CFD simulation of COVID-19 saliva aerosol removal in a gym by ventilation and air cleaning

Within a time span of only a few months, the SARS-CoV-2 virus has managed to spread across the world. More than one year later, on 26 Jan. 2021, the World Health Organization noted 98,925,221 confirmed cases and 2,127,294 confirmed deaths due to COVID-19. The SARS-CoV-2 virus can spread by close contact, which includes large droplet spray and inhalation of microscopic droplets and by indirect contact via contaminated objects. There is mounting evidence that the virus can also be transmitted by inhalation of aerosols at short-to-medium range. Saliva aerosols are generated when sneezing, coughing, talking or just exhaling. It can be assumed that aerosol concentrations in indoor environments should be kept low in order to minimize the potential risk of virus transmission. However, there is little knowledge on the aerosol concentrations in different types of indoor environments. In a gym, large aerosol emissions occur due to physical exercise and associated breathing patterns. Therefore, this study will employ Scale-Adaptive Simulations (SAS) and Large Eddy Simulations (LES) with Ansys Fluent to investigate the dispersion of aerosols produced by breathing during physical exercise in a gym and to evaluate the potential of aerosol removal by ventilation and air cleaning. The CFD simulations will be validated by comparing the CFD results with the previously performed aerosol measurements by the authors in which 35 test persons performed physical exercise in a gym and aerosol concentrations were measured with particle sizers covering the range of 0.254 to 35 μm. The SAS and LES simulations will be performed at full scale and will employ high-resolution computational grids (about 100-150 million cells in total) with near-wall cell sizes down to 1 mm to also resolve the thin viscous sublayer near the surface of the persons. The results are expected to contribute to strategies to limit aerosol concentrations in gyms but also other indoor environments in order to mitigate the spread of SARS-CoV-2 as well as other viruses in future pandemics.