Control of vortex breakdown in a torsionally driven closed cylinder by addition of swirl using a small disk
Résumé
This paper discusses results of a new experimental approach to control vortex breakdown in a confined cylindrical vessel with a rotating top endwall. The aim was to determine the effectiveness of adding co-rotating and counter rotating swirl near the axis of rotation using a small disk located in the bottom endwall. Initial results, with only the top end rotating, were satisfactorily validated against classical data from the literature. Results of the vortex breakdown onset, using this new non-intrusive approach, have revealed that co-rotation of the smaller disk precipitates vortex breakdown formation while counter rotation delays the onset of the breakdown phenomenon. It has also been shown that co-rotation increases the bubble radial and axial dimensions while shifting the bubble in the upstream direction. By contrast, counter rotation tends to reduce the size of the bubble, or completely suppress it, while shifting the bubble in the downstream direction.