Influence Of Propeller Blade Deformation On Hydrodynamic Noise

Composite propeller is widely used in engineering.Under the action of fluid,its blade will produce large deformation,which has an impact on the propeller noise,and its location is the same as that of hydrodynamic noise.In order to explore the sound mechanism of non-cavitating noise of flexible propeller and study the influence of blade deformation on noise,a propeller noise prediction program based on FW-H equation is developed in this paper.Firstly,the unsteady hydrodynamic performance of the propeller is simulated to obtain the flow field data.Based on the macro command of CFD post,the second development of ANSYS is carried out,and the data acquisition script is written to quickly derive the flow field data such as the coordinates of each node,the pressure distribution and the shear stress distribution in the direction of motion under different time steps.Verify the data and write the data interface to provide the data basis for the subsequent propeller noise calculation.Then the noise prediction method is developed based on FW-H equation.The time domain integral decomposition of FW-H equation farrasat 1 formula is defined,and the position of fluid viscosity in the formula is deduced.The time delay,panel integral and time differential in the formula are treated accordingly.The noise prediction program considering viscosity under unsteady conditions is compiled.The flow field data is used for prediction,and the reliability of the program is verified by comparing with the numerical simulation results,It is proved that the prediction method is feasible.Then,the noise contribution of different sections of the blade is analyzed by using the noise prediction method.According to the diameter of the blade,the blade is divided into four regions,and the unit area is processed;However,with the increase of radius,the high frequency component becomes less obvious.The contribution of thickness noise increases with the increase of radius;The contribution of load noise increases first along the radial direction,but decreases at the tip.The variation trend of total noise is similar to that of load noise;From the axial observation,the change along the radius direction is not obvious,but has a slight increasing trend.Finally,the influence of blade deformation on hydrodynamic noise is studied by using the noise prediction method.The results of deformation are obtained by using user-defined function and simulation software to explore the influence of uniform deformation and periodic deformation on noise,and the influence of fluid structure interaction on noise under non-uniform wake.The results show that the uniform deformation has almost no effect on the noise compared with no deformation;When periodic deformation occurs,the total sound pressure level fluctuates about 2.91db;Considering the effect of fluid structure interaction,the total sound pressure level fluctuates about 4d B.It can be seen that the small deformation of rigid propeller has a certain impact on the noise,and the large deformation of composite propeller has a more obvious impact on the noise.