CFD simulation of directional short-crested waves on a jack-up structure

Greenwater on jack-up structures occur when storm waves significantly exceed the air gap and slam into the jack-up hull and its topside equipment. In the present study, a Navier-Stokes code was employed in conjunction with the interface-capturing level-set method for the prediction of wave impact on a jack-up structure under hurricane wave conditions. An overset grid system is employed to facilitate the simulation of complex flow around a generic jack-up structure with three supporting legs and simplified topside equipment. Time-domain simulation of greenwater and wave impact loads were performed for random 3D short-crested waves based on the directional wave spectra of Hurricane Katrina. The simulation results successfully captured the evolution of the wave crest as it propagates through the jack-up structure while exerting impact loads on the topside equipment in its path. A detailed evaluation of six different extreme wave events indicates that the greenwater impact loads are highly localized due to the short crestedness of the random 3D waves. Nevertheless, the maximum wave impact load exerting on the entire jack-up structure is strongly correlated with the crest height of the incident waves. The simulation results provide useful guidance for estimating the peak impact loads produced by directional short-crested waves. Copyright 2012 by the International Society of Offshore and Polar Engineers (ISOPE).

CFD simulation of directional short-crested waves on a jack-up structure Conference Paper