If you watch the movies, there isn’t much to a wind tunnel. Just a fan and a tunnel, right? The truth is there’s a lot more to it than that, and [ejs13] shows you how you can make a small tunnel with some basic supplies. One of the requirements for a useful tunnel is to have laminar flow — that is, flow in uniform layers with little, if any, mixing. This tunnel achieves laminar flow using an array of soda straws to direct the flow. In fact, there are 150 straws in total. You can see a short clip of the wind tunnel in action below.
The rest of the parts are easy, too. A computer fan provides wind, and there’s a little bit of wood and acrylic. You’ll notice in the video that you can easily see the airflow. That’s thanks to a light source, some water, and a bit of dry ice.
We imagine you can scale this design up with bigger fans and, of course, more straws. The acrylic is to provide a window so you can see inside. Glass would probably work, too. Overall, this would make a great class project, along with creating some wings or small models of planes or cars.
We’ve seen similar laminar flow setups but not using soda straws. Just what you need to test out that paper airplane design you’ve had in your head.
I think that wing is stalling.
Brings back memory of my research into boundary layer theory to improve flight characteristics of paint balls Boundary Layer Theory Utilization in Tactical Trajectory Improvement of Paintballs https://a.co/d/d25l0Og
Nasa has a pdf that has been around since the 90s that uses straws. Complete instructions and parts list.
https://www.grc.nasa.gov/www/k-12/smokie/SmokeyWindTunnelFinal3.pdf
I would think multiple fans (2×2 or 3×3) would work better than one because there’s a dead spot in the center of the fan.
Still needs plenum space to equalize pressure for the uniform flow.
I’m saving up a bunch of ICE brand drink bottles for a box fan no grille way of getting a straight penetrating flow to go a distance. They are straight sided with no frills or indents. If the top and bottom are cut off with a scissors for a neat edge, they’re about 17 x 6 cm. Maybe long enough to turn a “tornado” into straight line winds?
I know a bar owner that wants the big outflow on the wall up high of the HVAC to shoot over the closer areas and get to the far end. Grilles are designed to spread out the flow not shoot it far.
I remember a model rocket magazine from the early 1970s that published instructions on making a wind tunnel from a small box fan taped to a cardboard box that was filled with a bundle of body tubes to achieve the laminar flow. I only remember the price of that many BT-50 body tubes would have cost all my allowance money for over a summer to save for.
Not from the 70s, but it’s in a model rocketry newsletter. Much larger than the one described in the article:
Build Your Own Inexpensive Wind Tunnel
https://www.apogeerockets.com/education/downloads/Newsletter252.pdf
I definitely build something like this in the 80s for a science fair project.
My unique twist was to rotate it vertical and use it for spin testing. With a variable speed fan you can get a plane model to balance in the column in a stable spin.
The spin failure mode of the F-14 was in everyone’s consciousness because of the (original) Top Gun movie.
Thank, Al!
Kids, want to make one?
Use a piece of drainpipe. 1 drainpipe. Slide over a soda or bubble bath bottle as a window. 2 wall fasteners to use as feet. You can use drain pipe end caps and cut out. Or 3d print end caps to hold your fans in place.
Bob’s your uncle!
Hats off to DerAxeman for the link.
Here in EU plastic drinking straws are now banned. Because banning is fun and not in short supply.
Cellulose-based drinking straws would work just as well (and are similarly problematic as the plastic ones).
FWIW, a couple early issues of Make magazine (when that was still a thing) showed a similar device attached to the end of a garden hose. Significantly increased the distance of the stream.
I’ve seen straws used to (supposedly) tame port turbulence in a vented speaker.