The paper investigates the effect of different computational meshing techniques and essential calculation parameters on the convergence and accuracy of the unsteady viscous free surface flow calculations around ship hulls.

 As the overall computational time including the pre-processing period still remains as a major issue despite the significant developments in computational power of high performance systems in recent years, the determination of an optimal convergence strategy along with a practical meshing technique provides valuable benefits for such computations. The paper compares different computational cases in terms of the effect of the time step size and number of outer iterations per time step, on the critical aspects, such as convergence speed, accuracy and overall solution time. An attempt was made to provide an optimum convergence strategy by dynamically varying the time step sizes and number of outer iterations per time step. Different meshing techniques, which included unstructured grids with both isotropic and anisotropic mesh elements along with conventional structured grids, were also adopted to provide further information about the effectiveness in the pre-processing time and effect of the grid structure on the solution.

Unsteady Reynolds-Averaged-Navier-Stokes equations along with the Volume of Fluid (VOF) method were employed for the computational analyses. The well-known Wigley hull form was selected as the reference geometry for the fundamental computations. The determined optimum strategy was then applied to the Series 60 and DTMB 5512 hull forms in order to validate its effectiveness and accuracy. The evaluations were performed in comparison with the experimental results available in the open literature.