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

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Satellite droplets in a breaking liquid jet

The famous example of a dripping faucet is an example of a Rayleigh-Plateau instability in which there is a certain jet radius below which perturbations on the surface will grow to break the jet into ...
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3answers
4k 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 ...
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2answers
91 views

How does the correlation length of weather emerge?

The question is pretty simple: If I know the weather where I stand, I can estimate the weather 5 meters or 1 km away away pretty well, but I'll have a hard time guessing what the weather is, say, 50 ...
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3answers
304 views

A simple logical problem regarding pressure and force

Suppose a 2 meter long pipe, with area of cross section is $1 m^2$. The pipe is vertically placed, with the bottom end closed. Inside the pipe, at the closed bottom end, there is $1 m^3$ of air, ...
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1answer
345 views

Compressible fluid flow through a branched pipe junctions

Backdrop: Designing a dust extraction system (LEV) with a branched junction. What principles allow for the calculation of volume flow rate and pressure at the inlets if the volume flow rate and ...
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1answer
411 views

Best way to move teaspoon to dissolve sugar in a cup of tea

I know that there is asked questions about something like cooling down cope of coffee..etc, but this one is little different. My friend was watching TV program of English eating etiquette, and they ...
2
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1answer
712 views

Can silicon droplets bouncing on a vibrating surface be a model for Quantum Mechanics?

In this video on youtube it is claimed that silicon droplets bouncing on a vibrating surface show behaviour in analogy to particle/wave duality in Quantum Mechanics. Is this true? Did they ...
7
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3answers
288 views

How do I intuit viscosity in a rotating fluid?

Suppose I have two plates with a viscous fluid in between. I slide them in the same direction (a direction in their own plane), one at $5 \,\text{m/s}$ and the other at $6 \,\text{m/s}$. Due to the ...
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1answer
48 views

Depends river stream on river level?

If we have referral particle in the middle of the river, will it's velocity increase with higher river level?
6
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1answer
310 views

Gravity duals to Navier Stokes and interpretation of non linear contributions

I have been reading the paper The Incompressible Non-Relativistic Navier-Stokes Equation from Gravity. In it they state, "An instability, if it occurs, must necessarily break a symmetry ... ...
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2answers
312 views

Can wind blowing on smooth water create speckle interference patterns?

On a calm smooth lake, or even a large rain puddle, I've seen transient rough patches on the surface suddenly appear and disappear, and sometimes move across the water some distance before ...
7
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2answers
231 views

Where can I check a solution to 3D Navier Stokes?

A few years ago I developed a solution to the Navier-Stokes equations and as of yet have not been able to locate a similar version of the solution. I would like to know if anyone has seen a solution ...
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1answer
210 views

Swimming and forces

I was told that the total integral of the stress over the surface of a swimmer (i.e. the total force exerted by the swimmer on the fluid) always vanishes, because there are no external forces applied ...
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1answer
381 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 ...
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3answers
278 views

The viscous force between the layers of liquid is same, then why there is variation in the velocities of its layers?

I have learned in my textbook that when the liquid flows the bottom layer of the liquid never moves because of friction, but the upper layers move with increasing velocities how it is possible if the ...
3
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0answers
72 views

Sound level of organ pipe driven by helium

The sound pressure level of an organ pipe is a function of the gas flow rate delivered to the pipe. Source Would the sound level of an organ pipe driven by helium be lower than that of a pipe driven ...
2
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0answers
84 views

Stat mech explanation for separation of one liquid from another in gravity?

If one mixes two distinct ideal gases above the Earth's surface, one with a higher molecular mass than the other, then at equilibrium, their number density gradients will be such that at low heights, ...
2
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1answer
268 views

Is it wrong to associate non-isotropic flow high with Reynolds-Number and is there a better metric?

IT is often stated the flow with high Re is not isotropic, meaning there is no uniform or dominant direction of the flow. But this seems wrong to me - -while there's certainly cases where no dominant ...
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1answer
58 views

Disregarding drag force that affects pop-up lightweight ball

Is it possible to disregard drag force of water with no viscosity that affects lightweight pop-up ball (its weight is assumed to be zero)? There is a discussion, on which I consider that although ...
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3answers
552 views

How much effect does the Bernoulli effect have on lift?

I understand that the Bernoulli effect is a flawed explanation for the cause of lift, and does not cause much at all, but how much? Is there any experimental data on the force caused by the ...
2
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3answers
534 views

Why does smoke go inside the car if the back door is open?

Inspired by another question I wanted to ask about phenomenon that I've experienced. We had a van with separate trunk deprtment (similar looking one below) to transport things. But some of the things ...
2
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0answers
147 views

Turboshaft Turbine Mathematical Model

Are there any simplified mathematical models for how two gas coupled turbines (also called a free power turbine) should interact with one another as the speed of the driving turbine changes. (i.e.) ...
2
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0answers
91 views

Wrinkling paint - soluto/thermocapillarity - is it due to the primer or solvent [closed]

This is really a one-and-a-half part question. I know that when paint is mixed with a solvent or used with a primer, it sometimes wrinkles. As I understand, a key physical phenomena here is a ...
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4answers
2k views

Why does smoke go out the window of the car - and what if there's wind blowing instead of the car moving?

When driving a car while smoking with the window open (safety and legal issues aside), I've noticed that the smoke tends to go outside the window. Why does the smoke go outside? If the car is ...
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2answers
517 views

How does liquid in a ball affect its rotational acceleration down a ramp?

Suppose we have a shell with mass $M$ and radius $R$. If we let that roll without slipping down a ramp of angle theta to the horizontal, we can easily find the acceleration of the shell the instant ...
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7answers
12k 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 ...
3
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1answer
192 views

How does a hinge affect the amount of a submerged material?

