Turbulence suppression in emulsions

Emulsification involves the mixing of immiscible liquids under flow conditions that are often turbulent, which generates a dense droplet suspension. An accurate description of this system comprises the dynamics of deforming interfaces, allowing for coalescence and breakup of droplets in the possible presence of surfactants that can alter interfacial dynamics. Further, a range of length and time scales of turbulence should be resolved. Simulating an emulsion in a periodic box by means of the lattice-Boltzmann method, we consider different volume fractions (φ) of the dispersed fluid while incorporating a low wavenumber forcing to generate homogeneous, isotropic turbulence in the continuous phase. We find that increasing φ significantly suppresses turbulence at high wavenumbers. The continuous phase becomes turbulent at low φ values (below 20%), and droplets undergo coalescence and breakup depending on the local flow dynamics. At higher φ (around 50%), the two liquids form a complex, entangled structure of essentially connected regions along with many small satellite droplets. Here fine scale flow features are not generated as the turbulence cascade is hindered by the connected interfaces.