Advice For Building a WINDTUNNEL

[jgb768]

Advice For Building a WINDTUNNEL!

OK everyone i need tips/ advice on building a windtunnel. I need Info that can help me avoid problems that i will run into while making the windtunnel that would arise from lack of experience. etc.

Let me provide some info about me, for refrence. I am a high school student (senior), i am building a windtunnel, I have not taken calculus. NOT stupid! :rofl: i have a very basic understanding of aerospace engineering. I understand the basic parts of a windtunnel and the necessity of laminar flow, etc., but I am what you would call a noob, not exactly experienced like u guys so that's why I am here asking 4 ur knowledge

-thx-

 

[berkeman]

It would help guide our responses if we knew more about what you have learned so far in your own research on wind tunnels. I think that this request is related to your science fair project thread, which is fine, but here at the PF (much like in real life in engineering and physics), we ask to see your work so far in order to help you better. Just asking an open question like this puts an enormous burden on the time of all of our PF helpers. Do we have to explain what a diffuser is? Or do you know that already? Do we have to explain scale factors, or do you know that already? What regimes are you asking about? Do you see how asking a very general, open-ended question puts a big time burden on the people who you are asking for help?

So, I'd suggest this. Do a PF search on windtunnel (for the word appearing anywhere in the posts), and read through the threads. Then maybe try a search for tunnel in the title, to see if that gives any additional helpful hits. Then a google search on "wind tunnel", which will provide LOTS of additional info.

And then if you have questions (which you probably will, about practical diffuser considerations, and scale factors, and sensors, and ...), this is absolutely the right place to ask them.

Please do more work on your own (this IS your science fair project after all), and then come back with informed, intelligent questions for us. You will get lots of help if you do your part first.

 

[momentum_waves]

<https://www.amazon.com/Instrumentation-Measurements-Experiments-Fluids-Rathakrishnan/dp/0849307597/ref=pd_bbs_sr_1/104-2322076-5544765?ie=UTF8&s=books&qid=1192687548&sr=8-1>

If you have the financial resources, I would suggest purchasing this inexpensive reference book. It is an extremely useful resource, written by on of India's leading academics.

 

[jgb768]

Settling Chamber - The purpose of the settling chamber is to create a Laminar flow.

Contraction Cone - The contraction cone takes a large volume of low-velocity air and reduces it to a small volume of high-velocity air without creating turbulence.

Test Section - The test section is where the wing is to be tested

Diffuser - The diffuser slows the speed of airflow in the wind tunnel as it moves toward the fan.

Drive Section - The drive section is the fan

I DO NOT KNOW MUCH about the mathmatical aspects of a wind tunnel, and i wouldn't know where to begin asking questions.(like scale factors).

here is a specific question that i am having THE MOST trouble with. The fan, which is more important, the size or speed of the fan? Is their any thing specific i should know about the fan because in my research on google and nasa's websites. I find little information on it concerning small windtunnels

 

[vitorpy]

jgb768,

A little advice: specify first your requirements. What is the size of the wind tunnel you're going to build? Air flow velocity?

After you defined the first requirements, you can size the fan. Most of homebuilt models will use a brushless DC motor, as the ones found in CD-ROM drives (it's a really nice one). With the motor and size/velocity requirements, you can properly define the fan you're going to use.

And congratulations for your interest. Be welcome to the field. Good take offs for you guy =)

 

[jgb768]

i need a windtunnel to get data for the effects of windshear on a wing, i have the windshear part, I am going to use an air compressor so i can get an accurate velocity for the windshear : ) but as for the windtunnel i don't know exactly what size it should be, i found a thing that said u could build a windtunnel that had a wind speed of 30 mph for under $200 and the link was to a NASA site but that NASA site apparently dosent exist anymore, because the link is a dead end but that same link is everywhere. anyone know about it or if it was moved?

 

[vitorpy]

Although my field is CFD, I'll do my best to help you.

Doesn't look like a simple experiment, nice choice. Difficult one, though.

If you are going to measure the effects of wind gradient on an airfoil, first, define your airfoil. Build tunnel section to match the size of test airfoil. A cylindrical one is the best.

What variables you're going to measure? Chose appropriate measuring equipment.

So, now you already have the sizing requirements of your wind tunnel. Wind gradient effects must account for a change of 30 knots or up in horizontal velocity. So, define the Vo, the base velocity. After this is defined, you have air speed and sizing requirements - with this, you can find the appropriate fan and motor (there's an empirical formula to this, I'll post when I find it - if you have Anderson's Introduction to Aerodynamics or can find one, you're going to find the formula in it).

Now, you have to normalize the flow. A very fine web will do it for a small size, for a bigger size you can cut small tubes and construct a grid like structure with them.

Hope it helps.

 

[jgb768]

ya that's probably the best help I've gotten off the PF so far ty : ) i'll see if i can dig up that book

 

[jgb768]

http://ldaps.ivv.nasa.gov/Curriculum/tunnel.html

Thats the link that was supposed to be the page that told u how to build a 30mph windtunnel for under $200 but the link is a dead end. anyone know about it?

 

[vitorpy]

http://web.archive.org/web/20020202113520/http://ldaps.ivv.nasa.gov/Curriculum/tunnel.html

archive.org is your friend =)

 

[vitorpy]

http://en.wikipedia.org/wiki/Subsonic_and_transonic_wind_tunnel

Might help too.

 

[jgb768]

im starting to believe this is Definitely going to be possible : D

 

[jgb768]

http://web.archive.org/web/200202021...um/tunnel.html

that link u gave me ^ the plans.pdf file is just a link to that site that doesn't exist : (

 

[jgb768]

http://130.64.87.22/robolabatceeo/college/windtunnel/baals.asp

YAY! I found it : D lol

now all i need is suggestions for a wing to do my tests on.

 

[FredGarvin]

http://arxiv.org/ftp/physics/papers/0208/0208039.pdf

 

[vitorpy]

jgb768,
Glad you believe, motivation is the key to success, in any project.

For the wing, select it when you have a nice idea of the airflow from the wind tunnel. Many proprieties databases for different airfoils exists around the Internet, just Google for it. Also, make a choice based on your ability to construct it. A symmetrical airfoil might be easier, but I don't know for sure.

Keep the good work, boy!

 

[jgb768]

WHAT kind of wing should I use?

 

[jgb768]

k wait i can't buy a wing...darn it lol that's stupid hehe but hey... go with the flow = )

 

[vitorpy]

Just select a profile (a Selig 1223 will do) and build the wing, guy.