Tagged Questions
3
votes
1answer
70 views
Equidistant coffee rings in a mug: pinning boundaries coupled with migration of solute or just sip volume?
I understand that you get coffee rings on a table as a result of solute migration (solutocapillarity) towards the pinning of the circumference of the coffee ring [Deegan et al.].
Below is an ...
33
votes
7answers
2k views
How can two seas not mix?
How can two seas not mix? I think this is commonly known and the explanation everyone gives is "because they have different densities".
What I get is that they eventually will mix, but this process ...
1
vote
0answers
104 views
Mechanical effects of convective flow in steady-state stagnant film diffusion
When analysing diffusion problems in the context of the simplified film model, two limiting cases are ussually introduced during the solution of the differential chemical species mass balance ...
3
votes
3answers
1k views
What is the physical meaning of diffusion coefficient?
In Fick's first law, the diffusion coefficient is velocity, but I do not understand the two-dimensional concept of this velocity. Imagine that solutes are diffusing from one side of a tube to another ...
2
votes
1answer
148 views
What is the return probability for Brownian motion in three dimensions?
I would like to know the probability of return to the initial point in three dimensional Brownian motion. Does someone know an expression for the diffusion constant? (Suggestions of books on this ...
4
votes
2answers
2k views
Convective and Diffusive terms in Navier Stokes Equations
My question has 2 parts:
I just followed the derivation of Navier Stokes (for Control Volume CFD analysis) and was able to understand most parts. However, the book I use (by Versteeg) does not ...
1
vote
1answer
524 views
How does smoke move in the air and how can I direct it so it will go to a place I want it to go?
Let's assume a close room with 1-2 people who only one of them smoking cigarette.
What is the equation describe the smoking spreading? is it diffusion? what are the parameters is so?
Is there a ...
2
votes
1answer
214 views
Rough diffusion rate of sugar water through a larger volume of water
I hope this a question that can be answered and isn't too vague. I'm also only after a very rough answer.
I'm adding a small amount (~500mL) of sugar solution into a carboy with a much larger volume ...
6
votes
2answers
280 views
Why is the answer to this diffusion example unintuitive?
Imagine a linear decrease in concentration from left to right. Using Fick's first law,
$J = -D \frac{d \psi}{d x}$
for all x, from left to right, we have the same flux amount because the decrease is ...
