Annular Flows and Their Interaction with a Cylindrical Probe

A numerical and experimental study is presented of the flow in the gap between concentric rotating cylinders and of its interactions with a cylindrical probe. The radius ratio η of the cylinders is 0.53, 0.44, and 0.35 corresponding to an aspect ratio Γ of 11.36, 7.81 and 5.32. The test cases covered the Taylor number range 2.35 x 10[superscript]6 ≤ Ta ≤ 17.520 x 10[superscript]6, which is above the first critical Taylor number. The cylinders are laid horizontal with the inner cylinder rotating clockwise. The cylindrical probe, which is used to test the intrusiveness of an endoscopic probe on the ensued Taylor vortex flow, is 0.01m in diameter and 0.6m long into the annular region. To the author's best knowledge, no published study has analysed the intrusivity of a cylindrical probe on the flow in concentric rotating cylinders. The flow is herein analysed in the meridional and azimuthal planes. The results from this study further confirm that η, Γ, Ta, and the end-wall conditions are all important parameters that determine the flow regime in the annular gap between concentric cylinders. The results also show wavy vortex flow with aspect ratio Γ < 25 at high Taylor numbers, well beyond the published Taylor number for transition to turbulent flow. In this flow, the vortex centres shift toward the outer cylinder as the centrifugal force due to the rotation of the inner cylinder is greater than the pressure gradient due to the stationary outer cylinder wall. As the η increases, the vortex centres displace more towards the outer cylinder wall. Introducing the cylindrical probe changes the Taylor flow structure. It shifts and distorts the vortices from their original axial position, reduces and elongates the size of the vortices, and reduces the strength of the vortices located between the rotating inner cylinder and the stationary outer cylinder.