h a l f b a k e r yContrary to popular belief
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CoandaTornado
ooh, my gut tells me that this idea that popped into my head today might be a good'er | |
Rising heat can be made to tornado if given a little nudge. This has led to conjecture that it might be possible to use this phenomenon to create chimneys out of thin air without the need for a huge towering stack for solar updraft towers. I think that is a stellar idea, but... again the heat is
just thrown away after it exits the turbine chamber.
What if, instead of building a solid chimney, one were to construct a scaffold-like tower which is open to the air with only enough support to safely suspend a hemispherical cap, (round end up), designed to match the diameter that the tornado will be at that height.
The center of the hemisphere is cut away and above this is a parabolic funnel shape with the turbine blades ringing it.
In this case the heated air entering the bottom of the hemisphere is directed at ninety degrees to its former direction of flow in order to escape and turns the blades of the turbine in passing. The air then flows radially outwards in all directions but the negative pressure beneath the hemisphere created by the uprising tornado causes this radially directed hot air to bend downwards due to the Coanda effect and is eventually dragged back into the swirling vortex at its base following a path of least resistance and conserving almost every bit of the excess heat which would normally have been tossed away.
Basically it would be wrapping a tornado back on itself, or making a spinning vortex ring comprised of spinning vortex rings.
I think I might try welding a small model and see if I can get a camp-fire tornado to wrap back on itself.
It would look just like a magnetic field made of flaming swirls.
...and I'll probably also toss in a few handfuls of metallic salts at some point. You know, for science.
: ]
Coanda tornado 1
https://imgur.com/Ha3IPOv
pencil sketch [2 fries shy of a happy meal, Feb 05 2018]
Coanda tornado 2
https://imgur.com/RK4Mzkk
marker sketch with some weird ghosting thing going on beneath it I didn't draw. [2 fries shy of a happy meal, Feb 05 2018]
Not this, but sort of similar...
http://globalwarmin...mneyPlusBellJar.pdf
Solar Chimney with Bell Jar... [DamianMitchell, Mar 01 2018]
Prototype # 1
https://imgur.com/gallery/sWbA9
[2 fries shy of a happy meal, Mar 01 2018]
Schlieren Photography
https://en.wikipedi...hlieren_photography
How to take photos/video of the workin's... [neutrinos_shadow, Mar 04 2018]
(?) Prototype # 2
https://www.youtube...watch?v=MPFCoHIDQ4U
not as good as the original [2 fries shy of a happy meal, Mar 11 2018]
Another kick at the cat.
https://www.youtube...ms&feature=youtu.be
<note to self> heat tape not meant for open flame. [2 fries shy of a happy meal, Mar 18 2018]
[link]
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Wait a minute. I thought a convection current needed cooler fluid
crowding in at the bottom to sustain it. If you return the hot fluid
from the top to the bottom (by coanda) without dumping its heat
on the way, won't you somehow undermine the convection
process? |
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I don't know. This just popped in full-blown.
I see the camp-fire tornado being fed by cold air drawn in at the base of the fire, and the Coanda effect curling the fire streams downwards and re-entering the maelstrom above the level of the burning fuel. Since the turbine would be located at the uppermost point in the system the heated air would be trapped and pass through the turbine again and again until the heat energy dissipates. |
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You'd get a convection current with a cold air intake 'and' a conservation of heat loss from vortex-ing the vortex... I think. |
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I could be wrong, but the visual I got was totally awesome and I want to play with it either way. |
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//What about birdstrike?//
yum. Just set up plates to catch the nicely grilled avian morsel. |
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Scaffold might be the limiter. Poking a subtle dynamic system is hard to engineer finitely. Not saying it's not possible though. |
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//birdstrike//
I think that the airflow from the vortex would deter birds and insects almost like an elliptical, hmmm or maybe egg shaped, force field of extremely hot air leaving secondary vortices in its wake. |
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//Scaffold might be the limiter.//
Good point. I figure as long as all of the inward facing surfaces are curved to follow the swirling of the air then the inner tornado will be effectively channelled while allowing the... Coandized air to re-enter the initial tornado wherever it feels comfortable doing so along its way to the ground.
