| The rearview mirror is a bulged part of car exterior, which has an important influence on aerodynamic noise of car. Nowadays, most of the studies on the rear mirror aerodynamic noise are concentrated on analysis and optimization of the specific shape of rear view mirror, which lack of comparison and systematization. Domestic studies mainly focus on the mirror style, and research on the influence of base shape is few. In view of this, the styles of rearview mirror base are divided into three types in this paper. The flow field characteristics of different models and the influence on vehicle interior noise are also analyzed.Firstly the numerical model is established and the flow field calculation domain size of car body is determined. Because the autobody is symmetrical, half autobody model is used to save the calculation time. After that, a numerical simulation on vehicle flow field is made in this paper, and the boundary layer grid on body surface is generated which meets the requirements. Grid in key area (near side window) is further meshed so that the simulation could be more actual. Flow field simulation process is divided into steady-state simulation and transient simulation. The steady-state simulation selected realizable k?εmodel to analyze flow field and pressure distribution characteristics on body surface. According to sound power levels distribution, we could identify noise source which provided a reference for the interior noise analysis. The Large eddy simulation (LES) is selected in transient simulation, and relevant parameters such as the time step is determined by the eddy current cycle near rear view mirror.In transient simulation, the non-uniform and layered layout mode is applied in the selection of monitoring points in lateral window, which can not only analyze the noise level of key positions, but also the mean value that plays a part of"weighting". Thus it can better reflect the whole situation of lateral window noise. This paper makes a comparison of the spectrum data of monitoring points in detail and explains the reasons for the differences. The results keep a good consistency with the flow and pressure distribution. In order to predict the interior noise, noise spectrum data which is obtained in transient simulation process is set as the loading incentive and imported to SEA model. Because SEA can't calculate the precise noise value at certain point and the average noise value of a region can be gotten in it. The influence of body's detail structure is not obvious, thus, autobody SEA subsystem is simplified. The partition,connection and material property, as well as key parameter determination and loading incentive selection of SEA subsystem are particular introduced in this paper.Based on the simulation process delivered before, the influence of three base modeling (side-window half connection,side-window whole connection and door outer panel connection) on interior noise in different frequency range is obtained. This paper analyzes the reasons and gets a series of significant conclusions. Finally, this paper puts forward the optimization scheme about rearview mirror base model and proceeds preliminary analysis and discussion about the noise reduction method on non-smooth surface. |
