力学学报 ›› 2010, Vol. 42 ›› Issue (6): 1050-1059.doi: 10.6052/0459-1879-2010-6-lxxb2009-544

• 研究论文 • 上一篇    下一篇

超声波作用下气泡的非线性振动

王成会,林书玉   

  1. 陕西师范大学应用声学研究所
  • 收稿日期:2009-09-03 修回日期:2010-04-16 出版日期:2010-12-10 发布日期:2010-12-02
  • 通讯作者: 王成会 E-mail:wangld001@snnu.edu.cn

The nonlinear oscillation of bubbles in the ultrasonic field

Chenghui Wang 王成会,   

  1. Applied Acoustics Institute, Shaanxi Normal University, Xi'an 710062, China
  • Received:2009-09-03 Revised:2010-04-16 Online:2010-12-10 Published:2010-12-02
  • Contact: Chenghui Wang 王成会 E-mail:wangld001@snnu.edu.cn

摘要: Flynn方程在引入泡内气体的压缩性修正后能够更好地描述超声波作用下液体内气泡的非线性振动。我们以此为基础通过数值分析得到了不同初始半径的气泡在同一声场中的振动位移时间图像和相轨迹,发现气泡的运动行为对其初始状态有很强的依赖关系,在频率为26.5 kHz,幅度为1.35 atm的声波作用下,初始半径小于1 μm的气泡作小幅受迫振动,大于200 μm的气泡作小幅准本征振动,不具备空化气泡特征。声场中的小气泡对声波强度变化的反应更为激烈,当增加声强度时,可将一定范围内的小幅受迫振动气泡转化为空化气泡,并且,当驱动声波压力幅值增加时,初始半径越小的气泡的最大位移增加幅度越大。驱动声波频率同样影响气泡的振动。随着声波频率的升高,空化气泡的初始半径取值区间越来越小,空化振荡也越来越弱。本文还通过高速摄影系统对换能器作用于未除气的自来水所引起的变化进行了实验研究,结果表明,超声波作用下液体内的气泡场是一个混合场,场内气泡尺寸呈一定的分布状态,不仅有空化气泡,还有毫米级的大气泡。气泡的运动行为直接影响空化效果。超声空化场是一个复杂的物理场,场内除了有气泡的振动外,还有气泡间的相互吸引、碰撞和结合。

关键词: 高速摄影

Abstract: The nonlinear oscillation can be described by Flynn Equation when considering the compressibility of inner gas of bubbles. Based on the model the displacement/the time relation and phase-trajectory of vibrating bubbles of different initial radii are simulated numerically, which shows that the movements of bubbles depend strongly on the initial conditions in the same sound field. When the driving frequency of 26.5kHz and intensity of 1.35atm is adopted, the bubbles oscillate forcedly with initial radii are smaller than 1\mu m, while oscillate quasi-intrinsically with initial radii larger than 200\mu m. The two kinds of bubbles are not cavitation ones. The changes of smaller bubbles are more intense to the sound intensity. If the sound intensity increases, a restricted range of bubbles smaller than 1\mu m can become cavitation ones. Furthermore, the smaller the initial radius is, the larger the increase of maximum displacement is. In addition, the driving frequency also affects the movement of bubbles. With the increase of driving frequency, the initial radii range of cavitation bubbles decrease, and the oscillation intensity reduces. The results present that there are three types of bubbles in the ultrasonic field: big bubbles oscillated quasi-intrinsically, cavitation bubbles and micro-bubbles oscillated forcedly at the driving frequency. The size range of cavitation bubbles is influenced jointly by driving frequency and pressure amplitude. At the same time, we researched the bubbles field in tap water by high speed photography when the ultrasonic transducer is working. The results show that there is a mixed field, where many bubbles with different radius are vibrating and moving. Not only cavitation bubbles but also bubbles with the millimeter scales coexist in the radiation field of ultrasonic transducer. The movements of bubbles can affect the intensity of cavitation directly. There is a complex physical field when cavitation comes into being in the liquid, where bubbles are vibrating, colliding and combining.

Key words: high speed photography

中图分类号: 

  • O322