The objective of this paper was to investigate acoustic pressure waves and the transient flow structure emitted from the single bubble near an elastic boundary based on the particle image velocimetry (PIV). A combination of an electric-spark bubble generator and PIV were used to measure the temporal bubble shapes, transient flow structure, as well as the mid-span deflection of an elastic boundary. Results are presented for three different initial positions near an elastic boundary, which were compared with results obtained using a rigid boundary. A formula relating velocity and pressure was proposed to calculate the acoustic pressure contours surrounding a bubble based on the velocity field of the transient flow structure obtained using PIV. The results show the bubbles near the elastic boundary presented a “mushroom” bubble and an inverted cone bubble. Based on the PIV-measured acoustic pressure contours, a significant pressure difference is found between the elastic boundary and the underside of the bubble, which contributed to the formation of the “mushroom” bubble and inverted cone bubble. Furthermore, the bubbles had opposite migration direction near rigid and elastic boundaries, respectively. In detail, the bubble was repelled away from the elastic boundary and the bubble was attracted by the rigid boundary. The resultant force made up of a Bjerknes force and buoyancy force dominated the migration direction of the bubble.

中文翻译：

---

基于PIV的弹性边界附近单个气泡的声压测量。

本文的目的是研究基于粒子图像测速（PIV）的弹性边界附近单个气泡发出的声压波和瞬态流动结构。电火花气泡发生器和PIV的组合用于测量时间气泡形状，瞬态流动结构以及弹性边界的中跨挠度。给出了弹性边界附近三个不同初始位置的结果，并将其与使用刚性边界获得的结果进行了比较。提出了一个与速度和压力有关的公式，以基于使用PIV获得的瞬态流动结构的速度场来计算气泡周围的声压轮廓。结果显示，弹性边界附近的气泡呈现“蘑菇”气泡和倒锥形气泡。根据PIV测得的声压轮廓，在弹性边界和气泡底面之间发现了明显的压差，这导致了“蘑菇”气泡和倒锥形气泡的形成。此外，气泡分别在刚性和弹性边界附近具有相反的迁移方向。详细地，气泡被排斥远离弹性边界，并且气泡被刚性边界吸引。由Bjerknes力和浮力组成的合力主导了气泡的迁移方向。在弹性边界和气泡底面之间发现明显的压力差，这导致了“蘑菇”气泡和倒锥形气泡的形成。此外，气泡分别在刚性和弹性边界附近具有相反的迁移方向。详细地，气泡被排斥远离弹性边界，并且气泡被刚性边界吸引。由Bjerknes力和浮力组成的合力主导了气泡的迁移方向。在弹性边界和气泡底面之间发现明显的压力差，这导致了“蘑菇”气泡和倒锥形气泡的形成。此外，气泡分别在刚性和弹性边界附近具有相反的迁移方向。详细地，气泡被排斥远离弹性边界，并且气泡被刚性边界吸引。由Bjerknes力和浮力组成的合力主导了气泡的迁移方向。