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A constitutive framework for the non-Newtonian pressure tensor of a simple fluid under planar flows

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posted on 2024-07-09, 13:37 authored by Remco Hartkamp, Billy ToddBilly Todd, Stefan Luding
Non-equilibrium molecular dynamics simulations of an atomic fluid under shear flow, planar elongational flow, and a combination of shear and elongational flow are unified consistently with a tensorial model over a wide range of strain rates. A model is presented that predicts the pressure tensor for a non-Newtonian bulk fluid under a homogeneous planar flow field. The model provides a quantitative description of the strain-thinning viscosity, pressure dilatancy, deviatoric viscoelastic lagging, and out-of-flow-plane pressure anisotropy. The non-equilibrium pressure tensor is completely described through these four quantities and can be calculated as a function of the equilibrium material constants and the velocity gradient. This constitutive framework in terms of invariants of the pressure tensor departs from the conventional description that deals with an orientation-dependent description of shear stresses and normal stresses. The present model makes it possible to predict the full pressure tensor for a simple fluid under various types of flows without having to produce these flow types explicitly in a simulation or experiment.

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ISSN

0021-9606

Journal title

The Journal of Chemical Physics

Volume

138

Issue

24

Article number

article no. 244508

Pagination

244508-

Publisher

American Institute of Physics

Copyright statement

Copyright © 2013 AIP Publishing LLC. the published version is reproduced with the permission of the publisher.

Language

eng

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