Dear Fellow Scholars, this is Two Minute Papers
with Dr. Károly Zsolnai-Fehér.
If we write the laws of fluid motion into
a computer program, we can create beautiful
water simulations like the one you see here.
However, with all the progress in computer
graphics research, we can not only simulate
the water volume itself, but there are also
efficient techniques to add foam, spray, and
bubbles to this simulation.
The even crazier thing is that this paper
from 8 years ago can do all three in one go,
and is remarkably simple for what it does.
Just look at this heavenly footage, all simulated
on a computer by using Blender, a piece of
free and open source software and the FLIP
Fluids plugin.
But all this has been possible for quite a
while now, so what happened in the 8 years
since this paper has been published?
How has this been improved?
Well, it’s good to have bubbles in our simulation,
however, in real life, bubbles have their
individual densities, and can coalesce at
a moment’s notice.
This technique is able to simulate these events,
and you will see that offers much, much more.
Now, let’s marvel at three different phenomena
in this simulation.
First, the bubbles here are less dense than
the water, and hence, start to rise, then,
look at the interaction with the air!
Now, after this, the bubbles that got denser
than the water start sinking again.
And all this can be done on your computer
today!
What a beautiful simulation!
And now, hold on to your papers, because this
method also adds simulating air pressure,
which opens up the possibility for an interaction
to happen at a distance.
Look.
First, we start pushing the piston here.
The layer of air starts to push the fluid,
which weighs on the next air pocket, which
gets compressed, and so on.
Such a beautiful phenomenon.
And let’s not miss the best part!
When we pull the piston back, the emerging
negative flux starts drawing the liquid back.
Look!
One more time.
Simulating all this efficiently is quite a
technical marvel.
When reading through the paper, I was very
surprised to see that it is able to incorporate
this air compression without simulating the
air gaps themselves.
A simulation without simulation, if you will.
Let’s simulate pouring water through the
neck of the water cooler with a standard,
already existing technique.
For some reason, it doesn’t look right,
does it?
So what’s missing here?
We see a vast downward flow of liquid, therefore,
there also has to be a vast upward flow of
air at the same time, but I don’t see any
of that here.
Let’s see how the new simulation method
handles this…we start the down flow, and
yes, huge air bubbles are coming up, creating
this beautiful glugging effect!
I think I now have a good guess as to what
scientists are discussing over the watercooler
in Professor Christopher Batty’s research
group.
So, how long do we have to wait to get these
results?
You see, the quality of the outputs is nearly
the same as the reference simulation, however,
it takes less than half the amount of time
to produce it!
Admittedly, these simulations still take a
few hours to compute, but it is absolutely
amazing that these beautiful, complex phenomena
can be simulated in a reasonable amount of
time, and you know the drill, two more papers
down the line, and it will be improved significantly.
But we don’t necessarily need a bubbly simulation
to enjoy the advantages of this method.
In this scene, you see a detailed splash,
where the one on the right here was simulated
with the new method, it also matches the reference
solution and it was more than 3 times faster.
If you have a look at the paper in the video
description, you will see how it simplifies
the simulation by finding a way to identify
regions of the simulation domain where not
a lot is happening and coarsen the simulation
there.
These are the green regions that you see here
and the paper refers to them as affine regions.
As you see, the progress in computer graphics
and fluid simulation research is absolutely
stunning, and these amazing papers just keep
coming out year after year.
What
a time
to be alive!
Thanks for watching and for your generous
support, and I'll see you next time!
