Cavitation occurring in hydraulic machinery often involves the interaction of multiple bubbles, and the collapse jets of unequal-sized bubble pairs can significantly affect local loads and material damage. Focusing on this issue, the present work investigates the jet behavior of synchronized and unequal-sized dual cavitation bubbles in an infinite liquid. Employing the OpenFOAM platform, the collapse morphologies, jet structures, velocity-field characteristics, and energy evolution of dual cavitation bubbles are analyzed. Based on characteristics and coexistence state of jets, four jet patterns have been identified: (1) counter-jets, (2) non-coexisting counter-jets, (3) large bubble-directed jet, and (4) converging jets. During collapse, increasing the bubble spacing weakens the coupling between bubbles and reduces centroid migration and interface asymmetry. The collapse of small bubble induces intense local pressure gradients and shear flows, thereby promoting the accumulation of kinetic energy and dissipation of energy in large bubble prior to the final collapse and enhancing the collapse intensity. These findings provide mechanistic insight and regime maps that are useful for predicting cavitation-induced damage in hydraulic machinery and related applications.
Zhang et al. (Sun,) studied this question.