Research on the Visualization of Cavitation Bubble Oscillation within Confined Spaces Based on the High-Speed Photography

The present paper presents a microsecond-level visual investigation of the bubble oscillation near an angular wall within confined spaces based on a high-speed photography experimental system. The inception and collapse times of the bubble are detected at a nanosecond level through the highly sensitive hydrophones, and the pressure fluctuation characteristics during the bubble oscillation are investigated. In addition, the influence mechanisms of the bubble spatial position on their collapse deformation and jet dynamics are explored, and the variation characteristics of the bubble indentation angle, hydrophone signals, and liquid velocity are a quantitatively analyzed. The main conclusions are summarized as follows: Within confined spaces, the bubble oscillation exhibits a disc-shaped cylindrical structure, and a jet pointing towards the wall vertex is formed during the collapse, causing the bubble to split into two parts. As the bubble-wall distance increases, the jet width decreases, which is more pronounced at smaller bubble positional angles. Based on the analysis of the pressure fluctuation signals, three peak signals are identified during the bubble oscillation process, corresponding to the bubble inception, the first collapse, and the second collapse.