| With the implementation of the national strategies to strengthen transportation and oceanic power,domestic researchers have increasingly high expectations for the study of ship maneuverability performance.Understanding a ship’s maneuvering performance is a critical prerequisite for assessing its safety,which helps crew members operate ships better,and the ship maneuverability simulator pioneered by Dalian Maritime University greatly convenience for evaluating the operational capabilities of crew members.Studying the hydrodynamic derivatives of ship maneuverability can provide new ideas for modeling navigation simulators,Traditionally,hydrodynamic derivatives are obtained through multiple r egression of data from tank experiments,and empirical formulas estimated from multiple regression are used to estimate hydrodynamic derivatives.However,with ships becoming larger and ship designs becoming more complex,traditional methods have gradually become unsuitable for modern ships.Nowadays,researchers can use the least squares method to fit test data to the hydrodynamic mathematical model of ship motion to obtain hydrodynamic derivatives,but this fitting method requires a large amount of data.On the other hand,the CFD method can provide numerical experimental data support for researchers.To further improve the parameter information of the hydrodynamic derivatives of ship maneuverability in navigation simulators,this study used commercial software STAR-CCM+,and the CFD method to obtain the hydrodynamic derivatives of ship maneuverability through numerical simulation of various movements under planar motion mechanisms.The important parameter of trim was also included in the simulation experiment to obtain the hydrodynamic derivatives of ship maneuverability under trim conditions.The main research content of this article is as follows:(1)Establish numerical tank suitable for PMM tests.A numerical towing tank was simulated,and the overset mesh technology was used to divide the numerical tank and the geometric ship model into meshes.The mesh accuracy,convergence,and independence of time step were analyzed,and the suitable mesh scale and time step for the three types of motion simulation were obtained.Finally,the expected results of the planar motion mechanism were simulated,laying the foundation for further obtaining hydrodynamic derivatives.(2)Derive a numerical PMM test method for obtaining third-order nonlinear viscous hydrodynamic derivatives.The methods for obtaining various hydrodynamic derivatives were introduced from three aspects: traditional calculation methods,empirical formula estimation methods,and the use of least squares fitting empirical data.In particular,the der ivation process of the theoretical model used in this study for the use of least squares fitting and the transformation method of the fitting objective function were emphasized.A theoretical model formula for least squares fitting data in the planar motion mechanism experiment was derived,providing a theoretical model for subsequent researchers to use this method for obtaining hydrodynamic derivatives.(3)Incorporate the calculation method for hydrodynamic derivatives in numerical PMM tests with consideration of trim effects.Currently,research on ship manoeuvrability hydrodynamic derivatives under trim remains insufficient.Adding the important parameter of trim into the numerical simulation process produced results that are more consistent with actual ship operation conditions,and the linear hydrodynamic derivatives of the standard model KVLCC2 and the results of the water tank experiments conducted at the SIMMAN2008 seminar were compared.The corresponding errors were within 10%.For the nonlinear hydrodynamic derivatives,comparing the hydrodynamic data obtained from the numerical simulation with the results of the water tank experiment yielded errors that were also within10%,achieving satisfactory results.For the Yu Kun ship numerical values and t he numerical values of both ships after adding trim,compared with the empirical formula,the errors of the obtained linear hydrodynamic derivatives,nonlinear hydrodynamic derivatives,and cross-coupling derivatives were within 15%,providing reference significance for the research on ship manoeuvrability hydrodynamic derivatives under trim.Through this research,the parameter information of ship manoeuvrability hydrodynamic derivatives under trim conditions in navigation simulators has been filled,provi ding data support for subsequent researchers to further explore the impact of trim on ship manoeuvrability.Simultaneously,the hydrodynamic derivatives of ship maneuvering characteristics provide a hydrodynamic modeling approach for building navigation simulators. |
