Figure 8 shows a plot of Reynolds number versus spin parameter with two curves drawn
to show where v ± rω = vc. Above the top curve, both sides of the ball have turbulent
separation. Below the bottom curve, both sides of the ball have laminar separation. Between
the two curves, the v − rω side of the ball has laminar separation while the v + rω side of
the ball has turbulent separation. We emphasize that the two curves shown in figure 8 are
merely approximations of where transitions between laminar flow and turbulent flow exist.
Such transitions are certainly not instantaneous at a specific, critical speed. Figure 8 provides
a rough idea of where the three cases exist.