Tag Archives: GEOMAR

Collaborative Taylor column experiments during lockdown

We’ve become quite experienced with remotely-controlled rotating tank experiments, but the current lockdown brought us into yet another new-to-us situation: We had plans to film and live-stream tank experiments from Geomar, but not being employed there, I am currently not allowed in the building! So what happened this morning is that Torge and I met up on Zoom and I watched from home as he had all the fun.

It all started out quite well — camera tests worked well, water was in the tank, I was having fun taking screenshots. Well, and I was wishing I was there, playing, rather than watching and occassionally interrupting with instructions or unsolicited advice!

When we were done setting things up, students joined in for their exercise session (no, it’s not me three times in the meeting below, I just edited that in for privacy because we didn’t ask students for permissions to use their pictures), and a lively discussion ensued. Topic of the day were eddies in the ocean, and it was all leading up to the Taylor column experiment that we had only recently figured out.

The Taylor column experiment basically shows that rotating flows cannot just flow across an obstacle, they have to stay 2D and thus move around it. Which worked out beautifully! The blue dye started out upstream of the obstacle and got deformed into these beautiful filaments as it is moving around the hockey puck and the Taylor column on top of it (The puck is only blocking the lower part of the water column, above it there is just water!).

It all went super well until we fell into the trap we’ve been falling in ever since we started working with the tank: The co-rotating camera switches off when the power to the rotating table is switched off, which is the easiest way for the rotation to be switched off. So yeah. Below you see Torge trying to save the day by holding his laptop above the tank to give students a look into the tank after it stopped. Oh well…

But all in all, it worked super well and it’s great to see how virtual teaching and learning can be a really good substitute for in-person classes. But we are still looking forward to the times when we can all play together again!

Walk to & visit at GEOMAR as wave watching occasion

These very long and regular wave crests were caused by a ship — they are one side of the V of a ship’s wake that’s about to reach the sea wall here.

I love how well defined the wave crests are — on one side you see the reflection of the bollards and the bright sky, on the other side the reflection of the dark sea wall.

Below you can see the waves approaching the sea wall and then their reflection:

And I realized that it’s a very good thing I didn’t own a smartphone when I was still working at GEOMAR, otherwise you’d be completely fed up by these kinds of pictures by now :-)

For the rest of this post: More pictures of more wakes as seen from the roof top terrace, which very nicely show you the V-shape…

I just love how you see the “feathers” that, together, make up the V-shaped wake.

And several wakes on top of each other…

And below you see the turbulent wake in the middle of the V as a lighter line where the surface appears smooth due to turbulence.

 

 

You are watching seals? I am watching waves!

On a recent evening stroll with a friend, the seal basin looked like this:

“Do you think there are any seals in there today?” she asked. “Why yes, of course, don’t you see the waves?” I replied. Because obviously in a basin sheltered by the wind and with no moving parts in it except possibly a seal or three, there is no other mechanism that I could imagine that would create such a wave field. Sometimes I wonder what everybody else is thinking about all the time that I am thinking about waves while they aren’t… Who’s missing out on the cooler thoughts, me or them?

Anyway, we got to do some proper seal watching and wave watching, respectively:

Pretty, isn’t it? the wake of a seal. Pay close attention, I might be testing you on this some time soon ;-)