Validation and optimization of SST k-ω turbulence model for pollutant dispersion within a building array

The prediction of the dispersion of air pollutants in urban areas is of great importance to public health, homeland security, and environmental protection. Computational Fluid Dynamics (CFD) emerges as an effective tool for pollutant dispersion modelling. This paper reports and quantitatively validates the shear stress transport (SST) k-omega turbulence closure model and its transitional variant for pollutant dispersion under complex urban environment for the first time. Sensitivity analysis is performed to establish recommendation for the proper use of turbulence models in urban settings. The current SST k-omega simulation is validated rigorously by extensive experimental data using hit rate for velocity components, and the "factor of two" of observations (FAC2) and fractional bias (FB) for concentration field. The simulation results show that current SST k-omega model can predict flow field nicely with an overall hit rate of 0.870, and concentration dispersion with FAO = 0.721 and FB = 0.045. The flow simulation of the current SST k-omega model is slightly inferior to that of a detached eddy simulation (DES), but better than that of standard k-epsilon model. However, the current study is the best among these three model approaches, when validated against measurements of pollutant dispersion in the atmosphere. This work aims to provide recommendation for proper use of CFD to predict pollutant dispersion in urban environment. (C) 2016 Elsevier Ltd. All rights reserved.