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64
votes
2answers
8k views

Why do chimneys have these spiral “wings”?

While walking around I noticed something very peculiar. Many chimneys had spiral "wings", while others didn't. I came up with two possibilities: The wind circles around the chimney upwards which ...
27
votes
3answers
4k views

Emptying a bottle faster by swirl

A moment ago, I was emptying bottles filled with water (2 liters) that are on the terrace of my house. As I did so I remembered something I saw on TV a some time ago (I don't remember when or where or ...
18
votes
3answers
940 views

How to show that the Coriolis effect is irrelevant for the whirl/vortex in the sink/bathtub?

There is a common myth that water flowing out from a sink should rotate in direction governed by on which hemisphere we are; this is shown false in many household experiments, but how to show it ...
14
votes
8answers
6k 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.
13
votes
6answers
32k views

Can magnetic fields be redirected and focused at one point?

I know that magnetic fields can be redirected, but... given a situation where you have static magnetic field over a large area, and you want to quickly change the magnetic field strength. Is it ...
9
votes
2answers
1k views

Why do co-rotating vortices coalesce, but not counter-rotating ones?

In studying the aerodynamics of modern aircraft equipped with high-lift devices, I have discovered that quite a number of distinct trailing vortices are present in the immediate wake of an airplane in ...
9
votes
2answers
441 views

The optics of vortex (in water): why there is a bright ring?

This picture is from this YouTube video from "Physics Girl", which shows how you can generate vortices in a swimming pool by using a plate: And there she explains the creation of the shaded circle ...
9
votes
4answers
4k views

How can I understand a Vortex Tube and its efficiency?

A Vortex Tube takes a pressurized input stream, most typically of a gas, and creates two output streams with a temperature differential. Apparently, it has been described as a Maxwell's Demon. Both ...
8
votes
2answers
11k views

How do you calculate vortex shedding frequency?

I am attempting to try to find out if there is any effect of Von Karman vortices on a group of wind speed readings where it is presumed that due to a mountain nearby the data collection spot Von ...
8
votes
2answers
959 views

Why water in the sink follow a curved path?

When you fill the sink with water and then allow the water to be drained, the water forms a vortex.. And then it starts to follow a curved path downwards by effects of gravity.. Why this phenomena ...
8
votes
1answer
290 views

How deep can a whirlpool descend?

My question is based around comparing the physics of a tornado against, what I imagine/assume to be the marine equivalent of a tornado, that is a whirlpool located either at sea, in a tidal region or ...
8
votes
1answer
509 views

Could the phenomenon of vortex bursting be exploited to reduce wake turbulence?

One of the classic stories in the annals of aerospace engineering is the development (and subsequent redesign) of the F-18 and its Leading Edge Extensions (LEX) due to fatigue problems, problems that ...
6
votes
1answer
3k views

What is a Physically Accurate Explanation for the Kutta Condition?

Countless arguments between highly intelligent people have been waged (on this very site in fact) as to exactly how lift can be explained in an experimentally and mathematically rigorous way. Taking ...
6
votes
1answer
628 views

How to calculate strength of wind speed in a von Karman vortex?

I am working on a project involving Von Karman vortices coming off of a mountain. I was able to calculate the shedding frequency (thanks to tpg2114 in a prior question), but now find it necessary to ...
5
votes
1answer
182 views

What's the corresponding symmetry of enstrophy conservation?

In fluid mechanics, especially 2D turbulence study, people talk about conservation of enstrophy. But I can't really understand enstrophy very well, and what's the corresponding symmetry of enstrophy ...
5
votes
1answer
288 views

Effect of rotation on turbulence threshold for Reynolds number?

If the significance of the Reynolds number is: Then what is the effect of angular momentum on the transition from laminar to turbulent as in a convective vortex? Waterspouts, in particular, seem ...
5
votes
3answers
3k views

When is a flow vortex free?

To solve problems in fluid dynamics one states often the assumption that the flow is vortex free i.e. $rot(u) = 0$ It is a basic assumption which is needed for potential flow problems etc.. My ...
5
votes
3answers
462 views

Why do tropical cyclones not tear themselves apart?

