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

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

doi:10.1116/1.1335833

Cited by 28 publications

(15 citation statements)

References 20 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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“…There is very little experimental data available for the torque on a rotating sphere as a function of Knudsen number. Tekasakul et al (1996) and Bentz et al (2001) state that their experimental results are in good agreement with the linearized Boltzmann results of Loyalka (1992) but do not provide sufficient data for a meaningful comparison. Thus, we use the published computational results of Loyalka and fit those results to an analytical expression for z r0 Kn 1 ð Þ.…”

Section: Theoretical Methodsmentioning

confidence: 88%

Analytical expression for the rotational friction coefficient of DLCA aggregates over the entire Knudsen regime

Corson

Mulholland

Zachariah

2017

Aerosol Science and Technology

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We apply a self-consistent field method (Corson et al. 2017c) to calculate the rotational friction coefficient for fractal aerosol particles in the transition flow regime. Our method considers hydrodynamic interactions between spheres in a rotating aggregate due to the linear velocities of the spheres. Results are consistent with electro-optical measurements of soot alignment. Calculated rotational friction coefficients are also in good agreement with continuum and free molecule results in the limits of small (Kn D 0.01) and large (Kn D 100) primary sphere Knudsen numbers. As we previously demonstrated (Corson et al. 2017b) for the translational friction coefficient, the rotational friction coefficient approaches the continuum limit as either the primary sphere size and the number of primary spheres increases. We apply our results to develop an analytical expression Equation (26) for the rotational friction coefficient as a function of the primary sphere size and number of primary spheres. One important finding is that the ratio of the translation to rotational diffusion times is nearly independent of cluster size. We include an extension of previous scaling analysis for aerosol aggregates to include rotational motion. EDITORYannis Drossinos tion coefficient, as a function of primary sphere size and the number of spheres in the aggregate. $ t , J $ O;r , and J $O;c are the translational, rotational, and translation-rotation coupling friction tensors. The translational, rotational, and coupling friction tensors relate the particle translational velocity to the force on the particle, the particle angular velocity to the torque on the particle, and the particle translational or angular velocity to the torque or force on the particle, respectively. Note that the subscript O indicates that the property is described relative to the particle's center of mass, while the dagger symbol represents the transpose of a tensor. These equations apply for creeping flow in the continuum, free molecule, and transition regimes, characterized by very small, very large, and intermediate Knudsen numbers, respectively. For spheres, the Knudsen number is defined as Kn D λ=a, where λ is the gas mean free path and a is the sphere radius.Brenner (1967) demonstrated that a particle's friction and diffusion tensors are connected by a generalized Stokes-Einstein relationship, D $ O D kTM $ O ¡ 1 [4] where the grand mobility and diffusion tensors M $ O and D $ O are defined as M $ O D J $ t J $y O;c J $ O;c J $ O;r 2 4 3 5 [5] D $ O D D $ O;t

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

Abstract: Articles you may be interested inUsing a two-capillary viscometer with preheating to measure the viscosity of dilute argon from 298.15 K to 653.15 K J.

Cited by 28 publications

References 20 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

Analytical expression for the rotational friction coefficient of DLCA aggregates over the entire Knudsen regime

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