Research On The Aerodynamic Noise And Passive Control Of Flow Field Around A-pillar And Side-view Mirror

Wind noise generated by a speeding car affects the comfort in the car seriously, whichmakes noise reduction an important issue. According to previous studies, A-pillar and sideview mirror are main sources of wind noise. Amount of work have been done to the researchof side view mirrors. However, less attention was paid on A-pillar, where the mechanism ofnoise generating and methods of noise reduction are still under study. Thus, this thesis aimsat the wind noise generated by A-pillar. Bionic structures were applied to A-pillar andnumerical methods were used to study the effect on flow field and wind noise.In the numerical simulations, k-ω SST turbulence model was used in steady calculation.The flow field and pressure contours were obtained. Large eddy simulation(LES) was usedin transient calculation. The fluctuating pressure on the monitoring points were obtained andthen the sound pressure level was computed.Firstly, the simplified car model was built and simulated by numerical methods.Characteristics of flow field around A-pillar was analyzed to understand the noise sourcesand mechanism. A bionic serration structure was added to A-pillar to get three kinds ofmodels: the original model, the reference model, the bionic model. These three kinds ofmodels were simulated respectively. The effect on the flow field behind A-pillar was studiedby analyzing the velocity field and pressure field. Secondly, giving aesthetics andpracticability, a modified serration structure was added to the A-pillar of the full vehiclemodel. The flow field and sound field of both original and bionic model were simulated andthen compared. The results suggest that the bionic serration structures improve the flow fieldeffectively and bring noise reduction to a degree. The largest drop of the sound pressure atthe monitoring points is more than10dB. Finally, orthogonal experiment design was adoptedto further investigate the effect law of shape and size of serrations on the noise reduction under different flow speed. The primary and secondary factors were identified and theoptimal combination was found.Conclusively, the bionic serrations applied to A-pillar have a positive effect on the flowfield and reduce the wind noise to a degree.