Viscous forces and bulk viscoelasticity near jamming

When weakly jammed packings of soft, viscous, non-Brownian spheres are probed mechanically, they respond with a complex admixture of elastic and viscous effects. While many of these effects are understood for specific, approximate models of the particles' interactions, there are a number of pro...

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Bibliographic Details
Published in:Soft matter 2017, Vol.13 (45), p.8368-8378
Main Authors: Baumgarten, Karsten, Tighe, Brian P
Format: Article
Language:English
Subjects:
Jamming
Mathematical models
Moisture content
Particulates
Scaling
Shear modulus
Viscoelasticity
Viscous damping
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Summary:When weakly jammed packings of soft, viscous, non-Brownian spheres are probed mechanically, they respond with a complex admixture of elastic and viscous effects. While many of these effects are understood for specific, approximate models of the particles' interactions, there are a number of proposed force laws in the literature, especially for viscous interactions. We numerically measure the complex shear modulus G * of jammed packings for various viscous force laws that damp relative velocities between pairs of contacting particles or between a particle and the continuous fluid phase. We find a surprising sensitive dependence of G * on the viscous force law: the system may or may not display dynamic critical scaling, and the exponents describing how G * scales with frequency can change. We show that this sensitivity is closely linked to manner in which viscous damping couples to floppy-like, non-affine motion, which is prominent near jamming. We demonstrate that dynamic critical scaling in foams and emulsions near jamming depends sensitively on the dissipative interactions among particles.
ISSN:1744-683X
1744-6848
DOI:10.1039/c7sm01619k