Impact of opening shape on airflow and pollutant dispersion in a wind-driven cross-ventilated model building: Large eddy simulation

Natural ventilation, a useful mechanism to moderate the indoor temperature and to disperse pollutants, is a complex engineering problem to analyze due to a large number of influential factors such as wind direction, size, and location of openings, etc. The present paper investigates the effect of different shapes of openings, with a constant wall porosity, namely, horizontally long, squared and vertically long, on cross-ventilation in a generic isolated building. Flow and passive pollutant concentration fields are the performance indicators. The large eddy simulation (LES) approach together with the wall-adapting local eddy-viscosity (WALE) sub-grid scale (SGS) model is employed for the simulations. Validation results, based on available wind-tunnel measurements, of time-averaged velocity and pollutant concentration for the reference case are reported. Results display that the performance of cross-ventilation in reducing the pollutant concentration enhances as the height to width ratio of the openings increases and the building with horizontally long openings is the most contaminated case. The ventilation performance in the case of vertically long openings is shown to be the most effective one. Furthermore, present findings show that the participation of the turbulent diffusion flux in the passive pollutant transportation becomes smaller as the flow makes progress toward the downstream.