稳定流场条件下土壤颗粒跃移运动的力学特性

    Mechanical properties of saltating soil particles insteady-state wind field

    • 摘要: 针对土壤风蚀所导致的土地沙化,其关键问题是微观机理研究中运动颗粒的受力,该文通过建立气流-土壤颗粒耦合作用的稳态两相流模型,对土壤颗粒跃移运动受到的不同作用力进行了数值计算和理论分析,计算结果表明:拖曳力与重力之比大约在2~20之间,而Magnus力、Saffman力和电场力与重力之比仅在0~0.5之间。同一流场以同一速度起跳的土壤颗粒,重力和拖曳力起主要作用,Magnus力和静电力的影响较大,Saffman力影响最小,几乎可忽略。从土壤颗粒的跃移运动轨迹比较发现,该模型计算结果与试验观测结果趋势一致,但不同力作用下的差别不同,其中在重力、拖曳力和Magnus力作用下的土壤颗粒运动与试验观测误差最小,充分说明了该模型的合理性。此研究对农田种植垄间距、留茬高度、翻耕土壤粒度等保护性耕作措施提供依据。

       

      Abstract: Acted force on saltating soil particles is a key problem to study micro-mechanism in wind erosion disaster. In this paper, steady-state two phase flow model is suggested with the coupling interaction between air and particles, and the different force acted on saltating soil particles is theoretically calculated and analyzed. The numerical results show that ratio of the drag force to gravitation is between 2 and 20, but the ratio of Magnus force, Saffman force and electrostatic force to gravitation are only between 0 and 0.5. In the same wind field, and with the same lifting-off velocity, from the ratio of the different force to gravitation and the effect of the different force for saltating soil particles trajectories, it can be seen that the drag force and gravitation play dominant roles in soil particles movement, the effect of Magnus and electrostatic force are smaller, and Saffman force is the smallest and can be neglected. The soil particle motion trajectories show that the simulation results of this model is agreement to the experimental results. Acted by different force, the difference of soil particles trajectories is obvious, but acted by gravity, drag force and Magnus force, soil particles trajectories has minimum error, which fully shows that the model is reasonable. The study can provide a theoretical basis for farmland protection measures.

       

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