https://doi.org/10.1140/epjp/s13360-025-07178-z
Regular Article
Stresses and torque due to Couette flow of micropolar fluid in a striated annulus
Mathematics Programme, National Mathematical Centre, Abuja, Nigeria
a
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Received:
27
August
2025
Accepted:
6
December
2025
Published online:
13
January
2026
Abstract
A micropolar fluid flow in a striated annular passage is studied—the striations are characterized by shallow circumferential protrusions. The annular passage is bounded by smooth rotating cylinder and a stationary striated shaft. The mean stresses and torque are analytically determined as functions of the parameters specifying the effects of microstructure and geometry. The mean shear difference between the non-zero components of the asymmetric stress tensor is determined to examine the variation due to the microstructure. Furthermore, the analysis is extended to elucidate the behavior of the mean couple stress under the interactive effects of the flow parameters. The mean torque acting on the cylinder is evaluated, and the results indicate that the torque is significantly higher for a micropolar fluid compared to its Newtonian fluid counterpart, considered as a limiting case. The torque increases appreciably with the reduction in the gap width of the annular passage, primarily due to the reinforced influence of the bounding surfaces. This boundary effect is further amplified as the wavenumber of the striations increases, owing to the enhanced flow resistance introduced by the surface topography of the shaft. The percentage variation in the torque reveals that the flow of a micropolar fluid requires less torque when the inner shaft is smooth than when it is striated.
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© The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2026
Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
