Topic
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 integral equation for the flow velocity u ( x ; k ) in the steady Couette flow derived from the linearized Bhatnagar-Gross-Krook-Welander kinetic equation is studied in detail both theoretically and numerically in a wide range of the Knudsen number k between 0.003 and 100.0.
31 citations
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TL;DR: In this paper, a revised axisymmetric lattice Boltzmann model is proposed to simulate the flow in microtubes and the wall boundary condition combining the bounceback and specular reflection schemes is used to capture the slip velocity on the wall.
Abstract: Purpose – This paper aims to examine how using lattice Boltzmann method (LBM) aids the study of the isothermal‐gas flow with slight rarefaction in long microtubes.Design/methodology/approach – A revised axisymmetric lattice Boltzmann model is proposed to simulate the flow in microtubes. The wall boundary condition combining the bounce‐back and specular‐reflection schemes is used to capture the slip velocity on the wall. Appropriate relation between the Knudsen number and relax‐time constant is defined.Findings – The computed‐slip velocity, average velocity and non‐linear pressure distribution along the microtube are in excellent agreement with analytical solution of the weakly compressible Navier‐Stokes equations. The calculated‐friction factors are also consistent with available experimental data. For simulations of slip flow in microtube, LBM is more accurate and efficient than DSMC method.Research limitations/implications – The laminar flow in circular microtube is assumed to be axisymmetric. The prese...
31 citations
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TL;DR: In this paper, a flow induced around a sphere with a non-uniform surface temperature in a rarefied gas is investigated using the linearized Boltzmann equation for hard-sphere molecules and the diffuse reflection condition.
Abstract: A flow induced around a sphere with a non-uniform surface temperature in a rarefied gas is investigated using the linearized Boltzmann equation for hard-sphere molecules and the diffuse reflection condition. With the aid of the accurate and efficient numerical method developed by the authors with Aoki, the behaviour of the gas (the velocity distribution function as well as macroscopic variables and force on the sphere) is clarified for the whole range of the Knudsen number. In addition, the solutions of the drag and thermal force (thermophoresis) problems of a spherical particle with an arbitrary thermal conductivity are obtained by appropriate superpositions of the present solution and those of a sphere with infinite thermal conductivity, obtained by the authors with Aoki. The resulting thermal force is compared with various experimental data.
31 citations
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TL;DR: In this paper, a flat membrane based on phase-separated alkali-borosilicate glass with an average pore diameter of 1.4nm was prepared in order to study the transport characteristics in the transition regime between Knudsen and configurational diffusion.
31 citations
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TL;DR: In this paper, half-space problems for the Boltzmann equation are used in order to derive boundary conditions for gas flows past an obstacle at the level of fluid mechanics, and they also appear to describe transitions between flows with strongly contrasted Knudsen numbers.
31 citations