Urban emissions

Air quality is a serious health concern for many residents in built up environments. The opening of new industrial sites, or the expansion of existing facilities can raise serious questions regarding the health and odour impacts on the surrounding environment. Addressing these concerns can be an essential part of receiving approval from local councils or regulatory bodies. Regulators may request an impact assessment prior to giving a permit or license to a project.

Traditional plume dispersion models such as AERMOD and its predecessor AUSPLUME are incapable of accurately resolving downwash and building effects. This often renders them unsuitable for emissions from small stacks in heavily populated areas. CFD provides a more rigorous, and accurate solution for these cases, and can be used to determine if a facility is acceptable from both a safety and odour point of view. Should CFD modelling show that a facility is not acceptable, it can be used to determine the required level of filtration, or stack changes that will result in an acceptable outcome.

 

Figure 1: Modelled dispersion of the plumes from a pair of stacks.

 

Synergetics assessed emissions from a proposed facility near residential areas. High-level CFD was used to determine the worst-case weather conditions resulting in maximum ground level and façade concentrations for the surrounding buildings. We then compared these concentrations to toxicity and odour thresholds, presented the results to the local authorities. The CFD results played a critical role in reducing community concerns, and the facility gained approval to operate.

Figure 2: Simulated dillution factor at ground level under worst case weather conditions. A contour value of 8.4 (red) corresponds to an odour that 50% of people will generally find offensive.

For more air quality examples, see our services page.