Since convection begins above the heat source, the majority of the waste heat should be sucked in right nice and close to the base if the geometry fits the BTU's |
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On a side note; did you know that the proper decomposition of wood chips gives off the same BTU's as combusting the wood but over a longer time? ...and when it's done giving off its heat it becomes topsoil instead of released carbon. |
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So you're doing sort of fire sculpture? Like that idea. Any
chance of uploading a
rough sketch? I think I get it but a sketch would be cool. |
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If it's what I think it is it's a neat idea. |
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That link is great. That was certainly what I had in mind for the campfire version. |
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Ok I did a quick felt marker sketch. My wife and I sold our house and we're kinda currently living in a camper for the winter until we find our next place, so I'll have to sweet talk her into scanning it at work come Monday. |
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ps. it's not the greatest sketch. |
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This sounds very much like a crossover between a plug nozzle rocket motor and a vortex cannon, both of which are Baked and WKTE. |
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Maybe, but I don't think so. Nothing leaves any sort of launcher, the vortex just sort of sits there twisting and swirling back on itself over and over turning a fan until all of the heat of the fire or the compost heap dissipates. |
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Heat is heat after all. Fire is just the most easy to visualise airflow. |
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[2 fries] What device are you posting this on? |
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Obviously then , not fitted with a webcam nor do you possess a camera or cellphone in this period of pixel transportation. |
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Oh, As an absolute last resort there's Paint. |
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I now have an image of [2 fries] sitting around a campfire,
slightly misty-eyed, with a can of Kokanee in his hand
singing Oh Coanda. |
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Funny, we are waiting for an offer on a campground/rv park to be accepted so your vision might be clearer than you think... except about the Kokanee bit. Watered down piss-water that, but in a pinch, and if they're cold enough I can be tempted. |
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Yeah I guess worse comes to worse I could always snap a phone pic and upload that next time. Scanned the sketches and I just need to put them in photobucket. Give me a second or eight. |
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Ok, a little bit later... photobucket doesn't like that I've used their free image hosting for years without paying anything and I just get bounced from there now, so... Imgur it is for now. |
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[couple of links]
The pencil sketch is too light and the marker sketch shows no detail but between the two it should make sense. |
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...also with the color sketch the flaming streamers would twist around the outer diameter of the... I don't know the word... fire-backwash I guess, and not be entirely vertical but more of an undulating sheet sort of like a roiling plasma with little fire tornados spinning off at random, but I couldn't draw what I see in my head. |
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My gut feeling is that the Coanda loopback stream will be be unstable a) because the system is open to environmental conditions (look at the structure in the video to just do the tornado) and b) the flow has to deal with being a fraction flowing back down, spread out over a sphere around the upmoving tornado. |
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Maybe an initial push or fanning can set up the right conditions to get that second level that will loop the tornado all the way around. Experimenting with a tornado flame, with your structures, next to a constant downdraft may indicate plausibility. |
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Yeah, all I've got to do is play with heights and diameters and curves of the geometry. I'll show you... just give me a bit of time. |
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<side note> I learned two new things today. Almost had a melt-down. The stimulus has been overwhelming.
I'm gonna go lie down for a bit. |
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So... I just wondered something. |
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If more and more heat is pumped into a system which torus-es back on itself and that heat is not allowed to leave... will the temperature amplify, or will the torus ring itself increase to trap the heated air? |
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Will this create the ultimate smoke-stack particulate scrubber since no particles will be able to exit the system until their heat had dissipated and they have agglomerated into clumps large enough to precipitate out of the convection current? |
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Will BC residents no longer have to maintain no campfires during the summer-fire-ban if no sparks can leave the fire? |
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If a large enough volume of heated air could be kept coherent without needing a sack to contain the air-mass within, would we be able to make hot air balloons with no fabric? |
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So, the fire sends hot air upwards; somehow you convince it to tornadate. At the top blades pull some energy out into a generator or merry-go-round or something, and send the air across the top of the dome, sans rotation. |
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Whence laminar flow takes over and the air flows down the sides and reenters through the bottom of the dome, still retaining enough buoyancy to make the exercise worthwhile as it goes through the turbine, again. |
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My kneejerk reaction is broken bootstraps. But... |
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We'll see. I've scrounged almost all of the metal parts I need to make a small alcohol burning version. |
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I just need to buy a metal-cutting hole saw after work today. |
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" What about birdstrike? " |
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I'll test that theory out and we'll see how well it works. |
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How long were you thinking this test might continue? |
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That's a valid question. I believe in order to answer that properly, I'd need some data, an initial assessment of what that data indicates, and some theory that I could validate or disprove. |
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Ha!
It's Alive! IT"S ALIVE!!! |
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Awesome link [DamianMitchell]. I never would have stumbled on that in a million years. |
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Ok, so I built a prototype today at work and I was totally stoked at the initial results.
It seems to be a balancing act between the amount of heat in the system and the shape needed to channel it all. To recreate this experiment you will need: |
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-A three inch metal hole saw and drill
-Needle nose pliers
-Flammable liquid, (I used spray solvent)
-1 soda can bottom.
-1 tin-can cylinder cut in half.
-2 salad bowls, (I used two dissimilar objects and you can tell that this affects the vortex)
-1 angel food cake insert, (I used the base from a tin candy tray)
-Some framework, (bent coat-hangers will do) |
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The funnel shape needs to as closely approximate the inverted Coanda hemisphere as possible. The less wiggle room between the two, the better the effect is going to be but it certainly appears stable and scalable. |
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I know. I know. Pics or it didn't happen.
