Numerical simulation of surfactant-laden emulsion formation in a stirred vessel

The present study aims to establish the transparent interplay among interfacial deformation, surfactant transport, and the underlying flow structure inside a cylindrical stirred vessel equipped with a pitched blade turbine. Massively parallel, three-dimensional, interface-tracking, large eddy simulations of O/W emulsification are deployed to provide detailed, realistic visualization of the intricate interfacial dynamics coupled to the turbulent flow fields, from the onset of impeller rotation through to the attainment of a dynamic steady state. This study investigates the effect of surfactant elasticity (the sensitivity of interfacial tension to the surfactant concentration), the Biot number (the ratio of characteristic desorptive to convective time scale), and Marangoni stresses. Allied to this, the transient drop counts, and their size distribution have been tracked. In particular, the simulations have demonstrated that the presence of surfactant is associated with interfacial rigidification, suppression of end-pinching, and promotion of tip-streaming. The interfacial dynamics in the surfactant-laden system alters the evolution of drop count and their size distribution, where the appearance of the first dispersed drop occurs earlier and a larger number of relatively small drops are observed in comparison to their surfactant-free counterparts carried out in our previous work.