Key parameters determination based on seed movement process simulation for rice strip aerial seeding via UAV

• CFD-DEM coupled framework decodes strip aerial seeding dynamics. • Through-type seeding tube completely blocks rotor airflow disturbance. • Field-validated 57.4 mm rice seed strip width and 0.77 strip index. To clarify the influence of the key structures and working parameters of the rice strip aerial seeding (SAS) based on unmanned aerial vehicle (UAV) on the strip effect, this study systematically analyzed the entire movement process of seeds by constructing the Computational Fluid Dynamics and Discrete Element method (CFD-DEM) coupled simulation model, and the mud-box aerial seeding test was conducted to validate the reliability of the simulation. The results showed that the flight velocity, flight height, and length of the seeding tube respectively affect the strip effect of rice seeds by changing the distribution space of the downwash airflow, the unconstrained movement trajectory of the seeds after leaving the seeding tube, and the lateral movement velocity of the seed. The strip effect of the rice seeds improved with the increase of flight velocity and seeding tube length, and weakened with the increase of flight height. These were some uncontrollable factors, such as variations in the roll angle of UAV attitude and the assembly accuracy of connection component. It is difficult to fully limit the influence of these factors by adjusting the flight height and velocity. However, extending the seeding tube to 1500 mm to keep its end in a ground-contacting for seeding can optimize the average width of strips and the strip index to 33.2 mm and 0.87. Therefore, A new, stable, and reliable SAS architecture, featuring a fully through-type seeding tube, was used in field test. The average strip width was 57.4 mm with strip index of 0.77 in the field test, which met the requirements of the direct strip-seeding technology for rice. These research findings can provide technical references for the further design of a productized rice SAS device based on UAV.