1. I am simulating a closed tank(cylindrical) in which liquid cryogen is partially filled.when heat flux is applied on the walls, natural convection occurs and evaporation takes place at the interface. For this problem, what model is suitable in multiphase models. i think any one we have to use UDF.

2. how to calculate amount of each phase in a zone, in axisymmetric model. i.e. each amount of vapor and liquid in post processing. i tried with define custom-functions and reporting it in surfacce integrals. it showed different value for 3d and axisymmetric model. i used 'density-liq*VOF-liq*cell-volume'for custom function.

I will appreciate ur help. Prasanth

Hi!

You should use VoF multiphase model. For heat and mass transfer you can write an udf. It is only possible in Fluent 6.1! I think you can find an example for that kind of udf in udf manual (fluent 6.1).

For the ammount of each phase you should write a costum function as "density-liq*VOF-liq" - volume is allready incuded in VOF macro (VOF - vapour fraction)...actually im not shure about this (it still very early in the morning) - think about it

Good luck

MATEUS

Hi Mateus, I am already using VOF model itself. But when I enguired Fluent people, they were not sure and telling that VOF shouldnot be used and mixture model should be used. So i got puzzled and had put a question here. thanks for ur reply. regarding UDF, there aren't suitable example. there are so many conditions to be considered such as vapor pressure, saturation temp, enthalpy at the interface etc. any way, thanks for ur reply --prasanth

hi,

For the phase change problem like this, better to use mixture model. U have to write UDF with 3 source term.. 1. Mass source term for the vapor.

2. Mass sink term for the liquid. and

3. Energy source term ( For the pahse change)..

If u acn mail me, I can send u a sample UDF.

BFN

Mahesh

HI I did mail to your id. Thank you for your response. --prasanth

[zacfranki]

Hi mahesh
i see the post where you are involved about an udf for phase change in vof model. Can you send me the udf that you have written?

Thanks a lot
David