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When an aqueous drop contacts an immiscible oil film, it displays complex interfacial dynamics. When the spreading factor is positive, upon contact, the oil spreads onto the drop's liquid–air interface, first forming a liquid bridge whose curvature drives an apparent drop spreading motion and later engulfs the drop. We study this flow using both three-phase lattice Boltzmann simulations based on the conservative phase field model, and experiments. Inertially and viscously limited dynamics are explored using the Ohnesorge number $Oh$ and the ratio between the film height $H$ and the initial drop radius $R$ . Both regimes show that the radial growth of the liquid bridge $r$ is fairly insensitive to the film height $H$ , and scales with time $T$ as $r\sim T^{1/2}$ for $Oh\ll 1$ , and as $r\sim T^{2/5}$ for $Oh\gg 1$ . For $Oh\gg 1$ , we show experimentally that this immiscible liquid bridge growth is analogous with the miscible drop–film coalescence case. Contrary to the growth of the liquid bridge, however, we find that the late-time engulfment dynamics and final interface profiles are significantly affected by the ratio $H/R$ . 

ABSTRACT: The presence of asphaltene at both fluid−fluid and fluid−solid interfaces has a wide impact on petroleum recovery processes, for example, by stabilizing oil−gas−water dispersions, adsorbing on reservoir rock surfaces and thus changing their wetting properties, and forming deposits in oil−gas production systems. The Yen-Mullins model for asphaltene behavior in bulk fluids provides a framework for understanding a diverse range of phenomena related to the adsorption dynamics of asphaltene at interfaces and how the adsorbed layers are structured. In this work, we address the relatively less explored parameter, which is accounting for the size and shape of the particles on the interfacial properties and emulsion stability. We discuss our investigations of the asphaltene adsorption and its effects, focusing on oil−water interfaces, and propose a lattice-gas model to explain the experimental observations of the interfacial tension and rheology. 

We study the dynamic wetting of a self-propelled viscous droplet using the time-dependent lubrication equation on a conical-shaped substrate for different cone radii, cone angles and slip lengths. The droplet velocity is found to increase with the cone angle and the slip length, but decrease with the cone radius. We show that a film is formed at the receding part of the droplet, much like the classical Landau–Levich–Derjaguin film. The film thickness $h_f$ is found to decrease with the slip length $\lambda$ . By using the approach of matching asymptotic profiles in the film region and the quasi-static droplet, we obtain the same film thickness as the results from the lubrication approach for all slip lengths. We identify two scaling laws for the asymptotic regimes: $h_fh''_o \sim Ca^{2/3}$ for $\lambda \ll h_f$ and $h_f h''^{3}_o\sim (Ca/\lambda )^2$ for $\lambda \gg h_f$ ; here, $1/h''_o$ is a characteristic length at the receding contact line and $Ca$ is the capillary number. We compare the position and the shape of the droplet predicted from our continuum theory with molecular dynamics simulations, which are in close agreement. Our results show that manipulating the droplet size, the cone angle and the slip length provides different schemes for guiding droplet motion and coating the substrate with a film.