Research On The Influence Of The Wing Mirror Optimization On Aerodynamic Noise Of A Car

As the main bulge on the outer surface of the car,the wing mirror affects the dynamics of the car.Due to the action of the flowing gas and the solid boundary,a large aerodynamic noise which is passed to the car through the window is formed in the vicinity of the wing mirror.The paper focuses on the influence of the wing mirror on the aerodynamic noise of the car.Two kinds of wing mirror optimization schemes are proposed: the first scheme is to change the tilt angle of the wing mirror cover so as to be parallel with the longitudinal axis of the vehicle,and the second scheme is to change the size of the wing mirror mounting base.And attempts to reduce the aerodynamic noise in the car by studying and optimizing the characteristics of the wing mirror.Firstly,the similarity between classical acoustic theory and aeroacoustic theory is explored from the theory.The finite element analysis method and turbulent numerical simulation method adopted in this paper are described.Based on this,the numerical simulation of the external flow field of the research object is carried out.The numerical simulation of the external flow field is divided into steady state and transient calculation process,and the numerical simulation of the external flow field is carried out in the fluid software Star-ccm+.Steady-state calculations use the Reynolds Time-Rate Method(RANS)and the k-epsilon turbulence model.The distribution of sound pressure level on the outer surface of three wing mirrors,the streamline diagram of the wing mirror and the distribution of sound pressure level on the side window glass near the wing mirror are studied.It is concluded that the wing mirror and the A-pillar region exist strong wind noise.The transient calculation takes the steady state calculation as the initial value,and uses the large eddy simulation(LES)method to analyze the pressure distribution map near the wing mirror and the wake velocity field of the mirror.By comparing the sound pressure level-frequency curve of the original wing mirror and the two optimized scheme wing mirror models at the monitoring point,the effects of the two optimization schemes on the aerodynamic noise and noise are analyzed.Secondly,the paper studies the inner noise level,and calculates the internal sound field aerodynamic noise by using the turbulent value calculated by the transient as the excitation source.According to the theory of random acoustics,the method of random excitation and acoustic-vibration coupling are used to calculate the interior noise.The interior noise calculation is performed in the acoustic section of LMS.virtual.lab.By comparing the original wing mirror and the two optimization schemes,the aerodynamic noise level of the wing mirror at the driver's outer ear can be seen: the scheme of changing the tilt angle of the wing mirror can reduce the aerodynamic noise of the vehicle by about 2dB compared with the original wing mirror.In the second scheme,changing of the size of the mounting base reduced the aerodynamics by 1 dB.The research shows that the optimization scheme one has a more obvious effect on changing the aerodynamic noise problem.Finally,an accurate wind tunnel test method is adopted to obtain the aerodynamic noise inside the vehicle.The wind tunnel test can effectively eliminate the road noise and engine noise components generated by the road test.The wind tunnel test was carried out in a wind tunnel center of a ground vehicle in Shanghai.The sound source localization method was used to capture the aerodynamic noise source.The main location of the aerodynamic noise was the wheel and the mirror area.By collecting the noise signal in the car and comparing the experimental values with the numerical simulation data,the accuracy of the numerical simulation model and method is verified,and it is concluded that the mirror tilting optimization scheme one can reduce the aerodynamic noise of cars when driving at high speed.