The influences of special wetting surfaces on the dynamic behaviors of underwater oil droplet

In this paper, the spread behaviors of the underwater oil droplet on smooth brass substrate and 316L stainless steel (a kind of low-carbon subtype of marine grade stainless steel) substrate were studied from the microscopic view by using high-speed microscopic imaging technology. Chemical modifications were made on the surface of the brass sheet to change the surface properties and the controllable regulation of superoleophilic–superoleophobic wettability gradient surface was achieved successfully. The behaviors of the spreading length and contact angle of the oil droplet rising to different modified surfaces were observed and measured. Taking the influence of water surrounding the oil droplet into consideration, a quantitative relation among droplet dimensionless spreading length, the droplet impact velocity, droplet size, droplet properties, viscosity of the water and surface wettability was acquired through energy analysis for the spreading behaviors of the oil droplet rising to the surfaces. Then an improved spreading dynamic model was established to describe the spreading behaviors of underwater oil droplets on surfaces with different wetting properties.