Optimal shape design of a floating body for minimal water wave forces

Abstract

Water waves are the most significant excitation source for floating vessels. The motion of floating vessels needs to be stable against a random water wave environment. In this study, the authors try to find an optimal shape for a floating body that gives minimal water wave excitation forces for a given water wave over a predefined frequency band. First, we propose a shape optimization formulation with a displacement constraint of which the objective function is to minimize water–structure interaction forces. For the calculation of water wave forces, high-order boundary-element analysis software is developed under an assumption of linear hydrodynamic potential theory. The analysis software is plugged into an optimization toolbox in MATLAB software in order to find the optimum under-water shape of the floating body. Two numerical examples are introduced to show the validity of the proposed optimization formulation: hemisphere and pontoon problems. Various shapes that give minimal heave and/or surge water-excitation forces are sought.