Jamming and growth of dynamical heterogeneities versus depth for granular heap flow

Abstract

We report on grain dynamics versus depth for steady-state gravity-driven flow of grains along a heap formed between two parallel sidewalls. Near the surface the flow is steady and fast, while far below there is no flow whatsoever; therefore, a jamming transition occurs where depth is an effective control parameter for setting the distance from the transition. As seen previously, the time-averaged velocity profile along the sidewall exhibits a nearly exponential decay vs depth. Using speckle-visiblility spectroscopy (SVS), we find that velocity fluctuations grow relative to the average on approach to jamming. Introducing an image-based order parameter and the variance in its temporal decay at a given depth, we also characterize the spatially heterogeneous nature of the dynamics and find that it increases on approach to jamming. In particular, the important time and length scales for dynamical heterogeneities are found to grow almost exponentially as a function of depth. These dynamical changes occur without noticeable change in structure, and are compared to behavior found by experiment and simulation elsewhere in order to test the universality of the jamming concept. In particular we find that the size of the heterogeneities scales as the inertia number raised to the -1/3 power, in agreement with two recent simulations.

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• Modeling size segregation of granular materials: the roles of segregation, advection and diffusion
• Rheology of sediment transported by a laminar flow
• Intermittency and Velocity Fluctuations in Hopper Flows Prone to Clogging
• Dynamical heterogeneity in soft particle suspensions under shear
• Differential Variance Analysis of soft glassy materials: a direct method to quantify and visualize dynamic heterogeneities
• Rheology and dynamical heterogeneity in frictionless beads at jamming density
• Relaxation Dynamics of a Granular Pile on a Vertically-Vibrating Plate
• Temperature-pressure scaling for air-fluidized grains on approaches to Point J
• Quantification of plasticity via particle dynamics above and below yield in a 2D jammed suspension
• Laboratory experiment and discrete-element-method simulation of granular-heap flows under vertical vibration
• Concentrated suspensions of Brownian beads in water: dynamic heterogeneities trough a simple experimental technique
• Measurement of surface deformation and cohesion of a granular pile under the effect of centrifugal force
• Rheology and Shear Band Suppression in Particle and Chain Mixtures
• Collective motion of macroscopic spheres floating on capillary ripples: Dynamic heterogeneity and dynamic criticality
• Deformation of a rotated granular pile governed by body-force-dependent friction
• Geometry-dependent constitutive law for granular slow frictional drag