Soft glassy flow of highly concentrated monodisperse emulsions in microchannels: Layered structure and stairwise velocity profile

Concentrated emulsions with a jammed structure exhibit intricate flow properties, which are not fully comprehended. The flow behavior of a highly concentrated monodisperse emulsion in a microchannel is investigated using dissipative particle dynamics simulations. The local flow curves are analyzed at different sampling resolutions and tracer sizes. The characteristics of the velocity profile obtained at low resolutions agree with experimental observations. However, at high resolutions, the velocity profile deviates from the Herschel-Bulkley model, and stairwise changes appear in the shear zone. Droplet distributions indicate that the layered structure forms within the shear zone and expands with increasing pressure drop. Due to the infrequent exchange of droplets between neighboring layers, a sudden change in velocity arises between them. Additionally, at high pressure drops, the previously uniform droplet distribution in the plug zone transforms into a layered structure as well. Our findings suggest that highly concentrated emulsions under confinement exhibit non-homogeneous structures which affect their flow behavior significantly.