Numerical Analysis On Hydrodynamic Performance Of Ducted Propellers

Ducted propeller can maintain high propulsion efficiency under heavy load condition and good working condition in large working range in oblique flow.Due to these reasons,Ducted propeller is used widely as propulsors for modern ships.In recent years,with the development of CFD(Computational Fluid Dynamics)method and improvement of commercial computational fluid dynamics software,most of complicated engineering problems can be solved accurately and quickly by CFD software,and the CFD method is more and more widely used in the field of ship hydrodynamics.In this paper,based on the CFD method,the ICEM software is used to model and mesh the ducted propeller and its fluid field.Fluent software is used to calculate and analyze the steady open water performance in axial uniform flow,the unsteady open water performance in oblique flow and the steady cavitation performance.Firstly,in this paper,three dimensional model and different gird number of fully structured meshing for the ducted propellers consisting of JD7704 duct and Ka4-55 propeller is modeled using ICEM technique,the Moving Reference Frame(MRF)method is used to predict the open water performance by using different turbulence models,and the results are compared with the experimental results.Satisfactory results are obtained and it is proved that the modeling,meshing and calculation methods used in this paper is feasible.In the analysis of the open water performance of the ducted propeller,the influence of diameter and length of the duct on hydrodynamic performance of the propeller is calculated.The accelerating and decelerating ducts are obtained by changing the camber and angle of attack.The effects of dually ducts consisting of multi-segment wings are compared and analyzed,and the variation trends are summarized.In this paper,the unsteady open water performance in oblique flow of ducted propeller consisiting of JD7704 duct and Ka4-55 propeller and BD12 duct and D4-70 propeller is calculated respectively.The pressure distribution of propeller blade and duct,the change of thrust and torque produced by propeller and the velocity distribution in the flow field are analyzed.The results show that the existence of the duct can reduced the fluctuation of propeller's thrust and torque significantly in oblique flow.Finally,this paper takes the BD12+D4 series ducted propeller as an example to calculate the steady cavitation performance of the ducted propeller,and the numerical results are analyzed and provide a reference for the calculation of the cavitation performance of the ducted propeller in the future.