  Direct numerical simulations of turbulent Taylor-Couette flow are performed
up to inner cylinder Reynolds numbers of {Re_i=10^5} for a radius ratio of
{\eta=r_i/r_o=0.714} between the inner and outer cylinder. With increasing
{Re_i}, the flow undergoes transitions between three different regimes: (i) a
flow dominated by large coherent structures, (ii) an intermediate transitional
regime, and (iii) a flow with developed turbulence. In the first regime the
large--scale rolls completely drive the meridional flow while in the second one
the coherent structures recover only on average. The presence of a mean flow
allows for the coexistence of laminar and turbulent boundary layer dynamics. In
the third regime the mean flow effects fade away and the flow becomes dominated
by plumes. The effect of the local driving on the azimuthal and angular
velocity profiles is quantified, in particular we show when and where those
profiles develop.
