Azimuthal component of the velocity, v_φ, in the z = 0 plane along a radial cut across the flux tube performed at the azimuthal angle φ = π/4. The azimuthal velocities for the models with different l/R have been shifted vertically by an arbitrary constant to ease the comparison. The velocities are plotted for the time at which the maximum of the integrated vorticity occurs in each simulation, indicated within the figure. The horizonal dashed lines denote the v_φ = 0 reference value and the vertical dotted lines denote the limits of the nonuniform boundary layer in each case.