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The transient evolution of corotating disk flow

K. Marsh
University of Minnesota

S. Abrahamson
Failure Analysis, Inc.

Photo of Ms. Marsh and her experimental apparatus

The fluid spin-up from rest between corotating, shrouded disks was studied experimentally and numerically. Velocity measurements were obtained using LDA and a facility consisting of a stack of 4 coaxial disks separated by solid spacers, 0.063 disk radii thick. The assembly was spun up to 1.05 rad/s in 0.2 seconds. Axial profiles of radial and tangential velocity were measured at three radii. The flow evolution is divided into two phases, boundary layer development followed by core spin-up. Calculations of the first phase assume axisymmetric flow with linear dependence on r. The tangential flow boundary layers are fully developed after ~1/3 disk revolution, and evolve similarly to the layer on a single disk. Geometric confinement induces secondary recirculation in the r-z plane, with negative radial velocities at the midplane. The secondary flow develops slower than the single disk radial pumping and the recirculation strength continues to grow long after the primary flow is stationary. Angular momentum is imparted to the fluid in the boundary layers and is convected into the core by the secondary flow. Core spin-up occurs by conservation of angular momentum as the fluid is convected toward the hub. Consequently, the near-hub flow is last to spin-up. At each radial location, the strength of the secondary recirculation grows until the core flow begins to spin-up.


Last Modified: 2007-09-21 at 12:09:06 -- this is in International Standard Date and Time Notation