Mixing dynamics of bilgewater emulsions in Taylor Couette flows

Taylor-Couette (TC) flows between two concentric, rotating cylinders, is ideal for studying the mixing dynamics and stability of emulsions due to the availability of wide variety of hydrodynamic flows. The control of oil discharge concentration at sea from the marine vessels require a better understanding of the stability and formation of Navy standard bilge mix emulsion. In this study, a pre-prepared concentrated oil-water emulsion is directly injected into the annulus of the TC cell containing surfactant-water solution at varied flow conditions to determine the emulsion formation dynamics. The optical properties of the TC cell enables us to visually study the mixing dynamics of the emulsion in solution. It was observed that the dispersion coefficient showed an approximately linear response to increasing inner cylinder speed of TC cell. Samples were collected at different mixing stages from the TC cell and laser diffraction particle analyzer was used to characterize droplet size distribution for these stages. The measurements indicate an initial droplet breakup followed by shear induced coalescence to form a larger median droplet size with time at lower mixing speed. Whereas at higher mixing speeds, the droplet breakup continues under shear and droplet coalescence was delayed.