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# Simulation CFD

#### hydrostatic thrust bearing problem

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03/07/2018 10:51 AM

Hi,

Im trying to do simulation of hydrostatic thrust bearing, couse I want to have a pressure distribution and component velocities in the gap. So I've created a 2d model of fluid in SimStudio which is cross-section of half 3d disk model. I do not upload screenshot/image becouse it is "simple" rectangle.

I only know pressure boundary conditions, so I set up 0 Pa on the outlet and 1 MPa on the inlet (both static, gage). Flow is incompressible and laminar. Solver only sees 2 outlets and 0 inlets, is it good? And I think results of velocities are bad (for example: non-zero Vx - velocity near the wall). So its my first problem.

My second problem is setting a rotation speed to upper edge (simulation of rotating shaft) Is it possible in 2d model? I've tried by changing material to "rotational..." but solver shows 0 mass error. Next I've tried by adding (angular) motion to solid, so I edited model by adding second rectangular above "old one", and set up 100rpm. In results I have constant flow velocity along bearing radius (along edge)...

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#### Re: hydrostatic thrust bearing problem

03/07/2018 11:59 AM

Hello and welcome :)

Let me help.

1) It is OK that CFD is saying 2 outlets, it simply sees pressure as outlet and flow rate as an inlet. In this case I would ignore the line ;)

2) This one I cannot answer yet, CFD would always have a v=0 on a wall unless the boundary layer was removed?

3) Not sure you can do this as it breaks the whole 2D idea. How about a thin section in 3D with periodic conditions so that any flow exiting at the side, re-enters on the other?!

I hope this helps :)

Jon

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#### Re: hydrostatic thrust bearing problem

03/08/2018 2:44 PM

Thanks for reply :)

I've created thin model in 3d with the same pressure boundary conditions as in 2d. Now I have model with "gap" dimentions (mm) [800,10,0.1] and results of velocities are good :)

Can I use a motion tab to set up a rotational move? I will leave a "flow driven" unchecked and set up axis on 0,1,0. Center of rotation will be [-200,10,0] couse shaft diameter is 2000mm. I'll try upload some screenshots later if it necessarily.

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