Fluid Dynamics
The study of fluids in motion"¤ Bernoulli's Principle
Bernoulli's Principle simply states that
where the velocity
of a fluid is high, the pressure is low, and where the
velocity is low, pressure is high."
(Giancoli 270)
This is why airplanes can fly, and it is also used by marine mammals to move in the water.
Let's picture the cross-section of a wing (or flipper):
The upper surface is more curved, while the bottom surface is more flat. Because of this, the fluid (air or water) that's flowing over the top of the wing is covering a larger distance than the fluid flowing under the wing, and this means that the fluid flowing over the wing has to move faster than the fluid flowing under it.
Which brings us to Bernoulli's Principle: since the fluid on top is moving faster, its pressure is lower, and since the fluid on bottom is moving slower, it's pressure is higher.
And what happens if the air under a wing has higher pressure than the air over it? The wing will be pushed up! This is how airplanes (and marine mammals) achieve lift, thanks to the phenomenon described by Bernoulli's Principle.
(Giancoli 270)
¤ Drag
¤ Types of Flow