Category Archives: wave watching

October #wavewatching: reposting my Instagram posts

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My scicomm Instagram @fascinocean_kiel is back! As in it’s something that I am putting more thought into again. While it started off strong almost two years ago with daily posts written specifically for Instagram, I’ve been in a bit of a slump. For a while, I just posted pictures from current blog posts with a description like “read more about this on my blog”, but this didn’t feel satisfying. It also meant that I had a lot of #wavewatching posts on my blog, which I felt were taking over what I want the focus of this blog to be on. So the current compromise is that all the #wavewatching stuff happens over on Instagram (in German, but they have a really good translator at least to English), and only the most outstanding highlights will get their own post on here. But there will be a summary post of what went on on Instagram every month or so. Or at least that’s the plan for now!

I started out posting on Instagram again at the end of my month-long trip to Bergen, Oslo, and finally Gothenburg, when I got the exciting opportunity to “meet” Anna Wåhlin’s AUV, Ran, and take part in a short cruise on RV Skargerak to see her in action.

Btw, the reason I am posting more selfies now is that I’ve been thinking about the research around #ScientistsWhoSelfie that shows that showing selfies is beneficial for being perceived as warmer, more trustworthy and also as reducing gender-related stereotypes about who can be a scientist (at least if you are a woman posting selfies). And I think that it’s a very easy contribution to make if it helps achieve scientists in general being perceived as more trustworthy and also helping people to see that scientists are not always old, white men with beards and messy hair in lab coats. Sometimes it’s also me, sitting in the rain, grinning because I get to see a cool AUV up close! :-)

On that cruise, there was of course also CTD work going on.

And work doesn’t stop just because it gets dark…

Then this is the library in Gothenburg — a beautiful building that I passed several times on the way to the institute, and always admired.

And then I was on the ferry to go back home! In a cabin with sea view! That made me so happy. I was so tired after that exciting month, so sitting in my bed instead of standing on the cold, wet and windy deck felt like heaven :-)

And then we were home! Or at least almost. The Kiel lighthouse is situated offshore in Kiel bight, and it’s where the pilot station is (you see the pilot ship returning to the lighthouse in the picture below)

And this is the ferry arriving in Kiel port. I always love watching how these big ships are carefully maneuvered into port!

And this is another lighthouse on our way into Kiel port, and the ferry’s wake.

And then we had a little throwback, reminiscing of Pierre & my adventures on Straume Bru.

And then we are back to wave watching in Kiel! Reflections on the sea wall, and total reflection.

And what was going on here with all that foam? And is foam actually a passive tracer, or is the distribution also influenced by surface tension or other stuff?

Here is where the foam ends up in Kiel fjord. And what I find fascinating is how towards the upper edge of the picture, the ring waves of the water draining into Kiel fjord are really visible, whereas in the lower edge the picture seems dominated by wind waves. Even though both types of waves are probably fairly equally present in all parts of the picture, just the different angle makes one or the other appear more prominently.

It’s really fun to bring this collection of screenshots of my Instagram together. I’m a little impressed by how many wave pictures I post!

Here we are looking at a ship’s wake that is reaching the beach.

And I just love the sound of waves on a stony beach!

Not every day is wave watching day, sometimes we just have to be content with water.

And autumn leaves…

But then there is of course always the opportunity to make the waves you want to see (and be the change you want to see ;-)). Here we are looking at hydraulic jumps in the sink at work.

Although with these views it seems almost silly to go to a sink for wave watching opportunities…

But now a wave riddle. What’s happening between this pic…

…and this one? Any ideas, anyone?

And then there was the day where I went to play with four rotating tanks simultaneously in the morning, and then later to a conference on “Screening the Sea”, audiovisual media and the sea. That was one exhausting day!

The next day, walking down to Kiel fjord, I was in a bit of a gloomy mood and thought that there might not possibly anything going on that I hadn’t taken a million pictures of already. And luckily I was so wrong! My faith in daily wave watching was completely restored when I saw the sediment clouds and how they behaved in comparison to surface waves.

And then there was the day with very low water, where we could really nicely see how the shape of the ground influences the waves.

