![]() The drainage of granular material through an aperture involves the full range of granular behavior from the solid-like static packing, liquid-like dense phase flow, to gas-like dilute free-falling stream. Thus, granular flow in silo has drawn great attentions from the community of engineering sciences and has motivated a mass of experimental and numerical investigations over the years. Characterizing such unique behavior and understanding the underlying mechanisms are obviously helpful for better design and proper operation of silos. The flow of granular assembly in silo involves many intriguing phenomena such as jamming, avalanching, shear banding, density wave, , ], stress pulsation, , ], mixing and segregation, etc. Silo is one of the most important storage and transportation devices for granular materials and has been used in various industrial applications. Our simulation results thus suggest that from the perspective of particle velocity fluctuation, there is no essential difference between granular flows under funnel and mixed discharge modes. And its bottom boundary corresponded to the location of free-fall arch and acted as the source of the resonant motion of particles. Its upper boundary located at the position where the flowing zone started to converge along the vertical direction and was featured as the maximum particle compressive force. The correlation analyses indicate that for these two flow modes, there both existed an intermediate region in the converging part of the flowing zone. Discrete Fourier transform results demonstrate that resonant motion of particles appeared during both funnel and mixed flow discharges. For mixed flow discharge, the flowing zone sharply shrunk when the upper free surface of the material approached a critical height and the discharge mode then shifted to funnel flow mode. For funnel flow discharge, the characteristic width of flowing zone at the early discharge state presented a clear history-dependent feature. ![]() The developments and evolutions of flowing zone and also the characteristics of particle velocity fluctuation during funnel and mixed flow discharges were analyzed and compared by performing 3D Discrete Element Method (DEM) simulations. The primary motivation of this work is to investigate whether there exist fundamental differences between the rheological behavior of particles under these two discharge modes. The drainage of granular assembly from a flat-bottomed silo can be in either funnel flow mode or mixed flow mode.
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