Dense gas flow simulations in ultra-tight confinement

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Abstract

Modelling dense gas flows inside channels with sections comparable to the diameter of gas molecules is essential in porous media applications, such as in non-conventional shale reservoir management and nanofluidic separation membranes. In this paper, we perform the first verification study of the Enskog
equation by using particle simulation methods based on the same hard-sphere collisions dynamics. Our in-house Event-Driven Molecular Dynamics (EDMD) code and a pseudo-hard-sphere Molecular Dynamics (PHS-MD) solver are used to study force-driven Poiseuille flows, in the limit of high gas densities
and high confinements. Our results showed (a) very good agreement between EDMD, PHS-MD, and Enskog solutions across density, velocity, and temperature profiles for all the simulation conditions, and (b) numerical evidence that deviations exist in the normalized mass flow rate versus Knudsen number curve compared to the standard curve without confinement. While we observe slight deviations in the Enskog density and velocity profiles from the MD when the reduced density is greater than 0.2, this limit is well above practical engineering applications, such as in shale gas. The key advantages of promoting the Enskog equation for upscaling flows in porous media lie in its ability to capture the non-equilibrium physics of tightly confined fluids, while being computationally more efficient than fundamental simulation approaches, such as molecular dynamics and derivative solvers.
Original languageEnglish
Article number092003
JournalPhysics of Fluids
Volume32
Issue number9
Early online date1 Sep 2020
DOIs
Publication statusE-pub ahead of print - 1 Sep 2020

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