声速时空腔流激振荡与声学特性.试验马赫数为1.5,基于每米的雷诺数为2.26×107,来流边界层厚度为0.024 m,试验空腔长深比分别为15,12和6.结果表明:空腔内形成的剪切层与腔后壁相撞诱发腔内较强烈噪声,噪声从腔后缘向腔前缘传播时受到腔内流动的干扰,故同频率下腔后缘处的声压均高于腔前中部区域的声压.闭式和过渡式空腔长深比较大,剪切层与腔底面相撞在腔内形成的压缩波或激波,干扰了从腔内声波反馈回路、限制了流激振荡的形成,故腔内未出现明显的声压峰值激振频率;开式空腔长深比较小,剪切层直接跨过空腔中部与腔后壁相撞,产生的噪声向腔前缘传播,腔内形成流激振荡,并出现多个声压峰值激振频率. 

Cavity flow oscillations and aeroacoustic characteristics at supersonic speeds

Cavity flow oscillations and aeroacoustic characteristics at supersonic speeds were investigated based on flow-fields of three types of cavity flow.The data presented herein was obtained over Mach number of 1.5 at a Reynolds number of 2.26×107 per meter with a boundary-layer thickness of approximately 0.024m.The length-to-depth ratios of the cavities were 15,12 and 6,respectively.The results indicate that the intense noise resulted from impingement of shear-layer and the cavity rear-face occurs in the cavities.Sound pressure level(SPL) in the region upstream of the cavity rear-face is more than that in the region downstream of the cavity front-face and in the middle of the cavity.The compressible or shock waves induced by impingement of shear-layer and the cavity floor disturb the sound feedback mechanism from the cavity rear-face to the front-face at supersonic speeds,causing self-sustained flow oscillations and peak frequencies of the cavity tone inside cavities for transitional and closed cavities with large length-depth ratios.However,the shear-layer bridges the open cavity,which has no influence on the mechanism.The self-sustained flow oscillations and some peak frequencies occur inside the open cavity.