Effects of Installation Environment on Flow around Rear View Mirror

Yuan, Haidong; Yang, Zhigang; Li, Qiliang

doi:10.4271/2017-01-1517

Cited by 10 publications

(7 citation statements)

References 21 publications

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“…Noises caused by running airflows include: noises caused when air enters a vehicle through door windows; aerodynamic noises caused by vortexes which are generated when airflows get contact with the body, as well as vibration noises caused by friction between air and the body; vibration noises caused by convex structures on the body. From the perspective of aerodynamics, a rear view mirror outside a vehicle is a bluff body with a large structural size, which is exposed in high-speed airflows; the flow field in the wake flow region behind the rear view mirror has a complicated structure, and resistance brought by it is 2 %-5 % of air resistance of the complete vehicle; turbulent flow structures will directly affect pressure distribution in lateral window region; the shape of rear view mirrors obviously affects aerodynamic noises of the vehicle [5][6][7][8]. Therefore, it is very necessary to study flow fields and aerodynamic noises around the rear view mirror.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation and experimental test on aerodynamic noises of the bionic rear view mirror in vehicles

Wan¹,

Ma²

2017

J. vibroeng.

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At present, there are some researches focusing on optimization of aerodynamic noises on rear view mirrors, but researches on bionic noise reduction of rear view mirrors are rarely reported. Therefore, with an original rear view mirror as the basic model, the paper applied a head convex hull of a dung beetle to the original rear view mirror cover to obtain a bionic rear view mirror, then conducted numerical computation for aerodynamic noises of the bionic rear view mirror and compared the computational results with the original model. Finally, in order to verify correctness of computational results of aerodynamic noises of the rear view mirror, wind tunnel test was conducted on the rear view mirror. Experimental and numerical simulation results were highly consistent in the whole frequency band, so the wind tunnel test could be replaced by numerical simulation. Only one obvious vortex was behind the bionic rear view mirror, but two obvious vortexes with the opposite rotation directions were behind the original rear view mirror. The bionic rear view mirror did not present vortexes near the lateral window, so impacts of vortexes on noises in the vehicle could be eliminated effectively. Pressure difference in front of and behind the bionic view mirror was smaller than the pressure difference in front of and behind the original rear view mirror. Pressure resistance caused by the convex structure outside the rear view mirror was reduced, so noise reduction could be promoted. The convex structure mainly affected the aerodynamic noise in mid-high frequency regions. Compared with the original rear view mirror, noise reduction effects of the bionic rear view mirror were obvious, where the noise reduction amplitude reached 10dB. Noise source size and intensity of the bionic rear view mirror were reduced obviously.

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Section: Introductionmentioning

confidence: 99%

Numerical investigation and experimental test on aerodynamic noises of the bionic rear view mirror in vehicles

Wan¹,

Ma²

2017

J. vibroeng.

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“…33,34 We also successfully performed IDDES on prediction of the unsteady flow behind the rear-view mirror of the DrivAer model to consider the effects of installation environment on flow around rear view mirror. 35…”

Section: Methodsmentioning

confidence: 99%

Reduced-order modeling of pressure excitation on automotive front side window

Yuan

Yang

Xia

et al. 2018

Proceedings of the Institution of Mechanical Engineers, Part D:

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The pressure excitation on automotive front side window acts as an indicator of the unsteady flow and wind noise in the front side window region. The complex unsteady flow in this area generates a wider range of vortex structures resulting in the nonhomogeneous and complex pressure excitation on side glass. The description of the pressure field, which can consider the nonhomogeneous in the exact space, is needed to better solve the vibration and noise problems. The turbulent pressure excitation on side window was achieved by the incompressible improved delayed detached-eddy simulation, which is validated by the wind tunnel experiment. The reduced-order modeling methods, including the proper orthogonal decomposition and the dynamic mode decomposition, were employed to describe the pressure excitation on side glass. The dynamic mode decomposition modes separate the pressure excitation into three parts just corresponding to three main flow structures in the front side window region: the vortex shedding of the side mirror (lower frequency range), pedestal vortex (middle frequency range), and A-pillar vortex (higher frequency range). The turbulent pressure excitation generated by the vortex shedding of the side mirror contributes most of the vibration of the side glass and then the wind noise in the cabin in the low-frequency range. (The characteristic frequency is around 60 Hz, which is close to both the measured coincidence frequency and the theoretical derivation value.) The dynamic mode decomposition analysis with the unique and exact frequency for each mode, considering the nonhomogeneous of the pressure excitation, has potential to understand and solve the vibration and wind noise problems.

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“…Through investigations done on passenger car, the noise caused by the rearview mirror has been investigated at a certain extent. 5–9 Because of the difference mentioned above, the conclusion drawn from passenger car cannot be extended to coach. As a result, how to understand the aerodynamic noise of rearview mirror area of coaches is the focus of this study.…”

Section: Introductionmentioning

confidence: 99%

Numerical and experimental research on flow and aerodynamic noise characteristics of coach

Chang

Yang

2020

Proceedings of the Institution of Mechanical Engineers, Part D:

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The researches on flow and aerodynamic noise characteristics of coaches are urgently needed to improve with the rapid development of new energy coaches. In this paper, tests in model wind tunnel and numerical calculations were carried out to study the phenomenon of flow and aero-noise on 1:25 scale model coach. Based on large eddy simulation (LES) and detached eddy simulation (DES), reliable numerical calculation method of flow and aero-noise on coach was established and verified. It is found that the maximum difference on turbulent pressure between test and LES is less than 10 dB(A) while that of DES is about 20 dB(A). Due to the results got from 1:25 scale model, the W_LES_HOA model is used to obtain the flow field and sound field information outside the coach. To find out the different propagation characteristics of turbulent pressure pulsation and acoustic pressure, proper orthogonal decomposition (POD) and band-pass filter analysis are used for further analysis. For rearview mirror, the energy of first mode is 6.1%, and only the first nine modes have an energy for more than 3.0%. By the reconstruction of first four modes, it can be seen that the complicated transverse vortex shedding couples with A pillar vortex and reaches the body surface. However, the coupling of turbulent pressure can only be seen clearly under low frequency around 250 Hz while the coupling of acoustic pressure can be seen under 750 Hz. Meanwhile, with the analysis of low frequency round 250 Hz and 500 Hz, the change of flow field generated by airflow impingement on the windward surface and A pillar makes the front of the coach becomes the main sources of aerodynamic sound sources.

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Effects of Installation Environment on Flow around Rear View Mirror

Cited by 10 publications

References 21 publications

Numerical investigation and experimental test on aerodynamic noises of the bionic rear view mirror in vehicles

Numerical investigation and experimental test on aerodynamic noises of the bionic rear view mirror in vehicles

Reduced-order modeling of pressure excitation on automotive front side window

Numerical and experimental research on flow and aerodynamic noise characteristics of coach

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