×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Pressure Drop through orifices in a rotating disk

Pressure Drop through orifices in a rotating disk

Pressure Drop through orifices in a rotating disk

(OP)
I have two volumes separated by a rotating disk spinning at ~8000 rpm with five 0.125" dia (0.200" long) holes in it.  They are machined in the disc at a diameter of 1.2".  I know how to calculate flow with a certain pressure drop through these orifices if they were static, but how do I account for the fact that they are spinning at 8000 rpm? Surely this would hinder the flow somewhat?
Thanks

RE: Pressure Drop through orifices in a rotating disk

Just my thought.
If I want to solve this problem, I'll changet it to a "static problem" with this assumption: rotating disc can be assumed a static "strainer". you can assume mesh size of this "strainer" based on dia and the number of holes as well as rpm of disc.Actually 8000 is pretty big and I think such assumption is not very wrong.

RE: Pressure Drop through orifices in a rotating disk

I think a pseudo-static strainer solution can work if the fluid is a gas.

If the fluid is a liquid, things could get interesting.  

E.g., absent rotation:
The upstream isobars are hemispheres, and
The upstream flows are radially in toward the apertures.
The downstream isobars are ... not hemisphers, and
The downstream flows are toroidal, outside of the hole centers bounded by the chamber walls and the stream exiting the apertures.

With rotation, all the flows are sheared, and the path length for a given unit volume could get quite large, depending on the extent to which the bulk fluid in the chambers rotates with the disk.

It should make a hell of a mixer.

Mike Halloran
Pembroke Pines, FL, USA

RE: Pressure Drop through orifices in a rotating disk

I would imagine it would be just horizontal flow from the near or in the film layer being sheared off and then blown through the hole.

BigInchworm-born in the trenches.
http://virtualpipeline.spaces.msn.com

RE: Pressure Drop through orifices in a rotating disk

What if the shear value is high enough to allow the disc to create drag against the contact area with the fluid?

Could the a vortex be created in the area local to the disc and then for the fluid to flow axially though the disc whilst rotating at the same speed as the disc?

Conversely...what if the shear is very low and the liquid local to the disc becomes very turbulent, effectively blocking any flow?

I can imagine either one happening...

What about centrifugal forces, could the liquid properties be effected?

Hydromech

RE: Pressure Drop through orifices in a rotating disk

(OP)
BTW, the fluid is jet fuel.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources