The migration and adherence of oil droplets on surfaces with different wettability in a laminar flow field

In this paper, the rising trajectories of oil droplets near the substrates of small channels in the laminar flow field were observed using the high-speed camera. Chemical modifications were made on the surfaces of the brass sheets to change the surface properties and the controllable regulation of superoleophilic–superoleophobic wettability gradient was achieved successfully. The adhesion behaviors of the oil droplets on surfaces with different wettability at different flow velocities were observed as well. According to the adhesion behaviors of oil droplets on surfaces with different wettability, a mathematical model was established to analyze water film thinning and adherence of oil droplets on the wall in the laminar flow field. Then the quantitative relationships among the adhesion time tf of oil droplets on different wetting surfaces, oil and water properties, and surface wettability were acquired.