Vortex-Induced Motions of Offshore Structures

Background

Floating Offshore structures, such as production semi-submersibles, TLPs and spars, can exhibit significant in-line and transverse motions under current conditions. Such motions are generally called Vortex- Induced Motions (VIM) and could have a strong impact on the fatigue life of mooring and riser systems.

The VIM phenomenon is characterised by complex interactions between the floater and the flow around the floater. At the moment model test programmes are the preferred method to predict the VIM behaviour of the vessel. However, this is only feasible when the final design of the floater is known. Thus, tools and benchmark data are needed to assess the anticipated VIM behaviour at an early design stage to be able to reduce the VIM response of the floater.

Objectives

The main objectives of the VIM Joint Industry Project are as follows:

• Increase insight into the physics/phenomenon behind VIM in order to improve concept design
• Develop an early stage VIM prediction/quantification method
• Provide design guidance or “Best Practice” for VIM model testing and VIM CFD studies
• Evaluation of differences between model tests and CFD on one hand and field observations on the other hand