C_VOF not changing at all during simulation

  • Last Post 18 February 2019
  • Topic Is Solved
gunjanauti posted this 17 February 2019

I have written a udf to initialize VOF with a profile (which works fine). I am solving with multiphase (VoF model), energy and viscous laminar flow equation. The solver should solve the volume fraction equation and change the values of the volume fraction. After a lot of effort I tried creating a UDS (C_UDSI(c,t,0)=C_VOF(c,t)). It solves the uds equation properly. Does anyone have and idea why is this the case? Why can't I get the values by using C_VOF alone? Otherwise post-processing is a major headache if I have to use the uds everywhere.

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abenhadj posted this 17 February 2019

Can you please shed some more details about your run? Do you have see a change in the VOF field in Fluent? Perhaps you are using the wrong threads to access VOF?



Best regards, Amine

gunjanauti posted this 18 February 2019




    Thread *t;

    cell_t c;

    face_t f;

    real domain_ID =2;

    Domain *domain;

    domain = Get_Domain(domain_ID);


    thread_loop_c (t, domain)


       begin_c_loop (c,t)


           C_UDSI(c,t,0) = C_VOF(c,t);


       end_c_loop (c,t)



Actually I want to use the gradient of C_VOF but as I am running fluent in parallel mode I am not able to retain the gradients of secondary variables using 'solve set expert'. So I have stored the C_VOF in a form of UDS (for liquid phase and flux and unsteady function as none). Now this UDS starts to diverge (the residuals start increasing beyond the set point) after a few time steps but C_VOF does not change at all. 

So is there a different way through which I can use the C_VOF_G? or what changes should I make to this udf? 




abenhadj posted this 18 February 2019

Domain ID is the phase ID of primary phase. The problem here is the UDS: is it defined for the mixture? If yes then wrong.


To access VOF gradient the only official way is by that TUI command. You can access the RG of VOF within an Adjust.

Best regards, Amine

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gunjanauti posted this 18 February 2019

I have defined the UDS for liquid (the primary phase). I'll try using RG