Reentrant corner flows of Newtonian and non-Newtonian fluids
作者:
Joel Koplik,
Jayanth R. Banavar,
期刊:
Journal of Rheology
(AIP Available online 1997)
卷期:
Volume 41,
issue 3
页码: 787-805
ISSN:0148-6055
年代: 1997
DOI:10.1122/1.550832
出版商: The Society of Rheology
关键词: Singularity;Molecular dynamics;Corner flow;Slip
数据来源: AIP
摘要:
Computations of the flow of non-Newtonian fluids in the presence of a reentrant corner have a long history of convergence problems, which are believed to originate from a nonsquare-integrable stress singularity. Local flow analyses near such a corner have been inconclusive, due to the nonlinearity and the model dependence of the governing equations. We have used molecular dynamics simulations to compute the flow of both a Newtonian liquid and a model polymer melt through a channel with a reentrant corner, providing an unbiased and convergent calculation. The fluids interact via Lennard–Jones potentials, and for the polymer case we employ FENE chains of length up to 30. For the Newtonian fluid, the shear stress near the corner is found to agree with the Stokes flow prediction of Moffatt. In the non-Newtonian case, the shear stress has a stronger apparent divergence, increasing with velocity but not with chain length, which appears to saturate at an integrable value of approximately 0.8. The molecular origin of the stress enhancement is the additional elongation and rotation of the molecules near the reentrant corner.
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