Addressing human exposures to air pollutants around buildings in urban areas with computational fluid dynamics (CFD) models

This paper discusses the status and application of Computational Fluid Dynamics (CFD) models to address challenges for modeling human exposures to air pollutants around urban building microenvironments. There are challenges for more detailed understanding of air pollutant source emissions, transport and dispersion, and the resulting human exposures. The application of CFD for detailed modeling of urban building microenvironments requires tools for complex geometry creation and meshing, advanced physical models, parallel computing capabilities and scientific visualization.

CFD simulations are able to account rigorously for details of buildings and structures in urban areas as well as local aerodynamics and turbulence. These features can be influential in determining local human exposures to environmental pollution. CFD simulation of complex distributions of pollutant concentrations within microenvironments of human exposure are feasible using today’s high performance computing. Output from CFD can be directly used to both simulate real events and provide a better understanding of exposure events than is now available from any other modeling method. In some cases the output of CFD simulations can be used in the development of better simplified modeling methods in the same way as field and wind tunnel study measurements have been used. Wind tunnel studies can be used to provide validation data for the CFD simulations for the limited physical conditions that may be studied in a wind tunnel. CFD modeling allows for the inclusion of complex physical processes such as turbulence, chemical reactions, heat and mass transfer. Through further research, validation and testing, CFD modeling has the potential to become a reliable tool for estimating pollutant concentrations for situations that today have no reliable modeling method. Discussions with examples are presented to highlight the use of CFD simulations as a tool for addressing human exposures around buildings in urban areas. Particular attention is given to geometry modeling and meshing, the application of physical models and parameters (e.g., boundary conditions and turbulence models) and simulation post processing and evaluation.