| 麻山药种植田沙壤土流动性离散元模型颗粒放尺效应 |
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| 引用本文： | 郝建军,龙思放,李建昌,马志凯,赵晓顺,赵建国,李浩.麻山药种植田沙壤土流动性离散元模型颗粒放尺效应[J].农业工程学报,2020,36(21):56-64. |
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| 作者姓名： | 郝建军 龙思放 李建昌 马志凯 赵晓顺 赵建国 李浩 |
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| 作者单位： | 河北农业大学机电工程学院,保定 071000;河北农业大学机电工程学院,保定 071000;河北农业大学机电工程学院,保定 071000;河北农业大学机电工程学院,保定 071000;河北农业大学机电工程学院,保定 071000;河北农业大学机电工程学院,保定 071000;河北农业大学机电工程学院,保定 071000 |
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| 基金项目： | 河北省农机新机具新技术研发项目（2020） |
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| 摘 要： | 为简化麻山药-沙壤土复合体离散元模型，提高离散单元法在农业领域中的计算效率，以沙壤土为研究对象，在EDEM离散元软件中构建非球形颗粒，进行双目标参数标定试验，采用放大颗粒粒径方法，利用转鼓、坍塌与FT4流变仿真试验，从颗粒群动态堆积角、流动质量、流动速率以及能量等方面探究了颗粒放尺效应对颗粒群物理特性的影响。试验结果表明：干燥处理后的2 mm粒径沙壤土基质静态堆积角和动态堆积角平均值分别为32.16°和35.02°；与独立标定试验相比，双目标标定试验获得的仿真参数更具准确性与唯一性；在动态堆积角试验中，真实沙壤土颗粒在转鼓中所形成的动态堆积角随粒径和旋转速度的增大而减小，而在仿真试验中，转鼓转速相同情况下，非球形颗粒群在增大粒径的情况下所产生的动态休止角差异较小；坍塌试验中，不同粒径颗粒群在流动过程中的流动质量与平均流速变化趋势基本一致，但误差随粒径增大而增大；颗粒质量相同时，将粒径分别放大2倍及4倍，颗粒数量同比减少87.24%、98.92%，仿真时间明显缩短，计算效率显著提高；FT4流变试验表明，当放尺因子S为2时，阻力FV及其力矩T随时间变化的拟合曲线值约为原尺时的2倍，而当放尺因子S为4时，与原尺相比，拟合曲线斜率差异显著，相关性明显降低。研究结果可为构建沙壤土离散元放尺模型提供理论依据，同时也可为农业工程离散元放尺仿真计算提供一定参考。
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| 关 键 词： | 土壤 模型 颗粒放尺 沙壤土流动特性 标定试验 |
| 收稿时间： | 2020/8/7 0:00:00 |
| 修稿时间： | 2020/9/25 0:00:00 |
Effect of granular ruler in discrete element model of sandy loam fluidity in Ma yam planting field |
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| Hao Jianjun,Long Sifang,Li Jianchang,Ma Zhikai,Zhao Xiaoshun,Zhao Jianguo,Li Hao.Effect of granular ruler in discrete element model of sandy loam fluidity in Ma yam planting field[J].Transactions of the Chinese Society of Agricultural Engineering,2020,36(21):56-64. |
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| Authors: | Hao Jianjun Long Sifang Li Jianchang Ma Zhikai Zhao Xiaoshun Zhao Jianguo Li Hao |
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| Institution: | School of Mechanical and Electrical Engineering, Hebei Agricultural University, Baoding 071000, China |
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| Abstract: | This study aims to significantly improve the computational efficiency of discrete element method (DEM) in the agricultural field, particularly in the simplified model for harvesting the yam-sandy loam soil complex. Taking the sandy loam soil as the research object, the dual-target parameter calibration experiments were used to construct non-spherical particles in the discrete element software, together with enlarging the size of a single particle. The dynamic accumulation angle, flow quality, and flow rate were determined in the drum and collapse tests, and thereby to explore the influence of particle ruler effect on the flow characteristics in the particle group. The maximum scale factor of particles in the model was set as S=4, and the rotating speed of drum was set as4rpm, 40rpm, and 80rpm, respectively. The dynamic angles of repose in the particle group were measured in the actual and simulation test. Subsequently, a collapse test was carried out to monitor the discharge outlet flow during the collapse of particle groups'' indifferent sizes. The test results show that the average static accumulation angle of 2mm sandy loam matrix after drying treatment was 32.16°, and the average dynamic accumulation angle was 35.02°. The simulation parameters obtained from the dual-target calibration test were more accurate than that from the independent calibration test. The dynamic accumulation angle that formed by the real sandy loam particles in the drum decreased with the increase of particle size and rotation speed, while, the non-spherical particle group only changed the particle size in the simulation test. There was a relatively small difference in the dynamic angle of repose that produced in the case of diameter. In the collapse test, the changing trend of flow quality representing by the particle groups of different diameters in the flow process was basically the same as that of average flow velocity. The error was also increasing with the continuous increase of diameter. The amount of particles in the same calculation domain decreased by 87.24% (S=2) and 98.92% (S=4), respectively, indicating that the simulation time significantly reduced. Especially, when S=2, the calculation efficiency was significantly improved, compared with that of the non-stretched particles. The FT4 rheological test showed that when the scaling factor S was 2, the fitting curve of resistance FV and its torque T with the time changes was about twice that of the unfolding factor. When the scaling factor S was 4, the slopes of two fitted curves were totally different, indicating that the correlation was significantly reduced, compared with the original ruler. The findings can provide a sound theoretical basis on the construction of discrete element scaling model for the sandy loam soil, and the simulation calculation in agricultural engineering. |
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| Keywords: | soils models particle scale sandy loam flow characteristics calibration test |
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