Numerical Study On The Energy Saving Effet Of Twisted Rudders

Due to the seriously increasing environmental disruption and resource consumption,energy saving has become an urgent need in the society.The twisted rudder is a new-type energy saving appendage of ships,and can reduce cavitation on the rudder surface and improve the propulsion efficiency if it is designed appropriately.In this thesis,a numerical method based on solving the RANS equations is applied to simulate the viscous flow around a twisted rudder in three different systems: i.e.,the rudder in open water,the rudder behind a propeller and the rudder in a hull-propeller-rudder system.The sliding mesh technique is used to simulate the rotating propeller and the turbulence is modeled by the RNG k-? model.By simulating the flow around the rudder in the three systems,the pressure distribution on the rudder surface,the pressure contour at different sections of the rudder,and the lift and drag of rudder under different rudder angles are analyzed and compared with those of a conventional rudder.Besides,with the aim of increasing the rudder effect,a twisted rudder is designed according to the wake field of the propeller.The numerical calculations for twisted rudder in propeller-rudder and hull-rudder-propeller system are conducted to determine the self-propulsion factors;the results show that the designed twisted rudder can achieve the energy-saving effect as expected.The numerical method applied in this thesis can properly simulate the incompressible and viscous flow around a twisted rudder in the three systems mentioned above to study the hydrodynamics of the rudder and the effect of propeller wake field on twisted rudder.The conclusions have reference values for designing the twisted rudder.In addition,the numerical prediction of the self-propulsion factors for ships with a twisted rudder is helpful to ship designers.