4. Surging of Large Amplitude and Surf-riding of Ships in Following Seas

概要

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The surf-riding of a ship is examined by means of the free-running model tests, as well as the numerical simulations and phase plane analyses of the nonlinear equation of surging motion. It is clarified that the surf-riding occurs when the ship speed including the oscillatory surging component, after the decay of the transitional motion, reaches the phase velocity of the wave. The speed range of the ship is divided into the three parts concerning the occurrence of the surf-riding. Below the first critical speed the ship never makes the surf-riding but makes always the periodic surging motion. Over the second critical speed, the ship inevitably falls into the surf-riding condition. Between the two critical speed, the ship makes either periodic surging or surf-riding, motion depending on the initial conditions. As a practical guideline to avoid the dangerous surf-riding, a simple method to obtain the critical ship speed and the critical wave height is proposed. By the analogy with other phenomenon such as Josephson effect in the superconductivity, the surf-riding is suggested to be one of the fundamental non-linear phenomenon in the physical science.
社団法人日本船舶海洋工学会の論文