Research On The Hydrodynamic Noise Of Marine Propeller Considering The Deformation Of The Blade

The application of elastic materials is one of the new breakthrough directions in the study of vibration reduction and noise reduction of marine propellers.Except for the radiated noise induced by marine main and transmission mechanism,the propeller is the significant underwater noise source of the ship.The hydrodynamic noise is produced by the fluid pulsation when the blades of the propeller cutting the water with a high speed.The equivalent Young’s modulus of the composite material is smaller than that of the high-strength alloy commonly used in the manufacture of the marine propellers.The blade of the composite propeller deforms periodically when suffering the unsteady hydrodynamic loads.The deformation and vibration of the blade will change the flow field characteristics of the flow around the blade which is directly related to the hydrodynamic noise of the propeller.The geometry of the propeller is complex.It is difficult to analyze the deformation characteristics of the composite propeller and the hydrodynamic characteristics of the fluid near the propeller considering the vibration of the blade,which restricts the research and application of the composite propeller.The development of computational fluid dynamics(CFD)and fluid structure coupling theory has brought convenience to the research of composite propeller.In this paper,a linear isotropic elastic material propeller is taken as the research object.A two-way fluid structure coupling numerical method is established to study the deformation and noise characteristics of composite propeller.The following works have been carried out:The stress,strain and the hydrodynamic characteristics of a three-dimensional elastic wing,modified NACA0009,are calculated using the two-way fluid structure coupling numerical method as the attack angle of the wing equals Odeg.The hydrodynamic characteristics of the elastic wing is simulated using the detached eddy simulation with the shear-stress transport K-Omega model.The stress and strain of the elastic wing are simulated using the finite element method.Comparing with the rigid wing,the fluctuation amplitude of the lift is larger,while the frequency of the lift is slightly smaller.The vortex shedding of the elastic wing has great difference with the rigid wing.One of the blades of E1619 propeller is taken first to analyze the influence of the grid scale and timestep on the two-way fluid structure coupling numerical simulation.Then,the deformation,vibration and the hydrodynamic characteristics of elastic E1619 propeller is analyzed as the advance coefficient J=0.71.The deformation and the vibration of the elastic propeller are discussed in detail in this paper.The thrust coefficient and the torque coefficient of the elastic propeller are smaller than that of the rigid propeller,while the propulsion efficiency of the elastic propeller is slightly larger.the blade of the elastic blade deforms under the hydrodynamic loads and vibrates periodically.The simulation module of noise in the commercial software Starccm+is used to simulate the hydrodynamic noise of the elastic propeller.The hydrodynamic noise of the elastic and rigid propeller are discussed in this paper.The directivities of the total sound level of elastic and rigid propellers are significantly different to each other.The total sound level of elastic propeller is smaller than that of the rigid propeller.