Simulation And Optimization Of The Rear View Mirror Factors On The Passenger Cars’ Aerodynamic Noise Performance

As extended points of the vehicle near the side window,rear view mirrors have significant influence on the aerodynamic noise caused by high-speed driving.In this paper,two factors,i.e.the shape of the mirror handle and the relative position between the hood and the mirror handle,are selected to investigate the effects on the aerodynamic noise of passenger cars.The aerodynamic noise in the rear view mirror region is optimized by using global optimization method and non-smooth surface.The realizable k-ε model is used for the steady state simulation where as the large eddy simulation(LES)method is used for the transient simulation.Such numerical simulation approach is validated by computing the sound pressure level of monitoring points and then comparing with the experimental data.The models of ship,rectangular and convex rear-view mirror handle are installed in the plate model and the vehicle model,the sound pressure level on the side window surface monitoring points and the flow field in the rear view mirror area of the three models are compared and analyzed.The results showed that the ship mirror handle is beneficial to the aerodynamic noise in the rear view mirror area.Under the condition of ±10 degrees yaw angle,on the windward side,the sound pressure level on the side window surface monitoring points of the ship’s rear-view mirror handle model is lower than the others;on the leeward side,the aerodynamic noise generated by the three rear view mirror handle models is close.On the leeward side,the sound pressure levels on the side window monitoring points of the three rear view mirror handle models are higher than those on the windward side.Based on the model of ship mirror handle rear view mirror,the aerodynamic noise in three relative positions,i.e.the hood is 22 mm higher than the upper surface of the mirror handle,the hood is parallel to the upper surface of the mirror handle and the hood is 40 mm lower than the upper surface of the mirror handle,are compared and analyzed.The results show that the sound pressure level on the side window surface monitoring points is the lowest when the hood is parallel to the upper surface of the mirror handle.The effects of ship,rectangular and convex rear view mirror models on aerodynamic noise performance are analyzed when the hood is lower than the mirror handle and the hood is higher than the mirror handle.The results show that the sound pressure level on the side window surface monitoring points of the rectangular mirror handle model is lower when the hood is lower than the mirror handle;the sound pressure level on the side window surface of the ship mirror handle model is lower when the hood is higher than the mirror handle.On the basis of the previous research,three factors,i.e.the minimum distance between the rear view mirror shell and the sail,the angle between the mirror shell and the sail,the ratio of shell thickness to channel height,are optimized by using the global optimization method.The optimal combination of three parameters is obtained which reduced the sound pressure level of the side window surface monitoring points by 0.5d B.The optimization of non-smooth surface to reduce aerodynamic noise is explored.The conclusion of this paper has positive meaning to vehicles styling and NVH design.