科研之友
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摘要
The force-driven Poiseuille flow of dense gases between two parallel plates is investigated through the numerical solution of the generalized Enskog equation for two-dimensional hard discs. We focus on the competing effects of the mean free path lambda, the channel width L and the disc diameter sigma. For elastic collisions between hard discs, the normalized mass flow rate in the hydrodynamic limit increases with L/sigma for a fixed Knudsen number (defined as Kn = lambda/L), but is always smaller than that predicted by the Boltzmann equation. Also, for a fixed L/sigma, the mass flow rate in the hydrodynamic flow regime is not a monotonically decreasing function of Kn but has a maximum when the solid fraction is approximately 0.3. Under ultra-tight confinement, the famous Knudsen minimum disappears, and the mass flow rate increases with Kn, and is larger than that predicted by the Boltzmann equation in the free-molecular flow regime; for a fixed Kn, the smaller L/sigma is, the larger the mass flow rate. In the transitional flow regime, however, the variation of the mass flow rate with L/sigma is not monotonic for a fixed Kn: the minimum mass flow rate occurs at L/sigma approximate to 2-3. For inelastic collisions, the energy dissipation between the hard discs always enhances the mass flow rate. Anomalous slip velocity is also found, which decreases with increasing Knudsen number. The mechanism for these exotic behaviours is analysed.
- 出版日期2016-5
- 单位西安交通大学
