Control of the liquid jet formation through the symmetric and asymmetric collapse of a single bubble generated between two parallel solid plates

Abstract

The liquid jet formation can be induced by the asymmetric collapse of the cavitation bubble located nearby boundaries. The jet translational direction and speed can be influenced by the type of the boundary, e.g. solid boundary, free surface or elastic boundary, and the relative locations of the cavitation bubble and the boundary. The mechanisms of the liquid jet formation of a single bubble generated between two parallel solid plates are investigated through the strobe photography experimental method and numerical simulations. It is found that there are two conditions for the bubble to split into two smaller bubbles, which could collapse respectively toward the boundary closer to them and form the liquid jet. The first condition is that the proportion of the maximum bubble diameter to the distance of the two plates, which is denoted as ρ, surpasses the threshold of 0.78. The distance of the bubble center to one of the plates, which is closer to the bubble, is denoted as d. The proportion of d to the maximum bubble radius is denoted as γ. The second condition is that γ surpasses the minimum value, which decreases from 1.1 to 0.3 as ρ grows from 0.78 to 1.35. The size of the separated bubble, that locates closer to one of the plates, decreases as the original bubble moves from the middle toward the other plate. Furthermore, it is found that the maximum jet speed of about 100 m/s appeared when the optimum relative bubble size equals to 1.09 and for the bubble located at the middle of the plates. Therefore, the jet speed and diameter could be adjusted by the relative size and generation position of the bubble between the plates. In this way, the laser energy can be controllably transformed into the directional mechanical force through bubble interactions with a pair of solid plates.