The quantitative study of how fluids (gases and liquids) move.
8
votes
1answer
251 views
Why does a transformation to a rotating reference frame NOT break temporal scale invariance?
Naively, I thought that transforming a scale invariant equation (such as the Navier-Stokes equations for example) to a rotating reference frame (for example the rotating earth) would break the ...
8
votes
5answers
337 views
What can wavy patterned sand tell about the Fluid that formed it?
Sand on the bottom of the ocean as well as sand on the low-tide beach often forms wavy patterns. Do the parameters of these wavy patterns have any relation to the water and waves that formed them? If ...
5
votes
2answers
252 views
Explanation that air drag is proportional to speed or square speed?
A falling object with no initial velocity with mass $m$ is influenced by a gravitational force $g$ and the drag (air resistance) which is proportional to the object's speed. By Newton´s laws this can ...
5
votes
3answers
677 views
Why do non-Newtonian fluids go hard when having a sudden force exerted on them?
You can dip your hands into a bowl of non-Newtonian fluid but if you are to punch it, it goes hard all of a sudden and is more like a solid than anything else.
What is it about a non-Newtonian fluid ...
5
votes
1answer
137 views
Distance a curveball travels?
I've seen some discussions regarding the movement of a spinning object, say a curveball. However, all have been largely qualitative. I was wondering if anyone has seen or worked through a ...
5
votes
2answers
797 views
Why does pressure act as a source for the gravitational field?
I'm asking for a qualitative explanation if there is one.
My own answer doesn't work. I would have guessed it's because when a gas has pressure the kinetic energy adds to the rest mass of a given ...
4
votes
1answer
171 views
Can a hovering helicopter travel half the globe in 12 hours? [duplicate]
Suppose we have a helicopter that is able to stay stationary in flight for extended periods of time. If such a helicopter stayed at point A in the sky for 12 hours straight, would it reach the other ...
4
votes
3answers
330 views
A fly in an accelerating car
A fly is flying around in a car, the fly never touches any surface in the car only fly’s around in the air inside the car. The car accelerates. does the fly slam in to the rear window. or does the fly ...
4
votes
4answers
435 views
How far can water rise above the edge of a glass?
When you fill a glass with water, water forms a concave meniscus with constant contact angle $\theta$ (typically $\theta=20^\circ$ for tap water):
Once you reach the top of the glass, the water-air ...
4
votes
2answers
2k views
Flow of liquid among branches
If water is flowing through big pipe is branched into 4 branches of small pipe. Lets say the flow is around 4 m/sec.
I have the following questions:
What will be the flow rate in each of the ...
4
votes
1answer
267 views
wind vs air resistance
I'm wondering which offers more resistance: pulling an object at some speed through air, or holding the object steady against wind at the same speed.
I think initially people would think same ...
4
votes
2answers
352 views
When water is about to boil
Have ever noticed? When water is about to boil, no matters the kettle, there is some sound I have no idea where it comes from, sometimes long before it boils.
Is there any explanation for this ...
3
votes
0answers
54 views
How do Kolmogorov scales work in shear thinning fluis?
My understanding of Kolmogorov scales doesn't really go beyond this poem:
Big whirls have little whirls that feed on their velocity,
and little whirls have lesser whirls and so on to viscosity.
...
3
votes
2answers
164 views
Air velocity in a double-skin facade
I was wondering how the air flows in a double skin facade? Say I have a glass facade with a depth of 1m, a height of 200m and a width of 10m. It is a single vertical shaft all the way up with openings ...
3
votes
2answers
181 views
At what size will self-gravitation contribute more to stability than surface tension?
The governments of Earth have embarked on an experiment to place a massive ball of water in orbit. (umm... special water that doesn't freeze)
Imagine this to be a fluid with a given density, $\rho$ ...
3
votes
2answers
530 views
Is the wind's force on a stationary object proportional to $v^2$?
I am on a boat docked at Cape Charles, VA, about 30 or 40 miles from the center of Hurricane Irene. This understandably got me thinking about the force of wind on the boat. Since air friction is ...
2
votes
1answer
108 views
Sideways motion between a vertical launch from a planet and landing [duplicate]
I saw a video some days ago (Hello Kitty in Space) of a schoolgirl successfully launching a balloon into space which later popped and landed ~47 km from launch site.
If I vertically launch an object ...
2
votes
1answer
215 views
Limitations of drag equation
The magnitude of the air resistance for objects with Reynolds numbers greater than 1000 is given by the formula:
Why it does not hold for objects with lower Reynolds numbers? Can I use this ...
2
votes
1answer
320 views
What is the best tool for simulating Vacuum and Fluids together?
I require a software to simulate Fluid simulation with the capability of supporting vacuum simulation. My requirements are that all numbers must reflect their real counterparts almost exactly. For ...
2
votes
1answer
84 views
Beer bottle leftovers pour quickly only after waiting?
Why is it that after pouring a delicious beer from a bottle, I can hold it upside down for several seconds without reward, but if I wait a bit, the remainder presumably settles at the bottom and ...
2
votes
1answer
412 views
How much water must flow trough canal to maintain a constant water deep?
In order to maintain a constant water deep in canal, how much water must flow trought the pipe ?
As shown on picture, canal have a rectangular shape.
I don't know if canal length have an influence.
...
2
votes
1answer
538 views
Free Body Diagram of Fluid Statics Problem
I need help determining the forces, and the direction of them in this fluid statics problem.
A hollow cylinder with closed ends is 300mm in diameter and 450mm tall. It has a mass of 27kg and a tiny ...
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 ...
1
vote
1answer
65 views
Explanation for the next steps of chaplygin dipole
this post is the Chaplygin dipole, it's an interesting issue.
Can someone explain me these steps in other words please? any Explanation of any step will help me, I hope that together I will ...
1
vote
2answers
423 views
Free fall of two spheres made of same materials, different masses, with air resistance
Two people falling with the same parachute will gain different speeds if their masses are different. The upward air drag will needed to be bigger for a heavier person, since gravitational force is ...
1
vote
2answers
348 views
Speed of sound in astrophysics
Why is the speed of sound given so much importance in Astrophysics? For example in gas outflow (and accretion) problems, we often calculate the sonic point (the point at which the outflow speed ...
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 ...
0
votes
1answer
63 views
Can anyone explain what a superleak is?
In the context of Helium can anyone explain what a superleak is and why it could be useful?
0
votes
1answer
284 views
Lamb-Chaplygin dipole
There is an interesting issue of hydrodynamics: whirlpools.
I want to learn about the Lamb-Chaplygin dipole.
Lamb-Chaplygin dipole corresponds to a steady solution of the two dimensional Euler ...
0
votes
1answer
185 views
Calculational method for determining surface tensions from photograph of menisci?
How can I get from a photograph of a liquid surface to a value for the surface tension.
0
votes
1answer
110 views
Liquid analog of the Black Hole (Part 2)
Similar question has been asked but did no get good answers.
We know that black hole can confine light, but can we create an ocean black hole -
which can confine surface water waves or sound waves in ...
0
votes
2answers
773 views
Physics behind Water drops during falling from a tap
what is physics behind Water drops during falling from a tap.
water drop animation
A drop or droplet is a small column of liquid, bounded completely or almost completely by free surfaces.
Why Water ...
-2
votes
2answers
157 views
Why does the higher pressure of air underneath an aeroplane wing keep it flying?
With aeroplane flight, the wings are shaped so that the air that goes over the top of the wing has to travel faster than the air that goes below the wing. This means that the air below the wing has ...
