A numerical investigation into the flow field around a worker positioned by an exhaust opening.

A numerical investigation has been made into the flow behaviour near a worker in the vicinity of an exhaust opening. The flow field is that induced by the withdrawal of air through the exhaust opening and hence a wake forms between the worker and the opening. Both laminar and turbulent flow regimes are considered. The numerical technique adopted is the control volume, finite-difference method with the k-epsilon model used to model the turbulent flow. The problem has been considered in two dimensions in order to gain a greater understanding of the flow behaviour but the numerical method adopted could be extended to investigate three-dimensional effects. An investigation is made into the effects upon the flow of the distance of the worker from the exhaust opening for different operating conditions. The results show that if the worker is close to the exhaust opening then the flow is steady and a small area of recirculating flow exists in the wake of the person. However, if the worker is situated some distance away from the opening then the flow field is unsteady with vortex shedding occurring in the persons wake.

An investigation into the effects of breathing upon the aspiration efficiency of the human head.

A mathematical investigation is undertaken into the effects of the breathing pattern upon the aspiration efficiency of the human head. It is assumed that all the fluid inhaled by the head is subsequently exhaled and that the two stages of the breathing pattern last for an equal length of time. The particles are taken to be spherical and are assumed to be suspended without sedimentation in an ideal fluid which is flowing towards the head. A model for the head is proposed and the case of breathing through the mouth is studied. An analytical approach is adopted to determine the behaviour of the particles near the mouth, and the sampling efficiency of the head is investigated. Results are obtained for various situations, and comparisons are made with existing experimental results. It is shown that, in many cases, the effect of the breathing pattern is insignificant but for normal human breathing rates, it becomes significant as the velocity of the flow increases.