# Tagged Questions

The quantitative study of how fluids (gases and liquids) move.

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This is a deceptively simple problem in fluid mechanics that I can't quite figure out because it produces a paradox. Suppose that there is a straw and a small column of water inside the straw, such ...
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### Pressure required to overcome surface tension

Imagine I have a vertical straw, and that it is partially filled with water. If I were to decrease the radius of the straw at the bottom end, eventually surface tension would allow the water to remain ...
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### flow rate measurement of a fluid

I had an experiment related to piping networks in my institute. In the experiment there was a device that was measuring flow rate based on rotations of a fan-like system. This created a doubt in my ...
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Could anyone suggest a good introductory book or any online resource about vorticity? I just now started to learn physics but I have a good mathematical background.
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### Submerged water jet

I am trying to calculate at what pressure and speed water from a high pressure water jet will hit an object 100 millimeters away from the nozzle opening, but i can't figure it out. The nozzle will ...
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### What amount of force could be created by a person “swimming” in air?

Had a question on a physics test, a person is at rest on a frictionless surface and can not throw anything, can they move? I said yes, by "swimming" against the air and got docked because "it wouldn'...
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### Atmospheric pressure changes on plastic bottle containing a liquid

We have a problem at work and I need some help on a theory. We ship a liquid in plastic bottles using a pump closure. Recently some of the bottles have been arriving to customers having leaked. The ...
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### Entropy and vacuums

If I have a vacuum (completely devoid of any particles; Q.M. effects aside), then turn a nozzle and let a gas freely expand into the vacuum, will I have increased the entropy of the vacuum? I get ...
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### Wall Shear Stress

I have the solution of a Navier-Stokes simulation with an incompressible, Newtonian fluid with laminar flow. Now I compute the wall shear stress (vector) as $$\tau_n = \mu (\nabla u) n,$$ where $\mu$ ...
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### How long time before all the water in a lake has been replaced? [closed]

Studying hydrology, and in that context we've seen some information about lakes and the times it takes for the water to renew completely in them. This got me interested in finding out how this is ...
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### Rankine Oval is oval shaped

I'm studying Rankine oval and I have a question. How do you prove the equation for its zero streamline curve is in fact oval shaped? Is there some family of oval shaped curves including Rankine Ovals? ...
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### How much load does an aqueduct support?

Recently, I found out about /r/InfrastructurePorn, and I found a particularly interesting photo of the Gouwe Aqueduct in Gouda, NE: It seems like the bridge that is supporting the boat wouldn't be ...
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### How does capillary action work in tubes which are closed at the top?

In all textbooks the examples and descriptions use tubes which are open at both ends. Our teacher remarked that if it were closed at one end like a test tube (albeit a thin one) even then capillary ...
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### How does a fluid force behave at different angles?

I have a mock exam problem that deals with fluid forces acting at different angles. Here are the scans: Based on the description of the systems, I know that in (a) and (c), F is going to equal the ...
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### How does the viscosity of a non Newtonian fluid (ooblek) affect its resistance to electricity?

I know the conductivity of water is based on whatever is dissolved into the solution, hence pure water does not conduct electricity. However, these ions in solution must also be free to move around. ...
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### Efficient way to move water pumping vs circulation [closed]

I have a basic question about efficiency of pumping. If I have a well of 100 meters depth, but water filled till top, and I want to circulate the water. What will be most energy efficient. A) ...
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### I want to increase pressure of water in a closed vessel [closed]

I am trying to make a high pressure water jet using DIY hand pump which pushes water into a sealed vessel with non-return valve at the inlet. I am planning to do it by first closing the valve to the ...
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### Why is a controlled shear test compared to the natural flow?

Looking for the areas where contolled shear stress (CSS, where force is fixed while rate of deformation is measured) and controlled stress rate (CSR, where conversely the force is measured while ...
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### Phase diagrams and critical pressure

If a solid substance is pressurized past its critical pressure, what happens? Is the critical pressure only a factor when a substance is over the critical temperature also? On another note what makes ...
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### Continuity Equation in Differential Geometry

I'm looking for a derivation of the mass continuity that applies in general on symplectic manifolds. In particular the "the amount of change in the mass in a volume is just amount that flows in or out"...