Study On Cavitation Structure And Dynamic Behavior Of Cavitation Bubbles In Unbounded Domain Under Ultrasonic Excitation

With the development of science and technology,the application of ultrasonic cavitation effect has become increasingly widespread.Studies have found that the rational use of cavitation effects can bring great convenience to human production and life,and the cavitation structure in the liquid and the dynamic behavior of cavitation bubbles will affect the strength of the cavitation effect.Therefore,studying the cavitation structure in the liquid under ultrasonic excitation,the radial motion of cavitation bubbles,and the interaction between cavitation bubbles have certain guiding significance for the better use of ultrasonic cavitation effects.The research object of this paper is the cavitation structure and cavitation bubble in the ultrasonic field.This paper studied the formation and development process of the cavitation structure in the liquid under ultrasonic excitation and the stable cavitation structure,studied the radial dynamic characteristics of the single cavitation bubble under ultrasonic excitation,discussed the physical conditions for obtaining the best cavitation effect,studied the interaction of double cavitation bubbles under ultrasonic excitation,and explored the influence of different factors on the secondary Bjerknes force between double cavitation bubbles and the radial motion characteristics of double cavitating bubbles.The research work will provide technical reference for better use of ultrasonic cavitation effect and enhancement of cavitation effect.Firstly,taking the cavitation structure in the ultrasonically excited liquid as the research object,this thesis used the experimental method to study the formation and development process of cavitation structure in the liquid and the stable cavitation structure under ultrasonic excitation.Established an ultrasonic-excited cavitation experiment platform.The formation and development of cavitation structure in distilled water under ultrasonic excitation were studied.The effects of input power,different frequency combinations and radiation power density on the stable cavitation structure were studied;the three liquid working fluids of distilled water,alcohol and glycerin were changed,and the cavitation structure in different liquid working fluids was studied.Through research,the formation and development process of the cavitation structure of distilled water in different sound fields were obtained;the effects of input power,different dual-frequency combinations and radiation power density on the stable cavitation structure were obtained;the cavitation structure in three liquid working fluids of distilled water,alcohol and glycerin were clarified.Next,taking the single cavitation bubble in the ultrasonic field as the research object,this thesis used the theoretical analysis method to study the radial dynamics of the cavitation bubble under ultrasonic excitation.The radial dynamic equation of ultrasonic cavitation bubble is derived and solved by fourth-order Runge-Kutta method.The effects of initial radius of cavitation nucleus,saturated vapor pressure,hydrostatic pressure and surface tension of liquid on ultrasonic cavitation threshold were studied.The change process of radial motion of cavitation bubble under single-frequency ultrasonic excitation was analyzed,and the effects of ultrasonic parameters,liquid physical parameters and initial radius on the radial dynamic characteristics of cavitation bubble were studied.The radial dynamic characteristics of cavitation bubble under dual-frequency excitation were analyzed,and the enhancement and weakening effect of dual-frequency ultrasound on cavitation effect under different conditions are discussed.The effects of power distribution ratio and dual-frequency phase difference on cavitation effect were further analyzed.The influence of initial radius of cavitation nucleus,saturated vapor pressure,hydrostatic pressure and surface tension on cavitation threshold were obtained through research.The influence of ultrasonic parameters,liquid physical parameters and initial radius on the radial dynamic characteristics of cavitation bubbles were clarified.The enhancement and weakening effect of dual-frequency ultrasound on cavitation effect were discussed,and the physical conditions of dual-frequency combination to strengthen cavitation effect were provided.Finally,taking the double cavitation bubbles in the ultrasonic field as the research object,this thesis used the theoretical analysis method to study studied the interaction of the double cavitation bubbles under ultrasonic excitation.The dynamic equation of ultrasonic-excited double cavitation bubble is derived and solved by fourth-order Runge-Kutta method.Based on this equation,the change process of sub-Bjerknes force of double cavitation bubbles under ultrasonic excitation was analyzed,and the effects of sound pressure,frequency and double bubble spacing on sub-Bjerknes force of double cavitation bubbles with different initial sizes were studied.The radial motion characteristics of double cavitation bubbles under ultrasonic excitation were analyzed,and the effects of sound pressure,frequency and double bubbles spacing on the radial motion characteristics of double cavitation bubbles with different initial sizes were studied.Through the study,the influences of sound pressure,frequency and double bubble spacing on the secondary Bjerknes force of double cavitation bubbles with different initial sizes were obtained.The influences of sound pressure,frequency and double bubble spacing on the radial motion characteristics of double cavitation bubbles with different initial sizes were clarified.There are 94 figures,4 tables and 77 references in this thesis.