ABSTRACT

Computational Fluid Dynamics (CFD) simulation methodologies for FPSO bow impact calculation were consolidated in a Joint Development Project (JDP). To validate the proposed simulation method, a series of model test performed for the bow wave impact problem by focusing wave was considered. First, wave generation performance was checked by applying the present CFD simulation method. In this case, the measured stroke signals of the wave maker in the model test were directly used as input of the inlet velocity boundary. Then, the numerical simulations results for wave impact forces were validated by comparing with the model test data. It is confirmed that FPSO bow impact prediction using the consolidated CFD simulation guideline is fairly good in overall physical process and wave impact forces.

INTRODUCTION

Offshore structures are vulnerable to harsh environmental conditions during operation, which can result in critical wave impact loads during their lives. Depending on the impact direction, the wave impact can be divided into vertical and horizontal wave impacts. The vertical wave impact includes the bottom slamming of a ship-type offshore structure and the wave-in-deck impact of semi-submersible platform. On the other hand, the horizontal wave impact includes the column impact of the semi-submersible platform and bow flare impact of FPSO, where the large horizontal wave impact is generally caused by the breaking waves. It is known that the wave impact events can cause fatal damage on the offshore structures as well as the safety of operators. Thus, the accurate estimation of wave impact force is significant for the survivability of the offshore platform under the extreme environmental conditions.

In recent years, direct CFD simulation method is considered as a complimentary tool to estimate wave impact loads on offshore structure. Bredmose and Jacobsen (2010) analyzed the wave impact forces on a fixed monopile based on open source CFD solver (OpenFOAM). This study showed that peak wave loads on the fixed monopile can be changed depending on the impact location. Mo et al. (2013) presented large eddy simulation (LES) results about flow pattern and interaction between a breaking wave and a slender cylinder. Kamath et al. (2016) validated the CFD simulation results for wave impact forces by comparing existing model test results with breaking location effect. Peng (2014) also performed numerical simulations by using the VOF method to estimate the impact force on a circular cylinder. He suggested a new formula for the estimation of the slamming coefficient. Hong et al. (2018) presented a comparative study in which various CFD codes, such as OpenFOAM, STAR-CCM+, MPS, etc, give different results in wave impact problem.

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