Size Dependent Orientation of Knudsen Force

Taishan Zhu, Wenjing Ye, Jun Zhang

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Knudsen force acting on a heated microbeam adjacent to a cold substrate in a rarefied gas is a mechanical force created by unbalanced thermal gradients. The measured force has its direction pointing towards the side with a lower thermal gradient and its magnitude vanishes in both continuum and free-molecule limits. In our previous study, negative Knudsen forces were discovered at the high Knudsen regime before diminishing in the free-molecule limit. Such a phenomenon was however not observed in the experiment. In this paper, the existence of such a negative Knudsen force is further confirmed using both numerical simulation and theoretical analysis. The asymptotic order of the Knudsen force near the collisionless limit is analyzed and the analytical expression of its leading term is provided, from which approaches for the enhancement of negative Knudsen forces are proposed. Copyright © 2012 by ASME.
Original languageEnglish (US)
Title of host publicationASME 2012 Third International Conference on Micro/Nanoscale Heat and Mass Transfer
PublisherASME International
Number of pages4
ISBN (Print)9780791854778
StatePublished - Jul 18 2013
Externally publishedYes

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): SA-C0040, UKC0016
Acknowledgements: This work is supported in part by Award No. SA-C0040/UKC0016,made by King Abdullah University of Science andTechnology, and in part by Hong Kong Research GrantsCouncil under Competitive Earmarked Research Grant 621408.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.


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