Dynamic Simulation Of Ultrasonic Cavitation Bubble Under Electrostatic Field

Cavitation reaction caused by ultrasonic action on liquid which can accelerate the outflow of substances in the cell and improve the extraction yield of the natural production.The electric field will make irreversible damage to the cell membrane,promoting the outflow of the target components and increasing the extraction rate of effective components.Ultrasound synergized with electrostatic field extraction is becoming the hotspot among extraction technology,owing to the breaking cell wall of ultrasound and the breaking cell membrane of electrostatic field.In order to further explore the mechanism of ultrasonic collaborative electrostatic field extraction,investigating the influence of electric field on dynamic behavior of cavitation bubble by numerical simulation.First,the ultrasonic cavitation bubble dynamics model was established to explore the dynamic behavior characteristics of bubbles without electrostatic field.Then,the dynamic model of ultrasonic cavitation bubble under electrostatic field was constructed by adding electric field module and electric field control equation.Studying the effect of electrostatic field on the dynamic behavior of cavitation bubble by numerical simulation,so that we can analysis the synergistic of ultrasonic and electrostatic field.This paper is divided into two parts.The first part is simulating the dynamic behavior of ultrasonic cavitation bubble,based on the governing equation of fluid dynamics and VOF model in Fluent 14.5 software environment,adding ultrasound.The morphological of gas-liquid interface was obtained through numerical simulation.According to the numerical simulation results,a standard for evaluating the degree of cavitation reaction has been established.Based on this criterion,the influence of ultrasonic parameters on cavitation reaction was studied,combining the gas-liquid interface of cavitation bubble.Under the situation of other conditions being equal,the numerical results indicate that the cavitation effect is best when the sound pressure amplitude is 3 MPa within the range of 1~5 MPa,and when ultrasonic frequency is greater than 20 kHz,the cavitation effect decreases with the increase of ultrasonic frequency.The results also show that the cavitation effect of dual frequency ultrasound with the same frequency is better than single frequency ultrasound whose sound pressure amplitude is twice as much as dual frequency ultrasound,and the cavitation effect of dual frequency ultrasound with the different frequencies is affected by the frequency difference.The second part is building models and simulating the dynamic behavior of ultrasonic cavitation bubble under electrostatic field.In the basic of ultrasonic cavitation dynamics model,the dielectrophoresis force was added to the momentum equation in the form of body force and the electric field module and electric field control equation were added to the ultrasonic cavitation dynamic model through FLUENT software.The results of the study show that the electrostatic field promotes the cavitation reaction,which is reflected in the change of shape or the increase of kinetic energy for a single cavitation bubble,no matter the coupling of ultrasound flied and electrostatic field was orthogonal or parallel.But the promotion of parallel coupling is better than the promotion of orthogonal coupling.When the coupling of ultrasound flied and electrostatic field was parallel,the direction of the electrostatic field and ultrasound flied codetermine the effect of the electrostatic field which shaping the cavitation bubble or enhancing the kinetic energy.When the coupling of ultrasound flied and electrostatic field was orthogonal,the vertical component of electric force changes the shape of cavitation bubble,and the horizontal component of electric force increases the kinetic energy of cavitation bubble.It was also revealed that the promotion of cavitation reaction is more obvious with the increase of electric field intensity.However,due to the radius of the cavitation bubble is at the micron level,the promotion of the electrostatic field on the cavitation reaction is limited.In order to make the electrostatic field promotion distinct,higher electric field intensity needs to be achieved.