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Stress-gradient-induced polymer migration in Taylor-Couette flow.
Elnaz Hajizadeh1, Ronald G Larson
1Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109, USA. rlarson@umich.edu.
Soft Matter
|August 9, 2017
Summary
This study shows polymers accumulate near the inner cylinder in a Taylor-Couette flow, driven by stress gradients. Our continuum theory accurately predicts this polymer migration, confirmed by Brownian dynamics simulations.
Area of Science:
- Polymer physics
- Fluid dynamics
- Rheology
Background:
- Continuum theory for stress-gradient-induced polymer migration.
- Polymer depletion effects at solid boundaries.
Purpose of the Study:
- Apply continuum theory to Taylor-Couette flow.
- Investigate polymer migration patterns and distributions.
- Validate theory with molecular simulations.
Main Methods:
- Systematic perturbation analysis using Weissenberg number (Wi).
- Numerical solution of transport problem coupled with upper-convected Maxwell equation.
- Brownian dynamics (BD) simulations with Hookean dumbbells.
Main Results:
- Polymers accumulate near the inner cylinder in Taylor-Couette flow.
- Strong accumulation observed for Wi > 4.
- No first-order migration contribution due to flow geometry.
- BD simulations confirm theoretical predictions for small dumbbell radii.
Conclusions:
- Continuum theory accurately predicts polymer migration in rotational shearing flow.
- Theory validated by direct molecular simulation.
- Potential applications in lubrication and journal bearing flows.
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