超声速来流边界层厚度对浅腔声学特性的影响

通过分析不同来流边界层厚度与空腔深度比(δ/D)下腔内中心线上的脉动声压级的分布和不同测点的声压频谱特性,讨论了超声速来流边界层厚度对浅腔(长深比分别为12和15)声学特性的影响.试验来流马赫数为1.5,基于每米的雷诺数为2.26×107.结果表明,δ/D减小导致浅腔内的噪声更加强烈,腔前后部的声压级分布更不均匀;除了个别离散频率外,腔内不同测点其余离散频率对应的声压级都有不同程度的增大.δ/D减小引起空腔前部和后部区域几乎整个离散频率范围内的噪声声压级有明显升高;因超声速浅腔流动,腔中部产生的激波的干扰因素的影响,边界层流动特性对浅腔中部区域的声学特性影响较小. 

Shallow cavity noise influencing by boundary-layer thickness at supersonic speeds

An experimental investigation has been constructed to perform effects of boundary-layer thickness on shallow cavity noise characteristics, and sound pressure level (SPL) distributions and sound pressure frequency spectrum characteristics (SPFS) inside cavities with length to depth ratios of 12 and 15 at supersonic speeds are analyzed. The data presented herein was obtained over a Mach number of 1.5 at a Reynolds number of 2.26×107 per meter. The results show that decrease in ratios of the boundary-layer thickness to the cavity depth causes flow oscillation amplification, noise enhancement. It leads to increase in SPL in the high-frequency range with the region downstream of the cavity face, and has a significant influence on SPFS characteristics in the middle and rearward of the cavity in the low-frequency range. Generally, decrease in boundary-layer thickness has ad