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


Dive into the research topics of 'Size Dependent Orientation of Knudsen Force'. Together they form a unique fingerprint.

Cite this