One key aspect of cruise ship design is satisfaction with the onboard motion-induced comfort standards. Such standards imply evaluating motion-related indices, such as the motion sickness index (MSI), in several locations along the vessel. The assessment requires dedicated seakeeping calculations to predict vertical accelerations in the selected locations for comfort analysis. The requirements of the seakeeping calculations force designers to tackle this issue in a relatively advanced design stage, with hull form and the general layout already fixed. However, the comfort issue should be addressed already in the concept design phase, proposing an effective design strategy oriented to comfort satisfaction. To this end, the present article proposes a methodology for the comfort assessment of cruise ships in the concept design phase. Starting from a database of 25 vessels where seakeeping calculations are available for head seas at several speeds, dedicated regression formulae have been developed for the vertical motion transfer functions (TRFs). The Fourier model employed to regress the real and imaginary parts of the TRFs fits well with the initial database. Furthermore, the model has been tested on an external ship and compared with the standard procedure for MSI evaluation in a sea area of interest, showing good agreement with the obtained results.
