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Old   July 23, 2008, 12:50
Default vof boundary conditions
  #1
carlos
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Hello, Iīm working on a closed tank filled the 12,5% of water and the rest with air. I know every thing but the boundary conditions. In boundary conditions panel I have three zones, exterior, interior and solid. I donīt know how to say where is the water and where is the air. Thanks in advance
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Old   July 23, 2008, 13:43
Default Re: vof boundary conditions
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George Kakavas
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In order to display the waves, you need to adapt a region from y=0 until y= the initial water height, and then you patch this region with water phase and set volume fraction equal to 1. then display contours of phases-water and you will see that Fluent recognized the area of the water. At inlet conditions, if you have a udf for your velocities then enter them at boundary conditions. If not, try to create a dynamic zone mesh for the inlet boundary again with a sinusoidal function to create the waves.

Hope it helps
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Old   July 24, 2008, 10:52
Default Re: vof boundary conditions
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carlos
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I am really greatfull for your help. I wouldnīt suspect of adapt a region, but what do you mean with patch that region with water?what are the commands for that?
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Old   July 24, 2008, 10:58
Default Re: vof boundary conditions
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George Kakavas
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After adapting the region that contains the water, you should go: solve-initialize-patch..select haexaedron at the right then water at the phase list and the only option below is volume fraction..then set its value to 1 instead of 0 which is the default. To make sure it works, display contours of water phases and there you will be able to see the water in your tank with a red colour.. In order to display your waves while simulating, go to execute commands and set 2 commands for lets say every 10 time steps: 1) display set-window 1 2) display contour water vof 0 1

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Old   July 24, 2008, 11:19
Default Re: vof boundary conditions
  #5
carlos
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But I do not have that options for patching because i think the adaptation has any kind of error. I get this:

Grid size ( original / adapted / change)

cells ( 1323 / 1323 / 0)

faces ( 2705 / 2705 / 0)

nodes ( 1383 / 1383 / 0) Error: Set_Thread_Variables: wta(real) Error Object: ((constant . 1) (profile "" ""))
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Old   July 24, 2008, 11:22
Default Re: vof boundary conditions
  #6
George Kakavas
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hmmmm when adapting, instead of adapt press mark..it should work now..i had the same error before.. then the options for patching should appear..
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Old   July 24, 2008, 11:54
Default Re: vof boundary conditions
  #7
carlos
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I now have the hexahedron option but I do not have the water phase option ,instead of that I have solid.maybe I should change the boundary conditions, I think all my errors are on that but I have changed them so many times...I am desperated
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Old   July 24, 2008, 12:13
Default Re: vof boundary conditions
  #8
George Kakavas
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hmm have you defined your phases when enabling vof model? check that boundary conditions do not realy play a role here..mixture and water phase should appear when patching

and remember patch AFTER you have initialized your flow field..otherwise Fluent will be confused and display a tank full of water or air...

do that from the beginning..enable vof, define phases primary=air, secondary=water (add water from fluent data base materials) and then operating conditions, initilize the pressure and enable gravity, then boundary conditions, only velocity inlet conditions for start.then initialize the whole flow field and then try to adapt and patch.. iterate to see if the model works, and then try to alter your boundary conditions.. remember that because it is a multiphase model, you normaly should use unsteady solver..

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Old   July 24, 2008, 13:05
Default Re: vof boundary conditions
  #9
carlos
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I have started doing all the things you said and it is still displaying the hole tank full of water.and mixture and water are not available for patching. I think it should be any of two things: -the mesh in which i have like separated but linked-node zones(maybe i have to do like a only simple mesh)I will send you by e-mail and see what you think -boundary conditions(when you say velocity-inlet you mean for the exterior zone and for mixture?)I have to say that previously I was using a moving wall.

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Old   July 24, 2008, 16:52
Default Re: vof boundary conditions
  #10
George Kakavas
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if it displays only water..initialize the flow field again and then try to re mark cells and select the bottom of the 2 haexadrons at patching..set volume fraction =1..it should work..the grid does not play a role here then plot filled contours of volume fraction (water) it should work boundary conditions should be defined both for mixture face and water phase normaly..but even so it should work..i do not see any other problem here
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Old   July 25, 2008, 07:40
Default Re: vof boundary conditions
  #11
George Kakavas
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there is also a very good tutorial that is similar to your problem it will really help you. i ll just post the link here download the wave file

http://www.fluent.com/software/sf_me...orial_wave.htm

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Old   July 27, 2008, 13:57
Default Re: vof boundary conditions
  #12
carlos
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I finally did it.It was that I was using an old version. I download a new one I did as you said and it worked. You donīt know how thankfull i am to you. I just have to find a UDF to put time in my velocity. if you know any let me know. Thanks a lot you saved my life
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Old   July 27, 2008, 15:19
Default Re: vof boundary conditions
  #13
George Kakavas
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any time...take care
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