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viscosity of fluidity?

 
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admiral



Joined: 17 Sep 2005
Posts: 546

PostPosted: Wed Jan 18, 2006 8:00 am    Post subject: viscosity of fluidity? Reply with quote

Let's talk about it, how comes the surface tension of water? Has it something to do with viscosity? What is it generally?

Mr. Green I just want to start a peaceful scientific discussion.
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Bob S.



Joined: 29 Apr 2004
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PostPosted: Wed Jan 18, 2006 10:05 am    Post subject: Re: viscosity of fluidity? Reply with quote

admiral wrote:
Let's talk about it, how comes the surface tension of water? Has it something to do with viscosity? What is it generally?

As I understand it, viscosity and surface tension are two different things. Viscosity has to do with the motion of a fluid's particles against each other. And that viscosity is in all three dimensions. But surface tension is acutally stronger since it takes a fluid particle's natural cohesive bonding and confines it to a two-dimensional surface. Or something like that. I'm not sure of the physics involved and how they are related, but both are quantifiable properties for engineering purposes.
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stellara



Joined: 02 Apr 2005
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PostPosted: Wed Jan 18, 2006 12:11 pm    Post subject: Reply with quote

hey Smile I don't quite understand what you want to discuss.. Just the characteristica of water? ..
What I find very fascinating is that you can't compress it! Like you can compress air and then the pressure increases. It's just impossible.. Shocked Laughing

yeah, Bob, what you say about viscosity sounds logically.
greets Very Happy
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admiral



Joined: 17 Sep 2005
Posts: 546

PostPosted: Thu Jan 19, 2006 8:34 am    Post subject: Reply with quote

I want to discuss the definition "viscosity".
My first idea about viscosity was the surface tension of e.g. water. However the higher the viscosity is, the slimier the fluidity will be, and I took two examples, petrolium and blood.
And however if you put a feather into a can of petrolium, it will sink faster than if you put it into a can of blood.

The surface tension describes the time delay until the feather falls into the fluidity, and the viscosity describes the sinking-velocity of the feather inside the water.

So, it must have to do anything with the surface tension? Or do you have a better explanation?
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Bob S.



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PostPosted: Thu Jan 19, 2006 3:31 pm    Post subject: Reply with quote

admiral wrote:
... I took two examples, petrolium and blood.
And however if you put a feather into a can of petrolium, it will sink faster than if you put it into a can of blood.

A can of blood? Gah! Where do you get such a thing! Shocked Nevermind. I don't want to know.
Basically, blood is salt water with extra stuff thrown in, and water has a very high surface tension relative to its viscosity because of hydrogen bonding which gasoline does not have (or not as much of).

See here for a good explanation of surface tension and viscosity.

Water is a strange substance. Even though its molecules are smaller than those of gasoline, water's viscosity is about twice as strong.
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admiral



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PostPosted: Fri Jan 20, 2006 6:13 am    Post subject: Reply with quote

3rd paragraph, ll.9
Quote:
the viscosity of whole blood (cells plus plasma) is about 3 times
that of water
from http://www.madsci.org/posts/archives/mar99/921961618.Me.r.html
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admiral



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PostPosted: Fri Jan 20, 2006 6:31 am    Post subject: Reply with quote

And you can try to put some of your blood onto the table, if you compare it with water puored onto the table, you will see that water spreads faster.
Do you think this is a good prove?
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Bob S.



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PostPosted: Mon Jan 23, 2006 12:35 pm    Post subject: Reply with quote

admiral wrote:
And you can try to put some of your blood onto the table

Gah! NO! Shocked Use your own blood!
Quote:
, if you compare it with water poured onto the table, you will see that water spreads faster.
Do you think this is a good prove?

It proves that blood is thicker than water (which we know from the idiom Wink ).
But really, how fast something spreads has as much if not more to do with the strength of the surface tension relative to the density of the liquid to hold back the liquid flow than with the viscosity of the fluid itself.
To measure just the viscosity, you need a way to eliminate the effects of surface tension. That should be covered somewhat in your engineering dynamics and fluid mechanics class.
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pugachevV



Joined: 16 Jan 2003
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PostPosted: Tue Jan 24, 2006 5:50 am    Post subject: Reply with quote

We can say that viscosity is the resistance a material has to change in form. This property can be thought of as an internal friction.
Have fun.
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admiral



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PostPosted: Tue Jan 24, 2006 6:55 am    Post subject: Reply with quote

ok, then surface tension has not very much to do with viscosity.
Laughing But then, how do you explain the difference between cementing motar and cementing water on a wall? Doesn't mortar have a higher viscosity rate? Isn't it's surface tension higher than water?

Mr. Green I just want to make this clear first, then I still have got a lot of questions...
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pugachevV



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PostPosted: Thu Jan 26, 2006 5:35 pm    Post subject: Reply with quote

Mortar is a powder that because of a hudraulic reaction becomes a solid.
I think its viscosity is not so important.
I think water has a viscosity of about 1 and may be the standard against which other fluids are measured.
I imagine if you want to do some research there's a lot of stuff available.
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