Virtual, advance testing of optimal tunnel ventilation

Each tunnel is unique. Often the alignment changes, even during construction. Nevertheless, tunnels have to be ventilated right from day one so that no road user will be harmed in the event of a fire. A firm of consulting engineers has now developed a tunnel ventilation simulator that can be used to simulate and virtually test different tunnel ventilation scenarios in advance.


Many drivers feel uneasy when they enter a tunnel or when a traffic jam forces them to stop in one. Therefore, it’s good to know that engineers are constantly working to make tunnels safer. For example, the tunnel ventilation experts at HBI Haerter Consulting Engineers have developed a simulator that can be used to simulate and virtually test ventilation in tunnels

Safety is the top priority

Dr Rune Brandt, CEO of HBI Haerter, understands the pressure that his customers are under. “Tunnel operators today have to meet road users’ extremely high safety requirements. More frequently, motorists, cyclists, rail passengers, and pedestrians are concurrently using the same tunnel.” Meanwhile, the clock is ticking. “A tunnel has to go into operation as quickly as possible because of the tremendous cost pressure,” says Brandt. “Not to mention the fact that the alignment may have to be changed during construction!”

Simulating all ventilation scenarios

“With our tunnel ventilation simulator, we can simulate all scenarios, virtually control the automation, and simulate how the ventilation system will respond under various conditions,” says Brandt. The engineers at HBI Haerter are testing all “foreseeable and unforeseeable scenarios.”

“For example, we use our tunnel ventilation simulator to check the positions of flow anemometers, fans, and ventilation dampers and to test how to properly control the ventilation and readjust it in the different zones so that smoke can be discharged and fresh air drawn in if a fire occurs,” Brandt explains.

Tested 1,000 times in advance

For the functional simulation, HBI’s tunnel ventilation simulator can use the SIMATIC S7-PLCSIM Advanced virtual controller. For engineering, it uses the TIA Portal. Parallel to tunnel construction, all controllers are virtually tested in this combination in a “virtual control center.” As a result, the ventilation system’s controller is already fully developed on its first day of use. The control system knows what it’s doing and can evaluate the data from three installed flow anemometers, assess the plausibility of conflicting measurements, and adjust the ventilation to accommodate new situations within seconds.


And what if a fire breaks out, as it did in 1999 in the Mont Blanc Tunnel, which lacked a reliably functioning safety system? In this case, the controller in a tunnel with a ventilation system that’s been virtually tested in advance by HBI Haerter promptly opens the ventilation dampers, the smoke is extracted, and the fans optimize the air flow so that fresh air can be drawn in. All road users can exit the tunnel safely.

We’re simulating all foreseeable and unforeseeable scenarios.
Dr. Rune Brandt, CEO HBI Haerter AG

Safety and reliability in ongoing operation

But it isn’t just a matter of fire safety. “Thanks to the simulation, our customers can also save money during ongoing operation, because there’s no need for all the ventilation systems to run at full speed when they can be intelligently controlled,” says Brandt. “The system can also be predictively maintained, thanks to the data reported to us by the sensors.”

Added value in the cloud

Operators are still supplying data to the consulting firm in the traditional form. “When the data needs to be analyzed in real time, MindSphere is the logical choice,” says Brandt. The customers are still a little hesitant, “but we’re watching the development.”


With the aid of MindSphere, the open, cloud-based IoT platform, the data collected can be analyzed and processed as meaningful smart data for increased availability and improved tunnel safety. “After all, the point is to simply drive through the tunnel – and enjoy the ride,” says the tunnel expert.

Tunnel operators today have to meet road users’ extremely high safety requirements.
Dr. Rune Brandt, CEO HBI Haerter AG

HBI Haerter also uses the digital twin method to simulate and virtually test smoke in tunnels and on train platforms. This includes visualizing how smoke propagates in tunnels, how fresh air is drawn into the tunnel, and how traffic affects air flows. For this process, the simulation experts use Simcenter STAR CCM+ software.

This software even makes it possible to enter the tunnel or platform in advance using VR headsets. “Users can release massless particles to visualize the flow field and the relevant smoke and temperature layers,” says Erwin Schnell, project manager at HBI Haerter. “In complete safety, they can walk to the exits nearby and determine whether the escape routes are smoke-free.”

HBI is a firm of consulting engineers. The services focus on the design, planning and execution of projects in the field of tunnel ventilation, prediction of emissions, safety issues as well as the aerodynamics and thermodynamics of road and rail tunnels.
From the offices in Bern and Zurich, both Switzerland, and in Heidenheim, Germany, more than 30 ventilation specialists work on the projects, amongst others in Australia, U.S., Sweden, Switzerland, and Germany.

July 2019

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