[Kalybre]

Hello,

I have work with Ansys but not too much with CFX. I am having a problem with a centrifugal pump. I think my problem is due to the boundary conditions or perhaps the interface, I am not sure. I have check the rest of the thread but I couldn't find an answer and the tutorial is only for an impeller, not for a complete pump.

I describe my set up in the enclosed file.


All advise is grateful

[ghorrocks]

The document is not readable. Please do not post it on links, just post it on the forum.

[filippogalli]

From my point of view there are two errors:

- For the impeller define the rotation as "Domain motion: rotating" and not as "Rotating Wall"
- Domain Interface: Interface Model-Frame Change/Mixing Model: here you have to use either Stage or Frozen Rotor otherwise this can not work.

[Kalybre]

Originally Posted by filippogalli

From my point of view there are two errors:

- For the impeller define the rotation as "Domain motion: rotating" and not as "Rotating Wall"
- Domain Interface: Interface Model-Frame Change/Mixing Model: here you have to use either Stage or Frozen Rotor otherwise this can not work.

For the impeller I only have the options:
- No slip wall (this is the only that allow add rotary velocity)
- Free slip wall
- Specific shear

Perhaps I should define the DEFAULT DOMAIN rotating?

[filippogalli]

I don't understand what your default domain is!

You should define different domains for each component (impeller, volute, inlet pipe) and then define the stationary domains as stationary (volute and inlet pipe) and the rotating domain (runner) as rotating with your RPM set and the no slip wall condition for hub, shroud and blades.

If you do this right the default domain will disappear as it normal contains only parts that have not defined in another domain.

[Kalybre]

Originally Posted by filippogalli

I don't understand what your default domain is!

You should define different domains for each component (impeller, volute, inlet pipe) and then define the stationary domains as stationary (volute and inlet pipe) and the rotating domain (runner) as rotating with your RPM set and the no slip wall condition for hub, shroud and blades.

If you do this right the default domain will disappear as it normal contains only parts that have not defined in another domain.

Yes, you were right, I had defined the impeller like sub-domain, for that I didn't have th options that you told me.

Now I have defined 3 different domains: 2 stationary and one rotating (impeller).
The Domain interface: Frame Change/Mixing Model : Frozen Rotor ( y tried with stage too), between : Inlet pipe - impeller & impeller - Casing.
With these should work, but I have obtained the results on the enclosed picture.

Why the impeller is stationary? I can't understand it.

[ghorrocks]

Have you read the documentation about rotating frames of reference? There are many different ways of doing this - you need to understand the assumptions behind the models to understand the results.

[billy7590]

I am having similar issues.
When I use frozen rotor interface, CFX asks for pitch setting as well. My inlet pipe side of interface has a different mesh than the mesh on impeller side of interface. Does that have an adverse effect ??