The Parametric Design To Hull Form

Parametric design system of special product has been widely applied since 1990s and accordingly freed the designers from a mass of trivial matters, which not only improved the design efficiency and enhanced the ability to rapidly react to the market, but also reduced the information storage. In shipbuilding, due to the diversity of the demand of ship owners and complexity of the hull form, it is always repetitious to modify the hull form and carry out its corresponding performance computing, which brings the necessity of the parametric design to hull form.The technology of the design to mathematic hull form has been developed well after a long time of research. However, the prospective object is always difficult to achieve as the hull form derived from characteristic parameters and curves is dissimilar from the practical hull form. In this paper, the parametric design method to regular hull form is proposed based on the technique of representing the hull form by NURBS. According to this method, the longitude curves and the sections are derived from characteristic parameters, and then the faired practical hull form could be obtained.In view of the complexity of the curves and the surface of ships, it seems to be impossible to express them by a uniform formula before the method of NURBS was used. In the paper, the whole hull form is successfully represented by a uniform NURBS formula by using the algorithm of NURBS curve, the NURBS representation of quadratic curves, the correcting boundary conditions as well as the parametric method. With the application of NURBS, the data of hull form could be conveniently imported to Shipflow, Fluent, MaxSurf, Napa, Tribon and other softwares for the analysis, design and manufacture of ships.This paper considers the parameters of bulbous bow and stern, adopts the centroid of the area between section and design waterline as the characteristic parameter and discusses the maximum curvature points. Consequently, the parametric design to regular hull form is achieved and the relation between the hull form and the characteristic parameters and curves is established, by which the design and optimization of hull form is transferred to the design and optimization of fewer parameters and curves affecting the hydrodynamic performance.In recent years, the demand to hydrodynamic performance has been improved and the update of the hull form has been accelerated. Therefore, the existed resources of hull form cannot satisfy the new demand, which brings the new challenge to the traditional design method for hull form. However, the application of the parametric design to hull form provides the means for quick generation and variation of hull form to hydrodynamic optimization, which makes it possible that the hull form with excellent hydrodynamic performance can be created quickly and efficiently. Applying the parametric design to hull form and guided by design experience, the longitude characteristic curves and the parameters of stern are optimized in this paper. And the numerical simulation results of the optimized hull show that the non-uniform level of wake and the wake peak of propeller plane are decreased remarkably, and that the wake distribution is improved.