Numerical simulations of FPSO with sloshing tanks in a random freak waves

This paper presents a potential-viscous coupled method to simulate a floating production storage and offloading (FPSO) with two liquefied natural gas (LNG) sloshing tanks in a random freak wave. The potential theory uses high-order-spectral (HOS) method. The random wave is generated by HOS for 2 000 s, and a freak wave is observed around 1 830 s. The FPSO LNG model was firstly verified in regular waves using HOS-computational fluid dynamics (CFD) coupled method and validated the HOS-CFD coupled method can solve the ship motion coupled with sloshing tanks accurately. The FPSO with LNG tanks are then simulated in the freak wave, showed the coupling effects when the freak wave passes. With the existence of the sloshing tanks, the amplitude of the roll motion decreases and the period of roll motion changed. Wave breaking phenomenon can be observed when the wave crest of the freak wave encounters with the ship.