Your place in public transport determines the level of exposure to expired droplets – Eurasia Review
The COVID-19 pandemic has revealed the urgency of understanding how public transport ventilation systems transmit viruses and how exhaled droplets evolve in ventilated spaces. The researchers wondered if these ventilation systems could be improved to reduce the transmission of the virus.
In Physics of Fluids, by AIP Publishing, researchers at IBM Research Europe developed a model with unprecedented level of detail and focused on conditions that are more characteristic of asymptomatic transmission. The multiphysics model involved the dynamics of air and droplets, heat transfer, evaporation, humidity, and the effects of ventilation systems.
“By visualizing the droplets and the flow, you realize the number of physical phenomena that take place around us that go unnoticed, such as the complex interactions between the body’s natural plumes, exhalation and ventilation,” said L ‘author Carlos Peña-Monferrer. “When it comes to preventing the risk of infection, that’s precisely what makes it hard to contain. “
The researchers analyzed what happens when speech droplets are exhaled by a row of passengers seated in a ventilated space, such as those in public transport vehicles. In some of these systems, air is injected at the top and extracted at the bottom through the vents near the window seats.
This generates internal recirculation to improve thermal comfort and remove contaminants, but researchers wondered if certain seating positions negatively affect circulation.
The team found that the droplets from the window seat rose further and filled the space of other passengers to a lesser extent soon after exhaling. In addition, the droplets released from the middle seat further contaminated the aisle passengers, indicating that the downward flow of personal ventilation in the aisle seats could displace the droplets downward and increase the risk of infection.
The droplets released from the aisle were immediately drawn down through the ventilation system.
The researchers modeled various scenarios in great detail, such as a situation in which passengers in different seats uttered a vowel for a few seconds. By creating a detailed representation of the flow field and tracking each droplet, they were able to reconstruct their ventilation paths.
Going forward, the team will replicate conditions that more faithfully represent the diversity of human activities on public transport vehicles to help inform the actions, design and operation of future ventilation systems for safer environments.
“These high-resolution simulations were focused on public transport vehicles, but they could be extended to commercial or residential buildings, healthcare facilities, offices or schools,” Peña-Monferrer said.