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

learn more… | top users | synonyms (1)

4
votes
2answers
7k views

Calculate fluid pressure loss due to hole leakage

I have a cylindrical pipe of internal diameter of around 5mm, with pressurised fluid flowing though it. If I have holes at the wall of the pipe, how do I calculate the pressure loss due to water ...
4
votes
2answers
218 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, $\rho$ ...
4
votes
2answers
214 views

Dynamic ferrofluid sculptures [duplicate]

http://www.youtube.com/watch?v=UJJuq_pcyIQ What exactly is going on in the video example? I understand the phenomena occurs because of magnetism but I am trying to figure out the mechanics behind ...
3
votes
2answers
2k views

Why does sweetness of coke change after freezing completely

I freeze my coke in a freezer completely to solid and then keep it out to melt and as it melts portion by portion I starts to drink, initially It will be very sweet and later it wont be sweet at all. ...
3
votes
4answers
3k views

Dyson Air Blade as a propulsion system?

I've read from many sources that Dyson Air Multipliers are more efficient and quieter than normal fans. Now, with the proof of concept, is it possible to use its principles as a propulsion system for, ...
3
votes
0answers
139 views

Difference between a Fixed Point and a Limit Point in implementations of the Renormalization Group (RNG) in Large Eddy Simulation (LES) model

In the introduction of this paper, it is explained that and how the application of a dynamic subrid scale model for turbulence into a large eddy simulation (LES) model corresponds to doing one ...
3
votes
2answers
234 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
1k 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 ...
3
votes
1answer
200 views

What keeps the sugar suspended in the tea?

At room temperature.... How long will the sugar stay suspended once dissolved ? What governs the rate of settling ? What part does Brownian motion play ? Sugar might be a bad example...please ...
2
votes
1answer
29 views

Effect of small changes in atmospheric pressure on open cylinder piston

OK, I'm not a physics student, but I played one for 2 semesters 35 years ago... now I'm a competitive shooter working a theory about why small changes in atmospheric conditions cause our hyper-tuned ...
2
votes
1answer
160 views

Entropy is constant. How to express this equation in terms of pressure and density?

In hydrodynamics of an ideal, non-compressive flow we use 5 variables: pressure $p$, density $\rho$ and velocity field $\mathbf{v}$. So we need 5 equations. Landau's "Hydrodynamics" states that the ...
2
votes
3answers
16k views

How to establish relation between flow rate and height of the water column of the tank?

Suppose a water tank has 1" diameter drain at the bottom and is filled with water up to one meter height above the drain. What time it will take the tank to drain out completely. Now say, the tank is ...
2
votes
1answer
1k views

Drinking juice through a straw

Why we are able to suck more drink through a larger diameter straw than a smaller diameter straw if $p_1 v_1 = p_2 v_2 = Q$ as per Bernoulli's Principle. The pressure difference I create in mouth ...
2
votes
3answers
913 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
votes
1answer
456 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
2answers
734 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
146 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
2answers
378 views

Fluid Dynamics - Water Bottle Drink Mix: Air or No Air?

If you take an ordinary sized plastic water bottle full of water and pour a packet of powdered (or liquid) drink mix into it, Will shaking the bottle with the cap screwed on to dissolve the mix into ...
2
votes
1answer
997 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
516 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 ...
2
votes
1answer
232 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 ...
1
vote
3answers
89 views

Why dont we consider force exerted by atmospheric pressure in mechanics?

My school has started teaching fluid mechanics, and it really bugs me why we don't consider force exerted by atmospheric pressure in mechanics. I couldn't understand a word my teacher said. There is ...
1
vote
0answers
85 views

momentum equation to find velocity of solid particle after collision [closed]

If a particle collides with a liquid drop, particle might penetrate into drop and so the velocity of particle reduces. i.e. a sudden change in particle velocity happens right at the collision moment, ...
1
vote
1answer
133 views

Positions and corresponding terminology of “acoustics energy”?

From limited knowledge, decades ago, dating back to the nineteenth century: Ohm's law of specific acoustic energies was the first biological application of Fourier's theorem. Actually, it was ...
1
vote
2answers
223 views

Is viscosity a function of density only?

I know viscosity is also a function of temperature, but (excluding superfluids) are there any fluids which are less viscous than fluids at lower densities? Is density the ultimate control on ...
1
vote
2answers
713 views

Gas viscosity at high pressure, high temperature

EDIT 1 PER COMMENTS I am wanting to model nitrogen gas viscosity as a function of pressure and temperature OR learn of an existing equation that models nitrogen viscosity for the pressure and ...
1
vote
1answer
129 views

What does centre of lift depend on?

I've read in many places that centre of lift is about quarter chord of the wing and that post-stall lift (the part developed on lower surface) has centre midchord. The later makes sense; the pressure ...
1
vote
1answer
93 views

Constant mass flux in fluid dynamics?

OK so I am having a conceptual crisis about Hydrodynamics. 1) Since mass should be conserved, is $\frac{dm}{dt}=0$ ? 2) But I know that the formula $\rho_1u_1A_1 = \rho_2u_2A_2$ exists... and ...
1
vote
2answers
161 views

What is a good model for computing water dropping on a surface?

Before introducing my question I would like to outline the fact that I'm a coder, so I can be wrong when using some kind of terminology. What is a good model for computing the flow, the shape and all ...
1
vote
3answers
109 views

Can a very thin sheet of any material float inside a liquid?

When a body is immersed in a liquid,buoyancy is the net force of all the forces acting on it. Now the forces are equivalent to those which will act on the same volume of liquid.Rightly so,but ...
1
vote
0answers
78 views

What causes a whirlpool to form in a bathtub? [duplicate]

I mean, when you have a full bathtub and then let it empty, under what conditions does a whirlpool form? Could we devise an experiment and measure this effect? When it comes to fluids, I don't know ...
1
vote
0answers
43 views

Bulk transport of an aerosol by a blast wave

I'm trying to model the behaviour of aerosols in response to blast waves. (This is for visual effects.) Intuitively, if a flare left a smoke trail above a field and then a bomb detonated elsewhere ...
1
vote
1answer
271 views

Power in hydraulic analogy

In hydraulic analogy one compares electrical circuits with water circuits. For the electric case the formula $P = U \cdot I$ for the electric power holds. The analogous formula for water flow would ...
1
vote
1answer
144 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
1answer
384 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?
1
vote
2answers
1k 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 ...
0
votes
2answers
238 views

Direction of pressure in fluids

ok so my friend told me that in a container, the pressure exerted by the walls on the liquid in the container act in the upward direction.Is he correct ? so what I am imagining is a cylindrical ...
0
votes
2answers
390 views

What is the aperture in the hydraulic analogy of Ohm's law

Note: My question is duplicate of Why doesn't water come out of tap/faucet at high pressure when I turn it on?. None of the answers given there explains how the continuity equation fits properly. ...
0
votes
1answer
133 views

Viscosity of water in the presence of solutes

Some physical properties of water change in the presence of solutes: vapor pressure, boiling point, freezing point and osmotic pressure. In particular, these four properties are called colligative ...
0
votes
1answer
445 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
695 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
152 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 ...
-1
votes
2answers
943 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 ...
-2
votes
2answers
386 views

About how fast can a small fish swim before experiencing turbulent flow around its body? [closed]

About how fast can a small fish swim before experiencing turbulent flow around its body? An Engineering Problem! Please go through this question step by step. :D