[Nabu]

Hello everybody,

i'm using CFX 14.5.7 to simulate one stage of a centrifugal compressor. I used Turbogrid to mesh the impeller passage. Attached is the minimum errors that i could achieve playing with factors inside mesh data.

The simulation reached acceptable value for residual RMS error (less than 10^-4), but Yplus is more than 300.

Is there anyone who has suggestions or comments to improve Yplus result?
I did not use tip clearance on shroud because i saw that by introducing a clearance at shroud the errors in the mesh increase. But i would like to ask if is reasonable to model the clearance in the mesh and if someone has experience of meaningful results.

Thanks for any help!

[ghorrocks]

Do not simply assume that a big y+ means your simulation is bad. You should do a mesh sensitivity check and find out whether it is a problem or not.

And also do not assume your convergence is acceptable either. You should check that as well.

[krishna13j]

Hi Nabu,

I am doing a similar simulation and developed the mesh for a passage using Turbogrid but am stuck after the single passage analysis. I have completed the single passage analysis but my work requires to model a full stage centrifugal compressor. Can you please help me with this. Is this done in ICEM CFD or can it be doen directly in CFX-Pre.

Also, I have an inlet pipe geometry which I need to connect to the full stage mesh. Do I need to develop a united geometry in design modeller or would it be fine if I model it separately and then import it to CFX-pre after meshing in ANSYS meshing tool?

Thanks

[stephec1]

Is there by any chance that I can obtain the full Impeller in turbogrid instead of a single flow passage?
I am simulating flow through a pump when its operated in reverse and using a single blade wont be representative of the problem as the flow field might be different at any point of the volute given the changing shape of the volute and that why the need to obtain a complete impeller model.
Anyone with an idea of how to obtain that please your help is much appreciated..

Regards,

[ghorrocks]

Please start a new thread for a new question in future.

Can't you convert a single passage model into the full impeller simply by rotating it around? CFX-Pre has the capability to transform meshes easily, so you do not need to remesh, you can do it in CFX-Pre.