Motion and Passenger Discomfort on High Speed Catamarans in Oblique Seas

A two dimensional Green function solution for the transient motion of water sections is used in a high Froude number strip theory to determine the motion response of high-speed vessels in head and oblique seas. The method is validated by comparison with published data for the heaving, pitching and rolling response of three catamaran hull forms at high Froude numbers representative of the Froude number of typical high speed catamaran ferries. A frictional damping term was introduced to exactly match resonant motion maxima. The method is then applied to investigate the effects of hull spacing, sea direction and motion control systems. Finally the response of an 80m 1800 tonne vessel is investigated and the increase of motion sickness incidence with significant wave height and sea direction is investigated. In larger seas the maximum motions occur when the sea is taken on the bow, but in smaller, shorter period seas the maximum motions occur when the sea is taken on the quarter. Motions reduce rapidly as the sea direction approaches the beam.