Project A5 Aerodynamic dynamic interactions

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Project A5 Aerodynamic / dynamic interactions

• Hassan Hemida, Chris Baker (University of
  Birmingham)
• Daniele Ongaro, Simon Iwnicki (Manchester
  Metropolitan University)

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Aim

• To come to a better understanding of the nature
  of the interaction between unsteady train
  aerodynamic forces and moments and the vehicle /
  track dynamic system

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Objectives

• To simulate numerically unsteady cross wind
  forces and moments on passenger trains
• To simulate numerically unsteady cross wind
  forces and moments on freight trains
• To incorporate these unsteady forces and moments
  into a train dynamic model (VAMPIRE)
• Through multiple runs of VAMPIRE to investigate
  the interaction between aerodynamic forces, track
  defects, different speed profiles etc

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Vehicle dynamic modellinginto Vampire
Wind Force History (t)
Flange climbing Indicator Y/Q
Vampire Dynamic Simulation
Track Design irregularities
Roll-over Indicator ?Q/Q
Running Speed
Other outputs
W/R Contact Conditions

• Integrate all aspects that affect the dynamic
  behaviour of the vehicle
• Produces time history of vehicle behaviour under
  the effect of wind in real running conditions

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Outline of presentation

• Modelling of cross winds
• Wind tunnel tests to obtain passenger train
  aerodynamic force information
• CFD trials to obtain freight train aerodynamic
  information
• Simulation of cross wind forces and moments
• Incorporation into train dynamic model
• Output from train dynamic model

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Modelling of cross wind conditions

• Simplified method simulate wind time series
  only at points and times corresponding to the
  passage of the train
• Match wind spectrum in plane of reference of
  moving train Cooper 1985
• Wind time history formed from summation of sine
  waves of variable amplitude, frequency and phase
• Wind velocity relative to train formed by vector
  addition of train speed

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Wind tunnel modelling of Class 365

• Modelling needed to obtain
• mean aerodynamic force and moment coefficients
• Aerodynamic admittances and weighting functions

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Large eddy simulation modelling of freight trains
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Large eddy simulation modelling of freight trains
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Simulation of cross wind forces and moments
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Incorporation into train dynamic model

• As stated in GM/RT2141 (Resistance of Railway
  Vehicles to Derailment and Roll-Over)
• Wheel/rail coefficient of friction of 0.32 shall
  be used.
• The simulation shall be capable of generating a
  time history of Y/Q which shall be computed using
  a sliding mean over a 2m length of track.

Vehicle Class 365 Maximum speed 100 mph Tare
weight 34 ton Wheel diameter 0.84m Wheel
profile new P8

• Vehicle model composition
• 7 Masses for a total of 38 degrees of freedom
• 6 Stiffness Elements
• 2 Bumpstop Elements
• 21 Viscous Damper
• 8 Shear Spring Elements
• 4 Airspring Elements
• 10 Bush Elements

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Results Time historyFlange climbing risk

• Nadals formula indicates that the limiting value
  of Y/Q above which derailment may occur is given
  by Y/Q (tana-m)/(1mtana)
• According to GM/RT2141 the computed Y/Q value
  shall nowhere exceed 1.2.
• Y/Q quite far from the threshold value with
  maximum speed wind of 25 ms

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Results Time historyRoll over risk
The wheel unloading is connected both with the
track design (cant deficiency or excess) and the
track irregularities. The highest DQ/Q due to the
track design is about 0.15 in the curve. The
highest DQ/Q due to the track quality is about
0.4 in straight .
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Results Time historyRoll over risk
The wheel unloading rises both in terms of mean
value and amplitude with the increase of the
cross wind speed. The normal wind condition of
10ms slightly affects DQ/Q in term of roll over
risk, while the overcoming of safety criteria
seldom appears with strong wind. The
extraordinary wind scenario shows a high complete
wheel unloading occurrence.
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Future work

• Probabalistic analysis of VAMPIRE output
• Further exploration of freight train LES results
• Optimisation of freight train shape for wind
  induced overturning