Model research programme for hydrodynamic response of an air lifted gravity-based structure in limited water depth

Summary

The research programme provided a preliminary guide for designers concerned with the required still water Under Keel Clearance (UKC) and still water Water Plug Height (WPH) of air-lifted Gravity Based Structures (GBS) with skirts, for floatout through very shallow (<12m) water in a mild seaway.

The modelling provided an excellent understanding of the effects of trapped air volumes on wave-induced dynamic motions, for varying values of UKC.

The effects of UKC reduction were evaluated in the range of 1.4 – 10.4m for the prototype.

At the upper end of this range substantial attenuation in both Heave and Pitch occurs with reduction of UKC, while different trends were found in the lower end of the range.

Keywords: gravity based structure, air lifted, under keel clearance, modelling tank