Effect of the Reynolds number on the aeroacoustic fields of a transitional supersonic jet
Effect of the Reynolds number on the aeroacoustic fields of a transitional supersonic jet
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DOI：
10.1063/1.5138195
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发表时间：
2020-04
影响因子：
4.6
通讯作者：
Y. Ozawa;T. Nonomura;A. Oyama;K. Asai
中科院分区：
文献类型：
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作者：
Y. Ozawa;T. Nonomura;A. Oyama;K. Asai
通过粒子图像测速 (PIV)、纹影可视化和近场声学测量，对超音速喷气机气动声场的雷诺数效应进行了实验研究。在理想膨胀条件下，马赫数为 2.0 的冷超音速射流是根据喷嘴出口直径的雷诺数产生的，范围为 105 到 106。本研究重点关注超音速射流的层流到湍流的转变，包括过渡条件 (Re ≈ 105)。高雷诺数射流 (Re = 106) 的 PIV 结果在喷嘴出口处呈现出完全湍流的剪切层，显示剪切层宽度呈线性增长。相反，在低雷诺数射流（Re = 105）的情况下，在过渡区域附近观察到湍流脉动显着增加和剪切层生长速率急剧变化。纹影可视化和声学测量表明，转变的湍流波动产生了强烈的马赫波。由于层流到湍流的转变对初始扰动敏感，因此还研究了扰动喷嘴流的影响。在低雷诺数射流（Re = 105）入口处添加物理扰动可以促进较早的过渡并抑制喷嘴外部湍流脉动的显着增加。由于扰动而引起的流场变化导致声压级降低。因此，具有扰动的低雷诺数射流的气动声场表现出与高雷诺数射流（Re = 106）相似的趋势，高雷诺数射流在喷嘴出口处已经表现出完全湍流剪切层。
The Reynolds number effect on the aeroacoustic fields of a supersonic jet was experimentally investigated via particle image velocimetry (PIV), schlieren visualization, and near-field acoustic measurements. Cold supersonic jets under ideally expanded conditions at a Mach number of 2.0 were produced with the Reynolds number, based on the diameter of the nozzle exit, ranging from 105 to 106. This study focuses on the laminar-to-turbulent transition of a supersonic jet, including a transitional condition (Re ≈ 105). The PIV results of the high-Reynolds-number jet (Re = 106), which exhibited a fully turbulent shear layer at the nozzle exit, show a linear growth of the shear layer width. Conversely, a significant increase in the turbulent fluctuations and a drastic change in the shear-layer-growth rate were observed near the transition region in the case of the low-Reynolds-number jet (Re = 105). The schlieren visualization and acoustic measurements imply that the turbulent fluctuations of the transition generated strong Mach waves. The effect of disturbing the nozzle flow was also investigated because the laminar-to-turbulent transition is sensitive to the initial disturbance. A physical disturbance added in the inlet of the low-Reynolds-number jet (Re = 105) can promote an earlier transition and suppress a significant increase in the turbulence fluctuations outside the nozzle. The changes in the flow fields due to the disturbance result in a decrease in the sound pressure level. Therefore, the aeroacoustic fields of the low-Reynolds-number jet with the disturbance show similar trends to those of the high-Reynolds-number jet (Re = 106), which already exhibited a fully turbulent shear layer at the nozzle exit.