Abstract
We experimentally analyze the effect that particle size has on the mass flow rate of a quasi two-dimensional silo discharged by gravity. In a previous work, Janda etal. [Phys. Rev. Lett. 108, 248001 (2012)PRLTAO0031-900710.1103/PhysRevLett.108.248001] introduced a new expression for the mass flow rate based on a detailed experimental analysis of the flow for 1-mm diameter beads. Here, we aim to extend these results by using particles of larger sizes and a variable that was not explicitly included in the proposed expression. We show that the velocity and density profiles at the outlet are self-similar and scale with the outlet size with the same functionalities as in the case of 1-mm particles. Nevertheless, some discrepancies are evidenced in the values of the fitting parameters. In particular, we observe that larger particles lead to higher velocities and lower packing fractions at the orifice. Intriguingly, both magnitudes seem to compensate giving rise to very similar flow rates. In order to shed light on the origin of this behavior we have computed fields of a solid fraction, velocity, and a kinetic-stress like variable in the region above the orifice.
Highlights
The flow of granular matter in the discharge of silos or hoppers has been studied for many years [1,2] due to its application in industry
The most widely accepted expression to predict the mass flow rate W of granular matter in a silo was proposed by Beverloo et al [8] in 1961, W
Where C and k are fitting parameters, g is the gravity acceleration, ρB is the bulk density, N is the dimensionality of the system, D = 2R is the diameter of the outlet, and dp = 2rp is the beads’ diameter
Summary
The flow of granular matter in the discharge of silos or hoppers has been studied for many years [1,2] due to its application in industry. Despite the popularity of the expression of Beverloo et al [8], it involves some features of uncertain physical sense, such as the inclusion of the bulk density ρB instead of the flowing density or the reduced aperture size D − kdp, which accounts for a hypothetical forbidden area of the orifice through which the beads are not allowed to pass. This idea, popularly known as the empty annulus [15], has been the traditional way to include the dependence of the mass flow rate on the particle size
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
