[zhubohong]

Hello, everyone! Here I want to ask some questions as the tittle shows.

ANSYS CFX just has three drag models, Schiller, Ishii and Grace, but I want to investigate the effect of other models, such as Kuo, Kolev and Morsi, on my gas-liquid flow simulation. So, it means I should input the drag coeffient using the Expression. However, I met some problems.

Firstly, the drag coeffients of models are all related to Reynolds Number(Re). I checked the CFX Reference Guide and found out a parameter, Slip Re. The Guide defines this as that "Reynolds Number for Eulerian multiphase fluid pairs"
I tried to re-define the Schiller Naumann model by myself for comparing the existed one. My Expressions is "if((slip Re)<1000,(24/(slip Re))*(1+0.15*(slip Re)^0.687),0.44)“, but after I input it in "drag coeffients", the system showed a error that "MOMENTUM TRANSFER/DRAG FORCE does not have a required fluid pair prefix". I don't know how to solve it.

And, some drag coeffients are also related to Eotovos number and Weber number, but I didn't find them in CFX Reference Guide. So, how to define them in Expression?

Thanks for your time!

[ghorrocks]

Eotovos and Weber number - just define a CEL expression to calculate it.

The CEL error just sounds like you need to get the variable name right. I suspect it might be that you need to specify which fluid pair you are talking about - you can have more than one fluid pair. Look in the CFX reference manual for available variables and the correct way of referring to them.

[zhubohong]

Originally Posted by ghorrocks

Eotovos and Weber number - just define a CEL expression to calculate it.

The CEL error just sounds like you need to get the variable name right. I suspect it might be that you need to specify which fluid pair you are talking about - you can have more than one fluid pair. Look in the CFX reference manual for available variables and the correct way of referring to them.

Thanks for your reply. I tried to solve the problem. If I just used the "slip Re", the report showed that "does not have a required fluid pair prefix". if I used the "air.slip Re or water.slip Re", the report showed that "it is not allowed to have a phase". So, it seems I need to define the "slip Re" as like "air|water.slip Re". But the "air|water.slip Re" is a wrong expression. Yesterday, I checked the CFX reference guide, but I still find the way to define it. Few of information is explained about the fluid pair.