Due to the combination of vortex-induced vibration and coupled platform motion, fatigue damage is a potential issue for catenary flexible risers. This paper reports the experimental results of vortex-induced vibration of a catenary flexible riser hinged underneath a two-degree-of-freedom vortex-induced moving platform. The in-plane and out-of-plane responses of the riser are monitored by high-speed cameras while the cross-flow and in-line motions are recorded by laser displacement sensors. The strong and weak couplings between the platform motion and riser vibration are identified. Moreover, the strong coupling is further classified into two types: riser vibration dominated and platform motion dominated ones. The in-plane and out-of-plane responses of the riser also present the interaction which varies along the span. Affected by the in-line motion of the top platform, the interaction between in-plane and out-of-plane responses is weakened. Because of the spatial frequency competition, the number of required samples for machine learning varies along the riser. The maximum required number occurs in the middle part, followed by the top part as a result of the platform motion.

platform motion  /  vortex induced vibration  /  coupling response  /  spatial-temporal evolution