Where to post: Lift Aerodynamics Question

[Dick74]

Where is the best place to post a question/challenge concerning the frequently published theory about wing lift due to the increase in the air velocity over the upper airfoil surface.

 

Would it be on this Forum? If so, which category?

[chasingmars]

Where is the best place to post a question/challenge concerning the frequently published theory about wing lift due to the increase in the air velocity over the upper airfoil surface.

 

Would it be on this Forum? If so, which category?

Most people here are builders and pilots, not aerodynamicists, and I don't know if it's the right audience to discuss fluid dynamics and theory of lift, etc.

 

That said, before you launch in on Bernouli you may, if you already haven't, wish to look at Newtonian concepts of lift, and consider that it's not really an either/or thing, but rather, both are simplifications of relatively complex goings-on that involves viscous effects and such, and as models, aren't necessarily an exact representation of the details of the system.

[Edge 513]

I'm sure there are guys that could sit around your campfire and swat a few flies. If you're here to speak tho, and not to hear...about canards, you are inviting the wrong Indians. In fact you're in the wrong camp.

[sounds of muffled rummaging under the deer hides...]

Ugg. Wheres that dusty peace-pipe Tonto? Dicks gonna need it for the RV Tribe.....

[WileEZ]

The best place probably would be at http://www.homebuiltairplanes.com under the "Design / Structures / Cutting Edge Technology" forum.

 

The members there are really into the different aspects of airplanes including digging into why one design work and another doesn't work on a certain design and vis versa.

 

And yes they do discuss canards in general and refer you to this or the other canards forums for specific canard models questions.

 

Here's a canard (or two) I like to dream about building! (From: http://www.aircrew.org.uk/woking/W_News161001.html)

[Dick74]

Thanks for the comments.

 

I am interest in understanding lift so I can better develope my concept of a canard amphibian, similar to Peter Van Dyne's Merganser, that is cheap and can be kept in my one car garage. I currently am working on the details.

 

I get particularly upset when experts promote ideas that can not be proved and supported with the accepted laws of nature, hense my question. I will look at the Homebuilt forum for a place to start my discussion. If I am wrong then I would like to be shown the errors in my thinking.

 

Craig K.,

Can you give me a source for information on the Newtonian concepts of lift that you mentioned? I would like to check them out.

[Marc Zeitlin]

Can you give me a source for information on the Newtonian concepts of lift that you mentioned? I would like to check them out.

See:

 

http://www.av8n.com/how/htm/airfoils.html

 

for a pretty good explanation of how wings work. That whole site is very good, with few errors. None of that "equal transit time" crap.

[Jon Matcho]

Where is the best place to post a question/challenge concerning the frequently published theory about wing lift due to the increase in the air velocity over the upper airfoil surface.

I moved your post here, to the Aerodynamics sub-forum.

 

I get particularly upset when experts promote ideas that can not be proved and supported with the accepted laws of nature, hense my question.

Yes, that's an issue. In these cases Expert would be the wrong title. With much of anything "published" there are degrees of credibility that you need to be savvy to.

 

I will look at the Homebuilt forum for a place to start my discussion.

I doubt that's the right forum either. Like here, I'd bet there are just a small handful over there that go into work every day with a title remotely resembling 'aerodynamicist'. Actually, I changed my mind. I'll bet there's maybe 1 real aerodynamicist over there, if any.

 

For discussions relating to new designs such as yours, check out the Models/Sims & Concepts sub-forum here.

[Dick74]

I have checked out the site, http://www.av8n.com/how/htm/airfoils.html, suggested by Marc. On the site I have a problem with the basis for the placement of streamlines and the downstream end condition. I can not understand how either can be proved. It appears to be a flawed concept.

[Marc Zeitlin]

On the site I have a problem with the basis for the placement of streamlines and the downstream end condition. I can not understand how either can be proved.

Do you have a problem with it because you can't understand it, or is there some mathematical or test basis for your problem? Things are considered proven when the theory matches the data.

 

In fact, the streamlines and downstream conditions shown in the figures on that web page match exactly with what the mathematics of inviscid flow around and airfoil predict, match CFD analyses (which needs no theory, just an understanding of the underlying physics of fluids), and also match exactly what's found in smoke tests of airfoils in wind tunnels, as well as the pressure distributions.

 

Here's an on-line simulator:

 

http://www.grc.nasa.gov/WWW/K-12/airplane/foil2.html

 

Some actual flow visualization:

 

http://www.aoe.vt.edu/~devenpor/aoe3054/manual/expt1/text.html

 

And again:

 

http://amasci.com/wing/airgif2.html

 

It appears to be a flawed concept.

In what way does it appear flawed, given that it matches theory, numerical analysis, and the facts?

 

If you don't state what you think is incorrect and how, it's difficult to address the issue/question.

[Dick74]

Thanks Marc,

The references you have given should give me a basis for understanding or explaining my impression. I have a problem in that I can not accept anything that does not fit in with everything else that I know and have experienced.

 

I will review, study and analyze the info and report back.

[Phil Kriley]

See:

 

http://www.av8n.com/how/htm/airfoils.html

 

for a pretty good explanation of how wings work. That whole site is very good, with few errors. None of that "equal transit time" crap.

That is a good site! One thing that has always bothered me, though, is using a stationary wing and moving air.

 

Quote from the site: "We know that air has mass. Moving air has momentum. "

 

It always bothered me that this doesn't seem to be taken into account when using a wind tunnel (or a computer program) to try to simulate what happenes to a wing that is actually moving through still air.

 

Or maybe it has been taken into account and it was found that the difference is negligible. I wish I had the smarts to REALLY understand this stuff.

[TMann]

Quote from the site: "We know that air has mass. Moving air has momentum. "

 

It always bothered me that this doesn't seem to be taken into account when using a wind tunnel (or a computer program) to try to simulate what happenes to a wing that is actually moving through still air.

It's all relative. When you are skydiving, it always seems as though the air is rushing up at you. In Vegas, they have a vertical wind tunnel and it still feels like the air is rushing up at you.

[Marc Zeitlin]

..... I have a problem in that I can not accept anything that does not fit in with everything else that I know and have experienced.

You're hardly the only one in that category :-).

 

I will review, study and analyze the info and report back.

Sounds like a plan!

[Marc Zeitlin]

That is a good site! One thing that has always bothered me, though, is using a stationary wing and moving air....

Whether the air is moving and the wing is stationary or the air is stationary and the wing is moving is immaterial - the aerodynamics are exactly identical, since we're nowhere near relativistic speeds. Velocity doesn't matter - acceleration does - that's where forces come from. F=ma, right? At any rate, the air particles do exactly the same thing whether in a wind tunnel or over a moving aircraft wing - they don't know the difference.

[Cozy Girrrl]

....In Vegas, they have a vertical wind tunnel and it still feels like the air is rushing up at you.

Uhm... maybe because it is?

...Chrissi

[TMann]

Uhm... maybe because it is?

...Chrissi

....... now you're getting it!