Laminar Flow DISAMBIGUATION
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Laminar Flow DISAMBIGUATION

August 28, 2019


[intro theme] Greetings, children, Captain Disillusion here. Let’s get right into it with a recent video that’s been all over my feed– [Going Up the Country song]
Oh, okay. Not that, sorry, heh. We’ve had a few, uh, out of context reposts of the last, uh– How about–nope. Nope. Uh, maybe something, uh, on Instagram? [Going Up the Country music]
No? No– Y’know what? Let’s just check the old inbox. [Going Up the Country repeats] Ow! Okay, there’s gotta be something I can talk about. C’mon. Ah! Perfect: a baby! The little baby from Tik Tok that draws really well. How bizarre? Let’s examine this. Okay, so the hand looks kinda weird, swiviling around in the sleeve, but maybe this child is not as young as she appears, y’know certain conditions can– then again there’s the part where she looks away from the paper while still drawing. And that’s a little bit of a– What’s this? Oh. Looks like you guys have already… brought up all these points, and educated each other about it everything there is to observe in this video. I guess I’m not bringing anything new to the table. Let’s pick something else. Uh. There’s– There’s this one: it shows a stream of water frozen in place. …until a hand touches it, revealing it’s actually flowing. According to the title, this is a phenomenon called ‘Laminar Flow.’ But–it looked so magical. I think that– Oh. Looks like there’s lots of input from you guys here as well. Some sophisticated explanations… (Sighs) I suppose I have no choice I’m going to have to dive in and analyze your analysis. To test the wisdom of crowds. There are other examples of this kind of video out there. And under each, usually at least one expert opinion setting the record straight, that this is NOT laminar flow, that that’s not how it works, that it’s fake. Indeed, if you look up scientific demonstrations of laminar flow, you find that it’s pretty involved. Viscus sugar syrup mixtures, dyes, devices pushing liquid through horizontal tubes at just the right pressure relative to the tube’s diameter, the Reynolds number. What am I, Smarter Every Day? All I know is, tutorials on how to construct an actual laminar flow nozzle don’t make it look easy. This ‘King of Random’ build seems like an all-day project, YouTuber ‘djdegraaf’ went through several iterations of their version before they got the device to work right, a nd Don Jupp appears to have been perfecting his nozzle for the better part of a year. In the end, they all achieve a stream that’s pretty smooth and stable, but the doubters in the comments have a point: laminar flow nozzles produce a perfect tube of water, like a liquid laser beam, but these viral examples are organic and complex. It doesn’t look like the same phenomenon. So how do the ‘experts’ say this kind gets faked? I’d really like to educate myself. [CD reading comment] The relationship of between the frame rate of the camera and the frequency that the water is moving at–
[Normal CD] What?? Oh, I think I know what they’re trying and failing to describe: I’ve seen this trick where a water nozzle is vibrated by an audio speaker and magically attracts huge views! Legendary tinkerer ‘brusspup’ did a couple of these experiments, and then Vlogger ‘Wolfie’ saw that and did it, too. But louder and ‘funnier.’ [Wolfie] Todays video might get a little bit drippy. So now that I’m shooting on 24 frames per second–If you don’t do that it’s not going to work. (*buzz*) I’m going to make this water spout moving in 3… 2… 1… Here. (*feedback sound*) Back to the drawing boards. [Captain] Now wait a second, they talk about frame rate, but these guys mention shutter… and these ones use the term, ‘sync.’ I’m getting confused again! If we’re gonna explain to the masses how something works, we should understand the details a little better, cuz, you know, imprecision can lead to all sorts of unexpected effects. Woaaaaahhh Aaaaaaahhhhh! (*thud*) Ugh. Uh. So, let’s brush up on the protocol: water, runs through a tube, that touches the membrane of a speaker, which plays a tone of a certain frequency, which vibrates the end of the tube, which fans the water out. But the whole thing is being filmed by a camera, which records pictures, or ‘frames,’ at a constant rate. When the frequency of the audio tone is the same as the camera’s frame rate, or if your speaker’s not banging enough, a multiple of the frame rate, the flow looks like a sine wave. [Wolfie] I’m going to make it freeze in 3.. 2.. 1.. Boom! It’s Frozen Fully frozen! You already know… [Captain] Well, no, Wolfie, the water doesn’t look frozen, does it? It’s just the wave in which it seems to flow isn’t moving. If the tone’s frequency is slightly higher than the frame rate, the wave appears to travel forward. If it’s slightly lower, the wave seems to move backward. Trippy. But I don’t think it’s right to call them ‘synchronized’ because the speaker and the camera aren’t being coordinated to stay in sync. No matter at what phase of the tube’s 48hz bounce you power up the camera, it’s 24 frames per second record rate will make the water wave appear stationary. The two aren’t synchronized, they just happen to be synchronous, thanks to the precision of digital devices. And although it helps make the effect clearer, shutter speed has nothing to do with this. That’s just the time sampling within each frame. See, 24 frames per second doesn’t mean a frame captures 1/24th of a second in time, the camera’s shutter is open for only a fraction of the frame’s time. And shutter speed is actually measured as either a fraction of a second of real time, in photography where there are no frame rates, and in broadcasting where there’s one standard frame rate, or as a relative shutter ‘angle’ in the motion picture industry, where frame rates often vary. But don’t ever worry about that. Just know that’s why people’s videos of the experiment have different degrees of motion blur from shot-to-shot. Their shutter is usually set to ‘automatic,’ and changes with lighting. Slower shutter speeds makes the wave fuzzier, but more contigious. Faster shutter speed makes it sharper, but can break the wave into descrete dropplets. Or, I guess, reveal the droplets as they really are. Fascinating, isn’t it? And I guess the most important thing to note about this is that it has absolutely nothing whatsoever to do with laminar flow! I mean–am I crazy? Are we looking at the same videos? Nothing about this looks smooth, or still, or laminar! So what are you on about, Rahuls, Oscars, and Perkins’ of the world?? You know, catching a glimpse of one interesting phenomenon and then casually drawing a tenuous mental link to another one you’ve heard of is not knowledge, or expertise, or a license to explain it to random people on the internet with the confidant arrogance of a young *me*. So the question remains: what exactly *is* laminar flow? The answer is this. AND this. Because, laminar flow is just a blanket term for fluid flowing in parallel layers. As long as it’s doing that, it could be any shape, moving at any speed. And for all you haters out there who don’t believe this is possible, why don’t you just try it yourself?! (*water flowing*) [zen music] No tricks, no effects. This beautiful thing is really happening. Look, if you want the perfectly shaped liquid tube, then the complicated laminar flow nozzle DIY project is for you. But, if all you’re after is the laminar part, and don’t care about the shape, then it’s easy. First, fill a standard party balloon with water. Then, to show yourself the power of Flex Tape™, cordon off a small area for the nozzle, so the whole balloon doesn’t explode. And finally, stab a hole in it. Seems the only ingredients needed for basic laminar flow are: 1) That the liquid isn’t propelled before reaching the nozzle, which could introduce turbulence, and 2) that the rim of the nozzle is very smooth. As with many things, latex takes care of both. And that’s why this video is real. And the expertly commenters were wrong. They were so preoccupied with wether they *could* explain it, they didn’t stop to think if they, like, need to even, like, do it at all! Let’s face it, if I wanted to created a water-based hoax, why would I do something as simple as making it stand still? I’d probably shoot for something a little more elaborate. Wait a minute… I learned my lesson. Better take thorough anti-freebooting precautions. [Rad dubstep music] [CD Theme] But now I’m afraid it’s time for me to go, kids. [Mechanical sounds] A cute couple in Kislovodsk are quarreling over the proper spelling of ‘Kabbalah.’ Remember, love with your heart, and use your head for everything else! Captain Disillusion! [Water splashing] [outro theme] Subtitles by SWinxyTheCat.

