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VOF error when initializing

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Old   January 21, 2009, 07:33
Default VOF error when initializing
  #1
Simone
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When initializing turbulent flow for VOF calculation, solver get me this error:

"Warning: Initializing turbulent flow with density unavailable in fluid! Density of 1 kg/m^3 assumed for computing initial turbulence quantities."

What is it?? How can I avoid this error??

Thank a lot
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Old   January 21, 2009, 08:12
Default Re: VOF error when initializing
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Andrea
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There's no problem, simply the turbulent flow field will be initialized using a standard density value. Next the turbulent flow will be calculated coerently with the exact density of the fluid...
It's just the initialization
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Old   January 21, 2009, 09:07
Default Re: VOF error when initializing
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Simone
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...ok, but after a few iteration simulation diverge and the iso-surface at VOF=0.5 assume unphysical shape....

With laminar model I don't have this problem!

Any idea??
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Old   January 21, 2009, 09:19
Default Re: VOF error when initializing
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Andrea
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what kind of simulation is? Steady, transient...and also: underelax, boundary, initialization field/functions...?
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Old   January 21, 2009, 09:27
Default Re: VOF error when initializing
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Simone
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Simulation is VOF unsteady, underelax low (0.4, 0.3 etc..), wov wave first order, 6DOF frozen for computing hyrodynamics forces on a ship hull.

Similarly of the demo from CD-Adapco for DFBI, i set the correct bondary conditions, but i change turbulent model...so from laminar to k-omega. Mesh is ok, with B.L.y+=50.

Time step 0.01s

Do you have any experience on this problem?
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Old   January 21, 2009, 14:27
Default Re: VOF error when initializing
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Adam
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Are you using first or second order time Discretization?
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Old   January 21, 2009, 15:08
Default Re: VOF error when initializing
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Simone
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second order

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Old   January 21, 2009, 15:09
Default Re: VOF error when initializing
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Simone
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and first order for time!
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Old   January 21, 2009, 17:00
Default Re: VOF error when initializing
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Adam
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Try changing the turbulence specification to K + Epsilon on both the initialization and the inlet.
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Old   January 23, 2009, 08:18
Default Re: VOF error when initializing
  #10
Andrea
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if it doesn't work try initializing the sim with first order scheme...then switch to second order later
It's a general tip, I'm sorry but I don't have experience in this kind of sim...but the initialization it's similar to other ones...
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Old   February 3, 2009, 20:35
Default Re: VOF error when initializing
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star
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Have you tried lowering the time step? Are you using ccm+ or v4? In v3 I always faced problem when the time step is that large (0.01s). In v4 this seems less a problem. I think I read on the manual or somewhere VOF is not yet able with k-omega or other turbulence models. For DFBI, it might not even able to handle k-E but I'm not sure. BTW, I'm curious to know how long it takes you to complete this run.. the elapsed time I mean... when you complete this job later. (Just curious if you dont mind).

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Old   February 11, 2009, 12:26
Default Re: VOF error when initializing
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jimmer
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I think VOF and turbulence don't go together in STAR-CD. The software calculates granular variables and the only correct choice there is laminar flow.
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