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Knudsen number
About: Knudsen number is a research topic. Over the lifetime, 5052 publications have been published within this topic receiving 104278 citations.
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TL;DR: The criteria for the presence of Knudsen forces are outlined and an analytical expression in the form of a linear function of the pressure is given for the force in the free molecular regime.
34 citations
TL;DR: In this article, a rarefied gas flow through a slit in an infinite plane wall, induced by a small pressure difference across the slit, is studied on the basis of the kinetic theory.
Abstract: A rarefied gas flow through a slit in an infinite plane wall, induced by a small pressure difference across the slit, is studied on the basis of the kinetic theory. The system of integral equations for the macroscopic variables (the velocity, density, and temperature of the gas), derived from the linearized Boltzmann–Krook–Welander equation with the diffuse reflection boundary condition, is solved by constructing the Neumann series numerically. The flow velocity, density, and temperature fields of the gas as well as the mass flux through the slit are obtained with good accuracy for various Knudsen numbers. The correction to the free molecular flow result for large but finite Knudsen numbers is also obtained analytically, which gives a continuous transition from the free molecular flow to the present numerical result.
34 citations
TL;DR: In this article, the Boltzmann equation with the Bhatnagar-Gross-Krook collision model (Boltzmann-BGK equation) is employed to describe multiscale flows, i.e., from the hydrodynamic limit to free molecular flow.
34 citations
TL;DR: In this article, the Lattice Boltzmann method is applied to the study of pulsed reactive flows in transitional Knudsen number regimes, namely 0.1 Kn 1.
34 citations
TL;DR: Simulation of the long-range diffusion of ethane in the bed over the Knudsen, transient, and molecular diffusion regimes is consistent with the PFG NMR measurements in yielding tortuosity factors which depend upon the regime of diffusion.
Abstract: Mesoscopic kinetic Monte Carlo simulations and pulsed field gradient nuclear magnetic resonance (PFG NMR) measurements are compared in order to investigate the transport of ethane in a bed of NaX crystals A novel molecular mechanics particle-based reconstruction method is employed for the digital representation of the bed, enabling for the first time a parallel study of the real system and of a computer model tailored to reproduce the void fraction, particle shape and average size of the real system Simulation of the long-range diffusion of ethane in the bed over the Knudsen, transient, and molecular diffusion regimes is consistent with the PFG NMR measurements in yielding tortuosity factors which depend upon the regime of diffusion; more specifically, tortuosity factors defined in the conventional way are higher in the Knudsen than in the molecular diffusion regime Detailed statistical analysis of the computed molecular trajectories reveals that this difference arises in a nonexponential distribution of the lengths and in a correlation between the directions of path segments traversed between collisions with the solid in the Knudsen regime When the Knudsen tortuosity is corrected to account for these features, a single, regime-independent value is obtained within the error of the calculations
34 citations