1. Aerodynamics of High Speed Rail Tunnels
Mohammad Tabarra
Associate Director, Arup, UK
8th Dec 2010, HSR Tunnels 26

2. Aerodynamics of High Speed Rail Tunnels
Aim 1: Size high-speed tunnel cross sections for a range of train and tunnel configurations
Aim 2: Predict transient forces and moments on tunnel fixed equipment
Method: 1D finite difference formulation of Newton’s 2nd law, conservation of mass, momentum and isentropic flow
Simulation code: Tun X, run several times to find optimum tunnel area for a given train speed and tunnel length, and in double-track tunnels for different train time off-sets
Mohammad Tabarra
Associate Director, Arup, UK
8th Dec 2010, HSR Tunnels 26

3. Transient pressure simulations
200m long streamlined high speed train, 350km/h, 11 m2. Sealed with time-constant 10sec.
Pressure criteria:
TSI (<10kPa pressure change in whole event)
UIC 2005 baseline pressure comfort criteria (1kPa/1sec, 1.6kPa/4sec, 2kPa/10sec)
Sample tunnel length 1.6km
Tunnel cross-sectional area optimised to meet comfort criterion exactly without pressure relief shafts
Then run the simulation again with one pressure relief shaft
Mohammad Tabarra
Associate Director, Arup, UK
8th Dec 2010, HSR Tunnels 26

4. Pressure outside a 200m long train, 350kph in a 1.6 km tunnel
Note – height of tunnel, train, and dimensions of shaft are exaggerated in these plots for clarity.
Mohammad Tabarra
Associate Director, Arup, UK
8th Dec 2010, HSR Tunnels 26

5. Pressure outside a 200m long train, 350kph in a 1.6 km tunnel
The addition of a pressure relief shaft breaks up the pressure waves: the changes of pressure become smaller but more numerous. This graph shows pressure at a point near the rear of the train, outside the train’s sealing system, with and without pressure relief shaft
Mohammad Tabarra
Associate Director, Arup, UK
8th Dec 2010, HSR Tunnels 26

6. Pressure inside a 200m long train, 350kph in a 1.6 km tunnel
2.0kPa
10 sec
To check the effect on aural comfort, consider the pressure inside the sealed train
Without pressure relief shafts, the comfort criterion 2kPa / 10sec is met exactly
Mohammad Tabarra
Associate Director, Arup, UK
8th Dec 2010, HSR Tunnels 26

7. Pressure inside a 200m long train, 350kph in a 1.6 km tunnel
1.3kPa
10 sec
With a pressure relief shaft, the maximum pressure change inside the train in 10 sec is reduced to 1.3kPa (36% reduction).
Mohammad Tabarra
Associate Director, Arup, UK
8th Dec 2010, HSR Tunnels 26

8. This graph shows the pressure outside the train, just behind the tail.
Note the impact of pressure relief shaft on pressure extremes.
Mohammad Tabarra
Associate Director, Arup, UK
8th Dec 2010, HSR Tunnels 26

9. This graph shows what the passenger experiences, inside the sealed train.
The animation is identical to the last slide, showing pressure patterns outside the train.
Mohammad Tabarra
Associate Director, Arup, UK
8th Dec 2010, HSR Tunnels 26

10. Optimisation of tunnel area; effect of relief shafts
This graph shows the impact of pressure relief shafts on the minimum cross sectional area of the tunnel. Note the variations with tunnel length.
Example – a 1.6km tunnel needs a cross-sectional area 67.5sqm without relief shafts, or 47.5sqm with one relief shaft, to meet the comfort criteria.
Mohammad Tabarra
Associate Director, Arup, UK
8th Dec 2010, HSR Tunnels 26

11. Single & Twin-track tunnel sizing – effect of train speed
This graph shows the impact of train speed on the minimum CSA of the tunnel. Again, note the variations with tunnel length.
You can see that increasing the operational speed from 350 to 400 kph, means a 40 to 40% increase in tunnel area.
This means on existing lines with tunnels, the tunnel size shall limit your speed, even if the train can handle it.
Highlights the importance of forward infrastructure planning of HSR tunnels.
Mohammad Tabarra
Associate Director, Arup, UK
8th Dec 2010, HSR Tunnels 26

12. Mohammad Tabarra
Associate Director, Arup, UK
8th Dec 2010, HSR Tunnels 26

13. Transient Loads on tunnel fixed equipment
Maximum Forces
Maximum Moments
CTRL tunnels (HS1) cross section and the fixed equipment.
Note the instantaneous forces and moments with limited train speed 230 kph.
Expect these forces and moments to rise by speed ^ 2.
Mohammad Tabarra
Associate Director, Arup, UK
8th Dec 2010, HSR Tunnels 26

14. Conclusions & Recommendations
Pressure transients induced by a HSR train determine tunnel cross sectional area
Achieving aural comfort of passengers is the key criterion for dimensioning tunnels
One can investigate tunnel CSA and pressure relief shafts, for a given set of train speeds, area and length.
Tunnel sizes shall limit operational speeds, even if the rolling stock can go faster; i.e. raising train speed from 350 to 400 kph requires 30-40% larger tunnel CSA
Drag forces and moments on tunnel fixed equipment inform the design of brackets and fixtures.
Mohammad Tabarra
Associate Director, Arup, UK
8th Dec 2010, HSR Tunnels 26

15. Thank you for your kind attention
Mohammad Tabarra
Associate Director, Arup, UK