Impact of pulsating vortex dynamics on the thermal performance of a dimpled surface

Abstract

The effect of pulsating flow on the heat transfer inside a dimpled surface is numerically investigated. It has been found that, at Reynolds number of 300, the flow unsteadiness can largely alter the vortex dynamics inside the dimple. Typically, the vortex core is initiated close to the leading edge of the dimple. As the vortex bubble grows, a dual-core vortical flow structure appears due to the strong stretching by the main stream. Compared to results from steady case, the Nusselt number in pulsating flow increases both locally and globally, especially when at a higher pulsation amplitude. Such increase in Nusselt number can be further enhanced with the increase of dimple depth, in which case a stronger and larger vortex occurs above the dimpled surface and the mainstream flow pulsation has more significant influence on the unsteady vortex motion. These numerical findings show that flow pulsation can provide more flexibility and operability in flow control and thermal management.