# VOF model - volume fraction residual question

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 April 28, 2008, 19:31 VOF model - volume fraction residual question #1 Wim Heirwegh Guest   Posts: n/a 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 k-epsilon turbulence model - but without 'implicit body force' treatment Now at the start of my simulation the scaled Residual 'volume fraction of 2-phase' has the value 1.8e-5 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 'vf-2phase' residual that remained constant? Or is there a flaw in my moddeling? If someone has any experience with the 'vf-2phase' residual that can give some pointers. Every comment is helpfull. I like to keep the simulation steady-state thank you

 May 3, 2008, 14:37 Re: VOF model - volume fraction residual question #2 kk Guest   Posts: n/a 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 kk Guest   Posts: n/a 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 #4 Wim Heirwegh Guest   Posts: n/a 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 'vf-phase2' residu has a value of 2.1e-5 It stays around this value while velocity+continuity converges. (velocity residus starts at 2.0e0 and converge to 1e-7) 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 Wim Heirwegh Guest   Posts: n/a 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 Senior Member   Emre G Join Date: May 2011 Location: Turkey Posts: 120 Rep Power: 7 hi i hav a problem just same with this. residual vf-phase-2 appears allways zero during whole of the transient iteration other residuals change meaningly. i dont know why vf-phase-2 doesnt change could u help me plz

 July 4, 2013, 01:16 #7 New Member   yes Join Date: Jul 2013 Posts: 7 Rep Power: 5 Please sir send me bowl tutorial...

July 4, 2013, 07:21
#8
Senior Member

Jamal Foroozesh
Join Date: Oct 2012
Location: Iran
Posts: 141
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Quote:
 Originally Posted by gajendra Please sir send me bowl tutorial...
I can send to you this tutorial. Please send to me your email

 July 8, 2013, 12:08 #9 New Member   Bhargav Join Date: Jun 2013 Posts: 6 Rep Power: 5 Can someone send me the bowl tutorial please ybhargav93@gmail.com thank u

July 8, 2013, 13:44
#10
Senior Member

Jamal Foroozesh
Join Date: Oct 2012
Location: Iran
Posts: 141
Rep Power: 6
Quote:
 Originally Posted by Bhargav93 Can someone send me the bowl tutorial please ybhargav93@gmail.com thank u
I sent that.
Best Regards

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