Saturday, July 09, 2011

Tibetan singing bowls give up their chaotic secrets


The water-filled bowls, when rubbed with a leather-wrapped mallet, exhibit a lively dance of water droplets as they emit a haunting sound.
Now slow-motion video has unveiled just what occurs in the bowls; droplets can actually bounce on the water's surface.
report in the journal Nonlinearity mathematically analyses the effect and could shed light on other fluid processes, such as fuel injection.
At the heart of the phenomenon are what are known as Faraday waves, which arise when a fluid such as water vibrates, constrained by a closed boundary such as the edge of a singing bowl.
As the frequency of the rubbing reaches that at which the bowl naturally vibrates, the bowl's edge begins rhythmically to change shape, from one slightly oval shape into another.
The energy of this shape-shifting partly transfers to the water, in which a range of interesting patterns can arise as the intensity of the rubbing increases.
Slow-motion video of that transition now demonstrates how the irregular patterns of waves build up, the way that they crash into one another, and how that frees droplets that fly into the air..
But at a certain point the water becomes unstable - and a fizzing display of droplets and chaotic waves results.
A report by Jason Palmer in BBC. Here. and in Scientific American 


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