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

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Pressing a fluid through leaks

Say I have a cylindrical container of some volume $V$, that I fill with water or some other fluid with dynamic viscosity $\mu$. Here, the bottom of the container is milled such that some fraction, ...
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1answer
626 views

Physical Explanation for “Kolmogorov -5/3 spectrum” in Fluid Mechanics

According to Kolmogorov, the energy spectrum function of a turbulent fluid is given as, $E(k)=C\epsilon^{\frac{2}{3}}k^{\frac{-5}{3}}$ where $\epsilon$ is the energy flux and $k=\frac{2\pi}{r}$ ...
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2answers
189 views

Autocorrelation of sound in liquids vs gas

This is just a curiosity and you need to bear with me as my math skills were always sub-par and so is my English academic language. My specialty is Electronics but I have always been a programmer. ...
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1answer
868 views

Friction term in Navier-Stokes equation

The friction term in Navier-Stokes equation assumes that the viscosity coefficients are the same for the longitudinal and transverse directions. This doesn't seem intuitive, because the former is ...
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4answers
6k views

How does a hole's size affect the distance that water will squirt

I took a bucket, drilled 2 different sized holes on the side near the bottom and filled it with water. The stream of water the proceeded from the larger hole traveled further than the stream from the ...
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1answer
485 views

Why do nuclear bombs make a mushroom?

Atomic bombs make mushroom. It's well-known and we've seen many images of atomic experiments around the world. My question is, what causes the mushroom shape? Do conventional explosives like TNT and ...
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2answers
241 views

I noticed today that it is easier to open a soda bottle(standard 20 oz) upside-down, why is this?

Am I correct in assuming it is the weight of all that liquid + gravity?
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2answers
260 views

Why isn't pressure used for flight?

Why isn't pressure used as flight? I've heard that 2L bottles can hold a pressure of up to 90 PSI safely. Since $F = PA$, if the nozzle of a pressure rocket is about 4 inches squared in area, that ...
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2answers
1k views

How to calculate concentration of vapor at the surface of a water drop

I'm reading a paper that examines the evaporation rates of water. In the final formula, it has the following constant: $c_s - c_\infty $ where $c_s$ is the concentration of the vapor at the sphere ...
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1answer
9k views

How to calculate heat exchange/deltaT in a moving volume of fluid?

I am building a preheater for a maple syrup evaporator and am going to use the steam generated by the heating process to pre-heat the incoming sap from, say 5 degrees C to (hopefully) something on the ...
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1answer
476 views

Water droplet evaporation due to humidity and temperature

I am conducting an experiment that requires comparison to models for a water droplet's change in size due to evaporation. I've found plenty of papers, but they all seem to require measurement of the ...
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1answer
182 views

What software can I use to simulate supersonic gas particle flow? [closed]

Please please help me out with this. I am trying to find a software/program that I could use the simulate the scattering effect of light when it strikes gas particles moving at supersonic speeds? ...
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5answers
1k views

Why do blades of windturbine propellers as comp. to propellers of ships cover very different areas?

This is a thought I asked myself often, but never did real efforts to get an answer. Barsmonsters question about number of fans of a wind turbine made me think of it again Why do blades of aircraft ...
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2answers
550 views

the form of a kettle

What is the best form for a kettle, that is, to have the water boil the fastest? I am particularly interested in the following case: for one given kettle (whose volume is constant) containing ...
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3answers
2k views

Wind generators - why so few blades?

Why commercial wind generators usually have just 2-3 blades? Having more blades would allow to increase power OR decrease diameter. Decreased diameter would also reduce stress due to different wind ...
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votes
2answers
225 views

Entropy decrease using Stoke's flow?

There is a video of an experiment from University of Mexico using corn syrup (highly viscous) and water. They are "mixed together" in a container by turning a crank but when the crank is turned in the ...
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1answer
3k views

Will a lighter car have a higher top speed than a heavier car with an equal power engine?

If I have a car (with a particular engine) optimized (shape & weight distribution-wise) for attaining the top speeds possible, and I put that engine into a car which is heavier (but otherwise the ...
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1answer
601 views

communicating vessels formula

i having trouble with this formula (asked first in math.Se, i Didn't know the existence of physics.se) $$ Z1(t) = Ze+(\sqrt{Z1-Ze}-\frac{2S0}{S1}\sqrt{2g(1+\frac{S1}{S2})}.t)² $$ Z1 and Z2 are ...
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3answers
4k views

What nonlinear deformations will a fast rotating planet exhibit?

It is common knowledge among the educated that the Earth is not exactly spherical, and some of this comes from tidal forces and inhomogeneities but some of it comes from the rotation of the planet ...
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2answers
402 views

What is the dominant cause for ocean waves at a beach?

What is the dominant cause for ocean waves at a beach? Are they the result of wind/pressure difference? If so, the waves do seem to exist in similar intensity even during relative quiet times of the ...
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1answer
1k views

How to derive the Karman-Howarth-Monin relation for anisotropic turbulence?

I find the derivation of the Karman-Howarth-Monin relation in the book Turbulence from Frisch (1995) a bit to short. Can someone point me to a more detailed derivation of that relation, if possible in ...
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1answer
2k views

How to calculate the projected area at different angles/vectors?

Please help me with the following. I want to know if there is an equation/set of equations to find out the projected area of a (3-D) cube when it is oriented at different angles of attack to the fluid ...
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1answer
3k views

Why do some carbonated drinks fizz more than others?

