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Comparison of computational simulations of airflow patterns near the inlets of the IOM inhalable and GSP samplers.

American Industrial Hygiene Conference and Exposition, May 10-15, 2003, Dallas, Texas. Fairfax, VA: American Industrial Hygiene Association, 2003 May; :46
A number of numerical experiments were conducted, using commercial computational fluid dynamics software, to investigate airflow patterns in the inlet region of the 10M Inhalable (10M) and GSP Samplers (GSP). Experiments were done for freestream velocities from 0.25 m/s to 1 m/s including orientations from 0 degrees to 180 degrees for samplers in freestream air and mounted on bluff bodies. In addition, monodisperse particles of 6, 10, 20, and 50 micrometers were introduced into the flowfield and sampling efficiencies were calculated based on the ideal isokinetic sampler. At lower freestream velocities, for samplers alone in freestream flow, the change in the flowfield was less pronounced for the 10M sampler than for the GSP sampler. In addition, the GSP's suction distance extended farther from the inlet than did the 10M's. When mounted on a bluff body, the GSP's geometry, being larger and longer than the 10M, placed it farther out from the body and closer to undisturbed freestream flow. The 10M, however, collected particles from within the zone of stagnation caused by the bluff body. As the freestream velocity is increased, the zone of stagnation decreases in size and the area of freestream flow eligible for undisturbed sampling increases. Results of the numerical experiments were compared to empirical data (Jerome Smith and Aaron Bird, publication in press), which suggest similar findings. At the other orientations, the geometry of the samplers or bluff bodies dominates the effect on freestream flow and the sampler subsequently collects particles from a region of recirculation, stagnation, or separation. Sampling efficiency calculations based on particle trajectories were found to generally agree with empirical data for the 0 and 90-degree orientations. For the 180-degree orientation, agreement was relatively poor. The results of this study were used in developing a formal validation methodology for comparing numerical and empirical data.
Simulation-methods; Air-flow; Samplers; Air-monitoring; Air-quality-monitoring; Air-sampling; Sampling-equipment
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Research Tools and Approaches: Exposure Assessment Methods
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American Industrial Hygiene Conference and Exposition, May 10-15, 2003, Dallas, Texas