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Research Papers: Flows in Complex Systems

Detached-Eddy Simulation of Ground Effect on the Wake of a High-Speed Train

[+] Author and Article Information
Chao Xia

Shanghai Key Lab of Vehicle Aerodynamics and
Vehicle Thermal Management Systems;
Shanghai Automotive Wind Tunnel Center,
Tongji University,
No. 4800, Cao’an Road,
Shanghai 201804, China
e-mail: 1210076@tongji.edu.cn

Xizhuang Shan

Shanghai Key Lab of Vehicle Aerodynamics and
Vehicle Thermal Management Systems;
Shanghai Automotive Wind Tunnel Center,
Tongji University,
No. 4800, Cao’an Road,
Shanghai 201804, China
e-mail: xizhuang.shan@sawtc.com

Zhigang Yang

Shanghai Key Lab of Vehicle Aerodynamics and
Vehicle Thermal Management Systems;
Shanghai Automotive Wind Tunnel Center,
Tongji University,
No.4800, Cao’an Road,
Shanghai 201804, China
e-mail: zhigang.yang@sawtc.com

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received January 3, 2016; final manuscript received January 10, 2017; published online March 16, 2017. Assoc. Editor: Elias Balaras.

J. Fluids Eng 139(5), 051101 (Mar 16, 2017) (12 pages) Paper No: FE-16-1004; doi: 10.1115/1.4035804 History: Received January 03, 2016; Revised January 10, 2017

The influence of ground effect on the wake of a high-speed train (HST) is investigated by an improved delayed detached-eddy simulation. Aerodynamic forces, the time-averaged and instantaneous flow structure of the wake are explored for both the stationary ground and the moving ground. It shows that the lift force of the trailing car is overestimated, and the fluctuation of the lift and side force is much greater under the stationary ground, especially for the side force. The coexistence of multiscale vortex structures can be observed in the wake along with vortex stretching and pairing. Furthermore, the out-of-phase vortex shedding and oscillation of the longitudinal vortex pair in the wake are identified for both ground configurations. However, the dominant Strouhal number of the vortex shedding for the stationary and moving ground is 0.196 and 0.111, respectively, due to the different vorticity accumulation beneath the train. A conceptual model is proposed to interpret the mechanism of the interaction between the longitudinal vortex pair and the ground. Under the stationary ground, the vortex pair embedded in a turbulent boundary layer causes more rapid diffusion of the vorticity, leading to more intensive oscillation of the longitudinal vortex pair.

Copyright © 2017 by ASME
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References

Figures

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Fig. 1

A 1/8 scale high-speed train model

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Fig. 2

Computational domain and boundary conditions

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Fig. 3

Fine grids around the HST

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Fig. 4

Grid sensitivity of time-averaged velocity for coarse, medium and fine grids at x = 1W, 2W, 3W, 4W, 5W; y=–1W1W and z = 0.11H: (a) streamwise velocity and (b) spanwise velocity

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Fig. 5

Time-averaged force coefficients of the trailing car comparison between IDDES and testing

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Fig. 6

Static pressure of the longitudinal symmetry line on the roof: (a) the head train and (b) the tail train

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Fig. 7

Time history of the force coefficients of the trailing car: (a) lift force coefficient and (b) side force coefficient

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Fig. 8

Auto-power spectral of the force coefficients of the trailing car: (a) lift force coefficient and (b) side force coefficient

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Fig. 9

Time-averaged vorticity on the different horizontal plane sections (from top to down: z = 0.11H, 0.28H, and 0.45H, respectively): (a) stationary ground and (b) moving ground

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Fig. 10

Monitor points in the wake

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Fig. 11

Normalized auto-power spectral of the time-varying signal of velocity in the wake at x = 0W, 1W, 2W, 3W, 4W, 5W, y = 0.5W, and z = 0.28H

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Fig. 12

Phase difference at x = 4W, y= ±0.5W, z = 0.11H: (i) stationary ground and (b) moving ground

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Fig. 13

Iso-surface of P = −0.2 Pa: (a) stationary ground and (b) moving ground

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Fig. 14

Iso-surface of Q = 10,000: (a) stationary ground and (b) moving ground

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Fig. 15

Time-averaged streamwise vorticity and velocity vectors projected onto the plane sections at x = 1W, 3W and 5W (from top to down): (a) stationary ground and (b) moving ground

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Fig. 16

Instantaneous streamwise vorticity and velocity vectors projected onto the plane section at x = 4W: (a) stationary ground and (b) moving ground

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Fig. 17

The interaction of a pair of vortices with the ground

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