Shallow water waves always look a bit ridiculous, don’t they? Like sausages moving onto the beach.

And then I finally combined a lot of selfie movie clips about meeting Ran, the Autonomous Underwater Vehicle, into a 5-min-movie and advertised that on my Insta, too.

When I went to go vote, I happened to wave watch in a spot that I don’t usually go to. Also fun! And nice to see how this floating bridge is sheltering parts of the lake from the wind. Although some waves come through, as you see in the deformation of the reflections of the hand rails.

And then I went to Hanover to give a workshop at their university. But first, I had to go do a picknick with Frauke :-) And, of course, a wave riddle. Can you guess who or what made the waves in the picture below?

Frauke is the best. She brought soap bubbles to our picknick! And there is so much physics in soap bubbles. From the films that change color as the bubble ages, to the shapes they form, to how their size is related to how hard you blow when making them. So cool!

Also super interesting to watch how the soap is sliding down the soap bubble, leading to a discoloration starting at the top, sliding down, until it finally bursts when enough water has evaporated.

And now for some drop photography! Water is dripping down from somewhere fairly high up, so the crown of droplets that is thrown up into the air by the surface bouncing back after each drop is quite large! As I was watching, someone moved a window in the office building right there, so that the sun’s reflection lit up the point of impact perfectly.

Then a morning walk with my sister in Hamburg. There was some fog in the shadow-y bits of the river but it’s really hard to spot…

And then back home in Kiel! Perfect wave watching, right?

Later that same day my favourite spot at the Holtenau locks.

I just always love it there!

And then: A day full of jellyfish watching! They are SO beautiful! (For more jellyfish pics, see this blog post)

Jellyfish!

And one last selfie with jellyfish.

So this is where we are at with my Instagram @fascinocean_kiel now: 444 posts! And the last three all featuring jellyfish :-D

And I am thinking about switching it back to English again. So much for knowing my goals with this profile… :-D

#WaveWatching, beautiful jellyfish, miniature rip currents, double-diffusive mixing in a Latte

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So today I spent a perfect day at the beach in Schilksee, at the mouth of Kiel Bight.

Not a lot of wind (you see the gusts of wind further offshore) but perfect wave watching nevertheless. Look at this beautiful wake!

Here I wanted to take another picture of a wake, but the seagull had already taken off by the time I had my phone ready. Still beautiful though!

And in this picture I just love the geometry.

I have never seen as many jellyfish as today. They were everywhere! So I had to take a selfie.

They look so beautiful, and give such a nice depth to the picture below!

We were watching for quite some time.

And more selfies. But isn’t the jellyfish just amazing?

In the gif on top this post you see it swim, here you have to admire each picture individually :-)

I think they are sooo beautiful!

Coffee break: Double-diffusive layering in a Latte! Super clear layers, so I totally invaded someone else’s personal space AND took pictures of their drink. The things we do for scicomm ;-)

On the way back. It was only around 2:40 when the picture was taken (as you can confirm if you recognize the ferry in the picture), but the light already looks like it’s the evening. And another beautiful wake!

And then, more exciting stuff: Miniature rip currents!

When the water is pulling back, they really become quite strong and impressive and it’s easy to imagine that they get super dangerous really quickly when they are a little larger.

Now with the small waves, they just look beautiful.

And did I ever mention that I looooove waves just before they break?

Have a great evening, everybody!

Watch how sediment is transported with the flow while surface waves above move in the same direction but much faster

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When I was on my way down to Kiel fjord earlier this day I was in a bit of a weird mood. I was thinking about how the weather was grey and gloomy. And how that meant that there wouldn’t even be a nice sun raise to take pictures of. And how I might already have said everything there is to say about waves in that area of Kiel fjord.

But then, this happened.

Thanks to people working on the drainage system on the other side of the road, there was a lot of sediment dissolved in the water dripping into Kiel fjord! And watch how it spreads into half circles from where it enters the fjord. How pretty is that?

And then, even better, when you look at the surface waves, they propagate a lot faster than those clouds of sediment do. So this is a really nice example of how wave motion and transport of matter in the ocean are independent of each other (as a first order approximation at least).

