Problem with humid vapour
 

Hi everybody,

I have a big problem with CFX, trying to simulate an axial turbine with humid vapour.
The run goes ok for all the time expect when it stops ans try to save di res file.

The error/notice the comes up from the Out file is the following (as example):

+--------------------------------------------------------------------+
| ****** Notice ****** |
| While evaluating |
| H2O gas.Saturation Entropy |
| on domain "Rotore", |
| the variable |
| Absolute Pressure |
| went outside of its lower limit. Its minimum value was |
| -6.4313E+02. The bounds error was handled by clipping. |
| If this situation persists, consider increasing the table range. |
+--------------------------------------------------------------------+

...and also....


+--------------------------------------------------------------------+
| ****** Notice ****** |
| Newtons method failed to converge in 150 iterations. This |
| occurred while computing the following variable: |
| |
| Variable Name : Total Pressure in Rel Frame |
| Location Name : Rotore |
| Mesh location : VERTICES |
| Mesh entity : |
| Last 3 Changes : 1.99515E+01 1.97666E+01 1.97794E+01 |
| Tolerance : 1.0000E+00 |
| |
| The Newton iteration was diverging. The solver will continue |
| with the variable field as it was on the final iteration. If |
| this situation continues you might try decreasing the Newton |
| iteration under relaxation factor. This can be changed by |
| setting one of the following parameters: |
| |
| Temperature : "Constitutive Relation Under Relaxation" |
| Pressure : "Newton Pressure Under Relaxation" |
| |
| for your mixture using the command file editor. |
+--------------------------------------------------------------------+



What is this stuff? How can I fix this problem?
The consequence is that the run takes a huge amount of time to save and stop.


Please Help!!!!!

These warnings have nothing to do with the time it takes to save the res file.

The first error is saying that it has exceeded a limit on the saturation entropy table. If this worries you, you should do as it says and extend the range. But note this is just a warning, you can ignore it and proceed if you like.

The second error is saying it is having a hard time converging. The Newton iteration warnings normally occur when you have a complex material model. Check your material model is OK, but other than that the normal approach is to improve numerical stability using the standard techniques described here: https://www.cfd-online.com/Wiki/Ansy...do_about_it.3F