An unsteady RANS CFD method is applied to a surface-piercing body in steady forward motion in calm water or with Stokes' wave external flow or in regular head waves, but restrained from body motions. In terms of ship hydrodynamics problems, this can be referred to as the first step in merging the separate problems of resistance and propulsion and seakeeping. The approach includes the development of the computational method and verification and validation studies for a surface-piercing body for both steady and unsteady flows.; Steady flow results are presented for the model problems of a surface-piercing flat plate and Wigley hull in calm water and a surface-piercing flat plate with Stokes' wave external flow. Validation is carried out using a variety of benchmarks. The effects of the free-surface and Stokes' wave external flow are investigated. The effects of approximations for the dynamic free-surface condition are also investigated.; Unsteady flow results are presented for the model problems of a surface-piercing flat plate and Wigley hull in regular head waves. Validation using experimental data and comparisons with inviscid methods are done. The effects of regular head wave are investigated. The effects of Froude number, wave length, and wave amplitude are summarized.; The present unsteady RANS method performs well for steady flow in terms of predicting the hydrodynamic forces, boundary layer and wake, the effects of the free-surface and Stokes' wave. It also shows promising capability for simulation of unsteady forces and moments and unsteady boundary layer and wake and wave field response for a surface-piercing body in regular head waves, which suggests applicability for additional complexities such as practical ship geometry, ship motions and maneuvering.
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