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April 28, 2008, 19:31 
VOF model  volume fraction residual question

#1 
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Hi,
let me first situate the problem i'm working on: I'm moddeling a stirred cup filled with water in normal environment (air). There are no inlets and no outlets. I'm trying to simulate the vortex that's formed by stirring in steady state. For this I use following options:  VOF model with implicit formulation  PISO  Modified HRIC for volume fraction discretization  Presto for pressure discretization  Second order upwind discretization on others (momentum,...)  RNG kepsilon turbulence model  but without 'implicit body force' treatment Now at the start of my simulation the scaled Residual 'volume fraction of 2phase' has the value 1.8e5 and remains around this value the whole time. It doesn't converge like the rest of my parameters... When i check my results after convergence of the other parameters it gives strange results: there isn't any outlined interface between the two phases (water and air). Instead there is a gradual change of the volume fraction from 0.01 to 0.98 over a wide distance in the cup. For me this result doesn't seem to respond to reality where you can clearly see one nice vortex in a stirred water cup. Could this be a problem with the value of the 'vf2phase' residual that remained constant? Or is there a flaw in my moddeling? If someone has any experience with the 'vf2phase' residual that can give some pointers. Every comment is helpfull. I like to keep the simulation steadystate thank you 

May 3, 2008, 14:37 
Re: VOF model  volume fraction residual question

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try to patch water in part of the cup using adapt>region then see how it will behave be careful most VOF calculation depend mostly at the proper boundary condition and the proper way to start the slution with so you need a lot of choices.


May 3, 2008, 14:41 
Re: VOF model  volume fraction residual question

#3 
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try to see also the bowl tutorial it may be useful for you.


May 3, 2008, 16:54 
Re: VOF model  volume fraction residual question

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thanks for your reply!
Do you suggest to patch water with my current results and continue with the simulation? Because I already patched water at the start of my simulation. The first iteration my scaled 'vfphase2' residu has a value of 2.1e5 It stays around this value while velocity+continuity converges. (velocity residus starts at 2.0e0 and converge to 1e7) Maybe some extra information on my cup geometry: It's top is closed off. It's filled half water, half air. Because it's sealed off of the environment, I don't use any boundary conditions. extra info on setup: I initialized a volume fraction of 0 over the whole domain. Then marked 50% with adapt>region and patched a volume fraction of 1. (maybe this is what i'm doing wrong? if you read section 23.2.4 of the help file, they advise not to initialize zones with 0 volume fraction for a steady case) Comment or reactions are always welcome! BTW: The bowl tutorial was the first thing i read before starting the setup of my simulation. 

May 3, 2008, 16:59 
Re: VOF model  volume fraction residual question

#5 
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it actually seems a very simpel problem... yust a stirred cup of water or coffee with your hand closing off the cup. I want to see if it makes much difference in vortex production and pressure distribution with your hand or not.


November 15, 2011, 10:47 

#6 
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Emre G
Join Date: May 2011
Location: Turkey
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hi
i hav a problem just same with this. residual vfphase2 appears allways zero during whole of the transient iteration other residuals change meaningly. i dont know why vfphase2 doesnt change could u help me plz 

July 4, 2013, 01:16 

#7 
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yes
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Please sir send me bowl tutorial...


July 4, 2013, 07:21 

#8 
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Jamal Foroozesh
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July 8, 2013, 12:08 

#9 
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Bhargav
Join Date: Jun 2013
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Can someone send me the bowl tutorial please ybhargav93@gmail.com thank u


July 8, 2013, 13:44 

#10  
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Jamal Foroozesh
Join Date: Oct 2012
Location: Iran
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Quote:
Best Regards 

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