Modeling of droplet collisions using Smoothed Particle Hydrodynamics

We present an approach to model collisions of different droplets using Smoothed Particle Hydrodynamics (SPH). We consider bouncing and coalescence of two droplets. We only discretize the droplets neglecting the gaseous phase and consider a free surface at the boundaries. We use a modified continuum surface force model for the surface tension at a free surface. The transition between bouncing and coalescence is modeled using a critical Weber number and calculating the loss of kinetic energy during the collision to determine the point of coalescence. We demonstrate numerical convergence and analyze the error of the method for the transition of bouncing and coalescence. We show that the proposed approach is applicable to weakly-compressible SPH and incompressible SPH and compare binary collisions of Newtonian droplets with experimental results from the literature. Finally we apply the model to non-Newtonian droplets that show shear-thinning and shear-thickening behavior and discuss the differences to Newtonian droplets.