Simulation of urea particle flow using DEM for dry fertilizer spreading optimization

Uniformity of dry fertilizer spread pattern relies on the accurate representation of bulk material behavior during handling, discharge, and impact. This study aims to develop a discrete element method (DEM) model for urea and assessed it through a calibration and multi-method validation framework pertinent to fertilizer spreader applications. Urea was first characterized experimentally for particle size and density, and the DEM particles were represented as single spheres with a mean diameter of 3.2 mm. A full-factorial design of experiment was then used to calibrate the model using two bulk responses: angle of repose and loose-fill bulk density. The calibrated parameter set consisted of a particle-particle static friction coefficient of 0.27 and a rolling friction coefficient of 0.11. With this set, the DEM model predicted angle of repose and bulk density with percent relative errors of 10.02% and 7.50%, respectively. The calibrated model was then validated using two independent experiments: hopper discharge through a 100 mm square orifice and bulk particle impact on a 25° inclined plate. For hopper discharge, the model predicted a steady-state mass flow rate of 4.40 kg s⁻¹ compared with the experimental value of 4.83 kg s⁻¹, giving a percent relative error of 8.85%. For the impact-plate test, the DEM model predicted an accumulated mass of 2.50 kg·s compared with an experimental mean of 2.26 kg·s, with a percent relative error of 10.56%. The projected particle–plate contact area showed the closest agreement, with a DEM prediction of 102,039 mm² compared with an experimental mean of 103,520 mm², corresponding to a percent relative error of −1.43%. Overall, the results show that calibration based on angle of repose and bulk density can produce a DEM model that predicts gravity-driven discharge and post-impact spreading behavior with reasonable accuracy. At the same time, the larger error in accumulated mass suggests that impact-related retention and collision behavior may require additional calibration parameters in future work.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

thesis

Discipline thesis:degree_discipline

Agricultural engineering

Grantor

Iowa State University - Thesis & Dissertation

Year dc:date.issued

2026

Author dc:creator

• Kosaraju , Satya , Venkatesh

Advisor dc:contributor.advisor

• Tekeste, Mehari, Z

• Agricultural and biosystems engineering

Language dc:language.iso

en_US

Repository record dc:identifier.uri

https://dr.lib.iastate.edu/handle/20.500.12876/106807

OAI identifier oai:identifier

oai:dr.lib.iastate.edu:20.500.12876/106807