Thread: Cavitation

I would like to know why cavitation can sometimes cause a burst of light? I understand how cavitation works, but not how it could generate light. There's a shrimp or some kind of sea creature that breaks snail shells by snapping an arm at 8,000 Miles per second. At 10-20K frames per second you can see it really well and it's bizarre to me.

Sonic cavitation creates bubbles with no air in them that collapse. Often the force of the collapse is so great that the water at the very center is super heated to the point where it's so hot it glows for a split second. (That's where the light comes from, the glow of the super heated portion of the water.)

It's a really cool effect.

Originally Posted by kojax

Sonic cavitation creates bubbles with no air in them that collapse. Often the force of the collapse is so great that the water at the very center is super heated to the point where it's so hot it glows for a split second. (That's where the light comes from, the glow of the super heated portion of the water.)

It's a really cool effect.

Basically the bubbles are actually little vacuumes until the surrounding water implodes?

Originally Posted by kojax

Sonic cavitation creates bubbles with no air in them that collapse. Often the force of the collapse is so great that the water at the very center is super heated to the point where it's so hot it glows for a split second. (That's where the light comes from, the glow of the super heated portion of the water.)

It's a really cool effect.

Where did you ever get the idea that bubbles are formed with anything other than a gas in them ? What do you think a bubble is ?

The glow is due to adiabatic compression of the gas that is in the bubble.

http://www.faqs.org/abstracts/Zoolog...inescence.html

http://en.wikipedia.org/wiki/Sonoluminescence

Thanks for the link!

There's an old Harold Edgerton-type of high-speed photo (that I can't find on the Internet) showing a wadcutter bullet (shaped like a cylinder) striking a string and creating a line of light where it is hitting the string. This is likely the same phenomenon.

Originally Posted by DrRocket

Originally Posted by kojax

Sonic cavitation creates bubbles with no air in them that collapse. Often the force of the collapse is so great that the water at the very center is super heated to the point where it's so hot it glows for a split second. (That's where the light comes from, the glow of the super heated portion of the water.)

It's a really cool effect.

Where did you ever get the idea that bubbles are formed with anything other than a gas in them ? What do you think a bubble is ?

The glow is due to adiabatic compression of the gas that is in the bubble.

http://www.faqs.org/abstracts/Zoolog...inescence.html

http://en.wikipedia.org/wiki/Sonoluminescence

http://en.wikipedia.org/wiki/Bubble_fusion

It's one of the areas of fusion research, though it doesn't seem to be going anywhere, because the temperatures necessary for fusion to occur are only expected to be present in perfectly formed bubbles that collapse without deforming, and nobody knows of a good way to control it well enough to make that happen. --and it looks like maybe it doesn't even happen under those conditions.

http://www.scientificamerican.com/ar...reaction-findi

Anyway, that's where I got the idea about bubbles from. It's been a curiousity of mine ever since I spotted an article about it in Scientific American one day. Maybe bubbles aren't a technically correct way of describing what happens, but are used in the literature for simplicity?