  We investigate the quasi two-dimensional Taylor-Couette system in the regime
where the radius ratio is close to unity - a transitional regime between three
and two dimensions. By systematically increasing the Reynolds number we observe
a number of standard transitions, such as one from the classical Taylor vortex
flow (TVF) to wavy vortex flow (WVF), as well as the transition to fully
developed turbulence. Prior to the onset of turbulence we observe intermittent
burst patterns of localized turbulent patches, confirming the experimentally
observed pattern of very short wavelength bursts (VSWBs). A striking finding is
that, for Reynolds number larger than the onset of VSWBs, a new type of
intermittently bursting behaviors emerge: burst patterns of azimuthally closed
rings of various orders. We call them ring-burst patterns, which surround the
cylinder completely but remain localized and separated by non-turbulent mostly
wavy structures in the axial direction. We use a number of quantitative
measures, including the cross-flow energy, to characterize the ring-burst
patterns and to distinguish them from the background flow. The ring-burst
patterns are interesting because it does not occur in either three- or
two-dimensional Taylor-Couette flow: it occurs only in the transition, quasi
two-dimensional regime of the system, a regime that is less studied but
certainly deserves further attention so as to obtain deeper insights into
turbulence.
