Precessing vortex breakdown mode in an enclosed cylinder flow

The flow in a cylinder driven by the rotation of one endwall for height to radius ratios around three is examined. Previous experimental observations suggest that the first mode of instability is a precession of the central v ortex core, whereas a recent linear stability analysis to general three-dim ensional perturbations suggests a Hopf bifurcation to a rotating wave at lo wer rotation rates than those where the precession mode was first detected. Here, this apparent discrepancy is resolved with the aid of fully nonlinea r three-dimensional Navier-Stokes computations. (C) 2001 American Institute of Physics.