Experimental study of microjet impact mechanism under the action of vertical wall direction from single cavitation to triple cavitation bubble

Microjets generated by cavitation bubbles are widely applied in various fields. Most of the existing studies focus on the microjet of a single cavitation bubble, while relatively few examine jets affected by interactions between multiple cavitation bubbles, which are common in practical applications such as chemical engineering. To address this gap, this study designed an experimental device capable of measuring the impact of microjets and conducted experimental investigations on the microjet mechanisms resulting from the superposition of different numbers of cavitation bubbles in the direction perpendicular to the wall. The main findings are as follows: the microjet impact of a single cavitation bubble is primarily influenced by λ1w. For double cavitation bubbles, the impact is jointly affected by λ1w and λ12, with smaller values of both parameters leading to stronger jet impacts. For triple cavitation bubbles, the configurational symmetry plays a crucial role in determining the jet strength. In small particle size suspensions, λ1w < 1 inhibits particle displacement, λ1w ≈ 1 promotes displacement, and λ1w > 1 exhibits both promoting and inhibiting effects. For larger particles, λ1w < 1 enhances the microjet effect and promotes displacement, while λ1w ≈ 1 and λ1w > 1 attenuate the jet effect and inhibit displacement. Force analysis reveals that under λ1w < 1, larger χ values induce stronger forces, while under λ1w ≈ 1, the force is weakened when χ is close to 1. When λ1w > 1, the number of cavitation bubbles becomes the dominant factor, significantly enhancing the force exerted by double cavitation bubbles. This study provides a foundation for research on multiple cavitation bubble microjets.