稻谷颗粒模型离散元接触参数标定与试验

EDEM与FLUENT耦合模拟稻谷清选时,稻谷颗粒参数设置的准确性直接影响仿真结果的可信度。结合稻谷颗粒堆积角的实测试验与仿真试验,标定了稻谷颗粒模型间静摩擦系数、滚动摩擦系数2个主要接触参数。设计了堆积角形成装置,该装置采用坍塌法和注入法同时形成2种堆积角,可以减小非同时形成所引起的测量误差;创建了稻谷颗粒的离散元模型,结合堆积角的实测试验与仿真试验,建立了2个主要接触参数与2种堆积角之间的二元回归方程;以稻谷颗粒2种堆积角的实测结果作为目标值,对回归方程进行数值求解,得到颗粒模型间的静摩擦系数、滚动摩擦系数分别为0.433 6、0.161 5;设计了抛洒试验对标定后的参数进行验证,抛洒长度、宽度和近抛洒端堆积角等特征参数的实测结果与仿真结果的相对误差小于5.7%,这表明颗粒的模拟运动轨迹与实际运动轨迹基本一致,所创建的稻谷颗粒离散元模型及标定得到的接触参数可以为EDEM-FLUENT耦合仿真稻谷清选过程提供参考。

Calibration and Experiment of Contact Parameters of Rice Grain Based on Discrete Element Method

The credibility of simulation results was directly affected by the accuracy of rice grain parameter setting when EDEM coupling with FLUENT to simulate rice separation. In this paper, combined the measured and simulation test of rice grain response angle, two main contact parameters between rice grain models, static friction coefficient and rolling friction coefficient, were calibrated based on discrete elements. A response angle measuring device was designed to form two kinds of response angles using collapse and injection, which could reduce the measurement error caused by non-simultaneous formation, create a discrete element model of rice grain, combine the actual test and simulation test of the stacking angle, and establish the binary equation regression between two main contact parameters and two response angles. The measured results of the two kinds of response angles of rice grains were used as the correction index to solve the equations, and obtained the static friction coefficient and the rolling friction coefficient of the rice grain model were 0.433 6 and 0.161 5, respectively. The throwing test was designed to verify the calibrated parameters. The length and width of the throwing, and a response angle neared the spray point in experiment were compared with them in simulation, and the result showed that the relative error was less than 5.7%. These results indicated that the simulated motion trajectory of the particles was basically consistent with the actual trajectory. The discrete element model of the rice particles and the contact parameters obtained by the calibration can provide reference for the EDEM-FLUENT simulation of the rice cleaning process.