Nonlinear acoustic response of bubbles in a cluster and cavitation analysis of bubble-liquid mixture
MO Runyang, HU Jing, WANG Chenghui*, CHEN Shi
(Shaanxi Key Laboratory of Ultrasonics, Shaanxi Normal University, Xi′an 710119, Shaanxi, China)
Abstract:
The oscillation of bubbles inside a cluster is affected by many factors, such as the interaction caused by the secondary radiation of neighboring bubbles, the liquid pressure distribution inside the cluster.A model is developed to describe the coupled oscillation of uniform gas bubbles in a cluster by considering the pulsation of the boundary of the cluster and the secondary radiation of bubbles.Based on the nonlinear analysis of the model by use of progressive approximation, the 1/2 and 1/3 subharmonic responses are investigated.The stable cavitation threshold can be obtained by use of the activating condition of 1/2 subharmonic vibration, and a small value of the threshold can be got for a stable oscillating bubble-liquid system. The 1/3 subharmonic responses can be activated in the region of over three times of resonant frequency. In order to explore the inertial cavitation of a bubble cluster, the radiation acoustic intensity of cavitation bubble in the collapse phase is introduced to describe the cavitation intensity.The numerical analysis results show that the energy transfer ability of the inertial cavitation bubble is three order higher than the stable oscillating bubble. For cavitation bubbles of 3 ~10 μm initial radius, there are higher acoustic energy transfer level and the inertial cavitation threshold is about 1 atm in the low-frequency region. The larger bubble has a lower inertial cavitation threshold relatively. Therefore, the cavitation intensity can be controlled by mediating the amplitude and frequency of the ultrasound wave in the cavitation field.
KeyWords:
bubbles cluster oscillation; cavitation bubbles; nonlinear acoustical response; cavitation threshold