Browsing by Author "Madrid, Marcos A."
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Item A differential equation for the flow rate during silo discharge Beyond the Beverloo rule(EPJ Web of Conferences, 2017) Madrid, Marcos A.; Darias, José Ramón; Pugnaloni, LuisWe present a differential equation for the flow rate of granular materials during the discharge of a silo. This is based in the energy balance of the variable mass system in contrast with the traditional derivations based on heuristic postulates such as the free fall arch. We show that this new equation is consistent with the well known Beverloo rule, providing an independent estimate for the universal Beverloo prefactor. We also find an analytic expression for the pressure under discharging conditions.Item Determination of the angle of repose and coefficient of rolling friction for wood pellets(2022-02-08) Madrid, Marcos A.; Fuentes., José María; Ayuga, Francisco; Gallego Vazquez, EutiquioThe determination of the angle of repose for granular materials is indispensable for their handling and the design of containers and technological processing equipment. On the other hand, computational simulations have become an essential tool to understand the micro-behavior of the granular material and to relate it with the macro-behavior. The experimental determination of the angle of repose has a fundamental role when defining the required parameters to perform realistic simulations. However, there is a lack of a standard that allows the reproducibility of the experiments when using granular materials of equivalent spherical radius greater than 2 mm, such as corn, soybeans, wheat and PLA pellets, among others. In particular, a product of growing importance in the global strategy of decarbonization of the economy is biomass pellets, whose handling operations are one of the main components for the total cost of pellets supplied to the final user. In the present work, with the aim of determining the rolling friction coefficient, the variations in the angle of repose with the drop height for biomass pellets were studied both experimentally and with simulations, and an optimal procedure for its determination was found. Then, a calibration of the coefficient of rolling friction was performed through computational simulations using the discrete element method. The accuracy of the model under different configurations was checked.Item Differential equation for the flow rate of discharging silos based on energy balance(2020-05) Darias, José Ramón; Madrid, Marcos A.; Pugnaloni, LuisSince the early work of Hagen in 1852 and Beverloo et al. in 1961, the flow rate of granular material discharging through a circular orifice from a silo has been described by means of dimensional analysis and experimental fits, and explained through the “free fall arch” model. Here, in contrast with the traditional approach, we derive a differential equation based on the energy balance of the system. This equation is consistent with the well known Beverloo rule thanks to a compensation of energy terms. Moreover, this new equation can be used to explore new conditions for silo discharges. In particular, we show how the effect of friction on the flow rate can be predicted. The theory is validated using discrete element method simulations.Item Effect of bevelled silo outlet in the flow rate during discharge(2023-07-29) Gago, Paula; Madrid, Marcos A.; Boettcher, Stefan; Blumenfeld, Raphael; King, PeterWe investigate the effect of a bevelled (or slanted) outlet on the discharge rate of mono-sized spheres from a quasi-two-dimensional silo, using the discrete element method. In contrast to hopper discharges, where the bevelling is across the entire base of the container, we study a bevelled opening that is significantly smaller than the silo width and in which the slanting is limited to half a sphere diameter at the boundary of the outlet. We show that the bevelling increases the flow rate comparably to the inclination in hopper walls. Using Beverloo’s model, we relate this increase in rate to what we define as the ‘effective opening’ of the silo and analyse the velocity profiles associated with the discharges. We show that different openings, having effectively the same discharge rates, give rise to distinctly different internal dynamics in the silo. These results have the potential to aid industrial processes by fine-tuning and improving control of silo discharges, with a minimal impact on silo design, thus significantly reducing production and handling costs.Item On the use of magnetic particles to enhance the flow of vibrated grains through narrow apertures(2021-06-28) Carlevaro, Manuel; Kuperman, Marcelo N.; Bouzat, Sebastián; Pugnaloni, Luis; Madrid, Marcos A.The ow of grains through narrow apertures posses an extraordinary challenge: clogging. Strategies to alleviate the effect of clogging, such as the use of external vibration, are always part of the design of machinery for the handling of bulk materials. It has recently been shown that one way to reduce clogging is to use a small fraction of small particles as an additive. Besides, several works reported that self-repelling magnetic grains can ow through narrow apertures with little clogging, which suggest these are excellent candidates as \lubricating" additives for other granular materials. In this work, we study the effect of adding self-repelling magnetic particles to a sample of grains in two-dimensions. We find that, in contrast with intuition, the added magnetic grains not necessarily aid the ow of the original species.Item Self-assembly of self-propelled magnetic grains(2021) Madrid, Marcos A.; Irastorza, Ramiro; Meyra, Ariel G.; Carlevaro, ManuelIn this work, we study bidisperse mixtures of self-propelled magnetic particles of di erent shapes via discrete element method simulations. We show how these particles self-assemble into clusters and how these clusters depend on the ratio of the mixture, the magnetic interaction, and the shape of the grains. It is found that the mix ratio of the system controls the cluster size. Besides, the intensity of the magnetic dipoles and the shape of the grains in the mixture rule the average number of neighbors in contact and the shape of the clusters. By varying the intensity of the interactions, globular, linear and branched clusters were obtained.