# Fluid under centrifugal force (Basic)

1. Sep 14, 2009

### alexsb92

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

Last edited: Sep 14, 2009
2. Sep 14, 2009

### CFDFEAGURU

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

Thanks
Matt

3. Sep 14, 2009

### alexsb92

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.

4. Sep 15, 2009

### mjcguest

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?

5. Sep 16, 2009

### CFDFEAGURU

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

6. Sep 16, 2009

### mjcguest

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?

7. Sep 17, 2009

### CFDFEAGURU

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