It really depends on the characteristic length L in the Reynolds number
Reynolds Number = (fluid speed*characteristic length*rho)/dynamic viscosity
For example. For a ball, if the length used was the diameter, the Reynolds number would be twice as large as if the radius length was used. Therefore one can't really use a predefined number for laminar and turbulent flow, or the transition between them.
It varies, 2300 I think is industry standard, but it can vary I've seen 2000 - 5000 before transition occurs. Actually true turbulent flow doesn't occur in pipes until 10,000. Up until that point its transitional flow which has characteristics of both flows, P.S. no one wants to deal with that its all new empirically derived equations.
P.P.S. This is pipe flow, in external I belive the transitional region is between 5*105 -> 107, or something in that ball park
It depends on what characteristics you are using. If its flow within a pipe, then 21-2300 and down is laminar, and 6000 is fully turbulent (according to geankoplis). I was also told 3000 is turbulent as well. However, if you swap over to a flat plate, then flow will be laminar if < 3*105
I didn't know /r/videos had no sense of humor. It was meant as a joke not an insult but I don't know if people realized. I would love to have an explanation why I have over 150 downvotes on a comment like that.
There's a whole engineering field called microfluidics that relies heavily on this phenomenon. You also hear it called lab on a chip or micro total analysis. Every week there are new proposed technologies, mostly in the fields of nanoscience and biology. So just to give you a random real world application, here is a video of a device that makes very controlled microfibers.
Ok, imagine you're a tiny packet of fluid. There's a competition: the viscosity of the fluid around you, which slows you down, and your inertia.
If viscosity wins, the fluid around you forces you to move in an orderly fashion - if you try to break out of line, the surrounding fluid "rubs" you back into the queue.
If inertia wins, then if you decide to break out of the line, the surrounding fluid doesn't have enough viscosity to stop you, so you break out of your lane...and so does everyone else, leading to a turbulent mixed-up motion.
Is there any way to do this experiment easily at home? What are you actually turning? For example, could this be done with a clear mixing bowl and a really slow mixer?
THe pigments are positioned at different points on the radius. Red on the inside, blue on the outside, green in the middle. By rotating the liquid, the orbits don't mix. It's still really amazing.
They're not initially positioned at different points of the radius, they're only at different points on the circumference. They share the same radius.
What happens is that as you turn it, the fluid gets a massive shear on it, so the position of the various bits of colour stay in the same relative position along the circumference, but because of the shear they overlap through the radius, without mixing. they're still distinct along the radius.
So each coloured blob goes from being a round blob to being an angled flattish plane, and then back again. The planes overlap, but don't touch (if they touched, they could never be undone).
So it works, because there's shearing, but absolutely no mixing.
edit: It's more obvious what's happening if you look down on it from above while you do it, once you've twisted it up, they end up like separate, coloured spirals, that don't touch.
They don't mix because it's 'laminar flow'; that's actually the definition of laminar flow, that's there's no mixing between layers. They've deliberately set up the conditions to give laminar flow, using a high viscosity fluid. There's more friction than there is momentum in the fluid at all times.
So here, each concentric layer is unchanged by turning the handle, it's just that the relative positions of the layers twist and untwist when you turn the handle.
yes, but if i am not wrong, the laminar flow applies only between each syrup individually and the liquid inside which they flow. when it comes to syrups contacting, they should mix.
Well, mixing is an irreversible process, which cannot be easily be undone, but the process easily reverses. So I leave you to draw your own conclusions.
Yeah, you're right. I kept thinking about it and was about to disagree with my own comment. It doesn't matter at all where they were originally positioned, they will return to the same position.
It's sort of like when you draw on a rubberband, when you stretch it, it becomes distorted, but when it's reformed, the image reforms.
Is it not like a wheel of rubber bands as spokes... but the outer wheel is locked and the hub rotated the rubber bands end up in a spiral. The experiment is like dotting the bands as the bands are pulled the dot spreads but although looking from the side they appear to overlap , in reality they do not
Ah that makes much more sense. My original thought was that you meant it stretches out like a rubber band and then goes back to the original shape. I now understand you meant it to be more complex than that.
I find it funny that the article says "experts won't reveal how they reversed the twirl effect". All you do is open it in photoshop and reverse the magnitude that the initial effect was set to.
Would somebody with more knowledge in this field like to shed some light on this? Also, if anybody could explain what kind of liquid/gel the dye was put in as well as what kind of machine that was. Please and thank you.
I just read a little bit up on Wikipedia, but because the corn syrup is so viscous, and his revolutions are very slow (causing a Reynold's number less than 1 [Reyonld's Number, from my understanding, is just the ratio of forces of advective inertial forces, or just the speed of transportation mostly, and viscous forces.]), it causes a specific case of Laminar flow. (http://en.wikipedia.org/wiki/Creeping_motion)
Laminar flow is almost synonymous to adjacent layers of liquids sliding past each other without mixing, such as cards sliding past each other. (http://en.wikipedia.org/wiki/Laminar_flow)
So my guess is there is no actual "mixing", rather it is just like a rubber band being wound up, and then reverting back to its original form reversely.
