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accelerations?for a ship advancing at constant speed, with arbitrary heading in both regular waves and irregular seas. For detailed predictions in the time domain, programs such as FREDYN can be used for predicting ship motions. Such codes include modeling for a variety of indi -vidual forces including: Froude-Krylov, radiation, diraction, rudder and append -ages, propeller, maneuvering, and viscous. The simulations usually assume linear superposition of the individual forces, and a hierarchy of models, often based on experimental data or simple analytic tech -niques, has evolved for their prediction. Despite these limitations, there has been signicant success in predicting the large amplitude motions of particular hull forms. However, when applied to a new hull form or in situations where Froude-Krylov forces may not dominate, the predictions become suspect until they are compared with experimental data, which limits the extent to which the codes can be used in design cycles. Maneuvering and seakeeping are rela -tively new areas for CFD calculations. CFD oers the possibility of computing more of the physics directly and can contribute to the inviscid models where no experimen -tal data exists. Roll motion is an obvious area where viscous eects are important, and empirical models start to break down as new hulls come under consideration. Maneuvering force prediction is another area in which CFD can contribute and can capture the hull forces and interac -tion between the hull and appendages. To evaluate the applicability of RANS codes to simulate maneuvering directly, the SIMMAN Workshop on Verification and Validation of Ship Manoeuvring Simulation Methods was held in Copenhagen, Denmark in 2008. e purpose of the work -shop was to benchmark the capabilities of different ship maneuvering simulation methods through comparisons with test results for tanker, container ship, and sur -face combatant hull forms. The results from workshops such as this suggest that current CFD/RANS capa -bility provides accurate data for design studies involving calm water maneuvers. The number of runs needed to quantify ship behavior is within the realm of CFD and today?s computer resources. Efforts are needed, however, to make component en-USJuly 2012 en-US en-USwww.sname.org/sname/mt Figure 4: Wind ow over the deck of a semi-submersible heavy-lift ship in a cross breeze.