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This paper investigates how the structure of the flow field and the vertical distribution of the pollutant concentration near the wall facades of street canyons are affected by the presence of some elements such as street level galleries. Numerical results are presented for various gallery geometries in combination with facade roughness elements (balconies) for a canyon of an aspect ratio equal to h/w=2.33. The results were obtained by a Computational Fluid Dynamics (CFD) simulation employing the ANSYS-FLUENT suite that incorporated the k-e turbulent (RNG) model. The simulation generated several flow structures inside the canyon (mainly vortices), whose characteristic properties (e.g. number, strength and size) are discussed in terms of the effect of the galleries on the flow field structure and the roughness generated by the building façade balconies. The results indicate a significant influence on both the flow field structure and the mass concentration distribution of the polluting particles.

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Methanol diffusion flames are computed with a 2-D Large-Eddy Simulation that uses a partial equilibrium/two-scalar exponential PDF model applied at the subgrid (SGS) level. Turbulent kinetic and scalar energy equations provide the SGS closure. The PDF scalar covariances are obtained from similarity between resolved and modeled fluctuations. Turbulence/chemistry interactions are addressed by coupling the partial equilibrium to the extinction/reignition regime that is modeled by a two-scalar reactedness-mixture fraction exponential PDF. A Lagrangian equation and a local extinction criterion represent the turbulent evolution of the reactedness progress variable. Modeling assumptions that correlated the bimodal/monomodal behavior and the interactions of the disparate timescales of the flame structure complemented the model. Comparisons with data indicate that the methodology describes significant trends over a range of turbulent and chemical timescale conditions close to extinction thus broadening the scope of application of the procedure.