嵇艳鞠　任桂莹　关珊珊　黎东升

摘   要：共形网格技术可减小传统有限差分方法带来的阶梯状网格近似误差. 将共形网格技术运用到无源麦克斯韦方程组的推导中，采用线性加权平均方法，求得棱边电场的等效电导率，更新了传统时域有限差分方法的电场迭代方程;研究了具有解析式目标体的共形参数确定方法，利用投影思想得到共形网格位置坐标，进而求得共形参数. 通过与有限元方法计算得出的电磁响应进行比较，验证了本文方法的正确性;共形网格技术在保证计算效率的条件下，与阶梯状网格近似方法相比提高了曲面三维异常体的计算精度;需要共形处理的电场越多，共形网格技术的效果越明显，精度提高越多. 该方法为开展地下复杂异常体的航空电磁三维正反演奠定了基础.

关键词：航空电磁法;共形网格技术;三维曲面异常体;时域有限差分方法;线性加权平均

中圖分类号：P631                            文献标志码：A

Abstract：Conform mesh technique is usually adopted to eliminate the step approximation error caused by the traditional Finite Difference Time Domain（FDTD） method. In this paper，the conformal mesh technique was introduced into the derivation of passive Maxwell's equations. To update the electric field iterative equation of the traditional Finite Difference Time Domain method，a linear weighted average method was used to obtain the equivalent conductivity of the edge electric field. Using the projection theory，the position coordinates of the conformal mesh were calculated，and then the conformal parameters of the target body were obtained. The electromagnetic responses of this method are consistent with that of the finite element method. Compared with the step approximation method，the conformal mesh technique shows a higher computational accuracy when calculating a three-dimensional anomaly with a curved surface. The more the electric field is required to be processed conformally，the more obvious the effect of the conformal mesh technique is，the accuracy is also improved greatly as a result. This method sets the fundamental to calculate complex underground anomalies of airborne electromagnetic.

Key words：airborne electromagnetic surveys;conformal mesh technique;three-dimensional curved anomaly surface;Finite Difference Time Domain（FDTD） method;linear weighted average

航空瞬变电磁方法（Airborne Transient Electromagnetic Method，ATEM）采用飞行器搭载电磁系统对大地的二次场进行快速测量，通过分析二次场获得地下电阻率分布，从而了解地质体的构造. 相比于地面瞬变电磁法，航空瞬变电磁具有探测速度快，范围广，可在短时间内获得较多信息等特点，更适用于森林、沼泽、割裂地形、山区等地形复杂区域的勘探. 航空瞬变电磁法在国内外发展较为迅速，在浅覆盖区寻找金属矿、隐蔽洞体等典型目标体探测方面起到了重要的……