engleski

COMPARISON OF LINEAR SEAKEEPING TOOLS FOR CONTAINERSHIPS

The size of modern ultra-large containerships is such to fall outside the scope of the validity of rules of ship classification societies. Furthermore, in design and operation of large containerships important hydroelastic effects appear in addition to the rigid body response. Therefore, design loads for those ships are to be assessed based on direct seakeeping analysis. The aim of the present paper is to compare linear seakeeping tools in frequency-domain that may be used in different stages of ship design. The simplest tool is closed-form semi-analytical expressions formulated by Jensen, which are intended for ship conceptual design. Next tool in the comparison is the linear strip theory, which is very old, but still a very popular tool for ship seakeeping assessment. Finally, the most advanced tool employed in this study is the modern 3D panel method. The comparison is performed for 3 containerships of different sizes, and, when available, with experimental results from model tests. Two ship responses on regular waves that are analyzed are vertical wave bending moment at midship and relative velocity at bow. For each ship, two ship speeds and two heading angles (head and bow seas) are considered. Extensive comparison enables useful conclusions to be drawn.

containership; seakeeping; wave loads

nije evidentirano