A numerical study on the effect of wall wettability on film formation in liquid-liquid slug flow

This study numerically investigates the effect of the contact angle on the hydrodynamics of liquid-liquid slug flow in a capillary with an internal diameter of 2.4 mm. The finite volume method is used to solve the Navier-Stokes equation, and the volume-of-fluid method is employed for interface capturing. The contact angle varies from 13 degrees to 169 degrees. The aqueous phase is observed as a continuous medium, the organic phase is in a dispersed phase at low contact angles, and the aqueous phase is dispersed as a medium at high contact angles. The slug velocity is lower at partial wetting contact angles than at fully wetting or non-wetting contact angles. The vorticity inside the slug is higher at extreme contact angles (169 degrees/13 degrees) and becomes very pronounced near the interface. At the Weber number (We(slug) > 0:135), fully developed film is observed. The thickness of this film increases as the interfacial tension decreases. Additionally, the pressure within the slug rises with an increase in interfacial tension.