Droplet Propagation Modeling Helps Guide the Public Out of COVID-19 Lockdown

Droplet Propagation Modeling Helps Guide the Public Out of COVID-19 Lockdown
A software developer used Cradle CFD to model the propagation of droplets when people breathe, sneeze or speak in train carriages.

As governments struggle to adapt to the new normal during a global pandemic they are turning to computer simulations, initially designed for industrial applications, to help tackle the challenge of reducing COVID-19 transmissions in public spaces as lockdowns are eased.

Computational Fluid Dynamics is a powerful computer-aided engineering tool for measuring the effectiveness of wearing a mask to limit the spread of COVID-19. Healthcare and governmental authorities have turned to models from simulation specialist MSC Software, part of the Manufacturing Intelligence division of Swedish technology company Hexagon AB, as they evaluate lockdown strategies and provide guidance for citizens.

MSC Software’s Cradle CFD is a next-generation CFD tool that utilizes unstructured mesh to accurately represent complicated geometry – used to model everything from airflow within buildings to MotoGP bike aerodynamics. To address the challenges of COVID-19, a software developer in Osaka used Cradle CFD to model the propagation of droplets when people breathe, sneeze or speak in public spaces such as train carriages. Different scenarios include openly sneezing, sneezing into an elbow and sneezing wearing a mask.

Video: Software Cradle, part of Hexagon’s Manufacturing Intelligence division

The advanced modeling allows for particle size, breathing cycles, typical airflow rates, velocity, gravity and air turbulence. It also compensates for the effect of natural airflow and HVAC systems, modeled on the Mitsubishi Electric air conditioning system installed in Japan Rail East E233 series cars (click here for more info on simulations in a metro car).

The shape of the mask is based on publicly available surgical-style masks, rather than more advanced masks available to healthcare professionals, while the droplet filtration and pressure drop caused by the mask is calibrated using data from a well-known surgical mask producer.

These simulations make it clear that wearing even a standard mask significantly limits the distribution of potentially infectious droplets in these environments, helping reduce COVID-19 transmissions, says MSC Software’s vice president of marketing Dr. Keith Hanna.

Video: Software Cradle, part of Hexagon’s Manufacturing Intelligence division

Until people see these visual models in action they perhaps don’t appreciate how far a sneeze can travel, which helps give both government advisors and the general public a better understanding of the risks around public transmission of COVID-19, Hanna says.

“The beauty of these kinds of computer simulations is that once you have a base model you can start to pose “what if?’ scenarios – such as what if people wear masks, or what if people stay further away from each other – which helps the government make informed decisions. We can also apply this kind of modeling to other environments such as aircraft, allowing for the impact of recirculated air, when making decisions about the safety of long-haul flights.”

Based on the strength of these simulations, several of Hanna’s colleagues were invited to contribute to the Belgium Coronavirus Task Force to advise on the best ways to restrict the spread of COVID-19 as lockdown restrictions are eased. Several other governments have also approached MSC Software for assistance, plus the company has set up a task force to help teams that want to develop simulations further.

“There are so many different scenarios and permutations to consider, such as the effectiveness of perspex shields between customers sitting in restaurants, where this kind of modeling can show us the best way forward as we continue to fight the threat COVID-19.”


READ ALSO: Digital Simulation Reveals Social Distancing Measures Insufficient Against COVID-19


 

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