Modeling ventilation and dispersion for covered roadways

A series of computational fluid simulations was conducted to assess the relative impacts of several forced ventilation configurations on the distribution of atmospheric pollution concentrations from vehicles operating within a covered roadway. These conditions are frequently encountered in urban highways, airports, parking structures and so forth. Ventilation configurations tested included ceiling curtains and jets. A simple 2D geometry without artificial ventilation was used as a base case together with a worst-case flow scenario that assumed no transverse ambient wind flow. The base-case simulations were compared to simulations for various auxiliary ventilation alternatives. The simulations demonstrate that ventilation is necessary to effectively minimize peak ambient concentrations in covered roadways. Auxiliary overhead ventilation ports are found to result in the most dramatic improvement in pollutant concentrations. The simulations also indicate that regions of low velocity and vortex-type flow patterns with flow reversals are characteristic of situations with very high values of peak pollutant concentrations.