Yea this is definitely one of the reasons I'm building in modular sections. Hopefully the flow straightening grid I'm going to build will do the job well enough, but if not I can always re-design that section, and/or the contraction cone in order to get it better.
The plan so far is just to use simple smoke stream visualizations. I can get smoke pellets and run the exhaust through a tube into the tunnel, or I can just use some dry ice and water in a coke bottle and then use a tube to direct it.
Very good point about the wall effects. Right now the...
I got some quotes on large diameter PVC and sure enough, it's just too damn expensive. I've considered the scavenging route, but I've decided I'm just going to go with my original basic design using a lexan box for the test section and 1/2" cabinet grade plywood for most of the rest of the...
Certainly a good point. It's a bit of a catch 22 though because the Cadets meet weekly at a school, not at their own permanent location, meaning the tunnel will need to be brought to cadets and assembled when needed, thus it absolutely has to be portable and modular. Otherwise, I can build it as...
I'm looking into some large diameter PVC pipe. I'll make some calls tomorrow. If I can get 10" or 12" diameter pipe, then the booster fans make a very nice fit and a very good CFM compared to the fan system I was planning to use. Unfortunately, the downside is that large diameter pipe only seems...
My original choice was actually to use PVC pipe with a couple of windows cut out and some lexan over top, but the largest diameter I could find readily available was 4", which is smaller than I'm willing to use because in a classroom full of kids, it just wouldn't provide enough visibility...
Good to know on the symmetry. PVC is an interesting idea. I've noticed that locally PVC sheets are a bit harder to comeby, and at larger thicknesses, are more expensive than sanded cabinet grade plywood. It'd certainly be a nice weight reduction though.
My plan right now is to make the test...
The duct fan booster is a great idea! Saw a few 10" at 650cfm for around $60. As far as speed, I'm thinking if I hoop it up to a variable AC adapter that should do the trick for speed control.
Another question I'm having trouble with:
Is symmetry important in the tunnel design? Or is it less of a factor since the flow is straightened anyways?
For instance, does the symmetrical design on the right have some sort of functional benefit over the asymmetrical design on the left...
Sure enough! When I was using the sq. inches to sq. feet converter on Google (because dividing by 144 is extremely hard haha!) I was putting in 8 instead of 64!:redface:
So based on the CORRECT number (0.444 like you say), I get:
(159 / 0.444) x 60 = 21486.49 fph
21486.49 / 5280 =...
More excellent feedback! Thanks a ton guys. Keep it comin' if you've got it!
Etudiant,
I trust your calculations more than mine. Based on a set of calculations I found on another forum, my CPM to MPH calculation goes as follows:
(CFM / Sq. Feet Of Test Area) * 60 = fph
fph / 5280 = mph
That...
Thanks for the feedback! Luckily I was able to find a 9" diameter fan DC cooling fan that moves about 159 CFM, and so I'm planning to use that one. My plan is now to go with a 9" fan, mounted at the end of a diffuser section 10" square at its max width. The test section will be 8"x8"x14", and...
Hello,
My name is Ryan and I'm a volunteer instructor with the local Royal Canadian Air Cadet squadron. I'm looking for ways to try and make the kids' aviation lessons more interactive and hands on, and so I've decided I'd like to build them a small wind tunnel, purely for flow visualization...