SEAKEEPING QUALITY OF SMALL VOLUME HULL FORM ABOVE WATER PLANE (1ST REPORT)

Non-linearity of hydrodynamic forces acting on a small volume hull form above the water plane is studied experimentally. Nonlinearity of the vertical radiation force and moment cannot be clarified because the rated capacity of a forced oscillation device is insufficient for a high frequency oscillation of large amplitude. Both wave exciting heave force and pitch moment show a typical tendency of saturation against wave amplitudes. Applicability of the linear superposition on radiation forces and wave exciting force is studied by conducting a forced oscillation test in regular head waves. It is recognised from results of the experiment that the linear superposition cannot be applicable when the phase lag between forced heave motion and incident wave motion becomes greater than 90 degrees. See also abstract no. 92020375.