A framework for interpreting the coarsening and structural evolution of two co‐continuous immiscible viscous fluids

Experimental data from multiple studies show the coarsening of co‐continuous, high interfacial tension fluid systems is driven by capillary instabilities. Coarsening of low interfacial tension systems follows viscosity ratio dependence consistent with the pinch‐off of suspended short filaments although there is uncertainty of this interpretation. The attenuation of coarsening rates for both types follows a common dependence on phase volume fraction and viscosity ratio. Dimensional analysis provides an interpretation of the transition from linear coarsening to slower nonlinear coarsening as a balance of interfacial tension driven flow and a critical level of interconnectivity. The slowdown of coarsening is consistent with the formation of discrete domains which subsequently coexist with the remaining co‐continuous structure. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4140–4156, 2016