Streak-line motion during steady and unsteady axisymmetric vortex breakdown

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Abstract
Numerical calculations of vortex breakdown generated within a closed circular cylinder by rotation of one of the end walls have been performed. The solutions are used to compute steady streak-line patterns for dye introduced both symmetrically and asymmetrically about the symmetry axis upstream of the breakdown bubble. Beginning from such a steady state, the end-wall angular speed is impulsively increased and the asymmetric streak-line pattern is observed during a portion of the subsequent period of unsteady flow.