基于FDTD的不同土壤类型及湿度对雷电电磁场传播影响的研究

RESEARCH ON INFLUENCE OF DIFFERENT SOIL TYPES AND MOISTURE ON LIGHTNING ELECTROMAGNETIC FIELD BASED ON FDTD

关键词:  雷电电磁场  FDTD  土壤类型  土壤湿度  土壤电导率

Key words:  lightning electromagnetic field  FDTD  soil type  soil moisture  soil conductivity

摘要:

为深入研究土壤类型和土壤湿度对雷电电磁场传播效应的影响，首次将工程勘察领域研究得出的土壤湿度和电导率计算关系应用到雷电电磁场模拟计算中。基于Heidler雷电通道基电流函数模型和MTLL回击模型，在Mur一阶边界条件下，利用2D-FDTD计算粘土、粉土和砂土这三种具有代表性土壤在不同土壤湿度和观测距离下的雷电电磁场。研究结果表明：相比于粉土和砂土，雷电电磁场沿粘土地表传播过程中产生的水平电场更容易受土壤湿度的影响，特别是土壤湿度较低时，即土壤湿度从5%到6%变化过程中，水平电场峰值的波动幅度达39.86%；当土壤类型为粘土时，水平电场[Er]、垂直电场[Ez]和磁场Hφ受土壤湿度影响等级为Ez>Hφ；随着闪电电磁辐射传播距离和土壤湿度的增大，场幅值减小，波形的波头上升沿时间变慢。研究结果为准确评估和量化不同土壤类型和土壤湿度对雷电电磁场传播的影响以及优化闪电站网定位提供了重要的科学依据。

Abstract:

To investigate the influence of soil type and soil moisture on the propagation effect of lightning electromagnetic field (LEMF), the present study applies the relationship between soil moisture and conductivity obtained in engineering surveys to the study of LEMF. Bases on the Heidler function, MTLL model and Mur Absorbing Boundary, the present study uses 2D-FDTD to calculate the LEMF of clay, silt and sand under different moisture conditions and observation distances. The main results are as follows: Compared with those of silt and sand, [Er] generated by the propagation of LEMF along clay surface is more susceptible to soil moisture. When soil moisture changes from 5% to 6%, the attenuation of the peak of [Er] is 39.86%. When the soil is clay, the influence of soil moisture on [Er] is the strongest, followed by [Ez] and [H?]. As the propagation distance of lightning electromagnetic radiation and soil moisture increase, the attenuation of electromagnetic field intensifies, and the rise time of field waveform also increases. The results provide an important scientific basis for accurate evaluation and quantification of the influence of soil type and soil moisture on the propagation of LEMF and the optimization of the positioning of lightning station network.