Vortex shedding

[flynfrog]

Vortex gets thrown around here a lot. This is how they happen explained simply with video. The youtube channel is great for wasting time as well.
[youtube]http://www.youtube.com/watch?v=ZauGjgZ0rBQ&NR[/youtube]

[Rennsport_helgi]

"Air goes faster under the wing..." - stop watching at this moment as it's a wrong theory.

[flynfrog]

[youtube]http://www.youtube.com/watch?v=UqBmdZ-BNig[/youtube]

I think you mean over the top


Edit stole the video from this thread from a post by Tok
http://www.f1technical.net/forum/viewto ... =6&t=14877

[Rennsport_helgi]

Yes, in this case over the top. I've just read an article about a scale model airplane. A top curve of the wing is about 1,03 or so longer than bottom curve. So, speed difference would be 1,03 or so and the wing would never generate reasonable amount of lift. Unfortunately, I can't remember the exact numbers.

[pocketmoon]

NASA says http://www.grc.nasa.gov/WWW/k-12/airplane/wrong1.html

[Lycoming]

If you're going to show a video citing equal transit time theory, you should at least post a disclaimer explaining that it's wrong. Better yet, don't go spreading around videos with factual innacuracies. Also, that's not vortex shedding, that's just a few examples of how vortices form. THIS is vortex shedding:

http://en.wikipedia.org/wiki/Vortex_shedding

Which is something completely different, and has a very specific meaning to, for example, people who design chimney stacks or really tall buildings.

Also, nature does not abhor vacuums; it abhors differences in pressure. Subtle but important distinction.

It's a pretty terrible video, to be honest.

A top curve of the wing is about 1,03 or so longer than bottom curve. So, speed difference would be 1,03 or so and the wing would never generate reasonable amount of lift.

Are you citing equal transit time theory immediately after a post containing a video explaining how equal transit time theory is false?

[Huntresa]

"Air goes faster under the wing..." - stop watching at this moment as it's a wrong theory.

He says air goes faster over the wing when he first starts talking so ?

[flynfrog]

snip?

Wouldn't it still be vortex shedding with the resonate frequency being zero?

The second video shows that equal transit theory is false not the opposite.

[Rennsport_helgi]

I meant if he's not accuracy with that equal theory then there's no assurance that vortex shedding explanation is close to the truth.

[Just_a_fan]

The chap isn't wrong - he's just partially correct. Lift is the result of the laws of conservation of mass, energy and momentum being applied to the system. Bernoulli deals with conservation of energy in his equations, Newton deals with the conservation of momentum in his equations. Neither gives the complete story.

Navier-Stokes, on the other hand, does but you're not going to be doing a 2 minute YouTube sound bite explanation of NS.

[Cold Fussion]

Navier-Stokes, on the other hand, does but you're not going to be doing a 2 minute YouTube sound bite explanation of NS.

You could if all you wanted to do was to write down the equation (should take about 2 minutes).

[godlameroso]

Vortex shedding can be done by flapping wings, also vortex shedding does not necessarily mean less lift.

[olefud]

Vortex shedding can be done by flapping wings, also vortex shedding does not necessarily mean less lift.

Bees and, to some extent, birds use vortices to enhance lift. But in general, not less lift, just more drag.

[gambler]

Is there any chance that at the end of a fast strait, as the race car rapidly slows for a corner, that there is a backwash of turbulence that catches up and moves the car around a little, or promotes the wing to unload faster than it should?

[flyboy2160]

Is there any chance that at the end of a fast strait, as the race car rapidly slows for a corner, that there is a backwash of turbulence that catches up and moves the car around a little, or promotes the wing to unload faster than it should?

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