A scenario in which waves interact with two side-by-side floating bodies placed in close proximity holds significance in context to offloading of liquefied natural gas as well as floatover installation operations. The scenario becomes particularly challenging in beam-sea conditions and when the bodies have different draft and/or length. In the present paper we validate our in-house solver IITM-RANS3D to simulate the coupled response of twin floating barges, having different draft, in beam sea conditions. Two different configurations have been simulated with monochromatic incident waves depending on whether the shallow or deep draft body is placed on the weather-side. The results are benchmarked against in-house experimental data in terms of the response, wave amplification within the gap as well as surge force acting on the bodies. Broadly speaking, the simulations agree well with the experiments but necessitate further investigations into the over-prediction of the roll response.
Liquefied Natural Gas (LNG) offloading operations involve a LNG carrier (LNGC) closely approach and subsequently moor side-by-side to an offshore Floating LNG (FLNG) production platform. The LNGC is a tank ship whilst the FLNG is a ship-shaped or barge-shaped floating platform permanently moored above the natural gas field. These floating bodies are vastly different to one another in terms of size and draft. Further, to minimize the risk of collision, the mooring system must ensure that a minimum gap is maintained between the two vessels during the entire offloading operation. The result is a system of closely-spaced twin floating bodies restricted in sway but free to heave and roll which is susceptible to excitation in beam-sea conditions. In order to ensure a safe design of such a system, its dynamical response to an incident beam-sea needs to be understood. Since the bodies have different draft, the impact of placing either body at the weather-side on the hydrodynamic loads and resulting motion response needs to be studied in detail. Owing to the close side-by-side placement, the hydrodynamics within the gap and how that changes with relative placement also needs to be understood.