Study of ventilation and virus propagation in an urban bus induced by the HVAC and by opening of windows

CORZO SANTIAGO; RAMAJO DAMIAN; IDENSHON SERGIO

COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING

ELSEVIER SCIENCE SA

Lugar: Amsterdam; Año: 2022

0045-7825

Theexternal and internal airflow and air renewalinsideurban buses have takenespecial relevance since the COVID-2pandemic. Computationalfluid dynamics (CFD)simulations, which focusonthe estimationof indoor airflow are not conclusive about the impact of using Heat,Ventilation and Air Conditioning (HVAC) systems on diseases´transmission risk while travelling with open windows has shown to bea good strategy to renew the indoor air. In order to estimate theCOVID-2 airborne transmission by aerosols, a real urban bus wassimulated by CFD. Twenty passengers (containing the driver) wereincluded in the model with a typical inhalation-exhalation breathingcycle. The concentrations of air exhaled by ten of them were trackedduring 30 min using Eulerian scalar tracer, and the concentrationsinhaled by the twenty passengers were monitored. Then, the well-knownWells & Riley risk model was applied in order to estimate thecumulative inhaled viruses and the subsequent transmission risk. Fourscenarios were considered: HVAC off with closed windows (Case 1),HVAC on with closed windows and 100% of air recirculation (Case 2),HVAC on with closed windows and 75% of air recirculation (Case 3),and HVAC off and the bus moving at 20 km/h with some windows opened(Case 4). Results clearly showed that the motionless condition (Case1) caused the highest transmission risk around the emitters withnegligible risk far from them. On the contrary, the HVAC on reducedthe maximum risk to only 6% (Case 2) and 3% (Case 3) of the riskestimated for Case 1. Finally, travelling with some open windowspromotes a large air renewal, reducing almost completely thetransmission risk.p { text-indent: 0.4cm; margin-bottom: 0.25cm; line-height: 115%; text-align: justify }a:link { so-language: zxx }