Thank you for coming and for participating.

So my name is Christoph.

As Uli already mentioned, I'm a PhD student.

I'm currently in the process of finishing my PhD.

The main work that I was focusing on during my PhD was the free surface lattice Boltzmann

method, the one that I will be talking a little bit in more detail here today.

However, this was, of course, a joint project with many collaborators.

So actually some of them are from our group, but then others who bring the external knowledge

are from the TU Braunschweig, and they are the experts on sediment transport and new

information.

But let me quickly start with what I will be going to talk about to you today.

So what you see here is actually some video taken from the beach.

So Christoph?

Yeah.

I think you shared the wrong screen somehow.

Did I?

OK.

The question is now I can share the whole screen.

Harald, then please give us feedback if this is then working.

Do you see something, Harald?

No, I saw something.

Yeah, that's perfect.

OK.

Thank you for informing us.

All right.

So what you can see here is some video taken at the beach where you have some water flowing

along the sand.

And what you see is that there are some kind of sediment form structures that you clearly

notice.

They are called dunes.

And this is something that you probably also know from the desert.

So in fact, they are also happening underwater and, for instance, in a riverbed.

And I want to clarify some terms first.

So the first thing is the bed form.

And a bed form is just a periodic structure that develops between the interface of a free

surface and a granular bed in motion.

Then we have dunes.

And the specialty about the dunes is then that these dunes are just sinusoidal-shaped

bed forms, a special type of bed form.

And eventually, they are the so-called anti-dunes.

And they are happening whenever you have the liquid surface in phase with the dunes of

the sediment bed.

So that's what I've marked in the middle.

And that's what's also shown at the bottom.

And very interestingly about the picture in the middle is that these dunes can actually

move in the opposite flow direction.

And the reason is quite simple, because as you can see here, so we have a flow to the

right.

But then the material from the sediment is transported to the left of the next dune.

And that makes it seem like the dune is actually traveling in opposite flow direction.