Research On Vibration Acoustic Radiation Of Composite Propellers

In recent years,composite materials have been widely used in shipbuilding due to his superiority.Composite propellers are one of the most important applications of composite materials in shipbuilding industry.Composite propellers made of composite materials interact with the fluid when working under water,which cause pulsating pressure on the surface of the blades that causes the vibration of the blades to radiate noise outwards.Compared with traditional metal propellers,the vibration and acoustic radiation characteristics of composite propellers are more complicated because of the different material characteristics of composite propellers Therefore,it is of great significance to study the noise law of composite propeller blade's vibration to improve the stealth of submarine and design of low vibration and low noise propeller.This paper combines computational fluid dynamics(CFD),acoustic infinite element method and finite element method(FEM).First,the hydrodynamic characteristics and blade deformation of composite propellers are analyzed and comparing the results with the metal propeller.Second,the unsteady pulsating pressure and vibration noise of composite materials are calculated and analyzed.The specific research content is as follows.Firstly,we calculate the hydrodynamic characteristics of propeller using three different turbulence models to calculate the thrust coefficient,torque coefficient and open water efficiency of propeller in different working conditions.Then,we compare the numerical results with the experimental values of the relevant literatures and analyze the error,which verified the accuracy of hydrodynamic model.The surface pressure distribution,profile pressure field,velocity field and track line of propeller are analyzed and the effect of fluid-solid coupling on hydrodynamic characteristics of metal and carbon fiber composite propellers was studied.The calculation results show that the RNG model has the highest accuracy in the three turbulence models.So RNG is the optimal turbulence model.Secondly,the fluid-solid coupling calculation of metal propellers and composite propellers under different working conditions is completed by combining CFD method with FEM method.The blade deformation,thrust coefficient and torque coefficient of composite material propellers and metal propellers under the same working condition are studied.The performance difference between composite propellers and metal propellers is analyzed.Finally,the unsteady periodic pulsation pressure of propeller is calculated and its distribution is studied,then we use ICFD function in ACTRAN,extracting unsteady pulsation pressure of composite propellers as noise source.the vibration acoustic radiation characteristics of composite propellers are calculated by using acoustic infinite element method.The acoustic pressure distributions at different frequencies are analyzed and the acoustic pressure directivity along the blade surface and axial direction is studied by arranging field points.The results show that the axial acoustic pressure radiation of the propeller is greater than that of the disk under the pulsating pressure.Both acoustic pressure of the disk surface and the axial direction are distributed like the word "8".The closer to the center of the propeller shaft,the greater the magnitude of sound pressure radiation and the results also show that the center of the propeller shaft has the maximum total sound pres sure.