The bizarre patterns that emerge when you heat ANY fluid

(upbeat music) - When you Google the word convection, you get images like this, a 2D diagram of what happens in a saucepan

when

you put it on the stove, and it seems to fit the experience. Sometimes I lift the lid of a pan with spaghetti and the spaghetti comes together in a sort of donut shape, and I can imagine the strands twisting to form that shape, but is that really what's happening? Well, it turns out that the truth is much more interesting and I discovered it by building a real 2D version. You know, I like to build 2D versions of hydrodynamic mechanisms.

If you like that kind of thing, consider subscribing and clicking the notification bell. My first thought was that it should be made from a single piece of glass, but be resistant to thermal shock. So, borosilicate, but it's difficult to work with and would need to be made from sheets of glass, not blown glass, which can end up cloudy. You can see that here in the first version of my glass pop pop jar which had a flat boiler. So in the end we went with polycarbonate, which you don't want to get too hot, but it should be fine.

My first thought was that I should only

heat

it halfway. That way there will be a very clear path for the liquid to take its little cycle around the container. So just this little section here is aluminum, like if the whole bottom was aluminum and you

heat

ed it from the middle, eventually that heat would spread because aluminum is a good conductor of heat. I made the container quite tall because I wanted to see what kind of motion was obtained for different heights of liquid in the container. There is also the question of how do you visualize how water moves?

And I had some ideas for that. The first was to make the liquid rheoscopic, and that's what you're seeing here. That's really easy, just add mica powder to the water. The tiny mica flakes tend to align locally with each other, and as the water around them twists and changes direction, these aligned flakes reflect light in different ways depending on the orientation of the flakes. And this is how the flow becomes visible. I still haven't found an explanation for why the mica flakes locally align with each other, which is annoying, and here it is. It takes a little time to get started, but I love how it looks like smoke from a candle flame.

If I speed it up, the resemblance is even more striking. There are some interesting details here that aren't really conveyed in the traditional diagrams they show you in school. A fast, turbulent flow is obtained in a narrow channel in the center and a slow descent in wide channels on both sides. That could be due to the fact that I am heating it only from the middle. So here's a new container where the entire bottom is a strip of aluminum. The flow still seems really chaotic. Sometimes it seems like you can see different convection cycles, but then they break.

At one point the entire container is just one giant loop, but again, it doesn't last long. Fluid rheoscopic gives you an idea of ​​what parts of the liquid are moving, but it doesn't necessarily give you a great idea of ​​the speed of the liquid. It does to a point, but I wanted to see if I could do better. The first thing I thought was to use some type of neutrally buoyant particle. In other words, find some material that has the same density as water, which is one gram per cubic centimeter. That was the original definition of a gram, by the way, a cubic centimeter of water.

So many plastics have a density close to one gram per cubic centimeter, but no plastic reaches it. And then I thought, well, wait. I just need to find a plastic that has a density between the density of water and the density of water saturated with salt, which is about 1.2 grams per cubic centimeter. The ABS fits very well and, just by trial and error, I found the right amount of salt to make those ABS particles practically neutrally buoyant. The problem is that they stick together and that's annoying, and they seem to stick a little to the sides, so it doesn't help much to visualize the convection currents.

You can buy special particles that are a precise mixture of different plastics that give you 1.00 grams per cubic centimeter of density. The problem with them is that they are very expensive. Then I tried something else, water beads. Water beads are made of sodium polyacrylate, which has a density of about 1.2, which is not very good, except that they absorb hundreds of times their own weight in water; Once they are saturated in this way, their density is extremely close to one, and most importantly, they do not stick to each other or the sides of the container. The question then is: would the convection current created in this 2D convection current viewer be strong enough to lift the beads off the bottom?

And it turns out they are. That's pretty cute, isn't it? But I really wanted to see a good flow of particles. So you know what? I bought the expensive beads, right? I bought them. It's about a third the cost of gold per gram, which might be the most expensive substance I've ever purchased. Actually, maybe not. Actually, the nice thing about these beads is that they are fluorescent, so they really stand out if I shine this UV lamp on them. And I'm sure this is something you already know, but this convection flow that we're seeing here is driven by changes in buoyancy.

When bottom water warms, it becomes less dense, becomes more buoyant, and therefore rises to the surface. At the top,

when

it is further from the heat source and closer to the cold air, it cools down again. It condenses, loses buoyancy and sinks again. When it reaches the bottom, it reheats and the cycle continues. And since when it gets to the top, it has nowhere to go except left and right, you end up with these two cycles. Another way to see the convection current without using any tracers is to look at something like a heat haze. As water heats up, it becomes less dense, it bends light differently and that distorts this chess board I put behind it.

