Hull Form Optimization Based On The Vulnerability Of Parametric Rolling

Presently,the ships' stability is estimated based on International Code on Intact Stability,2008.Since it was made on the root of statistics and statics and the capsizing is more likely to happening when the ship is navigating on the wave and the accidents are caused by dynamic factors.To deal these defects,International Maritime Organization began the work of making the new generation intact stability which was basically completed in 2019.As one of the failure mode of the secondary intact stability,the vulnerability criteria of parametric rolling has been completed basically.Till now,many research institutions and companies have developed the software to estimate the vulnerability of parametric rolling,calculated the sample ships and studied the influence of the principle dimension on the parametric rolling.However the influence of the hull has not been researched.The feature of the line will be studies,the relationship between hull and parametric rolling will be researched and the way to design the hull which can avoid the parametric rolling will be found.The conclusion can provide reference for the design and protect the safety of the people and the goods during the sailing.Following is the introduction of the main content.(1)The program of ship line transform was developed based on the method of moving the control points of B spline surface and free-form deformation(FFD).A container ship,a fishery administration ship and a fishing ship were chosen as the parent ship,23 new ships were generated by changing the U or V degree of the stem,the flare degree of the bow and the lifting of the outline of the stern using the program.Those newly generated ships were grouped into to series;(2)The vulnerability of parametric rolling was estimated.Then the influence of the above three features on the parametric rolling was got by the result of the estimation.Changing the form of the stem from V section to U section,increasing the degree of flare or increasing the lifting of the outline of stern has an advantageous impact on the vulnerability of parametric rolling;(3)FFD was chosen as the method to transform the hull form,the Check 2 was chosen as the optimization objective function,the optimization variables were the moving values of the control points,the C11 container ship's front part was optimized by generic algorithm.In order to reduce the time cost by calculated,the fitness of the individuals were parallel calculated.The optimized ship's C2 is decrease 48.3%,the bow is in U section and the flare is decreased compared to the original ship.This proved that the influence of the lines' feature to parametric rolling is credible.