Infection control measures for public transportation derived from the flow dynamics of obstructed cough jet

C T Wang; J C Xu; K C Chan; H H Lee; C Y Tso; Carol S K Lin; Christopher Y H Chao; S C Fu

doi:10.1016/j.jaerosci.2022.105995

Infection control measures for public transportation derived from the flow dynamics of obstructed cough jet

J Aerosol Sci. 2022 Jun:163:105995. doi: 10.1016/j.jaerosci.2022.105995. Epub 2022 Apr 1.

Authors

C T Wang^{1

2}, J C Xu², K C Chan¹, H H Lee³, C Y Tso³, Carol S K Lin³, Christopher Y H Chao^{1

4}, S C Fu¹

Affiliations

¹ Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China.
² Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Hong Kong, China.
³ Department of Energy and Environment, City University of Hong Kong, Hong Kong, China.
⁴ Department of Building Environment and Energy Engineering & Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hong Kong, China.

Abstract

During the COVID-19 pandemic, WHO and CDC suggest people stay 1 m and 1.8 m away from others, respectively. Keeping social distance can avoid close contact and mitigate infection spread. Many researchers suspect that suggested distances are not enough because aerosols can spread up to 7-8 m away. Despite the debate on social distance, these social distances rely on unobstructed respiratory activities such as coughing and sneezing. Differently, in this work, we focused on the most common but less studied aerosol spread from an obstructed cough. The flow dynamics of a cough jet blocked by the backrest and gasper jet in a cabin environment was characterized by the particle image velocimetry (PIV) technique. It was proved that the backrest and the gasper jet can prevent the front passenger from droplet spray in public transportation where maintaining social distance was difficult. A model was developed to describe the cough jet trajectory due to the gasper jet, which matched well with PIV results. It was found that buoyancy and inside droplets almost do not affect the short-range cough jet trajectory. Infection control measures were suggested for public transportation, including using backrest/gasper jet, installing localized exhaust, and surface cleaning of the backrest.

Keywords: COVID-19; Gasper jet; Jet interaction; Particle image velocimetry; Public transport.