This paper considers the assessment of comfortability and the motion control of cruise ship in waves. In the present study, MSDV (motion sickness does value) is chosen as a primary index to evaluate the passenger comfortability. MSDV is obtained by using a time-domain ship motion program, called WISH. Seasickness level is evaluated in a short period using the frequency-weighted RMS of vertical acceleration in a low frequency range, and then it can be used for long-term prediction. In addition, the present study includes the application of the roll stabilizing fin to cooperate with the evaluation of passenger comfort.
The comfortability of passengers in ocean environment is one of the most crucial elements in cruise ship design. There is high demand of reducing seasickness of passengers and controlling ship motions even in rough seas. There are a few indices to evaluate the comfortability of cruise ship, and some regulations by classification societies for passenger comfort are available. However, most of them are defined in the forms which are not easy to predict or consider the frequency ranges over 5Hz, which hull vibration is of primary interest. Since the motion of ship makes disturbances which provoke motion sickness or seasickness, we need to consider a solution to the cause of the seasickness, i.e. ship motion responses in waves. Many researches on motion sickness have been carrying out by experimental or analytic ways. Irwin (1881) explained that motion sickness can be induced by sensory conflict. The etiology of sensory conflict is that sensory signals from the eyes and the organ of balance do not agree. A series of studies by O'Hanlon and McCauley (1974), McCauley et al. (1976) and Guignard and McCauley (1982) have produced models for the frequency and magnitude dependence of motion sickness due to vertical sinusoidal motion, using a three-axis motion generator. In these studies, it was found that the most nauseogenic frequency range was found to be from 0.17 to 0.33 Hz.
