Towards a one parameter equation for a silo discharging model with inclined outlets

Abstract

Experiments on the discharge of a silo with an inclined outlet are performed for three types of seeds. The angle of inclination is varied to cover the complete range from 0° to 90°. The theoretical description of the flow rate behavior as a function of the aperture angle is achieved taking into account the two types of regimes present in the problem: funnel and mass flow. The former is assumed to be dominated by arch formation- destruction and, consequently, a free falling down of the particles from the arch dome is able to predict the experimental behavior through the addition of just one parameter closely related to the geometry of the arch. The second regime is described through a radial velocity picture for the flow streams close to the silo aperture and a numerical integration allows calculating the expected flow with good results. Finally, with the hypothesis that radial velocity can always be used as a good approximation for flow streams, an equation valid for all the range of angles is derived with the inclusion of just one parameter related to the drag force exerted by the flow on the particles. The challenge of one parameter equation for describing the mass flow rate in a wedged hopper is achieved and discussed.