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UC3M Scientific culture
Scientific explanation
of why the beer spills when colliding bottles.
How did you come up with the idea for this research?
It was out of mere scientific curiosity.
Some lab colleagues were meeting in a bar after work
and someone made the trick of tapping a beer bottle.
We saw the foam spilling
and ask ourselves what could be happening.
Each of us started to propose his own theories and explanations
but any of them could convince us enough.
We found that a thorough work was required
and suggested taking the idea into the lab
so that we can make controlled experiments
with well-defined conditions to see the physical problem inside
and the physical effects that control this foam appearance.
What does the experiment consist of?
We want to reproduce
the beer bottle tapping so that the foam spills.
To have measurable conditions we use a laser
that creates a bubble in a certain bottle area.
At that moment we tap the bottle
and that hit produces the foam spilling.
Then we film that phenomenon with a high-speed camera.
What is the science behind this experiment?
Initially we were interested
in the phenomenon that is called cavitation.
According to it, there is a process similar to boiling
in which bubbles are formed in a liquid
by increasing the temperature.
In cavitation we create those bubbles by decreasing the liquid’s pressure.
Then the foam generates the physical process series
that we are studying.
What are the outcomes?
We have found that this matter is pretty interesting.
It has three differentiated stages
with a well-defined length and different physics.
At the first stage, some expansion and compression waves
that move forward within the liquid
and produce the tearing of gas cavities, bubbles.
On a second stage,
these torn bubbles create tiny bubbles
that swell quickly.
On a third stage,
which is really the most explosive one
and the most efficient in terms of liquid foaming.
What happens is
that the foam scoop goes up really fast
because it is lighter than the liquid surrounding.
The more it goes up the more it grows.
In a certain way this last thing is like an explosion.
In fact, the shape of these foam clouds
reminds us of a mushroom cloud in a nuclear explosion.
What are the applications for this research?
One of the applications for this specific project
is being able to predict the amount of gases
that is released during a volcanic eruption,
the cavitation on boat propellers
or in Chemistry for applications
in which chemical reactions are boosted by bubble implosion.
Communication Vice-Chancellor
Institutional Communication Service
Scientific Information Office
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