Building a Wind Tunnel and Stabilizing an Airplane in Pitch

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In summary, Cyrus built himself a wind tunnel using a house fan, Plexiglas, metal brackets, and flow straighteners. He used a PID loop to control the servo attached to the wing. He is testing the wind tunnel by flying a RC airplane through it.
  • #1
Cyrus
3,238
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It Works! Muahahahaha~

I have to do a project for my controls lab course. I decided to do the stabilization of an airplane in pitch. I wanted to make something that would actually attach to one of my RC airplanes, but the problem is that I’m not an EE and I don’t know/have the time to build and test an entire circuit board.

So I went another route. I decided to build myself a wind tunnel using a house fan, $90 worth of Plexiglas I cut with a ban saw, particle board for a base, and metal L brackets for the side supports. It’s all screwed together with 1/4-20 bolts\nuts\washers.

I got the airfoil for free from a friend who did his masters in Aerospace in manufacturing of small airfoils from composite materials. It’s a small blue Styrofoam wing with a nice hole cut through the CG so I could put a rod through it for support. Its also covered in fiberglass and epoxy resin. I could have made one myself, but this was a HUGE time saver having one done for me.

I made flow straighteners inside the wind tunnel using more Plexiglas pieces and taping them with 2" clear tape. Power comes from a normal house fan.

For now, I was controlling it with my RC Futaba Controller. For the project I have a servo interface that will run on MATLAB through a PID loop. *Hopefully* you will be able to tell it an angle, and it will move the servo and maintain that angle.

Right now the dowel is just held in place by sliding through the side holes in the Plexiglas, but I’m going to replace it with roller bearings once they come in next week. It has too much friction the way it is right now.

A potentiometer is going to be attached to the shaft to sense the angular rotations. The voltage will be converted to a wing angle.

I bought everything to make the wind tunnel at home depot and came up with how I was going to make it on the fly as I bought parts.

I built this in one day, and it works!

This is way cool. I’m a geek.
http://youtube.com/watch?v=tPqrOspSz6g

http://img145.imageshack.us/img145/7804/pict0070kx4.jpg

http://img144.imageshack.us/img144/9958/pict0071gm3.jpg

^ Note wind tunnel propped up on airfoil theory book. It was useful for something. :blushing:
 
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  • #2
Nice work, cyrus.

Hah!, i just saw the video, very pretty :tongue2:
 
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  • #3
Excellent work.

I am going to be designing and building a rocket with a stability control system for my senior project. The rocket will also be equipped with an altimeter and gps.
 
  • #4
Nice work! Very interesting to a fledging aerospace engineering student.
 
  • #5
Very nicely done, it looks really good.
 
  • #6
leright said:
Excellent work.

I am going to be designing and building a rocket with a stability control system for my senior project. The rocket will also be equipped with an altimeter and gps.

Let me know how it goes. PS, program it in MATLAB, because that's all I use, and that way I can read your code. :tongue2:
 
  • #7
http://youtube.com/watch?v=UNB5pHivYTU

Here, I added some streamers so you can see the streamlines, or is it streaklines, or pathlines...I DONT KNOW... the yarn I used has too much weight. I am going to find something lighter to use tomorrow.

You can't see them move too well though, I need a stronger fan source. I found an electric leaf blower in my garage. I will give that a whirl tomorrow. :devil:
 
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  • #8
That is just beautiful work Cyrus!
 
  • #10
Great job Cyrus! Very nice indeed! :approve:
 
  • #11
cyrusabdollahi said:
PS, program it in MATLAB

Is there any other way to go?
 
  • #12
Exactly.

Check this out. I got an outdoor electric leaf blower. I had to put on ear plugs. That thing is powerful! You can see the yarn is now striaght, it won't sag due to the slow flow.

One video is at medium speed and the other is at full power on the blower.

I had to prop up the blower a full 2 feet away from the wind tunnel just to lessen some of the load.
House Fan (Slow)
http://youtube.com/watch?v=UNB5pHivYTU

Black & Decker Leaf Blower (fast)
http://youtube.com/watch?v=Jla5o9FgSkQ

Now you can really see the lines move as the wing moves.
 
  • #13
Black & Decker Leaf Blower (fast) - That's great! :rofl: Got some buffeting there.
 
  • #14
Nice work, Cyrus! You can get a straighter airflow from your leaf blower by inserting honeycombs between your 3 plastic flow vanes. Take a sheet of thin cardboard, manila file-folder stock is about right, and fold it with accordian pleats. Unfold it, put a flat sheet on top, then put another folded one above and so on until the space is full. Seen along the direction of airflow it looks like (except imagine the stacks are touching...).

---------------------
/\/\/\/\/\/\/\/\/\/\/\/\
---------------------
/\/\/\/\/\/\/\/\/\/\/\/\
---------------------
/\/\/\/\/\/\/\/\/\/\/\/\

This should eliminate a lot of the turbulence and buffeting seen in your last "fast" video.
 
  • #15
I froze some shots at level, +20 and -20 and highlighted the streamlines using paint. You can see the difference in the flow as the wing is pitched both up and down. In one case the string curves back up above its starting point. Neato.

http://img385.imageshack.us/img385/9371/wingyh8.png

1.21 JIGGAWATTTS??
 
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  • #16
I'm proud of you, Cyrus!
 
  • #17
Linkin Park eh?

That's really cool!

Lisa! said:
I'm proud of you, Cyrus!
Hey, when did you come back?!
 
  • #18
cyrusabdollahi said:
I built this in one day, and it works!

This is way cool. I’m a geek.

i wish i was a geek!

nice work (even though i don't understand any of it :rolleyes: :biggrin: )
 
  • #19
Mk said:
Hey, when did you come back?!

About 3 week ago I guess!:smile:
 
  • #20
hey your fan looks identical to mine
 

1. How is a wind tunnel built?

A wind tunnel is typically constructed using a long, enclosed tube with a fan or compressor at one end to generate air flow. The tunnel is lined with smooth walls and contains a test section where models or aircraft can be placed to simulate real-life conditions. The tunnel also has a way to accurately measure air speed and pressure.

2. What is the purpose of stabilizing an airplane in pitch?

Stabilizing an airplane in pitch means ensuring that the aircraft maintains a steady and level flight path. This is important for safe and efficient flight as it allows the pilot to have better control over the aircraft and prevents any sudden changes in altitude or attitude that could be dangerous.

3. How is an airplane stabilized in pitch?

An airplane is stabilized in pitch through the use of various control surfaces such as the elevator, trim tabs, and flaps. These surfaces work together to adjust the lift and drag forces acting on the aircraft, allowing it to maintain a stable pitch attitude. Additionally, the pilot can also adjust the angle of attack or use autopilot systems to help stabilize the aircraft.

4. What are some challenges in building a wind tunnel?

One of the main challenges in building a wind tunnel is creating a smooth and consistent flow of air. This requires precise engineering and design to minimize turbulence and ensure accurate testing results. Additionally, constructing a wind tunnel can be costly and time-consuming, as it requires specialized equipment and materials.

5. How is data collected and analyzed in a wind tunnel?

Data collection and analysis in a wind tunnel involve using various instruments and sensors to measure the forces acting on the model or aircraft being tested. This data is then recorded and analyzed using computer software to determine the aerodynamic properties of the object. Engineers and scientists can then use this information to make improvements or adjustments to the design of the aircraft.

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