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Wind tunnel testing for students

Postby curt » Sat Feb 24, 2018 9:03 pm

This week I had some fun supporting a class and several student groups running wind tunnel tests on a small RC model airplane. They were measuring lift, drag, and moments at various angles of attack, transforming the raw data into aircraft body coordinates, and the plotting the results. Pretty cool stuff. The coefficient of lift for this airplane peaks out at about 1.2. The wing continues to generate lift way past the stall point, but the drag builds up very rapidly as well. Photo credit: Curt Olson, used with permission. :-)

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Re: Wind tunnel testing for students

Postby Thorsten » Sun Feb 25, 2018 7:09 am

Hey, this is cool!
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Re: Wind tunnel testing for students

Postby D-ECHO » Sun Feb 25, 2018 7:18 am

wish there was some possibility to do this here ;)
Really cool :D
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Re: Wind tunnel testing for students

Postby Johan G » Sun Feb 25, 2018 3:46 pm

Building a wind tunnel is relatively easy. The main issue would be cost, getting meaningful measurements and calibration.

Wide section with a fan, tight section (with higher airspeed, but lower air pressure), and again a wider section. Could possibly be done with a fan, some cardboard, a [food preparation room] scale and some rods connecting the model to the scale.

Do a Google image search for "diy wind tunnel" or "scale model wind tunnel".
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Re: Wind tunnel testing for students

Postby curt » Sun Feb 25, 2018 3:57 pm

Our wind tunnel is driven by a WWII P-38 prop and a big electric motor. I think it can generate wind speeds up to around 100 mph. It recirculates the air and takes up 2/3rds of a pretty large room, but is surprisingly quiet. It is in the attic of what used to be the hangar. Back in the early days of my dept. (1930's) they actually designed, built, and worked on real aircraft. There are some cool pictures floating around that show the hangar with the Akerman tailless plane. Someday I want to build a scale model of that and fly it (perhaps autonomously.) It would be a fun and challenging project and would be a tip of the hat to our building's name sake, and his airplane that never really had a chance to fully fly. We have the original blue prints but I'm still trying to get a copy of them. Among other things, this is one of the reasons I started creating MAdesigner (madesigner.flightgear.org) ... as a tool to help design and build complicated wing structures based on logical (or higher level) design parameters.

https://www.aem.umn.edu/info/history/akerman.shtml

If anyone decides to build their own wind tunnel, *PLEASE* post pictures and tell us about your project. I think it would be very interesting.
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Re: Wind tunnel testing for students

Postby danielHL » Sun Feb 25, 2018 4:32 pm

That looks really cool. I remember the experiments we ran in the lab when I was an engineering student. Our wind tunnel had an open measurement box of about 1m^3. Sadly we never measured airfoils or anything like it.

If I remember correctly the most expensive component is the six component force and moment balance you need. We got ours for free and someone built the rest of the tunnel. Fan, motor, gearbox, ducts - all pretty low tech. But big and veeeeery noisy :P
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