Air entrainment into balcony spill plumes

Abstract

New plume formulations have been developed for assessing air entrainment into thermal plumes that spill over a balcony edge into an atrium void. A simple weak rectangular plume treatment is developed to incorporate the effects of entrainment into plume ends. This is shown to be asymptotic to two dimensional, line plume (near the balcony) and three dimensional axisymmetric plume limits (in the far field). In addition a strong curved plume analysis that also includes the influences of the horizontal momentum of the smoke layer at the balcony edge is developed. The results of the analytical formulations have been compared with Harrison’s new comprehensive experimental data [1] and with CFD predictions from the JASMINE CFD model. It is shown that a virtual line source located a distance approximately three layer depths below the balcony edge provides a reasonably good description of mass fluxes for plumes with and without end entrainment. It is concluded that for practical engineering application, a simple rectangular plume treatment describes the transition from two- to three dimensional flow sufficiently well to be a simple option for the inclusion of end effects.