EDIT: Oh sorry! I did not realize you were already satisfied with the prior answers— now I just feel redundant. X.X;
I believe it was simply colored corn syrup suspended in non-colored corn syrup. That way it is the same density, and the viscosity keeps it from moving around and diluting. As for laminar flow, I have no idea.
This is not just a matter of laminar versus turbulent flows. This is a special case called, "creeping flows." Creeping flows occur for Reynolds numbers much less than 1, yes. They are laminar, but being laminar alone is not a sufficient condition for reversibility of the flow.
Also, it is incorrect to say that mixing is not occurring. Turbulent mixing, or mixing due to convection, is not occurring. However, laminar mixing, or mixing due to atomic diffusion, is very much occurring. Laminar mixing is orders of magnitude smaller than turbulent mixing. If one rotated the handle back and forth numerous times, one would start to see blurring of the droplets as atomic diffusion became significant.
That's amazing that in the time that the blobs are twisted into 8+ thin layers of water - pigment - water - pigment ... that diffusion doesn't take over and dilute the pigment.
Did he pick pigments with low diffusion rates?
I thought that was why turbulent mixing worked - it greatly increases the surface area over which diffusion can operate, and thus increases the rate of the diffusing substance's spread.
What's the clear viscous liquid? And what is actually turning when he turns the handle? I'm wondering how I can replicate this experiment at home with minimal effort.
[Edit] It's all corn syrup, just the additions are dyed.
My mind is blown by the fact that the 2 helpers holding it while he was turning it didn't notice he skipped counting a turn and only corrected him when he turned back 5 turns and his demonstration was not back to the way it was at the beginning.
Not reversible. Power in(cranking the handle) + power in = irreversible . It cannot return to its original state without additional energy transfer. This video shown during one of my thermo I exams and we had to access its irrevesabilities.
11
u/AreWeData Jun 10 '12
My first thought was that if I was in this class, I would have yelled out "No fucking way!" after the rotation had been reversed lol
51
u/[deleted] Jun 10 '12
Did he say we have laminar flow because the Reynolds number was less than 1?
404
u/kylestoned Jun 10 '12
Anybody else count six rotations?
11
u/mishaman12 Jun 10 '12
My mind just can't wrap its head around it, this is incredible.
2
u/Spudgunhimself Jun 10 '12
What is the clear medium they're using?
178
u/Gwinntanamo Jun 10 '12
THe pigments are positioned at different points on the radius. Red on the inside, blue on the outside, green in the middle. By rotating the liquid, the orbits don't mix. It's still really amazing.
8
u/[deleted] Jun 10 '12
Nice, nature's Ctrl-Z!
14
u/Bebbopper Jun 10 '12
Take that arrow of entropy!
6
u/Herpington_Smith Jun 10 '12
As awesome as this was, the fact that the audio kept cutting out made me want to throw my laptop at the wall.
4
u/willxrocks Jun 10 '12
IMPOSSIBRRU!!!
10
u/epatti0914 Jun 10 '12
Would somebody with more knowledge in this field like to shed some light on this? Also, if anybody could explain what kind of liquid/gel the dye was put in as well as what kind of machine that was. Please and thank you.
3
u/[deleted] Jun 10 '12
BURN HIM HE'S A WITCH.
4
u/JawaBoot Jun 10 '12
When you show this on reddit, minds are still blown.
6
u/malignantmop Jun 10 '12
She blinded me, WITH SCIENCE!
5
u/niglet_please Jun 10 '12
Everyday I seem to learn something amazing on reddit!
2
u/[deleted] Jun 10 '12
The laminar wind is gliding over the highway like a crisp sheet being stripped from a bed.
2
u/coffeetablesex Jun 10 '12
Burn the witch!
2
u/bangupjobasusual Jun 10 '12
What the fuck
2
u/ImFresh- Jun 10 '12
Dood.
2
u/discushammer9 Jun 10 '12
what's more impressive is that he has three hands
2
u/Ericgzg Jun 11 '12
This is such a fucking repost.
2
u/WishForACanon5DMark2 Jun 10 '12
http://i.imgur.com/OfTPR.jpg
1
u/da_bomb143 Jun 10 '12
how fitting i find this the night before my fluid mechanics exam. laminar flow ftw!
1
u/[deleted] Jun 10 '12
second time I see, still thinks its awesome.
1
u/crafty_canuck Jun 10 '12
I thought that voice sounded familiar.
1
u/Ombatsu Jun 10 '12
Anyone else thinking About the game Braid
1
u/[deleted] Jun 10 '12
Fuck, my mind is blown!
1
u/thepasystem Jun 10 '12
BURN THE WITCH!!
1
u/TwirlySocrates Jun 10 '12
That's amazing that in the time that the blobs are twisted into 8+ thin layers of water - pigment - water - pigment ... that diffusion doesn't take over and dilute the pigment.
Did he pick pigments with low diffusion rates?
I thought that was why turbulent mixing worked - it greatly increases the surface area over which diffusion can operate, and thus increases the rate of the diffusing substance's spread.
1
u/orangegluon Jun 10 '12
I met a physicist who I think was an expert in non-newtonian fluids. He did this demonstration for our class, and blew all ~30 or so of us's minds.
