The quantitative study of how fluids (gases and liquids) move.
3
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1answer
439 views
Boundary conditions for Couette flow
I'm trying to reproduce a result from a paper (T. Thatcher, Boundary Conditions for Grad's 13 moment equations, equation (32), page 6), however, I haven't been able to do so. Hopefully someone can ...
9
votes
2answers
2k views
Are there any liquids with zero surface tension?
Having read the Wikipedia page on superfluids I'm still not sure if stuff like liquid helium at the lambda point actually have surface tension or not. Is superfluidity the same thing? And are there ...
3
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1answer
1k views
Bubbles in zero gravity
What happens if you blow bubbles into a glass of lemonade on the international space station?
Since you are weightless in orbit, there's no up, down, left nor right. We define down on the Earth ...
3
votes
1answer
360 views
Primer on Liquid/Ink Splatter Physics
I'm looking for primer material on the modelling the physics of liquids. In particular I want to make a small simulation (I'm a programmer by profession) of throwing ink at a board, much like this.
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4
votes
2answers
155 views
Dynamic ferrofluid sculptures
http://www.youtube.com/watch?v=UJJuq_pcyIQ
What exactly is going on in the video example? I understand the phenomena occurs because of magnetism but I am trying to figure out the mechanics behind ...
6
votes
4answers
2k views
Polar vs non-polar fluid
In the book "Vectors, Tensors, and the Basic Equations of Fluid Mechanics" by Rutherford Aris I read the following:
If the fluid is such that the torques
within it arise only as the moments of
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23
votes
3answers
1k views
When water climbs up a piece of paper, where is the energy coming from?
Take a glass of water and piece of toilet paper. If you keep the paper vertical, and touch the surface of the water with the tip of the paper, you can see the water being absorbed and climbing up the ...
4
votes
1answer
534 views
Why does measured pressure change over time in closed hose with temperature gradient
I have a 4' hose that is closed at one end and connected to a Airdata Test Set (precise control of pressure) and a high accuracy pressure monitor on the other end with a T and valve. The valve allows ...
2
votes
2answers
388 views
Potential functions
Can someone please explain what a potential is? Example. velocity potential in ideal flows, acoustic potential (gradient of which gives the particle velocity in a sound wave).
Whenever I see potential ...
36
votes
11answers
4k views
How long a straw could Superman use?
To suck water through a straw, you create a partial vacuum in your lungs. Water rises through the straw until the pressure in the straw at the water level equals atmospheric pressure. This ...
4
votes
3answers
416 views
What cools a drink?
When you stick ice in a drink, AFAICT (the last physics I took was in high school) two things cool the drink:The ice, being cooler than the drink, gets heat transferred to it from the drink (Newton's ...
5
votes
5answers
832 views
Is it possible to accelerate air to supersonic speeds? What would it look like?
The speed of sound is the rate that disturbances in air propagate through it.
Is it possible to have a wind that itself is moving at supersonic speeds relative to stationary winds around it?
Or ...
26
votes
10answers
2k views
Mechanics around a rail tank wagon
Some time ago I came across a problem which might be of interest to the physics.se, I think. The problem sounds like a homework problem, but I think it is not trivial (i am still thinking about it):
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5
votes
6answers
427 views
Why do liquids separate in space?
I've seen videos of people in space (on ISS) who squeeze a bottle or something and liquid comes out, it then separates into smaller balls.
Why is this surely it should stay pretty much together ...
3
votes
2answers
288 views
Low pressure, pulsating, series of water droplets
I want to create a stream of water that emits only a droplet of water, waits a few milliseconds, and then continues. The important thing is that I need to create a visible gap between drops.
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1
vote
1answer
161 views
What is required to create water droplets of a consistent size and shape over a distance of 3 to 10 feet? [closed]
What would I need to do to create water droplets of a consistent size and shape over a distance of 3 to 10 feet? Are there any special requirements for the nozzle?
Can I use pure water or should I ...
32
votes
10answers
4k views
Why does dust stick to rotating fan propeller?
Why does dust stick to rotating fan propeller?
Intuitively, most people (including I) think of the dust will not stick to rotating fan propellers.
EDIT 1:
Thank you for the great explanations. I am ...
8
votes
1answer
2k views
Why exactly does a boomerang return back to the thrower?
I was always intrigued by the phenomena that govern the returning back of a boomerang to the thrower.
Even if it is dependent on various factors such as velocity, aerodynamics, wind resistance and ...
10
votes
4answers
953 views
How does a steady wind flow generate sound?
When a wind blow through sharp edge, say, edge of a paper, you can see the vibration of the paper and hear the sound.
For this type of oscillation, it should be a damped oscillation with external ...
29
votes
8answers
9k views
Why does the atmosphere rotate along with the earth?
I was reading somewhere about a really cheap way of travelling: using balloons to get ourselves away from the surface of the earth. The idea held that because the earth rotates, we should be able to ...
10
votes
3answers
503 views
Which direction will Coriolis forces deflect a bubble?
If I throw a ball straight up, it deflects slightly to the west due to Coriolis forces. If instead I watch a bubble float up in water, is the bubble deflected west, east, or neither?
I think the ...
2
votes
1answer
309 views
Why do those dolphin bubble rings I saw in a video behave the way they do?
This (see http://www.youtube.com/watch?v=TMCf7SNUb-Q&feature=related) is so cool, I wanted to show it.
As a pro forma question for this forum, any idea what is going on with the breaking of ...
6
votes
3answers
2k views
Why does the water level equalize in a series of tubes?
Say I have a series of tubes (not the internet) looking like this, where w represents water:
...
3
votes
2answers
531 views
logarithmic wind speed profile
Under some atmospheric stability condition, over flat terrain, it has been observed for a while that the ratio between wind speed at height $h_1$ above the earth and the wind speed at height $h_0$ is ...
22
votes
3answers
1k views
What is the fallacy in this infinite motion machine?
I realize this isn't possible, but I can't see why not, especially if you change the model a little bit so that the balls simply travel through a tube of water on the way up, rather than exactly ...
2
votes
3answers
682 views
Distance travelled in free-fall
When an object is in free fall, we have:
$a(t) = g - \frac{c}{m}v(t)^2$
where $g$ is acceleration due to gravity, $m$ is the mass of the object, and $c$ is the coefficient of air resistance.
How ...
7
votes
1answer
157 views
How do subgrid-scale parametrisations in climate models work?
Global Circulation Models typically have grids of 100-300km on a side. There are obviously lots of atmospheric processes that happen at smaller scales than this. Convection, cloud formation, the ...
68
votes
3answers
5k views
What really allows airplanes to fly?
What aerodynamic effects actually contribute to producing the lift on an airplane?
I know there's a common belief that lift comes from the Bernoulli effect, where air moving over the wings is at ...
3
votes
1answer
99 views
Reference request: statistical inference with real world (chaotic) data, e.g. climate/weather data
I'm interested in the process that goes from, for example, huge data sets of temperature, pressure, precipitation etc readings to a model of the atmosphere. I'd like to know about how much relies on a ...
7
votes
1answer
469 views
Resolving water sink problem
There is a common myth that water flowing out from a sink should rotate in direction governed by on which hemisphere we are; this is shown false in many household experiments, but how to show it ...
