Numerical simulation on the impact of the bionic structure on aerodynamic noises of sidewindow regions in vehicles

Abstract

The paper adopted a bionic hemispherical convex structure in the A pillar-rear view mirror regions according to actual requirements. Furthermore, impacts of the bionic structure on aerodynamic characteristics and noises in the region were studied. Friction resistance of airflows was greatly reduced, fluctuations and pulsation pressures of flow fields were also reduced, and characteristics of flow fields and sound fields were improved. The computational results were finally verified by the experimental test. Firstly, the aerodynamic lift force coefficient and drag force coefficient of the bionic model were computed, and they were obviously lower than those of the original model. The adhesive force between tires and ground during vehicle running was increased, and the danger degree of "waving" of high-speed vehicle running was weakened. In this way, stability of vehicle running could be improved. Secondly, flow fields of the bionic model were computed. Compared with the original model, an obvious vortex was behind the original model, while no vortexes were behind the bionic model. Therefore, convex structures of the bionic model had obvious impacts on flow fields behind the rear view mirror. Airflow separation situations were obvious improved at wheels, windshield and rear side windows of the bionic model. Due to blocking of convex structures of the A pillar and rear view mirror in the bionic model, airflows was hindered and obvious dragging phenomena were formed. Therefore, flow fields in the side window regions could be improved greatly. In addition, the flow field scope under the rear view mirror in the bionic model was also decreased. Ringed vortex structures appeared behind the rear view mirror in the bionic model. The ringed vortex structures were closely interlaced and then extended together backwards. Vortexes behind the rear view mirror in the original model were chaotic, where most of them were attached on the surface of side windows. In the original model, turbulent flows with certain strength were on the right upper corner of the side window region. In the bionic model, no turbulent flows were in the same regions. This result indicated that through using the bionic convex structures, airflows flowing through side windows could be combed and could move backwards towards upper and lower edges of the side windows. It could be predicted that pulsation pressures on the side window surface would surely decrease. Therefore, aerodynamic noises caused by pulsation pressures in side window regions would also be improved correspondingly. Especially in regions behind A pillar-rear view mirrors, the maximum noise reduction amplitude reached about 20 dB.

Experimental Study on a Generic Side-View Mirror with Slotted Cylindrical Foot

“…Figure 2 shows the definitions of the mirror baseline and the other three models with different slot sizes. For the slotted mirrors, the airflow rate Sr is defined as the ratio of the slotted area to the windward cross-sectional area of the mirror foot and is described as The flow blockage ratio of the side-view mirror is 4.7%, meeting the experimental requirement of less than 5% (Liu et al 2018).…”

“…Automobile noise is composed mainly of engine noise, tire noise, and wind (aerodynamic) noise (Li et al 2011). When a car runs at high speeds, aerodynamic noise becomes the dominant noise of the vehicle (Liu et al 2018), in which the side-view mirror is one of the aerodynamic noise sources Levy and Brancher 2013;Murad et al 2013;Oettle and Sims-Williams 2017). The high-speed airflow separation from the mirror surface leads to severe pressure fluctuations on the side window (Zheng and Li 2012;He et al 2020), which plays a significant role in the vehicle interior noise (Wang et al 2010;Yang et al 2014;Yao et al 2018).…”

Structural Design and Parameter Optimization of Bionic Exhaust Tailpipe of Tractors

“…Li et al [27] used the LES method and FW-H equation to numerically simulate the flow field and noise research so that the unsteady pressure fluctuations on the surface of a bionic blade constructed with long-eared owl wing models were suppressed, and the aerodynamic noise was reduced. Liu et al simulated the influence of aerodynamic noise of vehicle side windows with bionic structures [28]; Dean et al reviewed the research of shark-skin surfaces for turbulent drag reduction and [29]; Shi et al reduced the radiated aerodynamic noise of a cylindrical tube structure by mimicking the jagged structure of the leading edge of a long-eared owl wing [30].…”