Investigation of Droplet Size Distribution for Liquid-Liquid Emulsions in Taylor-Couette Flows
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In this paper, we investigate oil-in-water emulsions in a Taylor-Couette flow. A high speed camera was employed to record the formation of those emulsions and image processing was used to obtain the diameter of the droplets. No surfactants were added in order to study the pure effect of the fluid dynamical forces on the droplets. The results for three different oil-in-water emulsions show that the Sauter mean diameter considerably depends on the local shear rate and the material properties and that the droplet size distribution follows a log-normal distribution We, therefore, propose to express the Sauter mean diameter normalized by Prandtl mixing length in terms of a correlation, which is based on the Kolmogorov turbulence theory. This correlation subsequently depends on the local shear rate and the material properties such as viscosity, density and interfacial tension. The predictions of the correlation show fairly good agreement with the experimental measurement the Sauter mean diameter. Finally, comparing the predictions of the correlation to the data presented by Eskin et al. [Chem. Eng. Sci. 161 36-47; 2017] shows excellent agreement in the case, where the droplets are larger than the Kolmogorov length scale.