Measurements of mean flow and turbulence characteristics in high-Reynolds number counter-rotating Taylor-Couette flow

Particle image velocimetry was used for measuring the velocity and Reynolds stress distributions in the latitudinal plane of counter-rotating Taylor-Couette flow at high Reynolds numbers (Re). The ratio of outer to inner cylinder angular velocity, μ, varied between −10.79 and −0.68, and Rei based on the inner cylinder velocity ranged between 2635 and 40 446, substantially extending previously available data. The results were used for examining scaling trends, especially the effects of Re and μ on the mean flow and turbulence statistics. We showed that using a kind of “inner wall” scaling, μ was the primary parameter controlling the normalized profiles of mean velocity, Reynolds stresses, TKE production and dissipation rates. Re effects on the scaled profiles were much smaller. Increasing μ flattened the mean azimuthal velocity profiles in the center of the annulus, increased the radial velocity gradients near the walls, and moved the radial point at which the velocity changed sign towards the outer cylinder. The flow also became more turbulent and a log layer with increasing extent developed near the inner wall. All the Reynolds stress components, along with the TKE production and dissipation rates peaked near the inner wall. Raising μ extended the high turbulence levels deeper into the annulus. At low μ, the stabilizing effect of the outer cylinder kept the flow in the outer regions laminar. Only when the magnitude of the inner cylinder angular velocity equaled or exceeded that of the outer one, the Reynolds stresses remained significant across the entire measurement range, and started increasing also near the outer cylinder. The azimuthal energy spectra confirmed these trends and showed that the changes to turbulence levels occurred at a broad range of scales. Furthermore, for low μ, the instantaneous vorticity fields were dominated by nearly parallel, elongated, counter-rotating vorticity contours, reminiscent of inclined counter-rotating vortex pairs. At high μ, more randomly distributed structures were generated near both walls, and eventually filled the whole annulus.