裸露地表近地层土壤风蚀运移过程的模拟研究

Numerical simulation of soil erosion transport process of bare lands in boundary layer

土壤风蚀是造成土壤肥力下降和沙尘天气的重要原因。通过建立大气边界层对流扩散运动方程、裸露地表起尘模式和土壤颗粒的扩散方程等,采用大涡模拟方法对表层土壤侵蚀的迁移特征进行了数值模拟研究。计算结果表明:小粒径运动土壤颗粒受流场的影响比大粒径沙尘明显;随着土壤颗粒组粒径的增大,土壤输移量也增大,且逐渐趋于底层输移,小粒径土壤颗粒的输移量很小,主要偏重于高处,中等粒度颗粒输移量随高度缓慢减小;在较高处,小粒径土壤颗粒数目所占的百分比却较大,随着高度的降低,中等粒径土壤颗粒数目所占的百分比逐渐增大,而贴近床面处,大粒径土壤颗粒数目百分比较大。

Soil erosion is an important cause leading to soil fertility decrease and sanddust weather. Based on establishment of atmospheric boundary layer convective diffusion motion equation,dust lifting mode of bare surface and diffusion equation of soil particles,this paper conducts numerical a simulation study on the transport characteristics of surface land erosion with Large Eddy Simulation method. The results show that,the flow field effect on smaller soil particles is more obvious than that on larger soil particles. With diameter increases,the soil particle transport quantity increases and concentrates on the lower layer,while the transport quantity of smaller diameter soil particles is very little and concentrates on higher layer. For middle diameter particles,the soil particle transport quantity decreases gradually with height increases. But in higher layer,the percentage of smaller particles is higher,the percentage of middle diameter particles gradually increases with height decrease,and close to the surface,the percentage of larger soil particles is higher.