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Questions tagged [aerodynamics]

A subset of the [fluid-dynamics] tag concerning primarily forces such as lift and drag generated on bodies as they move through gasses or as gasses move through the body (typically air).

A subset of the tag concerning primarily forces such as lift and drag generated on bodies as they move through gasses or as gasses move through the body (typically air).

964 questions
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What really allows airplanes to fly?

What aerodynamic effects actually contribute to producing the lift on an airplane? I know there's a common belief that lift comes from the Bernoulli effect, where air moving over the wings is at reduced pressure because it's forced to travel further…
David Z
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7 answers

Why do archery arrows tilt downwards in their descent?

In the movies, arrows shot into the air rotate so that during the descent, the arrow head hits ground first. What is the source of this angular momentum? It would seem that the bow string exerts a force directly in line with the arrow.
lamplamp
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Why is jumping into water from high altitude fatal?

If I jump from an airplane straight positioned upright into the ocean, why is it the same as jumping straight on the ground? Water is a liquid as opposed to the ground, so I would expect that by plunging straight in the water, I would enter it…
Conrad C
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3 answers

How can a butterfly dodge the windshield of a fast moving car?

While driving, an unlucky butterfly was about to hit my windshield. But instead of splattering, it sort of glided smoothly upwards across the surface of my windshield. The butterfly was clearly not skillfully dodging the car because the required…
AlphaLife
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4 answers

Why are aerodynamic / streamlined shapes always stumpy at the front?

I'm building an autonomous boat, to which I now add a keel below it with a weight at the bottom. I was wondering about the shape that weight should get. Most of the time aerodynamic shapes take some shape like this: The usual explanation is that…
kramer65
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Why don't helicopters use reaction wheels to counter the main rotor?

As the main title says. I'm finding myself wondering about helicopters. The tail rotor is a vulnerable and key piece of equipment, especially on military helicopters. I know some helicopters instead use two main rotors (for example the KA-50). Why…
Scuba Steve
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47
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2 answers

How can airplanes fly upside down?

I've read many times, including here on this very site that the commonly known explanation of flight is wrong, and that airplanes can fly because the shape of their wings deflects air down. This makes sense, but as far as I can tell it doesn't…
Javier
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44
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3 answers

What is going on in front of and behind a fan?

Why is it that when you drop paper behind a fan, it drops, and is not blown/sucked into the fan, whereas if you drop paper in front of a fan, it is blown away?
GreenAsJade
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42
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4 answers

Slipstreaming - is there a penalty?

When a following vehicle slipstreams close to a vehicle in front, by placing itself in a region of air moving at a similar velocity to the front vehicle, it is afforded a benefit, e.g. improved fuel efficiency. Do the effects from this action…
Trev
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5 answers

Why does a weather vane arrow point in the direction of the wind?

It seems that a weather vane will rotate in order to minimize energy and thus orient itself parallel to the wind. What I do not understand is why it is implied that the weather vane arrow should point in the direction of the wind. I do not…
user391339
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What does a wing do that an engine can't?

This isn't a question of how a wing works -- vortex flow, Bernoulli's principle, all of that jazz. Instead, it's a question of why we need a wing at all. A wing produces lift, but why is that necessary? I got to this by thinking of an airplane at a…
yshavit
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29
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9 answers

Why does the air flow faster over the top of an airfoil?

I understand the common explanation of lift, which describes the airflow over the top of the wing as moving faster than the air below the wing. However, I don't quite understand why the air moves faster. I've read some explanations citing a…
Michael
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Causes of hexagonal shape of Saturn's jet stream

NASA has just shown a more detailed picture of the hexagonal vortex/storm on Saturn: http://www.ibtimes.com/nasa-releases-images-saturns-hexagon-mega-storm-may-have-been-swirling-centuries-1496218 https://en.wikipedia.org/wiki/Saturn_hexagon Is…
Luboš Motl
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23
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8 answers

How to sail downwind faster than the wind?

Recently a group set a record for sailing a wind-powered land vehicle directly down wind, and a speed faster than wind speed. Wikipedia has a page talking about it, but it doesn't explain exactly how it works. I can imagine some configurations, but…
Steve Armstrong
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3 answers

Does a wing in a potential flow have lift?

I have a hard time understanding whether or not a wing placed in a potential flow, assuming there is no viscosity and no friction with the wing, will produce a lift. I've seen several contradictory (to me) versions of what happens in this case, in…
NikiC
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