Horiba Taisei, Ogasawara Toshiyuki, Takahira Hiroyuki
Department of Mechanical Engneering, Osaka Prefecture University, Sakai, 599-8531, Japan.
J Acoust Soc Am. 2020 Feb;147(2):1207. doi: 10.1121/10.0000649.
Cavitation bubble cloud formation due to the backscattering of high-intensity focused ultrasound (HIFU) from a laser-induced bubble in various water temperatures and dissolved oxygen (DO) has been investigated. A laser-induced bubble generated near the geometrical focus of HIFU is utilized to yield intense negative pressure by the backscattering. Optical observation with a high-speed video camera and pressure measurement with a fiber-optic probe hydrophone are conducted simultaneously to understand the forming process of a bubble cloud and corresponding pressure field by the backscattering. Optical observation shows that a bubble cloud grows stepwise forming multiple layers composed of tiny cavitation bubbles, and the cavitation inception position is consistent with the local minimum pressure position simulated with the ghost fluid method. The bubble cloud grows larger in the opposite direction of HIFU propagation, and the absolute value of the cavitation inception pressure decreases with an increase in water temperature. The linear correlation between cavitation inception pressure and water temperature agrees with that given by Vlaisavljevich, Xu, Maxwell, Mancia, Zhang, Lin, Duryea, Sukovich, Hall, Johnsen, and Cain [IEEE Trans. Ultrason. Ferroelectr. Freq. Control 63, 1064-1077 (2016)]. However DO has minor dependence on the cavitation inception pressure when DO is degassed sufficiently. Furthermore, the gas nucleus size that might exist in the experiment has been estimated by using bubble dynamics.
研究了在不同水温及溶解氧（DO）条件下，高强度聚焦超声（HIFU）从激光诱导气泡反向散射导致的空化泡云形成情况。利用在HIFU几何焦点附近产生的激光诱导气泡，通过反向散射产生强烈的负压。同时使用高速摄像机进行光学观测，并使用光纤探头水听器进行压力测量，以了解气泡云的形成过程以及反向散射产生的相应压力场。光学观测表明，气泡云呈阶梯式生长，形成由微小空化泡组成的多层结构，并且空化起始位置与用虚拟流体方法模拟的局部最小压力位置一致。气泡云在与HIFU传播相反的方向上生长得更大，并且空化起始压力的绝对值随着水温的升高而降低。空化起始压力与水温之间的线性相关性与Vlaisavljevich、Xu、Maxwell、Mancia、Zhang、Lin、Duryea、Sukovich、Hall、Johnsen和Cain在[《IEEE超声、铁电与频率控制汇刊》63, 1064 - 1077 (2016)]中给出的一致。然而，当DO充分脱气时，DO对空化起始压力的依赖性较小。此外，通过使用气泡动力学估计了实验中可能存在的气体核尺寸。
