Interaction between a buoyancy-driven flow and an array of annular cavities

Abstract

A numerical study is performed to investigate the interaction between a buoyancy-induced flow and an array of annular cavities. The buoyant flow is generated in a vertical annular enclosure with a centrally-positioned finned inner cylinder. Heat is generated within the inner cylinder, and it is convected through the inter-fin cavities and annular enclosure to the outside environment. The results indicate the presence of a twin recirculating bubble in each cavity. At higher Ra, the main flow enters the cavities and removes the recirculating flow. These observations are more pronounced at higher Pr. For more slender and deeper cavities, the recirculating bubbles closer to the finned wall collapse and split into two bubbles. The presence of cavities create a nearly uniform high-temperature zone adjacent to the finned wall. As the fin length is reduced and the cavities become more shallow, this zone shrinks and the main buoyancy-driven flow maintains a closer thermal communication with the finned wall.