Effects of curvature on rarefied gas flows between rotating concentric cylinders

Nishanth Dongari, Craig White, Thomas Scanlon, Yonghao Zhang, Jason Reese

Research output: Contribution to journalArticle

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176 Downloads (Pure)

Abstract

The gas flow between two concentric rotating cylinders is considered in order to investigate non-equilibrium effects associated with the Knudsen layers over curved surfaces. We investigate the nonlinear flow physics in the near-wall regions using a new power-law (PL) wall-scaling approach. This PL model incorporates Knudsen layer effects in near-wall regions by taking into account the boundary limiting effects on the molecular free paths. We also report new direct simulation Monte Carlo results covering a wide range of Knudsen numbers and accommodation coefficients, and for various outer-to-inner cylinder radius ratios. Our simulation data are compared with both the classical slip flow theory and the PL model, and we find that non-equilibrium effects are not only dependent on Knudsen number and accommodation coefficient but are also significantly affected by the surface curvature. The relative merits and limitations of both theoretical models are explored with respect to rarefaction and curvature effects. The PL model is able to capture some of the nonlinear trends associated with Knudsen layers up to the early transition flow regime. The present study also illuminates the limitations of classical slip flow theory even in the early slip flow regime for higher curvature test cases, although the model does exhibit good agreement throughout the slip flow regime for lower curvature cases. Torque and velocity profile comparisons also convey that a good prediction of integral flow properties does not necessarily guarantee the accuracy of the theoretical model used, and it is important to demonstrate that field variables are also predicted satisfactorily.
Original languageEnglish
Article number052003
Number of pages17
JournalPhysics of Fluids
Volume25
Issue number5
DOIs
Publication statusPublished - 23 May 2013

Fingerprint

concentric cylinders
rarefied gases
slip flow
gas flow
curvature
flow theory
accommodation coefficient
Knudsen flow
transition flow
rotating cylinders
rarefaction
curved surfaces
data simulation
coefficients
torque
coverings
velocity distribution
trends
scaling
physics

Keywords

  • confined flow
  • flow simulation
  • Knudsen flow
  • Monte Carlo methods
  • rotational flow

Cite this

Dongari, Nishanth ; White, Craig ; Scanlon, Thomas ; Zhang, Yonghao ; Reese, Jason. / Effects of curvature on rarefied gas flows between rotating concentric cylinders. In: Physics of Fluids. 2013 ; Vol. 25, No. 5.
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Effects of curvature on rarefied gas flows between rotating concentric cylinders. / Dongari, Nishanth; White, Craig; Scanlon, Thomas; Zhang, Yonghao; Reese, Jason.

In: Physics of Fluids, Vol. 25, No. 5, 052003, 23.05.2013.

Research output: Contribution to journalArticle

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AB - The gas flow between two concentric rotating cylinders is considered in order to investigate non-equilibrium effects associated with the Knudsen layers over curved surfaces. We investigate the nonlinear flow physics in the near-wall regions using a new power-law (PL) wall-scaling approach. This PL model incorporates Knudsen layer effects in near-wall regions by taking into account the boundary limiting effects on the molecular free paths. We also report new direct simulation Monte Carlo results covering a wide range of Knudsen numbers and accommodation coefficients, and for various outer-to-inner cylinder radius ratios. Our simulation data are compared with both the classical slip flow theory and the PL model, and we find that non-equilibrium effects are not only dependent on Knudsen number and accommodation coefficient but are also significantly affected by the surface curvature. The relative merits and limitations of both theoretical models are explored with respect to rarefaction and curvature effects. The PL model is able to capture some of the nonlinear trends associated with Knudsen layers up to the early transition flow regime. The present study also illuminates the limitations of classical slip flow theory even in the early slip flow regime for higher curvature test cases, although the model does exhibit good agreement throughout the slip flow regime for lower curvature cases. Torque and velocity profile comparisons also convey that a good prediction of integral flow properties does not necessarily guarantee the accuracy of the theoretical model used, and it is important to demonstrate that field variables are also predicted satisfactorily.

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