Flow between rotating finite disks with a closed end condition studied by heterodyne photon-correlation

We have investigated experimentally the swirling flow between a stationary and a rotating disk with fixed closed end. In order to perform velocimetry measurements we implemented a heterodyne photon-correlation setup and obtained the three components of the velocity field at different positions along the gap between the disks. We compared the results for two different Reynolds numbers with a numerical solution of the similarity equation, to investigate the relation between the finite and infinite disk solution, theoretically studied by Brady & Durlofsky (1987). For the measurements performed at Re below the critical Reynolds number Re-c = 80, we found that the two solutions agree very well near the axis of rotation. Above Rec we found that this quantitative agreement no longer holds, but the flow qualitatively resembles the Batchelor solution, with two boundary layers and a core rotating as a solid body. Our results validate the theoretical prediction for closed-end finite disk flow.