Evaluation of computational and physical parameters influencing CFD simulations of pollutant dispersion in building arrays

• Published in: Building and environment 2018-06, Vol.137, p.90-107
• Main Authors: Dai, Yuwei, Mak, Cheuk Ming, Ai, Zhengtao, Hang, Jian
• Format: Article
• Language: English
• Subjects: Arrays; Aspect ratio; Building arrays; Buildings; CFD simulation; Computation; Computational parameters; Computer applications; Computer simulation; Detached eddy simulation; Dispersion; Fluid dynamics; Large eddy simulation; Parameters; Physical properties; Pollutant dispersion; Pollutants; Pollution dispersion; Sampling; Sensitivity test; Tracer gas; Turbulence; Turbulence models; Vortices; Wind tunnels
• ISSN: 0360-1323; 1873-684X
• DOI: 10.1016/j.buildenv.2018.04.005

Many CFD studies have investigated the influence of computational parameters on the predicted concentration distribution of pollutants around isolated buildings, but such studies for building arrays are still lacking. This study systematically evaluated the influence of four computational and two physical parameters on pollutant dispersion in building arrays, including turbulence models, grid resolution, discretization of time step size Δt, length of sampling period, aspect ratio of the arrays, and release rate of tracer gas. Throughout these evaluations, a set of published wind tunnel experimental data was used to validate the CFD models. For concentration simulations, the Large Eddy Simulation (LES) model gave the most accurate results but still had limitations in areas near the source, whereas the Detached Eddy Simulation (DES) and the Reynolds Averaged Navier-Strokes (RANS) RNG k−ε models underperformed in some areas. The results of the LES and DES simulations varied with changes in Δt∗ and sampling length until Δt∗ was less than 0.24 and the sampling length was higher than 2400 Δt∗ for LES and 1200 Δt∗ for DES. A larger aspect ratio did not necessarily result in a higher concentration field than a smaller ratio. An increase in the tracer gas release rate did not change the general dispersion characteristics, but it still affected the concentration distribution in the areas near the source and resulted in a larger polluted area. The findings of this study are intended to contribute to improvements in the quality of CFD simulations of pollutant dispersion in building arrays. •RANS, DES and LES simulations of pollutant dispersion in building arrays evaluated.•Time step size and sampling length of LES and DES models analyzed.•LES shows overall best performance but with limitations in area close to source.•Larger aspect ratio does not necessarily results in higher concentration.•Higher tracer gas releasing rate leads to larger polluted area.