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Impact of Boundary Layer Separation on Local Exhaust Design and Worker Exposure.

PB91185298

Publication Date	1990
Personal Author	George, D. K.; Flynn, M. R.; Goodman, R.
Page Count	30
Abstract	Flow visualization and tracer gas studies were conducted in a wind tunnel with a mannequin, to examine the phenomenon of boundary layer separation as it relates to a worker's breathing zone concentration. A simple conceptual model was used which was based on mass transport by vortex shedding. The model provided a reasonable estimate of the mannequin breathing zone concentration. An empirical model was developed which then related the measured concentration to the distance from the source to the breathing zone for conditions where the contaminant was released downstream in a uniform flow. The results of the mannequin experiments suggested that boundary layer separation plays a significant part in determining the concentration of contaminant in the breathing zone. The interaction of the separated boundary layer with a contaminant source downstream of a person in uniform flow can pull contaminant back into the breathing zone of the person. The amount of contaminant observed in the breathing zone was much less when the mannequin was positioned such that the air could flow from the side. The turbulent mixing zone was formed more to the side of the mannequin and thus has less opportunity to interact with the contaminant source. These results suggested that in situations such as paint booths where a worker is immersed in a uniform flow, a higher level of control may be achieved by standing to the side of the workpiece.
Keywords	Boundary layer separation Occupational exposure Industrial hygiene Environmental models Ventilation Exhaust hoods Air flow Laboratory tests Wind tunnels Pollution transport Indoor air pollution Spray painting Simulation Air pollution control Design Local exhaust ventilation
Source Agency	National Institute for Occupational Safety and Health
NTIS Subject Category	68A - Air Pollution & Control 94D - Job Environment 41I - Job Environment
Corporate Authors	North Carolina Univ. at Chapel Hill. Dept. of Environmental Sciences and Engineering.; National Inst. for Occupational Safety and Health, Cincinnati, OH.
Supplemental Notes	Sponsored by National Inst. for Occupational Safety and Health, Cincinnati, OH.
Document Type	Technical Report
NTIS Issue Number	199116

Impact of Boundary Layer Separation on Local Exhaust Design and Worker Exposure.

Impact of Boundary Layer Separation on Local Exhaust Design and Worker Exposure.
PB91185298

Publication Date	1990
Personal Author	George, D. K.; Flynn, M. R.; Goodman, R.
Page Count	30
Abstract	Flow visualization and tracer gas studies were conducted in a wind tunnel with a mannequin, to examine the phenomenon of boundary layer separation as it relates to a worker's breathing zone concentration. A simple conceptual model was used which was based on mass transport by vortex shedding. The model provided a reasonable estimate of the mannequin breathing zone concentration. An empirical model was developed which then related the measured concentration to the distance from the source to the breathing zone for conditions where the contaminant was released downstream in a uniform flow. The results of the mannequin experiments suggested that boundary layer separation plays a significant part in determining the concentration of contaminant in the breathing zone. The interaction of the separated boundary layer with a contaminant source downstream of a person in uniform flow can pull contaminant back into the breathing zone of the person. The amount of contaminant observed in the breathing zone was much less when the mannequin was positioned such that the air could flow from the side. The turbulent mixing zone was formed more to the side of the mannequin and thus has less opportunity to interact with the contaminant source. These results suggested that in situations such as paint booths where a worker is immersed in a uniform flow, a higher level of control may be achieved by standing to the side of the workpiece.
Keywords	Boundary layer separation Occupational exposure Industrial hygiene Environmental models Ventilation Exhaust hoods Air flow Laboratory tests Wind tunnels Pollution transport Indoor air pollution Spray painting Simulation Air pollution control Design Local exhaust ventilation
Source Agency	National Institute for Occupational Safety and Health
NTIS Subject Category	68A - Air Pollution & Control 94D - Job Environment 41I - Job Environment
Corporate Authors	North Carolina Univ. at Chapel Hill. Dept. of Environmental Sciences and Engineering.; National Inst. for Occupational Safety and Health, Cincinnati, OH.
Supplemental Notes	Sponsored by National Inst. for Occupational Safety and Health, Cincinnati, OH.
Document Type	Technical Report
NTIS Issue Number	199116