A ray tracing method for evaluating field distribution in tunnels

This paper is concerned with field estimation by the ray tracing method (RTM) in two-dimensional (2D) tunnels with arbitrary cross section whose dimension is relatively large compared with the wavelength. The tunnel wall is approximated as a combination of plates. We investigate the accuracy of RTM in comparison with a rigorous solution or finite volume time domain (FVTD) solutions. It is shown that RTM provides accurate numerical results for the field distribution in a rectangular tunnel when its dimension is larger than 20 lambda. For the tunnel with a curved wall, such as a circular or semicircular tunnel, it is shown that the radius of curvature should be greater than 20 lambda to obtain accurate numerical results based on RTM. (C) 2000 Scripta Technica, Electron Comm Jpn.