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We present fluid velocity measurements in a modified Taylor-Couette device operated in the quasi-Keplerian regime, where it is observed that nearly ideal flows exhibit self-similarity under scaling of the Reynolds number. In contrast, nonideal flows show progressive departure from ideal Couette as the Reynolds number is increased. We present a model that describes the observed departures from ideal Couette rotation as a function of the fluxes of an-gular momentum across the boundaries, capturing the dependence on Reynolds number and boundary conditions. [ABSTRACT FROM AUTHOR]

Experiments in a modified Taylor-Couette device, spanning Reynolds numbers of 105 to greater than 106, reveal the nonlinear stability of astrophysically relevant flows. Nearly ideal rotation, expected in the absence of axial boundaries, is achieved for a narrow range of operating parameters. Departures from optimal control parameters identify centrifugal instability of boundary layers as the primary source of turbulence observed in former experiments. By driving perturbations from a series of jets we demonstrate the robustly quiescent nature of quasi-Keplerian flows, indicating that sustained turbulence does not exist. [ABSTRACT FROM AUTHOR]