Extent of the Reverse Flow Wake Region Produced by a Body in a Uniform Flow Field

Welling, Irma; Kulmala, Ilpo; Andersson, Ing-Marie; Rosén, Gunnar; Räisänen, Jouni; Mielo, Timo; Marttinen, Keijo; Säämänen, Arto; Niemelä, Raimo

doi:10.1080/10473220119185

Cited by 7 publications

(9 citation statements)

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“…Box 12313, Research Triangle Park, NC 27709, USA. E-mail: richmond-bryant.jennifer@epa.gov Stokes methods (RANS) (e.g., Gadgil et al 2003;Welling et al 2001;Lan and Viswanathan 2001;Kulmala 2000;Flynn and Sills 2000). This choice may be related to the availability of RANS models in commercial CFD packages.…”

Section: Introductionmentioning

confidence: 98%

Considerations for Modeling Particle Entrainment into the Wake of a Circular Cylinder

Richmond-Bryant

Eisner

Flynn

2006

Aerosol Science and Technology

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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 ∼ ε 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.

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Section: Introductionmentioning

confidence: 98%

Considerations for Modeling Particle Entrainment into the Wake of a Circular Cylinder

Richmond-Bryant

Eisner

Flynn

2006

Aerosol Science and Technology

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“…To counter these concerns, this study aimed to test the impacts of realistic environmental factors on the capture efficiency and protection efficiency of an exterior hood. Though several studies (Ljungqvist, 1979;Kim and Flynn, 1992;Johnson, Fletcher, and Saunders, 1996;Welling, Andersson, Rosen, Räisänen, Mielo, Marttinen, and Niemelä, 2000;Welling, Kulmala, Andersson, Rosen, Räisänen, Mielo, Niemelä, 2001;El-Sotouhy, 2008) have shown the presence of human subjects to significantly alter air currents, no other capture efficiency study has included the presence of human subjects. Only one study (Kasberger, 2012) has included a manikin.…”

Section: Problem Statementmentioning

confidence: 99%

“…Guffey and Barnea (1994) found, using a tracer gas, that contaminant concentrations in the breathing zone were higher with the presence of a manikin than samples taken in the same locations without the presence of a manikin. Welling, et. al.…”

Section: Cross Draftsmentioning

confidence: 99%

“…The effects of body movements on breathing zone concentrations have previously been considered in free field systems (Ljungqvist, 1979;Kim and Flynn, 1992;Welling et. al., 2000;Welling et. al, 2001;Guffey et.…”

Section: Chapter 6 : Manikin Movements Introductionmentioning

confidence: 99%

“…Though several studies (Ljungqvist, 1979;Kim and Flynn, 1992;Johnson, Fletcher, and Saunders, 1996;Welling, Andersson, Rosen, Räisänen, Mielo, Marttinen, and Niemelä, 2000;Welling, Kulmala, Andersson, Rosen, Räisänen, Mielo, Niemelä, 2001;El-Sotouhy, 2008;Lewis, 2010) have shown the presence of a worker to significantly alter air currents, only one study (Kasberger, 2012) considered the effects the worker has on the capture efficiency of an exterior hood. The Kasberger study did not consider the actual effects the manikin had on the effectiveness of the capturing system…”

Section: Introductionmentioning

confidence: 99%

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Effects of a Manikin on the Capture Efficiency and Protection Efficiency of a Small Rectangular Hood

Geissler¹

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The primary indicator of capturing hood effectiveness is widely assumed to be the "capture velocity" measured normal to the center of the hood face, at the furthest location of the contaminant source. The velocity required at this distance (Vx) is thought to correspond to the appropriate flow (Q) required to capture the contaminant. The adequacy of Vx as a surrogate for hood effectiveness has long been poorly understood and has been little studied. Few considerations of potentially disruptive parameters, such as draft velocity, hood orientation, and operator presence are made during the design phase. In this study, an anatomically correct heated, breathing, and moving manikin was used as a surrogate for a human hood operator. Velocity profiles of the capture envelope were obtained by particle image velocimetry (PIV) at three orientations (0˚, 90˚, 180˚), with respect to the cross drafts (30, 60, and 120 fpm) generated inside a large wind tunnel. The capturing hood fan speed was set to maintain the Q of nominal Vx values of 50, 100, and 200 fpm, as measured 11 inches away from the hood face, in a controlled environment. A condensation particle counter (CPC) was used to compare the capture efficiency and protection efficiency of the rectangular hood with the traditional, expensive, and time-consuming tracer gas method. Salt aerosols and Freon 134-A were released, at separate occasions, 11 inches away from the hood face. Measurements were taken within the duct (Cduct) and between the mouth and nose (CBreathingZone) of the manikin. Duct measurements (Cduct100) were also collected when the contaminant was directly fed into the duct, and breathing zone measurements were also conducted with the hood turned off (CBreathingZone100). The capture efficiency results of each method were compared, and no significant difference between the methods was found. With the CPC method established as a viable method, studies were conducted to test the effects of operator presence, movement, hood orientation, and cross drafts under the same conditions as the PIV study. All effects, except for manikin movement, were found to have a significant effect on hood performance. Manikin movement did, however, have a significant effect on contaminant concentrations within the breathing zone of the operator.

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The dynamics of the body motion induced wake flow and its effects on the contaminant dispersion

Gao

2014

Building and Environment

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Extent of the Reverse Flow Wake Region Produced by a Body in a Uniform Flow Field

Cited by 7 publications

References 0 publications

Considerations for Modeling Particle Entrainment into the Wake of a Circular Cylinder

Considerations for Modeling Particle Entrainment into the Wake of a Circular Cylinder

Effects of a Manikin on the Capture Efficiency and Protection Efficiency of a Small Rectangular Hood

The dynamics of the body motion induced wake flow and its effects on the contaminant dispersion

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