aliasing and comedy demonstration experiment explanation humor laminar flow Sci-Fi Sound speaker the this VFX water

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  8. Till now you made me understand the things in your videos, but this time didn't get much. Got that it's not a fake but how is it so still. Wouldnt there be at least some light changes as the water flows. I'm trying to say that at home I do get some perfect flow's as I adjust the water in the shower, but I can still recognize that the water is moving. Why does it look like a picture? I'm not skeptical or anything. Just want to understand it. Thank you!

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  27. If laminar flow is a "term for fluid flowing in parallels layers", why do you call laminar flow the one une the video? There is nothing parallel in it. Am i wrong ?

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  43. dude, this guy has not changed at all over the years. Put it in 144p for OG Captain Disillusion watching mode.

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  51. Actually, the shutter and flow rate are not synchronous, but isochronous, since they use different timing sources that happen to have the same frequency.

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  55. You are just amazing at editing and vfx cap. I am new to this but i loved this debunk. Please keep making more.

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  56. Possibility that put 2 speaker at 2 side then make some song and make a squashing the water shape

    Reply

  88. Forgive me, but I am still…confused. Somehow, before watching this video, I was totally convinced that the visually stationary stream of flowing water, no matter how janky looking, was indeed laminar flow, and that whole vibrating/framerate stuff I had never even heard of, but now after, I am suddenly confused and am questioning it all anyway.

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  97. In an attempt to replicate the Captain's experiment I accidentally found a much easier way to do it. Use a defective balloon! https://www.youtube.com/watch?v=I8Sno627PrE

    Reply

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