Time-domain analysis of passenger comfort on cruise ships under motion responses in waves

The assessment of passenger comfort in modern cruise ships is considered from a hydrodynamic point of view, in addition to improvement using stabilizing fins. Passenger comfort is evaluated in this study based on the symptoms of motion sickness on ships provoked by low-frequency whole-body vibration. Motion sickness dose value is an index used to quantify seasickness and is chosen as a primary index to evaluate passenger comfort. To calculate motion sickness dose value in the time domain, a time series of vertical accelerations should be processed using frequency filters, which are defined in the international standards and guidelines provided by classification societies as forms of transfer functions in the frequency domain. Digital frequency band–limiting and weighting filters are formulated as a form of infinite impulse response filter and then applied to the present case. Two pairs of stabilizing fins are equipped to reduce the roll and pitch motions and to improve the passenger comfort on a model cruise ship. A linear optimal control algorithm, linear quadratic Gaussian, is considered to actuate each stabilizing fin. Numerical computations are carried out based on practical operating conditions for the cruise ship model using a time-domain ship motion program, which integrates the motion control algorithm and the passenger comfort analysis. The results of computations show that passenger comfort on a cruise ship can be evaluated appropriately by computing the index motion sickness dose value in the time domain. The motion stabilization by the stabilizing fins can be considered as a good method to reduce the motion of the present cruise ship model and eventually contribute to improve passenger comfort.