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

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

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

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

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

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

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

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

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

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

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

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

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

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

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