CFD-PBM simulation of dense emulsion flows in a high-shear rotor-stator mixer

Computational fluid dynamics (CFD) is coupled to population balance modelling (PBM) for the simulation of turbulent drop dispersion and evolving rheology in concentrated oil-water emulsions flowing through a Silverson 150/250MS mixer. Unsteady Reynolds averaged Navier-Stokes (URANS) simulations on a sliding mesh were performed for the fluid dynamics, linking the k − ω SST turbulence model to the population balance equations. The quadrature method of moments (QMOM) approach is used to solve the population balance equations. Breakage kernels based on the multi-fractal theory of intermittent turbulence have been modified to include the effect of turbulent shear and close packing of drops at high phase volume. A previously developed rheological model is used to calculate the emulsion viscosity. Emulsion drop size is shown to be influenced by rotor speed and phase volume fraction. Flow curves characterising the rheology of the emulsion show shear thinning behaviour and viscosity build after a single pass through the mixer.