Research On Aerodynamic Noise Of Rearview Mirror Of Passenger Cars

When a car is running at high speed,the influence of aerodynamic noise on the cab exceeds other noises and becomes the main noise source.The A-pillar-rearview mirror area is the main source of aerodynamic noise at the front side window.The rearview mirror is a blunt body structure protruding from the outer surface of the car,and its modeling characteristics have a great impact on the aerodynamic noise of the car.At present,domestic and foreign research institutions have achieved some results in the research of aerodynamic noise of rearview mirror,but the influence of basic modeling factors was mainly studied using the rearview mirror-flat model.There are not many researches on the influence of real rearview mirror modeling factors on aerodynamic noise.Therefore,this article started with the real rearview mirror model,adopted the whole vehicle model,and studied the flow field and aerodynamic noise of the rearview mirror through numerical simulation and wind tunnel test.The wake vortex area was controlled and the direction of the wake vortex was guided by rationally optimizing the shape of the rearview mirror shell,thereby reducing the influence of the rearview mirror wake vortex on the aerodynamic noise of the front side window surface.Firstly,conducted in-depth reading of domestic and foreign literature in the field of automobile aerodynamic noise,summarized the generation mechanism and the latest advances of automobile aerodynamic noise,and mastered the research methods of aerodynamic noise of the rearview mirror.Secondly,the steady-state numerical calculation adopted the Realizable k-εmodel,and the residual curve was observed to determine whether the calculation had converged.The transient numerical simulation used the LES model based on the three sub-grid stress models of Smagorinsky-Lilly,WALE,and WMLES.The FW-H model was used to calculate the sound pressure level at each monitoring point on the surface of the front side window.The LES based on the WMLES sub-grid stress model was determined to be the optimal model for transient numerical simulation through wind tunnel test and numerical simulation benchmarking.Therefore,the research method of this subject was determined.In addition,the aerodynamic noise of the rearview mirror under different wind speeds was studied through wind tunnel tests,and it was found that the aerodynamic noise of the rearview mirror increased with the increase of vehicle speed,and the change was obvious in the mid-to-high frequency range of 1000-5000Hz.Then,based on the eddy current control theory,three optimization schemes of the rearview mirror were proposed.Scheme 1 was to streamline optimization of the shape of the mirror shell of the rearview mirror.Scheme 2 was to optimize the angle of the inside of the rearview mirror,and 5 angle schemes were designed.Scheme 3 was to arrange the bionic shark fin structure inside the rearview mirror shell.In order to further explore the influence of the height,arrangement angle,and spacing of the bionic shark fin on the noise reduction effect,the orthogonal experiment was designed and analyzed.The influence of each factor on aerodynamic noise was determined according to the maximum K_i value of different experimental factors.Then,the optimal bionic shark fin noise reduction scheme was determined.The three optimization schemes were calculated by the validated numerical simulation method.By comparing the streamline diagrams and velocity cloud diagrams of the original model and the three optimization models on the three planes of XOY,XOZ,and YOZ,the position and structure of the vortex in the rearview mirror tail were analyzed.It was found that the flow field in the rear area of the rearview mirror of the three optimization schemes had been improved,so it could be predicted that the three optimization schemes were helpful to reduce the aerodynamic noise of the rearview mirror.By comparing the sound pressure level curve at the monitoring point on the surface of the front side window,it could be found that the three optimization schemes had a positive effect on reducing the aerodynamic noise of the rearview mirror.