Category Archives: observation

Wave watching on Kiel Canal: Bulbous bows and how they shape the wave field

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Even when I fully intend to just go for a Saturday afternoon walk to catch up with a friend, this is what happens…

I get distracted by waves. Like the crisscrossing pattern of waves and their reflections that you see below.

Or the amazing bow waves of ships passing by. Isn’t it fascinating what a huge amount of water is displaced by the ship’s bulbous bow, piling up into a mountain in front of it, then the sharp dip where the actual ship begins? (If you want to read about why ships are built with a bulbous bow, check out this old blogpost).

Having a bulbous bow alone does not always lead to the same bow wave. Which is fairly obvious when you think about it, of course the speed of the ship or the shape of the bow influence the wave field that is created, but also how heavily the ship is loaded, i.e. how deep the bow is in the water.

What you can see very nicely on the sequence of pictures of bows and bow waves in this post are bulbous bows going from fairly far out of the water (above) to fully submerged (towards the end).

And I just love the sharp contrast of the smooth water piling up and then the turbulence and breaking waves right there. Interesting example of subcritical and supercritical speeds, btw: The ship travels faster than the bow wave (so the bow wave can’t overtake the ship, but always stays behind it, forming a two-dimensional Mach cone).

The ship in the picture below is the odd one out in this blogpost: It does not have a bulbous bow but just pushes water in front of it. This is an interesting example of a bow shape that is clearly not optimized for energy efficiency when traveling large distances, but then the purpose of that ship is obviously a different one. But isn’t it amazing how such a small ship creates waves larger than all the other much bigger ships do, just because they have better bow shapes?

But beautiful wakes nonetheless. I love those tiny ripples riding on top of the wakes!

And, of course, the checkerboard pattern of a wave field and its reflection.

Here is another example of a ship with a bulbous bow, this time it is almost submerged. Since they are designed to be fully submerged, this ship is loaded in a way that is closer to what it was made for, and you see that the generated waves are smaller than the ones in the pictures up top.

And look at its wake — really not a lot going on here, especially when compared to the much smaller ship a couple of pictures higher up in this post!

Now for a ship that is hardly creating any waves at all, the mountain of water that it’s pushing in front of its bow looks especially weird since the bulbous bow isn’t visible any more.

See? (And isn’t it cool how the chronological order of pictures in this post just coincided with ships laying deeper and deeper in the water? I love it when stuff like that happens :-D)

And then, of course, I had to include some more pictures of beautiful wakes…

Do you see, comparing the picture above and below, how the first one was taken when the wake had just reached the shore, and the second one the wake was reflected on the shoreline already?

Not many things make me as happy as wave watching :-)

P.S.: Ok, one last bonus picture (non-chronological, we saw it some time during the walk. But that’s ok, I wasn’t going to include it until the post was already done and I decided that you just HAD to see this): Someone who is clearly not using their bulbous bow to their advantage. But at least I get to show you what they look like when they are not in the water. And we got to speculate about how annoying it is to be on a ship with such a strong tilt all day :-D

Minimal distractions from #wavewatching on a foggy Sunday morning in Kiel

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I’ve been wondering. Are foggy mornings where all you can see are waves (and a couple of seagulls) opportunities on which everybody else sees the world like I always see it (i.e. mainly focussed on waves), or do “normal people” just see the seagulls and, well, fog?

Below, for example, the first thing I notice are the wakes. And then possibly the birds creating them (since, of course, I am interested in what caused the waves) and the algae growing in the water (because I am looking down to see if there are more waves to see). But even looking at the picture now, I focus on the wakes and on how amazing it is that you see the middle one going all the way across the picture. And that the seagull in the front only started swimming at the middle of the image, since that’s where its wake starts.

I do like to have some birds or structures in my pictures for visual interest, but the reason I took the picture below was to show how foggy it actually was this morning. And how calm the Kiel fjord was with hardly any waves and therefore very nice reflections of even the flag pole. That is very unusual.

And then, in the image below, I finally spotted the Sweden ferry coming into Kiel port. I knew it had to be there because I had heard the engine for a couple of minutes already and it sounded very close, but it was nowhere to be seen. Can you spot the blue underwater hull and possible the blue writing saying Stena Line at the lower end of the upper third of the picture? But the reason I took that picture was mainly so that, when talking about the wake later (and of course I set out to take pictures of that wake specifically. Yep, that’s how I structure my Sunday mornings), I would have a reference for how foggy it was.

Because as much as I like watching ships, what I am even more interested in are their wakes. I really like how the otherwise calm surface clearly shows very detailed reflections that are only distorted by the wake. Look for example at the little life guard stand and its reflections — the poles holding up the roof are reflected on at least four different waves, repeating that very distinct part of the structure in different places depending on the surface slope of the wave. Or, to the left of the bottom reflection of that life guard stand, the reflection of the railing that seems to be mirrored. How awesome is that?

But then I also really like interferences of waves as shown below. Little seagull and its wake riding on the remaining wake of the Sweden ferry…

Or little random wave rings radiating out from a rock that is submerged and then resurfaces with each wave reaching it.

And what I find super fascinating in the picture below is how you see the longer waves in the undulations of the dark reflection of the structure of the jetty (careful though, it would never be a straight line since each individual pillar and the shoulder on top of which the actual gangway sits creates a little edge in the reflection), and then the short wavelength waves creating a noise on top.

