Capillary pressure (Pc) and phase saturation (Sw) in two-phase flow are well known to be hysteretically related. Thermodynamically-derived multiphase flow theories conjecture that this hysteresis will be lifted if specific interfacial area (anw) is included as a new state variable to create a unique Pc - S - anw surface. Specific interfacial area is defined as the total interfacial area per volume of a porous medium. Several studies have confirmed the existence of a unique Pc - Sw - anw surface under equilibrium conditions for a given porous medium. However, there is only one experimental work in the literature, where the uniqueness of this surface under transient conditions was questioned. However, in the data analysis only the terminal menisci were considered to calculate the specific interfacial area.
In this paper, we investigate the uniqueness of Pc - S - anw surfaces with and without the inclusion of corner fluid-fluid interfacial area, under different dynamic conditions, in two different micro-models bearing two different pore morphologies (granular vs. triangulated). We establish a systematic metric to analyze hysteresis under different hydrodynamic conditions.