Parameters calibration of discrete element simulation for fresh lotus seeds

Objective  To determine the parameters of discrete element simulation model in the mechanized processing of fresh lotus seeds, and provide data references for the mechanized processing simulation test of fresh lotus seeds.

Method  The calibration of discrete element simulation parameters of fresh lotus seeds was carried out by EDEM simulation software. The accumulation angle and repose angle of the actual fresh lotus seeds were measured by seed drop test with ‘Space lotus 36’ from Honghu, Hubei. Based on the Hertz-Mindlin (no slip) contact model, a simulation test of fresh lotus seed drop was conducted, and the error between the measured and simulated values of fresh lotus seed accumulation angle and repose angle was used as the test index to determine the contact parameters with significant effects on accumulation angle and repose angle through the Plackett-Burman test. The steepest climb test was conducted to determine the optimal contact parameter combinations in discrete element model for fresh lotus seeds. The actual seed drop verification test was carried out using the hopper with seed drop rate as the test index. The seed drop rates in actual and simulated seed drop verification tests were compared to verify the reliability of the optimal parameter combination.

Result  The effects of static friction coefficient between lotus seeds and rolling friction coefficient between lotus seeds on the accumulation angle were highly significant (P<0.01); The effects of rolling friction coefficient between lotus seeds on the repose angle were highly significant (P<0.01), and the effects of static friction coefficient between lotus seeds and static friction coefficient between lotus seeds and plexiglass on the repose angle were significant (P<0.05). The optimal combination of contact parameters was 0.4 for static friction coefficient between lotus seeds, 0.02 for rolling friction coefficient between lotus seeds, and 0.4 for static friction coefficient between lotus seeds and plexiglass. The results of the drop verification test showed that the maximum relative error of fresh lotus seed drop rate between the actual test and the simulation test was not exceeding 3.65%.

Conclusion  The contact parameters of the calibrated discrete element simulation model for fresh lotus seeds are accurate and reliable, and the findings can provide data references for the structural design optimization of lotus seed processing machinery.