Beam sea tests of two different ship models in large amplitude regular waves

The purpose of the paper is the study of the extreme ship motions through properly designed experiments aimed at both fundamental physical understanding and at collecting high-quality data for CFD codes validation. Two different ship models have been tested in regular beam waves to obtain repeatable data for time histories of measured motions, forces and moments. The tested models are geosyms of the DTMB model 5415 (INSEAN model 2385) and of the ONR Tumblehome (INSEAN model 2498), which are preliminary designs of surface combatants ca. 1980 and present time. The same scale has been adopted for both models (? = 46.6). Models have been both equipped with bilge keels. The adopted test conditions are free heave and roll, whereas the other degrees of freedom are constrained. Forces and moments have been acquired for the restrained motions. Two series of five repeated tests have been carried out, with medium and large wave amplitudes at the resonant frequency for both models. The precision limit (PI) for all variables has been evaluated.