RANS computational fluid dynamics predictions of pitch and heave ship motions in head seas

This work extends the previous effort in unsteady Reynolds averaged Navier-Stokes (RANS) simulations developed by the ship hydrodynamics group of the University of Iowa Iowa Institute of Hydraulic Research 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, multiblock, high-performance parallel computing RAINS code. Numerical verification studies in space and time demonstrate convergence for nearly all variables. The modified Wigley hull form 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 nonlinear problem into the forward speed diffraction and pitch and heave radiation problems, in the manner of strip theory. Comparisons between the current viscous RAINS solutions and those from experiments, strip theory, and nonlinear potential flow simulations show the RANS method to predict damping and added mass coefficients with a high degree of accuracy.