Influence of multiple air bubbles on the collapse strength of a cavitation bubble

•Air bubbles can extend the oscillation time of a cavitation bubble.•Air bubbles can split a cavitation bubble into two subcavitation bubbles.•Concluding the mechanism of air entrainment alleviating cavitation erosion.•Three different arrangements of three bubble–bubble relative sizes are demonstrated. Studying the effect of multiple air bubbles on the collapse strength of a cavitation bubble can aid in understanding the mechanism of air entrainment alleviating the cavitation erosion and enhance the aeration effects in hydraulic engineering. A cavitation bubble is generated by the spark-generated system. Air bubbles are arranged in three manners: two air bubbles on the same side, one air bubble on either side, and four air bubbles around. The intensity of the cavitation bubble collapse noise is estimated using a hydrophone. The results show that, in the range in which the air bubbles can interact with the cavitation bubble, the relative distance, size, and number of the air bubbles and cavitation bubble can considerably influence the migration direction, the oscillation time and the collapse sound pressure of the cavitation bubble. For the first time, it is observed that air bubbles split a cavitation bubble into two subcavitation bubbles. In aeration methods, under the same aeration concentration, the air bubbles should be small, numerous, and evenly distributed.