# Ink in water cup

1. Mar 10, 2007

### Abofaisal2008

Hello

I want know if i put ink point in water cup .. How i can describe ink point

motion ?? :uhh:

2. Mar 10, 2007

### Mentz114

The ink will diffuse. Look up 'diffusion'.

3. Mar 10, 2007

### DaveC426913

Or 'fluid dynamics'.

4. Mar 10, 2007

### Abofaisal2008

yes, i think diffusion . but i mean ink motion in water as liquied with liquied.

i think itsnt linear motion and i think its kind of chaos phenomena. Is that

right?

5. Mar 10, 2007

### Mentz114

Particles diffuse in a liquid. But for a liquid mixing with a liquid it's fluid dynamics, as DaveC points out. Yes, it is rather chaotic. Fluid dynamics is difficult mathematically.

6. Mar 10, 2007

### Integral

Staff Emeritus
Fluid dynamics would only come into play if the fluid were moving. For a drop of ink in still water you should be able to apply the http://en.wikipedia.org/wiki/Diffusion_equation" [Broken]. The simplesest solution would be if the ink drop were introduced into the middle of the liquid, rather then on the surface.

In the simple case you would use a spherical polar coordinate system and assume uniformity in all directions to get a solution in terms of only r, the radial component.

Last edited by a moderator: May 2, 2017
7. Mar 10, 2007

### daniel_i_l

Of course, gravity complicates things... first try without gravity:)

8. Mar 12, 2007

### DaveC426913

Last edited by a moderator: May 2, 2017
9. Mar 12, 2007

### Integral

Staff Emeritus
As for what you quoted, what the heck does that mean?

10. Mar 13, 2007

### DaveC426913

I quoted the OP's words about what he is looking for - not words that somebody else fed him.

When asked to elaborate what he is looking for, the OP's own words are about fluids in motion, and chaos.

Really, read the thread from post #1. Note what the OP is saying as opposed to what others are thinking he's saying.

11. Mar 13, 2007

### vicgnesh

Yes, I am sure that the ink will diffuse it water.

12. Mar 13, 2007

### Integral

Staff Emeritus
I guess not Dave cus I quoted the same post you did. I read the same lines you did only I see nonsense, clearly the OP does not know what he wants. I gave him a direct answer to that post. your posts are off topic and close to earning you a warning.

looks to me like YOU FED him fluid dynamics in post #3.

"WATER CUP" from post #1 does not imply a dynamic situation.

I will delete all further posts until we hear from the OP.

Last edited: Mar 13, 2007
13. Mar 13, 2007

### Abofaisal2008

Is my problem not clear?

ok .. put ink in water glass and observe motion of ink its not linear motion and its like smoke motion

http://www.astrographics.com/GalleryPrints/Display/GP4293.jpg" [Broken]

* im sorry for my english lang

Last edited by a moderator: May 2, 2017
14. Mar 13, 2007

### Abofaisal2008

Thank you DaveC426913

15. Mar 13, 2007

### Integral

Staff Emeritus
That could well be difusion acting unter the infuluence of gravity. I am not sure how gravity will interact with the diffusion equation but if it shows up as a non linear term, then you would see chaotic behavior.

As for fluid dymanics, there certianlly is not evidence of bulk motion of the water, if there were you would not see the delicate tentrils, they would lost in the currents, as the ink would simply follow the streamlines of the fluid.

16. Mar 13, 2007

### ZapperZ

Staff Emeritus
I think next time someone gives me a hard time when I make a point for a question to be presented in a clear manner, I will point to this thread.

The way that I have understood this is the evolution of a drop of ink in still water. This is a diffusion phenomenon, not a "fluid dynamics" problem.

While this is not an easy phenomenon to describe, I believe that what can be answered on here has been provided already.

Zz.

Last edited by a moderator: May 2, 2017
17. Mar 15, 2007

### nithin

Hmm i think that if you are doing it simply then talking about Brownian motion , how the molecules vibrating in the water "hit" the ink molecules and how it transfers energy to the ink molecules and causes it to move (diffuse) would suffice

18. Mar 17, 2007

### Abofaisal2008

Can you explain Browhian motion ? i think it for Einstien .. Is that right?