Vortex breakdown generated by off-axis bifurcation in a cylinder with rotating covers |
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Authors: | A V Bisgaard M Brøns J N Sørensen |
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Affiliation: | (1) Department of Mathematics, Technical University of Denmark, Matematiktorvet, Building 303, DK-2800 Kongens Lyngby, Denmark;(2) Department of Mechanics, Technical University of Denmark, Niels Koppels Allé, Building 403, DK-2800 Kongens Lyngby, Denmark |
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Abstract: | Summary Vortex breakdown of bubble type is studied for the flow in a cylinder with rotating top and bottom covers. For large ratios
of the angular velocities of the covers, we observe numerically that the vortex breakdown bubble in the steady regime may
occur through the creation of an off-axis vortex ring. This scenario does not occur in existing bifurcation theory based on
a simple degeneracy in the flow field. We extend the theory to cover a non-simple degeneracy, and derive the associated bifurcation
diagrams. We show that the vortex breakdown scenario involving a vortex ring can be explained from this theory, and that the
numerically generated bifurcation diagrams are consistent with the theory. |
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