Abstract: The basic research on electromagnetic effect of agricultural materials has good application value in microwave-assisted application and device design.  Based on properties of cereal grains, this paper presented a novel method for modeling and numerical analysis, which combined discrete element method, finite element method and average energy method. The feasibility, validity and accuracy of the model were verified by numerical simulation and experimental measurements. The real and simulated results showed that the repose angle error of rice particle materials was 0.45%, and the maximum error between the numerical results of effective dielectric properties obtained by the simulation model and the experimental measurements were less than 5.0% in the calculation conditions of dielectric constant (2.0~10.0), dielectric loss factor (0.1~0.9), microwave frequency（2.0~11.7 GHz）, moisture content (2.0%～19.7%) and volume fraction (18.2%～88.0%) of the cereal grain materials. This study provided basis for microwave processing and nondestructive sensing of cereal grains, and also provided  reference  for the simulation of dielectric properties of other kinds of granular agricultural products.

Key words: cereal grains, free-fall accumulation, effective dielectric properties, numerical simulation

摘要： 农业物料的电磁效应基础研究在农产品微波辅助应用及器件设计中具有较好的应用价值。针对堆积型谷物颗粒物料提出了集离散元法、有限元法和平均能量法为一体的等效介电特性模拟仿真模型和数值计算方法，采用数值计算和实验测量方法验证了模型的有效性和准确性。结果表明：真实稻谷和模拟稻谷的堆积角误差为0.45%。在谷物颗粒的介电常数(2.0~10.0)、介电损耗因子(0.1~0.9)、微波频率（2.0~11.7 GHz）、湿基含水率(2.0%～19.7%)和体积分数(18.2%～88.0%)计算条件下，采用模拟模型得到的谷物物料等效介电特性的数值结果与实验测量值的最大误差小于5.0%。上述结果可为谷物类农产品的微波加工和非破坏性检测提供依据，为其他不同种类农业散粒体的介电特性模拟研究提供参考。

关键词: 谷物颗粒物料, 落料堆积, 等效介电特性, 数值模拟