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

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368 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 ...
4
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4answers
405 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
421 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 ...
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2answers
238 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
391 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, ...
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2answers
500 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
202 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
570 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 ...
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1answer
206 views

Measure maximum volume of liquid of a water tap

I need to know the consumption of a water tap in Liters. I'm able to know the cross-sectional area of the pipe and how long the tap is open. With these data, how can I know the consumption/volume of ...
5
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1answer
556 views

Why does the milk frother on my coffee machine make so much noise?

I have a Sunbeam home espresso machine with a steam wand. The steam roars out straight from the end of the wand. When it's first placed in the cold milk it really screams! Once the milk has a bit of a ...
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2answers
847 views

How to relate speed of sound with relative humidity?

I am exploring the idea of measuring the humidity of a space using sound waves, however I am having trouble finding a mathematical relationship between the speed of sound and the humidity level. ...
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2answers
193 views

Cascade in relativistic turbulence

The Kolmogorov theory of turbulence indicates an energy cascade in turbulence. Is there a corresponding version of relativistic fluid?
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2answers
510 views

How can these fluid dynamical smoke-ring phenomena be explained?

The Navier-Stokes fluid dynamics equations, said that, as Sir William Thomson (or Lord Kelvin) predicted: When two smoke-rings are moving in the same direction, with the same speed, one behind the ...
4
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3answers
161 views

Effect variable cylinder radius has on airflow

Can someone shed some light on the following problem? I'm unable to get any traction on it as I know nothing about fluid dynamics (I'm a computer engineer). It's a problem I made up over a lunch ...
5
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2answers
93 views

Influence of choice of statistics on gas kinetics

In the derivation of distributions over energy states, a common assumption made is that under normal conditions (normal from a fluid dynamics standpoint, so > 300K typically) the energy states are ...
19
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1answer
373 views

Flames with no gravity?

I was watching "Solaris" (Tarkovsky) today, and noticed this: in some moment the space station changed orbit and the people inside experienced zero-gravity. At that moment, a candlestick passed ...
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5answers
751 views

Why cant one see tidal effects in a glass of water?

Why cant one see the tidal effect in a glass of water like in an ocean?
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1answer
130 views

How do I calculate speed of air on each side of airfoil?

I am doing a project on Bernoulli's principal for my High School physics course. I made an airfoil in accordance with NACA 2412 (same as a C-152). I am going to put it in a wind tunnel where the ...
12
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3answers
3k views

Does a wing in a potential flow have lift?

I have a hard time understanding whether or not a wing placed in a potential flow, assuming there is no viscosity and no friction with the wing, will produce a lift. I've seen several contradictory ...
3
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1answer
244 views

Showing symmetry of the stress tensor by applying divergence theorem to $\int\int_{\delta V(t)} \vec{x}\times \vec{t} dS$

I'm currently working through the symmetry of the stress tensor, in relation to viscous flow. I am looking at this by examining the conservation of angular momentum equation for a material volume ...
6
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1answer
741 views

Can you measure the speed of water coming out of a hose by its arc?

Water comes out of a horizontally stationed hose and creates an arc as it heads towards the ground. Can I determine the speed the water was traveling in when it exited the hose by the measuring the ...
10
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2answers
556 views

Calculating Reynolds number for a viscous droplet

I'm trying to develop a very basic scaling law/unit analysis for viscous droplet formation, and I'd like to get some rough numerical values of the Reynolds number to play with. To be specific, I'm ...
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3answers
652 views

What are the coefficients α, β, and κ in this equation for decompression-induced gas bubble growth?

I am reading a text about gas nuclei I encountered the following formula: $$r = \alpha + \beta \left( \frac{T}{P} \right)^\frac{1}{3} + \kappa \left( \frac{T}{P} \right)^\frac{2}{3}$$ $r$ is the ...
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3answers
739 views

Why are Navier-Stokes equations needed?

Can't we picture air or water molecules individually? Then, why are Navier-Stokes equations needed, after all? Can't we just aggregate individual ones? Or is it computationally difficult, or ...
2
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1answer
869 views

Pump pressure required to fill water tower

I have a water pump at a distance of x meters from a water tower located h meters above the pump through a pipe with diameter d. I am not concerned with the exact value just want to make sure my pump ...
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0answers
387 views

What is the pressure in a vertical pipe that has moving fluid through it?

