Expiratory Droplet Dispersion in a Mechanically Ventilated Enclosure

After the epidemic outburst of avian influenza and severe acute respiratory syndrome (SARS) in East and Southeast Asia, there has been a burgeoning research interest in investigating the control and transport's mechanisms of airborne bacteria and viruses indoors and in confined environments such as aircraft cabin. Dispersion of microorganism-laden aerosols exhaled from infected patients was admitted as a potential airborne transmission pathway. Consequently, competent understanding of aerosol dispersion and deposition is necessary to improve exposure assessment tools and models and endorse efficient ventilation strategies that can considerably reduce indoor particle concentrations and improve the indoor air quality.

This investigation attempts to provide a realistic simulation of the time-dependant flow field in a chamber inhabited with two heated manikins using the well resolved LES approach. The potential of both the Eulerian and the Lagrangian approaches coupled to LES of non-isothermal airflow to study dispersion characteristics of expiratory aerosols has been examined.

Experimental and numerical findings on the flow and temperature fields were recorded and show all good agreements. By taking into account the uncertainly of the particle counter used in the experimental work, globally the agreement between the experimental results and the computational modeling predictions on aerosols rates of decay is quite acceptable.

Keywords: Indoor air quality, Large eddy simulation, particle-laden flow, turbulence, Lagrangian description, Eulerian description, aerosols, thermal effects, deposition, ventilation schemes