Learning Forum

[sjohn]

I wrote a UDF to specify density as a function of  temperature for a multi-species, multiphase model. This is the error I get.

  step  flow-time     p-inlet

     0  0.0000e+00 -1.0553e-14

 

Updating solution at time level N...

 done.

 

  iter  continuity  x-velocity  y-velocity  z-velocity      energy  ch44-p  ch3oh-pha  n2-phase-a  co2-phase-  vf-phase-a     time/iter

        Stabilizing pressure coupled to enhance linear solver robustness.

        Stabilizing pressure coupled using GMRES to enhance linear solver robustness.

 

Experiencing convergence difficulties - temporarily relaxing and trying again...

 

Experiencing convergence difficulties - temporarily relaxing and trying again...

 

Experiencing convergence difficulties - temporarily relaxing and trying again...

 

Experiencing convergence difficulties - temporarily relaxing and trying again...

        Stabilizing pressure coupled to enhance linear solver robustness.

        Stabilizing pressure coupled using GMRES to enhance linear solver robustness.

 

Experiencing convergence difficulties - temporarily relaxing and trying again...

 

Divergence detected in AMG solver: pressure coupled temperature limited to 3.273150e+03 in 387997 cells on zone 1231 in domain 1

         Stabilizing vof-1 to enhance linear solver robustness.

        Stabilizing vof-1 using GMRES to enhance linear solver robustness.

 

Divergence detected in AMG solver: vof-1

Divergence detected in AMG solver: pressure coupled

Divergence detected in AMG solver: vof-1

Divergence detected in AMG solver: pressure coupled

Divergence detected in AMG solver: vof-1

Divergence detected in AMG solver: pressure coupled

Divergence detected in AMG solver: vof-1

Divergence detected in AMG solver: pressure coupled

Divergence detected in AMG solver: vof-1

Divergence detected in AMG solver: pressure coupled

Divergence detected in AMG solver: vof-1

Divergence detected in AMG solver: pressure coupled

Divergence detected in AMG solver: vof-1

Divergence detected in AMG solver: pressure coupled

Divergence detected in AMG solver: vof-1

Divergence detected in AMG solver: pressure coupled

Divergence detected in AMG solver: vof-1

Divergence detected in AMG solver: pressure coupled

Divergence detected in AMG solver: vof-1

Divergence detected in AMG solver: pressure coupled

Divergence detected in AMG solver: vof-1

Divergence detected in AMG solver: pressure coupled

Divergence detected in AMG solver: vof-1

Error at host: floating point exception

 

Error: floating point exception

Error Object: ()

 

Error at Node 5: floating point exception

 

Error at Node 4: floating point exception

 

Error at Node 6: floating point exception

 

Error at Node 3: floating point exception

 

Error at Node 10: floating point exception

 

Error at Node 7: floating point exception

 

Error at Node 0: floating point exception

 

Error at Node 9: floating point exception

 

Error at Node 8: floating point exception

 

Error at Node 1: floating point exception

 

Error at Node 11: floating point exception

 

Error at Node 2: floating point exception

 

Error: floating point exception

Would someone be able to review my UDF (below) and tell me if there is an obvious mistake.

#include "udf.h"

/* Define the UDF to specify temperature-dependent density */

DEFINE_PROPERTY(temperature_dependent_density, cell, thread)

{

    real T;  /* Temperature */

    real density;  /* Density */

    real vol_frac;  /* Volume fraction of phase A */

 

    /* Loop over all cells in the thread */

    begin_c_loop(cell, thread)

    {

        /* Get the volume fraction of phase A in the cell */

        vol_frac = C_VOF(cell, thread);

 

        /* Check if the volume fraction of phase A is greater than 50% */

        if (vol_frac > 0.5)

        {

            /* Get the temperature of the cell */

            T = C_T(cell, thread);

 

            /* Calculate the density based on the given relationship */

            density = 1.4811 - 0.0007 * T;

 

            /* Set the density for the cell */

            C_R(cell, thread) = density;

        }

    }

    end_c_loop(cell, thread)

 

    return density;

}

[Rob]

It's diverging, so the code is grammatically correct. But.... Is your intent to set a material density based on the species or phase fraction in a cell? Have a think about the physics, why would that be the case? 

[sjohn]

I would like to set the density based on phase fraction because the temperature-dependent density equation is for the phase. Instead of 50%, I could use 100% as the condition to change density as per temperature.

[Rob]

You're setting the phase density based on the phase fraction. You're not setting the mixture density.