Having studied supercavitation in the past, with specific reference to torpedoes such as the Soviet VA-111 Shkval, I was intrigued to find this video clip about Emperor penguins in Antarctica who appear to use something similar to boost their underwater speed.
I find that amazing. So much for this particular modern technological advance . . . Mother Nature's been doing it for millennia! I wonder if that's where the Soviet scientists got the idea?
Peter
5 comments:
Might be air lubrication, releasing some of the air held in the coat of feathers, but I doubt if there is actual cavitation involved. True cavitation actually vaporizes the water, and the bubbles collapse immediately, rather than leaving a wake of aerated water as seen in the video.
Or it could be that the Penguin recently ate at Taco Bell.
World War 2.1 by John Birmingham talked of a British warship that forced air through pores in the hull to create a hull to air to water interface.
In the story this so reduced wetted area and thus wetted-area drag that the vessel was capable of amazingly high speeds.
Maybe penguins discovered this first?
On a large screen you can see that the penguins are exhaling as they surface. The Shkval torpedo also expells gas at it's nose to create the air barrier. That makes sense for the penguins, too, because the very first thing they're going to want to do when they hit the air is to take a deep breath. The apparent velocity increase might be a happy accidental synergy. Note that the bubbles swirl around the body and wings, so there appears to be multiple vortices, so their body shape may have evolved to enhance the effect? This would be interesting to run through a computer hydrodynamics simulation. Probably already has been since the US Navy studied penguins, discovering that emperor penguins can stay down as long as 15 minutes and go as deep as 800'. Their lungs collapse as they go down and reinflate as they surface. Now that's an interesting trick.
There's a trail of bubbles that follow them when they first dive in that must be coming from their feathers, but the last thing they want is for that air barrier from the water to be penetrated. I would think any air that could be squeezed out from the feathers would be long gone before they start to surface.
Larry's analysis is spot on. The body shape is designed to maintain laminar flow as long as possible, , and there are probably turbulators/vortex generators in the right spot to induce transition,similar to tuna and some sharks.
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