Hull form optimization based on calm-water wave drag with or without generating bulbous bow

Abstract

In the ship design process, hull form design and optimization play an important role. In the research and engineering fields of hull form optimization, the resistance performance is most noticed among all the hydrodynamic performances. In this paper, we focus on the calm-water drag optimization for a high-speed slender hull without a bulbous bow, and the generation of the bulbous bow is introduced in detail, such as the hull form deformation methods and the knot-insertion procedure for the NURBS surface. Two optimization cases are given. In case 1, only shifting method is used, while in case 2, shifting and Radial Basis Function (RBF) methods are both used. During the hydrodynamic evaluation of the new sample hulls, the potential flow solver is applied, and the verification and validation procedure is done at first. The genetic algorithm is used to obtain two optimal ships with minimum wave drag. Optimization results show that even when we do not generate a bulbous bow, the optimal hull will have a relatively big decrease of the wave drag coefficient. However, favorable interference of the wave systems conducted by the generated bulbous bow can help reduce the wave drag coefficient to a greater extent, showing that the bulbous bow generation method proposed in this paper has potentials in the resistance optimization of the medium- or high-speed ship hulls.