CFD Modeling of Droplet Transport around a Human Body with Tracer gas, Eulerian, and Lagrangian Models
Donghyun Rim, SEONGJUN PARK,
Pennsylvania State University Abstract Number: 619
Working Group: Aerosol Science of Infectious Diseases: Lessons and Open Questions on Models, Transmission and Mitigation
AbstractAfter the outbreak of the COVID-19 pandemic, transport of viral aerosols has been widely modeled using computational fluid dynamics (CFD) simulation based on three approaches: 1) Tracer gas, 2) Eulerian, and 3) Lagrangian. Tracer gas model describes aerosols as a gas phase and Eulerian model assumes continuum particle, while Lagrangian model calculates discrete particle trajectories. However, very little information is available on the advantages and limitations of these models. The objective of this study is to assess the performance of the three approaches in modeling aerosol transport near a human body, considering the effect of the turbulent models, RANS SST k-w model and Large eddy simulation (LES).
The simulations were performed for an occupied room with a size of 5.5 m ⅹ 4.5 m ⅹ 2.7 m (67 m3), which had one sitting thermal manikin with aerosols (3.2 μm) released about 1.6 m in front of the manikin at an air speed of 0.2 m/s.
The result shows that the tracer gas model overpredicts aerosol concentrations in the human breathing zone (defined as the volume-averaged concentration within a 500 cm3 cuboid below the nose tip of the exposed occupant) about 20% compared to Eulerian and Lagrangian models. This is mainly because diffusion coefficient of the gas phase is about 104 times higher than that of the particle phase, and the gas phase is not affected by the gravitation settling. Eulerian model can be an alternative for Lagrangian model when LES was used for the turbulent model, because eddies created by LES model can simulate the aerosol dispersion near a human body. However, with SST k-w model, Eulerian model shows limitations in simulating the aerosol concentrations in the boundary layer, resulting in a 24% concentration difference in the human breathing zone compared to Lagrangian model.