Analysis of transmission characteristics of curved tunnel with arbitrary cross section using hybrid mode matching/finite elements approach

The transmission characteristics of curved tunnel with arbitrary cross section is analyzed with a combined method which involves staircase approximation, mode matching (MM)/finite element method. The hybrid approach described combines the computational efficiency of the modal analysis with the versatility and flexibility of FEM and can be used to accurately model curved tunnel with arbitrary cross section, where modal expansions cannot be derived analytically. The procedure is based on the edge element expansion of the transverse field components for the direct calculation of the coupling integrals involved in the MM formulation. Numerical results are presented to show the validity and the accuracy of the method.