INTERMITTENCY IN THE CLOSED FLOW BETWEEN COAXIAL COROTATING DISKS

We report an experimental study of the swirling flow generated in the gap between two coaxial corotating disks in an enclosed geometry, i.e. when the flow is enclosed in a cylindrical vessel. In this situation the angular momentum generated by the disk rotation tends to concentra te in a strong axial vortex. In the range of high Reynolds numbers exp lored, we show that two regimes exist, depending on the disk angular v elocities. When they rotate at quite different speeds, we observe very intermittent fluctuations of the axial vorticity associated with quas i-periodic vortex bursting, whereas at comparable rotation rates a mor e stable vorticity structure is observed. We describe these regimes us ing global measurements; we also show: using local velocimetry, how th e structure of the flow affects the small scale turbulence. (C) Elsevi er, Paris.