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-   -   VOF implicit or explicit (http://www.cfd-online.com/Forums/fluent/103541-vof-implicit-explicit.html)

hamid1 June 20, 2012 08:17

VOF implicit or explicit
 
Hi
Is implicit VOF inaccurate?
the advantage of implicit over explicit is it is very much faster,
thank you
Hamid

fevi84 June 21, 2012 16:45

The difference between VOF explicit and implicit is that the VOF explicit enables the use PLIC method (Geo Reconstruction in Fluent) for the volume fraction. The PLIC method (Piecewise Linear Interface Construction) is the best method available in Fluent for the interface reconstruction. So that if your interesting is the interface modeling is recommendable the use of VOF explicit

hamid1 June 22, 2012 05:00

thanks so much for reply,
I am mostly interested on the whole process as well as the movement of the second phase but not very sharp interface however something acceptable, i switched from explicit geo-reconstruct to implicit modified HRIC, so that the time step from around 0.0001 (variable enabled with courant n. max 0.95) in explicit turned to 0.01 or even 0.1 in implicit,
but the problem is I have divergence issue specifically for continuity and also vof phase2 , i am not sure how I can fix it, I turned the the under relaxation factors so much low and let 50 iteration per time step but it doesnt work,
any suggestions are truly appreciated,

thank you
Hamid

amin66 June 23, 2012 18:01

Dear Hamid
yes i think implicit is faster but maybe more problem with convergence(not sure)
the method that you want to use depends on your problem!

look at this page: specialy end of the page.
http://hpce.iitm.ac.in/website/Manua...ug/node935.htm

sicfred June 25, 2012 04:51

Dear Hamid,

There was a webinar in ansys where the explain the methods and options what you can use in fluent to resolve sloshing or free surface problems, and you can download it from the web site. I watched and it was very helpfull.

The web page is:
http://www.ansys.com/Resource+Librar...+Transmissions

I hope it will help you


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