FINITE-ELEMENT COMPUTATION OF DISPERSION PROPERTIES OF THIN-WALLED WAVE-GUIDES

A method is presented for the numerical computation of the wavenumbers and associated modes of the cross-section of thin-walled waveguides. The method is based on finite element techniques. A thin-shell type finite element of the cross-section is developed by using the virtual work formulation for one-dimensional propagation (the case of a waveguide). The set of equations of motion evaluated by finite element discretization is then transformed into a simple eigenvalue problem involving a general real matrix. Two examples are analyzed by the finite element method developed: the circular cylindrical shell (straight thin-walled pipe) and the thin-walled beam of I-shaped cross-section (the so-called I-profile). Results obtained by the finite element method, by Donnell's shell theory and by using simple Euler-Bernoulli beam theory are compared. © 1994 Academic Press Limited.