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Key outcomes

  • GHG emissions minimised
  • Plume dispersion target achieved
  • Regulatory requirements satisfied

Vehicle emissions form a large source of urban pollution. Inside tunnels, emissions result in reduced air quality, leading to requirements for tunnel ventilation. Emissions must be adequately dispersed to ensure safe environmental conditions both in the tunnels and near ventilation points. Computational fluid dynamics (CFD) can provide full understanding of the three-dimensional flow patterns inside tunnels. CFD can effectively predict the dispersion levels inside complex tunnel geometries and the resulting impacts on air quality and visibility.



Figure 1: Animation showing the Simulated exhaust plumes from trucks driving through a tunnel. The ventilation air extraction point is located to the left. The dispersion of emissions depends on many factors including the vehicle size, number of vehicles, speed of vehicles and the ventilation rate. Optimizing the ventilation system requires an understanding of the conditions within the tunnel.

Synergetics engineers perform CFD simulations of ventilation inside tunnels as well as emissions near the tunnel portal and ventilation stacks. The optimization of the emission strategy to both minimize emissions and achieve acceptable human health and environmental exposures is based on the results obtained.

CFD modelled isosurface of the plume from a tunnel portal.

Figure 2: CFD simulation of the spread of the plume from tunnel portal emissions. The plume is coloured by wind speed, and is observed to spread slowly along the road canyon, before spilling over the barriers and being carried downwind.

For further CFD modelling of transportation applications see our sector page.