Abstract
A time-domain numerical method to predict in-line dynamics of flexible risers for upwelling deep ocean water has been developed. The analysis method is based on a swingby-swing technique with symmetrical vortices model. The symmetrical vortices model may accurately estimate instantaneous hydrodynamic forces for the Kc number lower than eight.
The effects of internal flow are considered by adding the momentum change of the internal flow, the frictional force on the inner wall of the pipe, the reduction of the internal pressure, and the reaction force of the intake flow.
To validate the present dynamic analysis method, motion measurements in steady current conditions and forced oscillation conditions in still water are performed. The results in steady current conditions show that the horizontal displacement of the pipe with internal flow is larger than that without internal flow due to the reaction force of the intake flow. The results in forced oscillation conditions demonstrate that the amplitude of the motion increases when the internal flow exists. The results in conditions with two different oscillation components showed that the present method have great potential for analyzing dynamic responses of CWP in irregularly load conditions.
