ABSTRACT
The simplest system for an analysis of the transport of contaminants by ventilation is convective transport along the streamlines. It can generally be assumed, in regions with well-defined air flow fields, that the settling velocity of contaminants is negligible, which implies that gravitation plays an inferior role. Owing to the fact that the streamlines are closed, there is no convective removal of contaminants emitted within the vortex region. It is only turbulent diffusion within the vortex that causes removal of the contaminants. Transport due to turbulent diffusion does not increase in proportion to the vortex velocity but is changed at a slower rate. If for a certain ventilation rate of flow there is a vortex region within which a contaminant is emitted and this rate of flow is doubled, the concentration of the contaminant in the vortex region is not halved; it drops to somewhere between the original value and half this value.