[link] |
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You can clearly see how, when the amount of fuel died down to where the heat more closely matched the shape, all of the soot from the fuel and blackening paint is wrapped back into the tornado. |
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This gives me great hope for its use as a future filtration system for factories. |
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If the smallest particulates are the easiest to heat they will remain trapped in the vortex until they weigh enough to leave it and drop like rain. |
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Now, about that container-less vortex hot air balloon idea... |
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Oh yeah, it will make a huge difference when the funnel shape comes down to a proper point as well, rather than being blunt like this one. |
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If it was designed by somebody who knows a thing or three and built out of aerogel or some other insulating material then this little widget is going to have efficiencies in the high ninety percent range. Muhahahahaha! |
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I like it!
and I'm adding it to my top ten-ish list. |
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OK; it's a pity the still photos can't convey the vortical flows very
well, and the turbines and //magnetic field made of flaming
swirls// must be left to the imagination. Given that, the clever
part of what we *can* see is that the upper bowl isn't black
inside? I'm not trying to belittle what you've made - I expect the
Michelson-Morley experiment didn't look like much - I'm just
trying to understand it. Am I looking at it right? |
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I hope so.
I'm going to scrounge better parts and give it another go with video.
In the upper image that smudge you can see on the left hand side is the smoke curling back under the dome. That only happened when the fuel was almost gone.
Before that only a portion returned to the system. |
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It will take a much larger set-up and night time viewing to see any of the plasma/magnetic field effect because the flame will be almost blue when stretched that thin. The turbine concept will be much farther down the road. |
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It's simple really. The tornado wants to stay cohesive and new heat entering the base forces the tornado outwards and downwards.
Because of the lower air pressure under the dome the airflow becomes a torus and re-enters the vortex more easily than rising upwards.
So instead of needing a great height to achieve the chimney effect we can build wider instead of taller and keep the heat. |
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I wonder if the flows can be tagged for visual tracing. Maybe a non combustible confetti or dust? |
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I was thinking about that. The black smoke against the white background of snow doesn't show up on film as well as in person.
Everybody around me seems to be vaping nowadays. I wonder if the vapor would remain visible and backlit by the flame. |
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Maybe a little dropper bottle that can act as a light puffer, don't want to disturb the air flow though. Even something that when combusted would give little fairy lights of indication, like burning embers floating free from a fire. |
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A pinch of magnesium powder? |
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Yes even gentle airflow greatly effects the initial tornado action. Extending the point of the cone and increasing the diameter of the Coanda hemisphere and its chimney-hole will fix that as the tornado will become trapped much sooner around a solid core so that a breeze will only cause it to deform rather than miss the cone entirely, but the next test will definitely be indoors or at least in an alcove.
I really didn't expect the first knock-up to give positive results until I could stumble on better shapes to make it from than the ones I'd found so far in the thrift shops I've had time to visit.
I was right tickled I was. Did a little jig and everything. Other contractors watching me put this thing together all morning, when I should have been working, shaking their heads, then the looks on their faces when I fired that puppy up...
Absolutely priceless. |
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hmmm, a sparkler resting across the flame for the video trial should do the trick.
Some nice mood lighting, maybe a bottle of wine, a little Teddy Pendergrass playing low in the background... |
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She'll be mine,
oh yes,
she will be mine. |
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[2 fries shy of a happy meal], nice work!
Two words for you: Schlieren Effect. See linky.
Also, if no-one else at my work is using the license, I could get access to SolidWorks Computational Fluid Dynamics software. If you send me some dimensioned sketches, I could try to model what is going on; mostly because it would be fun, but also to find tweaks etc. |
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Sweet!
I will probably need to meet somebody more familiar with photography to tackle any of those Schlieren techniques. Cool concept though, realising that pressure waves warp light and figuring out how to capture that on film.
I will measure all of the dimensions of this next version which should work a lot better than the first. |
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Computer modelling would take aspects of this concept way farther than I can prototype my way through. |
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Um, I might want to measure that first model rather than the latest one.
Total crash and burn... literally. Tower collapsed under the weight of the new set up just as the video got set up and all there is to see is a small wedge of blue tornado, the sparklers going off and then the camera swinging back and forth capturing and ever widening puddle of flaming gas line antifreeze burning on the picnic table. |
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By the way, the lithium from watch batteries doesn't really turn a flame red much at all. |
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Ok, one more time from the top! |
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I sent you details of the first prototype [neutrinos_shadow] hope I got your email right. |
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Built a second one and filmed it at night with a sparkler but it doesn't seem to work nearly as well as the first one. [link]
I think that the lip on the funnel section, which I removed for the second version, is creating a secondary counter-rotating vortex within the dome which, once trapped, is expanding with the heat and channeling the tornado downwards more efficiently than if the flow were perfectly laminar. |
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:-(
Prototype 2: "This video is unavailable" |
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hmmm it loads for me. I have it set on Public so anyone should be able to see it. |
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Did my email make it to you? If not I will post it here as another link. |
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Too windy. Color flame candles disappointing. Heat tape catching on fire good for a chuckle though. |
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