Hydrogen Underground Storage Simulations of Multiphase Flows Using Equations of State that Preserve the Correct Surface Tension
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The phenomena of phase change and coexistence of two phases of a substance are of great interest in engineering. Two prevalent numerical techniques for modeling these phenomena are sharp interface and phase field. Sharp interface models assume an abrupt transition at the interface, requiring compatibility relations. In contrast, phase field models offer a smooth transition with a non-zero thickness, eliminating the need for compatibility relations. A single numerical model, utilizing an equation of state (EoS), can describe thermodynamic properties for both phases in phase field models. Some widely used EoSs in hydrogen underground storage simulations are van der Waals [1], Soave-Redlich-Kwong [2] and Peng-Robinson [3]. The major current challenge for the simulation of multiphase and multicomponent flow in permeable media is the effect that EoS has on the effective surface tension. In the present work it is shown that multiphase flow simulations based on traditional equations of state (e.g. cubic EoS) result in surface stresses that are several orders of magnitude larger than the actual ones, when intended to simulate problems of interest in engineering. A modification for cubic EoS is proposed by applying the methodology proposed in [4] with applications to numerical modeling of phase changes in hydrogen underground storage.