I have a system like this When the valve is closed, pressure along any point along the thin tube may be found thru pgh. 1. What about when the valve is opened? 2. Does the top of the jar need to be ...
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2answers
769 views

Euler equation of fluid dynamics

I'm trying to obtain Euler equation for a perfect fluid in laminar or stationary flow. A particle fluid is submitted at volume forces and surface force. The fist, in my case, is giving only by gravity ...
3
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1answer
282 views

Rayleigh-Benard Convection

I found this nice paper about RB convection. However I am confused by what is going on page 6. In particular why we are suddenly using Helmholtz equation to find spatially periodic solutions. Aren't ...
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1answer
639 views

Why does my natural whistle have a maximum volume

When I whistle, I find that I can vary the volume by pushing more or less air through my mouth at once. However, when I increase volume past a point, I start to hear a blend of rushing air and a ...
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4answers
4k 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 ...
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1answer
149 views

Does water have the same surface tension at same temperature but different volume?

I'm making an experiment and it is written in my older questions. Now, my question is - Does water have the same surface tension at same temperature but different volume?
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1answer
440 views

Lotus effect dust removal

I have found hundreds of papers describing the contact angle of water droplet sitting on hydrophobic surface and the change between Wenzel Regime and the Cassie-Baxter regime. Now, as I understand ...
0
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1answer
164 views

What caused Simon Faithfull's chair to fall appart?

There is an art/science video clip on youtube, by Simon Faithful, called Escape Vehicle no.6 (chair in space). It shows a simple steel office chair, tied to a weather balloon, ascending into the upper ...
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2answers
569 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 ...
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2answers
94 views

How would I work this continuity problem?

I am trying to design a system for a project and I need some input on if this is right or not. I have $10 \frac{kg}{s}$ of fluid flowing through a pipe. It breaks up into $10$ 1 inch diameter pipes. ...
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1answer
563 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.
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1answer
237 views

Why does water make a liquid film?

Cut a narrow slit in a thin sheet of opaque material. Immerse the sheet in a liquid, such as water. After removing the sheet from the liquid, you will see a liquid film in the slit. The question is: ...
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2answers
741 views

Bernoulli's equation and reference frames

So I was thinking about this while driving home the other day. I've never been quite clear on why when you drive with the windows down air rushes into your car. I thought this might be explained by ...
3
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1answer
193 views

What velocity must an aircraft achieve for its shock wave to transform to plasma?

A follow-up to After what speed air friction starts to heat up an object? I understand there may be technological limitations at present ... but, is it theoretically possible for a body to travel ...
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1answer
3k views

Boussinesq approximation for the Navier Stokes' equation - discrepancy

In the Navier Stokes' equation: $\rho_0 \left( \frac{\partial v}{\partial t} + v \cdot \nabla v\right) = -\nabla p + \mu \nabla^2 v + \hat{f}$ I included the temperature variation of density as ...
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1answer
308 views

Trying to link Eulerian and Lagrangian perturbations

I'm trying to make sense of the link between a (linear) Eulerian (i.e., at a given point) and Lagrangian (following a fluid element) perturbation. I will here express not only where I'm stuck, but ...
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1answer
260 views

By how much will water resistance and upthrust slows down a fully submerged object?

Consider the following example: While running, I do work and I have a certain velocity and acceleration. When I'm in a pool (my feet are touching the bottom), I do the same work but, I have less ...
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2answers
213 views

When playing the flute, does lip-hole aperture size affect air pressure in the mouth?

I apologize if this is too basic of a question for this forum, but when having arm-chair discussions about the fluid dynamics of flute playing, a friend has said: The lip-hole area together with ...
2
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1answer
182 views

Why does central jet velocity of a flute air stream not include aperture size?

Some fellow flutists and I are pretending to be experts at fluid dynamics and reading Patricio Cuadra's thesis on the topic: On page 17, it says: The central speed of the jet $U_j$ at the channel ...
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4answers
171 views

Particles scattering on fluids: breakdown of the effective continuum description

When does the macroscopic continuum description of a medium like a fluid break down? Say I'm interested in a scattering process of some particles with momentum $p$ and energy $E$ off a fluid of ...
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2answers
268 views

Is surface of a solid a streamline?

In fluid dynamics, streamlines are defined as line where at each point flow velocity is tangential to the line. Is it correct to say surface of a solid a streamline? On the surface the velocity vector ...
2
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1answer
277 views

If there is significant temperature difference between indoor air and outdoor air, will that significantly increase the rate of air exchange?

There would be heat diffusion, of course, but heat diffusion occurs even without the exchange of fluid parcels between each environment. We do know that cold air tends to be denser than warm air, and ...