Epidemic diseases are believed to be related to respiratory airborne transmission, and human coughing promotes the spread of human released particles. By discharging a large quantity of airborne particles with a high discharge velocity, coughing releases particles with a higher concentration than breathing or talking.

We designed a cough generator to examine the transport characteristics of particles from a simple transient jet. The discharge velocity, injection period, and the particle concentration in the injection are adjustable.

Here is a video shot of a cough jet (V = 0.6 m/s, duration = 1 s)

The study applies fundamental fluid dynamics to analyze velocity field of a cough jet; in this analytical study a dimension analysis is used to define key jet parameters assuming jet momentum self-preservation theory. In addition,  this study calculated the trajectories of different size particles from coughing in the cough jet region and measured their distribution in the vicinity of an exposed occupant in a close proximity to the coughing source.

POV ventilation to control the transport of particles from person-to-person

We applied a new ventilation system, protected occupied zone ventilation (POV) to reduce person-to-person cough transport. The POV works similar to an industrial air curtain to prevent the transmission of pollutants.

The schematic of the POV system

POV can bend a cough jet downward to reduce transmission

Linear slot diffusers with downward jets are good examples for POV

Possible future applications

Publications

Cao, G., Liu, S., Boor, B.E. and Novoselac, A. (2017). Dynamic interaction of a downward plane jet and a cough jet regarding particle transmission: an analytical and experimental study. Journal of Occupational & Environmental Hygiene 14(8) 618-631. doi: 10.1080/15459624.2017.1316383

Cao, G., Liu, S., Boor, B.E. and Novoselac, A. (2015). Characterizing the Dynamic Interactions and Exposure Implications of a Particle-Laden Cough Jet with Different Room Airflow Regimes Produced by Low and High Momentum Jets. Aerosol and Air Quality Research 15: 1955-1966. doi: 10.4209/aaqr.2015.03.0146

Liu, S., and Novoselac, A. (2014). Lagrangian particle modeling in the indoor environment: A comparison of RANS and LES turbulence methods (RP-1512). HVAC&R 20(4):480-495. doi: 10.1080/10789669.2014.884380

Liu, S.,and A. Novoselac. 2014. Transport of Airborne Particles from an Unobstructed Cough Jet. Aerosol Science and Technology, 48(11):1183-1194.

Liu, S., Cao, G., Boor, B.E., and Novoselac, A. (2014). A protected occupied zone ventilation system to prevent the transmission of coughed particles. The 13th international conference of Indoor Air Quality and Climate, Hong Kong.