a sailboat moves
over sails separates on to the windward (high pressure) and leeward (low
pressure) sides. The turbulence is created at the leading trailing edges.
The difference between the positive and negative pressure creates the
aerodynamic force that pushes the sail forwards and moves the boat along.
This force is is sufficient to overcome the resistance of water, hull,
sails and rigging.
The sails must always be adjusted to make maximum use of the speed and
direction of apparent wind.
is the real wind experienced by a static object
is the wind experienced by a moving object