Wind flow experiments

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I'd like to experimentally simulate air flow turbulences around obstacles. Building the obstacles in one thing, but providing a well characterised flow (and mix it with something visible like smoke...) is something else. In general, I think the whole idea is easier to acomplish compared to fluid turbulences in a water tank.
Any ideas for an air blow device where I know how fast the air is flowing and how I could regulate the velocity? Hairdryer is tricky as it introduces temperature. Any DIY tutorials for something of this sort - I didn't find any and am also no electronics guy to build and program sophisticated stuff myself...if anything, more the wood, saw, and nails type.
Thank you very much.
 

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  • #2
Nidum
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Wind tunnel made from cardboard boxes . Clear viewing sections from Plexiglas . Cold air room fan for wind flow . Wool tufts to show flow patterns .
 
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  • #3
berkeman
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I'd like to experimentally simulate air flow turbulences around obstacles. Building the obstacles in one thing, but providing a well characterised flow (and mix it with something visible like smoke...) is something else. In general, I think the whole idea is easier to acomplish compared to fluid turbulences in a water tank.
Any ideas for an air blow device where I know how fast the air is flowing and how I could regulate the velocity? Hairdryer is tricky as it introduces temperature. Any DIY tutorials for something of this sort - I didn't find any and am also no electronics guy to build and program sophisticated stuff myself...if anything, more the wood, saw, and nails type.
Thank you very much.
Here is an old thread on a DIY wind tunnel (it is first in the list of Similar Discussions at the bottom of the page):

https://www.physicsforums.com/threads/designing-an-experiment-w-a-wind-tunnel.299053/

I remember a few other similar threads -- maybe do a PF search to find them. I remember one in particular where the student did a great job making a honeycomb diffuser to improve his airflow uniformity... :smile:
 
  • #4
berkeman
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Here is the thread I was remembering. Nice small DIY wind tunnel for experiments.

https://www.physicsforums.com/threads/my-homemade-wind-tunnel.771179/

BTW, if you do a forum search on this, use Wind Tunnel -Vertical

The reason is that we had a long thread about Vertical Wind Tunnels, and those posts won't help you out. Adding the -Vertical excludes those posts from the search results.
 
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I remember the myth busters made a wind tunnel out of a box fan and a bunch of straws to eliminate the buffering from the blades.

Is there a reason you can't simply simulate it?
 
  • #6
boneh3ad
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It would be extraordinarily hard to manufacture a DIY tunnel out of things like cardboard boxes that gave you a flow quality high enough to have a meaningful approximation of what would happen in the atmosphere. You'd definitely need to use a honeycomb (or straws) to smooth out the incoming flow and you would want to have your fan be downstream of your test section pulling air through it rather than blowing through it.
 
  • #7
tech99
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It would be extraordinarily hard to manufacture a DIY tunnel out of things like cardboard boxes that gave you a flow quality high enough to have a meaningful approximation of what would happen in the atmosphere. You'd definitely need to use a honeycomb (or straws) to smooth out the incoming flow and you would want to have your fan be downstream of your test section pulling air through it rather than blowing through it.
There is a design for a home made wind tunnel using a household fan on the NASA web site, which I made for school children for testing cars. It is based on the design used by the Wright brothers and uses a sucker fan, with a bundle of straws, as mentioned. I think a problem is how to measure force. It is also difficult to obtain a lot of safe smoke, but you can buy a smoke stick to do this I think.
The Wright brothers initially tested their wing by mounting it on a beam on the handlebars of a bicycle, when they balanced their wing forces against those on a flat plate. They adjusted the geometry to test various angles of attack and find lift or drag coefficients.
It is also possible to plot airflows using electrolytic paper or using an electrolytic tank.
 
  • #8
boneh3ad
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It's actually not that hard to make smoke. Mineral oil and a thin wire of heated wire will give you a nice effect. It really just depends on what you hope to achieve with the tunnel. For simple demonstration you don't need anything fancy. To get actual data that is scientifically useful, you need a lot more thought.
 

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