i need help on a aeronautic experiment 1

[icebraker]

I am a 10th grade student and I enjoy physics and aeronautics and I need help. I am conducting an experiment on three different types of wings. They are Delta, Swept, and Straight.
I need to show the difference in the designs and how can I do this with a model wind tunnel. I have tried before, but when I put the aircraft model in a turn position and the angel of attack, the air flow is still straight and I feel it is not giving me a true reading on how the wing design would affect manuverablity and speed. Is there a solution to my problem.

Also do you know of any mathmatic formulas that could help me in this experiment and what each means.

I thank you,
Stephen Lehrter [sig][/sig]

 

[terrydrinkard]

Hello Stephen,
The basic difference between those three planform types is the slope of the lift curve. Granted, they also have different critical mach numbers, but I doubt your wind tunnel will produce transonic flows. If it can, let me know and we'll talk about it. Everything below is assuming (relatively) low speed incompressible flow.
The straight wing will have the steepest lift curve slope. That is, it will generate more lift per degree of angle of attack than either the swept or delta. This is the fundamental difference and you can show this by plotting lift vs. angle of attack.
Deltas and swept wings are not as efficient in turns because of this difference. To turn level, the wing has to generate more lift (try the vector math, it's relatively simple). Generating more lift creates more drag, and the straight wing is most efficient at this. Your data should show that the delta is least efficient in a turn because it generates the greatest increase in drag for a unit increase in lift.
So, in your windtunnel you need to be able to measure angle of attack, lift, and drag. If you can do this, you can show how those wing planforms differ in their aerodynamic performance. Use the same airfoil section for all three wings, otherwise the data lose some meaning. You do not need to put the wings in a banked position.
If you live near Seattle, Washington, I can help you more with the math. [sig]<p>Terry Drinkard<br><a href=mailto:terrydrinkard@yahoo.com>terrydrinkard@yahoo.com</a><br>[/sig]

 

[TCrush]

check this bookout if you can find it.
&quot;Introduction to Flight&quot; 4th ed. By John D. Anderson Jr.
should help explain everthing you need, and how to do it Mathmatically. If you can't find it let me know and I'll get you the equations.

 

[knobhead]

Or &quot;Mechanics of Flight&quot; by A C Kermode. Very good, very readable and has plain English explanations of all this stuff

 

[moygr1]

SCALE EFFECT:

The three wings are obviously different, and thus will give different properties, delta wings offer good lift and eccelerated speeds, say Mach and higher, and swept wings, give the same loading with reduced tip loading stresses as well as reduced drag, thus greater efficiency of the wing. and straight wings are intended for slow aircraft, say 250 knots or less. All are different as mentioned and thus will have different performance at different velocities, angle of attack and thus thickness of the wing, etc etc.

This is what the other individual with lift curve was pointing out, what that means is that the lift changes with each change in flight condition. A flight condition is a change in altitude, airspeed, temperature, angle of attack.

The reason temperature is listed is because when the temperature is hotter, the air is &quot;less dense&quot; and therefore your aircrafts performance is going to be reduced. In other words, your wing will have to move faster and faster to get the same lift as if it were at the same altitude and very cold.

Now scale effect is basically this:

The air around your model, which never changes in its size in relation to the model wing your using, actually undergoes the same effects as if it were over a real full size wing. The problem is the surface area, chord (wing width usually taken at the root section and measured in feet)and span are so much smaller that even though the air flow going over the wing is the same, the properties that would show a noticeable effect, which are the wing dimensions, just arent large enough to show the results.

Now your wind tunnel, id be asking what size it is? what size is your model, position and location etc, and most importantly, whats the reynolds numbers at???

Im not sure how well versed you are with aerodynamics, but do not confuse the properties of a delta wing as being compatable or comparable to a swept of standard rectangular wing, you will get different results.

moygr1@home.com