Air circulation study inside and outside of urban buses induced by the opening of windows

CORZO SANTIAGO; GODINO DARÍO; DAMIAN RAMAJO

Air Quality, Atmosphere and Health

Springer

Año: 2022 p. 1 - 25

1873-9318

In this work the external and internal airflow analysis in an urban bus iscarried out through computational fluid dynamics. The researchaddresses the study of the internal flow to estimate the air change ratecaused by the opening of windows. Two cases are considered: fullyopening and partially opening the windows, and three bus speeds of 20,40 and 60 km/h are assessed. The quantification of the air flow ratethrough the windows clearly displays that air enters through the rearwindows and exits the bus through the front windows. This effect isexplained by the pressure distribution in the outer of the bus, whichcauses the suction of the indoor air. At low bus speed, the incoming airflow rate increases linearly with the speed, but the improvement islower for high speeds. The theoretical air change time at 20 km/h isaround 25.7 s, which is 9 times lower than the expected by using HVACsystems. On the other hand, the estimation of the real air renewal timeby solving a concentration shows that 40 s are needed to exchange 85%of the internal air of the bus. The research also assesses the effect ofdifferent levels of occupation inside the bus. Results are conclusive torecommend the circulation with fully or partial windows openingconfigurations in order to reduce the risk of airborne diseasetransmission.