Numerical simulation of seed motion characteristics of distribution head for rapeseed and wheat

The distribution head and its impact on seed distribution uniformity were the core parts of an air-assisted centralized seed-metering device. Numerical simulation of seed motion in the distribution head was carried out with a coupling approach using the Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM). The seed migration trajectory and distribution behavior were tracked. The variation coefficient of seeds distribution (CV), airflow velocity field and seed motion characteristics for different structures of streamlined tube and lid, airflow velocities, and seed feed rates were calculated and analyzed. The structural parameters mainly included the streamlined angle (ψ), radius of baseline (R), outlet diameter of streamlined angle (d1), lid angle (α), and installation location (a). Simulation results showed that, with the streamlined angle increased from 10° to 50°, the variation coefficient of seeds distribution decreased initially and then increased for an inlet diameter of 20 mm and an airflow velocity of 20 m/s. When R was less than 20 mm, the air pressure loss and seed resultant force increased obviously. The seeds distribution was more uniform when ψ = 60°, R = 40 mm, and α = 120°. The seed resultant force and resultant velocity increased with the increasing of airflow velocity. The distribution uniformity and power consumption improved at the airflow velocity of 20-24 m/s for rapeseed and 24-28 m/s for wheat of different seed feed rates, respectively. This research using the CFD-DEM coupling approach would be helpful in improving distribution uniformity, explaining the seed distribution mechanism, and optimizing the structure of distribution head.