Transport of Airborne Particles from an Unobstructed Cough Jet

<div><p>This article presents analytical and experimental results for the velocity distribution and transport of expiratory particles from an artificial cough. The stream-wise penetration distance and velocity field of the cough jet were determined through a combination of dimensionless analysis and experimental techniques. The experiments were conducted in a well-controlled environmental chamber with simplified thermal manikins to simulate human coughs and buoyant thermal plumes, and involved flow visualization, velocity measurements employing high and low velocity hot-wire anemometers, and particle size and concentration measurement. The study analyzed three particle sizes—0.77, 2.5, and 7 μm—to examine the impact of particle size on particle transport in the cough jet region and in the vicinity of a receiver occupant positioned in close proximity to the coughing source. The results indicate that the cough jet has a lower axial velocity but higher span-wise expansion rate than a steady jet with an identical discharge velocity. The particles of three sizes have a similar trajectory when considering the transport in the cough jet region. However, particle concentration distributions of the three size particles show that size is an important factor for particle transport in the vicinity of the receiver occupant where airflow velocity decays to the room background air velocity. Furthermore, the results suggest that a cough jet is able to overcome the buoyant human thermal plume and travel further ahead in the region behind the receiver occupant.</p><p>Copyright 2014 American Association for Aerosol Research</p>