The natural frequencies of microbubble oscillation in elastic vessels
The natural frequencies of microbubble oscillation in elastic vessels
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DOI：
10.1121/1.3243292
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发表时间：
2009-12-01
影响因子：
2.4
通讯作者：
Saffari, Nader
中科院分区：
文献类型：
--
作者：
Martynov, Sergey;Stride, Eleanor;Saffari, Nader
本文应用弹性血管中气泡动力学的理论模型，数值研究了约束对气泡自由振荡的影响。血管壁变形描述使用集中参数膜型模型，这是耦合到Navier-Stokes方程的流体运动的血管内。结果表明，气泡在有限长的容器中的振荡的特点是频谱的频率，可区分的高频和低频模式。高频模式的频率随着容器弹性模量而增加，并且对于薄壁容器，可以高于无约束液体中气泡振荡的固有频率。在无限刚性容器壁的极限情况下，低频模式的频率接近于限制在刚性容器中的气泡的众所周知的解决方案。为了解释的结果，一个简单的两个自由度模型。结果表明，为了最大限度地沉积的声能，一个气泡被限制在一个长的弹性容器被激发的频率高于相应的自由气泡的固有频率。
A theoretical model for the dynamics of a bubble in an elastic blood vessel is applied to study numerically the effect of confinement on the free oscillations of a bubble. The vessel wall deformations are described using a lumped-parameter membrane-type model, which is coupled to the Navier-Stokes equations for the fluid motion inside the vessel. It is shown that the bubble oscillations in a finite-length vessel are characterized by a spectrum of frequencies, with distinguishable high-frequency and low-frequency modes. The frequency of the high-frequency mode increases with the vessel elastic modulus and, for a thin-wall vessel, can be higher than the natural frequency of bubble oscillations in an unconfined liquid. In the limiting case of an infinitely stiff vessel wall, the frequency of the low-frequency mode approaches the well-known solution for a bubble confined in a rigid vessel. In order to interpret the results, a simple two-degree-of-freedom model is applied. The results suggest that in order to maximize deposition of acoustic energy, a bubble confined in a long elastic vessel has to be excited at frequencies higher than the natural frequency of the equivalent unconfined bubble.