Mushroom shaped bubbles and the jet of 1000 m/s

Abstract

The dynamics of a single, laser-induced cavitation bubble on top of a solid cylinder is studied both experimentally and numerically. When the bubble is generated close to the flat top along the axis of the cylinder and its maximum radius exceeds the one of the flat top surface, it collapses in the form of a mushroom with a footing on the cylinder, a long stem and a hat-like cap typical for a mushroom head. The head may collapse forming a thin, fast liquid jet into the stem, depending on bubble size and bubble distance to the top of the cylinder. The parameter space of initial distance to the cylinder, bubble size and cylinder radius is scanned numerically, partly compared to experiments and evaluated for the resulting jet velocity and jet length and other features. The results represent a contribution to understand the behavior of bubbles collapsing close to structured surfaces, in particular, how thin, fast jets are generated. An indication how the fast jet plays a role for erosion is given, as well.