Three Dimensional Concentration Fields in the Near-Wake of Anthropomorphic Mannequins in Uniform Freestreams and Assessment of Vortex Shedding as a Mass Transfer Mechanism

摘要

Studies were conducted on the spatial distribution of concentration in the vicinity of an anthropometric mannequin in a uniform freestream. A set of concentration measurements was performed to obtain the spatial distribution of concentration with the fixed source placed in their recirculation zone. Sulfur-hexafluoride was used as a tracer gas. Eight isocontour maps were generated by using the results of the study. The heights of the planes were approximately the positions near the navel, the heart and the mouth of the mannequin. Results indicated that the three dimensional concentration field downstream of workers in uniform freestreams is unlikely to be very well mixed if the source is in the near/wake and that vortex shedding is experimentally observed over certain regions of the body but not in others. From the experimental results obtained in the study and those taken from the literature, the authors suggest that a mannequin can be divided into three regions with respect to vortex shedding: the free end region (from the top to the neck) characterized by a down wash effect, the intermediate region (from the chest to the elbows) characterized by the combination of the down wash effect and the vortex shedding, and the vortex shedding region (from the waist to the knee) characterized by the vortex shedding.