Tag Archives: Stena Germanica

More wave watching, this time in Kiel

Beautiful morning arriving back in Kiel… Looking downwind, the weather might seem pleasant (especially when focussing on the sunrise).

But looking upwind however, the wind rows on the water as well as the white caps on the waves indicate that it’s quite windy!

Very cool: the turbulent wake of a ship interrupts the wave field and therefore, with its different surface roughness, is clearly visible!

And below you see so many things: The sand bank running from the lighthouse towards the next headland becomes visible as waves are breaking  on it. The turbulent wake of that blue ship we saw above already is still clearly visible, as is its V-shaped wake. And you see our own wake as the feathery pattern that runs all the way from the bottom edge of the picture to way behind the blue ship!

And here our own wake becomes even more prominent as we turn. Laboe in the background…

Here is another ship, waiting to enter the locks of the Kiel canal. It’s moving only very slowly (so hardly any wake visible), but you see how it’s sheltering the water from the wind so the downwind water appears completely smooth right at the ship!

And here are some more wakes and sheltered spots of water surfaces. Locks of the Kiel canal in the background!

And another look at the locks. Do you notice how the wind rows still indicate that it’s quite windy, but how it’s a lot less windy than it was further out?

And then we are in the Kiel fjord. This is the upwind shore — see how waves are only slowly forming and building up with longer and longer fetch?

And then in the sheltered port a different kind of waves: Our bow propellers mixing the inner Kiel fjord!

Sunset wave watching in Gothenburg. Wakes under different light conditions!

Wave watching from high up gives you a whole new perspective on wakes, and depending on the lighting, features in the wave field become more prominent or fade away.

See for example below the ferry: You very prominently see the turbulent wake right behind the ship, and you see the waves of the wake opening up in a V-shape.

Above, there is still a lot of ambient light from the sky. Below though, the same ferry, similar spot, 30 minutes later: The turbulence is a lot harder to see since colors fade away, but the V-shaped wake becomes really clear since one slope of the waves reflects the city’s lights while the other reflects the darkness.

Another ferry coming in, another wake… Below the surface roughness becomes clearly visible with the turbulent wake right behind the ferry and the bow waves fanning out.

That was one brilliant mini cruise! Thanks for joining me, Frauke, and for staying out on deck with me — despite the freezing temperatures — until we were far out of the port and the light was gone completely. The sacrifices we bring in order to wave watch… ;-)

Refraction of light in ship exhausts

Leaving the port of Gothenburg after our mini cruise, A and I obviously had to secure the prime spot for wake watching because I wanted to check out more of the weirdness I talked about in the last blog post. So while we were waiting for the ship to sail, we had the best view of the ship exhausts, too, and it looks really fascinating:

img_9654

Do you see how the hot exhausts have a very different refraction index than the cold air around it?

Stena Germanica is the first ferry that size running on methanol (super interesting, btw, how the company is exploring new technologies!) so the exhausts are mostly clear.

img_9659

Although on occasion it does still look a little more like what you’d probably expect of a ship’s engine:

img_9660

But nowhere near as bad as it used to be! Can you imagine that this is what all ships looked like not so long ago?

img_9444

Good thing there are tons of regulations in place nowadays, and companies like Stena testing out new technologies.

img_9441

Can you imagine what Kiel would look like if there was more than one ship making that kind of smoke?

img_9460

Wake of the Stena Germanica — what’s going on there?

After having talked about wakes quite a bit recently, I’m going to show you a couple more pics today (bit not as many as I did two days ago, sorry! ;-))

And today we are focussing on the wake of one specific ship, the Stena Germanica that we sailed on for a mini cruise to Gothenburg (highly recommended!!). And even though that cruise sadly ended a month ago, I am still puzzled by what we saw:

img_9472

Look at the turbulent wake directly behind the ship. Do you see how the two sides are markedly different from each other?

img_9475

One side seems to be a lot more turbulent than the other.

img_9480

And I didn’t find an explanation for that. According to the internet, the ship has two propellers and on each of those propellers the pitch of the blades can be changed so that the propeller can always run at a constant speed and the ship’s velocity is changed by changing the propeller blades’ angles.

img_9482

Maybe that’s what is going on? But would they run two propellers at different pitches even when just steaming straight ahead?

img_9485

Btw, look at that beautiful wake pattern! You can see both the feathery V going out from the ship and those half circles filling in the V. I don’t think I have ever seen that this clearly on a ship this size before. But then maybe I just wasn’t observing well enough.

img_9487

I love it!

img_9488

img_9489

img_9498

img_9499

Now. The next morning: It is quite windy now, and the difference between the two sides of the wake is quite pronounced. Also very interesting: The foam on both sides is behaving very differently! One side (the upwind side) has a much sharper edge than the other.

img_9500

But this surely can’t be the effect of just the wind?!

img_9520

Looks great though!

img_9527

img_9528

img_9531

img_9565

Also very interesting: When arriving in Gothenburg, we met another Stena Ferry, and the same thing could be seen. Here she is after she passed by:

img_9584

img_9592

And her wake stays visible for quite a while with this marked foam stripe right in the middle of the wake, as if she had counter-rotating propellers that set up a convergence zone there?

img_9587

Same phenomenon again when leaving Gothenburg later that day:

img_9704

img_9703

And arriving in Kiel the next morning, we could beautifully observe the different parts of the wake again:

img_9789

img_9785

What do you think is going on here? Why is the wake of the Stena Germanica not symmetric? I’m having sleepless nights over this :-)