science of aerodynamics

[ho50ca]

Hiya,

I'm a teacher and I've got to deliver a lecture on aerodynamics to a group of gifted kids in Grade 6 and 7.

I am planning to introduce my lecture by discussing, briefly, the men I consider to be the twin fathers of the actual science of aerodymics, Prandtl and Lachester, then narrow the discussion to lift theory, talking/diagramming the various incomplete/bogus theories of lift, equal transit time, skipping-stone and Coanda. Then I'll introduce vortex flow theory and discuss/diagram that.

I'll end off with a hands-on. I have created several airfoils out of blue foam: Aquilla, flat-plate and undercamber. i'll add to that the Clark-Y off my model Spitfire and we'll see which creates the most perceived lift at what angle-of-attack, by holding them in the flow of air from a couple floor fans.

What do you all think of this? Keep in mind these are gifted kids so, high order thinking for their age is the norm, not the exception.

HO

[Ollie]

Please read this:
http://jef.raskincenter.org/published/airfoil.html
The kind of three airfoils giving lift depend on reynolds number. At Re 4,000 (insect size) the flat plate is best, next the curve plate and the Clark-Y is worst. At Re 30,000 the lift is a curved plate is best, next is the flat plate and the worst is the Clark-Y. At a reynolds number of 110,000 the best Clark-Y, next the curved plate and the worst is a flat plate.

Also see:
http://www.news.cornell.edu/releases/March00/APS_Wang.hrs.html

You can show the reynolds number effect. In still air, a burning punk gives off smoke in a laminar flow column for a few inches and then changes in turbulent flow.

[ciurpita]

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

[nmasters]

This might make a good handout (http://yarchive.net/air/lift.html)

[banktoturn]

Hiya,

I'm a teacher and I've got to deliver a lecture on aerodynamics to a group of gifted kids in Grade 6 and 7.

I am planning to introduce my lecture by discussing, briefly, the men I consider to be the twin fathers of the actual science of aerodymics, Prandtl and Lachester, then narrow the discussion to lift theory, talking/diagramming the various incomplete/bogus theories of lift, equal transit time, skipping-stone and Coanda. Then I'll introduce vortex flow theory and discuss/diagram that.

I'll end off with a hands-on. I have created several airfoils out of blue foam: Aquilla, flat-plate and undercamber. i'll add to that the Clark-Y off my model Spitfire and we'll see which creates the most perceived lift at what angle-of-attack, by holding them in the flow of air from a couple floor fans.

What do you all think of this? Keep in mind these are gifted kids so, high order thinking for their age is the norm, not the exception.

HO

HO,

IMHO, what you are proposing is too much stuff. I would lean toward including a few main concepts, and going in to some depth. I would also avoid trying to 'inoculate' the kids against some of the incorrect stuff that is commonly heard. Giving them good, correct explanations is probably enough without the added baggage of debunking the mythology.

If you could get through a nice exlplanation of how a typical airfoil creates pressure difference between the top and bottom surfaces, and what happens when a wing stalls, followed by the hands on stuff, that would be a pretty good day. If the kids are capable of higher order thinking, don't burden them with so much detail that they are reduced to rote memorization. Give them some concepts to integrate. I think that references to some of the historical figures are good, but I would emphasize their main contributions, rather than their 'greatness'. As an example of diligent applied R&D, the Wright brothers are hard to beat.

Good luck,

banktoturn

[danfly]

ollie,

Jef Raskin is a genious of our time.

[Ballistic]

I concur with banktoturn. Don't bother with historical minutae until the physics are well understood.

A technically-minded youngster wants but one thing: tools. Give them the equations and explanations so that they can solve the sort of real-world problems their minds will come up with. Leave historical minutae for the end, as an afterthought. Once they have solved problems, they will want to ground them somewhere - but not likely before. A mind intent on solving problems is more concerned with having the proper tools than knowing from whence they came.

One good resource is:
http://www.grc.nasa.gov/WWW/K-12/

It's always accurate, and smashes some common myths.

If you have a few kids that really 'bite', I'd push them towards a most prelimiary understanding of computational fluid dynamics (CFD). Some bright kids I've explained the priciples of CFD to were absolutely amazed by the concept, and I think at least one of them will carry the interest through to his studies, now and in the future. We need to get them interested and involved... can you imagine the technical deficit we face otherwise??

[chinlin0924]

hi ho50ca ,
I have a question about aerodynamics on small model helicopters or airplane.
They might got some scale ratio problem on its viscosity compairing with the full-size one.
how do you think about the differences for full-scale aircraft and model-aircraft in aerodynamics?

Thanks,
Chinlin

[Sparky Paul]

Inefficient airfoils are the biggest difference.
Full scale planes have Reynolds Numbers high enough that the air flow can be well controlled.
Air flow is more difficult to control at model Reynolds Numbers..
Look at this polar for the Eppler 374.
The flow at low RN is really, really bad..
It begins to smooth out at higher RNs... more chord, more airspeed...
A plot of that airfoil for common full scale RNs wouldn't look nearly as erratic.