(jug gurgling) - This is a Gluggle Jug and
it's absolutely the best way to serve water to someone
because of the funny noise that it makes. (jug gurgling)
(water sloshing) It's good, isn't it. I really wanted to know
what was going on inside when it made that noise. It's obviously something to do with the fact that you've got
some air trapped in there and how the water interacts with that, but I wanted to know the details so I went online and I
was surprised to find there's not really anything out there, there aren't any diagrams, or animations, you can't even buy one of
these things made of glass so you can see what's going on inside. So I decided to do some
of my own investigation. My first thought was that
it's related to the fact that you can smash the
bottom of a glass bottle by striking the top. That subject was covered comprehensively in a Mark Rober video,
I'll leave a link to it in the description, but
the short explanation is that as the bottle moves downwards, the inertia of the water inside creates a cavitation bubble at the base, it's a near vacuum inside that bubble so the water rushes back in at high speed and as it strikes the
glass bottom, it smashes. Ultimately I think that line of reasoning is a bit of a distraction, but you know, I'd filmed it already, and it's cool, so it's in the video. Actually, the Gluggle
Jug reminds me more of that thing that happens sometimes when you're drinking water from a glass and the conditions are right so that when you tilt the
glass away from your mouth a jet of water sprays out
and hits you in the face. Does that ever happen to you? I mean, it's happened to me maybe three times in my life
ever, so it's very rare, but I do remember a sort of
glug sound that goes with it, or a gloip sound reminiscent of the sounds you get from the Gluggle Jug, gloip. So, maybe this jug is
able to create that effect in a very reproducible way, like maybe that's what's happening inside the tail every time it glugs. The drinking glass splashback-effect, seems to be easier to produce in a glass that has a wide top and a narrow bottom. Here, look, as the glass is tilted back, that large body of water is
channeled into a smaller area as the cross-sectional area of the flow of water goes down, the speed of flow must go up and the only place it has to escape is that small area left open at the top. Again, the narrower the
channel, the faster the flow, that's just from a conservation
of mass point of view. So you see a jet jumping out and under the right circumstances that can hit you in the face. It's somewhat related
to the Worthington jet, that's the jet of water you see, when you drop something into water, that topic was covered in
a, Smarter Everyday, video. I'll leave a link in the description, but in short the water
rushes into the space cleared by the pebble
and all that momentum is directed upwards into a
jet that touches your bum. This is all hand-waving
speculation, of course, what I really wanted to do was
see what was going on inside, I wanted to create a transparent version. My first thought was to cut
the thing in half like this, and then slap some Perspex on there so you can see what's happening. Annoyingly all these things are manufactured in an asymmetrical way, which makes that cut very difficult, actually cutting ceramic
is really difficult anyway. So instead this 2D version
is laser cut from acrylic. The drawing for the laser cutter was based on a tracing of a picture of the Gluggle Jug and an assumption about the thickness of the ceramic. I wanted to make sure I was getting the internal dimensions right, especially in this tail section, because goodness knows what's
happening to the thickness of the ceramic in that region. And given how hard it is to cut
one of these things in half, I just bought another one
and smashed it with a hammer so that I could inspect the inside. So this was the drawing
for the outer plate, and this was the drawing
for the separator. You may notice a problem, and thankfully, Lisa at Quirkshop
who did the laser cutting pointed it out to me. There's nowhere for the water to get in, so here's the updated drawing
and here's the final product, let's see what happens. (jug gurgling) Well, that's a lot simpler
than any of my theories, it's basically just bubbles
moving back and forth between the two chambers. Whenever you hear a gloip sound, it's a bubble moving back or forth. It's like the glug sound you get when you pour water from a bottle, but it's different in
a really crucial way. Look with the bottle air periodically rushes into the cavity and when it does it sets up vibrations in the air and we hear that as a sound, but compared to the Gluggle Jug, it's much quieter and
that's because the sound is coming from a closed cavity, it's somewhat insulated from our ears. The reason the Gluggle Jug glugs are so much louder when you
bring it up to vertical, compared to pouring water from a bottle, is the fact that the bubbles, that is to say the
Gluggle Jug glug bubbles, are escaping into an open cavity. The sound that is generated is able to escape through
that open hole at the top and therefore it's louder in our ears. That explains why the glugs are more muted when you're tipping the jug, it's because the bubbles
are traveling the other way into the closed cavity of the tail. It's my hypothesis that
the pitch of the glug is the resonating frequency of this pipe and that's something we can test because the wavelength of
the sound produced by a pipe that is open at one end
and closed at the other, when it resonates-
(pipe humming) Is four times the height of the pipe. That's because there's a node
here and an antinode here, so the full wave is like this. Well, the spectrometer here says that the frequency
of the sound is 480 hertz. We can get the wavelength by
dividing the speed of sound by the frequency. I'm gonna say that the speed of sound is 347 meters per second, that's because it's about 28
degrees centigrade in here. So 347 divided by 480 is 0.72 meters, divide that by four gives
us, well, 18 centimeters. And look, yeah, that's not bad. So there you go, the Gluggle Jug.
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