Motion simulation of oat and vetch seeds in distributors based on DEM-CFD

Improving the uniformity of seed particle distribution is the key to the research of air blown collection and discharge seed metering devices. Analyzing the movement process of particles can help improve seed metering performance. In this study, the DEM-CFD (discrete element method and computational fluid dynamics) coupled simulation model was used to simulate the motion characteristics of oat seeds, vetch seeds, and mixed seeds in an air blown manifold distributor. From the perspectives of airflow field and seed motion, the effects of distributor cap shape and mixed seed supply ratio on the uniformity performance of oat seeds, vetch seeds, and their mixed seeds were analyzed. The coefficient of variation of seeding quantity in each row and the precision of discharging mixed seeds ratio were selected to evaluate the seed motion characteristics. The results showed that as the inlet velocity of the airflow increased, the seeds discharged from the distribution pipe decreased. When the inlet velocity of the airflow was 25 m/s, the coefficient of variation of seeding quantity in each row of seeding in the distribution pipe was the least and less than 5 %. The use of a convex distributor cap resulted in the best uniformity of the arrangement of vetch seeds, while the use of a conical distributor cap resulted in the best uniformity of oat seed arrangement. For the seeding of mixed seeds, the convex distributor better promoted the stable movement of the seeds, exhibited better seeding uniformity performance, and could effectively reduce the frequency of contact between the seeds and the distribution pipe wall, avoiding sudden changes in the velocity vector of the seeds. The convex distributor cap also exhibited superior seeding uniformity performance for different mixed seed supply ratios. This result will help to improve understanding of the distribution characteristics of mixed seeds and optimize the distributor structure of the air blown collection and discharge seed metering device.