The spinning rotor gauge: measurements of viscosity, velocity slip coefficients, and tangential momentum accommodation coefficients for N2 and CH4

Bentz, J. A.; Tompson, Robert V.; Loyalka, Sudarshan K.

doi:10.1016/s0042-207x(97)00031-6

Cited by 37 publications

(16 citation statements)

References 18 publications

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“…As a result, several experimental and numerical studies were conducted for determination of TMAC. Experimental research ranged from molecular beam experiments to gas flow experiments in the slip and early transition flow regimes (Arkilic et al 2001;Bentz et al 1997Bentz et al , 2001Goodman and Wachman 1976;Gronych et al 2004;Rettner 1998;Sazhin et al 2001), while the numerical research includes MD simulations of single-molecule interactions with crystalline surfaces (Arya et al 2003;Chirita et al 1993Chirita et al , 1997Finger et al 2007), two-and three-dimensional MD simulations for Kn \ 1 flows (Cao et al 2005;Li 2010, 2011), and coupled MD/ DSMC models (Yamamato et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Molecular dynamics simulations of shear-driven gas flows in nano-channels

Barışık

Beşkök

2011

Microfluid Nanofluid

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Using the recently developed smart wall molecular dynamics algorithm, shear-driven gas flows in nano-scale channels are investigated to reveal the surfacegas interaction effects for flows in the transition and free molecular flow regimes. For the specified surface properties and gas-surface pair interactions, density and stress profiles exhibit a universal behavior inside the wall force penetration region at different flow conditions. Shear stress results are utilized to calculate the tangential momentum accommodation coefficient (TMAC) between argon gas and FCC walls. The TMAC value is shown to be independent of the flow properties and Knudsen number in all simulations. Velocity profiles show distinct deviations from the kinetic theory based solutions inside the wall force penetration depth, while they match the linearized Boltzmann equation solution outside these zones. Results indicate emergence of the wall force field penetration depth as an additional length scale for gas flows in nano-channels, breaking the dynamic similarity between rarefied and nano-scale gas flows solely based on the Knudsen and Mach numbers.

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Section: Introductionmentioning

confidence: 99%

Molecular dynamics simulations of shear-driven gas flows in nano-channels

Barışık

Beşkök

2011

Microfluid Nanofluid

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“…In most macroscopic applications, TMAC is generally assumed to be unity, expressing diffusive reflection on the surfaces. While in many higher Kn experiments [9][10][11][12][13][14][15][16] and molecular dynamics (MD) simulations [17][18][19][20][21][22][23][24][25], the TMAC was reported to be always less than unity. For a variety of gases (mostly noble gases) on metals, semiconductors, or even glass surfaces, the TMAC may be impacted by many factors, such as gas and wall materials [9][10][11][12][13][14][15][16][20][21][22][23][24], incident gas angle and energy [9,11,[17][18][19]21], surface roughness [23], wall temperature [9,11,[17][18][19][21][22][23] and adsorbed layers or gas molecules adsorption [13,…”

Section: Introductionmentioning

confidence: 99%

Effect of gas adsorption on momentum accommodation coefficients in microgas flows using molecular dynamic simulations

Sun

2008

Molecular Physics

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The tangential momentum accommodation coefficient (TMAC), usually used in slip boundary conditions in micro-gas flows, is reported to be always less than unity and greatly influenced by temperature and the strength of gas-wall interactions. According to the definitions of accommodation coefficients, a proper statistical algorithm in non-equilibrium molecular dynamics method was described and verified. In planar Poiseuille gas flow in a smooth microchannel, the TMAC were calculated considering both the effects of temperature and gas-wall interaction. In the simulation processes, more gas molecules began to be adsorbed near walls under the condition of stronger gas-wall interaction and lower temperature. The gas adsorption resulted in a longer gas-wall interaction time so that the TMAC increased. While the gas-wall interaction became much stronger, more and more gas molecules were adsorbed to form an explicit layer above the wall. The full coverage of gas molecules on the wall prevented further adsorption; therefore the TMAC did not keep on increasing as the interaction strength continued to increase. Meanwhile, the normal momentum accommodation coefficient (NMAC) was also calculated according to the definition. In the isothermal flow, the average gas momentum normal to the wall was in complete accommodation with the wall, and the NMAC was almost unity in smooth micro channels.

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“…For the gas-kinetic limited situation, smaller α results in a slower condensation of vapor, which, in turn, leads to a higher supersaturation and stronger nucleation. For N 2 and CH 4 gases, α ranges from ∼0.8 to 1 at room temperature (Bentz et al 1997). The values at low temperatures are not available but are generally higher than 0.8 (see, for example, Wanlass & Eyring 1961;Trilling 1971) and could be as high as unity at Titan's temperatures.…”

Section: Sensitivity Testsmentioning

confidence: 99%

Methane-Nitrogen Binary Nucleation: A New Microphysical Mechanism for Cloud Formation in Titan's Atmosphere

Tsai

Liang

Chen

2012

ApJ

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It is known that clouds are present in the troposphere of Titan; however, their formation mechanism, particle size, and chemical composition remain poorly understood. In this study, a two-component (CH 4 and N 2 ) bin-microphysics model is developed and applied to simulate cloud formation in the troposphere of Titan. A new process, binary nucleation of particles from CH 4 and N 2 gases, is considered. The model is validated and calibrated by recent laboratory experiments that synthesize particle formation in Titan-like environments. Our model simulations show that cloud layers can be formed at about 20 km with a particle size ranging from one to several hundred μm and number concentration 10 −2 to over 100 cm −3 depending on the strength of the vertical updraft. The particles are formed by binary nucleation and grow via the condensation of both CH 4 and N 2 gases, with their N 2 mole fraction varying from <10% in the nucleation stage to >30% in the condensation growth stage. The locally occurring CH 4 -N 2 binary nucleation mechanism is strong and could potentially be more important than the falling condensation nuclei mechanism assumed in many current models.

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The spinning rotor gauge: measurements of viscosity, velocity slip coefficients, and tangential momentum accommodation coefficients for N2 and CH4

Cited by 37 publications

References 18 publications

Molecular dynamics simulations of shear-driven gas flows in nano-channels

Molecular dynamics simulations of shear-driven gas flows in nano-channels

Effect of gas adsorption on momentum accommodation coefficients in microgas flows using molecular dynamic simulations

Methane-Nitrogen Binary Nucleation: A New Microphysical Mechanism for Cloud Formation in Titan's Atmosphere

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