Risk Assessment of COVID Infection by Respiratory Droplets from Cough for Various Ventilation Scenarios Inside an Elevator: An OpenFOAM based CFD Analysis

Biswas, Riddhideep; Pal, Anish; Pal, Ritam; Sarkar, Sourav; Mukhopadhyay, Achintya

Respiratory droplets exhaled during speaking, coughing or sneezing have been responsible for the spread of the ongoing Covid-19 pandemic. The droplet dynamics depend on the surrounding air velocity, temperature and relative humidity. Droplets evaporate to form aerosols that contain the disease spreading virus. In a confined space like an elevator, the risk of transmission becomes higher when there is an infected person inside the elevator with other individuals. In this work, a numerical study is carried out in a 3D domain resembling an elevator using OpenFoam. Different modes of air ventilation are considered inside the elevator and the impact of these air circulations on droplet dynamics is investigated. The scenario of the opening of the elevator door and the passenger leaving the elevator has also been considered in order to simulate a real-life condition. A pedantic analysis of certain risk assessment factors and remedial measures to be adopted has been performed which include the number of aerosols present in the zone of 0.8 to 1.8 m, the radial spread of the suspended droplets around the mouth of the infected person. From these factors, the safe condition can be understood. The time period up to which the elevator will be risk-prone has also been investigated in case the person coughs just before leaving the elevator. After conducting these studies, the quiescent environment has been found out to be the most dangerous whereas ventilation with an exhaust fan is the safest.