On the creation of stagnation points in a rotating flow

We report the results of a numerical study of the creation of stagnation po ints in a rotating cylinder of fluid where both endwalls are rotated. Good agreement is found with previous results where the stagnation points are fo rmed on the care of the primary columnar vortex. Novel phenomena have been uncovered at small aspect ratios where stagnation occurs off-axis directly and the secondary vortex which is created forms a toroid. The case is then considered of a small cylinder placed along the center of the flow and desp ite the qualitatively different boundary condition, the phenomena are found to be robust.