Study On Maneuvering Modelling Of Twin-Propeller Twin-Rudder Inland Vessels

As the main carrier of inland transportations,inland vessels have drawn growing attention to research for ship maneuverability performance,which is connected with navigation safety and economy.Inland vessels have to experience large traffic flows and complex environments,such as confined channels,shallow waters and frequent ship encounters,which raise higher standards for manoeuvrability performance of inland vessels.Besides,many inland vessels are equipped with twin-propeller twinrudder configurations,and the mechanisms of propeller-rudder interactions can be complicated.Therefore,studies on the maneuverability performance of inland vessels are very important.This thesis focuses on maneuvering studies of twin-propeller twin-rudder(TPTR)inland vessels.By Computational Fluid Dynamics(CFD)techniques,simulations on the isolated propeller or rudder in open water conditions and propeller-rudder interactions are conducted.A maneuvering mathematical model is proposed for TPTR inland vessels and then validated against free-running model tests data of a TPTR inland container model.The main contents of the thesis are listed as below:(1)Study on numerical methods for RANS simulations of rudder hydrodynamics.A NACA 0012 rudder profile is taken as the example,and meshes are generated with various mesh topology structures,calculation domain sizes,and node distributions.According to the accuracy of results derived from different mesh settings,impacts of mesh properties on calculation results are concluded and meshing strategies for open water rudder simulations are recommended regarding calculation efficiency and accuracy.The calculation results show that structured meshes such as C-type and Htype can achieve higher calculation efficiency and accuracy than hybrid meshes,while less manual interventions are required in hybrid mesh generations.(2)Numerical study on open water characteristics of the propeller.The KP505 propeller is studied in this part,and numerical methods are determined by selecting proper boundary layer mesh settings and turbulence model strategies.Two methods for simulating the rotating process of a propeller,a quasi-steady one(Moving Frames of Reference,MRF)and a time-accurate one(Sliding Mesh),are analysed.The comparisons show that Sliding Mesh methods can resolve the propeller wake evolution better,while MRF methods can calculate thrust and torque coefficients of the propeller more efficiently.(3)Numerical study on hydrodynamics performance of propeller-rudder systems.Referring to calculation methods of open water propellers and rudders,SPSR systems are studied numerically and validated against experimental data.In addition,the TPTR system of the 64 TEU ship model,the studied ship model in this research,is calculated.Hydrodynamic coefficients of the propeller and the rudder are obtained under different advance coefficients and angles of attack,and related flow details are presented by streamlines and velocity fields visualizations.(4)Maneuvering modeling of the TPTR inland vessels.Free-running model tests of a 64 TEU TPTR inland container are carried out in an outdoor tank,and benchmark data for validations are obtained.With the regression results based on CFD simulations of propeller-rudder interactions,a rudder force model considering propeller impacts is proposed.With the proposed rudder force model,the mathematical maneuvering model of TPTR inland vessels is established and then validated against experimental data..Focusing on the propeller-rudder system of the TPTR inland vessel,this thesis established connections between propeller-rudder configurations and ship maneuverability performance by integrating empirical methods and CFD-based model into maneuvering modellinfg,which improves the implementation of numerical modeling for TPTR inland vessels and provides evaluation strategies for propeller-rudder configurations considering ship maneuverability performance.