A comparative study has been performed by comparing the ship motions and wave loads computed by different ship motion programs. Recently, a time-domain ship motion program, WISH has been developed under the support of five ship building companies and Korean Register. WISH is based on B-spline Rankine panel method which is capable to solve linear and nonlinear seakeeping performance including hull-girder structural loads. In the present paper, the linear and nonlinear motions and loads obtained using WISH are compared with those of commercial code and experimental data for LNG carrier, Hanjin containership, and S175 hull, showing a good agreement.
The analysis of motion responses and structural loads is an essential element for ship design. Thanks to the recent trend of lengthening ship size, the demand of nonlinear analysis for the prediction of ship motions and global hull-gird loads is high. Some programs, distributed mostly by ship classification societies, show the capability of nonlinear analysis, and it seem that the application of such programs will be getting more popular. These programs are mostly based on Rankine panel method which is very practical and efficient to extend nonlinear analysis.
Dawson (1977) gave an inspiration to many researchers to apply the Rankine panel method for wave resistance problem, and later Sclavounos and Nakos (1988) provided an important theoretical foundation by conducting a thorough stability analysis for the Rankine panel method. Nakos (1990) developed it to a frequency-domain solver on unsteady ship motion problem. Lin and Yue (1990) and Kring (1994) then extended to time-domain problems, and later extended it to nonlinear problems (Lin et al., 1994; Kring et al., 1996). These programs were developed to SWAN2 and LAMP2, which have worldwide fame for nonlinear ship motion analysis in time domain, and laterdeveloped to WASIM (DNV) and NLOAD3D (ABS), respectively.
