Mechanism and dynamics of hydrodynamic-acoustic cavitation (HAC)

Bubble clusters in hydrodynamic cavitation, acoustic cavitation and hydrodynamic-acoustic cavitation (HAC) are investigated via high-speed photography. By introducing a cavitation state variable, a method for cavitation characterization is proposed. The periodic characteristics and intensity distributions of hydrodynamic cavitation, acoustic cavitation and HAC are quantitatively analyzed using this method. It is found that the range of HAC is evidently widened and the strength of HAC is significantly enhanced compared with hydrodynamic cavitation or acoustic cavitation. Furthermore, we developed a preliminary physical model describing the dynamics of a cavitation bubble in HAC and proposed a mechanism to explain the enhancement of the intensity in HAC.