Shock formation in the collapse of a vapor nano-bubble

TL;DR

This paper presents a comprehensive diffuse-interface model for vapor nano-bubble collapse, capturing phase transitions, shock wave formation, and bubble oscillations during cavitation.

Contribution

It introduces a unified model valid across all phases, enabling detailed simulation of non-equilibrium processes during bubble collapse.

Findings

Shock waves are emitted during vapor bubble collapse due to phase transition to supercritical conditions.

Bubble oscillations involve periodic disappearance and reappearance linked to phase transitions.

Shock wave formation results from steepening compression waves during vapor to supercritical transition.

Abstract

In this paper a diffuse-interface model featuring phase change, transition to supercritical conditions, thermal conduction, compressibility effects and shock wave propagation is exploited to deal with the dynamics of a cavitation bubble. At variance with previous descriptions, the model is uniformly valid for all phases (liquid, vapor and supercritical) and phase transitions involved, allowing to describe the non-equilibrium processes ongoing during the collapse. As consequence of this unitary description, rather unexpectedly for pure vapor bubbles, the numerical experiments show that the collapse is accompanied by the emission of a strong shock wave in the liquid and by the oscillation of the bubble that periodically disappears and reappears, due to transition to super/sub critical conditions. The mechanism of shock wave formation is strongly related to the transition of the vapor to supercritical state, with a progressive steepening of the compression wave to form the shock which is eventually reflected as an outward propagating wave in the liquid.