| With the development of automotive electronics technology, more components were mounted on the rearview mirror, such as the mirror heaters, electric mirror adjustment and video cameras; this has led to a growing weight of the mirror. The greater weight could lead to the greater vibration of mirror, and it has a serious threat to safety. Therefore, it is usually carried out in a dynamic performance evaluation test repeatedly during the design stage of car. This not only extend the development of the design cycle, but also research and development costs.The causes of mirror vibration include road roughness, mechanical vibration and airflow excitation. The reasons of airflow excitation include vortex shedding, earlier air separation, surface pressure fluctuation and turbulence shock. This study use flow-solid coupled in simulating vibration of the exterior mirror caused by the airflow. The research is divided into three parts, including study of flow induced vibration, flow induced vibration of a single mirror and flow induced vibration of a mirror which was mounted on vehicle.In this paper, a square cylinder was first selected for the basic model. The STAR-CCM + was used to computational fluid field, and Abaqus for the solid calculation. Data exchange was done in Collaborative Simulation Platform of STAR-CCM +. To obtain the vibration characteristics of the different frequency ratio under conditions of fixed mass ratio equivalent and damping factor. The results show that the vibration amplitude is small at low frequencies ratio; With the increase of vibration frequency ratio, the amplitude of the vibration becomes larger; At a frequency ratio close to 1, the vortex shedding frequency equal to natural frequency of the mirror, resulting in a significant amplitude peaks; When the ratio exceeds 1, the amplitude is significantly reduced.Secondly, a single mirror was choose for reducing the influence of A-pillar. Modal analysis and FSI(Fluid-Solid Interaction) simulation was performed on mirror. The results obtained are as follows: When the velocity is 20km/h, the frequency of vibration was close to the vortex shedding, the vortex shedding caused vibration; When the velocity is 30km/h, there is no vortex-induced vibration; With the increase of velocity, the vortex shedding frequency is increasing, the vibration frequency of mirror was locked in two fixed frequency. The amplitude of vibration was influenced by not vortex shedding but the strength of the wind field. But this influence begins to slow down when velocity is larger than 160km/h.Take the 1:1 Driv Aer as analysis model, using the fastback model structure and non-complex chassis. The influence of vortex shedding is weak when the difference was larger between vortex shedding frequency and natural frequency, and this situation become different when there is no difference. The frequency of mirror vibration is locked when there is no vortex shedding influence.At last, the yaw angle was considered to study the mirror different vibration characteristics. When the vehicle is traveling with yaw angle, body effect become strengthening on mirror vibration. Since the complex flow field of leeward side, flow field forces no longer present at one frequency. At the same time, due to changes in the structure of the flow field, the vortex-induced vibration effect is restarted. |
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