CFD assessment of road tunnel ventilation

01 / THE CHALLENGE

Review CO distribution through the tunnel

Graphler Technology Solutions used Computational Fluid Dynamics (CFD) to evaluate a road-tunnel ventilation arrangement with jet fans and vehicle emissions. The assessment focused on carbon monoxide (CO) concentration against a project acceptance criterion of 60 ppm.

The engineering task was to examine how air moved through the tunnel and how the resulting flow distributed CO around the vehicles. The concentration field provided the acceptance check, while velocity contours and streamlines helped explain the flow pattern.

02 / OUR APPROACH

Represent the geometry, vehicles and jet fans

The three-dimensional CFD domain was developed from the supplied drawings. It included the tunnel boundaries, vehicle geometry and jet-fan arrangement. The documented setup specified five jet fans per lane.

Original cross-section view

The 90-second value describes the vehicle crossing input. It is not a stated simulation duration or pollutant-clearance time.

The study reviewed velocity and CO on a section identified as Result Plane 03, together with streamlines through the tunnel. These views connected the ventilation arrangement with the predicted flow and concentration fields.

03 / THE FINDINGS

Reported maximum CO was below the criterion

The study reports a maximum CO concentration of 56 ppm, compared with its stated acceptance criterion of 60 ppm. This is a comparison for the documented model and operating assumptions.

Reported maximum CO

56ppm

Numerical study result

Project acceptance criterion

60ppm

Benchmark stated in the source

ppm means parts per million. The source does not identify a governing standard or concentration-averaging interval; 60 ppm is presented here as this study’s criterion.

CO concentration · Result Plane 03

Use the flow field to explain the concentration pattern

The velocity contour shows variation in air speed along the result plane. The study used this view to examine regions of low velocity, recirculation and local acceleration within the tunnel.

Velocity magnitude · Result Plane 03

The streamline view complements the plane contour by showing the predicted routes of airflow through the domain and around vehicle obstructions. It helps the reader relate the fan locations to the wider circulation pattern.

Airflow streamlines through the tunnel

04 / ENGINEERING VALUE

Connect the ventilation arrangement with its CO result

The assessment provided a documented basis for reviewing the proposed jet-fan arrangement against the project’s CO criterion. It paired the reported maximum concentration with spatial flow evidence, making both the numerical result and the movement of air visible.

The practical finding was that the reported maximum of 56 ppm fell below the stated 60 ppm benchmark under the assessed conditions.