A reverse flow is created in front of an object placed in a uniform air stream that originates from behind the object. Gaseous contaminants may then be transported into the breathing zone of a worker from sources located within the reverse flow region. This should be taken into consideration when local ventilation systems are designed. The objective of this study was to characterize the reverse flow zone created in front of a worker in a uniform flow of air,using both experimental data and numerical simulation. Experiments were carried out by moving a point contaminant source on a table placed in front of the worker, and by measuring the contaminant concentration at nose level in front of the worker. The experimentally estimated length of the reverse flow region was smallest (0.5-1.0 m) with a nominal freestream velocity of 0.1 m/s, and similar (1.1-1.4 m) with nominal freestream velocities of 0.3 and 0.5 m/s.
Welling, I., Kulmala, I., Andersson, I-M., Rosen, G., Mielo, T., Marttinen, K., Säämänen, A., & Niemelä, R. (2001). Extent of the reverse flow wake region produced by a body in a uniform flow field. Applied Occupational and Environmental Hygiene, 16(9), 900-904. https://doi.org/10.1080/10473220119185