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

learn more… | top users | synonyms (1)

3
votes
1answer
236 views

Fluid Dynamics: Bernoulli Air Tunnel

I have the following question as part of a lab intro to explain the more complicated stuff I'l actually have to submit in the lab. I put all the questions here just to show my thought pattern/what ...
2
votes
1answer
782 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 ...
1
vote
2answers
287 views

Water and superconductors

If you have seen my previous questions then this may make better sense. If you put an insanely powerful superconducter on the outside layer of a ROV that is underwater, would it form an outer layer ...
3
votes
1answer
316 views

Tear drop shape

i heard that a tear drop shap is the most aerodynamic shape possible or the best is this true? If this isn't true what is since i need to make a fast ROV? Also since i need to have a propeller to ...
2
votes
3answers
215 views

can Superconductivity be used to repel water?

Can water be repeled with the force from superconductivity gathering current on the surface cuased by Faraday law of induction? I'm trying to make a ROV that can run underwater that uses ...
4
votes
1answer
101 views

Superconductors and electrical fields

I have been looking around to figure out how superconductors are made. What ways are there to create a superconductor that don't involve a coolant like liquid nitrogen? Is it possible to cause a ...
3
votes
1answer
706 views

Air flow coming out of a fan feels much stronger than air flow coming in. Why? [duplicate]

Possible Duplicate: Why is exhaling more forceful than inhaling? If I put my hand behind my computer's system block, I can feel a very strong flux of air coming out, as it is being pushed ...
3
votes
1answer
411 views

What is the formula for the glug point?

When you pour water out of a bottle, normally you have a smooth stream. However, if you pour it too fast it glugs, which is to say, comes out in quantized bursts. What is the formula for calculating ...
2
votes
2answers
344 views

Air drag coefficient value

Is there any equation that calculates the $C_d$ value in the formula of air drag ? $$F_d = \rho C_d v^2 A$$ I have found that there are tables for this constant but I am looking for the equation that ...
0
votes
1answer
553 views

How does a table fan work?

In a table fan, the blades move around in circular way and we feel air/wind when sitting on front of it. How does this happen?
1
vote
1answer
270 views

Vertical Motion in Air + Density [closed]

I am having trouble with this confusing question. Please help. The fastest recorded skydive was by an Air Force officer who jumped from a helium balloon at an elevation of 103000 ft, three times ...
6
votes
2answers
427 views

Analogue of Princeton Companion to Mathematics for Physics?

I would like to know if there are compendiums much like the Princeton Companion to Mathematics for physics (especially classical physics: fluid mechanics, elasticity theory, Hamiltonian formalism of ...
19
votes
4answers
2k views

Have we figured out how to analyze turbulent fluids?

I was surprised to read that we don't know how to analyze turbulent fluids. On page 3-9 of The Feynman Lectures on Physics (Volume One), Feynman writes: Finally, there is a physical problem that ...
1
vote
1answer
186 views

Surface Tension of a Liquid - When a liquid body is acclerating

As far as I understand it (which admittedly isn't very far), surface tension forces are made up by the tension-attractive forces of molecules at the liquid-gas/vacuum interface, such as those between ...
8
votes
5answers
423 views

What can wavy patterned sand tell about the Fluid that formed it?

Sand on the bottom of the ocean as well as sand on the low-tide beach often forms wavy patterns. Do the parameters of these wavy patterns have any relation to the water and waves that formed them? If ...
3
votes
1answer
102 views

Jupiter: Zonal Jets in opposite directions

I recently read that the Great Red Spot arises from the shear instability of zonal flow from zonal jets travelling in opposite directions. Is there any reason why such zonal jets travel in opposite ...
3
votes
0answers
211 views

Flow behind a plate causes pressure drop?

