Quantitative analysis of flow dynamics of organic granular materials inside a versatile silo model during time-lapse X-ray tomography experiments

Abstract

Gravitational flows, like silo discharge, vary in mode and are complex to identify since they depend on various parameters, ranging from silo structural properties to granular material properties. Moreover, the way cohesionless particles arrange themselves during the flow is still a matter of study and new experimental approaches are needed. Here, the paper introduces a new versatile silo model that was specially designed for in situ X-ray tomography studies of silo discharge for various flow conditions, namely concentric and eccentric. The presented work focuses on organic granular materials, i.e. sorghum and rice, which present relatively similar physico-mechanical properties but different elongation. The high-quality tomography images combined with adequate image processing strategy allow to unambiguously analyse individual grains dynamic behaviour during silo discharge for different hopper configurations. The paper focuses on the analysis of packing density, coordination number and grain rotation changes during funnel flow. The quantitative analysis essentially shows that hopper eccentricity and particle elongation influence flow dynamics of funnel flow. The proposed experimental methodology is proven to be solid enough to investigate in more detail dynamic phenomena during silo discharge. It can also serve as a strong baseline for numerical calibration and predictions.