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An inlet velocity profile: an important factor in computational fluid dynamic simulation of indoor contaminant dispersion.

Lee-E; Feigley-C
American Industrial Hygiene Conference and Exposition, June 2-7, 2001, New Orleans, Louisiana. Fairfax, VA: American Industrial Hygiene Association, 2001 Jun; :65
Determining airborne contaminant transport and distribution in buildings is often essential for understanding indoor air quality problems. Computational fluid dynamics (CFD) has been used increasingly to simulate airflow and contaminant transport processes, but many simulation efforts have not been wholly successful. Thus, understanding the factors affecting the accuracy of such simulations is critical. The goal of this study was to test and validate CFD approaches for simulating the dispersion of gases and vapors. Tracer gas concentrations were measured at points in a three-dimensional grid throughout a l-m x 0.3-m x 0.7-m chamber using a photoionization detector. Air flowrates were scaled using kinematic similarity criteria to represent a full-sized room at two realistic Reynolds numbers (Re = 500 and 5000). Also, chamber tracer concentration was simulated using CFD, initially assuming that air inlet velocity was normal to and uniform across the inlet face. The simulated three-dimensional distribution of tracer gas concentration matched measured patterns moderately well at the high Re, but significant differences in these patterns were observed at the low Re. Measured air velocity was found to vary substantially across the inlet face and the velocity profile differed for the Re numbers tested. Thus, another set of CFD simulations accounting for inlet velocity variation was performed. For the high and low Re numbers respectively, the average differences between measured and CFD concentrations were 41 % and 55% assuming uniform inlet velocity, but only 9% and I % using measured inlet velocity profiles in the simulations. Graphical comparisons revealed that CFD underestimated observed concentrations for both inlet boundary condition treatments, but use of measured inlet velocity profiles produced much better agreement with observed concentration levels and spatial patterns. These results suggest that use of realistic air inlet boundary conditions is important for accurate CFD simulation of contaminant dispersion in rooms and other enclosed spaces.
Airborne-particles; Air-contamination; Indoor-air-pollution; Indoor-environmental-quality; Air-quality; Air-flow; Gases; Vapors
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American Industrial Hygiene Conference and Exposition, June 2-7, 2001, New Orleans, Louisiana
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University of South Carolina at Columbia, Columbia, South Carolina