CFD Analysis of a V-Shaped Desktop Fan for Near-field Control of Infected Respiratory Cloud

Energy Department, Corso Duca degli Abruzzi, 24 - 10129 Turin, Italy

^* Corresponding author: hamed.rasam@polito.it

Abstract

The respiratory cloud of an infected person contains droplets of mucosal and salivary fluid carrying germs. As this cloud spreads from the emission point, droplets accumulate, and their concentration increases in the room, unless dilution, adequate ventilation, or filtration is applied. A susceptible person standing nearby can easily be exposed to this infected cloud, potentially inhaling a higher dose of pathogens compared to someone breathing the room’s mixed air. To mitigate this short-distance risk and potential contagion, a local airflow pattern can be employed. Our study presents a numerical investigation of a desktop fan acting as a barrier to airborne pathogen diffusion at a short distance. Positioned strategically between two individuals seated closely in a confined cubic room, the portable fan generates V-shaped air blades to intercept the respiratory cloud path. Employing a validated CFD tool based on the Eulerian-Lagrangian model for particle transmission and Schiller-Naumann for particle drag force coefficient, we explore the influence of fan axial locations, heights, and power levels on particle transmission efficiency. The results highlight the importance of each parameter in impeding airborne particle transmission. Notably, a mere 0.30 m deviation from the center axis can significantly reduce the fan’s efficacy, from 99% to 29%. Similarly, lowering the fan’s height by 0.30 m from the infected individual’s mouth level decreases transmission efficiency from 99% to 31%. Moreover, varying the fan velocity from 3 m/s to 1.5 m/s yields efficiency fluctuations from 99% to 37%.