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Ice accretion on marine vessels and offshore structures is a severe hazard in the Polar Regions. There is increasing activities related to oil and gas exploration, tourism, cargo transport, and fishing in the Arctic. Ice accretion can cause vessel instability, excess load on marine structures and represents a safety risk for outdoor working environment and operations. Freezing sea spray is the main contributor to marine icing. For safe operations in cold climate, it is essential to have verified models for prediction of icing. Sea spray icing forecast models have improved. Empirical and theoretical models providing icing rates based may be useful as guidelines. For predicting the distribution of icing on a surface at the design stage, Computational Fluid Dynamics has to be applied along with a freezing module. State-of-the-art models for numerical simulation of sea spray icing are still not fully capable of modelling complex ship-sea-wind interactions with spray generation and impact of shipped water. Existing models include good understanding of spray flow effects and freezing. Further development should focus on developing models for dynamic ship-sea-wind interactions, in particular including spray generation, effects of shipped water and distribution of icing on the vessel surface. More experimental and full-scale data is needed for development and verification of new and improved models. Models that estimate ice distribution may improve the winterization design process and reduce effort required for de-icing. Improved methods for de-icing and anti-icing will reduce the impact of sea spray icing and increase safety for marine operations in cold waters.

While designing the power requirements of a ship, the most important factor to be considered is the ship resistance, or the sea drag forces acting on the ship. It is important to have an estimate of the ship resistance while designing the propulsion system since the power required to overcome the sea drag forces contribute to 'losses' in the propulsion system. There are three main methods to calculate ship resistance: Statistical methods like the Holtrop-Mennen (HM) method, numerical analysis or CFD (Computational Fluid Dynamics) simulations, and model testing, i.e. scaled model tests in towing tanks. At the start of the design stage, when only basic ship parameters are available, only statistical models like the HM method can be used. Numerical analysis/ CFD simulations and model tests can be performed only when the complete 3D design of the ship is completed. The present paper aims at predicting the calm water ship resistance using CFD simulations, using the Flow-3D software package. A case study of a roll-on/roll-off passenger (RoPax) ferry was investigated. Ship resistance was calculated at various ship speeds. Since the mesh affects the results in any CFD simulation, multiple meshes were used to check the mesh sensitivity. The results from the simulations were compared with the estimate from the HM method. The results from simulations agreed well with the HM method for low ship speeds. The difference in the results was considerably high compared to the HM method for higher ship speeds. The capability of Flow-3D to perform ship resistance analysis was demonstrated.

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