INVESTIGATION OF MOTIONS OF CATAMARANS IN REGULAR WAVES .1.

In this paper an analytical technique based on the two-dimensional Gre en function method associated with a cross-flow approach for taking vi scous effects into account to estimate the motion response of catamara ns in the frequency domain is presented. In order to validate this met hod, the numerical results are compared with experimental values obtai ned for two different catamarans (ASR5061 [Wahab, R., Pritchett, C. an d Ruth, L.C. 1971. On the behaviour of the ASR catamaran in waves. Mar ine Technology, 8, 334-360] and Marintek [Faltinsen, O., Hoff, J.R., K valsvold, J. and Zhao, R. 1992. Global loads on high speed catamarans. 5th Int. Symp. on Practical Design of Ships and Mobile Units, Univers ity of Newcastle-upon-Tyne, 1.360-1.373]). In the second part of the p aper the tests carried out with a third catamaran configuration at the Hydrodynamics Laboratory of the University of Glasgow are presented t o evaluate the non-linear effects. These test results cover different speeds and wave heights at a wide range of wave frequencies. The paper concludes that the two-dimensional method correlates very well with m easurements of small amplitude motions. For large amplitude motion tes ts, the non-linear effects become significant when the model speed and wave amplitudes increase. The peak values of heave and pitch motions measured around the resonance frequency are smaller than those obtaine d from the linear theory.