Stokes Flow Simulation of a Droplet on a Super-Hydrophobic Surface

This poster presents the results of a numerical study of the two dimensional motion of a liquid droplet spreading by gravity over a hydrophobic micro-textured surface. The surface topology consists of a periodic array of elevations in the form of rectangles or hemispheres. Spreading of aqueous drops on these surfaces has received significant attention since the droplet can move over the valleys separating the elevations by riding on air confined in the valleys. Such flows – Cassie-Wenzel wetting - are at very large contact angles relative to the plane of the surface (superhydrophobicity) and reduced friction (minimal contact angle hysteresis). The movement of the fluid at the advancing contact line is modeled by providing a slip at the contact line to alleviate the singularity, and a relationship between the contact angle and the velocity of spreading to account for contact angle hysteresis. Fluid movement is analyzed in the limit of zero inertia (Stokes flow) and the boundary integral method is used to obtain numerical solutions for the motion.