Numerical optimization of ship hull forms from view point of wavemaking resistance based on panel method

A computational method is proposed for the analysis of hydrodynamic perfor lance of ship s and the design of optimized hull form in shallow water and deep water with respect to the wavemaking resistance is presented． The method involves coupled ideas from two distinct research fi elds：nurnerical ship hydrodynamics and nonlinear prρgrε㎜ing tec㎞ique． Having the numerical tools fbr hydrodynamic analysis， a mathematical procedure for optimizing hull forms is developed． The optimal hull form design system enables the designer to include advanced resistance performance predictions at the early stage of design process， allowing a systematic evaluation of the resistance performartce characteristics as a function of the hull geometry．The wavemaking resistance of ships is estimated by means of Morino’s panel method extended tofree surface flow and into the influence of finite depth on the wave resistance of ships and PAFS is linked to the optimization procedure of Sequential Quadratic Programrning（sQp）technique． An optimum hull form can be obtained through a series of iterative computation subject to some design constraints．The developed optimization procedure in shallow water is demonstrated by choosing a mathematical Wigley（CB＝0．444）hull and a standard Series 60（CB＝0．60）hull． The optimization in shallow water is canied out at Froude number of 0.316 and the wavemaking resistance taken as an objective function arid the optimized hull forms are obtained for different depths of water． The specified Froude number corresponds to lower than depth critical speed since most of ships operating in shallow water below depth critical speed． The sinkage is an impoItant factor in shallow water and this method considered sinkage as a hydrodynamic design constraint during the optimization process．The numericai results of optimization procedure indicate that the optimized hull forms in shallow water）delds a reduction in wavemaking resistance．In the optimization of catamaran ship hull without and with airship forms bulb installed on the center plane of catamaran， a mathematical ship hull of cosine waterline and parabolic frame line has been chosen to carry out the fundamental study of the numerical optimization and the wavemaking resistance taken as the objective function．The optimization is carried out at two Froude numbers 0.45 and 0.50 respectively， which are around the last hump of the wavemaking resistance curve of catamaran ship and most of the catamaran ships are running in high－speed range． The optimized catamaran hulls without and with airship fbml bulbs show lower wavemakillg resistance with original ones around the design speed．The entire process of hydrodynamic analysis， geometrical modeling and optimization thus attempts to imitate the traditional hull form design procedure． The system of computer can be used to develop mathematically faired and hydrodynamically desirable hull forms from an existing ship．