Interaction of a bubble and a bubble cluster in an ultrasonic field
Wang Cheng-Hui (王成会)a b, Cheng Jian-Chun (程建春)a
a Department of Physics and Institute of Acoustics, Nanjing University, Nanjing 210093, China; b Institute of Applied Acoustics, Shaanxi Normal University, Xi'an 710062, China
Abstract Using an appropriate approximation, we have formulated the interacting equation of multi-bubble motion for a system of a single bubble and a spherical bubble cluster. The behavior of the bubbles is observed in coupled and uncoupled states. The oscillation of bubbles inside the cluster is in coupled state. The numerical simulation demonstrates that the secondary Bjerknes force can be influenced by the number density, initial radius, distance, driving frequency, and amplitude of ultrasound. However, if a bubble approaches to a bubble cluster of the same initial radii, coupled oscillation would be induced and a repulsive force is evoked, which may be the reason why the bubble cluster can exist steadily. With increment of the number density of bubble cluster, the secondary Bjerknes force acting on the bubbles inside the cluster decreases due to the strong suppression of coupled bubbles. It is shown that there may be an optimal number density for a bubble cluster which can generate an optimal cavitation effect in liquid for a stable driving ultrasound.
Fund: Project supported by the National Basic Research Program of China (Grant Nos. 2010CB327803 and 2012CB921504), the National Natural Science Foundation of China (Grant Nos. 11174138, 81127901, 11174139, and 11204168), and the Fundamental Research Funds for the Central Universities of China (Grant Nos. GK201002009 and GK201004003), and the Natural Science Foundation of Shaanxi Province, China (Grant No. 2010JQ1006).
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