Journal of Jilin University(Engineering and Technology Edition) ›› 2020, Vol. 50 ›› Issue (5): 1635-1644.doi: 10.13229/j.cnki.jdxbgxb20190401

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Drag reduction of a square⁃back Ahmed model based on bi⁃stable wake

Zhi-gang YANG1,2,3(),Ya-jun FAN1,2,Chao XIA1,2(),Shi-jun CHU1,2,Xi-zhuang SHAN1,2   

  1. 1.School of Automotive Studies, Tongji University, Shanghai 201804, China
    2.Shanghai Automotive Wind Tunnel Center, Tongji University, Shanghai 201804, China
    3.Beijing Aeronautical Science & Technology Research Institute, Beijing 102211, China
  • Received:2019-04-26 Online:2020-09-01 Published:2020-09-16
  • Contact: Chao XIA E-mail:zhigangyang@tongji.edu.cn;chao.xia@tongji.edu.cn

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Abstract:

The wake of 1/4 scale square back Ahmed body with or without boat-tail structure was investigated at ReH=9.6×104 by pressure sensor and particle image velocimetry(PIV). The statistical analysis of the instantaneous pressure on the back shows that the wake presents a bi-stable behavior in the horizontal direction, characterized by alternating occurrence of two symmetry-breaking stable states, each can maintain a relatively long-time duration. During the two stable states, a lower pressure on the back presents a high probability, while in the switch state the pressure on the back is higher. The bi-stable behavior was also observed by instantaneous and conditional average PIV results of flow field in the horizontal plane. With boat-tail structure added at the model base, the bi-stable behavior of the wake is gradually suppressed with the increase in the boat-tail length, and the wake vortex structure tends to be symmetrical, the wake width becomes narrow, the vortex shedding strength weakens, leading to higher back pressure and lower drag coefficient.

Key words: vehicle engineering, square-back Ahmed model, bi-stable wake, boat-tail structure, particle image velocimetry(PIV)

CLC Number: 

  • U461.1

Fig.1

Experimental setup and coordinate system"

Fig.2

Boat-tail structure"

Fig.3

Cdvaries with length of boat-tail"

Fig.4

Averaging Cp of model base"

Fig.5

Instantaneous CP of two symmetrical points on back"

Fig.6

Pressure tap"

Fig.7

Phase diagram of pressure gradient"

Fig.8

Time-space diagram of horizontal back pressure distribution of boat-tail with different lengths"

Fig.9

Instantaneous vorticity field and streamline of cross section z/H=0.67 of wake"

Fig.10

Conditional mean velocity field of cross section z/H=0.67 of wake"

Fig.11

Velocity field of cross section z/H=0.67 of wake"

Fig.12

Instantaneous vorticity field and streamline of longitudinal section y/H=0 of wake"

Fig.13

Time-mean velocity field of y/H=0 plane"

