Category Archives: wave watching

Wave watching on the ferry from Kiel to Oslo!

So I took the ferry from Kiel to Oslo and obviously had to document (most of) the water I saw :-)

Usually I’m quite fond of folding bridges and of ship watching. This folding bridge and tug, however, are between me and the ferry I want to catch…

Made it to the best place onboard (well, except on the bridge, possibly…). Phew!
Had a false positive test notification this morning (mind you, not a false positive test, but a poor overworked health person checking the wrong box and me thus getting the wrong text message) and even though that was sorted out within minutes, it was quite an exhausting experience! So now I really appreciate this nice spot on deck, my new rain jacket and my rain pants even more than if it had been uneventful and smooth until now… ;)

Great spot for wake watching, and the sun is even coming out intermittently!
Bye bye, Kiel, see you soon!

Awesome #WaveWatching going on!
Also: Not a lot of water here today!

See the turbulent track of another ship (blue), both sides of its V-Shaped wake (red & green) and where the wake breaks on a sand bank.

Might be difficult to see, but that’s the pilot boat just turning away from another ship. Yep, getting windy!

#wavewatching is definitely getting more interesting! And deck pretty much empty by now. Did not think I would be wearing my awesome gloves in August @kjersti.daae but am very glad I packed them on top of my luggage right with the wooly hat & rain pants

I’m not a #meteorologist but this looks … wet!

Look at how different the upwind and downwind sides of our wake look! Downwind there is consistent breaking of “the feathers of one side of the V”, upwind only some few break, but then they break somehow more spectacularly.

How the mood has changed! But note the difference between the upwind and downwind side of the wake!

Got some sun yesterday afternoon after all!

could stare into the turbulence of the ship’s propellers forever without getting bored!

Great belt bridge

Windy morning! Love this kind of #wavewatching (only slightly scared my phone will be blown out of my hands…)

That’s some nice waves! :)

Birthday weather (not mine :))
Always worth getting up for the sunrise…

How awesome are waves in the sun? Worth risking my phone for these kinds of pictures! (Yep, I should get some kind of case & strap…)

Sorry, couldn’t vacate my breakfast spot for a better angle, but look at that pretty wake! Those wavelets don’t cease to amaze me. Maybe I should get a seagoing job?

Wake watching in Oslofjord

One last Oslo fjord pic (beautiful wake!!) before we had to go back to our cabins for a very well-organized exit!

What I never noticed before today? That when the hatch to the car decks is opened, they split the bow — down to the bulbous bow — in half and move it away to the sides. Sadly I didn’t get a picture from the side where it’s nicely visible, didn’t have a free hand…

Still windy! See the gusts of wind move over the surface? (Well, I guess they don’t move in the picture, but you know what I mean…)

Fountain with a view

Now that’s my kind of water feature! Mesmerizing!

Don’t know why sculptures so often involve naked people, but this is one instance where I think it actually works

And now I’m exhausted. Let’s see how much water I’m going to see tomorrow! :)

“Evaluating shallow water waves by observing Mach cones on the beach” — guest post by Felipe Veloso on his recent #WaveWatching article!

Super excited to share a guest post today: Felipe is writing about his recent #WaveWatching article on “Evaluating shallow water waves by observing Mach cones on the beach”. I came across this article and was going to write a summary, but how much cooler is it to hear from Felipe himself? Thank you for being here! :)

My name is Dr Felipe Veloso1 and I tremendously appreciate Dr Mirjam Glessmer invitation to write this post and letting me contribute to the terrific #WaveWatching collection!!

One of the spectacular things of #WaveWatching is that the observations are ubiquitous. It doesn’t matter if you live in Germany, USA, Japan or Chile. Oscillations and waves are there, whether you observe swimming pools, lakes, sea, or even a relaxing bathtub ready for you. In all cases, the water is always naturally oscillating in a comfortable dance combining up-and-down and back-and-forth movements. If you enjoy these natural phenomena like I do, invest some of your time and take a look to the wonderful #WaveWatchingWednesday and #KitchenOceanography collections that Mirjam has gathered for us. But there are some occasions that these wave phenomena are obscured to our naked-eye observations and a more careful revision is needed to figure out where these oscillations are hidden. A turbulent river coming down of a hill, or the simple passing of fast water flow in front of our eyes are some examples of “waves hidden at first sight”. Such situation occurred to me in the latest family vacations we had as a break from the lockdowns imposed by the pandemia. In particular, this situation became the reason of an article in Physics Education, and also the reason  of why I am writing these lines.

In an attempt to run away from the contaminated air of Santiago (the Chilean capital city, surrounded by mountains), we drove ~90 minutes to Viña del Mar city, to enjoy one week in the beach side. In this place, with the appropriate weather and personal calmness, families can enjoy the waves crushing the beach, the rising of children as “sand engineers”, and the “continuous fight” between these children and the ocean waves to avoid the destruction of the sand fortresses by the water. It is in this relaxing and family-friendly environment where my story begins.

My kids are playing in the sand and my feet are partially covered by water. After long time, we are able to come out from our houses after several months of mandatory quarantines, pandemic stress, and online teaching activities. In this particular moment, watching waves looks like a perfect panorama for me. Suddenly, the voice of my daughter Pilar wakes me up and asked me two questions: “Dad, what are you looking in the water?… and dad, why does the water creates those conical shapes at the end of the undertow current?” The first answer was easy. I was #WaveWatching. But the second answer was not so simple. What about those conical shapes?

Mach cones observed in the surface of undertow water produced by stationary millimeter grains/seashells in sand. Those feet belong to my daughter Pilar and myself. Image taken from the article.

Before her question, I haven’t thought on that. Rapidly, I realized I was observing a wave phenomena in a different and non-standard way. We were observing shock waves in the shape of Mach cones!! These cones appear when an object moves inside of a fluid with a relative velocity larger than the natural oscillation velocity of the fluid. In these situations, there is a shock occurring in the fluid itself. The tip of the cone (or V-) shape arises from the relative movement of the object, whereas the radial expansion of the wave creates the sides of the cone. This explains the formation of V-shapes in the water when a ship travels in a river, or when ducks swim in the lake. In the case of beach observations, the cones were originated by stationary small seashells or larger grains buried in the sand when the undertow water current returned back to the sea with depth not sufficient to immerse my toes.

Now, I am not really sure if my 8 years-old daughter or my 11 years-old son understood completely my explanations of waves and Mach cones. But, I am sure they understood that observing nature can be a fun and relaxing activity to enjoy in family vacations. As an exercise, I taught them how to compute the wave velocity by measuring these Mach cones. I also show them that we did not need any fancy or expensive equipment to accurately evaluate it. We only require interest and fascination on looking for an explanation of a natural phenomena… a phenomena that they could observe while enjoying the beach, the sand and the family time.

Family picture in Viña del Mar. My beautiful wife Alicia, my kids Diego and Pilar and myself. And of course, our dear dog Chewbacca trying to run away from the camera.


Further details can be found in the paper: Felipe Veloso (2021) “Evaluating shallow water waves by observing Mach cones on the beach” Phys Education 56, 054001.

  1. @fvelosoe in Instagram and Twitter