# Full sized Wind Tunnel

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#### sandman

##### Well-Known Member
I know all the computer software is great for simulations but...I always thought about making a full sized (for model rockets!) wind tunnel as a kid.

I was thinking of using heating ductwork.

An area in the center for the model and a viewing window.

Laminar flow streamers

Now for the motors!...Electrics or Gasoline...like an old lawn mower engine. Maybe 6 HP.

The fan is a problem...what to use.

The design should be available online someplace. Or some kind of calculations for fan size, HP output, Throat size (venturi area).

Might make a great "dust collector system for my shop too!

sandman

#### gerbs4me

##### Well-Known Member
This sounds like a great idea, probably an electric motor would be best, since no exhaust.

#### Elbmod

##### Well-Known Member
Hi Sandman

Have you looked at the Estes Education Technical Notes, there are some ideas for a wind tunnel there (Technical Note TR-5) - drop me a line if you want a copy.

As for other considerations - a colleague of mine (I'm a teacher) has just built one for some physics coursework projects - fashioned after the ones he used during his PhD. He recommends centrifugal fans arranged to "suck" rather than"blow" as apparently this creates more laminar air flow. Electric motors have to appeal because they are quieter!

#### Zippy

##### Well-Known Member
Leaf blower, outside so you can really anoy the neighbors.

#### Juerg

##### Well-Known Member
The problem with the leaf blower: It is hard to get a laminar airflow of the reqired size, this would take a rather long wind tunnel.

#### illini

##### Well-Known Member
Another thing to consider is to place a window screen upstream of the test section. This will help to break up large turbulent eddies into much smaller, nearly isotropic ones that will be rapidly consumed by viscosity.

Big whorls have little whorls that feed on their velocity,
And little whorls have lesser whorls, and so on to viscosity

-- Lewis F. Richardson, (from his 1920 paper) --

#### sandman

##### Well-Known Member
My brother is a plumber/heating contractor. Her was going to make the ductwork for me after I designed it.

I'm sure he may have a few old used furnace fans laying around!

sandman

#### Zippy

##### Well-Known Member
The problem with the leaf blower: It is hard to get a laminar airflow of the reqired size, this would take a rather long wind tunnel.
To get closer to laminar airflow an old racing trick can be used.
Vanes in the hood scoop, or in this case vanes at the front of the tunnel.

#### bobkrech

##### Well-Known Member
The typical way to build a good quality wind tunnel is to decide the test section cross-section and the flow velocity you want. Once you do this the rest is relatively easy. The crossection will depend on the amount of blockage you are willing to put up with, but typically you want keep it to a few percent.

Check out http://www.aerorocket.com/offer.html for some details.

This is not a particularly large or high speed tunnel. A high speed tunnel is not cheap to build. Our inhouse 1 ft square tunnel cost $10,000+ and has a 10+ hp motor. It occupies a 40' x 16' x 9' and the airflow in the room during operation is awesome. You also might want to checkout http://www.aerorocket.com/tunnel.html and http://www.aerorocket.com/offer.html for wind tunnel testing in this tunnel. Bob Krech #### rkt2k1 ##### Well-Known Member Sandman, Here is a plans for a home made wind tunnel I found on the Internet. I thought you may find them useful. I'm also including a link to a site who built a wind tunnel based on these plans. They offer wind tunnel testing services for$25/hr!

AeroRocket Web Site - Wind Tunnel

#### rkt2k1

##### Well-Known Member
I should have refreshed my screen! Bob posted the same info!

That's what I get for helping my son setup his computer joystick to work with MS Flight Simulator 2004.

#### bobkrech

##### Well-Known Member
I should have refreshed my screen! Bob posted the same info!
LOL

Only goes to show that great minds think alike.

Bob Krech

#### sandman

##### Well-Known Member
Thanks guys!

I knew I wouldn't have to re-invent the wheel!

sandman

#### rkt2k1

##### Well-Known Member
I received the 2004 Pitsco "Ideas and Solutions" catalog in the mail today. They primarily provide science and technology materials to schools. The catalog is absolutely filled with cool gagets and kits. They even sell the full Estes line of model rockets. As I was looking through the magazine I came across the following item, which I just had to post to this thread. They have a number of very cool (also quite expensive) full (ie model) size wind tunnels and accessories. The pictures in the catalog our much better. I believe you can request a catalog online. (Not sure if there is any cost.) Here's the links:

AirTech Scout Wind Tunnel

AirTech X-Stream Wind Tunnel (with Stinger mount)

#### powderburner

##### Well-Known Member
I notice that a lot of the plans and ideas posted in the previous comments are for open-circuit tunnels.
What do some of you think of recommending a closed-circuit (or even a hybrid) design?
That way, Sandman could get higher speeds with a smaller motor, and they tend to be a bit quieter.

Sandman, the idea for the upstream screen (for better airflow quality) is a good one. A similar approach is to make a 'wall' of short tubes stacked on each other (wonder where we could find a bunch of tubes?). The purpose is to attain uniform pressure and velocity in all parts of the airflow as it enters the test section.
After that, you expand the cross-section area (to slow the flow) and turn the corner to return the flow. On the opposite side of the tunnel loop, you locate your drive fan(s). Then the flow has another set of turns, plus the flow-straightening wall, to settle back down and get ready to hit the test section again. The most important part of the circuit for 'good construction' and smooth tunnel walls is after the last turn, through the convergent section, and into the test section.