A Verification of the Two-Fluid Model with Interfacial Inertial Coupling

The two-fluid model (TFM) has become a foundational tool in numerical codes used for engineering analyses of two-phase flows in energy systems. However, its completeness remains a topic of debate because improper modeling of interfacial inertial coupling can render the momentum conservation equations elliptic. This issue leads to short wavelength perturbations growing at an infinite rate. This paper demonstrates the practical feasibility of incorporating variational inertial-coupling terms into an industrial CFD TFM code to ensure it is well-posed without the need for regularization. For verification, two special cases with exact analytical solutions of the TFM equations are utilized, exhibiting convergence at a mesh resolution of 1 mm.