Dynamical System Analysis on the Onset of Recirculating Flow Region Associated with Vortex Breakdown

摘要

In this study, the onset of axisymmetric vortex breakdown in a closed cylinder is extensively investigated numerically by solving the incompressible axisymmetric Navier-Stokes equations. A longitudinal vortex tube, which is generated around the center axis of the cylinder, goes to burst after the radial expansion of the vortex tube and the appearance of a pair of stagnation points on the axis, by which a recirculating flow region is bounded. Such process is examined from the aspects of the velocity profile along the axis and the eigensystem of the velocity gradient tensor around the stagnation points, varying the Reynolds number and the aspect ratio of the cylinder.