NONLINEAR REACTION FORCES ON OSCILLATING BODIES BY A TIME-DOMAIN PANEL METHOD

An outline of a time-domain boundary integral equation method (with se cond-order accuracy) for bodies floating on a fluid is given. It inclu des the full nonlinear dynamics of a potential flow with a free surfac e. To validate the method, a partially immersed body is forced to osci llate at a small amplitude for each of three modes. Relevant component s of the reaction force on the body are integrated separately, thereby enhancing the accuracy of the hydrodynamic coefficients determined fr om this force signal. Linear frequency-domain results in a range of fr equencies agree well with the present ones for the square, excellently for the circle. Nonlinear fluid-body interaction is simulated for a v ertically oscillating square with amplitudes up to 80% of its draft. T he force dependence on the motion amplitude provides a confirmation of second-order theory. Furthermore, the triple-frequency force componen t shows a pronounced cubic dependence on the amplitude.