A tropical cyclone is the generic term for a hurricane, typhoon, or tropical storm. Tropical cyclones derive their energy from evaporation of water at the ocean surface which ultimately recondenses ...
5
votes
2answers
283 views

Does vortex shedding exist along the surface of an object?

Vortex shedding occurs due to the detachment of flow. The typical example is for the oscillating wake behind a cylinder, and has a frequency related to the size of the object. I want to know, if a ...
5
votes
1answer
126 views

Do vortex tubes work with a reversed end plug?

Would a vortex tube still work if instead of a cone plugged into the 'hot' end you had a smaller hole on the 'cold' end? As I understand it, the point of the cone on the hot end is to only allow the ...
4
votes
2answers
4k views

Frequency of Vortex Shedding

Suppose we have a long cylinder with diameter $D$, then we move it parallel to its axis with a velocity $V$ in a medium such that the Reynolds number of the flow is in the range $250<R_e<2\...
4
votes
3answers
2k views

Why does the tea in the middle of the cup spin faster when I stir it?

Try this: Make a cup of tea, add sugar, and stir it. Now add some milk, while it's still spinning. What I noticed is that the milk appears to move around a lot quicker in the middle of the cup of ...
4
votes
2answers
124 views

Destroying currents in superconducting rings by vortex tunneling

Consider a superconducting metal ring in which there is a persisting current $I$. I am interested in the failure of this current to remain "persisting" in the ring, although this will occur at ...
4
votes
1answer
2k views

how to determine if a vortex is laminar or turbulent

In a cylindrical chamber with a high diameter-to-height ratio; a fluid is tangentially injected. there is an axial exit to the cylinder. how do I determine if the vortex so formed is laminar or ...
4
votes
2answers
562 views

Why does the vortex form in the von Karman Vortex Street?

Why does the vortex form in the von Karman Vortex Street? So far I have this for the reasoning: 'It occurs when a fluid flows around a cylindrical object. The pressure on a fluid particle rises to ...
4
votes
1answer
125 views

How to relate wingtips vortices with the energy loss it engenders?

On planes, wingtips vortices engender a loss in terms of lift, and an incresed of the drag, so an energy loss. Is there any possibilty to find a mathematical model relating both ? Thanks for the help.
4
votes
0answers
91 views

What is the relationship between the angular speed and the diameter of the eye of a water vortex?

In a water vortex formed in a plastic bottle, what is the relationship between the angular speed of the water and the diameter of the hole in the cap? I would have expected that according to the ...
3
votes
2answers
35 views

Prevention of fluid vortex formation

I've been looking for a way to prevent Vortex (whirlpool) formation in a pressurized vessel as it drains, but I am not having any luck finding the parameters at which vortex formation occurs. Is there ...
3
votes
3answers
252 views

Explain Turbulence [closed]

I'm a high school student. I still don't understand what turbulence is. Please can you explain what it really is? This is what I think it is: rotating motion of water when a particle travels at a ...
3
votes
1answer
83 views

Physical intuition for Lamb vector

In many aerodynamical descriptions involving vortex structures (e.g. the Crocco's theorem) there is a useful physical quantity called Lamb vector: $$ \vec{\omega} \times \vec{v} $$ where $\vec{\...
3
votes
1answer
456 views

Do communicating vessels work when water is moving?

I want to know if the water level equalize in communicating vessels, when in one of the vessels there is a vortex, or any other water movement, and if the level does equalize, what will be the level? ...
3
votes
2answers
1k views

Vortex street and Reynolds number

Its been stated in Wikipedia regarding Reynolds number(Re) that "laminar flow occurs when Re<2300 and turbulent flow occurs when Re>4000. In another wiki file related to Kármán vortex street it has ...
3
votes
1answer
302 views

What is the relation between vortex and quantized magnetic flux in superconductor?

