Homemade Wind Tunnel?

[donpearsall]

I want to try to simulate a wind tunnel speed with my gas lawn blowers (200 mph air speed). But I don't know what to use for a smoke source. Has anyone done this? What can be used for a smoke stream. In real wind tunnels I have seen them use a wand that emits a thin stream of white smoke. Any ideas?

Don
MPS-BG 1300

[interested bystander]

You can buy smoke  liquid (which has to be heated by a smoke generator) from a theatrical costume store- we've not been successful with getting airflow and smoke flow coordinated- and we're only interested in flow visualization, not Cd, or lift numbers- good luck.

(I hope this subject generates some feed back cause we're stymied by our attempts)

[Glen]

Some of the scientific supply store sell smoke generators. Over the years in aero space I have seen several made in the shop. They can be simple or complex depending on what the engineers want. I believe you might get some help from HVAC people as they test air flow in ducting with smoke.

[Bob Drury]

Don, when Marlo Treit was wind tunneling his 4 foot model of his new streamliner, they used a liquid chalk painted on the car.  When it dried it stayed on the car until the wind hit it, then it moved around in the wind. showing the patterns as the wind hit the car.  Enough was left in trace paterns, that the car could be studied afterwards.  I am not sure, but I think there might be pictures of the testing on NitroGeazers.com.

[1212FBGS]

the smoke stream is done by a wand. the smoke visualization is done at very slow wind speed  usually when the tunnel wind speed is slowing down. it is a long tubing with a hose that siphon's the smoke from another room. what i do on my liner is mix blue chalk with wd40 and spray it onto the car before a pass, the wind blows the chalky mixture around and evaporates the solvents in the wd40 and leaves the chalky oily residue on the car for examination. works great
kent

[Sumner]

the smoke stream is done by a wand. the smoke visualization is done at very slow wind speed  usually when the tunnel wind speed is slowing down. it is a long tubing with a hose that siphon's the smoke from another room. what i do on my liner is mix blue chalk with wd40 and spray it onto the car before a pass, the wind blows the chalky mixture around and evaporates the solvents in the wd40 and leaves the chalky oily residue on the car for examination. works great
kent

Kent have you made any changes based on what you have seen?

Bob I couldn't get " NitroGeazers.com " to work.  Is it the Target 550 ( http://www.target550.com/ )site ?

c ya, Sum

[Bob Drury]

Sum, sorry, its Nitrogeezers.com.  Then go to LSR, then to Treit & Davenport.  Sorry to say no tunnel stuff, but lots of neat construction pictures.  I will see if I can get Marlo to download some tunnel pictures....

[1212FBGS]

sum
yeh we would bondo up or sand down areas. mostly you can find areas of seperation cuz the chalk would puddle so ya fill it with bondo to fair in the area to keep the air laminer. if ya see long clean areas we add trip tape. alot of fiddlin but worth it if ya are lookin for 1 or 2 mph

[Sumner]

sum
yeh we would bondo up or sand down areas. mostly you can find areas of seperation cuz the chalk would puddle so ya fill it with bondo to fair in the area to keep the air laminer. if ya see long clean areas we add trip tape. alot of fiddlin but worth it if ya are lookin for 1 or 2 mph

Good info, thanks.  What is "trip tape"?

Sum

P.S.  I almost inserted a wise remark that I'm hoping to go more than 1 or 2 mph, but you noticed I left it out .

[1212FBGS]

its this stuff ya can get from aircraft spruce that looks like thick scotch tape. you can get it in zigzag or dimpled tape. you put it in an area 2 reduce skin friction. they use it primarily on glider wings to reduce drag and increase lift. cool stuff
kr

[Reverend Hedgash]

Trip tape creates a rough place for the laminer flow to "trip over" into minor turbulence before separation occurs due to body shape.

This reduces drag because this turbulence keeps the flowing air closer to the body than if it wasn't there, therefore reducing profile drag.

Trip tape needs to be placed carefully for it to work, put it too close to the front of the car and it will reduce your laminer flow prematurely creating more drag, too far and it will be too shallow to have any effect.

Kent's gap method with the chalk is a neat method. Carbon black and kero is another.

rev.H+
 Hey Sum, read your stuff on your front end... how's it going?

[dirtydave]

As what you guys are talking about almost new to me,
coming from my drag racing back ground and with the current cnc porting machinery, one can program the dimple golf ball affect into a cylinder head port for major gains in CFM as a polished ports are sticky and take the air fuel mixture out of carburation,
Alzo painting a vehicle in a matt finish will also make it more slippery yehh???  but slippery is not alwayz goot ya...?

[tomsmith]

I was reading up on sailplane turbulators (thanks to piquing my interest by reading stuff posted here) and found this site:

http://www.sinhatech.com/auto.asp

They purport to have a product that works sort of like a turbulator but does not increase drag like turbulator strips do.  They call it an "unturbulator".  The development was originally for aircraft wings.  Maybe I'll try their product on my daughter-in-law's V-8 Toyota 4Runner when it becomes available (they claim in about a month) - she needs to get better mileage.  Do you suppose this complements the Nish vortex generator strips?  The "Sinhatech" stuff goes near the leading edge laminar bubble separation, where the vortex generator tape goes near the aft body when "Kamm effect" is used,  where the body tapering stops.  Fascinating.  I wonder what it all means.

[Sumner]

Trip tape creates a rough place for the laminer flow to "trip over" into minor turbulence before separation occurs due to body shape.

This reduces drag because this turbulence keeps the flowing air closer to the body than if it wasn't there, therefore reducing profile drag............

That is a better explaination than in all the stuff I've read on the internet and the Leading Edge book.  I kept trying to figure out how messing up the flow actually helped it.  Now I see, I think .

....Hey Sum, read your stuff on your front end... how's it going?

   

Well I'm back to work on it.  I hope to get the front axles finished over the weekend if I live through getting a wisdom tooth pulled Thursday.  The front is going to envolve making lots of parts, so I'll feel good if I'm done with it by August.  Then I hope it works .

Less than 9 months till you guys go racing, so keep with it .  I'm even starting to see problems being done a year from now.  

c ya, Sum

[Bob Drury]

This question I guess would be for Dan Warner.  Would this tape be considered a vortex generator?  Thanx, Bob