Fluid under centrifugal force (Basic)

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Discussion Overview

The discussion revolves around the behavior of fluid in a cylinder that is spun around its central axis, with a focus on the effects of rotation and the potential influence of air or atmospheric pressure. The conversation explores both theoretical and practical implications of fluid dynamics in this context.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • Some participants propose that the shape of the fluid surface will approach that of a paraboloid of revolution depending on the rotation speed of the cylinder.
  • One participant clarifies that the discussion pertains to a rolling cylinder, suggesting that the direction of motion may influence the fluid behavior.
  • Another participant raises a question about whether the shape of the fluid surface might be a catenary instead of a parabola, expressing uncertainty about this claim.
  • It is noted that the shape of the fluid surface could still be a paraboloid even in a vacuum, challenging the necessity of atmospheric pressure for this outcome.
  • One participant references a textbook, "Transport Phenomena," to support the claim about the fluid surface shape under atmospheric pressure.

Areas of Agreement / Disagreement

Participants express differing views on the shape of the fluid surface, with some supporting the paraboloid model and others suggesting a catenary shape. The necessity of atmospheric pressure for the fluid behavior remains a point of contention.

Contextual Notes

There are unresolved assumptions regarding the conditions under which the fluid behavior is analyzed, including the effects of rolling motion and the presence of air or vacuum.

alexsb92
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Hi,

What happens to the fluid in a cylinder that is spinned around it's central axis? Would it matter if there would be a bit of air?

Thanks very much,
Alex
 
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Depending on how fast you rotate the cylinder, the shape of the surface will approach that of a paraboloid of revolution.

Thanks
Matt
 
Hey,

Thanks for the info, but i think i was a bit unclear, as I was meaning that the cylinder is rolling. Forgot that the direction of it will make a difference.

Any ideas about that?
 
I don't have the math to back this up, but something's nagging at the back of my head to suggest you're more likely to get a catenary rather than a parabola. I Could be totally wrong on this... Anyone know for sure?
 
Check out "Transport Phenomena" by Bird, Stewart, and Lightfoot.

If the fluid surface is exposed to atmospheric pressure (14.696 psi) then the shape will be a paraboloid of revolution.

Thanks
Matt
 
Why the need for atmospheric pressure? A fluid spun in a rotationally will form a parabola in a vacuum, why is this necessary for the rolling cylinder?
 
Yes, a fluid under vacuum will produce the same result. I was just stating the conditions used in the Transport Phenomena book for clarity.

Thanks
Matt
 

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