Wired magazine ran an article this month on carbonation in soft drinks. If all soft drinks are manufactured effectively identically, why do some types fizz more than others? For example, root beer ...
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1answer
251 views

Olympic games and the local g

As you probably know, the two next Olympic games will take place in London and Rio. Randall, author of xkcd, did an interesting observation (that I had never thought of) in http://xkcd.com/852/ , ...
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1answer
781 views

Sutherland's constant of argon

I want to compute the viscosity of argon at different temperatures. What is Sutherland's constant of argon?
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2answers
254 views

How to calculate the effect of roof items on gas mileage?

I have a kayak and a bike. I routinely put them on top of my car and drive 60-70 mph for hundreds of miles. I am curious how much this affects my gas mileage.
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1answer
902 views

Fluid dynamics, flow of a 2D jet from a narrow slit

I'm working through some exam problems, and I came across this one - the solution of which baffles me considerably. A two-dimensional jet emerges from a narrow slit in a wall into fluid which is ...
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3answers
743 views

Boundary layer theory in fluids learning resources

I'm trying to understand boundary layer theory in fluids. All I've found are dimensional arguments, order of magnitude arguments, etc... What I'm looking for is more mathematically sound arguments. ...
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2answers
2k views

Shape of Fan Blades

How is the shape of the blades of an air fan determined? Trial and error, or is there a theory behind it? What are they trying to maximize, volume of air dislocated per rotation?
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1answer
431 views

Coffee cooling in a cup

Will coffee in two differant size styrofoam cups in the same room conditions cool at the same rate? One cup is 8 oz. and the other would be 12 oz.
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2answers
426 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 ...
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1answer
219 views

What is it that makes this structure cause turbulence?

I'm trying to design a quasi-simple vertical axis wind turbine, and a coworker came up with this design to focus the wind as it reaches the turbine in a wind tunnel. He says that there's going to be ...
6
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4answers
445 views

Would a fish in a sealed ball swim normally?

This question led me to wonder whether swimming would be the same experience for a fish in a full, sealed ball as it is normally. If the fish is about 7cm from the walls of the tank, a pressure wave ...
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3answers
590 views

Could a fish in a sealed ball, move the ball?

If you had a glass ball filled with water, completely sealed and containing a fish, could the fish move the ball?
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7answers
985 views

Does the wind gust over the ocean?

It is easy to observe that on a windy day, the wind does not blow for several hours at constant speed, then gradually subside. Instead, on a time scale of seconds or tens of seconds, there are ...
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1answer
518 views

Kinetic energy loss when a rigid body falls into water

Assume you have a rigid body falling into the ocean at terminal velocity. Also assume that the rigid body does not break on impact. How could you figure out how much kinetic energy would be lost in ...
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1answer
3k views

“Troll physics”: Buoyancy for infinite power [duplicate]

Possible Duplicate: What is the fallacy in this infinite motion machine? Most of the "troll physics" images I can figure out, but this one has me stumped. What is broken about the following ...
4
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1answer
206 views

How can you tell a model explosion from the real thing?

Movies and TV shows frequently show buildings being bombed, cars blowing up, etc. Frequently these are really explosions of miniatures filmed up close. Aside from the speed that the explosion ...
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4answers
354 views

Are smaller soap bubbles more accelerated by wind?

If you blow a bunch of soap bubbles outside, and a gust of wind hits them, will the bigger ones be more or less accelerated by the wind than the smaller ones? Intuitively, and maybe from remembered ...
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2answers
387 views

Laws of fluid flow in porous medium

What are the equations that describe the flow of a fluid in a porous medium? Is there a variation of the Navier-Stokes equations? I would like to model the flow of air through a sponge-like ...
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2answers
1k views

How to model/simulate pressures and flows in a network of pipes

I'm having a hard time finding information on how to model/simulate this. I attached a couple files, both of which show an example tank & pump network. It's just nonsense that I made up for this ...
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1answer
1k views

water flow in a sink

When one turns on the tap in the kitchen, a circle is observable in the water flowing in the sink. The circle is the boundary between laminar and turbulent flow of the water (maybe this is the wrong ...
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6answers
2k views

Is it possible for wind to break the sound barrier?

I understand that in nature wind would never get high enough, but I am just curious as to whether physics would allow this to occur or not.
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1answer
935 views

Pendulum with water dripping out

Consider a pendulum, consisting of a string of length $l$ tied to a ball of negligible mass and radius $r$. The bob is filled with water, which has density $d$, and the pendulum is given a small push ...
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8answers
3k views

Why there's a whirl when you drain the bathtub?

At first I thought it's because of Coriolis, but then someone told me that at the bathtub scale that's not the predominant force in this phenomenon.
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1answer
245 views

Shear, viscosity and expansion of universe

What is the meaning of expansion, shear and viscosity in context of universe? How can we conclude a result after getting a numerical value of above terms?
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2answers
528 views

A water drop in a falling lift

Consider a lift, which is at rest in an homogeneous gravity field. There is a thin layer(with thickness $h$) of water on the floor of the lift. At some moment a single cable, supporting the lift, ...
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6answers
709 views

Tsunami dampening mechanisms

Encouraged by the zeitgeist let me ask the following: Is it feasible (now or in the future) to build systems a certain distance of a vulnerable coastline which can serve to dampen a tsunami before it ...
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7answers
13k views

Why do tsunami waves begin with the water flowing away from shore?

A sign of a tsunami is that the water rushes away from the shore, then comes back to higher levels. It seems that waves should be both + and - polarized and that some tsunamis should go in the ...
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2answers
343 views

Mixed conductive and convective heat transfer

I want to make a finite element analysis of a cold airflow through warmer pipes. In particular I want to see how the pipes cool down and the air heats up, as it travels through the pipes. Wich are the ...