Numerical investigation on jet-enhancement effect and interaction of out-of-phase cavitation bubbles excited by thermal nucleation

Understanding the formation and interactions of out-of-phase cavitation bubbles is crucial for comprehensively exploring cavitation processes in both nature and engineering applications. In this study, a numerical model for the interaction of out-of-phase cavitation bubbles is developed using the hybrid thermal lattice Boltzmann method, where cavitation bubbles are solely excited by thermal nucleation. Furthermore, a new temperature distribution function for thermal nucleation is proposed, enabling a more stable generation of cavitation bubbles. By comparing the results with those obtained from the Rayleigh–Plesset equation incorporating the thermal effect term, the validity of the thermal nucleation model has been verified. Subsequently, the validity of two out-of-phase cavitation bubbles model is experimentally verified, and the dynamic and thermodynamic behaviors of two out-of-phase cavitation bubbles are systematically investigated. The behaviors are primarily influenced by the dimensionless bubble spacing $l_0^{\ast }$ and the dimensionless phase difference $\Delta {\theta }^{\ast }$. Specifically, when $l_0^{\ast }\ge 1.00$, weak interaction is observed, and no penetration phenomenon occurs. When $l_0^{\ast }<1.00$ and $\Delta {\theta }^{\ast }<0.50$, strong interaction is observed, and a penetration phenomenon occurs. Finally, the jet-enhancement effect of two out-of-phase cavitation bubbles is explored. The results indicate that when $l_0^{\ast }=0.78$, the optimal jet-enhancement effect can be achieved by maintaining $\Delta {\theta }^{\ast }=0.67$. These findings provide important numerical insights for optimizing jet-enhancement in cavitation-related technologies.