Hull Form Optimization For Rapidity Based On OPTShip-SJTU

With the increasing tension of energy supply,energy conservation and emission reduction are gradually attracting people's attention.EEDI brings new challenge to hull form design for various types of ship,and hull form optimization has become a key technology to be overcome urgently.At present,most hull form optimization is taken for high-speed ship,and little for low-speed full ship and even multi-hull ship.Therefore,hull form optimization for various types of ship is explored in this thesis,providing reference for related research.An in-house ship hull form optimization solver,OPTShip-SJTU,is taken in this thesis.The geometry of hull form is modified by shifting method and Free Form Deformation(FFD)method.Neumann-Michell(NM)theory and RANS method are taken in different optimization problem to evaluate the objective functions for ship hydrodynamics.Single-objective optimization algorithm,Genetic Algorithm(GA),and multi-objective optimization algorithm,NSGA-II,are utilized to solve the optimal hull.And Kriging approximation model is taken to evaluate ship performance instead of numerical method in the optimization process.In order to verify the reliability of the hull form optimization solver,the fore body optimization for KCS is carried out in this thesis.The results verify the reliability of Kriging approximation model,as well as the reliability and efficiency of NM numerical method for resistance optimization for medium or high speed ship.The total resistance of optimal hull decreases obviously,and there exists superposition of crest and trough in the flow field,causing favorable wave-making interference.Then,the fore body and aft body optimization for JBC,a typical low-speed full ship,are successively carried out.The results of single-objective optimization show that the flow separation near the stern is obviously improved,causing less vortex and great reduction of viscous pressure resistance.And the results of multi-objective optimization show that not only the total resistance greatly reduces,but also the wake quality of the propeller disk significantly improves.Finally,hull form optimization for a high-speed quad-hull ship is carried out,not only the demihull form,but also the transverse and longitudinal spacing,are modified at the same time.And the results show that wave-making resistance decrease obviously due to the favorable wave-making interference between the optimal demihull.The achievements obtained in this thesis show that OPTShip-SJTU has excellent applicability and reliability.And the results provides some guidance and reference for the hull form optimization problems for various types of actual ships.