Electrohydrodynamic instability and disintegration of low viscous liquid jet

Abstract

The simple-jet mode can be developed from dripping, dripping faucet (transition), and jetting when subjected to a sufficient strong electric field caused by a needle-plated electrode. In the present work, the instability and disintegration of an electrified jet of anhydrous ethanol in the electrohydrodynamic simple-jet mode are visualized by a high-speed camera. A systematic analysis and description on the evolution of the breakup morphology of the charged jet in the simple-jet mode was carried out. In the dripping mode at low Weber number, the unstable simple-jet occurs, while the stable simple-jet mode happens as Weber number higher than critical value. In a dripping faucet and jetting regime, the simple-jet mode can easily take place, and jet undergoes typical breakup modes including varicose, whipping, whipping assisted bifurcation, and ramified instabilities as electric potential increases. The growth rate of the maximum perturbation of the zero-, first-, and second-order surface waves determines the type of the instabilities. The operating window of the simple-jet mode is presented to indicate that the simple-jet mode only operates in the suitable range of Weber number and electric Bond number. The spray characteristics, including envelope angle, droplet size, and the stable length of the electrified jet, have been explored to demonstrate that the uniform drops could be generated in the simple-jet regime. The evolution from the cone-jet to the simple-jet mode is also observed when a special hemispherical nozzle is used. For an almost stable electric potential, the cone-jet can gradually transform into the simple-jet with an increase in the liquid flow rate.