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Silos are containers used by almost all fields of industry for storing granular materials and generally classified in two types: mass flow and funnel flow. One of the most important design parameter of these equipment is the discharge rate which depends on the flow mode. There are high numbers of analytical and empirical models used for determine this parameter, however none of them is suitable for both flow modes; moreover the accuracy of mass flow models is not acceptable. Recently a few numerical discharge models are made for certain geometries; but the applicability of these models in case of different flow modes was not examined. Aim of our work is the creation of an experimentally validated numerical discharge model based on others work and examination of this in term of different flow modes. We prove that our modified model is suitable for determine silos discharge rate independently from flow mode.

Purpose The effect of micromechanical parameters on the macromechanical behaviour of granular materials is analysed by using discrete element based model of the standard shear test. Design/methodology/approach Discrete element method based standard shear test simulations. Findings The approximate mathematical functions related to the effects of DEM micromechanical parameters density, Young-modulus, Poisson number, frictional angle, bond normal cohesion, bond tangential cohesion, rolling friction and particle shape on the macromechanical parameters of shear failure line (internal friction and cohesion) are determined by modelling large number of standard shear tests. Originality/value By knowing these effects of micromechanical parameters to the macromechanical behaviour of the simulated particle assembly, the calibration of discrete element models can be significantly accelerated.

Purpose -The analysis of the effect of tool vibrations on the measured and simulated draught forces of cultivator tools. This paper aims to discuss this issue. Design/methodology/approach -Soil bin measurements and discrete element method (DEM)-based simulations. Findings -The soil-tool interaction induced free vibrations of cultivator tools have significant impact on the measured draught force, and the simulations made by using vibrating tools give similar results. Research limitations/implications -Accurate calibration of discrete element model parameters can be done based on the reproduction of the whole Mohr-Coulomb failure line. Draught force ratiovelocity ratio values seem to be independent of tool geometry and soil conditions in case of velocity ratio higher than 2. Practical implications -DEM-based numerical simulations can be used for modeling the effect of tool vibration on the draught force values. During discrete element simulations of soil-tool interaction, the effect of tool vibration may not be neglected. Originality/value -The paper demonstrates that during the discrete element modelling of the soil-tool interaction, the tool vibration phenomenon should not be neglected.