The shielding effect and interaction mechanism of the air bubble on the cavitation bubble in aeration methods: A numerical study

Revealing the interaction between an air bubble and a cavitation bubble is important to better understand the mechanism of air entrainment to mitigate cavitation on spillway surfaces. The mechanism of interaction between the air bubble and the cavitation bubble during their multi-periodic evolution is investigated based on a compressible three-phase model, considering phase transition and thermodynamic effects. The results indicate that the air bubble has an evident shielding effect on the cavitation bubble, weakening its collapse and prolonging the oscillation period. Two patterns are identified according to whether the merging of the two bubbles occurs or not. The air bubble inhibition impact on the cavitation bubble is stronger in pattern 1 and relatively moderate in pattern 2. To quantify the influence of the air bubble on the cavitation bubble dynamics, the collapse radius, pressure load, and bubble temperature under different dimensionless distances (γ) and sizes (ε) between two bubbles are investigated and analyzed. As γ increases, the cavitation bubble collapse temperature and pressure increase, while the minimum radius decreases. The pressure value for γ = 0.24 reduces by 50.3% compared to the case where only the cavitation bubble collapses. In addition, the collapse temperature decreases with increasing ε. The collapse temperature decreases by 21.6% when ε increases from 0.2 to 0.45. These findings may provide some new references for understanding the macroscopic interactions between the air bubble cluster and the cavitation bubble cluster.