Motivation

1. 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.