Experimental Investigation of Roll and Heave Excitation and Damping in Beam Wave Fields

This paper will discuss a systematic series of model tests performed at NSWCCD on a conventional combatant hull form at varying Froude numbers, beam wave steepness, and beam wave frequencies near the natural roll frequency of the model. The model was free in roll and heave while constrained in the remaining four degrees of freedom. The model was fully appended, yielding lateral force on the bilge keels, lift, drag and torque on the rudders and all six force and moment components on the propellers. Stereo particle-image velocimetry (SPIV) measurement was used to study the three-dimensional unsteady flow patterns around the bilge keels at the model LCG. Model motion results were analyzed with respect to the excitation waves to yield normalized heave and roll amplitudes and phase angles. Force and moment results were analyzed to yield individual appendage viscous drag and added mass coefficients which were in turn used to extend and refine previous theoretical models to include the effects of beam seas. SPIV results were compiled and analyzed to provide a verification and validation dataset for CFD computations.© 2007 ASME