Investigation of the Bubble Dynamics near a Flat Wall with a Protrusion Within Slits

The present study employs high-speed photography and the Kelvin impulse theory to examine the bubble dynamic behaviors near a flat wall with a protrusion within slits. The theoretical model for the bubble collapse is established, and typical experimental phenomena are demonstrated. Qualitative and quantitative analyses are conducted on the bubble dynamic behaviors at both symmetric and asymmetric positions. The correlation between the Kelvin impulse and the bubble centroid movement is examined. The primary findings of this study are summarized as follows: (1) At the symmetrical positions, the direction of the bubble jet is vertically downward. The jet velocity diminishes as the bubble–wall distance increases. It also decreases when the protrusion radius becomes smaller. (2) At the asymmetric positions, as the height of the protrusion increases, the jet direction gradually shifts towards the protrusion. The jet velocity increases with the increasing bubble position angle and bubble–wall distance. (3) The Kelvin impulse direction aligns closely with the bubble centroid movement direction. They both decrease as the bubble–wall distance and the bubble’s position angle increase.