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Comprehensive evaluation of constant and variable turbulent Schmidt numbers for CFD simulation of near-field air pollutant dispersion

par Weerasuriya, A.U.;Longo, Riccardo ;Zhang, Xuelin;Cotteleer, Léo ;Parente, Alessandro
Référence Building and environment, 270, 112493
Publication Publié, 2025-02-01

Article révisé par les pairs

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Résumé :

Turbulent Schmidt number (Sct) is an essential parameter of the standard gradient diffusion hypothesis that is used for the Reynolds-Averaged Navier-Stokes (RANS) equation-based computational fluid dynamics (CFD) simulation of air pollutant dispersion. Many studies have attempted to choose the optimum Sct without considering its variability with local turbulent flow properties and height dependency. Recently, there has been a renewed interest in formulating variable Sct to model near-field air pollutant dispersion. However, these formulations are not widely employed due to a lack of knowledge concerning their use and advantages. This study aims to fill this knowledge gap by applying three variable Sct formulations for simulating pollutant dispersion around an isolated CEDVAL A1-5 building. CFD simulations were conducted using constant and variable Sct and two sets of inflow boundary conditions. The results suggested that the variable Sct formulation directly depending on flow parameters and physical properties, such as Sct_R2, display accurate prediction and is compatible with all inflow boundary conditions, differently from Sct_G and Sct_R1, which depend on model parameters, i.e. Cµ. Moreover, the three variable Sct formulations modeled similar spatial pollutant dispersion, but they modeled dispersion patterns that were noticeably different from that of constant Sct. A statistical analysis shows that the three variable Sct estimated the mean Sct in the range 0.6–0.7, with 50–60% occurrence probabilities, despite their values fluctuating between 0.11 and 1.85 in the area affected by the building.