Finite-size effects may be characterized by axial profiles of the angular velocity Ω measured at the mid-gap (r = (a + b)/2) in the Twente experiment. In this example, the cylinder Reynolds numbers are Re₁ = 1.0 × 10⁶ and Re₂ = 0 (outer cylinder stationary). The global torque measurements are taken for 0.22 < z/L < 0.78 with the top boundary of these measurements indicated by the dashed line at z/L = 0.78. The resolution of the laser-doppler anemometry prohibits measurements of the angular velocity in the boundary layer near z/L = 1 where Ω = Ω₂ = 0, in this case.