We do see an influence of waves on the sediment rings further out as they get deformed by the wind waves on Kiel fjord.

Actually, looking at the whole thing from a bit further away and not from directly above, we see that the sediment forms a plume parallel to the coast rather than spreading out in half circles further. And this I do believe is due to wave action. But let’s focus on the area right around the outflow… ;-)

I found this pretty cool to watch and was very glad I stopped my run to take pictures and movies when I first saw it, because on my way back it was all gone already. Lesson learned: Always stop to observe the cool stuff instead of pushing through with the exercises you planned on doing ;-)

Lille Lungegårdsvannet

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The geometric shape of Lille Lungegårdsvannet makes for perfect wave watching conditions. Not only when wanting to look at waves from all sides, but also when you are just fascinated by reflections and geometric wave pattern.

And also by rainbows. Am I the only one who, when the sun is out and at a good angle, walks around Lille Lungegårdsvannet to see the rainbow that you know must be there?

Visiting a wave power plant on a no-waves day

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You might remember earlier posts on a wave power plant I love to visit in Øygården, where it almost always looks like in the movie below (That movie is part of this blog post, but I also have a blog post on the wave power plant where waves used to drive a turbine or the one where waves run up a funnel to fill a reservoir).

Anyway, when I went there a couple of days ago, things were different. And while I still love visiting ruins of industrial buildings, especially in great weather, the water was … flat.

As in “flat as a mirror”. Below, you see the pillars that a bridge used to rest upon when the power plant was still in operation. And I have never been able to get this close to the funnel, whenever I have been here before, there were waves splashing everywhere and I wouldn’t have dared to go anywhere near that area.

Below you see the funnel that waves usually run up in and splash spectacularly. On the day we were there, we could walk up all the way to the funnel and even look down into it. See how the floor isn’t even wet in some places close to the funnel? The largest waves we saw were the size of the one below, just barely making it up into the mirror-like pond you saw in the picture above.

But luckily there is interesting stuff to watch there even when there are no waves, for example this happy fishy which just looks so content enjoying the view from the top of the cliff.

Or corroded steel rope. Did you know there is just ordinary rope in the middle? I did not. And how interesting that that middle bit is all that is left of the steel rope in places!

And also I always enjoy seeing different wave fields on bodies of water that are located close to each other, like here where the upper reservoir is sheltered from the wind whereas the lower isn’t.

So a nice trip all in all, just not quite the wave watching I had been hoping for! But I will be back! :-)

Phase and group velocities in deep and shallow water

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When Tor came to visit me in GFI’s basement lab a couple of days ago, he told me about an experiment he had seen in Gothenburg in the seventies. So Elin and I obviously had to recreate it on the spot. Therefore today, we are comparing phase- and group velocities in deep and shallow water!

Waves are excited by means of an oscillating, hand-helt beer can, curtesy of the beer brewing club at GFI. The experiments are filmed and wave lengths and phase velocities are determined from the videos, which is a lot easier than measuring them directly while the experiment is being run.

Shallow water waves

For shallow water, we are using a water depth of 10 cm. Waves are very easy to see and phase velocities are equally easy to measure.

There is another experiment on (standing) shallow water waves being run at GFI the year before students attend GEOF213, which I described back in 2013.

Deep water waves

For deep water waves, we use a water depth of 42.5 cm (the exact number only matters when the tank filling is also used to fiddle with the dead water experiment, as I had been when the idea for this experiment came up).

Typical wave lengths that are easy to do are between 10 and 25 cm (wave lengths obviously have to be short enough that the water is still “deep”, i.e. H>>wave length) — Elin’s instruction to me for the kind of waves she wanted was “Allegro!” :-D Elin, you are really the coolest and most fun person to play with tanks with!

In deep water, we now have the added difficulty that the phase speed is twice as fast as the group speed. This makes observing the whole thing a lot more difficult. Also amplitudes are a lot smaller now, since the tank was so full and we wanted to keep the water inside…

Here is t0 — Elin has just dipped the beer can into the water for the first time

t1 — can you see the wave signal has propagated up to where the red arrow is pointing to?

t2 — the signal has reached my thumb at the left edge of the picture.

