Numerical study of free-fall arches in hopper flows

• DEM simulation of hopper flows were performed on GPUs.
• The free-fall arch structures in hopper flows were plotted by statistical methods.
• Spatial profiles in the hopper flows were investigated statistically.
• The arch structure is consistent with the profiles but different from ideal FFAs.

Beverloo’s law describes the flow rate of grains discharging from hoppers, where the assumption of a free-fall arch (FFA) is very useful in understanding the physical picture of this process. The FFA has been observed in previous experiments but a clear systematic study of the FFA is still necessary. In this paper, dense granular flow in hoppers was studied by numerical simulations, in attempts to explore the free-fall region and its boundary. Generally, the numerical simulation results support the free-fall arch assumption, although the statistical description of the FFA is not exactly equivalent to its strict definition.