This paper aims to test the feasibility of correcting the relative wave elevation (RWE) prediction from linear potential theory using simplified CFD simulation of the local hull model. Two-dimensional models with and without bow flare shape in the vertical plane are created to evaluate the nonlinear wave swell-up phenomenon at FPSO bow. By dipping the 2D hull model into calm water using sinusoidal velocity with different amplitudes, the performance of bow flare design on green water reduction is estimated and discussed. The data of RWE correction from 2D CFD study is applied to the numerical prediction based on linear potential theory. For discrepancies showed in comparison with lab test measurement, 3D CFD study on fixed FPSO hull in beam sea wave is further conducted to preliminarily examine the 3D effect of bow flare.
Floating platforms like floating production, storage and offloading unit (FPSO) may encounter green water impact when operating in severely high sea-states, the water wave may rise up and exceed the freeboard height, falling onto the deck. As a traditional method for deck wetness reduction at bow region, bow flare design has been widely applied on ships and ship-shape offshore floating platforms, with its effectiveness proven by some research studies as well as long-time track record of the industrial application. Bales (1979) observes from model test that flared bows and knuckles are effective in mitigating deck wetness in some situations. Experimental studies conducted by O'dea and Walden (1984) show that the increase in bow flare can effectively reduce deck wetness. In the experimental investigation conducted by Jones (1992), the increase in bow flare can cause increase in flare slam force and decrease in deck wetness force. Buchner (1998) studied the nonlinear relative wave motion at FPSO bow experimentally, and identify that the measured RWE is lower than calculated with linear diffraction theory, due to increase in bow flare angle and the onboard procedure of green water onto the deck. A third order polynomial relation between measurement and linear potential prediction is derived, and a complete empirical approached is presented in Buchner and Voogt (2000). Nielsen (2003) also conducted experimental and numerical studies on the effect of bow flare to wave run-up, showing that the amount of shipping water can be significantly reduced by bow flare. Benmansour et al. (2016) observe in their experiment that increase on bow overhang extension can result in significant reduction on the shipping water volume.
