Tamoios Case

Before the installation of massive extraction ventilators in the Tamoios Tunnel, we read the project design to visualize how the airflow would be in certain locations. With this, we identified a possible air recirculation zone close to where the ventilators would be installed, which, in the worst case, would impair the operation of some of the 6 ventilators installed. If the team responsible for building the tunnel failed to improve the geometry of the tunnel to minimize possible air recirculation, the equipment would not be able to operate properly and impair tunnel ventilation. 

When raising the problem to the customer, FanTR calculated how the tunnel's air flow would be under those conditions, using the CFD and the scanned tunnel gallery geometry that was provided by Tamoios' geology team. The concessionaire's ventilation consultant, in collaboration with our team, came up with some restrictions, from the integrity of the excavated rock to the space needed for the constant movement of maintenance trucks on site. It was also found that it would not be possible to change the location of the ventilators but to adjust their position a few meters forward or backward. 

CFD simulation of the original design with the possible low speed recirculation zone

With the customer's agreement that there could be a recirculation issue, we collected other relevant information including the geometry, anticipated ventilator operation, expected speed within the tunnel, and car restrictions. All of this information has been considered to find a viable solution. So, we performed a CFD simulation which indicated that the proper functioning of the ventilators would be compromised due to a low-velocity recirculation zone caused by the rock contour. The solution therefore would be to sculpt the rock to smooth it out, but given the risk of collapse involved, it would not be possible to change the shape of the rock in question. 

To solve the problem, FanTR proposed the construction of a wall that would work as a “cowl” – just as a car has an engine wrapped by a cowl – providing a unique way to improve airflow in that region. Having decided on the construction of the wall, the next step would be to define its geometry. FanTR carried out several CFD simulations, with several interactions, until it found the most suitable geometry for the wall, guaranteeing the solution to the possible problem of air recirculation that would exist in that place.

CFD simulation of the project with the construction of the wall as a “fairing”

After the construction of the wall, during the tests, it was possible to verify the result of the simulation in practice: the recirculation that previously occurred in the place where there was no ventilator was stopped. FanTR predicted the flow behavior qualitatively and this generated a positive result for both our client and the company, which was able to help the client and avoid future problems.