And then, last but not least, the thing that I love to look at every single time: the waves and their reflections on the sea wall, creating a crisscross pattern.

Now imagine you had been on this walk with me. Would you have seen all the wave stuff, I saw?What are the kinds of things that you would have noticed that I clearly did not (since I did not mention them here)? 

I see a new hashtag in my future #oceanographyofpuddleswithreflectionsofElbphilharmonie

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There is a theme these days: one of Hamburg’s most famous sights, the concert hall called Elbphilharmonie.

And not only is it a pretty impressive buildings, it’s located right at the port of Hamburg, and, more importantly, right across from my new work place!

Yesterday morning there was a lot of ice on the puddle in front of it (above), this morning, by the time I got there, it was crushed (below).

And when I left tonight, there was some drizzle in the air and I did not feel like checking on the puddle.

Are you going to see this every day now? No, fear not — there are some cool blog posts in the pipeline! :-)

Here is to new beginnings!

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From dawn til dusk (which wasn’t actually as long a time as it sounds ;-)), first day in my new job as programme manager of the citizen science project on biodiversity “GEO-Tag der Natur“. I am looking forward to great views on the way to and from work! And I am suuuper excited to be starting this job! I will tell you more about it once I had the chance to settle in a little.

Even though wave watching is not part of the job, I could not help but notice those puddles. Not only because of the reflections of Elbphilharmonie on them, but because when I arrived there was a little ice on them (see above)! Which was gone when I left, but there were some tiny wind ripples (see below). Which one do you think is more beautiful? I can’t decide!

Where has all the water gone?

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You might have noticed that in today’s first post there was a lot less water in the Kiel fjord than in yesterday’s post (starting this year strong on the blogging front! I like it! And don’t worry, I won’t be keeping up this pace :-D). But look how little water there actually is!

In the picture above you see two navigation signs that are usually necessary there, because the rock in the middle is submerged far below the water surface. But not today!

And also in these locations you would typically see water coming all the way to the sea wall and sometimes even higher than that. So what happened? Strooong winds!

And the even more interesting thing will happen in a day or so, when the winds die down and all the water that got pushed out into the Baltic Sea comes rushing back into Kiel Fjord! Unfortunately I will most likely not be able to document it due to travel. Someone should pay me for documenting important oceanographic events in Kiel Fjord all day every day :-)

Ferry sailed past, wake perpendicular to wind. Cool interference pattern!

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Guess the title says it all today ;-)

Just kidding. Below you see a movie of a neat interference pattern I observed this morning. The situation is similar to yesterday in that the ferry has sailed past and the wake runs up on those bathing steps. But: today it’s quite windy and the wind waves’ crests are perpendicular to the crests of the ferry’s wake. Check it out:

That’s the kind of stuff I loooove watching! Happy New Year, everybody, may there be plenty of wave watching in 2019!

P.S.: Am I the only one who always wants to write fairy when writing about ferries? :-D

When the ferry has long sailed past and the waves start appearing out of the fog…

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Ending 2018 in style and exactly the way I want to continue in 2019: wave watching and dipping into Kiel fjord!

2018 has been an exciting year and a lot of changes that will shape 2019 to be very different from anything I have ever done before have already been set in motion. But despite all the new adventures, some things will stay the same: Stay tuned for ever more adventures in oceanography and teaching that I look forward to bringing to you!

Happy and healthy 2019!

Visiting the ruins of a wave power plant — waves running up a funnel to fill a reservoir

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Using wave energy to generate electricity sounds very attractive, after all there are tons of waves and all they do (in addition to looking pretty) is eroding coast lines. But that’s exactly the problem: There is a lot of energy in waves, so wave power plants have to be extremely tough.

Here is another post about the ruins of the wave power plant I visited on Toftøy. For an idea on the size of the waves on this not-very-windy day with fairly moderate waves, check out the movie at the end of this post (there are two people that you might be able to spot on the rocks on the other side, and those pillars used to carry a bridge). 

Below you see the waves entering a funnel that will lead them slightly uphill…

…so the water can fill up reservoir which is located higher than sea level…

…in order to drive turbines when the reservoir is emptied out again into the sea.

You already see the huge amount of energy stored in those waves, and looking at how little is left of the power plant, it’s definitely safer to stay well clear of those waves!

Check out in the movie below what it looks like when waves enter this power plant (and pay attention to the two people on the rock on the other side — they clearly didn’t expect that much energy in the waves! :-D)

Visiting the ruins of a wave power plant — waves driving a turbine

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After posting about how longer fetch leads to higher waves yesterday, here is why I was in that exact spot in the first place: To visit an old wave power plant on Toftøyna! The power plant was built in the 80s but destroyed only a couple of years after it had been built, so all there is to see now are some pretty exciting ruins!

Below, you see a cylinder that is a couple of meters high and some meters across, and that connects the air above the water with the water below. There used to be a turbine sitting at the top of that cylinder that used to be driven by the air column moved by waves at the base of the cylinder. The turbine is long gone, but what still happens is waves putting the water inside the cylinder into motion. And that looks pretty impressive as you see in the movie below!

Looking at those fountains shooting out of the cylinder, it’s not difficult to imagine what enormous kinds of forces the turbine had to endure before it got destroyed. Super impressive!

But what’s similarly impressive to me is how there are tiny flowers growing in this harsh environment. I guess it’s true: “life, eh, finds a way” :D