Dynamic densification of wet granular materials in continuous dense flows under gravity

Abstract

The continuous granular flow under gravity extensively exists in chemical processes, and the dynamic behaviors of granular flow under different gas–liquid environments are investigated by synchronous slide‐type high‐speed photography. Results show that a hexagonal arrangement is observed after three‐stage densification in wet granular flow, while these structures are almost absent in the dry system. Further analysis shows that under the induction of liquid, the special cavity collapse in stage І is the pre‐condition of granular densification, and the subsequent densification in stage ІІ for the first time gives the experimental proof for the hypothesis that energy barriers exist and depend on the friction characteristics, and the cage effect in stage ІІІ provides a guarantee for the formation of a hexagonal contact network. Besides, three‐stage densification in the three‐phase system mainly occurs in the region with low gas and liquid velocities (G* < 0.716 and L* < 0.023 in this work).