Acoustic cavitation characteristics of bubble in compressible liquid

Abstract

The newly proposed Gilmore-NASG model is used to study the acoustic cavitation characteristics of bubble in compressible liquid under the boundary condition of considering the compressible effect of the liquid, and comparison is made between the results calculated by the Gilmore-NASG model and original KM-VdW model without considering the mass exchange, chemical reaction and heat exchange between the gas in the bubble and the surrounding liquid. The results suggest that, compared with the KM-VdW model, the Gilmore-NASG model which employs a new equation of state to describe the gas, liquid and variations of liquid density and sound velocity due to compressibility, can give a larger compression ratio of cavitation bubble, a deeper collapse depth, higher temperature and pressure peaks. This is mainly because that the co-volume of argon molecule in the NASG equation of state is smaller than that in the VdW equation of state and the effect of the co-volume of water molecule is considered in the NASG equation of state, that is, the Gilmore-NASG model gives more comprehensive consideration to the liquid compressibility. When the bubble collapses violently, the Gilmore-NASG model takes into account the changes of sound velocity caused by the compressibility of the liquid at the bubble wall, effectively avoid the possibility of abnormal increase in the Mach number of the liquid at the bubble wall. With the increase in the driving sound pressure amplitude, the difference between the results given by the two models more and more significantly and the temperature and pressure peaks in the bubble given by the Gilmore-NASG model increase more significantly. With the rise of driving frequency, the difference between the results given by the two models gradually decreases and tends to be consistent under the high-frequency excitation. This indicates that the temperature and pressure in the bubble may arrive at higher values considering the compressibility of the medium caused by the co-volume changes of gas and surrounding liquid at different temperatures and pressures. In the meantime, the Gilmore-NASG model can accurately predict the changes in density, pressure and temperature of the liquid at the bubble wall as well as sound velocity, so this model has advantages in the study of bubble cavitation characteristics under high pressure and the effect of surrounding liquid on bubble cavitation characteristics. There will be important applications for the research on specific issues such as high-intensity focused ultrasound, shock wave lithotripsy treatment and sonochemistry.