[dinhanh]

Hello,

I am trying to implement the cavitation model such as Merkle model other than the default model in CFX. The model requires the liquid volume fraction at every calculation step to update the mass transfer rate. But I do not know how to access the variable phase volume faction in CFX-Expressions, when in the variable tab there are no phase volume fraction as in picture 1.

So in the expression that I defined: Vapor.Volume Fraction is pointed to volume fraction of vapor phase name as in picture 2.

Solution was diverged:

ERROR #001100279 has occurred in subroutine ErrAction. |
| Message: |
| Floating point exception: Overflow

An error has occurred in cfx5solve: |
| |
| The ANSYS CFX solver exited with return code 1. No results file |
| has been created.

So I think I were wrong to access the phase volume fraction. Does anyone know about this problem, please help me. Thank you very much!

[ghorrocks]

You are correctly accessing the volume fraction variable. It would give you a CEL error message if you were making an error there. Your problem is that your cavitation model is not numerically stable. This is not a surprise as cavitation models are highly numerically unstable at the best of times due to the massive variable gradients inherent in the model.

Before trying your own cavitation model on your own fluid, have you:
* Used the built in cavitation model using water and check that works
* Used the built in cavitation model using your fluid and check that works
* only then should you start introducing your own cavitation model with knowledge that everything else is working.

Depending on exactly what you are doing you may well have to some numerical stabilisation stuff - some introductory stuff is described in the FAQ: https://www.cfd-online.com/Wiki/Ansy...do_about_it.3F

[dinhanh]

Hi ghorrocks,

Thank you for your comments!

I will try as you suggest.