Investigation On Bubble Rising Behaviors Under Uniform Electric Field

The phenomenon of buoyancy driving the rise of bubbles is widespread in many industrial applications.It is extremely important to understand the rising behavior characteristics and laws of bubbles in liquid.Reasonable application of electric field in the liquid-gas multiphase flow system can effectively control the deformation and movement of the bubble,so that the bubble can obtain better rising characteristics and flow state in the liquid.There have been a large number of reports on bubble dynamics.However,the behavioral characteristics of bubbles under the electric field have not been fully grasped,and further research is needed.In this paper,the rising process of two-dimensional bubbles in liquid under uniform electric field is simulated.By tracing the gas-liquid interface,the behavior of single bubble in viscous liquid under the electric field and the effect of the electric field on the coalescing behavior of coaxial bubbles are analyzed.The laws of the change of bubble shape and velocity are summarized.The related achievements of the paper will lay the foundation for the in-depth study of the gas-liquid two-phase flow in electrohydrodynamics(EHD)and the development of related industrial equipment.The main research contents are as follows:A two-dimensional numerical model of bubble rising in liquid under electric field is established.The level-set method is used to capture the topological changes of the interface.The simulated bubble shape and terminal speed are compared with previous experiments,theories and calculation results to verify the feasibility,applicability and accuracy of the model.The deformation process of the bubble under uniform electric field is simulated by numerical calculation,and the bubble shape,rising speed and velocity field distribution are analyzed.The effects of the electric capillaries number(Ca_E)and the dielectric constant ratio(ε~*)on the bubble behavior are studied.The results show that the bubble is deformed along the direction of the electric field by the electric field force.When Ca_E andε~*increase,the electric field force on the bubble increases,and the degree of deformation increases.When the electric field force is large enough,the bubble is broken and satellite bubbles are generated.The vertical uniform electric field accelerates the rise of bubble.The rising process of single bubble under uniform electric field is simulated.The influencing factors of bubble behavior characteristics under electric field are analyzed.The changes of bubble shape and velocity under different density ratio(ρ~*),viscosity ratio(μ~*),Galilei number(Ga)and E?tv?s number(Eo)under the electric field are summarized.The results show that under the electric field,whenρ~*andμ~*reach a certain range,they will hardly affect the bubble shape and velocity.With the Eo number is small and the Ga number is large,the bubble shape oscillates during the ascent.The velocity of the bubble is closely related to the degree of deformation,and a consistent fluctuation state is generated with the change of the degree of deformation.The coalescence process of coaxial bubbles under the electric field is calculated.The evolution of bubble shape,rising speed and velocity field distribution are analyzed.The effects of Ca_E and Ga numbers on the coalescing behavior of coaxial bubbles are studied.The results show that the electric field greatly accelerates the coalescence process of bubbles.As Ca_E increases,the time for bubbles to coalesce is advanced.When Ca_E is large enough,bubbles will be penetrated.As the Ga number decreases,the influence of the electric field on the bubble coalescence process increases.