# Obtaining force results for rotating frame motion

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July 17, 2018, 12:44
Obtaining force results for rotating frame motion
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Ben Coles
Join Date: Jul 2018
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Hello,

I am in the process of learning to use Fluent and I’m currently working on a project that involves a hanging, rotating pipe with two spray nozzles that eject a liquid. I’m trying to determine the centrifugal force on the axis of rotation for given flow rates and rotational speeds but I’m not sure that I’m looking in the right place for this information.

I have two screen shots, one showing 60rpm rotation and the other showing 120rpm. Liquid travels down the vertical tube and then out the ends (the lower valve is shown closed in these images). I want to know what is the total force that the liquid puts on the axis as this rotates, and how does this force change as we increase speed and/or flow rate. I can play with all these variables, but am I looking in the right place for the net force reacted back to the axis of rotation due to pressure created during rotation? ie. net centrifugal force? (I’m looking at the yellow highlighted box at the bottom…)

When there is no rotation, the ejected liquid produces a thrust that pushes against the axis of rotation, but as rotation begins, and increases, the system crosses a breakeven point where the thrust from the liquid is equal to the centrifugal force of the rotating liquid and its inherent pressure gradient. I’m concerned with what happens above this point for bearing design considerations.

Any help greatly appreciated. Thanks
Attached Images
 60.jpg (121.4 KB, 8 views) 120.jpg (120.6 KB, 6 views)

Last edited by benclimbing; July 18, 2018 at 12:15.

 Tags centrifugal, centripetal, rotate, rotating, rotation