Instability thresholds of rotor-stator flows with axial throughflow.

Instability thresholds of rotor-stator flows with axial throughflow. This experimental study deals with the stability of rotor-stator flows subjected to an axial inward or outward throughflow. Stability diagrams have been established by flow visualizations according to the rotational Reynolds number Re and to V-* the dimension less axial velocity in the radial gap between the rotor and the shroud. Three aspect ratios G of the cavity have been considered to take into account both Batchelor type of flows with separated boundary layers and torsional Couette type of flows with joined boundary layers. We show then the influence of rotation, geometry and most of all of the superimposed throughflow on the appearance and disappearance thresholds of instabilities. Some new structures have also been observed to be compared to the case of a closed cavity. (c) 2006 Academie des sciences. Publie par Elsevier SAS. Tous droits reserves.