Cavitation and jetting from shock wave refocusing near convex liquid surfaces

Abstract

We study the physical mechanisms behind the ejection of a liquid jet from a curved free surface, specifically a free-falling water drop. The jet is produced after a spherical shock wave emitted from a micro-explosion created by a focused laser pulse is refocused on the opposite side of its source. The analysis of high-speed videos of the liquid jet formation revealed that it originates from a larger, prolate cavitation bubble created by the strong tension produced after the reflection of the original wave on the air–liquid interface. The shock wave propagation and jet formation are modeled separately with finite volume simulations in OpenFOAM. Initially we study the pressure evolution inside the drop by comparing the numerical simulations with the distribution of bubbles nucleated after the passage of the negative pressure wave. The jet formation dynamics is explained by comparing the experiments with numerical results. The jet velocity is higher if the laser focus is closer to the drop surface.