The objective of this research was to enhance the stability and consistency of seed distribution during carrot planting.The impact of the seed guide tube’s structure on seeding quality was examined,leading to the des...The objective of this research was to enhance the stability and consistency of seed distribution during carrot planting.The impact of the seed guide tube’s structure on seeding quality was examined,leading to the design of a cycloidal seed guide system augmented by positive pressure airflow.By conducting kinematic modeling of the collision position of the seeds within the seed guiding system,as well as considering the seed guiding process and the seed drop position,the significant parameters influencing the final velocity of the seeds were determined.Employing a coupled Discrete Element Method-Computational Fluid Dynamics(DEM-CFD)simulation,the effects of different structural and operating parameters of the seed guide tube on the seed trajectory and airflow field were analyzed.A three-factor five-level orthogonal test was then utilized to examine the influence of each factor on each index,with the optimal conditions identified as an inlet airflow velocity of 0.077 m/s,a 45°tilt angle for the airflow branch tube,and a seed initial velocity of 0.1 m/s.Under these parameters,the qualification index was recorded as 94.1%,with a coefficient of variation of 3.2%.Bench testing conducted under the same conditions showed a decrease of 0.07%in the qualification index,and an increase of 1.875%in the coefficient of variation,with errors relative to the simulation results within acceptable bounds.These findings enhance the stability and reliability of the seed guiding system during carrot sowing operations,aligning with the demands of precision sowing.展开更多
边坡的宏观力学特性是由组成土体颗粒的细观参数及其运动决定的,基于连续介质模型的有限元方法虽然能够在宏观层面上基本等效地得到边坡土体的应力变形特性,但难以反映边坡体在微细观尺度上的变形失稳机理,存在明显的局限性。将离散元方...边坡的宏观力学特性是由组成土体颗粒的细观参数及其运动决定的,基于连续介质模型的有限元方法虽然能够在宏观层面上基本等效地得到边坡土体的应力变形特性,但难以反映边坡体在微细观尺度上的变形失稳机理,存在明显的局限性。将离散元方法(discrete element method,DEM)与计算流体动力学方法(computational fluid dynamic,CFD)进行耦合,建立了煤系土边坡3维DEM-CFD流固耦合细观作用计算模型,对降雨作用下煤系土边坡失稳破坏的细观机理进行分析。结果表明,采用DEM-CFD流固耦合方法模拟的煤系土边坡破坏形式主要是雨水冲刷,边坡滑动面预测为近似的直线段,这与室外模型试验边坡雨水冲刷的范围非常接近,验证了该数值方法的适应性。边坡土体颗粒的力链、配位数以及孔隙率等细观参数,在降雨过程中都会随之发生变化,如坡顶颗粒的孔隙率由初始状态的0.35变化至失稳状态的0.80,这些细观参数的变化与边坡土体的宏观力学表现直接关联。文中通过对颗粒细观参数变化分析,从细观角度解释了雨水作用下煤系土边坡的破坏演变规律。研究成果为该区域煤系土边坡的防护设计与施工提供理论依据,并从微细观角度更好地分析离散介质岩土工程的宏观力学规律提供了一种思路。展开更多
基金the National Natural Science Foundation of China(Grant No.52275258)Taishan Scholar Youth Expert Project(Grant No.tsqn202306243)Natural Science Foundation of Shandong Province(Grant No.ZR202111230084).
文摘The objective of this research was to enhance the stability and consistency of seed distribution during carrot planting.The impact of the seed guide tube’s structure on seeding quality was examined,leading to the design of a cycloidal seed guide system augmented by positive pressure airflow.By conducting kinematic modeling of the collision position of the seeds within the seed guiding system,as well as considering the seed guiding process and the seed drop position,the significant parameters influencing the final velocity of the seeds were determined.Employing a coupled Discrete Element Method-Computational Fluid Dynamics(DEM-CFD)simulation,the effects of different structural and operating parameters of the seed guide tube on the seed trajectory and airflow field were analyzed.A three-factor five-level orthogonal test was then utilized to examine the influence of each factor on each index,with the optimal conditions identified as an inlet airflow velocity of 0.077 m/s,a 45°tilt angle for the airflow branch tube,and a seed initial velocity of 0.1 m/s.Under these parameters,the qualification index was recorded as 94.1%,with a coefficient of variation of 3.2%.Bench testing conducted under the same conditions showed a decrease of 0.07%in the qualification index,and an increase of 1.875%in the coefficient of variation,with errors relative to the simulation results within acceptable bounds.These findings enhance the stability and reliability of the seed guiding system during carrot sowing operations,aligning with the demands of precision sowing.
文摘边坡的宏观力学特性是由组成土体颗粒的细观参数及其运动决定的,基于连续介质模型的有限元方法虽然能够在宏观层面上基本等效地得到边坡土体的应力变形特性,但难以反映边坡体在微细观尺度上的变形失稳机理,存在明显的局限性。将离散元方法(discrete element method,DEM)与计算流体动力学方法(computational fluid dynamic,CFD)进行耦合,建立了煤系土边坡3维DEM-CFD流固耦合细观作用计算模型,对降雨作用下煤系土边坡失稳破坏的细观机理进行分析。结果表明,采用DEM-CFD流固耦合方法模拟的煤系土边坡破坏形式主要是雨水冲刷,边坡滑动面预测为近似的直线段,这与室外模型试验边坡雨水冲刷的范围非常接近,验证了该数值方法的适应性。边坡土体颗粒的力链、配位数以及孔隙率等细观参数,在降雨过程中都会随之发生变化,如坡顶颗粒的孔隙率由初始状态的0.35变化至失稳状态的0.80,这些细观参数的变化与边坡土体的宏观力学表现直接关联。文中通过对颗粒细观参数变化分析,从细观角度解释了雨水作用下煤系土边坡的破坏演变规律。研究成果为该区域煤系土边坡的防护设计与施工提供理论依据,并从微细观角度更好地分析离散介质岩土工程的宏观力学规律提供了一种思路。
