Authors

Abstract

To optimize the simulation process of seed pellet coating, this study employs the discrete element method to precisely model and analyze particles, using ice grass seeds as the research subject. The key procedures include constructing a three-dimensional pseudo-ellipsoidal geometric model based on the hyperquadratic surface pseudo-ellipsoid equation and defining it as the mesh division range for the DEM model. The Hertz–Mindlin with JKR contact model was selected to describe inter-particle interactions. A standardized filling sphere addition method for the ellipsoidal model was proposed. Using a central maximum filling sphere with a diameter of 1.2 mm as the baseline, composite models consisting of 17, 9, and 5 spheres were constructed with sphere diameters equal to 0.25, 0.5, and 0.75 times the baseline diameter, respectively. The filling sphere size corresponds to the largest inscribed sphere tangent to the ellipsoid. Through static angle of repose simulation tests, the optimal parameter combination was determined to achieve a target value of 30.54°, resulting in a shear modulus of 1.9 × 10⁷ Pa, a collision restitution coefficient of 0.5 for ice grass seeds, and a filling sphere diameter multiplier of 0.35. Under these conditions, the simulated static angle of repose averaged 30.67°, with a relative error of only 0.43%. Further dynamic calibration tests were conducted using a rotating drum. With a filling rate of 40%, a rotational speed of 58 r/min, and a simulation duration of 10 s, the simulated dynamic angle of repose was 38.12°, exhibiting a relative error of 0.88% compared with the physical test value of 38.46°. These results provide a valuable reference for discrete element modeling and parameter calibration of ellipsoidal particles.

Abstract in Chinese

为优化草种丸粒化包衣仿真过程，本研究以冰草种子为对象，应用离散元法对颗粒进行精确地建模和分析。主要内容为基于超二次曲面超椭球方程构建类椭球三维几何模型，并将其设为离散元模型的网格划分范围，选择“Hertz–Mindlin with JKR”接触模型，提出类椭球模型标准化填充球添加方式：以中心1.2mm最大填充球为基准，按其直径的0.25、0.5、0.75倍分别构建17球、9球、5球模型，其填充球大小为椭圆相切的最大内切球。通过休止角仿真试验，以30.54°为目标值优化得到最佳参数组合剪切模量1.9×10^7Pa、冰草种子间碰撞恢复系数0.5、填充球直径倍数0.35，此时仿真静态休止角均值30.67°，相对误差仅0.43%；旋转鼓动态标定试验中，旋转鼓的填充率为40%、转速为58r/min、仿真时长为10s，仿真动态休止角38.12°，与物理试验值38.46°的相对误差为0.88%。研究结果可为类椭球颗粒离散元建模提供参考。