Research Of Pure Loss Of Stability And Parametric Roll Vulnerability Criteria On Surface Naval Ships

The current intact stability criteria for naval ships employ an assessment method based on hydrostatic theory,and are also weather criteria based on experience.So they are not able to ensure safety of stability of naval ships when in severe sea conditions.2nd generation intact stability criteria set by IMO at present are based on dynamic stability theory and contain the main failure modes of ship intact stability in waves.To contain assessment of stability for naval ships in waves and frame their behaviors better,SGISC are considered being used as a tool in recent years,and integrating present navy ship intact stability criteria in the perspective of ship performance assessment in a seaway.Nowadays pure loss of stability and parametric roll vulnerability criteria in SGISC has been determined.In order to carry out practical feasibility tests,applications of level one and level two vulnerability criteria are carried out on 2 representative frigates with different sizes in China.The principle is to select 4 loading conditions for each frigate respectively,and assume a series of centers of gravity for each condition.Then carry out calculations on those assumptions according to pure loss of stability and parametric roll vulnerability criteria updated from SDC4 conference in 2017.Then get Zg_max of each loading condition with bisection method and compare the results with those from the present naval ship regulation.Stability assessment of feasibility for the two new criteria on naval ships when navigating in waves and ships'vulnerability for the two failure modes are got by analyzing the calculating results.Also,the research compare the level of severity of vulnerability criteria in SGISC with the present naval regulation.Vulnerability criteria in SGISC has been used as a tool for assessing the behaviors of naval ships in waves during the initial stage of design internationally.So the paper takes the frigate 3XA as an example.Firstly,finish hull modeling by taking advantage of NAPA via CAD graphic documents.Next transform the ship hull by changing 7 ship hull parameters through CAESES,and a series of ship hulls are generated.Then macro codes are developed on basis of the computer language C to export data points of all the new ship hulls,and carry out calculations of pure loss of stability and parametric roll with these data points.Finally,sort these ship hull parameters according to their sensitivity to pure loss of stability and parametric roll vulnerability respectively and analyze the influence rules of every ship hull parameter brought to the two failure modes.What has been done aims at providing technical references for naval ships'stability design when navigating in waves.