Research On The Effect Of Asymmetric Duct On The Ship Propeller Performance

With the development of the green ship concept,the energy conservation and emission reduction of ships has attracted worldwide attention.The installation of energy-saving appendages,as one of the energy-saving and emission-reduction technologies,is of great significance to study it.In this paper,an asymmetric duct designed according to the stern’s flow field was studied.The numerical simulation of the hydrodynamic,cavitation and noise performance of the ship-propeller model with or without the asymmetric duct was used to study the effect of the asymmetric duct on the performance of the propeller.First,this paper numerically simulated a KCS ship model with or without a free surface,and compared the calculated value with the free surface and the test value to verify the validity of the calculation method.Then this paper compared and analyzed the axial flow along the paddle surface of the bare ship with or without free surface.The results show that the distribution of the axial flow along the paddle surface of the ship with or without free surface is basically the same.Therefore,a numerical method without free surface is adopted to caculate the ship-propeller model.Secondly,this paper used STAR CCM+software to calculate the hydrodynamic performance of the ship-propeller model and compare the calculated value with the experimental value.The hydrodynamic performance of the ship-propeller-asymmetric duct model was numerically simulated and compared.The effects of asymmetric ducts on the efficiency of the propeller,the pressure distribution on the propeller surface,the axial flow of the propeller near disc surface,the propeller disc surface,and the wake vorticity generated by the propeller were studied.The effects of the asymmetric duct on the blade vibration were studied by exploring the pulsation amplitude of the propeller thrust and torque after the asymmetric duct was installed.Then this paper analyzed the influence of the asymmetric duct in the oblique flow.Then,the Schnerr-Sauer cavitation model was used to numerically simulate the cavitation performance of the E779A propeller,and compared with experimental values to verify the feasibility of the cavitation model.Then the numerical simulation of propeller cavitation of the ship-propeller model and the ship-propeller-asymmetric duct model were conducted,and the general laws of cavitation of the propeller behind the ship and cavitation of the propeller were obtained.The variation of the cavitation area of the propeller with asymmetric duct was also studied.Finally,the acoustic module in the STAR CCM+software was used to simulate the propeller noise of the integrated ship-propeller model and the propeller noise of the integrated ship-propeller-asymmetric duct model.The sound pressure level spectrum curve,sound pressure level directivity curve and the overall noise level of the propeller without the asymmetric duct and the propeller with asymmetric duct were discussed.Ans the influence of the asymmetric duct on the noise level of the propeller was studied.