Wind tunnel smoke

Hi LdV,

I would also like to know what the big boys use ??

I have built a 3.5 metre long wind tunnel in the garage and have been using a high speed camera at 125 frames per second to observe a 1:10 scale - wind turbine, I am designing.

I have used dry ice in warm water, and because it is heavier than air, I quickly found the couple of trays in the tunnel run out in a second or two, at a wind speed of 2 m/sec.

I am building a reservoir to fill and then flood the entry, somewhere about 2-3 metres cubed, like a tower, with a knife gate valve at the bottom ...........

This can then be dumped when the wind tunnel and turbine are at the required speeds for observation.

I hope somebody can enlighten us all with "The GOOD smoke" .....

Regards,

Macker

One homebrew device (that works...) is fixing 2 hypodermic needles so that their points are close together and slowly piping into them small quantities of ammonia gas through one and hydrochloric acid gas through the second. Although both gases are poisonous the result of the reaction between them is ammonium chloride which is a relatively inoccuous white solid. What you get is a thin stream of white 'smoke'. Arranging a row of such devices alows you to see and photograph aerodynamic stream lines. Beware of the toxicity and find out about the relative gas flows needed so that you can properly make the adjustments.

Some manufacturers used to sell small 'puffers' which made little white clouds that you could follow. I haven't seen them around for some time.

Google and enjoy.

What do they use in those smoke machines used in discos / parties etc...?

That must be pretty innocuous to use in a public place...

I know the smoke machines are filled with a liquid which is heated when smoke is needed...

John.

Hey all.

Commercial "fog machines" use a mixture of propelyne glycol glycerine and water. Roscoe makes a very good one. We use the term Fog machine and not smoke in the industry because these macines are not actually burning anything. The trick is to make your "needle stream" because compressing the fog stream (actually tiny drops of water and glycerine) tends to make the fog sublimate back out. Leave an air gap between the nozzle of the machien and the tube to crudely venuri the vapor through the tube will help. I don't know how thin a stream you need.

A small steram generator might work too.

Have fun with it.

Dear all

Thank you for your info which was very usefull.

I also found a site windsolutions .com that has affordable small machines with inocuous fluid.

Also one can make smoke by mixing sugar and salpetre and baking soda as a retarder.

It is easy but needs care when heating the mixture slowly so that it does not self ignite. The problem is how to dose it for wind tunnel needle aplications.

Regards

I seem to remember that wind tunnel testing used to use Titanium Tetra chloride to generate smoke.

Ya. - But this is not something for the kindergarten set to play with.

Tear gas makes a pretty white smoke too!

Hmmmm I seem to remember from school days that mixing bleach (sodium hypochlorite?) with brake fluid (hydroscopic) produced large quantities of a smoke like substance...

Don't know how dangerous the smoke is though...

John.

thanks for the idea but i want to know this is dengerous to do? and i don't know how does "propelyne glycol glycerine" look like.

thank you

Try www.kanomax-usa.com & download their catalog. They have a smoke generator for wind tunnel testing, as well as a distribution header (to get the nicely spaced streams).

for a small scale wind tunnel (around 5 inch diameter) I used two funnels (one either end of a central clear pipe) and a stack of drinking straws (cut into 3 to increase the ammount and reduce the length). Then popped a smoke pellet in the pouring end of one funnel and a vacuum cleaner hose on the end of the other. The straws straighten out the ariflow and the smoke pellet provides plenty of smoke (for around 45 seconds). Moving the vacuum hose forward and backwards in relation to the funnel gave a harder or slower pull - enabling me to change the airspeed.

Basic diagram here: http://www.crowcrow.com/image/wind_tunnel.jpg

Where does one find the smoke pellet? My son is trying to build a wind tunnel to test model car aerodynamics.

You can use poly glycol, Its used in all kinds of foods. I made a smoke machine for work using a small space heater, a gas tank from a lawn mower. With a coil and a little air pressure it makes quite a bit of smoke. We have another one that uses electricity to heat the fluid in a wand and do pin point tests.

You can buy cans of fake smoke at most hardwhare stores. They are normally used for testing smoke detectors. Good luck!

I used to work in the tunnels at NASA. Find Lenord Weinstein's paper on smoke wands in the NASA database. It is cheap and will give you great smoke. I teach now at WVU. email me if you need help. pgall@mail.wvu.edu

Pete Gall

Pete,

How about a link to Leonard Weinstein's paper?

http://www.freepatentsonline.com/4493211.pdf

Hi Pete I made a smoke generator for my low speed wind tunnel, similar to NASA' smoke generator (Robelen) , and UNIVERSITY OF WASHINGTON's. But I can t achieve good result. Problem is how to inject smoke into tunnel? Please help me. what is your e mail?

http://www.aa.washington.edu/uwal/download/documents/smokegen.pdf

The very best, and lowest cost thing is a fog machine they use for stage shows. Eliminator EF-400 Fog Machine on EBay. It costs about $30. Hook up a hose to it and spew a stready stream of fog where you want. It works awesome.