Effect of a single air bubble on the collapse direction and collapse noise of a cavitation bubble

•Air bubble can affect the collapse direction of the cavitation bubble.•Air bubble can attenuate the collapse sound pressure of the cavitation bubble.•The cavitation bubble collapse direction is related to the collapse sound pressure.•Summarized the law of the generation condition of the collapse direction. Studying the influence of a single air bubble on the noise intensity of cavitation bubble collapse has great significance for understanding the mechanism of air entrainment to alleviate cavitation in hydraulic engineering. A cavitation bubble is generated by an underwater low-voltage electric discharge device and interacts with a rising air bubble. Only the cases where the cavitation bubble centroid, air bubble centroid, and hydrophone probes are located approximately on the same horizontal line are analyzed. The results show that the roundness, size and distance of an air bubble have a very important effect on the collapse direction and collapse sound pressure of the cavitation bubble. The findings also reveal that the direction of collapse is closely related to the collapse sound pressure, while the dimensionless distance γ and dimensionless radius roundness ratio ε’ are important parameters that determine the collapse direction of the cavitation bubble.