Measurements of viscosity, velocity slip coefficients, and tangential momentum accommodation coefficients using a modified spinning rotor gauge

2001 ◽  
Vol 19 (1) ◽  
pp. 317-324 ◽  
Author(s):  
J. A. Bentz ◽  
R. V. Tompson ◽  
S. K. Loyalka
Keyword(s):  
Velocity Slip ◽  
Accommodation Coefficients ◽  
Tangential Momentum ◽  
Slip Coefficients

scholarly journals Extraction of Tangential Momentum and Normal Energy Accommodation Coefficients by Comparing Variational Solutions of the Boltzmann Equation with Experiments on Thermal Creep Gas Flow in Microchannels

Fluids ◽  
2021 ◽  
Vol 6 (12) ◽  
pp. 445
Author(s):  
Tommaso Missoni ◽  
Hiroki Yamaguchi ◽  
Irina Graur ◽  
Silvia Lorenzani
Keyword(s):  
Boltzmann Equation ◽  
Gas Flow ◽  
Recent Experimental Data ◽  
Thermal Slip ◽  
The Boltzmann Equation ◽  
Variational Solutions ◽  
Experimental Apparatus ◽  
Accommodation Coefficients ◽  
Tangential Momentum ◽  
Slip Coefficients

In the present paper, we provide an analytical expression for the first- and second-order thermal slip coefficients, σ1,T and σ2,T, by means of a variational technique that applies to the integrodifferential form of the Boltzmann equation based on the true linearized collision operator for hard-sphere molecules. The Cercignani-Lampis scattering kernel of the gas-surface interaction has been considered in order to take into account the influence of the accommodation coefficients (αt, αn) on the slip parameters. Comparing our theoretical results with recent experimental data on the mass flow rate and the slip coefficient for five noble gases (helium, neon, argon, krypton, and xenon), we found out that there is a continuous set of values for the pair (αt, αn) which leads to the same thermal slip parameters. To uniquely determine the accommodation coefficients, we took into account a further series of measurements carried out with the same experimental apparatus, where the thermal molecular pressure exponent γ has been also evaluated. Therefore, the new method proposed in the present work for extracting the accommodation coefficients relies on two steps. First of all, since γ mainly depends on αt, we fix the tangential momentum accommodation coefficient in such a way as to obtain a fair agreement between theoretical and experimental results. Then, among the multiple pairs of variational solutions for (αt, αn), giving the same thermal slip coefficients (chosen to closely approximate the measurements), we select the unique pair with the previously determined value of αt. The analysis carried out in the present work confirms that both accommodation coefficients increase by increasing the molecular weight of the considered gases, as already highlighted in the literature.

Disk spin-down measurements in the free-molecular flow regime: A new method for measurement of tangential momentum accommodation coefficients

Vacuum ◽  
2016 ◽  
Vol 126 ◽  
pp. 70-79 ◽  
Author(s):  
Tathagata Acharya ◽  
Jordan Falgoust ◽  
Richard Rasmussen ◽  
Michael J. Martin
Keyword(s):  
Flow Regime ◽  
New Method ◽  
Molecular Flow ◽  
Free Molecular Flow ◽  
Accommodation Coefficients ◽  
Tangential Momentum

scholarly journals Higher order slip according to the linearized Boltzmann equation with general boundary conditions

2011 ◽  
Vol 369 (1944) ◽  
pp. 2228-2236 ◽  
Author(s):  
Silvia Lorenzani
Keyword(s):  
Boltzmann Equation ◽  
Collision Operator ◽  
Velocity Slip ◽  
Lattice Boltzmann Methods ◽  
Linearized Boltzmann Equation ◽  
Potential Applications ◽  
Microscale Flows ◽  
Scattering Kernel ◽  
Linearized Collision Operator ◽  
Slip Coefficients

In the present paper, we provide an analytical expression for the first- and second-order velocity slip coefficients by means of a variational technique that applies to the integrodifferential form of the Boltzmann equation based on the true linearized collision operator and the Cercignani–Lampis scattering kernel of the gas–surface interaction. The polynomial form of the Knudsen number obtained for the Poiseuille mass flow rate and the values of the velocity slip coefficients are analysed in the frame of potential applications of the lattice Boltzmann methods in simulations of microscale flows.

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