Aerodynamic Noise Analysis For A Vehicle Rear View Mirror

When vehicle runs at low speed,the main noise source is power train and tires.When it's speed over 100km/h,aerodynamic noise will become the main source of noise.The factors influencing the aerodynamic noise are: vehicle body shape,rear view mirror,wiper,sealing,wind direction,wind speed and vehicle speed,etc.As the position of rear view mirror is outside vehicle body,it has big influence for aerodynamic noise.Due to complain for aerodynamic noise from rear view mirror on a vehicle,build initial 3D model for rear view mirror,according to the noise transmission principle,based on the Lattice Boltzmann Method of CFD unsteady flow field,the structure input incentives and acoustic input incentives are calculated,based on the statistical energy analysis the interior acoustic field is calculated,then get the aerodynamic noise initial simulation curve.According to the simulation result,there is an obvious peak at 4000 Hz.Combined with subjective test result,this peak is the main cause for rear view mirror aerodynamic noise.Change 4 components of rear view mirror: mirror feet,mirror house,triangle plate and water blocking strip,after simulation,find that 3 kind of changing water blocking strip methods can reduce aerodynamic noise,but their difference is very small.According to the 3 kind of methods build porotype rear view mirror,and test them in wind tunnel,the test result shows that removing the water blocking strip on mirror feet and keep the water blocking strip on mirror house is the best method,it can effectively reduce the vehicle aerodynamic noise at 4000 Hz about 5 dB(A).