Simulation of straw movement by discrete element modelling of straw-sweep-soil interaction

Abstract

Understanding residue and soil behaviour under the impact of tillage tools is critical for designing tools for conservation tillage. A soil-tool-residue interaction model was developed for a sweep and oat straw using the discrete element method. Soil, sweep, and straw were modelled using spherical particles, walls, and clumps respectively. A virtual field consisting of two layers including a soil layer and a top straw layer was constructed. Dynamic attributes including soil moving area, straw moving area, residue cover, kinetic energy, straw velocity, acceleration, displacement, and moving trajectory were monitored. Comparing the simulated values of soil and straw moving areas with those calculated from analytical models in literature, the calibrated model parameters of ball stiffness and clump stiffness were 8730 and 332 N m−1 respectively. The model had an overall relative error of 7.3% as comparing predicted straw displacements and residue cover with those measured in a soil bin test and extracted from previous experimental data in the literature. Increasing the travel speed of the sweep increased the residue cover reduction and straw displacements. The kinematic attributes clearly demonstrated three stages of the straw movement: forced, projectile, and overturning movements. The results demonstrated that it is feasible to obtain dynamic attributes of bulk materials and individual particles of a straw-sweep-soil interaction system using the discrete element model.