Analyzing the Near and Far Field Using Finite Difference and Finite Element Method

In this paper, the railgun is assumed to be an antenna and simulated with the finite element method (FEM) and the finite difference time domain (FDTD) method. For FEM analysis, the caliber of the railgun is 10 × 10 mm, rail thickness is 10 mm, and rail length is 400 mm. At first, the H-field on the cross section of the rails is computed. Next, power radiation and the maximum value of the E-field in the near and far field are obtained as a function of frequency. Polar radiation patterns versus frequency (1 kHz-1 MHz) in the near and far-field regions are calculated as a function of the angle. For FDTD, we assume that the railgun operates in the far-field region, and radiation patterns are computed in this region. The caliber of the railgun is 15 × 19 mm, rail thickness is 10 mm, and length is 1000 mm. Directivity has been computed versus frequency (100 Hz-1 MHz) in the far-field region. The H-field is calculated versus frequency and the energy is computed as a function of time. For both methods, the railgun included copper rails and an aluminum projectile.