A vortex is a topological defect of the order parameter. As far as I am concerned, I think a vortex is a phase singularity point and a vortex always has a quantized flux. And we know that the magnetic ...
3
votes
0answers
45 views

Calculation of Berry's phase due to monopole tunneling event of $O(3)$ NLSM on square lattice

I am currently reading the seminal paper by Duncan Haldane: http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.61.1029 In this paper, he asserts that for a unit-vector field $\hat{\Omega}(x,y,t)...
3
votes
1answer
141 views

Is it possible to generate one half of a Karman Vortex Street?

The Karman Vortex Street is a type of phenomenon which is generally illustrated by examples in which a long, solid, smooth circular cylinder moves at constant velocity through a fluid. The long axis ...
3
votes
0answers
157 views

seemingly impossible query

While on an expedition to a lake, it was noticed that the wind speeds gusted violently in seemingly periodic wakes and the proposed explanation was Von Karman vortex shedding off of nearby mountains ...
2
votes
2answers
117 views

Could galactic rotation be similar to an irrotational vortex?

Could black holes' near light speed rotation cause galaxies to move like an irrotational vortices?
2
votes
1answer
680 views

Vortex Air Intake

Why is a vortex air intake in an engine cause the fuel to burn more efficiently within a vehicle. Why is this more efficient.
2
votes
2answers
167 views

Nomenclature clarification concerning solitons

My experience with solitons is restricted to the classical setting, namely solutions to the quartic interaction $\phi^4$, the Sine-Gordon equation, and Korteweg–de Vries equations. I was explicit to ...
2
votes
1answer
196 views

Whirlwind/tornado/dust devil in the middle of nowhere

I live in area which have many properties similar to desert. Many times when I drive by I see a whirlwind/tornado/dust devil of sand or other garbage parts. I would like to ask how this was normally ...
2
votes
1answer
93 views

What is the physical basis of the $\rho \bf{u} \times \bf{\omega}$ force on a fluid vortex line?

In fluid dynamics, the force density on a vortex line is $\bf{f} = \rho \bf{u} \times \bf{\omega}$. In Faber, Fluid Dynamics for Physicists, ch. 4, this is "derived" by analogy with magnetostatics, ...
2
votes
1answer
354 views

Velocity field induced by vortex points along ellipse

I'm investigating the velocity field induced by a continuous distribution of 2D vortex points distributed along an ellipse $\{a\cos\theta,b\sin\theta\}$. I'm interested in the field inside the ellipse,...
2
votes
1answer
109 views

Physical intuition on vortex sound generation

Whenever a fluid has a nonzero vorticity, it looses some of its energy in a form of sound wave. Formally is this mechanism described by Lighthill's equation or some related model (like e.g. Curle's ...
2
votes
1answer
395 views

Complex valued energy

I'm working on a 2D He superfluid system with vortices. I was asked to calculate the kinetic energy of vortex-(anti-)vortex pairs and compare the two situations. One finds in literature that the ...
2
votes
1answer
103 views

Does a whirlpool(vortex in water) continue in air(vortex in air),and when does a vortex stop?

First part: The question is both about the continuity of the water vortex(whirlpool) to vortex in air in time and in space. About continuity in time,does the vortex of the water slowly produce a ...
2
votes
0answers
29 views

Why do vortices scatter at right-angles

I have been taking a course on non-perturbative physics and currently the teacher is away so I cannot ask him. In the lectures, he made the claim that a pair of vortices in the abelian-Higgs model ...
2
votes
0answers
44 views

Angular momentum transfer in a bottle vortex

A colleague and I were discussing the following fluid mechanics experiment, which most people have probably tried in their kitchen: take a bottle full of water (a 2-litre transparent soda pop bottle ...
2
votes
0answers
27 views

Formation of vortices in superconductors

So I'm trying to understand how mixed state of a type II superconductor becomes the energetically favourable state. I've been through a simple approximate calculation considering a S-N boundary to ...
2
votes
1answer
101 views

What does “downshear” mean?

I occasionally read descriptions such as "downshear of the vortex" in meteorological publications. What does this mean?
2
votes
1answer
131 views

Vortex shedding

So I was reading about vortex shedding, and got to know that it causes the building to resonate. Is there any way to use this resonance to generate electricity (maybe use quartz?) I am trying to make ...