1 Ahmed S R, Ramm G, Faltin G. Some salient features of the time-averaged ground vehicle wake[C]∥ SAE Technical Paper, 840300, 1984.
2 Choi H, Lee J, Park H. Aerodynamics of heavy vehicles[J]. Annual Review of Fluid Mechanics, 2014, 46(1): 441-468.
3 Khalighi B, Zhang S, Koromilas C, et al. Experimental and computational study of unsteady wake flow behind a bluff body with a drag reduction device[J]. SAE Technical Paper, 2001-01-1042.
4 Mcarthur D, Burton D, Thompson M, et al. On the near wake of a simplified heavy vehicle[J]. Journal of Fluids and Structures, 2016, 66: 293-314.
5 崔文诗, 杨志刚, 王国俊, 等. 不同后倾角三维车辆的尾迹非定常流动分析[J]. 吉林大学学报: 工学版, 2017, 47(3): 717-724.
Cui Wen-shi, Yang Zhi-gang, Wang Guo-jun, et al. Unsteady flow analysis for wakes of three-dimensional vehicles with different rear slant angles[J]. Journal of Jilin University(Engineering and Technology Edition), 2017, 47(3): 717-724.
6 Grandemange M, Gohlke M, Cadot O. Turbulent wake past a three-dimensional blunt body. Part 1: global modes and bi-stability[J]. Journal of Fluid Mechanics, 2013, 722: 51-84.
7 Grandemange M, Cadot O, Gohlke M. Reflectional symmetry breaking of the separated flow over three-dimensional bluff bodies[J]. Physical Review E, 2012, 86(3): 035302.
8 Grandemange M, Gohlke M, Cadot O. Bi-stability in the turbulent wake past parallelepiped bodies with various aspect ratios and wall effects[J]. Physics of Fluids, 2013, 25(9): 095103.
9 Wang H F, Zhou Y. The finite-length square cylinder near wake[J]. Journal of Fluid Mechanics, 2009, 638: 453-490.
10 王汉封, 徐胜金. 用POD方法研究有限长正方形棱柱尾流的双稳态现象[J]. 空气动力学学报, 2014, 32(6): 827-833.
Wang Han-feng, Xu Sheng-jin. On the bistable phenomenon of a finite length square cylinder wake with POD method[J]. ACTA Aerodynamica Sinica, 2014, 32(6): 827-833.
11 王汉封, 徐萌霞. 有限长正方形棱柱绕流的双稳态现象[J]. 力学与实践, 2013, 35(3): 46-50.
Wang Han-feng, Xu Meng-xia. Bistable phenomenon of the flow around a finite-length square prism[J]. Mechanics in Engineering, 2013, 35(3): 46-50.
12 Gilliéron P, Kourta A. Aerodynamic drag reduction by vertical splitter plates[J]. Experiments in Fluids, 2010, 48(1): 1-16.
13 王勋年, 李士伟, 陈立. 采用尾部隔板降低类客车体阻力的研究[J]. 实验流体力学, 2011, 25(2): 58-62.
Wang Xun-nian, Li Shi-wei, Chen Li. Investigation on reducing drag of the bus-like body using tail clapboards[J]. Journal of Experiments in Fluid Mechanics, 2011, 25(2): 58-62.
14 李士伟. 类客车体气动特性及减阻措施的试验研究和数值模拟[D]. 绵阳: 中国空气动力研究与发展中心, 2010.
Li Shi-wei. Experimental study and numericial simulation of the aerodynamics performance and drag reduction measurement for the bus-like body[D]. Mianyang: China Aerodynamics Research and Development Center, 2010.
15 Evrard A, Cadot O, Herbert V, et al. Fluid force and symmetry breaking modes of a 3D bluff body with a base cavity[J]. Journal of Fluids and Structures, 2016, 61: 99-114.
16 Verzicco R, Fatica M, Iaccarino G, et al. Large eddy simulation of a road vehicle with drag-reduction devices[J]. AIAA Journal, 2002, 40(12): 2447-2455.
17 Khalighi B, Chen K H, Iaccarino G. Unsteady aerodynamic flow investigation around a simplified square-back road vehicle with drag reduction devices[J]. Journal of Fluids Engineering, 2012, 134(6): 061101.
18 Khalighi B, Balkanyi S R, Bernal L P. Experimental investigation of aerodynamic flow over a bluff body in ground proximity with drag reduction devices[J]. International Journal of Aerodynamics, 2013, 3(4): 217-233.
19 张英朝, 杜冠茂, 田思, 等. 35°Ahmed模型气动射流减阻主动控制[J]. 吉林大学学报: 工学版, 2019, 49(2): 351-358.
Zhang Ying-chao, Du Guan-mao, Tian Si, et al. Active flow control of 35° Ahmed model to reduce aerodynamic drag with steady jet[J]. Journal of Jilin University(Engineering and Technology Edition), 2019, 49(2): 351-358.
20 Roumeas M, Gilliéron P, Kourta A. Analysis and control of the near-wake flow over a square-back geometry[J]. Computers & Fluids, 2009, 38(1): 60-70.
21 Wassen E, Eichinger S, Thiele F. Simulation of active drag reduction for a square-back vehicle[J]. Notes on Numerical Fluid Mechanics & Multidisciplinary Design, 2010(108): 241-255.
22 Littlewood R P, Passmore M A. Aerodynamic drag reduction of a simplified squareback vehicle using steady blowing[J]. Experiments in Fluids, 2012, 53(2): 519-529.
23 Grandemange M, Gohlke M, Cadot O. Turbulent wake past a three-dimensional blunt body. Part 2: experimental sensitivity analysis[J]. Journal of Fluid Mechanics, 2014, 752: 439-461.
24 Evstafyeva O, Morgans A S, Dalla L L. Simulation and feedback control of the Ahmed body flow exhibiting symmetry breaking behaviour[J]. Journal of Fluid Mechanics, 2017, 817: 2-12.
25 Brackston R D, García de la Cruz J M, Wynn A, et al. Stochastic modelling and feedback control of bistability in a turbulent bluff body wake[J]. Journal of Fluid Mechanics, 2016, 802: 726-749.
26 Volpe R, Devinant P, Kourta A. Experimental characterization of the unsteady natural wake of the fullscale square back Ahmed body: flow bistability and spectral analysis[J]. Experiments in Fluids, 2015, 56(5): 1-22.
27 Khalighi B, Chen K, Iaccarino G. Unsteady aerodynamic flow investigation around a simplified square-back road vehicle with drag reduction devices[J]. Journal of Fluids Engineering, 2012, 134(6): 061101.
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