Induced Forces and Moments of a Tumblehome Hullform (Model 5613) Undergoing Forced Roll in Waves

: Predictions of large amplitude roll motions and capsize events have proven to be difficult and include large uncertainty. A factor that contributes to the difficulty in predictions is a lack of knowledge of resultant forces and moments for large roll angles. The equations currently used by numerical models to predict forces and moments due to roll motion are based on experimental data performed within a small range of roll amplitudes. For this reason, a data set of forces and moments is needed to verify that the model predictions are accurate in the U per ranges. If the predictions are inaccurate for the larger roll angles, a need may exist to develop new modes to predict the forces and moments for these larger roll amplitudes. In 2006, NSWCCD performed an experiment on Model 5613 to obtain the model scale constrained seakeeping results during large amplitude motions in waves, in contrast to the calm water experiments of 2005. Similar to the 2005 experiment, the effects of model speed, roll amplitude roll frequency, wave height and wave len on the forces and moments were investigated in an effort to develop a database of surge, sway, and heave forces, and roll, itch and yaw moments as a result of flare amplitude forced roll motions in waves. This report will describe the experimental setup and results of the 2006 experiment.