Experimental Studies On The Dielectric Liquid Motion Induced By Corona Discharge

Electrohydrodynamics is an interdisciplinary subject combining electrodynamics and fluid mechanics.Corona discharge is a common phenomenon in electrohydrodynamics and has a wide range of applications.Needle-plate electrode is a classical electrode structure for studying corona discharge and its related phenomena.It has long been known that corona discharge has a driving effect on liquid in the needleplate electrode.However,some phenomena still lack systematic experimental analysis and theoretical explanation.In this paper,the experimental and theoretical investigation on the corona discharge driving liquid in the needle-plate electrode is carried out and a new droplet control technology is developed.The main reseach topics include:(1)It is proved that the soliton like motion on the surface of dielectric liquid layer caused by corona is not a wave phenomenon.Firstly,the conditions for generating solitary waves in the liquid layer under corona are determined.After velocity analysis,it is suggested that it may not be a speculation of wave phenomenon.By testing its dependence on the propagation medium,interference and reflection,it is found that the wave theory can not describe it,and the influencing factors of its propagation are proposed.(2)The evolution process and critical conditions of the formation of different self-organized patterns in the dielectric liquid layer under the action of corona are determined.The distribution of current density liquid layer characteristic size corresponding to each tissue pattern is given,and the relationship between the characteristic size of each self-organized patterns and each parameter is obtained.By analyzing the force balance conditions of the formation,maintenance and transformation of the self-organized patterns,a mechanical model of one of the patterns was established,and the relationship between the pattern feature size and the liquid layer feature size was explained.(3)For the first time,the phenomenon that corona discharge drives droplets to produce a single unsustainable motion is found,and two conditions that cause the droplets to move are established.By comparing the movement of droplets caused by surface tension such as electrowetting and dielectrophoresis,the uniqueness of droplet motion caused by corona is proved,and the relationship between motion parameters and various conditions is given.The conditions for the conversion of droplets from a single motion to a continuous intermittent linear motion are proposed.(4)The controllability of the movement direction of the droplet caused by corona is proposed.Through the additional electrode structure of conducting hole,two possible directions of droplet movement are realized.The physical mechanism of the effect of the conducting hole on the moving direction of the droplet is proposed,and the relationship between the moving direction and the parameters is quantified.The validity of the physical mechanism is verified by the calculation of the electric field of the additional surface charge with the finite element software COMSOL multiphysics.It is determined that the horizontal component distribution of the electric field on the surface of the plate electrode is the decisive factor of moving direction of droplets.(5)For the first time,the droplet control technology based on corona is proposed,and the complete method of realizing free and controllable movement of droplets under the action of corona is developed,which successfully realizes the long-range and complex path movement of droplets.By changing the conducting hole into a floating conducting ring,the multi-directional movement of the droplets is realized,and the realization conditions are quantified.The range of droplet velocity is obtained,and the influencing factors and physical mechanism of its limit velocity are determined.By comparing the droplet control technology based on corona with other existing technologies,it is concluded that this new technology has the advantages of flexible motion path,simple and universal control method.This technology offers new potential options for a variety of applications involving droplet control.