Gilmore-NASG Model And Dynamic Characteristics Of Acoustic Cavitation Bubble

The extreme physical and chemical effects of acoustic cavitation bubble are still a very important research topic both theoretically and experimentally.In this paper,the dynamic characteristics of acoustic cavitation single bubble are studied by combining Gilmore equation with NASG equation of state.Firstly,Gilmore-NASG model was used to study the dynamic characteristics of adiabatic cavitation bubble in compressible liquid under the boundary condition of considering the compressible effect of the liquid.The bubble radius,velocity of collapse and rebound,pressure and temperature inside the bubble,as well as the liquid pressure,density,sound velocity,temperature,and Mach number at the bubble wall were calculated with time.The results are compared with the KM-VDW model.The results show that compared with the KM-Vd W model,the Gilmore-NASG model uses NASG equation of state to describe the gas,liquid and the density and sound velocity of liquid caused by compressibility.So the compression ratio,collapse depth,temperature and pressure peak of cavitation bubble are higher.With the increase of the amplitude of the driving sound pressure,the difference between the two models becomes more obvious.With the increase of driving frequency and initial radius,the difference between the two results decreases gradually.Secondly,the NASG equation of state was used to describe the subcritical water for the first time,and the Gilmore-NASG model was used to calculate the radius variation of bubble in subcritical water under different liquid environments.The results are basically consistent with those given in other literatures,which indicates that NASG equation of state can describe the acoustic cavitation of subcritical water.Finally,by combining the NASG equation of state with Gilmore equation,a new Extended Gilmore-NASG model was established,which considered the mass and heat transfer effects at the bubble wall.The bubble radius,velocity of collapse and rebound,the number of water vapor molecules,internal energy,pressure,temperature in the bubble,and the liquid density and sound velocity at the bubble wall were calculated with time.Comparing the calculated results with the results calculated by the Gilmore-NASG model,it can be seen that in the slow expansion stage of the bubble,the pressure reduction promotes the liquid to evaporate,resulting in an increase in the number of water vapor molecules in the bubble,and the evaporated water vapor molecules carry energy to the bubble.At the same time,the heat conduction effect transfers heat from the surrounding liquid to the inside of the bubble,so the expansion radius of the bubble increases,the number of water vapor molecules increases,and the internal energy increases.When the bubble collapses,a large number of water vapor molecules condense due to the sharp increase in pressure.When the water vapor condenses,it absorbs energy.At the same time,the heat conduction effect transfers the energy in the bubble to the surrounding liquid,so the temperature in the bubble decreases,and the liquid density and sound speed at the bubble wall increase.In order to verify the validity of the Extended Gilmore-NASG model,it is compared with the other two existing models.The results show that the Extended Gilmore-NASG model has the same variation trend with the driving sound pressure,driving frequency and initial radius as the other two models,and the Mach number calculation results are better than the other two models.In conclusion,the Extended Gilmore-NASG model can use a state equation to describe the gas,water vapor inside the bubble and surrounding liquid uniformly,accurately predict the change of liquid density and sound velocity at the bubble wall,accurately reflect the covolume effect,and can be applied to a larger pressure and temperature range.