the aerodynamics of high speed train with the influence of crosswind
TRANSCRIPT
The Aerodynamics of High-Speed Train Especially With the Influence of Crosswind
Student: ZHAO PeiboDecember 1, 2014
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CONTENT• Introduction• The basic theory of fluid dynamics• The aerodynamics of isolated high-speed
trains without crosswind • The aerodynamics of high-speed trains with
the influence of crosswind• Conclusion• References12/01/2014
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INTRODUCTION12/01/2014
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The development of high-speed train
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The accidents relates to aerodynamics
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THE BASIC THEORY OF FLUID DYNAMICS
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Computational Fluid Dynamics(CFD)
Computational fluid dynamics
(CFD)
Pure Theory
The role of CFD in engineering predictions has become so strong that today it can be viewed as a new “third dimension” in fluid dynamics, the other two dimensions being the classical cases of pure experiments and pure theory.[1]
Fig. 1 Relationship between pure theory and pure experiment.
[1]John F. Wendt, Computational Fluid Dynamics: An Introduction
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Four Types of Simulation
Direct Numerical Simulation (DNS)
Reynolds-averaged Navier-Stokes (RANS)
Large Eddy Simulation (LES)
Detached Eddy Simulation (DES)
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No particular hypothesis, determine the N-S Equation directly
The most accurate method to simulate the flow
DNS could be applied to ranges of turbulence in different
length scale
Cost large amount of time and money
Usually be utilized to the relatively low Re number
Direct Numerical Simulation (DNS)1
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Utilize the N-S equation
Use relatively large grid of meshes to discrete the flow
Introduce the Reynold stress because the equation is not
closure
Usually applied to the practical issues not the physical
characteristics of the turbulence itself
Reynolds-averaged Navier-Stokes (RANS)2
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The accuracy is between DNS and RANS
Only simulate large eddy and reflect the influence of small
eddy by subgrids
Since the shear effect, LES is relatively rougher in near
solid boundary regions
Large Eddy Simulation (LES)3
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Detached Eddy Simulation (DES)
RANS
LES
DESRegions near the solid boundary
Regions far away from the solid boundary
Utilize the single turbulence simulation by three-dimensional
unsteady numerical computational method
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Types of experiments
Experiment
Full-scale
Towing tank test
Wind tunnel test
Dynamic model test
Test truck
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The comparison between full-scale test and sub-scale test
Full-scale Test
Advantages:• A train could be attached by a
dynamometer car to record the six aerodynamic components of the different parts of the high-speed train
• The result is close to the realistic condition
Drawbacks:• High expense• Complicated meteorological
conditions since the ambient wind condition
Sub-scale Test
Advantage:• The flow can be carefully
controlled• Relatively cheaper than full-scale
testDrawbacks:• Not easy to find the proper scale
ratio and proper material to make models
• Elliptic smaller-scale items of the simplified train model affect the accuracy
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The geometry model of high-speed train and the rail
Head car
Tail car
Middle car
The most satisfactory method by far is to use a moving tunnel ground in the form of a belt.
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The aerodynamic components
FD: Drag forceFL: Lift forceFS: Side force
MR: Rolling momentMY: Yawing momentMP: Pitching moment
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THE AERODYNAMICS OF ISOLATED HIGH-SPEED TRAINS WITHIOUT CROSSWIND
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An innovative test by British Rail Research
The ratio of test facility is 1/25 th-scale and the track is designed as 136m. The model is connected to an acceleration carriage, and propelled by rubber launchers. The train will stop at the time when they reach the end of the track by a hook engages a cable connected to a piston in a cylinder for braking.
