How
did studying the speed of blood flow and blood pressure help us
design airplanes?
Dutch-Swiss
mathematician and scientist Daniel Bernoulli (born on this date in
1700) observed and tested the flow of fluids, that is, liquids and
gases. He tried to understand how the speed of blood flow in veins
and arteries related to the pressure it exerts. To find out, he
punched holes in pipes and inserted vertical straws, and then he
measured the height to which the fluid rose up the straw. Here's what
he found:
The
quicker the motion of fluid in the pipe, the less the pressure
exerted, and the lower the level of fluid in the vertical straw. When
fluid moves at lower speeds, it exerts more pressure and pushes up
into the straw to a higher level. Bernoulli was able to devise
mathematical equations to match his experimental findings.
Here
is an animation you can manipulate to see the difference in
speed-of-motion (velocity) and pressure, depending on the shape of a
pipe. Be sure to “grab” and “drag” the little yellow boxes to
change the shape—then check out the graphs below that show the
relation of the speed to the pressure. Make really exaggerated shapes
with a really narrow mid-portion, for example, and one very wide end,
to see the results most clearly.
Apparently,
for more than a century, based on Bernoulli's findings, doctors
measured blood pressure by sticking point-ended glass tubes directly
into people's arteries. Eeek! I feel glad that a less invasive and
painfully method was eventually invented!
Later
on, airplane wings were designed to take advantage of Bernoulli's
principle—with the air moving more quickly over the top of the
wing, creating less pressure—and therefore providing lift as the
greater pressure under the wing pushes the wing up.
Bernoulli's
fluid mechanics have been used in many other ways, of course; also,
Bernoulli made other contributions to mathematics, statistics, and
science. So hooray for Bernoulli!
Also
on this date:
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