Suppose I have a rod that has a density of $X <1$. If I were to submerge that rod in water (density 1), I would expect $X$ of the rod to be below water and $1-X$ of it to be above water (simple ...
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1answer
181 views

Is it possible for an object to stop sinking after a while?

Suppose you drop an object into a body of fluid (on a planet with constant gravity). Suppose the fluid is pure (as in, there are no solid granulates or bubbles present in it), and finally suppose that ...
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1answer
337 views

thought experiment involving water pressure

If I were to move the syringe up, and cause it to be stationary, how does that effect the pressure at the bottom of the pipe? How does the movement of this water effect the system setup and ...
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1answer
826 views

How can the Moon have such a strong effect on the ocean?

The gravitational acceleration on Earth is approximately $ 10 \mathrm{m}/\mathrm{s}^2 $. Compared to this, the tidal effect of the Moon's gravity gives a local variation in the acceleration of ...
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0answers
310 views

How to calculate the Darcy-Weissbach friction factor for shear thinning laminar flow in a pipe?

The Darcy-Weissbach friction factor for laminar flow would be $\frac{64}{Re}$ Now, having a shear thinning (non-newtonian) fluid where the viscosity is not constant how do I arrive at $Re$? To know ...
2
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3answers
902 views

Apparent paradox in equation of continuity

Equation of continuity says us that if we insert some fluid in a tube, the same amount of fluid will come out from the other end. If we make a small hole in a hose pipe, water will come out with a ...
2
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1answer
252 views

Evaporation of water content from a solid material by applying low pressure

I have a raw material which melts at $96\ ^\circ C$. My aim is to make water content evaporate at temperature below this temperature. I can apply vaccume oven for this. I want to know at what pressure ...
6
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1answer
294 views

Why do air bubbles stick to the side of plastic tubing?

I'm watching water with air bubbles flow through transparent plastic tubing. The inner diameter is a few mm. Bubbles typically are the same diameter as the tubing, with length about the same or up ...
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4answers
1k views

How much information about the scale of a waterfall can be obtained from its sound?

Is it possible to constrain the height, volume flow, or distance of a waterfall from the quantitative analysis of a high-quality recording of its sound? As an aside, the simulated sounds of fluid ...
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1answer
272 views

What causes the structure visible in first few milliseconds of a nuclear explosion?

Following on from this question, here is a high-speed photograph of a nuclear explosion, taken about 1 ms after detonation: (source) As anna v pointed out, several similar images can be seen in a ...
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1answer
181 views

Atmospheric Circulation

What is the simplest simulatable model giving our rotating earth its 3 circulation cells (Hadley, Ferrel, Polar)? The model should also show 1 circulation cell if the earth's rotation were stopped (or ...
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5answers
307 views

How can the surface of a liquid exist if there are no attracting molecules above it?

Okay this is probably a stupid question but here goes: We know that molecules in a liquid are attracted from all the molecules around it so there is no net attraction. Well, then how do the ...
6
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1answer
160 views

Could the Bernoulli effect be causing my ceiling to come down?

Very 'applied' question, but I have nowhere else to turn, so I'm asking the physics experts here: I have a carport whose ceiling is made of very lightweight paneling. I've had several times now that ...
2
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1answer
357 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 ...
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4answers
394 views

What is the term for hose fluctuating movements during flow?

What do we call it when water flowing through a flexible hose causes it to act like snake movements if the hose were disturbed? Can this movement be explained by the Coriolis force?
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3answers
414 views

How can I keep a smaller water reservoir's water level at half available when being fed from a larger reservoir? [closed]

I'm trying to create my own ultrasonic humidifier. I ordered the misting part which works great but it only functions correctly in shallow water. So I'd like to feed from a large water reservoir to a ...
1
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2answers
223 views

Is it true that under water human body can sustain higher levels of acceleration?

In several sci-fy novels, I've read about humans being submerged in water (or water like substance) to allow for a higher acceleration. Now, I'm really curious. Is this true? Can you accelerate faster ...
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0answers
65 views

Does Bernoulli's principle hold in moving reference frames? [duplicate]

Possible Duplicate: Bernoulli’s equation and reference frames Sometimes in train, when setting behind opening window, I can feel strong gale blowing in. The closer to the window the ...
4
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2answers
1k views

Why do cars gain lift while going at a high speed?

I've been researching the physics involved with spoilers and I've just been turning up the same information about spoilers giving the back wheels of a car more traction by acting as an up side down ...
7
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2answers
383 views

At what velocity does sea water leave a pipe run into a fresh water lake (for equal surface levels)?

If I took a fresh water lake* whose surface is exactly as sea level, and connect it to the sea with a pipe filled with sea water, with both ends of the pipe at exactly the same depth from the surface, ...
10
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2answers
493 views

Energy from man-made tornadoes

Peter Thiel just paid $300,000 to Canadian inventor Louis Michaud who is working to construct useful "man-made tornadoes" or "atmospheric vortex engines" which could be components of future power ...
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0answers
61 views

Displacement of a Rock Thrown Overboard [duplicate]

Possible Duplicate: Basic buoyancy question: Man in a boat with a stone If you have a large boulder on a boat, in a pond, and you throw the boulder overboard and into the pond, would the ...
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1answer
196 views

Increment of surface tension with increase of temperature

What is the reason for the increase in surface tension of molten copper/cadmium with increase in temperature?
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2answers
553 views

How deep is the Great Red Spot?

The Great Red Spot (GRS) is a very persistent storm system that's easily visible through a telescope on the surface of Jupiter. But what is the three-dimensional structure of the GRS, and how deep ...