We experimentally and numerically investigate the angular momentum transport in turbulent Taylor-Couette flow for independently rotating cylinders at a small radius ratio of $\eta =0.357$ for various shear Reynolds numbers $\left(4.5\times {10}^3\le {\text{Re}}_S\le 1.2\times {10}^5\right)$ and ratios of angular velocities $\left(-0.5\le \mu \le 0.2\right)$. The momentum transport in terms of the pseudo-Nusselt number ${\text{Nu}}_{\omega }$ does not show a pure power law scaling with the forcing ${\text{Re}}_S$ and features nonconstant effective scaling between $1.3\times {10}^4\le {\text{Re}}_S\le 4\times {10}^4$. This transition lies in the classical turbulent regime and is caused by the curvature-dependent limited capacity of the outer cylinder to emit small-scale plumes at a sufficient rate to equalize the angular momentum in the bulk. For counter-rotating cylinders, a maximum in the torque occurs at ${\mu }_{max}=-0.123\pm 0.030$. The origin of this maximum can be attributed to a strengthening of turbulent Taylor vortices, which is revealed by the flow visualization technique. In addition, different flow states at ${\mu }_{max}$ concerning the wavelength of the large-scale vortices have been detected. The experimental and numerical results for the Nusselt number show a very good agreement.

• Received 29 November 2018

DOI:https://doi.org/10.1103/PhysRevFluids.4.084605