Experiments in Fluids ( IF 2.3 ) Pub Date : 2021-10-01 , DOI: 10.1007/s00348-021-03308-2 M. T. Khoo 1, 2 , J. A. Venning 2 , B. W. Pearce 2 , P. A. Brandner 2
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Abstract
The spatial and acoustic characteristics of tip vortex cavitation (TVC) inception were measured in a cavitation tunnel. Numerous cavitation events were recorded to reveal the influence of different nuclei populations and cavitation numbers on nuclei capture and activation physics, and the role of the streamwise pressure distribution in a vortex. Synchronised high speed video and hydrophone measurements of cavitation events were taken in the trailing vortex of an elliptical hydrofoil at an incidence of \(6^\circ \) and a Reynolds number of \(1.5\times 10^6\). The injected nuclei population in the tunnel test section was varied by using different microbubble generators mounted upstream of the test section. Both the nuclei population and cavitation number have a significant effect on the inception location distribution along the trailing vortex, and in particular, inception event rates. The cavitation number alters the flow volume subjected to tension, thereby also affecting the shape of the inception location distribution. Once the nuclei are activated, cavity kinematic and acoustic properties are influenced by the local pressure (i.e. inception location and cavitation number) more so than initial nucleus size, at least in the \(\sim \)50–100 \(\upmu \hbox {m}\) diameter range considered in this study. Inception events that occur near the tip generate stronger acoustic pulses. At these inception locations, the frequency of the tonal peak associated with inception remains relatively constant for the two nuclei populations, but increases with cavitation number. This study provides insights into the roles of nucleation and cavitation number in TVC and informs future measurements and predictions of TVC dynamics and noise.
Graphic abstract
中文翻译：
成核和空化数对尖端涡流空化动力学和噪声的影响
摘要
在空化隧道中测量了尖端涡流空化 (TVC) 起始的空间和声学特性。记录了大量空化事件，以揭示不同原子核数量和空化数对原子核捕获和激活物理学的影响，以及涡流中流向压力分布的作用。在椭圆水翼的尾涡中以\(6^\circ \)的入射角和\(1.5\times 10^6\)的雷诺数进行空化事件的同步高速视频和水听器测量. 通过使用安装在测试部分上游的不同微气泡发生器来改变隧道测试部分中注入的核数。核数和空化数对尾涡的起始位置分布，特别是起始事件率都有显着影响。空化数会改变受到张力的流量，从而也影响初始位置分布的形状。一旦核被激活，腔运动学和声学特性受局部压力（即起始位置和空化数）的影响比初始核大小的影响更大，至少在\(\sim \) 50–100 \(\upmu \ hbox {m}\)本研究中考虑的直径范围。尖端附近发生的起始事件会产生更强的声脉冲。在这些起始位置，与起始相关的音调峰值的频率对于两个核群保持相对恒定，但随着空化数的增加而增加。这项研究提供了对成核和空化数在 TVC 中的作用的见解，并为未来 TVC 动力学和噪声的测量和预测提供了信息。
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