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UDF for modifying density of mixture phase during the calculating process

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Old   January 11, 2016, 03:38
Default UDF for modifying density of mixture phase during the calculating process
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Meng Liu
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I‘m dealing with a problem about multiphase flow. I want to modify the density of mixture phase during the calculating process. But the UDF doesn't work. Did anyone ever try to modify flow variables by UDF? Here is my UDF.

Code:
/* domain pointer that is passed by adjust function is mixture domain */ 
DEFINE_ADJUST(adjust_fcn,mixture_domain)
{
	int phase_domain_index;
	real rhoW, rhoV, VFv;
	cell_t cell;
	Thread *M_t; /*define mixture phase thread */
	Thread *w_t; /*define the primary phase thread */
	Thread *v_t; /*define the secondary phase thread */
	Domain *subdomain;
	
	/* loop over all subdomains (phases) in the superdomain (mixture) */
    sub_domain_loop(subdomain, mixture_domain, phase_domain_index)
    {
		if (DOMAIN_ID(subdomain) == 2)
      /* loop over all cell threads in the primary phase domain */
		thread_loop_c (w_t,subdomain)
		{
      /* loop over all cells in primary phase cell threads */
			begin_c_loop_all (cell,w_t)
			{
				rhoW=C_R(cell,w_t); /* density of water */
			}
			end_c_loop_all (cell,w_t)
		}
	  /* loop if secondary phase */
		else if (DOMAIN_ID(subdomain) == 3)
      /* loop over all cell threads in the secondary phase domain */
		thread_loop_c (v_t,subdomain)
		{
      /* loop over all cells in secondary phase cell threads */
			begin_c_loop_all (cell,v_t)
			{
      /* set volume fraction of vapor */
				VFv=C_VOF(cell,v_t);
				rhoV=C_R(cell,v_t); /* density of vapor */
			}
			end_c_loop_all (cell,v_t)
		}	
	}
	/* loop over all cell threads in the Mixture phase domain */
	thread_loop_c (M_t,mixture_domain)
	{
    /* loop over all cells in Mixture phase cell threads */
		begin_c_loop_all (cell,M_t)
		{
			C_R(cell,M_t)=VFv*rhoV+(1-VFv)*rhoW; /* density of mixture */
		}
		end_c_loop_all (cell,M_t)
	}
 }
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Old   May 25, 2019, 05:50
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hi,
I want to consider in the mixture model ,the thermal conductivity depend on temperature, but I'm having trouble writing the code as well as applying it to the fluent. Is your problem solved? If possible, contact me via email.
faezeh0012.m@gmail.com
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Old   May 28, 2019, 09:24
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Hi Zahra-M,


Maybe it's not obvious, but temperature-dependent conductivity is a *lot* easier than multiphase-dependent density. If you want a UDF for it, please go and look at DEFINE_PROPERTY.


In most instances (unless you will be tweaking the parameters repeatedly), I would recommend simply setting up a piecewise-linear list, instead of a UDF.


Oh, and sola86's approach (back in 2016) was not a recommended one. If you sneak user-defined values into the solution variables, the solver will either overwrite them or get confused, or both. To adjust the solution, tell Fluent how to adjust it, using user-defined properties and source terms.


Good luck!
Ed
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