From timing this, we can calculate the group speed. We can also measure the wave length on the video and then calculate a theoretical phase speed from that. For the experiments Elin and I did, the results were pretty good, as in phase speed was usually about twice as fast as group speed. And I am curious to hear how well this works out when the students run the experiment!

The mystery of “51”, or: Tidal current at Straume Bru

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My friend Pierre, who I went to Saltstraumen with in 2012, wrote me a text about a year ago and asked me to remind him to tell me about 51 next time we met. We met and, as we do, geeked out about some hydrodynamics stuff. And he told me about 51. It turns out that on his way to work, Pierre crosses Straume Bru on the 51 almost daily, and watches the strong tidal currents and whirlpools that form there. But it wasn’t until a couple of days ago that we managed to take bus no 51 to this specific spot — Straume Bru — and geek out about it together!

I got there about an hour before Pierre did. Not because he was late, but because I was so excited to finally see that tidal current I had heard so much about! And also because I had looked at the tidal forecast and wanted to make sure I would see the strongest current and not miss it by an hour.

Turns out that when I arrived, the current was indeed quite strong. But look at the water level relative to the structures. Pretty much half time between high water and low water, even though the current is strong, there is still a lot of water left in the reservoir!

I love watching the waves radiating from the edge in that wall, and the wedge of eddies that is separating the fast flow from the boundary.

Also look at how the waves are being deformed by both the eddy and the current in the picture below! Especially in the top left corner, where the “wake” of the edge follows the meanders.

As had been forecasted, it started to rain while I was wave watching. With the surface a little rougher now, I noticed these two long streaks. Not sure what was going on there?

It didn’t look like oil or any surface film, but I can’t really think of anything else right now. I was briefly considering Langmuir circulation, but I don’t think the wind was steady enough and also I don’t know if that would combine well with a strong current. Any ideas, anyone?

In any case, the stripes weren’t visible any more when the rain stopped. But look at all these amazing waves!

And, now looking downstream, some more eddies and whirlpools!

Looking upstream towards the bridge, we see the glossy V that is formed upstream of where the wakes meet that are formed by the walls on either sides of the outlet.

And downstream again — how awesome and cute are those little eddies? And how amazing is it that they can persist over long distances while maintaining a dip in the surface that is probably as long as my thumb?

And not two seconds look the same!

Below is a closer look of the two wakes of the sides of the outlet coming together and overlapping.

And here is another picture of the wedge of eddies that forms, separating the strong current from the more stagnant, turbulent boundary layer. Look at how irregular the wedge is, formed of eddies of different sizes that are being advected downstream! And also look at the waves that are being pulled with the current, leading to stripes along the current!

Here is another look at the wedge and the stripes of the waves that are being deformed by the current.

And another one, because the scenery is actually really pretty, too! Which I hardly noticed until I had taken about 500 pictures of the water ;-)

More eddies in the wedge.

Interesting how one side of the outlet forms a wedge while the other “just” forms a wake, isn’t it? I think it’s because the the left one, the one with the wedge, restricts the current a lot more.

And here is a new perspective: Looking at the wedge of a second, parallel outlet. You see really well how the boundary layers from both sides come together!

Looking upstream, the standing waves in the foreground give you an idea of how strong the current is!

And another beautiful wedge!

And more turbulence looking downstream. Funny how parts of the surface look so glossy and smooth, isn’t it? I think those are the areas outside of the current that aren’t turbulent.

Now a final excursion to the other side of the bridge, to look at the wakes of the structures. Notice how much less water there is now!

And here is the upstream part of the V.

And the beginning of the wedge.

Walking a little around the corner, we see that the wake begins already upstream of the corner!

And a final look at the wake.

This is how happy wave watching makes me, even when it’s cooold and raining! At least occasionally, not the whole 1.5 hours I was there… The rain, I mean. Happy I was all the time :-)

Two days later, I actually took the bus across the bridge (after another adventure with Pierre, more on that soon!) and the current went the other way! As it should, but it’s always nice to confirm theory.

