Logarithmic Boundary Layers in Strong Taylor-Couette Turbulence

We provide direct measurements of the boundary layer properties in highly turbulent Taylor-Couette flow up to Re = 2 X 10(6) ( Ta = 6.2 X 10(12)) using high-resolution particle image velocimetry and particle tracking velocimetry. We find that the mean azimuthal velocity profile at the inner and outer cylinder can be fitted by the von Karman log law u(+) = 1/kappa lny(+) + B. The von Karman constant kappa is found to depend on the driving strength Ta and for large Ta asymptotically approaches kappa approximate to 0.40. The variance profiles of the local azimuthal velocity have a universal peak around y(+) approximate to 12 and collapse when rescaled with the driving velocity (and not with the friction velocity), displaying a log dependence of y(+) as also found for channel and pipe flows.