I've done an experiment where we direct an air jet from a fan onto a set of electronic scales. By measuring the velocity of the air jet at the exit of the fan nozzle, and applying the conservation of ...
0
votes
1answer
288 views

Fluid Mechanics Problem - Ball in Reservoir

I'm having a problem starting and solving the following problem: My attempt at the solution was to realize you need to balance the upward forces with those of the downward forces in which case you ...
4
votes
3answers
889 views

Water under high pressure

If you were to sink a container to the bottom of a deep ocean and seal it there, then bring it up to the surface, would it retain its pressure? The answer for a gas is obviously yes, but what about ...
-1
votes
1answer
155 views

Behaviour of liquid in vaccume

Is it possible for a liquid to exist in a high quality vacuume? For example, a few Torr. If so what are the methods for doing this?
17
votes
4answers
525 views

Why does the fundamental mode of a recorder disappear when you blow harder?

I have a simple recorder, like this: When I cover all the holes and blow gently, it blows at about 550 Hz, but when I blow more forcefully, it jumps an octave and blows 1100 Hz. What's the ...
4
votes
1answer
401 views

Fluid Mechanics from a variational principle

It is posible to define a good variational principle to describe Fluid Mechanics? if so, wath is the correct tratement of the issue. I guess something like: $I=\int d^4x (\frac{1}{2}\rho v^2-P-\rho g ...
6
votes
2answers
420 views

Given a terrain, how to draw the stream flow path?

Assuming I have a terrain, as usual the terrain has ridges, creeks and all the characteristics that you can find on a real life map. Water flows from the top of the mountain into lower area, the path ...
6
votes
2answers
525 views

Surface tension of solutions and mixtures

The inspiration for this question is over on cooking.stackexchange, asking more about actual measurements for commonly consumed liquids, but I'm interested more generally as well. What determines the ...
3
votes
2answers
847 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 ...
0
votes
1answer
2k views

Streamlines & Pathlines Problem

I have a 2D flow velocity field $\bar{V} = y^2\hat{i} + 2\hat{j}$. I'd like to find the equations for the streamlines and pathlines. Since $\bar{V}$ has 0 time derivative, the flow is steady, and so ...
0
votes
1answer
168 views

Filtering and extracting turbulent data from instantaneous dataset

I have collected data on flow velocity at 1 Hz sampling rate for 25 hours using a high resolution acoustic Doppler current profiler (HR-ADCP). how I can decide up to which period is the mean ...
2
votes
2answers
235 views

pressure exerted by fluid

If I had a flexible tube sealed at both ends and I submerged it in water (held vertical) Would the bottom half of the tube compress and the top half expand? What would the pressure in the tube be? Say ...
6
votes
1answer
456 views

Spin-up time for fluid in an open cylinder with no endwalls?

I'm interested in how quickly (if at all) the fluid in an open cylinder would reach solid-body rotation if the cylinder is suspended vertically in an unbounded fluid. I've found plenty of work that ...
9
votes
3answers
197 views

What does the quantification of causes and effect look like, for clouds in offshore wind turbine wakes?

At Horns Rev windfarm off the coast of Denmark, sometimes in winter, clouds appears in the wake of the turbines. I've only seen photos of the phenomenon when the wind direction is exactly aligned with ...
4
votes
1answer
621 views

Can I measure the Reynolds number or the heat transfer coefficient

Suppose I have a flow of hot air around a cold and unevenly shaped object with holes and tunnels (think about it as a bed packed with some objects). I would like to know the Reynolds number of this ...
3
votes
1answer
178 views

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, ...
8
votes
1answer
492 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 $k=\frac{2\pi}{r}$ ...
4
votes
2answers
166 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. ...
8
votes
1answer
660 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 ...
7
votes
4answers
3k 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 ...
1
vote
2answers
205 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?
1
vote
2answers
255 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 ...
2
votes
2answers
894 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 ...
1
vote
1answer
6k 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 ...
2
votes
1answer
440 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 ...
1
vote
1answer
177 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? ...
6
votes
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 ...
2
votes
2answers
437 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 ...
24
votes
3answers
1k 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 ...
5
votes
2answers
211 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 ...
1
vote
1answer
2k 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 ...
0
votes
1answer
516 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 ...
23
votes
3answers
1k 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 ...
4
votes
2answers
383 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 ...