A recursive approach for the finite element computation of waveguides
  The finite element computation of structures such as waveguides can lead to heavy computations when the length of the structure is large compared to the wavelength. Such waveguides can in fact be seen as one-dimensional periodic structures. In this paper a simple recursive method is presented to compute the global dynamic stiffness matrix of finite periodic structures. This allows to get frequency response functions with a small amount of computations. Examples are presented to show that the computing time is of order $\log_2 N$ where $N$ is the number of periods of the waveguide. 
Denis Duhamel (UR Navier)