In the environmental protection and petroleum industries, advanced technologies for separating water and oil are essential. Selective separation of oil and water is an important means of oil and water separation, and superoleophilic and superoleophobic properties of microstructure surface in water have attracted attentions of many researchers. Contact angle is greatly affected by interactions between the liquid and the solid and by chemical characteristics and roughness of a solid surface. For a certain solid surface, surface roughness is a key factor in controlling contact angle.
Contact angle is usually used for study of wetting phenomenon while wetting equations connect experimental measurement variables and wetting phenomenon. Wettability phenomenon can be theoretically explained by wettability equation.
Previous numerical simulations on static contact angle and dynamic contact angle of droplets on surfaces were mainly directed to water droplets in the air. Two-dimensional numerical simulations were used to study static and dynamic properties of water droplets in the air. Numerical simulations on static contact angles and dynamic contact angles of oil droplets in water were rarely found.
Choe Hyon Chol, a researcher at the Faculty of Mechanical Science and Technology, has conducted a 3-dimensional numerical simulation on the underwater apparent contact angle of oil droplets on the microstructure-textured surface by VOF method.
The results are as follows.
The height of a microstructure layer on the surface is an important variable that affects the wettability of a solid surface. When the surface of material is oleophobic in water, an increased microstructure height increases roughness factor, apparent contact angle of an oil droplet and oleophobic nature of surface. When the surface of material is oleophilic in water, an increased microstructure height reduces apparent contact angle and makes the surface more oleophilic.
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