Temperature-assisted Imploding Sound Field Improves The Cavitation Uniformity

Acoustic cavitation can generate a large number of cavitation bubbles.The high temperature and high pressure in the bubbles and the acoustic microstream,shock waves and jet outside the bubbles can form various physical,chemical and biological effects,which can be applied to ultrasonic cleaning,ultrasonic inactivation,ultrasonic extraction,ultrasonic therapeutics and so on.However,acoustical cavitation has not been widely used in industry up to now.The main reason is that the propagation of point source in non-ideal liquid will face the attenuation caused by sound attenuation and spatial dimension.More seriously,when the liquid is cavitated,a large number of cavitation bubbles generated at the radiation end of the transducer will in turn suppress the propagation of acoustic waves,forming a cavitation shield,and the final range of cavitation is confined to the vicinity of the transducer.Based on the experiment,the sound field distribution in the long tough is studied,and the measured data is fitted.Then the influence of various attenuation on the sound propagation is analyzed and the attenuation coefficients are obtained.In theory,the acoustic field generated by the annular sound source is modeled theoretically.By numerical simulation,the imploding ability of sound waves can offset sound attenuation and the cavitation uniformity can be improved.In addition,this paper also discusses the limitation of the imploding ability of the annular sound source.We believe that the imploding ability of the annular sound source is limited.There is a critical radius beyond which the imploding ability is insufficient to offset the attenuation.Finally,on the basis of annular sound source,this paper proposes to adjust the temperature difference of liquids to change the cavitation threshold of liquids at different locations to ensure that liquids have high cavitation threshold at high sound pressure and have low cavitation threshold at low sound pressure,which effectively improve the uniformity of the cavitation field.