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Jellyfish Swimming Is Mixing the Oceans
eviltangerine writes "A new article from LiveScience suggests that marine creatures, such as the jellyfish, may contribute as much to ocean mixing as wind and tides. Wired is also covering the story and includes a video of the jellyfish in action. From the article, 'The mere act of swimming implies that some water travels with the swimmer,' said CalTech engineer Kakani Katija, co-author of the study in Nature Wednesday. 'Drift applies to all animals, to anything with a body.' No word yet on when the jellyfish blender is to debut."
At the very least, the organism contains water.
However, Sir Newton shouldn't have any problem with the statement. Obviously, some water must be pushed away from the swimmer, but so long as the total water pushed backward equals the sum of the mass of the swimmer plus the sum of the water carried with the swimmer.
Furthermore, once the Jellyfish is in motion, any water carried with it, like the Jellyfish, will want to continue in motion. The most low-energy state allows the water already in motion with the Jellyfish to continue moving, while water in front of the animal is pushed aside and around back.
Unless the swimmer is frictionless, their sides drag some water along with them. Yes, water must be displaced backwards, but it's not false that "some water travels with the swimmer".
10 PRINT CHR$(205.5+RND(1)); : GOTO 10
The topic of ocean mixing is a huge subject, and seems to implicate just about everything you can think of: the atmosphere, geologic activity, emergent effects from complex system dynamics, boundary layers, energy dissipation, fluid turbulence, climate change, dissolved minerals, the rotation of the earth, gravitational effects of the moon, etc., etc. It's not particularly surprising to me that the actions of marine life are a significant component as well, though it's interesting to see actual numbers claiming to demonstrate it.
10 PRINT CHR$(205.5+RND(1)); : GOTO 10
Then he must not understand fluid dynamics. When moving through a fluid, the fluid closest to the object moving moves very little or even not at all, implying that some gets dragged forward.
Of course, a bunch gets flung back as well, which is what I assume you meant.
"Temporary vortices aside, I think that Sir Isaac Newton might take issue with this statement."
Well yes if you put the vorticies (turbulance) to one side you have probaly eleminated the mode of travel for the water. Customary car analogy: If I take the wheels of my car it will no longer roll down hill.
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
I mean, I know headlines can't convey everything, but it seems a few leaps have been made...
Not a physicist but a physician. This makes sense - since it's roughly same way blood moves in blood vessels. Flow along the wall of the blood vessel is minimal. The greatest flow is in the center of the vessel, with diminishing flow the closer you get to the wall. That's why flow increases dramatically in larger blood vessels (it's a function of the fourth power of the radius - called the LaPoiseuille equation).
Again I'm no physicist, but I assume that if you have something pushing a fluid through a medium, you could define two boundaries that are not movable - the solid thing doing the pushing, and looking further and further out eventually you reach a "column" of water where the force does not get transmitted and is thus also static. Although it would be hard to get laminar flow in this scenario, it's not hard to imagine the greatest flow being generated where the greatest pressure change is - ie somewhere in the middle of the area described. The pressure change (and thus the flow) will be minimal where the static "walls" are, be they "real" (as in a solid fin, or an arm) or "not real" as in a non moving column of water.
Seven puppies were harmed during the making of this post.
Ships don't travel in convoys due to the motion of water particles.
Ships in convoys are too far apart to affect each other much, unlike a crowded sail ship race.
Ships travel in convoys due to the motion of torpedo particles.