(11b) A Fully Coupled Time Dependent 3-D Axisymmetric Simulation of an Evaporating Sessile Drop

Drying a droplet of a colloidal suspension is a simple method to deposit particles on solid surfaces. Different deposition patterns can be obtained depending on several aspects such as, the evaporation mechanisms, solid substrate-liquid interactions, and colloidal particle concentrations. There are interests in understanding the fluid dynamics during evaporation of the solvent in order to control the distribution of the deposited particles. Studies have been done analytically and numerically with different types of evaporation fluxes at the droplet interface to determine the effect of these fluxes on the fluid flow profile in the droplet. These studies have been done mostly on small droplets where the gravitational force is negligible.

In this work, the full Navier-Stokes equation for the fluid flow in the drop is solved simultaneously with the profile of droplet and mass diffusion of the evaporated solvent. We consider both small and large gravitational bond numbers. The Galerkin finite element method is used to numerically solve the governing equations. The overall thrust of the modeling effort is to predict the motion of particles inside the droplet and the deposition pattern of particles and orientation of rod shaped particles on the substrate.