Wind Speeds and AOA of an Aerofoil.

[Rusty Cessna]

Hiya folks,

I am due to start a physics A-level practical investigation with the above title and I was wondering if any of you where I could find out any information on the physics of wind speeds and Angle Of Attack of an aerofoil, I would like to link it into Critical angles and stalling etc but really don't know where to start. Any tips on the theory and how to go about the practical would go down well too.

Thanks in advance.
Rusty.

[18-Wheeler]

Try here for starters - http://www.best.com/~williams/avform.html

[bookworm]

Try
John Denker's See How It Flies (http://www.monmouth.com/~jsd/how/)

[LAN]

Hi Rusty!

Well, for a practical demonstartion, I would recomend NASA's "FoilSim". This program is available through their homepage under "Education" and allows you to design a given airfoil and conduct measurements of physical properties of the air flowing around the airfoil.

If you are looking at making a presentation, I would recommend starting with the properties thickness and camber and then relating them to viscosity & Reynolds-no.

Good luck with your project!

Best rgds,
Ivan

[Rusty Cessna]

Thanks for the replies, very helpful!

I have a vague idea of how im going to do this, the one thing that is stumping me at the moment is how to measure Lift in a basic measure withought knowing the Coefficient of lift.

Thanks folks,
Rusty.

[Zeke]

Rusty,

It took a while for some very smart people to work out what you are asking.

I would start with a rotating cylinder then apply a Joukowski transformation to get an aerofoil.

You can transform a cylinder to an aerofoil, and you also transform the flow about a cylinder to flow about a aerofoil.


http://www.diam.unige.it/~irro/animation/cilsmo000.gif
http://www.diam.unige.it/~irro/animation/prosmo000.gif

http://www.diam.unige.it/~irro/animation/cilsmo005.gif
http://www.diam.unige.it/~irro/animation/prosmo015.gif

http://www.diam.unige.it/~irro/animation/cilsmo010.gif
http://www.diam.unige.it/~irro/animation/prosmo030.gif

You can play with the nasa foil sim to calculate the ideal lift generated for an aerofoil.

Z

Some links to look at http://www.diam.unige.it/~irro/cilindro1a_e.html http://www.diam.unige.it/~irro/java/conformi1_0.html http://www.jesus.ox.ac.uk/~dacheson/a6.html http://www.lerc.nasa.gov/www/K-12/aerosim/ http://www.aero.usyd.edu.au/aero/jouk/jouk.html

[bookworm]

Rusty

If you really mean how to measure lift, try a pair of scales or a spring balance! Lift is a force.

If you mean how to predict roughly how much lift you can expect to get...

You need to know what limits you can adjust the lift coefficient between. Then multiply by the wing area and dynamic pressure. The maximum coefficient of lift will depend on the scale of your model (Reynolds number) but somewhere between 1 and 3 would be a good starting point.

So say you've got a 1 square metre wing and a 3 m/s wind tunnel. The dynamic pressure is about 5 Pa, and so with a lift coefficient of 1 you'll expect a lift of 5 N (or about 500 g on the scales).

Try plotting that lift against AOA. Don't forget to post your results here...