All Questions
16 questions
1
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1
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121
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How to calculate the thickness of ice formed on a lake with a known temperature gradient?
I've been working on a problem involving the formation of ice on a small lake. The surface of the lake is in thermal equilibrium with the air at $-4^{\circ} \mathrm{C}$, while the bottom remains at $4^...
1
vote
1
answer
56
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A problem to understand the stability analysis in the Cahn-Hillard equation
Let us suppose the general diffusion equation (Cahn-Hillard equation):
$$\frac{\partial c}{\partial t} = M \nabla^2 \mu, \tag{1}$$
where $c (\underline{r},t)$ is the concentration of a given species ...
- 33
1
vote
2
answers
90
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A problem to find the the chemical potential from the free energy (Ginzburg-Landau/Cahn-Hillard)
I have a problem to derive exactly the spatial term of the chemical potential from the free energy of the Cahn-Hillard equation
So, let us start with the free energy of a binary mixture (A and B). The ...
- 33
0
votes
1
answer
166
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How does the pressure inside a pipe drop for a compressible gas (hydrogen)?
It is about turbulent compressible fluid, in this case, hydrogen gas.
I have hydrogen gas at Ti = 25 K, pi = 3 bars, and ṁi = 0.001 kg/s (so 2.214 m/s) at the inlet of the tube. The pipe is 12.7 mm in ...
5
votes
1
answer
222
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Why does a dump yard stink more in the night?
There was an open dump yard a few miles away from where I used to live for an internship. It was not noticeable during the daytime, but once the sun sets, the dump yard reminded us of its presence ...
- 12.6k
1
vote
1
answer
370
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Is natural gas transported as a liquid or supercritical fluid? [closed]
is natural gas transported as a liquid or supercritical fluid?
I am curious as to what phase natural gas is in when being transported in pipelines over long distances. Both liquid and supercritical ...
- 13
3
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0
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88
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Burning a match in a one-exit tunnel (or Heavy Rain trial of the butterfly scene)
If you light a match in a narrow labyrinth tunnel where there is only one way the air is coming from, will the flame of a match bend in that direction?
In other words, I want to know if the trick one ...
- 31
0
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1
answer
75
views
Can Brownian motion explain why white smoke moves around in the air?
Can Brownian motion explain why white smoke (fume) generated by chemical reactions moves around in the air?
0
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1
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97
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Fighting wild fires with sub zero air
I understand this is probably too costly to be practical, but was intrigued how one might use the mechanism of fire combustion against itself. Fires produce their own retardants (water and carbon ...
- 1
0
votes
2
answers
191
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Do different ways of vaporizing water have different efficiencies?
Question
Are some ways of vaporizing 1kg of pure water at ATP more efficient? Specifically cold vs hot methods of vaporizing water.
Background
There are many ways of vaporizing water. Some ways ...
- 676
2
votes
1
answer
700
views
Knudsen Number and pressure
When computing the Knudsen number to know if the continuum hypothesis can be applied as $\frac{k_B T}{p \sqrt{2} \pi d^2 L}$, do we use the static or total pressure of the free stream? My object is ...
3
votes
2
answers
733
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What's the minimum time scale for a candle to be lit in order for it to establish a steady state?
My Understanding
When a candle is lit initially, it goes through a few stages (see, e.g. this explanation from the National Candle Association):
Wick burns.
Crusted wax on wick melts, evaporates ...
- 280
1
vote
4
answers
3k
views
How does the dissolution of salt affect the solution density?
Suppose you have a container of water as a solvent and you a certain amount of salt as a solute sitting at the bottom of the container that has yet to start dissolving. Supposing temperature and ...
- 289
1
vote
0
answers
343
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How does fluid velocity affect the dissolution of some solute in the fluid?
Suppose we have a perfect sphere of some solute such as sugar and we place it in a fluid such as water, at a certain temperature, that is not moving. It will dissolve and diffuse into the water due to ...
- 289
6
votes
3
answers
11k
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How much heat from a fire actually warms your home?
A fire in a hearth disperses heat to, I guess, three places:
the bricks of the chimney
out the hearth (where the person tending the fire is standing)
out the chimney, above the house
How would you ...
- 587
0
votes
1
answer
116
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Phase transition of liquid under motion
I was testing in my lab with water and found that it starts to solidify when it is stationary at 0 degree centigrade. However, when I move the liquid with some velocity it doesn't change its phase. My ...
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