Computational Fluid Dynamics: computing power ensures tunnel safety

Proper Smoke and Heat Extraction is vital for tunnels, so that in case of calamities road users can safely escape from the tunnel and emergency services can gain safe access. Colt International BV provides solutions for smoke control in traffic, rail and metro tunnels.

The total combination of smoke control systems is designed and supplied by them, which may include tunnel ventilation systems that work by displacement of air (exhaust and/or by thrust) and by overpressure (stairwells and escape corridors). To ensure a system that is up to its task, calculations must be made. Basically, a ProTuVem calculation serves this purpose, which is fine for a first indication. Colt then validates the ProTuVem designs using CFD, or Computational Fluid Dynamics.

Design optimization

Using CFD simulations, it is possible to make more accurate predictions regarding the effectiveness of the tunnel ventilation system and the positive pressure system. With CFD, it is possible to look for possible improvements and/or system optimizations. Think for example of the fire resistant lining of the tunnel as described by Promat / Etex with the associated positive effects on safety. Colt International BV sees in CFD currently the best available method to predict (air) flows and transfer of energy for not (yet) existing situations. By doing this at a preliminary stage, expensive field tests are unnecessary.

Safety requirements for a tunnel ventilation design can be met more quickly, thanks to the reliable calculations made by CFD. Working with CFD also makes certifying a fire safety system easier and faster. A fire safety system present by or pursuant to law must have an inspection certificate issued by an ISO17020 type A accredited inspection body. This tests for the derived objective. The test can be carried out during the design phase, based on the CFD results. The lead time to obtain the certificate is thus considerably reduced.

From Practice

Vialis BV and Van Hattum en Blankenvoort BV, both part of Royal VolkerWessels, are realizing the completion and tunnel technical installations of the Tunnel Delft, the second phase of the NS railway station in Delft. In 2025 this tunnel will open in its entirety (phases 1 and 2) for train traffic between The Hague and Rotterdam. Colt International BV is the designated party to provide fire safety in the tunnels and at the station and is closely involved in the realization of the smoke control system in the station, the ventilation system in the tunnels and the overpressure systems in the emergency stairwells. Again, CFD was used to predict, through simulations, the effect of air currents in the tunnels and the station, should a fire break out.