Numerical study of inter-building dispersion in residential environments: Prediction methods evaluation and infectious risk assessment

The inter-building dispersion under wind effect was focused on and the cross-infection risk was assessed. The URANS model and DES model were compared, and the representation of surroundings was evaluated to improve the prediction of airflow and pollutant dispersion among a group of buildings. The DES model can better reproduce unsteady fluctuations of airflow around the buildings, and can accurately predict the frequency of vortex shedding. The predicted Strouhal number is approximately 0.15, which is consistent with the reported value in literature, whereas the URANS model fails to reproduce the whole features of unsteady airflow and significantly under-estimates the vortex shedding frequency. Ignoring the surrounding buildings in the simulation will significantly over-estimate the downward dispersion and over-estimate the risks in lower heights. The tracer gas concentrations near the downstream buildings are four orders lower than the concentration in the index/source unit, but only one order lower than the concentration in the leeward side and on the roof of the index building, and therefore the risk is comparable to that of intra-building dispersion within the index building. The tracer gas can diffuse to a long distance with slow concentration decay in empty areas. The cross-infection risk of inter-building dispersion should not be overlooked, especially when a super infector with high pathogen generation rate exists.