Confined geometry like silos are widely used for the processing of granular and powder materials which is important in many engineering applications but the discharge flow of granular matter in silos remains an open subject of study. One of a very famous problems in silos is the jamming. A practical solution commonly implemented to solve this problem is the placement of an obstacle just above the outlet. Numerous studies are devoted to the influence of an obstacle on the jamming, but very few of them deal with the influence of this obstacle on the flow rate.
We present an experimental and numerical study on the flow behavior around a cylindrical obstacle during the discharge of granular material in a quasi-2D rectangular silo. As described in the literature, the presence of an obstacle decreases the flow rate (Zuriguel et al.2016. Phys. Rev. E 94, 032302), but the characteristic lengths to be chosen in the flow rate law are not known. We have shown that the presence of the obstacle changes the direction of the flow. In this case the confinement of the granular matter (through the thickness of this silo) is important to take into account in the flow rate law (Zhou et al. 2015. Phys. Rev. E, 92:062204).
To better understand these two effects, a new configuration was designed, with a quasi-2D silo with an outlet in the corner of the silo and an adjustable thickness.
Experimental (flow rate measurements, PIV) and numerical (continuum model) results are presented. We propose an analytic model based on the Janda's law (Janda et al. 2012. Phys. Rev. Lett., 108:248001) to describe our results.