EFFECTS OF STACK HEIGHT AND POSITION ON POLLUTANT DISPERSION IN BUILDING WAKES

Abstract

Selected smoke visualization and ground level concentration data are presented and discussed for the case of neutrally buoyant plumes influenced by a squat-building wake. The plumes considered were emitted from low stack height sources at various positions atop the building and were studied to ten building heights downstream. The plume smoke visualizations contribute to a method of qualitatively estimating the ground level concentrations with regard to the overall visualized plume behavior. The quantitative ground level concentration data support the qualitative visualization results and show that stack position can affect local ground concentrations by a factor of six and, in addition, the stack height and position parameters, which determine the efflux point of release in the building wake flow, are strongly interrelated in determining the ground level concentrations. In particular, for a building oriented normal to the oncoming flow, roof-top emissions at the trailing building edge produce the highest ground concentrations, whereas for a stack height equal to 1.5 times the building height, the largest ground concentrations occur for the case where the stack is positioned at the leading roof-top edge of the building.