Research On Hydrodynamic Performance And Cavitation Characteristics Of A Cycloidal Propeller

Cycloidal propeller is a special marine propeller that appeared in the late twentieth century.It has good resistance to wind and waves,fast response speed,good maneuverability,superior hydrodynamic performance,with high efficiency,low noise level and long service life.The movement of the blade is composed of the revolution around the central axis and the autorotation around the rotation axis of the blade,so that it can achieve the purpose of generating thrust in the full angle range on the horizontal plane instantaneously.This kind of superimposed motion brings about more complex interactions between fluid and blades,and the accompanying complex cavitation characteristics.Studying the hydrodynamic performance and cavitation characteristics of the cycloidal propeller is of great significance to the improvement of its efficiency.This paper mainly takes the two-dimensional and three-dimensional numerical models of the five-blade cycloidal propeller as the research object:First,the appropriate turbulence model and boundary conditions are selected,and the convergence of the grid base size and time step of the two-dimensional numerical model is verified.Moreover,the force change of the propeller within one revolution is analyzed.The distribution of velocity,vorticity and pressure of the flow field after a stable complete cycle is analyzed,too.On this basis,the four factors,blade number,blade chord length,blade thickness and blade camber,are selected as variables to further explore the influence of geometric parameters on the hydrodynamic performance of the cycloidal propeller.Secondly,the computational domain grid is divided and the boundary conditions of the three-dimensional cycloidal propeller are set up.What’s more,the independence of the computational domain time step is verified and the possible similarities and differences in the force of the propeller blades between the two-dimensional and three-dimensional cases are compared.The velocity field and pressure field distribution of a certain section after the steady state achieved is also analyzed.Finally,based on the hydrodynamic model of the three-dimensional cycloidal propeller,an appropriate cavitation model is added.The effect of cavitation on the distribution of hydrodynamic coefficients,velocity field,pressure field and vorticity field has been studied and the cavitation number is selected as a measurement standard to quantify this possible effect.The hydrodynamic performance and cavitation characteristics of the propeller are studied by numerical calculation methods,which may provide reference value for future optimization design.