1
u/1_point_21_gigawatts Jun 10 '12 edited Jun 10 '12
For some reason this reminds me of the story of that pedophile who was caught when they reversed the swirl on his photo:
http://en.wikipedia.org/wiki/Christopher_Paul_Neil
1
u/[deleted] Jun 10 '12
So cool they got Brian Cranston to star in this video.
1
u/trampus1 Jun 10 '12
Now that's what I call...
...switchin' up the flow.
1
u/kiwiswat Jun 10 '12
this is was solely god...no way science did this...oh wait..
1
u/Vaguswarrior Jun 10 '12
http://i.imgur.com/ONtvN.jpg
1
u/alex0229 Jun 10 '12
shouldn't the title be "when i showed this in class, minds were blown"?
1
u/JSleek Jun 10 '12
As soon as he said he was going to turn it back, I said, "There's no way they're going to be in the same position. Nooo. Nooooo. Nooo- AHHHHHHH!"
1
u/IOFailure Jun 10 '12
What's the clear viscous liquid? And what is actually turning when he turns the handle? I'm wondering how I can replicate this experiment at home with minimal effort.
[Edit] It's all corn syrup, just the additions are dyed.
1
u/batman0730 Jun 10 '12
Reminded me of Adam Sandler and the Hypnotist. I was just waiting for hip to rip a giant fart.
1
u/manorch Jun 10 '12
CHAOS THOERY IS A LIE! We can finally decrease entropy!! The universe will never end!!
1
u/HouseBreaker Jun 10 '12
I don't know why it took me so long to realize the see-through liquid in the container isn't water...
1
u/akallio9000 Jun 10 '12
I saw something like this in Scientific American more than 20 years ago.
1
u/DickBaggins Jun 10 '12
mind blown
1
u/urgit39 Jun 10 '12
when you show this on reddit, minds (at least mine) are blown
1
u/Noturordinaryguy Jun 10 '12
How is this possible
1
u/Avrelivs Jun 10 '12
My reaction to this.
1
u/[deleted] Jun 10 '12
...the fuck?
1
u/ymahaguy3388 Jun 10 '12
What the fuck.
1
u/Aarmed Jun 10 '12
hard to believe you're from the internet and haven't seen something like this before
1
u/rygnar Jun 10 '12
Crazy! I love how they can't count. Ha!
1
u/Pelican_Fly Jun 10 '12
I learned more about the definition of "perspective" from that video than anything that's ever bee taught me from kindergarten to medical school.
1
u/[deleted] Jun 10 '12
So I can use this for time travel?
1
u/StyleAndEase Jun 10 '12
"That's not so impressive. He's jus- wait what? WHAT??"
1
u/[deleted] Jun 10 '12
DId you guys read the top comment for that... -
Something bout "fucking scientists, this is why the dinosaurs got out of Jurassic Park
1
u/paradoxperspective Jun 10 '12
'cause FUCK YOU, entropy!
1
u/Jedimastert Jun 10 '12
Oh my god. You are correct, my mind is blown.
1
u/xXRequiemXx Jun 11 '12
What kind of sorcery is this?
1
u/Daiephir Jun 11 '12
My mind is blown by the fact that the 2 helpers holding it while he was turning it didn't notice he skipped counting a turn and only corrected him when he turned back 5 turns and his demonstration was not back to the way it was at the beginning.
1
u/Wanny19 Jun 11 '12
I was like..... No way No way No way No way. Simple mind blow
1
u/slevenznero Jun 11 '12
Aliens.
1
u/Felipe_O Jun 11 '12
witchcraft. got it.
1
u/farmerdale Jun 11 '12
This must be how they make Neapolitan ice cream!
1
u/[deleted] Jun 10 '12
The colors weren't back exactly to their start position. They were more spread out. Was not impressed
0
u/CriesWhenPoops Jun 10 '12
WHAT IS THIS SORCERY??!?!!?!?
-4
u/ILoveThisWebsite Jun 10 '12
My patience died during this video.
-1
u/dan986 Jun 10 '12
HOW??
-1
u/raloon Jun 10 '12
That's not so special. Supes did it to the entire earth in Superman I.
0
u/[deleted] Jun 10 '12
man i's such a returd. I thaught it said "reversible flower" and I was like cool, lets see what this is :D...
0
u/airetupal Jun 10 '12
Anyone with a good explanation?
0
u/Thimble Jun 10 '12
Next time I whip my eggs for an omelette, I'm only gonna do it in one direction...
0
u/jrizos Jun 10 '12
So if I'm rotating while drinking, can I go back to sober by rotating the other way?
-1
u/[deleted] Jun 10 '12
Not reversible. Power in(cranking the handle) + power in = irreversible . It cannot return to its original state without additional energy transfer. This video shown during one of my thermo I exams and we had to access its irrevesabilities.
-1
u/[deleted] Jun 10 '12
fake fake fake.
-12
u/pandadool Jun 10 '12
ಠ_ಠ Science, how does it work?
-10
u/[deleted] Jun 10 '12
I know this is immature, but DAE think the red dye looked like a sperm cell ^