Study On Parametric Rolling Prediction Of Full Scale Container Ship Based On A Hybrid Method

Parametric rolling(PR)in head or following waves has been considered as one of the main dynamic stability failure modes in the development of 2nd generation Intact Stability criterion by the International Maritime Organization(IMO).With the promulgation and implementation of the new criteria,the prediction of PR vulnerability will from academic research gradually entering engineering application stage,including full scale ship design and optimization.Therefore,based on previous studies,it is necessary to further develop practical numerical prediction method that applicable to engineering.Especially study selecting proper calculation methods of motion and roll damping suitable for the prediction in early design stage,and carrying out study for effect of environmental factor on the accuracy of vulnerability prediction.In addition,according to the design characteristics of container ships,which has been reported several accidents,this kind of ship could also appear large lateral acceleration response due to large amplitude of PR.To ensure the safety of the crew,it is also necessary to study the potential hazard level due to this kind of response to ship operation.In this research,typical full scale ships such as large and medium container ships have been adopted for the study on parametric rolling vulnerability prediction of full scale ship.Firstly,a hybrid numerical prediction method based on potential and RANS methods is developed for simulation of parametric rolling.The validations have been conducted for model tests results of 6 ships,and comparison study with two other numerical method has also been carried out.Satisfactory accuracy and applicability for engineering has been proved.It is suitable to be utilized for analysis especially at the early design stage where one often lacks experiment data.Secondly,the effect of wind load on PR vulnerability prediction has also been analyzed based on numerical simulations of four full-scale ships.On the basis of the above work,according to model tests of two container ships,comparison for two control schemes based on frequency detuning control principle are also studied,and suggestions are given.Destructive effect of PR has also been studied,which focus on evaluating hazard level of acceleration response induced by PR and damage of course keeping ability in low speed due to PR.In the view of selection of method for estimating roll moment of inertia for the control scheme,relevant suggestions are also given,including an improved simplified empirical approach.Finally,based on the draft second generation stability criteria made by IMO,147 loading conditions of 38 full scale ships in 10 types were analyzed.The vulnerability level,vulnerable ship types and parameter ranges of loading conditions of current ship designs were obtained.Suggestions on development of direct stability assessment have also been given.These results could be reference for future design and development of criteria.