Acoustic microbubble dynamics with viscous effects
Acoustic microbubble dynamics with viscous effects
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DOI：
10.1016/j.ultsonch.2016.11.032
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发表时间：
2017-05-01
影响因子：
8.4
通讯作者：
Wang, Qianxi
中科院分区：
文献类型：
--
作者：
Manmi, Kawa;Wang, Qianxi
超声作用下的微泡动力学在生物医学超声、超声化学和空化清洗等领域有着重要的应用。这种现象中的粘性效应是必不可少的，因为Re相关的雷诺数约为0（10）。流场的特征是体积内的无旋流，但在气泡表面存在薄涡量层。本文采用基于粘性势流理论的边界积分方法对这一现象进行了研究。通过在气泡表面的动态边界条件下加入无旋流的法向粘性应力，将粘性效应纳入模型。采用Joseph & Wang（2004）的粘性修正压力来解决自由表面无旋流的非零剪应力与零剪应力的物理边界条件之间的差异。当Re = 10时，该模型与球形气泡在粘性液体中振荡几周的瑞利-普莱塞特方程很好地吻合。它与实验数据和基于Navier-Stokes方程的刚体边界附近瞬态气泡动力学轴对称模拟结果密切相关。我们进一步分析了刚性边界附近的微泡动力学，分别在与临床相关的参数区域垂直和平行于边界的超声运动。从射流速度、气泡体积、质心运动、开尔文冲量和气泡能量等方面分析了粘性对声微泡动力学的影响。Elsevier B.V.版权所有
Microbubble dynamics subject to ultrasound are associated with important applications in biomedical ultrasonics, sonochemistry and cavitation cleaning. The viscous effects in this phenomenon is essential since the Reynolds number Re associated is about O(10). The flow field is characterized as being an irrotational flow in the bulk volume but with a thin vorticity layer at the bubble surface. This paper investigates the phenomenon using the boundary integral method based on the viscous potential flow theory. The viscous effects are incorporated into the model through including the normal viscous stress of the irrotational flow in the dynamic boundary condition at the bubble surface. The viscous correction pressure of Joseph & Wang (2004) is implemented to resolve the discrepancy between the non-zero shear stress of the irrotational flow at a free surface and the physical boundary condition of zero shear stress. The model agrees well with the Rayleigh-Plesset equation for a spherical bubble oscillating in a viscous liquid for several cycles of oscillation for Re = 10. It correlates pretty closely with both the experimental data and the axisymmetric simulation based on the Navier-Stokes equations for transient bubble dynamics near a rigid boundary. We further analyze microbubble dynamics near a rigid boundary subject to ultrasound travelling perpendicular and parallel to the boundary, respectively, in parameter regions of clinical relevance. The viscous effects to acoustic microbubble dynamics are analyzed in terms of the jet velocity, bubble volume, centroid movement, Kelvin impulse and bubble energy. Crown Copyright (C) 2016 Published by Elsevier B.V. All rights reserved.