Homemade Wind Tunnel

This is my homemade model wind tunnel that I made for my physics class. The model shows the effects of lift force on different airfoils. See the links below for purchasing materials:

[ericinventor]

Hello everyone, I made this video after learning about lift in my high school physics class. Now I study engineering at Cornell University and I am taking an Aeronautics class because I wanted to know if what I was taught in high school was correct since I have many comments on this video saying that my explanation of lift using Bernoulli's principle is incorrect. Now I will try to respond to these comments based on what I have learned:

[bocelle]

Your ability to build this with things like pen housing for sleeves and the simplicity of design is brilliant!

[chrisod]

You should get a newton scale with a spring and attach it to measure the force produced.

[anilallipilli]

Small correction: wing placed upside down is still a wing. Spoiler serves a different purpose it "spoils" the air flow which will cause lift it didn't, its the wing's job to create downforce. Anyway job well done.

[egamez]

Great project. Congratulations...but...the Bernoulli effect has very little effect on the production of lift on a wing. The Coanda effect of fluids acting on a curved surface creates a down-wash of the fluid, thus creating lift. So Newton's 3rd law of motion is the one "doing all the lifting", not Bernoulli's law.
Great experiment!!!

[cocemojoe]

That's a fantastic beginning,   If you placed the vertical posts on the outside of the foil you could change the angle of attack into the wing giving you more than just flat flight but take off and landing. also you already have most of the RC equipment add a couple of rc flaps smoke generator and nozzles, maybe some threads on the surface, and possibly a tail.   

[klaasvanmanen]

Very nice for a first attempt Experiments in a wind tunnel give much more accurate and repeatable data when done in laminar flow. By putting your ventilator in front of the model, you shoot a lot of very turbulent air onto the airfoil. The only thing you can really see here is that it actually moves. By moving the ventilator to the other side of the 'tunnel', and having it suck air *out* of the box, the flow around the airfoil will be less turbulent. Adding a honeycomb structure at the side where the air is sucked into the box, can reduce the turbulence even more, and create something which may start to look like laminar flow. The honeycomb structure should consist of small parallel pipes, similar to straws for drinking, placed in the direction of the flow of course, and cover the whole of the entrance. The walls of the straws should be thin compared to the diameter, to avoid introducing lots of drag. Pulling the rotor even further away from the airfoil (making the box much longer) will also help to improve laminar flow.

I guess you will have learned this by now since the video is already 10 years old. But then my comment may help your viewers who would like to copy your setup. Just copying would be a bad idea if they want to create something that actually deserves to be called a wind tunnel.

[rodomoyo]

This is so fucking cool dude, I’m making an engineering club for my highschool and I think this could be a rly fun project

[AerialPhotogGuy]

Very good project and very well done!!!
Nice presentation too!!!


It looks like the angle of attack is higher on the airfoil shaped wing than it is on the flat wing but that may not be the case, it could be that it just appears that way from where I sit.
If the angle of attack is less on the flat wing than on the airfoil shaped wing, then the comparison between the two wouldn't be fair, an "Apples to Apples" comparison for angle of attack would be
required but again, they may just appear to be different from my perspective.
Either way, your experiment clearly shows that an airfoil shape performs much better than a flat wing regardless of angle of attack.


Lots of RC guys fly flat foam wing planes including me and they fly pretty good as long as they have enough power (like a 1.25 to 1 thrust to weight ratio or better).
Give it enough power and almost anything will fly 😁.

It is true that an airplane with the typical airfoil design does not need as much power to fly (when compared to a flat wing airplane).
Although a flat wing airplane will fly, it will fly better and more stable with more lift if the wing has the typical airfoil shape because the air flowing across the wings adheres to the
surface of the wing much better than it does over a flat wing with a square or blunt leading edge, the reduced pressure on top of the airfoil shaped wing certainly has an advantage over a flat wing
with regards to lift.


