Study On Wind Buffeting Noise Mechanism And Control For Side-windows

With the sustained development of Chinese automobile industry and national economy,consumers will pay more attention to the riding comfort and driving safety of cars when they purchase automobiles.Vehicle wind noise has always been one of the major comfort issues which consumers complaint about.In addition to increasing the driving resistance and the fuel consumption,the buffeting noise induced by the open-window driving condition of vehicles seriously affects the user experience,which can easily lead to fatigue driving,and the low-speed airflow will induce the structural resonance radiation noise.The unsteady loads caused by the low-speed airflow will excite the vehicle body vibration which leads to the occurrence of unsafe factors.The side window buffeting issue however still exists for almost all passenger cars today.Even though manufacturers continuously strive for solutions,so far no practical and implementable countermeasure has been found.Therefore,it is of great practical significance to study the formation mechanism of side window buffeting noise of vehicles and explore the influencing factors and effective engineering control measures of the side window buffeting.First,the simple cavity model of a car body is taken as the research object.The accuracy of the simulation is verified by the comparison between the theoretical calculations of the simple cavity natural frequency and the simulation results.The formation mechanism of buffeting is studied from the transient flow characteristics of the internal and external flow fields and the spectrum analysis.The results show that the feedback mechanism caused by vortex periodically shedding is the main reason for the strong pressure oscillations in the cavity.The feedback mechanism is the basis for the occurrence of the buffeting noise,and the Helmholtz resonance significantly enhances the buffeting noise At the same time,the research on the flow field characteristics and buffeting noise in the side windows of actual vehicles is carried out.The results show that the flow in the side window can be divided into three parts: the Karman vortex street generated by the rearview mirror,the reattached flow and the spiral vortex.The feedback mechanism of the periodic shedding of the free shear layer vortex structure is the basis for the occurrence of buffeting noise in real vehicles.Then,the influence factors of buffeting noise of the real car are studied.According to different mirror installations and the model without rearview mirrors,the flow characteristics and side window buffeting noise are analyzed,and the influence mechanism of the rear-view mirror on the buffeting noise of the side window is studied.In addition,the influencing factors of buffeting noise are summarized.The results show that under the simulation speed of 80 km / h,the front side window buffeting intensity of the door mounted mirror is higher than that without rear-view mirror,and the buffeting of the glass mounted mirror is the lowest level.Comparing with the flow field characteristics of the side windows of the door mounted mirrors and the glass mounted mirror,it is found that the rearview mirror wake vortices affect the free shear layer as a whole deviate from the side window area,and make the free shear layer partially deflected,thereby destroying the development of the free shear layer and its vortex structure,which has obvious inhibition effect on buffeting noise.The position of the wake vortex in the rearview mirror determines the influence level.The different intensity spiral vortices formed on the A-pillars of three different models also have a different inhibitory effect on the buffeting noise.For the model without rear-view mirror,because of the lack of acceleration of the airflow between the rearview mirror and the side window,the vortex strength of the free-shear layer generated by the free-shear layer in the region is weakened,the lack of the wake vortex impact on the free shear layer and its vortex.These are the main factors affecting the front-window buffeting of the non-rear-view mirror model.For the rear side window buffeting noise,the rear window of the model without rear-view mirror has the strongest buffeting noise,followed by the door mounted mirror model,and the glass mounted mirror has the weakest buffeting noise.the rear view mirror also has an influence on the rear window buffeting noise.However,the influence on the velocity of the rear window area is small.Based on the analysis of the buffeting noise of the front and rear windows of the three models,it was found that the buffeting noise of the rear window is higher than the buffeting noise of the front window.At the same time,the flow characteristics and buffeting under different side-window opening conditions are studied.The analysis shows that the export of the air flow is the reason for the reduction of buffeting noise.In the last part,based on the study mentioned above,it is effective to reduce the side-window buffeting by influencing or damaging the feedback cycle.Based on this idea,six measures to control side-window buffeting noise are proposed.The results show that all methods have effect on reducing side-window buffeting,and then the mechanism of each method is analyzed.