digital flow benching, smoke query-esque.... sorta thing....

[Bengstudent]

Hi all... Basically I have a slight issue. As a Uni assignment we were asked to flow a head. Fine and done... But I decided that what would be far better was validate a CFD model where I can do all the work digitally, including modifications. As part of this, Ive made (and are continuing to make) some basic tube sections such as this...

And some flow restrictors such as this....

and plan on running them through the flowbench with pressure and velocity sensors, plus a visulisation of smoke flowing through it all.

The problem is... I cant see the smoke...

http://smg.photobucket.com/albums/v66/Glaive/?action=view&current=MyMovie.mp4

So the question is... Does anyone have any idea's? I was thinking UV smoke. Or a chamber where I can make a smoke charge with a much higher concentration of smoke, or using combustable smoke pellets to increase density. But I'm at a bit of a loss... Anyone have any idea's?

While it was a Uni assignment that made me start this project... Its not an assignment, or homework or anything like it. It just piqued my intetrest... Plus I like the look of Ansys.

So anyone fancy pitching in?

Thanks in advance,
Chris.

 

[MintJulep]

I saw your smoke sort of ok.

Start by just playing with lighting and background.

Try to get rid of the lighting reflections on the tubes. A solid dark background instead of half dark and half windows.

Maybe try an old-school black light.

 

[Bengstudent]

Yeah... Ive got a photography student coming to give me a hand. And we havent tried it mounted in the flow bench room, which only has flouresent lighting... So its possible we can use varied spotlights, etc... just looking for "Plan B's"

 

[btrueblood]

A smoke wand, i.e. very small diameter tubing, with which you can probe closer to walls, and which emits a much finer stream of smoke, might help.

Alternatively, oil and chalk, smeared on the walls, for visualization of boundary layer flows.

Third, telltales or short pieces of yarn, either attached to walls or along short wire "rakes".

A higher frame rate camera, or flash photos, to better "freeze" the motion.

Google Schlieren photography. Oh and Raman spectroscopy, but I don't know if you want to go that elaborate.

Lots of ideas, sorry about that.

 

[Bengstudent]

No, thats some lovely stuff to be looking at, thanks.

 

[franzh]

I heard what appeared to be a high velocity blower (suction) and cigarette smoke? I think a slower velocity would make the smoke more dense. In college, we used an oil based smoke and experimented with variable speed blowers. Boundary Layer Adhesion was an interesting study/demonstration and changed considerably with the wall diameter, restrictions, bends, and air velocity. Dont do like one former (emphasis on "former") student, and use Sulfur for smoke!

Franz

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[Bengstudent]

Hiya Franz.

It was basically a vacuum cleaner and a smoke machine to test the theory and get an idea of smoke visulisation... The next step is really lighting and combustable smoke, rather than smoke machine generated smoke. The issue is, it has to be at a high speed, as the flow bench opporates in that area.

The thing of it is, I need to keep it all pretty simple as I still have all my actual assignments to be doing and i cant really spend too much time looking at "interesting"... As well as this, theres a friction study of an engine, head development, hub centreed steering and gemotry work that needs doing.

But I think your stuff might be interesting over the holidays... And dont worry... No Sulphur based smoke

 

[1gibson]

I wonder if dry ice in densely colored water (food color again) would produce colored "smoke"?

I wrote out instructions to make smoke b-o-m-b-s with pottasium nitrate and sugar, but deleted it because these days it would probably get you arrested. Maybe try the small round commercial ones if you can.

 

[Bengstudent]

We've already ordered some chemicals to cook up... Thats one of the plan B's

 

[btrueblood]

Well, careful on the ratios if you go gibson's route. A few percent more nitrate and smoke generators become smoke boomers.

 

[patprimmer]

I'm not sure how the colour would be carried in CO2 vapour.

Regards
Pat
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