Using Cahn–Hilliard mobility to simulate coalescence dynamics

In droplet–droplet collision processes, such as bouncing and coalescence, the following stages can be identified: droplet approach, film drainage, film rupture and the hydrodynamics of coalescence driven by capillary forces. The film rupture process represents a remaining challenge for numerical models intended to simulate the outcome of collisions. It has been proposed that the lattice Boltzmann framework has a mesoscale nature that is suitable for modeling of film rupture. The present work examines diffuse coalescence based on the Cahn–Hilliard free energy for non-uniform systems. No empirical coalescence criterion is needed as the diffuse mechanism is based on a thermodynamic description with its own time characteristics.