Ball moving below the critical speed. Symmetrical Flow.
The extent of the boundary layer, and the general form of the turbulent
wake behind the ball. The wake is slightly broader than the ball, and the
pressure on it immediately behind the ball is lower than on the
front part of the ball (It is the net effect of the pressure on the whole
surface that retards the ball). The wake gradually melts back into the
(The drawing is not to scale : the thickness of the boundary layer is
exaggerated in order to show it.)