Article summary: PETA engineering instructor Dr Althea de Souza recently chaired a virtual community event to discuss how computational fluid dynamics (CFD) may be useful in the fight against COVID-19.
The challenges and issues that should be considered before engaging in CFD simulations were a big part of the discussion.
With the early evidence on virus transmission at the start of the COVID-19 pandemic changing quickly, and as understanding of the role of airborne transmission grew, there was increasing interest in using simulation to study infection risks.
Dr de Souza has a background in engineering simulation, specifically in CFD. Until recently, she chaired the NAFEMS International CFD Working Group, who decided that a virtual discussion event would be the best way to explore the most appropriate use of engineering simulation in relation to COVID-19.
Following this event, Dr de Souza wrote an article summarising the key points discussed at the event, which was published in Benchmark, The International Magazine For Engineering Designers & Analysts from NAFEMS in January 2021.
What was discussed at the event?
As COVID-19 is spread by respiratory aerosols and airborne droplets, users of CFD tools have naturally asked themselves what simulations could be carried out to help protect people against infection. CFD makes visible what would otherwise not be seen, but how effective would these simulations be in actually capturing what is important? The group were conscious of the risks from misusing CFD, either from poorly designed simulations or inappropriate conclusions from simulations.
The event’s guest speaker was Professor Cath Noakes, whose work includes both simulation and physical studies of airborne pathogens and who leads the Environment and Modelling Group, a SAGE (Scientific Advisory Group for Emergencies) sub-group focusing on the science underpinning environmental transmission of COVID-19.
Professor Noakes explained airborne transmission and the spread of COVID-19, stating that although it is a respiratory virus, it can also be spread through direct contact and that the risk factors relating to transmission are quite wide-ranging.
Two sides to the story
Two members of the CFD working group outlined the different views that could be taken.
Simon Fischer presented the opportunities for CFD, outlining the strengths of CFD as follows:
- it uses established models
- validated simulations of turbulent multiphase flows
- it handles complex geometries
- it is faster, safer, and more cost-efficient compared to experimentation
- substantial existing expertise in relevant industries and related research
CFD can be used to support scientific research in gaining more detailed insights into the fluid mechanics associated with the virus and its transmission. By assessing real life and ‘what if’ scenarios, the conclusions from simulations can be useful in guiding society, industry and politics on adequate safety measures. There is also a strong case for using CFD to improve ventilation systems, rehabilitation devices and optimise pharmaceutical processes.
Anthony Mosquera played the role of devil’s advocate, arguing against the use of CFD; an unfamiliar role for a long-term member of the NAFEMS CFD Working Group and someone who spends their life working with CFD tools.
Anthony presented the main measures that can be used to reduce the risk of transmission. The measures are all qualitative, so can CFD enable us to provide more quantitative measures? He considered each in turn and questioned whether CFD can provide useful further knowledge than can be obtained from other sources.
Anthony concluded that the question we should ask is “What decisions does CFD enable us to make to reduce our risk from COVID-19 that we would not have known by other intuitive, already available, more timely or less costly means?” He suggested that CFD needs to be validated by experiments and as those experiments alone can give us the information we need, we don’t need to do both.
The event also included presentations from representatives from the Chartered Institute of Building Services Engineering and the Health and Safety Executive. After the presentations, the floor was opened for discussion and questions from the audience.
A poll taken during the event showed that 29% of attendees have undertaken CFD work related to COVID-19, whilst 54% haven’t, although others are considering it.
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