Why Do Poached Eggs Stay In The Center?

[bmarc92]

I cracked an egg into water and it sank implying the egg matter is average more dense than water.

If this is the case, a vortex should force the egg (when on the surface) off to the edges via the difference in centripetal force.

Why then does the egg stay in the center when the water is swirling?

 

[A.T.]

... it sank... .when on the surface...

So did is sink, or is it on the surface? Is the water being heated and stirred?

Since it is just slightly denser than water, other effects might play a greater role, like circulation due to heating and stirring.

 

[bmarc92]

So did is sink, or is it on the surface? Is the water being heated and stirred?

Since it is just slightly denser than water, other effects might play a greater role, like circulation due to heating and stirring.

When I first crack the egg and drop it in, it sinks.
I'm saying when you swirl water in a cylinder, there is a current flow: toward the surface, you have water forced toward the outer edge due to centripetal force. Water current runs down the cylinder edges and back up from the center. (First of all, if this is incorrect pls point it out because my point hinges on this)


What I'm asking is, mass_U235 < mass_U238. When they are put through a centrifuge, U₂₃₈ ends up on the outside which is filtered out leaving U₂₃₅ to be extracted. Point being denser objects end up on the outside.

Since ρ_egg > ρ_H2O, why does the poached egg remain in the center, it's heavier! it should make its way along the radial axis.

------------------------------------------

Say that the water wasn't heated, so no heat related effects, and the investigation has to do with the behavior of the egg when water is being stirred.

 

[Baluncore]

When you stir the water, there is a point in the centre where there is little flow. If the egg is not in that place, it will be induced to spin as it travels around with the flow, by the differential water speed, and it will have a Magnus effect lift, towards the centre, where it will be stable.
https://en.wikipedia.org/wiki/Magnus_effect

 

[bmarc92]

When you stir the water, there is a point in the centre where there is little flow. If the egg is not in that place, it will be induced to spin as it travels around with the flow, by the differential water speed, and it will have a Magnus effect lift, towards the centre, where it will be stable.
https://en.wikipedia.org/wiki/Magnus_effect

"Point in the center where there is little flow" <------ I don't understand the reason behind this premise. But even if I were to accept it, this implies that for this to be the reason behind the egg remaining in the center, in terms of force gradient, there must be a converge of force toward the center for this point to be a stable potential well. Where would this force convergence come from?

 

[Baluncore]

Do you stir the water around the egg?
If you stir water in a round container, the velocity is greater at the outer edge than at the centre, where the point is turning, not moving.
The body of the egg sits in a shear zone and therefore spins as it travels around, unless it reaches the centre.

 

[Hill]

If it is like in this video, it appears that the egg starts moving outwards but then the white touches the wall and the egg bounces.

 

[Motore]

So you mean how does the white not separate from the yolk? When poaching the egg? Or how the yolk is trapped in the middle and not flung to the side when water is stirred before hand?

 

[DaveC426913]

I have (er, had) 12 foot circular swimming pool. The pump keeps water circulating in a counter-clockwise direction. Anything a little heavier than water will be carried along by the gentle current until and unless it reaches the centre. At the centre, there is much less current, and the heavier debris always gathers there.

A circulating pool of water is not the same as a centrifuge. The primary driver in a centrifuge is centrifugal force, The primary driver in a (slowly) rotating pool of water is current flow.

 

[Drakkith]

I have (er, had) 12 foot circular swimming pool. The pump keeps water circulating in a counter-clockwise direction. Anything a little heavier than water will be carried along by the gentle current until and unless it reaches the centre. At the centre, there is much less current, and the heavier debris always gathers there.

My fiance and I utilize this method (albeit manually by creating the circular current ourselves when we first get in) to clean our pool. Everything moves towards the center and it makes very easy to clean! I've always wondered why this effect happens.

 

[Baluncore]

Everything moves towards the center and it makes very easy to clean! I've always wondered why this effect happens.

Tea leaves, at the bottom of the tea, move towards the middle of the cup when it is stirred. Which way do tea leaves that float move?

A drifting boat moves towards the middle of a river, and then moves faster than the water surface in the river. That is because the boat is sliding downhill, on the surface of the water.