Development of an Axisymmetric Thermal Plume between Vertical Plates

Abstract

This investigation analyses the turbulent structure of a thermal plume created by a heated disk, evolving between vertical plates. The objective of the study was to understand the development mechanisms of this buoyancy driven flow. The analysis of the average and the fluctuating fields of the temperature as well as the flow visualisation show the existence of three different zones. The first zone of the plume air feeding was characterized by the thermal profiles in three extrema structures. These extrema disappear in the second zone where the profiles present on maximum. In the last zone, the profiles are flattened and self-similar. Thus, the turbulence was fully developed. A flow visualisation show that the vertical channel around the hot disk affects the flow structure plume and causes the appearance of a new zone at the system entrance. This supplementary zone characterizes by the development of the two rotating rolls in the vicinity of the hot source. The skewness and flatness factors of the temperature fluctuations show that the latter have a nearly Gaussian distribution in the most turbulent regions of the flow (in the region where the turbulence was fully developed), but that deviates gradually from the Gaussian distribution in the other region.