Width of the BL as a function of time for the four simulations mentioned in Sect. 3.3. The width is calculated from the radii of the region where 0.02 <u_ϕ/u_K< 0.8. All four simulation settle down to a BL width of approximately 20 percent of the stellar radius. Simulation A approaches this value more slowly and in a slightly different manner, which is due to the very low resolution of this particular simulation (512 × 512).