Buoyancy-driven exchange flow between two adjacent building zones connected with top and bottom vents

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  • We examine the buoyancy driven flow between two adjacent building zones separated by top and bottom vents with and without a source of buoyancy. In the absence of a source, by opening the vents, the pressure difference between the two zones drives the exchange flow. When there is an isolated source of buoyancy, two distinct flow regimes are defined: a ventilation-dominated regime in which the flow that is generated by the initial temperature difference, and a source-dominated regime in which the flow is principally governed by the source. Here, we restrict attention to the former case. Thus in each zone our analytical model assumes a horizontal interface that separates the upper layer, which is comprised of fluid having the initial density of the light zone, from the lower layer, comprised of fluid whose density is larger than that of the light zone. The transient evolution of such interfaces along with the stratification and buoyancy in each zone are predicted. Attention is focused on the influence of the effective area, source buoyancy flux and the time during which the source is switched on. Because the interface elevations change significantly at early times, a non-monotonic behavior is predicted for the evolution of stratification in the light zone. We also find that the terminal stratification and buoyancy in both zones are not impacted by the number of connecting vents; however, this number has a strong influence on how quickly steady state is achieved. Similitude laboratory experiments help to corroborate key predictions.

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    Article (Published)
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    Attribution-NonCommercial 4.0 International