Study on the combined effect of wind and buoyancy on cross-unit contamination around a high-rise residential building

In this paper, the characteristics of air cross-contamination around a high-rise building under the combined effect of wind and buoyancy are numerically studied. A 1:1 typical multi-unit building model is constructed and the risks of air contaminant building ingress under various environmental conditions are quantitatively evaluated. Firstly, the reentry ratios are quantified to evaluate the possible cross-unit dispersion without considering thermal effects. Then, the flow field and dispersion behavior are further analyzed considering the effect of wall surface temperature rise. The simulated concentration fields in three intervals of generally recognizes Richardson number (Ri) are investigated from the combined effect of wind and buoyancy. It is found that reentry ratios in multiple cases can reach 10.0%, which indicates that the air cross-contamination is an important route that cannot be neglected when a highly infectious airborne disease outbreak in high-densely residential environment. And the largest reentry ratio is detected when the windward surface temperature difference is 15 K above the ambient air at the wind speed of 1.0 m/s, with Ri=14. This study helps deepen our understanding of the mechanisms of cross-contamination under the influence of solar radiation, and will be useful for the prevention and control of accidental infectious diseases outbreaks.