SERCO

A method for computing periodic orbits for the Navier-Stokes

equations will be presented. The method uses a finite-element Galerkin

discretisation for the spatial part of the problem and a spectral

Galerkin method for the temporal part of the problem. The method will

be illustrated by calculations of the periodic flow behind a circular

cylinder in a channel. The problem has a simple reflectional symmetry

and it will be explained how this can be exploited to reduce the cost

of the computations.