Validating FLUENT for the flow of granular materials in aerial spreaders

A simulation model for predicting the velocity vectors of fertilizer particles emanating from an aerial spreader was developed using a commercial software package FLUENT version 4.32. Simulation results for urea particles emanating from a curved duct were compared with laboratory results. The particle size (geometric mean particle diameters) ranged from 1.30 mm to 2.82 mm and the air velocity at the inlet of a curved duct was varied from 42 m/s to 62 m/s. FLUENT always predicted lower particle velocities than were measured in the laboratory. The difference was attributed to uneven shape of the particles and modeling errors. FLUENT predicted particle velocities could be corrected with a correction factor specific to a fertilizer. For materials having particles of different shapes the value for correction factor would be different. The particle velocity was found to be linearly related to the air velocity. The effect of the particle size on its velocity was quadratic, with smaller particles attaining higher velocities at the exit from the duct than did the larger particles.