Numerical study of supercooled water droplet impacting on cold superhydrophobic surface under electric field

Abstract

The process of ice formation on outdoor electrical equipment is determined by the impact of supercooled droplets on the cold surface under an electric field. Clarifying the impact-freezing of a supercooled droplet under an electric field is important for designing anti-icing surfaces in the power industry. Here, we developed a coupled electro-solidification model by combining the volume of fluid (VOF) method, a dynamic contact angle model, the two-phase electrohydrodynamic (EHD) model, the modified enthalpy solidification method and the nucleation effect. Then, the impact dynamics of a water droplet on a cold superhydrophobic surface under an electric field were studied numerically. The effects of the electric field intensity, Weber number, initial droplet temperature and conductivity on the spreading factor βm and the freezing fraction αad are analyzed. By specifically considering the effect of the electric field enhancing the water to freeze, the bottom filament is successfully recreated in the simulation. This phenomenon was first reproduced in our simulation, and it would significantly increase the probability of icing on the cold surface under the electric field, even on the superhydrophobic surface. Finally, based on the numerical results and published experimental data, we fit the freezing fraction relation of the supercooled water droplet impinging on cold superhydrophobic surface under the electric field, which can be used to predict the icing growth and prevention of icing on transmission lines. The numerical model developed here can also be directly used to simulate ice growth and guide the design of anti-icing surfaces in power transmission systems.