Collapse of cavitation bubbles near air bubbles
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Collapse of Cavitation Bubble near Air Bubbles * Jing Luo, Wei-lin Xu , Rui Li State Key Laboratory of Hydraulics and Mountain River Engineering, China
Sichuan University, Chengdu 610065,
(Received July 20, 2018, Revised November 6, 2018, Accepted November 15, 2018, Published online July 9, 2019) ©China Ship Scientific Research Center 2019 Abstract: Cavitation erosion is one of the commonly seen damage modes in water engineering. The study of the interaction among cavitation bubbles, air bubbles and the wall is of great significance for revealing the mechanism of air entrainment to alleviate cavitations and giving better play to the cavitation erosion mitigation effect of aeration. Through high-speed camera shooting, this paper has studied the regular pattern of collapse of cavitation bubbles in the vicinity of the wall and air bubbles. The results have shown that in the vicinity of air bubbles, cavitation bubbles may only collapse towards or backwards air bubbles, while under the dual impacts of air bubbles and the wall, the direction of collapse of cavitation bubbles depends on the vector synthesis of the impacts of air bubbles and the wall. When air bubbles are very close to cavitation bubbles, air bubbles will be penetrated and stretched by cavitation bubbles; when the distance between the two is short enough, cavitation bubbles and air bubbles will connect to form gas-type cavitation bubbles, and the collapse strength will be significantly decreased; when there are two air bubbles near cavitation bubbles, they may even be penetrated successively by cavitation bubbles. Thus it can be seen that during air entrainment to alleviate cavitations, the number of air bubbles is more important than the total air concentration. Key words: cavitation bubble, air bubble, high-speed photography, air entrainment to alleviate cavitation
Introduction Cavitation is common in many engineering applications, such as large cavitation bubbles generated by underwater explosions, millimeter-scale cavitation bubbles that produce cavitation erosion in ships, hydraulic machinery and hydraulic energy dissipation structures, in addition to ultrasonic-induced millimeter-scale cavitation bubbles are used in biomedicine, the material preparation process and chemical production to accelerate chemical reaction rates. Wang et al.[1] gave a very comprehensive review of bubble dynamics and its applications, and pointed out the research difficulties and research derection in this field. Philipp and Lauterborn[2] studied the collapse of
* Project supported by the National Key Research and Development Program of China (Grant No. 2016YFC0401901), the National Natural Science Foundation of China (Grant No. 51409180). Biography: Jing Luo (1983-), Male, Ph. D., Assistant Professor, E-mail: [email protected] Corresponding author: Wei-lin Xu, E-mail: [email protected]
cavitation bubble near the wall and thought that the jet plays a less important role in the cavitation damage, while the bubble-wall dimensionless distance γ (γ = h/Rmax，Rmax is the maxi
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