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Considerations for modeling particle entrainment into the wake of a circular cylinder.

Authors
Richmond-Bryant-J; Eisner-AD; Flynn-MR
Source
Aerosol Sci Tech 2006 Jan; 40(1):17-26
NIOSHTIC No.
20029194
Abstract
The objective of this work is to evaluate the performance of the steady state Reynolds Averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) models for estimating concentration of low Stokes number aerosols (Stk = O(10-4)) in the wake of a bluff body. These simulations are compared with experimental data. In the simulations and experiments, particles are released upstream of the body and convected downstream, where some are entrained into the wake. The air velocity is computed using a steady state renormalized group k ~ e model. Lagrangian particle trajectory simulations are performed in conjunction with each airflow model to calculate concentrations. The experiments are performed in an aerosol wind tunnel in which phase Doppler velocimetry measurements are obtained the velocity field and for aerosol concentration. The RANS model yields a wake concentration deficit that extends downstream past x/D = 10, while the experiments produce elevated concentrations immediately downstream of the near wake. It is postulated that the concentration peak is at least in part attributed to particle interaction with the boundary layer by the following mechanism. Particles are transported into the boundary layer by turbulent diffusion, turbophoresis, and/or inertial forces. Particles then separate from the cylinder with the airflow and travel in a sheath around the periphery of the near wake to converge at the downstream edge of the near wake. Underestimation of the wake concentration by the RANS model is potentially due to inadequacy in the boundary layer approximation used in the model.
Keywords
Particulates; Airborne-particles; Air-contamination; Gravimetric-analysis; Aerosols; Aerosol-particles; Computer-models; Models
Contact
University of North Carolina, Department of Environmental Sciences and Engineering, Chapel Hill, North Carolina, USA
CODEN
ASTYDQ
Publication Date
20060101
Document Type
Journal Article
Funding Amount
719405
Funding Type
Grant
Fiscal Year
2006
NTIS Accession No.
NTIS Price
Identifying No.
Grant-Number-R01-OH-007363
Issue of Publication
1
ISSN
0278-6826
Priority Area
Research Tools and Approaches: Exposure Assessment Methods
Source Name
Aerosol Science and Technology
State
NC
Performing Organization
University of North Carolina Chapel Hill
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