We have water in our rotating tank! Now testing the lasers

Posted on by Mirjam Glessmer

Above you see the very first water coming into our tank. Only a couple of hours, and the tank was full! And in solid body rotation (since it has been spinning all the time while being filled) which means that we can start doing the real experiments very soon! 🙂

Most of the afternoon has been spent testing the lasers that will be used later to measure flow velocities inside the water around our topography. Laser testing isn’t something where we can help with, but that doesn’t keep us from having fun with safety goggles! Although it took us a little while to figure out that while the goggles made the laser invisible (or, hopefully, blocked it from coming anywhere near our eyes) we could see on the displays of our cameras whether the laser was on or off!

Below you see the laser going through the water and illuminating the topography in the lower right corner of the image.

What needed to be done then was to make sure that the laser sheet is actually at exactly the position we want it to be.

When you look in from the side through the water, you see the shape of our topography illuminated and the vertical laser sheet coming in from the right.

Same if you look in from the top: Do you recognise our little Antarctica? Below we see a vertical laser sheet.

What the “official” camera sees can be observed on a screen in our second-floor office:

And what we saw is that there are way too many bubbles on the topography still, that show up as bright spots (which distract from the particles that we specifically seed to visualize currents). So: Someone needed to go in and clean…

We could observe on the screen how the bubbles were swept away!

Next, it was time to set the exact positions we want the laser sheets at.

For the horizontal sheets, this is done by having someone stand in the tank and actually measure the height at which the laser hits a ruler for a given setting.

But now I am going to pick up Lucie, or new team member, at the tram stop and hope that we are ready to start the real experiments first thing tomorrow morning! 🙂

Why do we go to all the hassle of rotating our swimming pool?

Posted on by Mirjam Glessmer

We have started rotating and  filling water into our 13-meter-diameter rotating tank! So exciting! Pictures of that to come very soon.

But first things first: Why do we go to the trouble of rotating the swimming pool?

The Earth’s rotation is the reason why movement that should just go straight forward (as we learned in physics class) sometimes seems to be deflected to the side. For example, trade winds should be going directly towards the equator from both north and south, since they are driven by hot air rising at the equator, which they are replacing. Yet we see that they blow towards the west in addition to equatorward. And that is because the Earth is rotating: So even though the air itself is only moving towards the equator, when observed from the Earth, the winds seem to be deflected by what is called the Coriolis force.

The influence of the Coriolis force becomes visible when you look at weather systems, which also swirl, rather than air flowing straight to the center where it then raises. Or when you look at tidal waves that propagate along a coastline rather than just spreading out in all directions. Or when you look at ocean currents. But all of these effects are fairly large-scale and not so easy to observe directly by just looking up in the sky or out on the ocean for a short while.

There are however easy ways to experience the Coriolis force when you play on a merry-go-round or with a record player or with anything rotating, really. Those are obviously spinning much faster than the Earth, and that’s exactly the point: The faster rotation makes it easy for us to see that something is going on. And obviously, Nadine and I had to test just that on the best merry-go-round that I have ever seen:

And that is what we’ll use in our experiments, too: Since our topography is a lot smaller than the real world it is representing, we also have to turn the tank faster than the real world is turning in order to get comparable flow fields. How to exactly calculate how fast we need to turn we’ll talk about soon. Stay tuned! 🙂

Introducing: Mirjam Glessmer

Posted on by Mirjam Glessmer

And another post introducing another team member working on the TOBACO project! Introducing today: Mirjam Glessmer.

My name is Mirjam. I am a physical oceanographer myself and have done a postdoc in Bergen (which – small world! – Elin sent me the advertisement to after – even smaller world! – a proposal for a postdoc position with Anna unfortunately didn’t get funded!). But while I love physical oceanography, love going to sea, and love doing tank experiments, I realized that I am not so keen on doing the sitting-in-the-office-and-struggling-with-software part of the research myself (but if you are interested in my oceanographic street cred, check out my publications on Nordic Seas fresh water, double-diffusive mixing, and lots of other cool stuff here). However, I am passionate about learning about other people’s research, and about communicating ocean and climate topics to the public! So I am here to support the outreach side of things.

