Turbulent and Laminar Flow
Laminar: Smooth, linear
Turbulent: Eddies
Turbulence happens when two fluids (liquids or gasses) with different
densities are flowing past each other.
Example:
Cigarette smoke
Airplanes are designed to have flow be laminar:
When the landing wheels of an airplane drop, it gets noisy: the
landing gear is causing turbulence in the underpart of the jet.
Golf Ball Dimples:
Softball and Baseball players are experts at predicting the effect of
turbulent flow (if they can throw a curveball, or hit one!)
Fuzz on the ball makes a turbulent wake. Position of stitches
controls the position and magnitude of the turbulent wake.
From a NASA web site:
Baseballs and softballs are examples of sports
projectiles. The air flow
around the ball is science that must be mastered by
every baseball or
softball pitcher. The air flow around a smooth ball is
much different than
the air flow around a ball with stitches. See the
diagrams below. In the
flight of a smooth ball the air molecules travel around
the ball to the
back where they meet and mingle and combine to push the
ball forward. The
pressure behind the ball is less than the pressure in
front. When the ball
has stitches as in a baseball or softball, turbulence
occurs where the
stitches are. The turbulence causes the air to stick to
the ball just a
little longer and reduces the wake (as in a boat's
wake) which reduces
drag. These stitches can also change the direction of
the ball. A good
pitcher uses the spin and the stitch alignment to throw
curve balls.
According to an apocryphal story, Werner Heisenberg was
asked what he would ask God, given the opportunity.
His reply was: "When I meet God, I am going to ask him two questions:
Why relativity? And why turbulence?
I really believe he will have an answer for the first."