基于改进颗粒簇单元的卸粮宏细观机理模拟

Simulation of Macroscopic and Microscopic Mechanism During Grain Discharge Based on Improved Particle Clump Unit

传统PFC模拟卸粮均采用单一ball单元模型,不能准确反映小麦等不规则粮食卸粮过程中的宏细观力学机理。本研究建立了由clump单元和ball单元组成的改进颗粒簇单元,以室内卸粮物理模型试验为基础进行数值计算,并和传统模型的模拟结果进行对比分析。研究表明:(1)在宏观仓壁压力方面,改进颗粒簇单元模拟所得结果与传统ball模型相比,误差降低了17.9%;(2)在颗粒细观结构方面,改进模型的颗粒堆积孔隙率下降了3.07%,而配位数增大了27%,模拟误差降低了3.12%;(3)改进模型接触力数量增加了96.3%,接触力链分布更均匀密集,能清晰反映瞬时拱此消彼长的动态变化。本研究建立的改进颗粒簇单元提高了模拟的准确度,能客观反映卸粮过程的侧压力、颗粒结构、细观力学参数动态变化。

In the silo grain discharge with PFC simulation,the traditional model uses a ball unit model,which could not reflect macro and meso mechanical mechanism accurately during the process of grain discharge such as wheat and rice and other particles with irregular shapes.Based on this,a particle clump unit model consisting of clump units and small ball units was established in this paper.The model used clump units to simulate irregular grain particles and adds small ball units to simulate dust particles.Based on the physical model test of indoor grain discharge, the numerical simulation experiment was carried out with improved particle clump units,and the simulation results were compared with the traditional model.The research showed that:( 1) In terms of macroscopic wall pressure, and the error of the result gained from the improved particle cluster element simulation reduced by 17.9% compared with the traditional ball model;( 2) In the micro - structure of particles,the particle packing porosity of the improved model decreases by 3.07% and the coordination number increases by 27% compared with traditional ball units model,which decrease the simulation error by 3.12%;( 3) Particle morphology affects the micro - mechanical behavior of particles,the simulation results show that the number of contact forces in the improved model increases by 96.3%compared with the traditional ball model,and the distribution of contact force chains is more uniform and dense,and the distribution of contact force chain is more uniform and dense,which can clearly reflect the dynamic change of instantaneous arch length.The improved clump units established in this paper further improved the accuracy of simulation objectively reflected the dynamic changes of lateral pressure,particle structure,and meso - mechanical parameters during grain discharge process.