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Dynamic Vorticity Banding in Discontinuously Shear Thickening Suspensions
R N Chacko1, R Mari2, M E Cates3
1Department of Physics, Durham University, Science Laboratories, South Road, Durham DH1 3LE, United Kingdom.
Physical Review Letters
|September 22, 2018
Summary
Vorticity bands in shear thickening suspensions are unsteady, driven by particle migration and stress concentrations. These dynamic bands are confirmed by both continuum models and particle simulations.
Area of Science:
- Rheology
- Fluid Dynamics
- Suspension Mechanics
Background:
- Steady-state vorticity bands in shear thickening suspensions are theoretically challenged by particle migration due to normal stress imbalances.
- Understanding the dynamics of shear thickening fluids is crucial for various industrial applications.
Purpose of the Study:
- To investigate the possibility and nature of vorticity bands in shear thickening suspensions.
- To develop a model coupling shear thickening with particle migration.
- To validate model predictions with direct particle simulations.
Main Methods:
- Development of a continuum model coupling shear thickening and particle migration.
- Linear stability analysis to identify instability towards banding.
- Nonlinear computations to explore band dynamics.
- Direct numerical simulations of particle suspensions.
Main Results:
- Homogeneous flow is unstable to vorticity banding under specific conditions (negative constitutive slope).
- Nonlinear computations reveal unsteady vorticity bands with spatiotemporal patterns.
- Stress-concentration coupling governs the dynamics of these bands.
- Direct particle simulations confirm the existence and behavior of these dynamical bands, agreeing with the continuum model.
Conclusions:
- Unsteady vorticity bands can arise in shear thickening suspensions.
- Particle migration and stress concentrations are key to the formation and dynamics of these bands.
- The developed continuum model accurately captures the essential physics observed in particle simulations.
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