Zhang, J, Yao, S, Fei, F et al. (2 more authors) (2020) Competition of natural convection and thermal creep in a square enclosure. Physics of Fluids, 32 (10). 102001. ISSN 1070-6631
Abstract
Although natural convection and thermal creep have been well recognized in the continuum and rarefied regimes, respectively, the study of the competition of them in a wide flow regime is very scarce. From a theoretical point of view, natural convection can be described by Navier–Stokes–Fourier (NSF) equations at the macroscopic level, while thermal creep needs descriptions at the molecular level. Therefore, it is quite challenging to capture these two effects simultaneously. In this work, we employ the unified stochastic particle Bhatnagar–Gross–Krook (USP-BGK) method to investigate thermally driven gas flow in a square enclosure. The simulation results obtained by the USP-BGK method are validated by comparing to those from NSF solutions and direct simulation Monte Carlo method for the continuum and transitional regimes, respectively. We find that the flow patterns in the whole flow regime cannot be determined by just one nondimensional parameter, i.e., the Rayleigh number (Ra), but needs two nondimensional parameters, i.e., the Knudsen number (Kn) and the Froude number (Fr), or Kn and Ra. Specifically, small Knudsen and Froude numbers tend to generate natural convection, while large Knudsen and Froude numbers tend to cause thermal creep. Moreover, our simulation results and analyses demonstrate that when Kn < 0.12, thermal creep is dominant if Ra < 1.0, while natural convection is dominant if Ra/Fr > 0.28, or equivalently, L/L* > 1.0, where L is the characteristic length of the system and L* is the equivalent characteristic length of molecules. These findings provide useful guidance for better understanding of the complex gas flows resulting from the competition of natural convection and thermal creep under microscale or low-density conditions such as on Mars.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2020 Author(s). This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. The following article appeared in Zhang, J, Yao, S, Fei, F et al. (2 more authors) (2020) Competition of natural convection and thermal creep in a square enclosure. Physics of Fluids, 32 (10). 102001 and may be found at https://doi.org/10.1063/5.0022260. Uploaded in accordance with the publisher's self-archiving policy. |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Chemical & Process Engineering (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 18 Dec 2020 14:40 |
Last Modified: | 18 Dec 2020 14:40 |
Status: | Published |
Publisher: | AIP Publishing |
Identification Number: | 10.1063/5.0022260 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:169156 |