Research On The Impact Of Non-smooth Surface On The Aerodynamic Noise Based On The Vehicle Rear-view Mirror Base Model

With the rapid development of China’s auto industry,the automotive market is becoming increasingly competitive.People concern about the car power,safety,fuel economy,at the same time,the ride comfort of vehicle is also put forward higher requirements.The level of vehicle aerodynamic noise is one of the main factors affecting ride comfort.The complex flow field caused by high-speed airflow through the rearview mirror causes pressure fluctuations in the rearview mirror area,resulting in the pulsating pressure acting on the vehicle body.Pulsating pressure is the main cause of aerodynamic noise which seriously affects the car ride comfort.Therefore,the aerodynamic noise in the rearview mirror area is the focus of the aerodynamic noise reduction.The study shows that the spoiler effect of the bionic non-smooth surface has a certain effect on controlling the flow field structure and reducing the aerodynamic noise.This paper uses the characteristics of the rearview mirror base as the research point,through the three types of base modeling to start the study and explore the influence of base modeling on aerodynamic noise reduction of non-smooth surface.Then choose the base modeling with good aerodynamic noise reduction effect of non-smooth surface,establish the streamlined rearview mirror as the research object,and the aerodynamic noise reduction effect of non-smooth surface under lateral wind is further studied.Because of the importance of A-pillar and side-window area on the automobile aerodynamic noise,the flow field of the A-pillar and side window area is simulated based on the wedge.Base modeling uses three typical connections:side window full connection,side window half connection and outside board connection.The non-smooth surface is arranged on the rearview mirror cover.The flow state and vortex structure in the rearview mirror basin are calculated by SST k-ω method.Then,the sound pressure level spectrum of the side window area monitoring point is obtained by the combined method of DES and CAA.Based on the analysis of the steady-state and transient calculation results,the influence of the base modeling on the aerodynamic noise reduction of the non-smooth surface is studied.The results show that the side window full connection and side window half connection have better performance on the aerodynamic noise reduction of the non-smooth surface.On the basis of the above research,the streamlined rear-view mirror model is established with the side window half connection scheme to study the perturbation effect of the crosswind on the non-smooth surface noise reduction,and further verify the aerodynamic noise reduction effect of the non-smooth surface mirrors.Based on the standard MIRA model,the non-smooth pits are arranged at the edge of the rearview mirror cover.Through the simulation,the flow field structure,the pressure cloud and the sound pressure level curve of the monitoring point under the crosswind and no side wind conditions are obtained.The simulation results show that the scheme of bionic pits on the edge of the rearview mirror cover has a good effect on reducing the aerodynamic noise.And the disturbance of the crosswind also affects the aerodynamic noise reduction effect of the non-smooth surface.Non-smooth surface mirrors have the best aerodynamic noise reduction performance on the leeward side under the crosswind.