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Aerodynamik
Astrid Herbst (Bombardier), Tomas Muld & Gunilla Efraimsson ( KTH)
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2
Future demands Higher speeds and high
capacity
Wide body trains with max speed > 250 km/h
Aerodynamic challenges specific for wide body trains:
head pressure pulse & slipstream
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3
Slipstream
Safety issue for passengers on platform and trackside workers
Measures on operation & train design
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More value for environment and performance:
Aerodynamic optimisation
Reduction of drag saves energy and traction power
Drag and Cross-Wind Optimisation
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More value for environment and performance:
Aerodynamic optimisation
Parameterized model
defines the variables and
boundary conditions
Computer optimisation by
using the parameterizedmodel
Goal function is reduce
drag while keeping the
cross wind safety
chamfering
tangent between
nose and car body
upper part
of the nose tip
lower part
of the nose tip
starting section
of the nose
height and length
of the nose
size of the bogie fairing
spoiler geometrylateral tangent
at the nose tip
upper curvature
of the carbodyupper curvature
of the nose tip
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Pareto front
Design Space
Lo
wdrag
Increasing stability
Pareto front
Design Space
Lo
wdrag
Lo
wdrag
Increasing stability
More value for environment and performance:
Aerodynamic optimization
Thousands of virtual wind tunnel
tests in the computer used to find
the very best shape
Main result shows 20 30 %
lower drag and 10 15 % lowerenergy consumption
Installed power can be reduced
with lower cost
Lower energy cost for operators
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Slipstream Test Setup
Measurements with fast 3D-ultrasonic anemometers (USA)
Train speed and positions measured with light switch
Light switch mounted to detect single rail passages
Vs
ters
Enkp
ing
60 m CarCatenary Pole 1
Road
20 m 20 m 6 m 5 m
LS 1 LS 2
30.58 m
Catenary Pole 2
T-junction
9m
13m
Reference
Pressure
9.42 m
Up Track
Down Track
Vsters Enkping
USA 1 USA 2 HPP USA 3
Legend
USA : Ultra Sonic AnemometerHPP : Head Pressure Pulse Rake
LS : Light Switch
60 m
CarCatenary Pole 1
Road
20 m 20 m 6 m 5 m
LS 1 LS 2
30.58 m
Catenary Pole 2
T-junction
9m
13m
Reference
Pressure
9.42 m
Up Track
Down Track
Vsters Enkping
USA 1 USA 2 HPP USA 3
Legend
USA : Ultra Sonic AnemometerHPP : Head Pressure Pulse Rake
LS : Light Switch
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Measurement results
-5
-2,5
0
2,5
5
7,5
10
-50 0 50 100 150 200
x [m]
u Wind[m/s]
-0,072
-0,036
0
0,036
0,072
0,108
0,144
cu,Wind[]
Ensemble average overall
Ensemble average Skirt leading
Ensemble average Skirt trailing
Maximum
Axles
Intercar
Gap
Head
Passage
Impact of
Bogie Skirts
Tail Passage
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Numericalsimulations of slipstream
performed at KTH
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Slipstream
Slipstream= Inducedvelocity by the train
Regions
1) Head pressure pulse
2) Boundary Layer(Freight Trains)
3) Near wake(High-speed Train)
4) Far Wake
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Train models
Aerodynamic Train Model (ATM) Regina (CRH1)
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Decomposition models
=
+= + +
Mode 1 Mode 2,3 Mode 4,5 Mode 6+
Full
flow
field
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Connection between modes
Phase portrait
Spiraling circles when the modes are connected
Random patterns when not
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Example of flow structure
Isosurface of
V-velocity
Mode 1+4+5
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Decomposition models
Challenges
- Long computation times
- Accurate results
Understanding of dominant energetic structures
Two methods
- Proper Orthogonal Decomposition (POD)
- Dynamic Mode Decomposition (DMD)
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Comparing with Experiments
CFD
by KTH
Water
Towing Tank
from
Bombardier
performed atDLR
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Grid study
Small cells
Medium cells
Large cells
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TSI-measurements3 m
1.2 m
Velocity for an observer
standing on platform
0.07s (1s) time
averaged velocity
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Achievements
Showed that POD and DMD can be used with Detached EddySimulation flow fields.
Identified dominant flow structures for two different trains.
Used advanced models on applied geometries.
Cooperation and exchange of knowledge with Bombardier.
Fundament for efficient prediction to connect train geometryand slipstream.
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Publications Muld, T.W, Analysis of Flow Structures in Wake Flows for Train Aerodynamics, Licentiate Thesis in Mechanics, KTH
Stockholm, ISBN 978-91-7415-651-5, 2010
Muld T.W, Efraimsson G., Henningson D. S, Flow structures around a high-speed train extracted using ProperOrthogonal Decomposition and Dynamic Mode Decomposition, Computer & Fluids, DOI:10.1016/j.compfluid.2011.12.012 , 2012
Muld T.W, Efraimsson G., Henningson D. S, Mode decomposition on surface mounted cube, Flow, Turbulence andCombustion, DOI: 10.1007/s10494-011-9355-y, 2011
Muld T.W, Efraimsson G., Henningson D. S, Mode Decomposition of Flow Structures in the wake of Two High-SpeedTrains, The First International Conference on Railway Technology: Research, Development and Maintaince, April 16-18,Gran Canaria, Spain, 2012
Muld T. W., Efraimsson G., Henningson D. S., Herbst A. H. and Orellano A., Analysis of Flow Structures in the Wakeof a High-Speed Train, Aerodynamics of Heavy Vehicles III: Trucks, Buses and Trains, September 12-17, 2010,Potsdam, Germany
Muld T. W., Efraimsson G., Henningson D. S., Herbst A. H., Orellano A., Detached Eddy Simulation and Validation onthe Aerodynamic Train Model, Euromech Colloquim 509, Vehicle Aerodynamics, Berlin Germany, March 24-25 2009
Muld T. W., Efraimsson G., Henningson D. S., Proper Orthogonal Decomposition of Flow Structures around a Surface-mounted Cube Computed with Detached-Eddy Simulation, SAE paper 09B-0170, 200915