Theoretical Study On Ultrasonic Cavitation And Effects Of Microbubbles On Sound Propagation

The cavitation effect is a fundamental effect in power ultrasound.Cavitation phenomenon is often accompanied by high temperature and high pressure,jet,acoustic emission,free radicals,high-speed shock waves and other extreme extreme physical phenomena,triggering a variety of secondary effects such as mechanical effects,thermal effects,light effects,chemical effects and other secondary effect.Cavitation mechanism has been successfully applied to ultrasonic cleaning,ultrasonic atomization and other industrial technology.At present,with the development of high intensity focused ultrasound treatment technology,but also face many problems of cavitation effect.In the HIFU treatment,on the one hand the cavitation effect can be combined with the focus of the ultrasound field of mechanical effects,thermal effects and other damage to destroy tumor cells,to prevent the recurrence of metastasis;the other hand,due to cavitation effect is difficult to control and difficult to measure,The degree of cavitation is often difficult to grasp,the treatment also need to avoid the occurrence of a strong cavitation effect on the normal part of the organization caused by accidental injury.In the field of acoustic chemistry and other power ultrasonic applications,the theory of cavitation is also put forward a new requirement,cavitation effect has become an urgent problem in the field of ultrasound.In this paper,the cavitation effect is explored from the perspective of cavitation bubble movement and cavitation temperature and high pressure characteristics.The ultrasonic propagation of cavitation bubbles in liquid is also discussed accordingly.Specific work for(1)Based on the idealized assumption,consider the bubble gas as the ideal gas,the bubble movement model simulation.Changes in environmental parameters,liquid static pressure,surface tension,viscosity and so on have a curb effect on the bubble movement,the larger liquid static pressure,surface tension,viscosity,not prone to transient cavitation.In order to ensure that cavitation occurs,increase the excitation intensity.The higher the vapor pressure content in the bubble or the greater the original radius of the bubble,the easier the cavitation is to occur.(2)As the bubble inside the gas as the actual gas,consider the heat exchange inside and outside the bubble.During the cavitation process,the temperature and pressure changes in the bubble are simulated.Considering the influence of the thermal conductivity on the degree of cavitation,the better the thermal conductivity is,the higher the temperature is.Ultrasonic sound higher,can speed up the progress of cavitation.The higher the sound pressure amplitude,can increase the cavitation strength,cavitation progress is slow.(3)Consider the effect of the presence of cavitation bubbles on the sound propagation in the liquid.Cavitation bubbles will interfere with the propagation of ultrasound in the cavitation liquid,due to the cavitation bubble on the acoustic energy aggregation effect,the sound pressure will appear uneven irregular distribution.The more dense cavitation bubbles in the liquid,the greater the interference with acoustic propagation.The greater the initial bubble,the more intense the sound pressure,will increase the cavitation bubble on the sound transmission interference effect.It is necessary to perform the degassing treatment of the liquid in order to avoid the interference of the cavitation bubbles in the liquid to the sound propagation.