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-   -   VOF error when initializing (http://www.cfd-online.com/Forums/cd-adapco/56961-vof-error-when-initializing.html)

 Simone January 21, 2009 07:33

VOF error when initializing

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

 Andrea January 21, 2009 08:12

Re: VOF error when initializing

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

 Simone January 21, 2009 09:07

Re: VOF error when initializing

...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??

 Andrea January 21, 2009 09:19

Re: VOF error when initializing

what kind of simulation is? Steady, transient...and also: underelax, boundary, initialization field/functions...?

 Simone January 21, 2009 09:27

Re: VOF error when initializing

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?

 Adam January 21, 2009 14:27

Re: VOF error when initializing

Are you using first or second order time Discretization?

 Simone January 21, 2009 15:08

Re: VOF error when initializing

second order

 Simone January 21, 2009 15:09

Re: VOF error when initializing

and first order for time!

 Adam January 21, 2009 17:00

Re: VOF error when initializing

Try changing the turbulence specification to K + Epsilon on both the initialization and the inlet.

 Andrea January 23, 2009 08:18

Re: VOF error when initializing

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...

 star February 3, 2009 20:35

Re: VOF error when initializing

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).

 jimmer February 11, 2009 12:26

Re: VOF error when initializing

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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