Research On Bionic Design Of Aerodynamic Noise Of Airfoil And Elliptical Section Rods

With the advancement of science and technology and the improvement of people’s living standards,consumers pay more attention to the comfort of transportation.An important indicator for evaluating ride comfort is aerodynamic noise.Rods are a common component in vehicles,such as aircraft landing gear,car luggage racks,and high-speed rail pantographs.During the high-speed driving of vehicles,these rods will generate strong aerodynamic noise,which is harmful to drivers and passengers.It will cause great interference and affect the riding comfort and driving safety.The traditional noise reduction method has encountered a bottleneck,and it is difficult to continue to greatly reduce the aerodynamic noise of the rod.Therefore,it is of great significance to study the generation mechanism of aerodynamic noise of airfoil and elliptical section rod based on the idea of bionics,and to conduct bionic optimization research on the aerodynamic noise of rod.In this paper,the STAR-CCM+software is used for simulation,the large eddy simulation is used to solve the near-field unsteady flow,and the FW-H equation is used to predict the far-field noise.The main contents are as follows:(1)Based on the standard NACA0012 airfoil,the aerodynamic noise of thin airfoil section members is studied and a bionic noise reduction scheme is proposed.Firstly,numerical simulation and prediction of the near-field flow and far-field noise of the airfoil are carried out by using the mixed calculation method of large eddy simulation and acoustic comparison,and the acoustic wind tunnel experiment is carried out,and the numerical simulation results of the airfoil are compared with the acoustic wind tunnel experimental results,which verifies the accuracy of the numerical simulation results.Then,the serration structure of the silent owl trailing edge is abstracted,and four bionic serration structures are designed,which are added to the standard airfoil trailing edge to explore the noise reduction effect of the serration structure of different sizes.It is found by calculation that under the conditions of 0° attack angle and 10° attack angle,the serrated structure of the airfoil trailing edge has a certain noise reduction effect.When the angle of attack is 0°,the maximum far-field SPL is reduced by3.5dB.When the angle of attack is 10°,the maximum far-field SPL decreases by 1.6dB.Finally,the influence of the tooth width and tooth height of the trailing edge sawtooth on the noise reduction effect is summarized.It is found that when the tooth width is constant,the larger the tooth height,the better the noise reduction effect;when the tooth height is unchanged,the larger the tooth width is,the noise reduction effect is better.That is,with the increase of the sawtooth size,the noise reduction effect is more significant.(2)Based on the thick elliptical section rod,the aerodynamic noise of the elliptical section rod is studied and a bionic noise reduction scheme is proposed.First,a wind tunnel PIV(Particle Image Velocimetry)experiment was carried out on the elliptical series cross-section members,and the large eddy simulation method was used to simulate them.The simulation results were compared with the wind tunnel experimental results to verify the accuracy of the simulation results.Then,by extracting the biological surface features such as shells and sharks,the bionic structures of grooves,pits and V-groove are abstracted,and added to the surface of the elliptical section bar.The acoustic analog hybrid calculation method is used to explore the noise reduction effect of the bionic pit-groove structure.The results show that the groove,pit and V-groove structures have certain effects on controlling the far-field aerodynamic noise of the elliptical rod,and the maximum reduction is 12.1dB under the condition of 50m/s incoming flow.Among them,adding an elliptical rod with a V-groove structure can effectively reduce noise at each far-field monitoring point,with a maximum reduction of 5.4dB.Finally,the reasons for the differences in the aerodynamic noise of different bionic rods are summarized,and the reasons why the bionic structure can reduce the aerodynamic noise of the elliptical rods are analyzed from the perspective of the development of the flow structure.(3)Based on the asymmetric section rod,the aerodynamic noise of the asymmetric section rod is studied and a bionic noise reduction scheme is proposed.Firstly,the wind tunnel PIV experiment and numerical simulation are carried out on the asymmetric cross-section member to verify the accuracy of the simulation results.Then,by extracting the surface features of humpback whales,the bionic structure of bumps is abstracted,and it is added to the surface of the asymmetric section member to explore the noise reduction effect.The results show that the bionic asymmetric structure can effectively reduce the far-field noise,and the maximum reduction can reach 15.1dB.Adding bump structures on the surface of asymmetric rods can reduce an additional 3.4dB compared to asymmetric rods without bumps.Finally,the reasons for the differences in the aerodynamic noise of different asymmetric rods are summarized,and the reasons why it can effectively control the aerodynamic noise of elliptical rods are analyzed from the perspective of velocity cloud map,pressure cloud map,vorticity map and other flow fields.In summary,this paper combines the rod wind tunnel experiment and numerical simulation to analyze the reasons for the difference in the aerodynamic noise of the rod with different airfoils and elliptical sections,summarizes the laws and results of bionic noise reduction,and provides new ideas for rod noise reduction in the future.