Wind-Jack Interaction of jack-up legs with the seabed


For jack-up wind turbine installation vessels the loads on the legs and the jacking system during touch-down and lift-off are considered the most critical aspects in the operational performance of the vessels. The aim of the JIP, which is in its second year, is to understand and predict this interaction between jack-up legs and the seabed in order to better quantify the operational limits.


As a first deliverable to the participants, MARIN’s existing time domain hydrodynamic tool aNySIM has been extended with a simplified soil response model, which ena- bles the seabed impact loads on the vessel during dynamic vessel motions to be calculated. In the coming year an advanced soil response model will be developed and verified by soil mechanic, as well as hydrodynamic model tests. Finally, an easy-to-use practical tool will be developed. Wind-Jack will run until Q3 2014. Contact: Jorrit-Jan Serraris, j.w.serraris@marin.nl


VIM Vortex-Induced Motions of offshore structures


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.


VIM phenomenon is characterised by complex inter- actions 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. Therefore, tools and benchmark data are needed to assess the antici- pated VIM behaviour at an early design stage to be able to reduce the VIM response of the floater.


The primary objective of the VIM JIP is to increase the physical insight into the VIM phenomenon so the design of a floater can be improved during the design phase.


The JIP will focus on model testing methodologies and CFD studies. Specific consideration will be given to: - The effect of geometric design parameters and appendages on VIM


- Characteristics of the flow field during VIM - Differences in (environmental) conditions between model tests, CFD results and field observations with respect to VIM behaviour


- Influence of scale effects on VIM


To start shortly, the three-year JIP will be conducted in close cooperation with oil companies, offshore design companies, operators and offshore contractors. Contact: Arjen Koop, a.koop@marin.nl


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