Internal flow-induced behaviour of flexible risers

It has been found in recent years that the pressure distribution and flow behaviour of fluid inside the bore of a flexible riser has a substantial effect on its static and dynamic behaviour. This paper is concerned with examining the contributions of internal flow to both the governing equations and the dynamic excitation forces applied to a flexible riser. A derivation from first principles of the full governing equations for a flexible riser in two dimensions is presented, together with equations for riser excitation due to slug flow through the riser bore. A frequency-domain numerical solution scheme is also described and its results are compared with model tests for both riser global behaviour due to external disturbances (such as surface vessel motions and waves) and due to internal flow.