Parametric rolling of a post-Panamax C11 class containership in regular and irregular waves is numerically investigated using body nonlinear time domain methods based on strip theory. The Froude-Krylov and the hydrostatic forces are calculated for the exact wetted surface area under the undisturbed incident wave profile. Two kinds of formulations are used for calculation of the radiation forces. The first one employs a linear radiation force in which the frequency dependent hydrodynamic coefficients are calculated for mean position of the sections at mean water level. The second formulation calculates the hydrodynamic coefficients for the exact submerged depth of ship sections under the undisturbed incident wave profile, and hence called as body nonlinear radiation force. The numerical results from the aforementioned formulations are compared with each other, and also with experimental results obtained from a wave tank in both regular and irregular waves. For all the cases in regular waves, the vulnerability to parametric rolling is clearly identified by the numerical models, even though a few discrepancies are observed in the estimation of the severity (maximum roll angle) of the problem. In this paper, the effects of the linear and body nonlinear radiation forces on the numerical calculation of parametric rolling of a container ship and the ability of the numerical methods to identify parametric rolling are investigated.

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