Numerical Ocean Wave-Basin (NOW): A Numerical Solution for FSRU Mooring Design Analysis

Abstract

A numerical solution is proposed for the design analysis of the mooring system of an FSRU in shallow water. Previously. such analysis relied on second-order diffraction theory with viscous damping empirically calibrated from physical model tests. However, both experimental and theoretical methods had to introduce uncertainties in the predicted mooring load because of their physical and theoretical limitations. A complicated procedure had to be introduced to derive design loads considering the uncertainties and limitations. The proposed numerical solutions are developed to minimize those uncertainties by introducing the state-of-the-art numerical tools to accurately model the flow field near the FSRU and the surrounding wave field. A CFD-based numerical wave basin, MrNWB, and a potential-based higher-order Boussinesq wave model, HAWASSI, are coupled together to simulate the near- and outer-field free-surface flows around the FSRU hull. This paper describes the framework of the proposed numerical method, followed by preliminary verifications of the accuracy and effectiveness of the proposed solution. A benchmark model test of an FSRU moored in a shallow sloping beach is used to validate the generation of the low-frequency wave and the slow-drift motion of FSRU from CFD simulation. The numerical results show significant improvement in the low-frequency FSRU responses compared to the conventional theoretical methods.

Phase-Resolved Wave Simulation over Isolated Seamount

“…The study in [33,34] also illustrated the performance of simulations against measurements for three application areas: wave tank experiments, incoming waves in a harbor with a deep access channel, and extreme waves such as in the Draupner wave, a measured freak wave at the Draupner platform in the North Sea on 1 January 1995 over deep water. Furthermore, HAWASSI was identified as one of the potential wave kinematics solvers to generate nonlinear irregular waves for the "JIP on Reproducible Computational Fluid Dynamics (CFD) Modeling Practices for Offshore Applications" [35,36]. It has been used for engineering applications to develop reliable numerical wave modeling practices.…”