The present paper summarizes the results for numerical simulation of a fixed FPSO-shaped body in uni-directional phase-focused wave groups, which is prepared as a short report for the CCP-WSI Blind Test Workshop on Focused Wave Impact on a Fixed FPSO at the 28th International Ocean and Polar Engineering Conference (ISOPE 2018). The numerical simulations were carried out using the open source toolbox OpenFOAM. An overset mesh method was applied, where two layers of mesh were generated, namely the background mesh and the overlapping body-fitted mesh. The incident focused wave groups were first validated against the experimental data at several positions. With the propagation of the waves, it was found that the waves generated by the numerical model were slightly dissipated due to numerical diffusion. Therefore, smaller wave crest was predicted from the numerical model. Then the simulations were conducted for the same wave conditions with the FPSO structure in place. The surface elevation and the pressure at several locations based on the validation criteria are reported.
The floating production storage and offloading (FPSO) vessels are used in offshore oil and gas industry. They are usually operated in deep water conditions where harsh marine environment may be encountered. Therefore, it is of importance to examine the survivability of the FPSO in such extreme sea state.
Previously there have been several publications on extreme wave loads on fixed structures. Zang et al. (2006) presents the effects of second order wave diffraction in wave run-up around the bow of a vessel (FPSO) for regular waves and focused wave groups. Chen et al (2014) analysed the high order components of the wave load on a monopole. Paulsen et al. (2014) investigated numerically the forcing by steep regular water waves on a vertical circular cylinder at finite depth. Special attention was paid on the second load cycle. It was found that the second load cycle was caused by the strong nonlinear motion of the free surface, which drives a return flow at the back of the cylinder following the passage of the wave crest.
