裸露地表土壤风蚀及其电场数值模拟

Wind erosion and numerical modelling on its electric field of bare soil over lands

土壤风蚀及电场机理研究是认识其灾害本质,进而实现有效防治的基础。采用颗粒流体动力学方法,建立裸露地表土壤风蚀的气-固耦合模型,并基于水的电离理论,建立了运动土壤颗粒碰撞带电模型。数值计算结果不仅从理论上再现了裸露地表土壤风蚀的发生、发展及达到动态稳定的过程,而且定量分析了土壤风蚀过程颗粒的带电特性及其产生的风蚀电场。在风-颗粒相互耦合作用下,裸露地表土壤颗粒的风蚀过程最终达到动态稳定,土壤风蚀量随高度呈指数规律递减,且贴近地表层风蚀量较大。土壤颗粒在运动中的碰撞使得颗粒发生带电现象,粒径较大颗粒带正电,粒径较小颗粒带负电;由带电土壤颗粒产生的风蚀电场强度随高度减小,且在风蚀过程中逐渐增强,在风蚀达到动态平衡时风蚀电场趋于稳定。本文综合考虑了风-土壤-电场的土壤风蚀过程,这将为建立更加符合实际、较为全面的土壤风蚀模型提供理论基础。

Wind erosion is the serious disaster problem for agriculture and environment,so it needs insight into its mechanical mechanism to prevent and control effectively soil and related disasters.In this paper,granular flow dynamics model in bare lands,which is coupled with wind and soil particles,is suggested to describe the evolution process of wind erosion.And based on the theory of water ionization,the soil particles charged model is establish to reveal the particles charged during the collision process.Each charged soil particle can be look as a point charge,so the calculation model is given to simulate the characteristics of soil erosion electric field until its reaching a dynamic equilibrium.The numerical simulation results show that with the action of wind force,the soil particles roll or jump,and then they impact other soil particles on bare lands.During the wind erosion process,the wind provides continuously energy for moving soil particles,and the moving soil particles also weaken the wind,with the coupling the wind erosion reaches a dynamic stability in about 7seconds.In the dynamic equilibrium the calculation result of soil erosion amount is mostly closed to the experimental results.And the quantity of wind erosion decreases exponentially with height,especially below 10 cm height the soil erosion amount exceeds 90% of the total,which indicates that wind erosion is the particle transport phenomena near lands.During two soil particles collision process,charge transform of H3O＋and OH-causes the collision particles charged,and the larger soil particles positively charged,the smaller soil particles negatively charged.In different particles size intervals the change of the total electricity fluctuates with time,but the overall trend of electric quantity increases rapidly in the initial stage,and then decreases slowly until reaching a dynamic stability.The charged soil particles produce electric field,the electric field intensity is weak at the beginning and then gradually increases until wind erosion reaches stability,and the electric field intensity decreases with height.The study results indicate that it will be an important trend to consider the electric field in wind erosion,which provides a theoretical basis to establish more practical and comprehensive soil erosion model.