A statistical framework using LES to assess the effect of internal heating and natural convection on airborne transmission*

Under standard ventilation within confined spaces, the flow corresponding to the natural convection from a heat source such as a human adult, a heated wall or any electronic equipment may be substantial. The present work builds on a recently proposed statistical framework using high-fidelity large-eddy simulations and particle overloading (Salinas, J. S., Krishnaprasad, K. A., Zgheib, N., Balachandar, S. (2022). Improved guidelines of indoor airborne transmission taking into account departure from the well-mixed assumption. Physical Review Fluids, 7(6), 064309). More specifically, we investigate the effect of heating on the mixing of pathogen concentration. Several high-fidelity simulations were considered within a canonical room of size 10m × 10m × 3.2m with over 20 million droplet nuclei that were individually tracked. The heat sources consisted of a heated wall and volumetric heat sources, representing one or more adults/children in the room. In each simulation, the strength and positioning of the source were varied. Our statistically relevant results indicate that provided the flow is turbulent, the presence of heat sources or heated boundaries have an effect on the room averaged statistics, which can be accounted for in the well-mixed theory. Furthermore, we investigate the added effect of filtration, and optimal ACH (air changes per hour) as it pertains to reducing the risk of airborne transmission.