COEXISTENCE OF PERIODIC ROLL MOTION AND CHAOTIC ONE IN A FORCED FLOODED SHIP

This letter describes the coexistence of periodic and chaotic roll mot ion of a flooded ship in waves. We found experimentally, both with a f looded ferry model and with a simplified box-shaped model, that the tw o types of roll motion can coexist under the same wave condition. A tr ajectory reconstructed in a delay-coordinate state space from the time series data of the measured roll angle looks like a low-dimensional s trange attractor. Moreover, a mathematical model for the simplified bo x-shaped ship shows the coexistence of a periodic solution and a chaot ic one with a positive maximum Liapunov exponent.