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Building Simple Wind Tunnels
There are several levels of wind tunnels that you can make depending on the degree of sophistication you need. In all but the simplest case, you will want to have an wind-speed meter, which also come with various levels of sophistication - and expense! One of the least expensive is distributed by various companies including Edmund Scientific (#H30603-49) or Pitsco (#X15557-101) for about $20 and measures up to 66 mph.
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A MODEST VERSION
The wind coming from an ordinary house fan is rather turbulant and swirling. One rather giant step up is to eliminate that turbulance by passing the wind through a box (shown to the right) that is filled with a square lattice such as found in an egg crate or for packing drinking glasses for mailing. The deeper this lattice the better as the squareness of the individual passageways eliminates swirling.
One more function has been added to this modest wind tunnel - it is a funnel and thus speeds up the wind at the outlet. This is due to the Venturi effect, which you should look up elsewhere. Here are two other views of the "wind funnel":
A BETTER VERSION
The main differences between this version and that modest one, above, are that the columnator is longer, the experimental objects are located in an extension of the columnator, and there is a second columnator after the experimental objects. Of course, the extension that contains the objects must be transparent so that you can see what you are doing.
If you are at the level requiring this version, you will also be needing various measuring devices within the chamber surrounding the object being studied. You might want to rig up pressure gauges as well as some sort of balance. A suggestion would be to study the wind tunnel made by the Wright brothers and adopt some of their techniques.
THE BEST VERSION
The United States National Aeronautics and Space Administration has an office of education that interfaces with its highly sophisticated operations with that of the schools and students of the United States. NASA has some of the most elegant wind tunnels in the world, and they also have several mobile units, which sometimes go on the road for demonstrations. Contact NASA if you need a really high tech wind tunnel.
A REALLY QUICK VERSION
This is really quick IF you have all the equipment needed. In essence, it amounts to using a pick-up truck fitted with an outrigger plank upon the end of which you can set your study object. On a calm day, the truck's speedometer will give you the wind speed, and if the outrigger extends several feet out away from the air currents flowing around the truck, it will experience essentially laminar flow air. A video camera would be a welcome addition as it can "watch" the object, and will record speeds that are microphoned to it.
WARNING! WARNING! WARNING! WARNING! This device is fraught with danger unless several precautions are taken. The outrigger can hit other cars, telephone poles or people and, like a dull knife, slice into them. Think thoroughly through all the scenarios were your outrigger to hit something: what would break, which way will pieces swivel, what would be damaged? You need lots of room for doing this method - a LARGE, empty parking lot, for example. Also remember that the plank must be firmly secured to the back of the truck so that it won't "fly" away. Also, you don't want anyone in the bed of the truck monitoring the wind action because if the outrigger does hit something that plank will break loose, swing around and snip the observer in half. And that might also happen to the driver if the plank hits something so immobile that the other end swivels right through and into the cab. Finally, you don't want to use a chase car just in case the plank "flies" off and back through your chase car's front window.
With all that taken care of, this version of a wind tunnel has advantages. The wind speed can easily be measured from the speedometer, the wind flow is fairly laminar and constant, and the wind speed can be higher than from most fans/wind funnel setups.
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