Coalescence and Break-up of large, deformable droplets with different viscoties in turbulent channel flow

The dynamics of large, deformable droplets released in a turbulent channel flow is numerically analyzed. Pseudo-Spectral direct numerical simulations are based on the resolution of the coupled Navier-Stokes and Cahn-Hiliard equations (Phase-Field Model). The droplets have the same density but different viscosity compared to the surrounding fluid. We first focus on droplets coalescence and break-up rate. Two different dynamic are observed, depending on the Weber number $We$, (which measures the ratio between the inertial forces and the surface tension forces) and the viscosity ratio $\lambda$, (ratio between the viscosity of the drop and the continuous phase). For small We, droplets are only slightly deformed and their viscosity does not influence much the coalescence/break-up rate. For larger We, droplets are deformable and their viscosity can significantly alter the coalescence and break-up dynamics.