Influence of liquid density variation on the bubble and gas dynamics of a single acoustic cavitation bubble

The effects of liquid density variation at the bubble surface on the dynamics of a single acoustic cavitation bubble are numerically studied. The Gilmore model together with a comprehensive hydrochemical model is used. The evaporation and condensation of water vapor are included in the hydrochemical model. The simulation results are compared to those resulting from the widely known Keller-Miksis model, which assumes a constant liquid density at the bubble surface. The numerical results for a single argon bubble in water reveal that the pressure and the temperature inside the bubble in collapse phase significantly increase, when the non-constant liquid density is used. These differences increase by raising the ultrasonic amplitude and by decreasing the bubble ambient radius and ultrasonic frequency. More importantly, at higher ultrasonic frequencies, the models give the same results regarding the cavitation dynamics and much more remarkably on the thermodynamic behavior of the bubble contents. Also, it is revealed that the entered number of water vapor molecules into the bubble in expansion phase through evaporation are less than the simulated one by the diffusion limited model. Notably, in the case of an argon bubble in aqueous solution of H₂SO₄(85wt%), a better match between the results of two models is observed. In addition, it is shown that considering the liquid bulk viscosity, arising from the rapid liquid density variation at the end of bubble collapse, in the Gilmore model leads to a slight growth in the collapse strength, temperature, and pressure within the bubble.