scispace - formally typeset
Search or ask a question
Topic

Knudsen number

About: Knudsen number is a research topic. Over the lifetime, 5052 publications have been published within this topic receiving 104278 citations.


Papers
More filters
Journal ArticleDOI
TL;DR: The nonlinear Bhatnagar, Gross, and Krook kinetic equation is solved for boundary conditions leading to planar Couette flow and heat transport and in the limit of zero Knudsen number but arbitrary uniformity parameter, an exact ``normal'' solution is obtained.
Abstract: The nonlinear Bhatnagar, Gross, and Krook [Phys. Rev. 94, 511 (1954)] kinetic equation is solved for boundary conditions leading to planar Couette flow and heat transport. In the limit of zero Knudsen number but arbitrary uniformity parameter (shear rate), an exact ``normal'' solution is obtained. The velocity distribution function is illustrated explicitly for states far from equilibrium. At finite Knudsen number, the distribution function is obtained from numerical solution of a set of nonlinear, singular integral equations. Results are presented for a range of values of the Knudsen number and uniformity parameter. The approach to a normal state is studied with a determination of the hydrodynamic profiles, velocity slip, shear viscosity, and a nonlinear Burnett transport coefficient.

37 citations

Journal ArticleDOI
TL;DR: In this paper, an analytical approach based on linearized and semi-linearized forms of the regularized 13-moment equations (R13 equations) for rarefied gas flow in a parallel-plate micro-channel is considered, where a streamwise constant temperature gradient is applied in the channel walls.
Abstract: Rarefied gas flow in a parallel-plate micro-channel is considered, where a streamwise constant temperature gradient is applied in the channel walls. An analytical approach to the problem is conducted based on linearized and semi-linearized forms of the regularized 13-moment equations (R13 equations), which are a set of macroscopic transport equations for rarefied gases at the super-Burnett order. Typical nonequilibrium effects at the boundary, i.e., velocity slip, temperature jump, and formation of Knudsen boundary layers are investigated. Nonlinear contributions lead to temperature, density, and normal stress profiles across the channel which are not reported elsewhere in literature.

37 citations

Journal ArticleDOI
TL;DR: In this paper, the performance of a microelectromechanical in-plane Knudsen radiometric actuator, a self-contained device having thermal force generation, sensing, and tuning mechanisms integrated onto the same platform, is evaluated in terms of a non-dimensional force coefficient.
Abstract: The generation of forces and moments on structures immersed in rarefied non-isothermal gas flows has received limited practical implementation since first being discovered over a century ago. The formation of significant thermal stresses requires both large thermal gradients and characteristic dimensions which are comparable to the gas molecular mean free path. For macroscopic geometries, this necessitates impractically high temperatures and very low pressures. At the microscale, however, these conditions are easily achieved, allowing the effects to be exploited, namely, for gas-property sensing and microstructure actuation. In this letter, we introduce and experimentally evaluate performance of a microelectromechanical in-plane Knudsen radiometric actuator, a self-contained device having Knudsen thermal force generation, sensing, and tuning mechanisms integrated onto the same platform. Sensitivity to ambient pressure, temperature gradient, as well as gas composition is demonstrated. Results are presented in terms of a non-dimensional force coefficient, allowing measurements to be directly compared to the previous experimental and computational data on out-of-plane cantilevered configurations.

37 citations

Journal ArticleDOI
10 Oct 2013-Langmuir
TL;DR: An efficient computational procedure for the rapid prediction of the self-diffusivity of gas molecules in nanoporous materials by a combination of the Knudsen model, Rosenfeld's excess-entropy scaling method, and a classical density functional theory (DFT).
Abstract: We present an efficient computational procedure for the rapid prediction of the self-diffusivity of gas molecules in nanoporous materials by a combination of the Knudsen model, Rosenfeld’s excess-entropy scaling method, and a classical density functional theory (DFT). The self-diffusivity conforms to the Knudsen model at low density, and the effects of intermolecular interactions at higher densities are accounted for by Rosenfeld’s excess-entropy scaling method. The classical DFT provides a convenient way to calculate the excess entropy used in the scaling analysis. The hybrid computational procedure has been calibrated with MD simulation for the adsorption of H2, He, Ne, and Ar gases in several nanoporous materials over a broad range of pressure. It predicts adsorption isotherms and different types of diffusion behavior in excellent agreement with the simulation results. Although the simulation of gas diffusion in nanoporous materials is extremely time-consuming, the new procedure is computationally very...

37 citations

Journal ArticleDOI
TL;DR: In this paper, numerical simulations are performed to investigate the capability of the Knudsen thermal force for the detection of sulfur dioxide in CH4/SO2 gas mixture and reveal the main mechanism of force generation inside the device.

37 citations


Network Information
Related Topics (5)
Reynolds number
68.4K papers, 1.6M citations
85% related
Heat transfer
181.7K papers, 2.9M citations
84% related
Turbulence
112.1K papers, 2.7M citations
84% related
Boundary value problem
145.3K papers, 2.7M citations
82% related
Particle
96.5K papers, 1.9M citations
80% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023112
2022236
2021168
2020163
2019190
2018172