Abstract
When a narrow tube inserted into a static container filled with particles is subjected to vertical vibration, the particles rise in the tube, much resembling the ascending motion of a liquid column in a capillary tube. To gain insights on the particle dynamics dictating this phenomenon – which we term granular capillarity – we numerically investigate the system using the Discrete Element Method (DEM). We reproduce the dynamical process of the granular capillarity and analyze the vertical motion of the individual particles in the tube, as well as the average vertical velocities of the particles. Our simulations show that the height of the granular column fluctuates in a periodic or period-doubling manner as the tube vibrates, until a steady-state (capillary) height is reached. Moreover, our results for the average vertical velocity of the particles in the tube at different radial positions suggest that granular convection is one major factor underlying the particle-based dynamics that lead to the granular capillarity phenomenon.
Highlights
When vertical vibration is introduced into granular systems, the granular materials can exhibit a diversity of interesting phenomena, such as size segregation, density waves, convection and heap formation [1]
A interesting phenomenon is that when a narrow tube inserted into a static container filled with particles is subjected to vertical vibration, the particles rise in the tube
We have presented the simulation of the experimentally reported granular capillarity phenomenon [2,3,4,5,14], which was caused by vertical vibrations of a vertical tube inserted in a container filled with particles
Summary
When vertical vibration is introduced into granular systems, the granular materials can exhibit a diversity of interesting phenomena, such as size segregation, density waves, convection and heap formation [1]. A interesting phenomenon is that when a narrow tube inserted into a static container filled with particles is subjected to vertical vibration, the particles rise in the tube Because this process resembles the rise of a liquid in a capillary tube, we term it granular capillarity. Particle-based numerical models have been developed to simulate the particle dynamics due to the vibrating tube [4] These simulations were performed for one oscillation cycle of the vertically vibrating tube only, and they could not reproduce the rising process of the granular column in the tube observed experimentally in the course of many oscillation cycles. We will show that the granular capillarity effect is associated with granular convection in the system, which is inherent to particulate materials subject to vibrations
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