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Aerodynamics: The force that lifts steel to the sky

Since the dawn of our era, the human race wished to develop methods to face the limitations set by our nature. We didn’t have wings, we couldn’t breathe underwater, yet we sought ways to break through the limitations of what was set to us by nature.


Now we are born in times, where water and air don’t seem that mesmerizingly mysterious as it was centuries ago. Planes and helicopters take off and land successfully over a hundred thousand times per day, and those weigh thousands of pounds. What force of nature lifts such heavy things into the air?

The main part of that force comes from a difference in pressure. Propellers and airplane wings accelerate air above them, decreasing the pressure above.



Image credit https://www.faasafety.gov/gslac/alc/course_content_popup.aspx?cID=104&sID=448


How does pressure change above the wing? Well, according to Bernoulli’s equation, pressure and the velocity of liquids and gasses are inversely proportional to each other.


Here is Bernoulli’s equation: P + ½ 𝜌v2 + 𝜌gh = constant


From this we see that when velocity increases, the pressure decreases to keep the sum of potential energy (𝜌gh), kinetic energy (½𝜌v2), and pressure (P) constant.


So that makes the main goal of the helicopter’s propellers to accelerate the air above to decrease pressure. That force lifts the helicopter straight up, and in order to go forward, helicopters tilt forward.


It is also very interesting to see the shape of helicopter blades and airplane wings. You can see that they are shaped in a way that minimizes the drag force that resists the force that is moving the transport forward.




Nature shaped fish in a way that minimizes the drag force, and it is very similar to the wing shape, the main difference being that fish have both top and bottom curved. People quite often observe nature to create new ideas, and it is interesting to see how the idea of the wing shape comes from fish.

Interesting links and sources:

https://byjus.com/physics/bernoullis-principle/ - more info on Bernoulli’s equation

https://metro.co.uk/2017/03/06/helicopter-magically-appears-to-fly-without-its-blades-6490340/ - Optical illusion, that makes it seem like helicopters are flying without spinning. A little bit unrelated to the article’s theme, but is very interesting to check out.

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