Ashish Orpe
Department of Physics, Clark University
Email: avorpe@physics.clarku.edu
authors: Ashish V. Orpe and Arshad Kudrolli
Investigation of structure and dynamics of gravity driven dense granular flows with internal imaging
Silos are important industrially for storage and distribution of granular materials. The flow in such systems is dense and characterized by the highly dissipative interaction between the flowing particles. Previous experimental studies have been carried out by observing the flow near the walls owing to the opacity of granular materials. To understand the three dimensional structure and flow dynamics, we fill the silo with glass particles, and a liquid with the same refractive index. The work is focused on the uniform plug-like flow region high above the orifice.
A plane of grains is illuminated using a laser, and dark particles against a fluorescent background are imaged using a digital camera. The particles are identified and tracked over long durations to obtain various flow characteristics. We observe that the side walls induce significant structural order on the granular layer adjacent to the front walls while the bulk is quite disordered. The velocity fluctuation properties in the bulk show remarkable similarities to those for simple elastic hard-sphere liquids. However, those near the walls are qualitatively different and similar to the earlier observations for dry granular flows. By varying the orifice width, we also show that all the flow properties are observed to be flow-rate independent and that the
interstitial fluid has no significant effect. Our results suggest the possibility of modeling dense granular flows using hydrodynamic approaches.
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