Wind table (laminar flow table)

[Tyler Swain]

http://blogs.exploratorium.edu/tinkering/tag/wind-table/

 

I am always impressed by what the Exploratorium does, and I have been following this project by them for awhile.  How difficult do you think it would be to build one of these?  The wind tables are an expanded version of the Wind tube exhibit they have in their museum.       

 

Tyler Swain

Creative Arts Lead

 

Omaha Children's Museum

500 South 20th Street

Omaha, NE 68102

Tsw...@ocm.org

www.ocm.org

 

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[David Knaack]

Technically a very easy build. I'd think most of the time would probably go into making it look good (unless it was a modification of an existing table).

I would suggest making the straws an easily replaceable component, so that when it gets beat up, or maybe if a specific design is desired as a theme a new insert can be constructed and dropped in. The base of the insert above the plenum could be made of window screen over hardware cloth, with a wide-spaced grid of aluminum strap underneath to eliminate droop.

For an air source I'd think a commercial squirrel-cage blower from an HVAC system would work well. Direct the output horizontally into the plenum, with defusers to break up the stream. 

A layer of material to create a little bit of back-pressure in the plenum immediately before the laminar stack would probably help, perhaps a layer or two of high-loft quilt batting or similar backed by window screen. That would necessitate a dust filter on the front end though, or the whole thing would eventually clog up. Depending on how well the defusers were configured you could probably get away without that.

Without a filter though the window screen is going to eventually get crudded up. You could remove that and go with just the 1/4" hardware cloth, but if you do that you have to bond the straws together, which makes building that component more time consuming. Instead of just stacking them and putting them under a little compression to prevent them being pulled out you have to put some adhesive on them to avoid having them pushed down into the plenum. I'd go with a filter on the intake, but that creates a periodic maintenance task that may or may not work well where you are deploying it.

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[Tyler Swain]

When I first saw the design for them I thought of the squirrel cage as well, as one of our large exhibit pieces, the Super Gravitron, uses them to move balls all over the place.   It looks like the exporatorium  is using 3 heavy duty vornado fans.

[David Knaack]

I suggest squirrel-cage mostly because they produce much more static pressure than an axial fan, so you have more freedom to use flow restrictions to pressurize a plenum evenly, which makes it easier to avoid uneven flow in the output stream. If you use a coaxial fan you might be better off with a duct design that minimizes back-pressure while using vanes to redirecting flow to minimize pressure differences. 

Also, I'm not sure about noise. IME squirrel-cages tend to be quieter for a give CFM, but maybe I'm just used to cheap fans.

[Kevin Fusselman]

It seems straight forward, if a bit expensive, due to the quantity of materials required... A big fan and some pipe...

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