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Research Papers: Techniques and Procedures

Passenger Train Slipstream Characterization Using a Rotating Rail Rig

[+] Author and Article Information
N. Gil, C. Roberts

Department of Electronic, Electrical and Computer Engineering, University of Birmingham, Birmingham B15 2TT, UK

C. J. Baker, A. Quinn

Department of Civil Engineering, University of Birmingham, Birmingham B15 2TT, UK

The wavelet plots can be obtained at http://paos.colorado.edu/research/wavelets/.

J. Fluids Eng 132(6), 061401 (May 19, 2010) (11 pages) doi:10.1115/1.4001577 History: Received June 28, 2009; Revised March 08, 2010; Published May 19, 2010; Online May 19, 2010

This paper presents the results of a new experimental technique to determine the structure of train slipstreams. The highly turbulent, nonstationary nature of the slipstreams make their measurement difficult and time consuming as in order to identify the trends of behavior several passings of the train have to be made. This new technique has been developed in order to minimize considerably the measuring time. It consists of a rotating rail rig to which a 1/50 scale model of a four car high speed train is attached. Flow velocities were measured using two multihole Cobra probes, positioned close to the model sides and top. Tests were carried out at different model speeds, although if the results were suitably normalized, the effect of model speed was not significant. Velocity time histories for each configuration were obtained from ensemble averages of the results of a large number of runs (of the order of 80). From these it was possible to define velocity and turbulence intensity contours along the train, as well as the displacement thickness of the boundary layer, allowing a more detailed analysis of the flow. Also, wavelet analysis was carried out on different runs to reveal details of the unsteady flow structure around the vehicle. It is concluded that, although this methodology introduces some problems, the results obtained with this technique are in good agreement with previous model and full scale measurements.

Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Model scale results for four car ICE train from the train rig from (4) (x-axis shows time, t, normalized by vehicle velocity and train length, and y-axis shows slipstream velocity normalized by vehicle velocity. Nose of train passes at t=0 and tail of train at t=4.

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Figure 2

Model scale results for four car ICE train from the TRAIN rig (2,4) (x-axis shows equivalent full scale distance along the train, and y-axis shows the slipstream velocity u normalized by vehicle velocity V. Nose of train passes at x=0 m and tail of train passes at x=100 m. Measurements were made at half train height and at different lateral distances y from the side edge of the train.

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Figure 3

Full scale results for ICE service train-trackside measurements (from Ref. 2) (x-axis shows full scale distance along the train, and y-axis shows slipstream velocity normalized by vehicle velocity. Nose of train passes at x=0 m and tail of train passes at x=360 m Measurements were made at a height of 0.5 m above the rail and at various lateral distances y′ from the rail edge.

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Figure 4

Full scale results for ICE service train-platform measurements (from Ref. 2) (x-axis shows full scale distance along the train, and y-axis shows slipstream velocity normalized by vehicle velocity. Nose of train passes at x=0 m and tail of train passes at x=360 m. Measurements were made at a height of 1.0 m above the platform and at various lateral distances y from the platform side edge.

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Figure 5

Rotating rail rig in its original form

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Figure 6

Rig setup for aerodynamics experiments showing the wooden platform and the slot through which the train passes. The probes are located at either sides of the train. The train is formed of four wagons and its curved shape can be appreciated.

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Figure 7

Train model dimensions at rail center line (mm)

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Figure 8

Measuring points around the train. The y-axis shows train lateral distance from train side edge and the y∗ axis shows train lateral distance from train centerline. The z-axis shows vertical distance from train midheight.

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Figure 9

Set airflow. x-axis shows equivalent full scale distance along the train, and y-axis shows slipstream velocity normalized by vehicle velocity. Nose of train passes at x=0 m and tail of train passes at x=104 m. Train speed was 16.5 m/s and measurements were made at half train height, z=0, and at y=0.5 m from the outer side edge of the train.

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Figure 10

Ensemble average normalized velocities at train midheight and at different lateral distances from the train surface. Train speed=16.5 m/s. (a) Outer probe. (b) Inner probe.

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Figure 11

Normalized ensemble average slipstream velocities comparison between results obtained with the spinning rail (a) and the ones obtained in the train rig (b). In both cases a four car ICE train model was used. The spinning rail used a 1/50 scale model and the train rig a 1/25 scale model. Measurements are taken at train midheight, z=0. Again, the x-axis shows equivalent full scale distance along the train, with the tail passing at x=105 m.

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Figure 12

Normalized slipstream velocities ensemble average at z=1 m, y=0.25 m and at different train speeds

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Figure 13

Normalized velocity contour plots at different cross sections along the train (x given as equivalent full scale length along the train). The bottom axis shows equivalent full scale lateral distance and the left axis shows equivalent full scale vertical distance. (a) Train nose, x=0 m. (b) End of nose, x=3.5 m. (c) End first wagon, x=26 m. (d) End second wagon, x=52 m. (e) End third wagon, x=78 m. (f) Midfourth wagon, x=92 m. (g) Beginning of tail, x=100 m. (h) End of tail x=104 m.

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Figure 14

Normalized slipstream velocity ensemble average (black) and standard deviation (gray). Train speed=16.5 m/s. (a) Measurements taken at train midheight (z=0) and y=0.25 m from the model convex side. (b) Measurements taken at train centerline (y∗=0) and z=2 m, i.e., 0.25 m above the roof.

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Figure 15

Displacement thickness on train sides and roof. (a) End first wagon, x=26 m. (b) End second wagon, x=52 m. (c) End third wagon, x=78 m. (d) End fourth wagon, x=104 m.

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Figure 16

Turbulence intensity contours. (a) End first wagon, x=26 m. (b) End second wagon, x=52 m. (c) End third wagon, x=78 m. (d) End of fourth wagon, x=104 m.

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Figure 17

Turbulence intensity contours in the near wake region. (a) x=115 m. (b) x=125.

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Figure 18

Average wavelet power spectrum for runs at different measuring points, using the Morlet wavelet. The left axis is the corresponding Fourier period (in seconds) to the wavelet scale. The bottom axis is the equivalent full scale length along the train. The nose passes at x=0 m and the tail at x=104 m. The shaded contours represent the contribution of each level to the total power. The levels are (gray scale in which white represents the lowest level and black the highest): [9.3×−10, 1.5×−8, 3×−5, 9.5×−4, 0.0156].

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