Study on nonlinear heave and pitch motions of conventional and tumblehome hulls in head seas

Abstract

The broadside of the tumblehome hull is inclined inward, while that of the conventional hulls is inclined outward. As a result of the geometric shape, the tumblehome hull has distinct motion characteristics compared to the conventional hulls. In this study, the nonlinear heave and pitch motion responses of a tumblehome hull are investigated experimentally and numerically. A series of model experiments at various wave slopes is performed to validate the nonlinear motion responses in head sea conditions. As a numerical approach, a time-domain B-spline 3-D Rankine panel method (RPM) and computational fluid dynamics (CFD) are adopted. During the nonlinear motion computation, a weakly-nonlinear method is applied to the RPM to consider the geometric properties of the tumblehome hull above the waterline. The S175 containership is selected as the comparative model. It is a conventional-shaped hull, and the relevant experimental results are available. For the conventional hull, the magnitudes of the motion transfer functions of the heave and pitch motions decrease as the wave slope increased. For the tumblehome hull, an opposite trend is observed in both the experimental and numerical results. The magnitudes of the motion transfer functions increase as the wave slope increased. The increase and decrease in the nonlinear motion responses are discussed. ？ 2022 Elsevier Ltd