Quasi-static simulation of droplet morphologies using a smoothed particle hydrodynamics multiphase model

Numerical simulation of the morphology of a droplet deposited on a solid surface requires an efficient description of the three-phase contact line. In this study, a simple method of implementing the contact angle is proposed, combined with a robust smoothed particle hydrodynamics multiphase algorithm (Zhang 2015). The first step of the method is the creation of the virtual liquid-gas interface across the solid surface by means of dummy particles, thus the calculated surface tension near the triple point serves to automatically modulate the dynarnic contact line towards the equilibrium state. We simulate the evolution process of initially square liquid lumps on fiat and curved surfaces. The predictions of droplet profiles are in good agreement with the analytical solutions provided that the macroscopic contact angle is accurately implemented. Compared to the normal correction method, the present method is straightforward without the need to manually alter the normal vectors. This study presents a robust algorithm capable of capturing the physics of the static welling. It may hold great potentials in bio-inspired superhydrophobic surfaces, oil displacement, microfluidics, ore floatation, etc.

The co-effect of microstructures and mucus on the adhesion of abalone from a mechanical perspective

Reliable and reversible adhesion underwater is challenging due to the water molecules and weak layers of contaminants at the contact interface,which requires to deepen the un-derstanding of wet adhesion of biological surfaces.Herein,the co-effect of microstruc-tures and mucus of abalone foot on wet adhesion is investigated from both experimental and theoretical perspectives.The morphologies,adhesion force and coefficient of friction indicate that the mucus in adhesion zone is crucial for successful attachment of abalone based on capillary forces and viscous forces,and the mucus in non-adhesion zone with lower adhesion force and friction coefficient may behave as a lubricant for the loco-motion.The theoretical calculation manifests that the microstructures may help abalone to form multiple liquid bridges with the secreted mucus,and significantly increase the wet adhesion force of abalone.These findings will bring profound views into the underlying mechanisms of biological surface adhesion.