Experimental Contradiction of Bernoulli's Principle
Scientists cannot confirm Bernoulli's Principle by empirical
experimentation. Even if they could build a Bernoulli donut and rig up
some pressure and velocity sensors inside it, it would still need some
sort of fan inside the donut to make the fluid move around inside it.
And a fan is not a legal part of a Bernoulli donut. Since Bernoulli
based his conclusion on a device that cannot operate and does not even
exist, I conclude Bernoulli's Principle does not necessarily apply to
anything real. On the other hand, I can actually build all kinds of real
devices that contradict many scientists' interpretation of Bernoulli's
Still, scientists, have had no particularly good explanation for how
come fast fluids sometimes have low pressure. Bernoulli's Principle
seems to use all the same words and arrive at an agreeable conclusion so
scientists use it, often without thinking it through. In order to make
it fit better, physics books generally present a partial drawing - just
one section of fluid flowing from a large pipe into a smaller pipe. The
illustrations do not show the complete donut nor to they show a fan that
might motivate the fluid to flow. In actual practice, if I want to move
fluid from one pipe to another, I need more pressure upstream, no matter
what size pipes I used. Otherwise, a Calabash pipe might just be able to
puff away all by itself.
Scientists use Bernoulli's Principle as a general catchall to explain
how high velocity fluids have low pressure. Here are some simple
experiments you can run to show that Bernoulli's Principle simply does
The garden hose experiment
Turn on the faucet and let water squirt out of the end of a garden
hose. If Bernoulli's Principle applied, the faster flowing fluid inside
the garden hose would cause it to flatten out into a garden strip.
Instead, it either stays the same shape or even bulges out a bit.
Bernoulli's Principle does not apply.
The moving jar experiment
Take an empty jar and put the lid on it so as to seal in some air.
Now get in a car and take the jar for a fast ride on the highway.
Scientists say that Bernoulli's Principle predicts that fast moving air
has lower pressure. Do you really think the pressure in the jar changes
when you go fast?
The hand-out-the-car-window experiment
Note: be very careful if you run this experiment that you do not
injure your hand and/or arm. When you are on a highway, moving fast, and
at safe distance from other cars or objects near the side of the road,
extend your hand out the window and make various shapes into the wind.
Some scientists say that an airplane wing
that is curved on top and flat on the bottom rises since the air must
flow faster over the top. This is incorrect. Notice that a flat hand
wants to rise of fall depending if it aims up or down. Also notice that
a curved hand with a round top and a flat bottom (the airfoil shape)
does not particularly want to rise.