Numerical study on the effect of sloshing on ship parametric roll

In this study, numerical simulations of the parametric roll of a ship coupled with liquid sloshing were performed. A model-scale ONR Tumblehome was used for the simulation, and the ship was equipped with a partially filled liquid tank. An in-house unsteady Reynolds-averaged Navier-Stokes solver was applied to the numerical simulation of the coupling effect between the sloshing and parametric roll of the ship in regular head waves. First, a validation study of the computational fluid dynamics (CFD) solver was conducted. Comparisons between the CFD and experimental results showed good agreement. Systematic grid and time-step convergence studies were performed to estimate the numerical uncertainty. The effect of liquid sloshing on the parametric roll of a ship was then investigated numerically with different liquid levels and different ship forward speeds. The results demonstrated that water sloshing could significantly decrease the natural roll frequency of the ship model, which led to a lower speed range where the parametric roll occurred compared with the model without sloshing. The phase difference between the total moment and sloshing-induced moment was close to 180, resulting in a reduction of the parametric roll amplitude. Sloshing had slight effects on the amplitudes of the heave and pitch motions.