Lubricated viscous gravity currents of power-law fluids. Part 1. Self-similar flow regimes

Leung, L. T. and Kowal, K. N. (2022) Lubricated viscous gravity currents of power-law fluids. Part 1. Self-similar flow regimes. Journal of Fluid Mechanics, 940, A26. (doi: 10.1017/jfm.2022.214)

Abstract

We examine the gravity-driven flow of thin films of viscous fluid of power-law rheology, lubricated by another power-law viscous fluid from below. Such flows are relevant to a range of geophysical and industrial settings, including the flow of ice sheets and fast-flowing ice streams lubricated from below by a layer of subglacial till. We model both layers using lubrication theory in two-dimensional and axisymmetric settings, in the limit in which vertical shear provides the dominant resistance to the flow. The flow is self-similar if the power-law exponents, describing the rheology of the two layers of fluid, are equal. We examine the similarity solutions in both geometries and describe the flow in terms of four distinct flow regimes ranging from thin films of viscous fluid coating a more viscous fluid from above, to thin layers of fluid lubricating a more viscous fluid from below. In contrast to the former scenario, a thin film of a low-viscosity fluid strikingly alters the dynamics of a more viscous fluid when it lubricates it from below: the overlying layer thins, the upper surface gradients lessen and most of the shear is confined to the lower layer. Such features amplify, and this flow regime becomes increasingly dominant when the viscous fluids are shear thinning, like the deformation of glacial ice on the large scale. This flow regime is most relevant to the flow of lubricated ice sheets, which thin and accelerate, forming fast-flowing ice streams, when they are well lubricated from below.

• Item Type: Articles
• Additional Information: L.T.L. acknowledges the support of a summer studentship through the Trinity College Summer Studentship Scheme. K.N.K. acknowledges funding through L’Oréal-UNESCO UK and Ireland, For Women In Science (FWIS).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Kowal, Dr Katarzyna
• Authors: Leung, L. T., and Kowal, K. N.
• College/School: College of Science and Engineering > School of Mathematics and Statistics > Mathematics
• Journal Name: Journal of Fluid Mechanics
• Publisher: Cambridge University Press
• ISSN: 0022-1120
• ISSN (Online): 1469-7645
• Published Online: 11 April 2022
• Copyright Holders: Copyright © 2022 The Authors
• First Published: First published in Journal of Fluid Mechanics 940:A26
• Publisher Policy: Reproduced under a Creative Commons License