Micro-jet formation induced by the interaction of a spherical and toroidal cavitation bubble
Jaka Mur, Alexander Bußmann, Thomas Paula, Stefan Adami, Nikolaus A. Adams, Rok Petkovšek, Claus‐Dieter Ohl
Abstract
We investigate experimentally and numerically the interaction between a spherical cavitation bubble and a wall-bounded toroidal cavitation bubble. We demonstrate that shock wave focusing following toroidal bubble initiation induces the formation of micro-jets that pierce the spherical bubble in the torus-axis direction away from the surface, strongest in the anti-phase scenario. The velocity of micro-jets is determined by the initial standoff distance of the spherical bubble from the wall and thus from the toroidal bubble, with peak jet velocities approaching 1000 m/s . The micro-jets are triggered by the complex interaction between the torus shock wave and the surface of the spherical bubble. Additionally, the formation of secondary cavitation appears to significantly enhance the micro-jets compared to scenarios without secondary cavitation. Following the formation of micro-jets, a subsequent broad jet pierces the spherical bubble, marking the onset of its collapse. After the collapse, we observe an amplified rebound phase resulting in a more than twofold increase of the bubble volume compared to the initial bubble. • Experiments and simulations of toroidal to spherical cavitation bubble interaction. • Micro-jet initiation is caused by shock wave focusing from the toroidal bubble. • Anti-phase bubble interaction induces micro-jets up to 1000 m/s . • Secondary cavitation significantly effects micro-jet initiation process. • Jetting mechanisms amplify the spherical bubble rebound phase to double initial size.