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Author Topic: surface tension and swimming  (Read 8695 times)

paul.fr

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surface tension and swimming
« on: 09/04/2007 09:35:49 »
In competitive swimming, first and second place are often separated by tens of seconds. if one of the swimmers covered themselves in soap would this release the surface tension behind them enough to propel them that bit faster and release the surface tension enough to make them go that 10th of a second faster?


 

Offline eric l

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surface tension and swimming
« Reply #1 on: 09/04/2007 10:19:49 »
It might also make it much harder to stay above surface !  Someone ready to give it a try ?
 

Offline lightarrow

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surface tension and swimming
« Reply #2 on: 09/04/2007 10:32:22 »
In competitive swimming, first and second place are often separated by tens of seconds. if one of the swimmers covered themselves in soap would this release the surface tension behind them enough to propel them that bit faster and release the surface tension enough to make them go that 10th of a second faster?

In case, I would use something which reduces water's viscosity, instead.
 

paul.fr

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surface tension and swimming
« Reply #3 on: 09/04/2007 10:43:46 »
It might also make it much harder to stay above surface !  Someone ready to give it a try ?

assuming then that you were a friendly bunch of swimmers, you would be better off soaping the other swimmers!
 

another_someone

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surface tension and swimming
« Reply #4 on: 09/04/2007 15:58:09 »
The problem is that you need to use the viscosity of the water to help propel you forward; thus, almost anything that generally reduces surface friction will will also reduce your propulsive efficiency.

Reducing the hydraulic drag over your head and torso is valuable, but for this, swimmers shave their heads, and might wear swimming caps and full body bathing costumes - they don't really need soap (which could also prove to be an irritant, if the water becomes too full of soap).
 

Offline eric l

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surface tension and swimming
« Reply #5 on: 10/04/2007 07:59:59 »
Would an increase in viscosity not result in less turbulence and hence less drag ?  It might well increase the propelling effect of the movements, too.
 

another_someone

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surface tension and swimming
« Reply #6 on: 10/04/2007 12:04:04 »
Would an increase in viscosity not result in less turbulence and hence less drag ?  It might well increase the propelling effect of the movements, too.

Increase viscosity too much, and you are swimming through treacle; reduce is too much as you are swimming through air (aside from the buoyancy issue).  Neither are ideal, so one has to assume there is some ideal between them.
 

Offline eric l

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surface tension and swimming
« Reply #7 on: 10/04/2007 12:38:59 »
How much would be to much ?  Are you thinking of a factor 2 (double or half the viscosity of water) or a factor 10 ?  From my own experience with viscoities (not in swimming water, mind) a factor 2 does not have much influence on things like turbulence and such things.
 

paul.fr

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surface tension and swimming
« Reply #8 on: 10/04/2007 13:27:07 »
http://www.nature.com/news/2004/040920/pf/040920-2_pf.html

Quote
Swimming in syrup is as easy as water
You can swim just as fast in a pool of gloop.
Michael Hopkin
 
Water: good for swimming in but no better than syrup.

Punchstock
 
It's a question that has taxed generations of the finest minds in physics: do humans swim slower in syrup than in water? And since you ask, the answer's no. Scientists have filled a swimming pool with a syrupy mixture and proved it.
« Last Edit: 10/04/2007 13:30:14 by paul.fr »
 

another_someone

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surface tension and swimming
« Reply #9 on: 10/04/2007 14:40:13 »
http://www.nature.com/news/2004/040920/pf/040920-2_pf.html
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creating a gloopy liquid twice as thick as water

That's not always the case. Below a certain threshold of speed and size, viscous drag becomes the dominant force, making gloopy fluids are more difficult to swim through. Had Cussler done his experiment on swimming bacteria instead of humans, he would have recorded much slower times in syrup than in water.

I would, in the circumstances, question whether there is not a level of viscosity where even for humans the effect is as for bacteria.

Yes, it is probably possible to transmit greater force to a more viscous liquid, but there is an ultimate limit to how much force a human being can generate no matter what the capability of the medium to absorb that force.

Maybe the swimmers can swim as fast in the thick goo they tried, but trying to swim through thick mud is a very different matter.  Maybe if we had enough muscle power, we could do it as efficiently, but in real life, it does not happen that way.
 

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surface tension and swimming
« Reply #9 on: 10/04/2007 14:40:13 »

 

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