RANS CFD Prediction of Pitch and Heave Ship Motions in Head Seas

G. Weymouth, R. V. Wilson, and F. Stern

DThis work extends the previous effort in unsteady RANS simulations developed by the ship hydrodynamics group of the University of Iowa IIHR to the capability to predict pitch and heave motions of ships with forward speed in regular head seas. The simulations are performed with CFDSHIP-IOWA, which is a general-purpose, multi-block, high-performance parallel computing RANS code. Numerical verification studies in space and time demonstrate convergence for nearly all variables. The modified Wigley hullform experimental data presented in Journee (1992) are compared with simulation results over a range of Froude numbers, wavelengths, and wave amplitudes and found to give accurate results, with uncertainties less than 2%. Viscous ship motions characteristics are investigated by decomposing the full non-linear problem into the forward speed diffraction and pitch and heave radiation problems, in the manner of strip theory. Comparisons between the current viscous RANS solutions and those from experiments, strip theory, and non-linear potential flow simulations show the RANS method to predict damping and added mass coefficients with a high degree of accuracy.