Application of the Type-C Constrained Interpolation Profile Method to Lightning Electromagnetic Field Analyses

概要

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The type-C constrained interpolation profile (CIP) method has been applied to analyzing lightning electromagnetic fields. The CIP method is one of the finite-difference methods. Differently from the finite-difference time-domain (FDTD) method, however, it considers not only electric- and magnetic-field values at each discretized points in a working space but also their spatial-derivative values there. Therefore, in principle, it can compute fields accurately even when a relatively coarse grid and a relatively large time increment are used. In section 2 of this paper, a numerical procedure for computing electromagnetic fields in a three-dimensional space using the CIP method is presented. In section 3, the type-C CIP method is applied to computing electric fields in a uniform grid, which are generated by a lightning return-stroke current wave propagating upward along a vertical straight channel located on flat perfectly conducting ground, and the CIP-computed waveforms are compared with the corresponding waveforms computed theoretically and using the FDTD method. In section 4, the method is applied to computing lightning electric fields in a nonuniform grid, and a similar comparison is made.