Control of vortex breakdown in a closed cylinder with a rotating lid |
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Authors: | Bo Hoffmann Jørgensen Jens Nørkær Sørensen Nadine Aubry |
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Institution: | 1. Department of Mechanical Engineering, Fluid Mechanics Section, Technical University of Denmark, Building 403, 2800, Lyngby, Denmark 2. Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA, 15213-3890, USA
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Abstract: | The flow within a closed cylinder with a rotating lid is considered as a prototype for fundamental studies of vortex breakdown.
Numerical simulations for various parameter values have been carried out to reproduce the known effect of a thin rotating
rod positioned along the center axis as well as analyze the influence of local vorticity sources. As expected, the results
show that the breakdown bubbles in the steady axisymmetric flow can be affected dramatically, i.e., fully suppressed or significantly
enhanced, by rotating the rod. The main contribution of this article is to show that the observed behavior can be explained
by the vorticity generated by the rod locally near the rotating lid and near the fixed lid, as analogous behavior is caused
by the introduction of local vorticity sources in the flow without a rod. Moreover, we describe the influence on the breakdown
bubbles of the vorticity sources by an analytical model. In addition to improving our understanding, this finding should also
open the door to other types of flow control devices capable of generating localized vorticity. |
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