On the Significance of Normal Stress Effects in the Flow of Glaciers
Open Access
- 1 January 1987
- journal article
- research article
- Published by Cambridge University Press (CUP) in Journal of Glaciology
- Vol. 33 (115), 268-273
- https://doi.org/10.1017/s0022143000008832
Abstract
McTigue and others (1985) identified a possible problem in the type of constitutive equation usually used for modeling the creep behaviour of polycrystalline ice. They pointed out that Glen’s flow law necessarily excludes the consideration of normal stress effects, which are of great significance in other disciplines that consider non-Newtonian fluids. Using the second-order fluid (with material parameters evaluated from laboratory data) as a tentative model for ice, they reached the conclusion that normal stress effects may be discernible in natural glacier flow. But, as noted by McTigue and others, the second-order fluid “fails to represent the non-linear rate dependence of ice in shear”; therefore it is in fact not a suitable constitutive model for glacier ice in shearing flow. In this note, parallel to what McTigue and others did for the second-order fluid, we present a similar analysis for (I) the modified second-order fluid and (II) the power-law fluid of grade 2, both of which are constitutive models recently proposed by Man as a tentative generalization of Glen’s flow law. Both models (I) and (II) can represent normal stress effects, and both agree with Glen’s flow law in the prediction of the depth profile of velocity in the steady laminar flow of glaciers. For ease of comparison, the same creep data of McTigue and others are used in quantifying the material parameters in these two models. Both models (I) and (II) predict far less pronounced normal stress effects in glaciers than those estimated by McTigue and others (whose data analysis in fact suffered from inconsistencies and over-parameterization).Keywords
This publication has 13 references indexed in Scilit:
- Normal Stress Effects in the Creep of IceJournal of Glaciology, 1985
- On the Free Energy and Stability of Nonlinear FluidsJournal of Rheology, 1982
- Flow law for polycrystalline ice in glaciers: Comparison of theoretical predictions, laboratory data, and field measurementsReviews of Geophysics, 1981
- Viscoelastic fluid relation for the deformation of iceCold Regions Science and Technology, 1981
- An approximation theorem for functionals, with applications in continuum mechanicsArchive for Rational Mechanics and Analysis, 1960
- The distribution of stress and velocity in glaciers and ice-sheetsProceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences, 1957
- The creep of polycrystalline iceProceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences, 1955
- The flow law of ice from measurements in glacier tunnels, laboratory experiments and the Jungfraufirn borehole experimentProceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences, 1953
- Experiments on the Deformation of IceJournal of Glaciology, 1952
- The Mechanics of Glacier FlowJournal of Glaciology, 1952