The flow between concentric rotating cylinders shows in some parameter regions properties as they are known in thermal convection (e.g. a linear instability of the laminar profile for rotating inner cylinder) and in other properties also found in shear flows like pipe flow (e.g. turbulence despite a linear stability of the laminar profile). Using the analogy to heat flux in Rayleigh-Bénard convection we plan to compute and analyze the total torque and its scaling in the different parameter ranges. In the first period of the project, a numerical code was established that allows computations at Reynolds numbers up to 30,000 and that reproduces many of the experimental findings. In particular in the case of counterrotating cylinders it was found unexpectedly that there is a maximum in torque and a instability of the boundary layer at the outer cylinder. In the second period of the project we will further explore the mechanism proposed to explore these findings. We will also explore the limit of rotating plane Couette flow, where connections to other shear flows and their spatial and temporal dynamics of localized turbulent puffs and stripes are possible. In addition to direct numerical simulations we will also rely on experiments in Cottbus, Göttingen and Twente.