There is a convection phenomenon that I really wanted to try to reproduce. This occurs, for example, on the surface of the sun. You get these convection cells, so if you have a thin layer of convective

fluid

, it breaks down into these smaller units. I should be able to achieve this by simply making the water in my convection scope shallow and heating the entire bottom. I think it is possible to discern some different convection cells here, but they are not completely independent of the entire body of liquid, as if there seems to be a general movement outwards at the top and inwards at the bottom.

And when I do it again with rheoscopic

fluid

, it actually looks really chaotic. Even just in a petri dish, it doesn't seem to work either, but I knew it works with oil instead of water. So look, here's that mica in cooking oil, and look at those lovely convection cells. I'm just heating the base of the petri dish with hot water from the kettle. That's amazing, isn't it? There are convection currents there that rotate quite quickly. And then you have this slow motion as the cells change shape, fuse, and move. By the way, this is called Rayleigh-Bénard convection when you have these stable cells.

Apparently, given the right conditions, these convection cells will spontaneously form into an irregular hexagonal lattice. I thought the trick would be to make the oil layer very thin, but I can never get hexagons. So with oil, it seems like you can set up those multiple convection cells when you only have a shallow layer of convective fluid. So let's test the oil in the 2D container. And there you have it. It's great, isn't it? Look at those individual convective cells and there is hardly any turbulent flow. And for good measure, here is a container filled with oil heated evenly from the bottom, and you can see that the flow is much less turbulent.

This is because oil has a higher viscosity, which means for the same flow rate, less turbulence. And it seems that the convection cells are a little more stable with oil, although it is still quite chaotic. Of course, it is not only in the Sun where these convection cells are found. Now, an important part of the climate system here on Earth, are the Hadley cells that take warm air from the equator and deposit it further north and additional convection cells at higher latitudes. We normally think of convection as being driven by temperature differences, but it's not the only way.

If you take a dark-colored liquor like Tia María and carefully pour cream on top, you also get convection, but this is solitary convection. It is driven by changes in concentration. In this case, the Aunt Maria near the surface loses alcohol through evaporation, becomes denser, and then falls to the bottom to be replaced by the Aunt Maria below that has more alcohol. That alcohol evaporates and the cycle continues. Again, this is due to changes in buoyancy, but the buoyancy is changing for a different reason. It's not obvious why the cream is important, but it seems to be.

Convection can also be driven by changes in surface tension and the cream could be influencing the system that way, but I don't think anyone knows for sure. However, I will link to a helpful article I found. Something really strange happens when I search my comments for the word Henson. Basically, a lot of people insist on how good the Henson AL13 razor is. I mean, it's not that strange considering the fact that all those comments are on a video sponsored by Henson Shaving, but it's really unusual to get so many positive comments about a sponsor. And it actually made me realize that I made a mistake in the last reading on sponsorship.

As if I thought I was being very clever talking about the dubious business model of cartridge shaver brands. It's literally called the razors and knives model, and it's a massive false economy, but that's not what the commentators care about. They seem to really enjoy the experience of using the Henson AL13. So let's look at why that might be. Well, it basically comes down to two things: precision and blade support. The solid aluminum body provides incredible support to the blade, something not found in cartridge shavers, almost by design. But with all the support in the world, if the blade is in the wrong position, you won't be able to get a good shave.

Well, Henson is a family-run aerospace machine shop that focused on manufacturing its own products. Therefore, these razors are manufactured using CNC machines to aerospace standards. Once the blade is installed, it protrudes only 33 microns from the shaving plane. There's not much room for error there. I mean, it's good to know all this information, but at the end of the day, I just wouldn't shave with anything else now that I've tried the Henson AL13 and neither would any of these people in the comments section. . And just for comparison, I shaved this side of my face with the leading brand of cartridges and you can really see the difference.

And I'll just repeat this point, like you could buy a cheap razor handle and be stuck with cartridges for the rest of your life, or you could pay a reasonable price for this precision-engineered all-metal handle that will last a lifetime. and then get the blades for literally pennies. If you are interested in the promo for this one, it is really good. If you visit hensonshaving.com/stevemould and use promo code Steve Mold at checkout, you'll get one hundred free blades with your Henson AL13 razor. Just make sure both items are in the basket when you apply the code.

That's equivalent to three or four years of shaving. The link is also in the description, so check out Henson Shaving today. I hope you enjoyed this video. If you did, don't forget to subscribe and the algorithm thinks you'll enjoy this video below. (happy music) (happy music continues)