(163a) A Model of Droplet Dispersion in a Turbulent Couette Flow

A model of droplet dispersion in a turbulent flow in a Couette device in which the inner cylinder rotates whereas the outer cylinder is immobile, is developed. Flow regimes, characterized by relatively high Reynolds numbers (>13000), are modeled. Only dilute dispersions are considered. An evolution of droplet size distribution in a Couette device with time is described by an advection-diffusion equation containing a population balance term. Both droplet breakup and coalescence processes are taken into account. A one-dimensional engineering model of a turbulent Couette flow, based on the Prandtl mixing length concept, is employed for calculations of flow velocity, eddy diffusivity and turbulence energy dissipation rate distributions along a Couette device radius. The model equations are solved numerically. Size distributions of droplets, generated in a small-scale Couette device in presence of emulsion stabilizing surfactants, at different rotation speeds and operation durations are measured. The experimental data obtained are compared with the modeling results obtained at neglecting coalescence. The droplet dispersion process in absence of emulsion stabilizing chemicals is also illustrated by computational examples.