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-   -   Difficult to model using vof (http://www.cfd-online.com/Forums/fluent-multiphase/120389-difficult-model-using-vof.html)

elahe65 July 5, 2013 14:41

Difficult to model using vof
 
I will be very grateful if you could answer my question, I want to a two-phase model using vof, including water and air. Do I need to define the two-volume in gambit or in Fluent need to do this?
For example, 0.15 m air and 0.2 m water in the canals, where should I enter these values? how about the volume fraction According to these values?

jamalf64 July 5, 2013 18:49

Quote:

Originally Posted by elahe65 (Post 438045)
I will be very grateful if you could answer my question, I want to a two-phase model using vof, including water and air. Do I need to define the two-volume in gambit or in Fluent need to do this?
For example, 0.15 m air and 0.2 m water in the canals, where should I enter these values? how about the volume fraction According to these values?

You dont need to define two volumes in gambit.
after initialization in fluent you must patch second phase.
step by step: 1- define air as primary phase 2- define water as secondary phase 3- initialize 4- adapt/region/define range of x,y,z for patch secondary phase/mark 5- solve/initialize/patch(phase:water/variable:volume fraction/register to patch:marked zone in step 4/ click patch) 6- iterate

I hope this help you
Jamal

flow_CH July 6, 2013 00:49

I am doing this subject but when i am using open channel flow boundary and patch the water, after a few iterate, the water height is good but after more iteration water is going up and Occupies whole the model.
I think the problem is due to initialize option. Every time i choose compute from all zones, this problem occurs and Every time i enter x velocity, just a little water enter from inlet and flowing to downstream( there is no flow, back of that water)
please help

jamalf64 July 6, 2013 03:38

Quote:

Originally Posted by flow_CH (Post 438070)
I am doing this subject but when i am using open channel flow boundary and patch the water, after a few iterate, the water height is good but after more iteration water is going up and Occupies whole the model.
I think the problem is due to initialize option. Every time i choose compute from all zones, this problem occurs and Every time i enter x velocity, just a little water enter from inlet and flowing to downstream( there is no flow, back of that water) see attached image
please help

you must wait until solution be converged. this way(your method) is wrong to judge.

flow_CH July 6, 2013 05:30

which case? the first that water Occupies whole the model or about two images?

thermal energy March 14, 2014 12:36

Hello dear friends,

I try to simulate melting process using VOF model. Pcm is solid phase initialy. Upper part of the solid there is air. They do not mix eachother. Natural convection is active. My primary phase air, secondary phase is pcm (phase change material). I have some questions to be sure about my model.

First, I do not define interface between air and pcm. Mean, There are 3 cell zone: air, fin ,pcm but I do not create name selection for this interface in meshing. Is it ok?

Initial condition of Wholesystem temperature is 293K, but air temp is 300K. how to set air temp ?

For cell zone condition, all cell zone (air, pcm, fin ) show mixture. Also for example, if I change pcm to phase2, all of cell zone change to phase 2

Only for secondary phase (pcm), I patch within fluent by adapt-region-mark then patch. Ok? Value of volume fraction should be 1 or 0 while patching?? I am confused. Initialy pcm is solid.

For initial values phase-2 volume fraction is 0. Ok?

I did some iteration for a short time to check model. For results, in graphics-countors I can not see total temperature for phase 1 and 2 only entalphy values I see for phase1 and 2.

Also countors of solidification/melting it shows only mixture. Mixture show what?

Any interaction should I use like surface tension etc.

Thanks for your help.


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