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 and the dimensionless phase difference Δθ. Specifically, when l≥1.00, weak interaction is observed, and no penetration phenomenon occurs. When l<1.00 and Δθ<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=0.78, the optimal jet-enhancement effect can be achieved by maintaining Δθ=0.67. These findings provide important numerical insights for optimizing jet-enhancement in cavitation-related technologies.