Simulation of near-field dispersion of pollutants using detached-eddy simulation

• A numerical simulation of pollutant dispersion is developed using the DES model.
• Results are compared with those of RNG k–ε model as well as wind tunnel experiments.
• Limits of RNG k–ε model in reproducing the wind flow and dispersion fields are emphasised.
• The DES model demonstrates that the unsteady-state approach is more appropriate.

A numerical simulation is developed using the unsteady-state turbulence model on a structured highly refined grid to predict the wind-flow field and dispersion field of a pollutant emitted from a rooftop stack around a two-building configuration. The results obtained are compared with those of a steady-state model previously reported by the authors. The pollutant concentrations are examined on the roof where the stack is located as well as on the leeward wall of an upstream tower to the emitting building in order to evaluate how the pollutant is dispersed by the DES model compared to RNG model. DES results are discussed against those from RNG k–ε approach and wind tunnel. The study emphasises limits in reproducing correctly the wind flow and dispersion fields due to underestimation and/or overestimation of the Reynolds stress components and the steady-state methodology when using the RNG k–ε model. Despite such limits, the RNG model produces a similar average error, in terms of concentrations, to that obtained with the DES model.