Learning Forum

[vmbraga]

Greetings,

 

In Fluent theory guide I found the following information:

 

"For the phases with multiple species, the phase shares the same pressure as the other phases, but each species has its own pressure (that is, partial pressure). As a result, the vapor density and the pressure used in Equation 17–488 are the partial density and pressure of the vapor."

 

In my case, I have a liquid phase with two species, and a vapour phase with only one species. I am using the Zwart, Gerber and Belamri cavitation model. For this model, how will the solver calculate the mass transfer? Is there any change in Equation 17-493 (see attachment)? If so, how to calculate the mentioned partial pressure and partial density?

 

Thank you for your consideration.

Regards,

 

Vitor

 

 

 

[DrAmine]

This just affects the gas phase. The gas phase in your case is made of one specie so the phase pressure is shared among the phases and equal to the partial pressure.

[vmbraga]

Dear Amine, thank you very much for your help. So, how does the solver calculate the partial pressure for the Zwart, Gerber and Belamri (ZGB) model?

I ask this because I'm using a UDF to replicate the ZGB model (my UDF is just a copy of the UDF available in the Fluent Customization Guide in the LINEARIZED_MASS_TRANSFER section). When I use this UDF for a single specie case (single specie liquid phase and single specie gas phase), the results of the UDF are identical to the results of the ZGB model implemented in Fluent, as expected.

However, when I use my UDF for the case with the two-species liquid phase, the results are different. My UDF overestimates the mass transfer when compared to the ZGB model implemented in Fluent. I'm trying to figure out why this happens, what changes in the Equation that I've attached in my previous message.

 

 

[DrAmine]

First of all, we do not download attachments.

Second, we do not comment on user defined settings/models. We just provide guidelines. The example in the manual is according to Zwart et al.  

What I can tell: You said you gas phase is one specie-phase so the pressure used here is the same pressure used by all phases.

You can now make a comparison between the built-in and the example from customization manual (actually the same). If you see a difference try reaching the ASC who can (if possible) reach the local support.

[vmbraga]

Ok, thank you again, Amine. 

BR,

Vitor

[DrAmine]

Welcome Viktor.