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° to 169°. 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°/13°) and becomes very pronounced near the interface. At the Weber number Weslug>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.