Research On The Oscillation Characteristics Of Laser-induced Cavitation Bubble With The Assistance Of Electric Field

Cavitation refers to the process of the formation,development,and collapse of cavities(cavitation bubbles)when the local pressure in the liquid drops.Cavitation technology has been applied in different fields such as biomedicine,microelectronics,and water treatment.Electric field assistance is often used to couple cavitation technology to improve its efficiency.However,the oscillation characteristics of cavitation bubble under the assistance of electric field are still unclear.In this dissertation,the oscillation characteristics of the laser-induced cavitation bubble under the assistance of electric field are studied numerically and experimentally.The simulations focus on the pressure and velocity fields near the cavitation bubble under the assistance of electric field.The experiments are performed to analyze the size,velocity,and period of the cavitation bubble under the assistance of electric field.The main research contents and results of this dissertation are as follows:(1)The mechanism of electric field on laser-induced cavitation bubble was theoretically analyzed,and the expression of electric field force acting on the cavitation bubble was obtained according to the electrohydrodynamics.The influence of electric field on the oscillation characteristics of cavitation bubble was explored.Based on dynamics of cavitation bubble,the influence of liquid parameters on cavitation bubble oscillation characteristics was investigated.The theoretical analysis provides a basis for the numerical simulation and experimental study of the laser-induced cavitation bubble oscillation characteristics under the electric field.(2)ANSYS-Fluent was utilized to simulate the laser-induced cavitation bubble in infinite domain under the assistance of electric field.The distributions of electric field strength,electric field force,pressure field and velocity field under different voltages were obtained.The simulation results show that as the voltage increases,the electric field strength and electric field force at the interface of the cavitation bubble increase.When the cavitation bubble is in the expansion stage,the oscillation velocity of the cavitation bubble decreases with the increase of the voltage,and the internal pressure increases as the voltage increases.When the cavitation bubble is in the contraction stage,the oscillation velocity and the internal pressure of the cavitation bubble both increase with the voltage.The changes in the velocity field and pressure field with the voltage both indicate that the electric field suppresses the expansion of the cavitation bubble and promotes the contraction of the cavitation bubble.(3)By establishing an experimental platform of laser-induced cavitation bubble under the assistance of electric field,the effects of laser energy and liquid viscosity on the oscillation of cavitation bubbles in infinite domain and at solid wall surface were studied.The experimental results show that the size and velocity of the cavitation bubbles in the infinite domain and solid wall surface both increase with the increase of laser energy but decrease with increased liquid viscosity.The oscillation period of the cavitation bubble in the liquid with larger viscosity is longer.The viscosity of liquid has a greater influence on the shape of the cavitation bubble at the solid wall surface.The thickness of the boundary layer between the cavitation bubble and the wall surface increases with the increase of (?),so that the shape of the cavitation bubble at the solid wall surface gradually deviate from the hemisphere with the increase of liquid viscosity.(4)The oscillation characteristics of the laser-induced cavitation bubble under electric field were studied through analyzing the size,velocity,and period of the cavitation bubble.The experimental results show that the size and period of the cavitation bubble both decrease with the increase of voltage.The variation of cavitation bubble oscillating speed is consistent with the simulation results,namely the cavitation bubble expansion speed decreases with the voltage and the collapsing speed increases as the voltage increases.The electric field has different influences on the oscillation of the cavitation bubble with different laser energies and liquid viscosities.The electric field has a greater effect on the cavitation bubble with lower laser energy and liquid viscosity.Electric field has a smaller influence on the oscillation of cavitation bubble at the solid wall than that in infinite domain.