Dynamic Heterogeneities in Complex Granular Flows
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Dynamic Heterogeneities in Complex Granular Flows Kuniyasu Saitoh , Ceyda Sanli , Devaraj van der Meer, and Stefan Luding University of Twente , Enschede , the Netherlands. Motivation.

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Motivation

Dynamic Heterogeneities in Complex Granular Flows

KuniyasuSaitoh, CeydaSanli, Devaraj van der Meer, and Stefan Luding

University of Twente, Enschede, the Netherlands

Motivation

Dynamic heterogeneity (DH) is a phenomenological approach to the glass and jamming transitions, where the

characteristic time and length scales show remarkable critical behaviors like critical phenomena and we saw the universality

in many experiments of homogeneously driven granular systems. However, the driven granular systems are sometimes

accompanied by complex flows. Therefore, the criticality in complex granular flows is thetarget of ourstudy.

Experiments

Particles

Polystyrene beads distributed on water

(mean diameter σ=0.62mm, polydisperse)

Driving force

Standing wave generated by a shaker

Control parameter

Area fraction of the particles φ

Interaction between the particles

Capillary force -> “cohesive”

Data

Trajectories projected on 2-dimensions

Units

time = sec. length = σ

Convection

Large scaleconvection

Dynamicheterogeneity

3-dimensional plots of the mobility & susceptibility

Trajectories of grains

Transport by convection

Fluctuation

Coarse Graining (CG) method

Velocity field

Four-point correlationfunction

Time & lengthscales

CG function

or

Diffusion

Mean square displacement

Cross-over time

2

1

Summary

  • Floating grainsdriven by standing wave & transportedby convection.

  • CG methodsuccessfully subtracts the meandisplacements.

  • Crossover time of the MSD diverges near the jamming point.

  • Time andlengthscalesfor DH diverge near the jamming point.

  • Exponentsobtained from our analysis are similartopreviousworks.

  • Our resultsdo notdepend on the choice of CG & overlap functions.


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