Biomimetics Makes Waves

[gf0012-aust]

foundthis on world affairs board. don't know if it's genuine.

No, it's not. The Skval doesn't look like that. The rear has a basic resemblance, but the rest is the artists imagination.

 

[ILIAD]

There a picture of a scale model at http://www.periscope.ucg.com/mdb-smpl/weapons/minetorp/torpedo/w0004768.shtml . I have seen picture of the nose in detail, but damned if I can remember where.
It is an ugly thing, that's for sure.

Did these tordpedoes induce an air pocket around them? That would eliminate the boundary layer between the skin and surrounding water. Did they actually release air from the nose, or did they heat and vaporize the water? They must have placed control surfaces aft of the cavitation zone, or they wouldn't steer very well.

Too much turbulence can cause cavitation, due to localized pressure decreases, but controlling the turbulence around a surface can be done without cavitation, and still get the benefit of reduced drag. Any object in motion in a fluid (gaseous or liquid) will have a boundary layer, where the molecules at the surface are not moving relative to the stream flow. The trick is to control that layer and keep it thin and close so laminar flow is not disrupted.

I don't know how fast sharks can swim, but some tuna can burst to 50mph. I wonder if they actually get a cavitation envelope at those speeds? It's certainly possible, you would have a tiny low pressure zone behind every scale.

Are there any pictures of the cavitating torpedoes available?

 

[Pendekar]

I don't know how fast sharks can swim, but some tuna can burst to 50mph. I wonder if they actually get a cavitation envelope at those speeds? It's certainly possible, you would have a tiny low pressure zone behind every scale.

Actually, fish body produce this slippery liquid that help them reduce drag underwater. everyone might wonder why is it the fish body is so slimy.

 

[highsea]

I think the slime on some fish is more protective, and to discourage parasites. Not all fish have slimy skin, sharks are very dry and rough. When we release fish, we have to be very careful not to wipe off the slime, the biologists warn us that the fish can get sick without it. I wouldn't be surprised if it was toxic. Fish without slime, like sharks, often have symbiotic relationships with other species to clean their skin. And less slimy fish like salmon and carp tend to get parasites like sea lice, or various diseases more easily.

It's interesting to watch fish closely, they definitely use their scales to change their surface characteristics when swimming. I have also seen small air bubbles under the trailing edge of the scales, but only on large scaled fish like salmon, carp, etc. It also seems like the larger the scales, the less slime in general. Slime being more common on small scaled fish like bottomfish (halibut, flounder, skates). Possibly because they are not as well armored against biting things. Tuna are small scaled, and very slimy, lol. They also have little pockets behind their fins, when they burst at high speeds, their fins tuck into these pockets to reduce drag.

Lol, now all we have to do is figure out how to apply this to our ships and subs.

 

[ILIAD]

Actually, fish body produce this slippery liquid that help them reduce drag underwater. everyone might wonder why is it the fish body is so slimy.

Not sure about caviatation for burst speed, but they do some miraculous things with modulating body stiffness to propel themselves quickly when required. Take a peek at http://ww2.lafayette.edu/~math/Rob/ONR_Long&Root_final_report.pdf .