含混合气泡液体中声波共振传播的抑制效应

当声波在含气泡的液体中传播时会出现共振传播现象,即在气泡的共振频率附近声衰减和声速会显著地增大,这是声空化领域的一个重要现象.以往的研究一般假设液体中只存在单一种类的气泡,因此忽略了声波共振传播的某些重要信息.本文研究了含混合气泡液体中声波的共振传播,混合气泡是指液体中包含多种静态半径不同的气泡.结果显示:在这种系统中存在声波共振传播的抑制效应,即与含单一种类气泡的系统相比,在含混合气泡的系统中声波的共振衰减和共振声速会明显变小.对于两种气泡混合、多种气泡混合以及气泡满足某种连续分布的系统,研究了抑制效应的本质和主要特征,此外还探究了黏性和空化率等对抑制效应的影响.本文的研究结果是对该领域现有知识的必要补充.

Restraining effect of resonant propagation of acousticwaves in liquids with mixed bubbles

There is the resonant propagation phenomenon of acoustic wave in bubbly liquid, i.e., the attenuation coefficient and the velocity of acoustic wave in range of resonant frequencies of bubbles can become very large. In previous papers, generally adopted was a simplified assumption that there is a single type of bubble in a liquid. It restricts our understanding of the resonant propagation phenomenon. In this paper the resonant propagation of acoustic wave in a liquid with mixed bubbles is studied. Here, static radii of bubbles are different from each other. Research results show that there is a restraining effect of the resonant propagation of acoustic wave in liquid with mixed bubbles. The attenuation coefficient and the velocity of acoustic wave in the liquid with mixed bubbles are obviously less than those in the liquid containing bubbles with the same static radius. The nature of the restraining effect is that the resonant vibration of bubbles is weakened due to the interaction between bubbles with different static radii. Some important properties of the restraining effect are investigated for all kinds of liquid systems with mixed bubbles. Moreover, the effect of the viscosity and the rate of cavitation on the restraining effect are also studied. Research results are shown as follows. 1) Comparing with bigger bubbles, resonant characteristic quantities (such as the attenuation coefficient and the velocity of acoustic wave) caused by smaller bubbles can be reduced more obviously; 2) the efficiency of the restraining effect increases with the number of types of bubbles increasing, however, it will gradually reach to a stable value when the number of types of bubbles is large; 3) the bandwidth of the resonant absorption of acoustic wave is dramatically affected by the distribution function of the percentage of the number of bubbles. The bandwidth of the resonant absorption will become large as the percentage of the number of smaller bubbles increases.