The application of CPML in analysis of the characteristic of EMP propagation in crooked tunnel

Finite-Difference Time-Domain (FDTD) method has been applied to analyze the characteristic of EMP propagation in tunnel, which can be seen as a waveguide approximately, and is excited by propagation model such as TE10, TM11, etc. In order to improve the effectiveness of the absorbing boundary condition, a perfectly matched layer (PML) medium with complex frequency-shifted (CFS) constitutive parameters is introduced for this study. The absorbing boundary is implemented by using the convolution PML (CPML), and the absorbing efficiency of CPML is compared with traditional PML. Numerical results show that the CPML provides for a more efficient absorbing boundary than that of the traditional PML at absorbing evanescent modes, and consequently the computation domain and computation time can be greatly reduced.