Anyone taking this bus regularly? You should start taking pictures for a time series! :-)

#wavewatching: Standing waves on coffee on a train!

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When I wrote the blog post on “wave watching in a bucket” a couple of days ago, it strongly reminded me of a movie I had filmed already back in March 2018. I was sitting on a train, still inside the train station, and noticed the pattern in my mug (also I just had gotten my awesome lighthouse thermos, hence the awkward angle of the camera).

The train is vibrating, and that vibration makes standing, concentric waves appear and disappear.

I noticed the same pattern on the lady-next-to-me’s coke zero on the bus yesterday, but felt weird leaning over and filming it. So I had to post the old movie instead. And also now I am wondering again what exactly determines the pattern in the standing waves that we get when vibrating buckets or cups with fluids in them…

Wave watching in a bucket

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On the GEOF105 student cruise that I was lucky enough to join like I did last year, I happened to observe what you see in the picture above: Standing waves in a bucket! And this isn’t a staged photo, this is me taking a picture of a student at work.

We are looking at the bucket the students use to take surface water samples which they measure on deck. The bucket happens to stand just above the engine room. Which leads to vibrations. Which, in turn, leads to waves. Many different kinds of waves! In addition to what you see above, we find, for example, plain circular waves. They might look like they do in the picture below:

And here is a short movie of the waves, first in real time, then in slow motion.

Sometimes the circular waves also have other wave lengths.

The next pattern that develops from a monopole (like the one you see above) is my favourite: A monopole with higher order stuff developing at the edge of the bucket.

Watch the movie below to see it in motion (first at real speed, then in slow motion).

The next step, then, is water that almost looks as if it was boiling. Like so:

Here is a movie of the bucket with the “boiling” wave pattern, again in real time first and then in slow motion.

The movie below shows a close-up of some of the waves in the “boiling” state, when there was enough energy in the system to throw drops up in the air. The movie goes from real time to slow motion. Careful when you play it, I left the sound in in order to show how the frequency of the waves is the same as the frequency of the engine. (And because of the annoying sound, it doesn’t start up automatically, so you have to click to play)

Here is a movie that shows the bucket in different positions, shot continuously to show how quickly the wave pattern develop and also how close together the different spots with the different pattern are located. Thanks for playing along, Kjersti!

So clearly the location has an influence on what wave pattern develops. But what are other important factors? We tested material, shape and size of the container.

A small plastic bucket which is almost cylindrical, for example. Guess what happens?

We can get the same wave pattern as in the large bucket! The movie below shows three different wave pattern. When the frequency suddenly changes that’s because the movie is in parts played in slow motion.

As to material: It seems to be important that it’s flexible. Iron cast pans don’t work (yes, there is water in it!), neither do metal lunch boxes…

And round shapes make nicer waves. But the rectangular vanes of the surface drifters (aka paint roller trays) also make pretty pattern! But now the waves are, unsurprisingly, only parallel to the edges of the tray.

Yep, this is the kind of stuff that makes me really happy! :-)

Kiel to Bergen, the mini series. Part 14, in which we are in the snowy part of Bergensbanen minutt for minutt

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And now we’ve reached the heights where there is fresh snow! And also where there are wild rivers. Don’t know which I find more exciting :-)

Ok, yeah, it’s definitely the rivers that I find more exciting. Also, isn’t it funny that at first glance, the river seems to be flowing left-to-right, because that’s the direction in which the waves break? It’s flowing right-to-left, though, and the waves are breaking in an upstream direction because the water is just flowing so fast, it’s ripping the carpet out from underneath their feet, so to speak.

And now we have arrived in winter wonder land :-)

…where there is some new ice on the more sheltered parts of the lakes, too!

And now we on our way back down on the west side of the mountains. Snow only on the higher peaks, not at ground level any more.

And now it’s properly overcast and occasionally also snowing!

But let’s end this part of the journey with this beautiful outflow of the lake, and the standing waves that look as if they were braided into each other. So pretty!