Fluid dynamics and heat transfer investigations of swirling decaying flow in an annular pipe Part 2: Fluid flow

A review and results from verification and validation was presented in the 1st part of this work. The 2nd part of this study focuses on the fluid dynamics of swirling decaying flows in an annular pipe. Swirling decaying flow is produced using different axial vanes (30°, 45° and 60°). The input parameters of this study are: the Reynolds number and the vane angle. The Reynolds number for this study is varied from 100 to 3000. The decaying nature of swirling decaying flow along the annular duct is investigated. For swirling decaying flows, the swirl number (S) was used to define the local ratio of (v/w) due to the decaying nature of the flow. S was found to be strongly dependent towards Re for fully laminar flows and less dependent towards Re for turbulent flows. An increase in Reynolds number increases the magnitude of the fluid velocity, kinetic energy and eddy dissipation. In the fully laminar regime, an increase in Reynolds number will shift the axial velocity profile towards the outer wall for A∗ = 1.25 to A∗ = 13.75, thus, making it Re dependent. As the Reynolds number increases (turbulent flows), the structure of the profile was found to be independent of Re for all vane angles.