The Magnetic Field Effect Of Bubbles In A Fluid

It is of physical significance to study the dynamic behavior of bubbles exposed to an uniform external magnetic field for the field based on cavitation application.In order to fully investigate the dynamic behavior of cavitation bubble in fluids,respectively based on the theory of magnetic field producing additional pressure on the bubble surface and the magnetichydrodynamics(MHD)theory,a modified dynamic equation of a radial vibrating gas bubble immersed in weakly conductive fluid-water and strong conductive fluid-gallium and driven by a sine sound field and exposed to an uniform external magnetic field is established by using the Navier-Stokes equations of incompressible fluid.Then,the magnetic effects of cavitation bubble in water and gallium fluid are studied numerically by using a fourth-order Runge-Kutta method.In this paper,the primary numerical research works are outlined as follows:1)The magnetic effect of cavitation bubble in weakly conductive fluid-water is studied.First,the lower limit of magnetic field which can effectively suppress the gas bubble movement is analyzed theoretically from the point of view of energy.Second,the numerical simulation of bubble vibration process under different intensity magnetic field is carried out.It's found that oscillations of the bubble is inhibited weakly by magnetic field,to have effective inhibition on bubble motion,the magnetic field intensity should be at least greater than 0.5T;Under the action of the strong magnetic field,the vibration amplitude and vibration period of the bubble decrease as the magnetic field increases,and the additional pressure magnetic field produces on the bubble surface increases as the magnetic field increases.2)The magnetic effect of cavitation bubble in strong conductive fluid-gallium is studied.First,the damping effect of the strong magnetic field on the bubble vibration in gallium fluid and the magnetic field effect on the sonoluminescence are studied based on the dynamic equation.Second,the properties of magnetic force are analyzed and simulated numerically,which reveals the possible coupling mechanism between the magnetic field and the bubble.Third,considering the large amount of numerical calculation,for the convenience of calculation,the effects of magnetic field on the stability of bubbles nonlinearly oscillating,the temperature and pressure inside the bubble,and fluid cavitation threshold are studied numerically based on the dimensionless equation.It's found that the the strong magnetic field suppresses the vibration of the bubble and reduces the bubble sonoluminescence intensity;that the magnetic field effect is similar to viscous force effect on the whole.In addition,It is also shown that the magnetic field enhances the stability of bubbles nonlinearly vibrating.With the increase of the magnetic field,the radial nonlinear vibration of the bubble is inhibited,which makes the bubble oscillation more stable.Especially when the magnitude of the electromagnetic force is comparable to the inertial force acting on the bubble interface,it transforms the irregular pulsation of the bubble into a stable regular oscillation.At the same time,the magnetic field causes that the temperature,pressure inside the bubble and liquid cavitation thresholds change.