Planar Rotating Flow Upstream, Midstream, and Downstream Regions of an Obstruction and Partial Shroud Opening Driven by Enclosed Corotating Disks

This work investigates the planar profiles of a rotating flow in a model corotating system. The simplified model is 2.25 times the size of a hard disk drive (HDD) and features an arm, disks, and hub. The flow was driven by a pair of corotating disks mounted in a shrouded enclosure with a partial shroud opening. We experimentally studied the flow in the locally planar inter-disk region when obstructed by the arm. Two-dimensional average velocity fields were measured at five planes using particle image velocimetry, with an undistorted flow view ensured by refractive index matching. In areas of solid-body rotation downstream of the arm, when inserted closer to the hub, it contracts while fully established. However, it spans a broader area when inserted closer to the disk edge but becomes fully established further downstream. Locally accelerated flows were observed in the narrowed space between the hub and the arm, with their magnitude exceeding the local disk velocity for deeper insertion angles. Contrary to the axisymmetric case, upstream of the insertion, the flow decelerates toward the shroud opening, influenced by axial velocity gradients in both the radial and circumferential velocity components. An indication of a secondary flow exists in the mid-plane upstream and downstream of the arm insertion as the flow moved inward in the hub direction influenced by the cross-stream centrifugal flow in the inter-disk region. Midstream of the insertion, flow disturbances result from momentum exchange between the arm wake and the shroud opening, driven by viscous diffusion terms. The flow exhibits different patterns in the inter-disk region upstream, midstream, and downstream of the obstruction as well as the narrow channel between the hub and the arm all of which are caused by geometric variations and the arm insertion, generating wakes and interacting with the inflow from the shroud opening.