I fly full scale airplanes as well (got my PPL many years ago) and I certainly would not even attempt to fly a full scale airplane with flat wings 😮


I tried flying a model 3D foamy with square leading edges, then I flew another one where I rounded the leading edge to help keep the air attached to the wing and while there wasn't much difference
in the overall performance, it did show improvement with stability, I assume it's because of reduced drag at the leading edge, anyway, it just seemed to be more controllable.
BTW, I'm a halfa** 3D flyer!! I can do knife edges, inverted circuits and a few other things all day long but nowhere near good enough for anyone to go out of their way to watch 😴


One of the main reasons for using the typical airfoil shape (other than added lift as you have demonstrated), is the fact that air will adhere to the surface much better and it will have a much lower
stall speed than a flat wing, a flat wing will have a much higher stall speed unless you use more wing surface area, this means that designers are trying to keep the wing loading as low as possible.
The best wing loading range with flat wings is similar to a glider and is usually in the range of 10 to 14 ounces per square foot of wing area.
I'm not familiar with what wing loading ranges are with full scale airplanes in terms of weight per square feet of wing area, I simply use the airplanes recommended weight and balance envelope from
the operators handbook to make sure it's safe to fly.
Even the rounded leading edge of an airfoil plays a very important role in keeping the air attached to the wing.
The amount of lift produced by a typical airfoil is fairly low but certainly noticeable, going with that principle alone will require a higher airspeed or airflow to produce a good amount of lift.
The total lift component of any airplane requires aerodynamic lift (with a typical airfoil) and angle of attack, it's not one or the other, it takes both but that is for maximum performance and efficiency.
The total lift component for a flat wing is really just angle of attack and typically will require more power for thrust when compared to a good airfoil design (as you have demonstrated in this test),
efficiency and stability is very low with a flat wing.


Try another experiment with the same airfoil shape like the first wing you tested but this time try it with the bottom of the wing parallel to the table, I think it will take a lot more airflow
to produce much lift but it would be very interesting to see what the results are.
Are you up for the challenge?
Maybe do another video comparing no angle of attack to the other various angles of attack?
Maybe you could figure out a way to make the wing so it will pivot on the vertical slide tubes that run on the vertical rods in the tunnel? That way you could use just one airfoil wing.

All full scale airplanes have some amount of positive angle of incidence to keep the fuselage level in flight, this is because it has to take angle of attack into account and the angle of incidence is
the angle between the longitudinal axis of the fuselage and the chord line of the wing.


As for spoilers, I think a better way to demonstrate the effects of spoilers would be to use that same wing but with a small spoiler mounted to the top side like you would see on a real wing.
Inverting the wing as you did here just shows how it performs in inverted flight.
Could you try demonstrating how that would work?


Another thing to note in regards to your setup is that you have the bulk of the air coming from your PVC pipe flowing over the top of the wing, there is less air flowing under the wing than it is over
the top of wing, great for creating lower pressure on the top of the wing but it doesn't seem like an accurate approach because in flight, there is always an equal amount of relative wind on both top
and bottom.
Notice that you have better results when you position the wing to the center-line of the PVC pipe, that allows the same amount of airflow over the top and under the bottom of the wing at
the same time.


Please know that
I'm am only trying to give you "constructive" criticism, I'm not downing your experiment or your efforts at all!!


Again, great experiment and well done!!



Keep up the good work!!

[smashingpencils]

What a legend for thinking of this!! Amazing!!

[enriquelaya]

Very nice. It is a good idea to use the RC motor and speed controller on the tunnel. The video does not show if you used an air straightening section to eliminate - reduce rotational flow. Usually this is done through air guides aiming to keep the flow parallel to the longitudinal axis. Assuming you did not, the flow pattern rotates heavily around the longitudinal axis. This has serious limitations on the type of experiments conducted.

[ronjones]

Excellent project. keep on experimenting and sharing what you find. You are an inspiration to young upcoming scientists. great job, !!

[fontunetheteller]

Very good, but I think you should use slicker rods, there seems to be a lot of friction between your rods and pen caps when the wing moves.

[georges]

Just what I was looking for, very cool.

[onehumanbeing]

Hey, such an fabulous project, I am an 8th grade student and I’m trying to do something fairly similar but have a few questions. Where did you get such a powerful fan, my cheesy fan doesn’t seem to bring my styrofoam anywhere? And how did you manage to make the iron poles so perpendicular to the platform and parallel to each other, I tried my best to make them parallel but the styrofoam still gets stuck on the top. Thank you so much!

[haydenborgic]

How can you dislike this? It is informative if you don’t like it don’t click on it

[aryanKumar-zodq]

Excellent example for lift force in aeroplane, thanks

[vittorfl]

Wing chord down: airplane
Wing chord up: f1 car

[KaushikSethuraman]

Love the model. How did you make the wing? Or where did you make it from? You don't mention that in the materials section of your description too. Thanks.

[interprimus]

may be a bit late), but if you change air wind direction in your tunnel, you will get significantly less disturbed air stream. try to use a smoke to visualize and see the difference when tunnel “pump” air and “suck”