A Numerical Study of Worker Exposure to a Gaseous Contaminant: Variations on Body Shape and Scalar Transport Model

Abstract

Three-dimensional computational fluid dynamics simulations are used to investigate the distribution and level of contaminant concentrations in the true breathing zone (at the nose and mouth) when toxic airborne contaminants are released within an arm's length in front of the worker who has his back to the airflow. The effects of different body shapes on fluid flow and concentration patterns around the body in a wind tunnel were evaluated and clarified that a sharp body or a block may not be a good surrogate for the human form in consideration of occupational and environmental health studies. The comparison of the concentration field calculated with the Eulerian and Lagrangian methods revealed that the Eulerian method has a more diffusive nature than the Lagrangian method. The concentrations at different locations were also compared to determine the optimum sampling location. It was found that the concentration at the breathing zone may be significantly different from the one at the chest area. The influence of the heat flux from the body was studied at two different Reynolds numbers. Predictions indicate that the heat flux may have a significant impact on exposure especially when the convection induced by buoyancy dominates the flow.

Effects of heating, breathing, hair style, posture, and air velocity on breathing zone concentrations for an anthropometrically-correct manikin in a wind tunnel

“…Studies considering the effect of body geometry on breathing zone concentrations (Brohus, 1997;Li et al, 2003;2005) were not done experimentally, however, they were done numerically using CFD. For example, Li et al (2005) found that rounded body shape (closest approximation to human body) resulted in much lower concentration levels than over simplified bodies.…”

“…Studies considering the effect of body geometry on breathing zone concentrations (Brohus, 1997;Li et al, 2003;2005) were not done experimentally, however, they were done numerically using CFD. For example, Li et al (2005) found that rounded body shape (closest approximation to human body) resulted in much lower concentration levels than over simplified bodies. While, studies considered the use of a manikin holding a source in its hands (Guffey, et al 2001;Kim and Flynn, 1992;George et al, 1990;Welling et al, 2001) found dissimilar results when the source located within wake zone than outside the wake zone.…”

“…As will be discussed later, manikins used in CFD simulations have been spheres, rectangles, sharp edged simplified shapes, or cylinder shaped models. The influence of manikin geometry on the flow pattern and contaminant dispersion at the breathing zone is still undergoing research (Brohus, 1997;Li et al, 2003;2005). Issues which need careful consideration are those of the choice of anthropometric measures, plus the mechanical and geometrical representation of the human being (joints and body parts).…”

Tracer Gas Exposure of Human Subjects Doing Simulated Work at a Benchtop Enclosing Hood in a Wind Tunnel

“…For instance, they use different levels of velocities and different experimental setups. A static simple manikin without arms, built from basic geometric forms, was used in this study; hence, results can be compared with simulations studies with similar figures (Karaismail, 2011;Li, 2005).…”

“…Worker exposure and body shape were studied numerically by Li et al (2005). They compared the Eulerian transport model and the Lagrangian trajectory tracking method.…”