When I am not in Grenoble, I work at the Leibniz Institute for Science and Mathematics Education in Kiel, Germany, and investigate outreach in ocean and climate sciences. How can we do it best? What design criteria can we use? In fact, I might be doing some research on who is reading this blog and for what reasons! 😉

For more information about me, you can have a look at my website, or – if you are interested in “kitchen oceanography”, random observations of all things water or science teaching – check out my blog!

Calibrations and decisions

Posted on by Mirjam Glessmer

Remember this little office on top of the tank? Exciting stuff going on there: Testing of the cameras that were just being installed in the last post! (Of course it will get even more exciting once we start rotating! :-))

Of course we need to know which part of the tank the camera captures exactly, and what any given length on the pictures relates to in real life. That’s why we measured the topography in the last blog post.

Below, you see that office again and additionally get a glimpse one floor down into the tank, and people moving a large grid there:

This grid, with exactly known dimensions and positioned in different ways above our topography, lets us calculate the focal length of the camera, which will ultimately give us the possibility to calculate back from pictures taken from far above to actual lengths in the tank. This is necessary to calculate the currents inside of the tank.

Easy as this sounds, I can assure you that it is not. So many considerations need to go into this now, for example where do we want to put the origin of the coordinate system when we interpret the data? And how should the axes be oriented? We are in the Southern Hemisphere, so should we use this to determine the direction of the x-axis? Or should the direction of the jet that we will be introducing into the tank give us our x-axis orientation? The source (where we will have the inflow of the jet later) seems like an obvious origin of a coordinate system, but we will move it around on the topography, so it really is not.

Decisions made now will make it a lot more convenient (or inconvenient) to work with the data for years to come, so lots of different considerations going on right now…

And there are two cameras that need to play well together, or at least the data coming from them needs to be connected seamlessly to each other…

Rotating a whole swimming pool!

Posted on by Mirjam Glessmer

We have arrived at the Coriolis platform in Grenoble and it is seriously impressive. When you have heard us talk about a 13-meter-diameter swimming pool that is being rotated, you could not have possibly imagined this GIANT 13 METER DIAMETER SWIMMING POOL THAT WILL BE PUT INTO ROTATION! At least I know that even though I theoretically knew the dimensions, I had absolutely no idea of how massive the structure would actually be when you stand in front of it or even climb in.

Let me show you around a little.

This is what the whole thing looks like when seen from the outside. It’s very difficult to imagine the scale of it all, but you can see the dark floor at the bottom of the tank, then on the left, there is a second level, and a little further up a third one. Those are all normal floors — on the second level there even is a little office!

When we climb down as low as possible, we see how the whole tank rests on all kinds of very heavy duty structures. And it must be, considering that it is supporting not only a lot of moving water, but also an office! I can’t wait to see everything rotating! Here you can maybe gauge the scale a little from the stair cases and handrails?

Below, the green metal wall (inside of that black-and-yellow striped zone, which is what will be turning, and the black safety guard) is the outside of the actual tank, that will contain the water later.

This is the office space on the second floor I talked about: you can kinda imagine the size of the tank underneath from the curvature of this room. And this will be rotating with the tank!

And here you see Elin down in the tank. The clear structure to her feet is the topography of Antarctica that we will use in the first experiment (more on that later).

When you look up from the tank, you see a lot of scaffolding and two very nice technicians (can you spot both?) installing fancy camera equipment for us (more on what we are going to do with those in later posts).

So this is where we’ll be for the next couple of weeks!

The first thing we did today was to measure the topography so we have a reference for what is actually in the water later (rather than what we thought there should be). You see Elin (on the left) sitting on the bottom of the tank, and Nadine (on the right) climbing on the topography.

And now we are busy sorting out all the things like access to the servers so we can see the data we’ll be measuring, VPN connections so Matlab finds its licence back home, and all the other fun stuff. But we will obviously keep you informed of every exciting new development, the super awesome science, and we are hoping to start calibrating the cameras later today! 🙂