Moving model test facility built by British Rail Research
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The measured and calculated result of the pressure distribution
Measured and calculated pressure distributions on a train nose model. (From Mackrodt et al 1980.)12/01/2014
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THE AERODYNAMIC OF HIGH-SPEED TRAIN MOVING THROUGH
CROSSWINDS12/01/2014
The investigation under different boundary condition
Schematic view of the experimental setup and the reference coordinate system
Schematic view from above of the experimental setup12/01/2014
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The scenario of the experiment I
The points on the train body where the pressure is measured during the experiment
There are 38 points to record the pressure at the front, middle and the end of the cuboid
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The scenario of the experiment II
Illustration of the crosswind scenario
Crosswind velocity profile
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The pressure distribution
The pressure distribution of wind side of experiment data, LES moving and LES stationary
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The result of aerodynamic components
(a) Side force coefficient Cs, during passage of wind tunnel nozzle. (b) Lift force coefficient Cl, during passage of wind tunnel nozzle. The extension of the wind tunnel nozzle is indicated with dashed lines.
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The investigation of different speed of crosswind
(a) the result of side force with the variation of crosswind speed (b) the result of lift force with the variation of crosswind speed
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The various results of aerodynamic components in the computational simulation when the high-speed train operating at the speed of 360 km/h
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The investigation of different speed of crosswind
(a) the result of rolling moment with the variation of crosswind speed (b) the result of yawing moment with the variation of crosswind speed
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CONCLUSION
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There are six aerodynamic components and each of them will impact the high-speed train.
The variation tendency of aerodynamic components with the increasing of wind speed is not the same in different range of speed.
The computational simulation of both RANS and LES perform a great agreement with the experimental data.
The result of aerodynamic force and moment coefficients show the differences in dynamic and static boundary condition. The results of the investigation indicate that the overshoot in the dynamics case of approximately 30% as compared to the steady condition, which prove that the necessarily of researching the dynamic condition.
The lift force, the side force, the rolling moment, and the yawing moment will increase with the rise of crosswind speed. However, the drag force and the pitching moment will increase when the speed of crosswind is less than 15m/s, and decline after that.
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[1] Joseph A Schetz, Aerodynamic of High-speed trains, Annu. Rev. Fluid Mech 2001. 33:371-414.[2] Sinisa Krajnovic, Per Ringqvist,Koji Nakade, Branislav Basara, Large eddy simulation of the flow around a simplified
train moving through a crosswind flow, Journal of Wind Engineering and Industrial Aerodynamics, 110(2012) 86-89.[3] Yinghui Zhao, Jijye Zhang, Tian Li, Weihua Zhang, Aerodynamic performances and vehicle dynamic response of high-
speed trains passing each other, Journal of Modern Transportation Volume 20, Number1, March 2012, Page 36-43[4] Joseph A Schetz, the aero dynamic of high-speed train, advances in mechanics, 2003, 33(3):404-423[5] Hongqi Tian, Ping Xu, Xifeng Liang, the relationship between pressure wave and operation speed when high-speed
trains passing each other, Journal of Chinese Ttail,2006, 27(6):70-71[6] R.G. Gawthrope. Train drag reduction from simple design change. International Journal of Vehicle Design, 1982, 3 (3):
263-274[7] John F. Wendt (Ed.), Computational Fluid Dynamics: An Introduction[8] David C. Wilcox Turbulence Modeling for CFD,[9] Bernard M, 1973. La soufflerie a veine longue de I’Institut Aerotechnique de SainCyrL’Ecile. Rev. Gen. Chemins Fer.
January.[10] Gaylard AP. 1993. The application of computational fluid dynamics to railway aerodynamics. Proc. World Congr. Inst.
Mech. Eng. 207:133-41[11] Howell,J.P..Everitt,K.W.,1983. Gust response of a high speed train model. In: Morel, T., Miller, J. (Eds.), Aerodynamic
of Transportation II. New York, ASME, pp. 81-89.[12] Howell, J.P., 1986, Aerodynamic performance of maglev train models to a crosswind gust. Journal of Wind
Engineering and Industrial Aerodynamics 22, 205-213[13] Fillipone. A., 2003. Unsteady gust response of road vehicles. ASME: Journal of Fluid Engineering 125, 806-812[14] Jun Wan, 2012, The aerodynamic performance and operating safety of high-speed train under the strong crosswind
and heavy rain.12/01/2014
REFERENCES
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THANK YOU
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