[Hirakjyoti]

I am working on a multiphase model where the two phases are air and a salt solution. I have interpreted an UDF for density of the solution in terms of mass fraction of the solution. But while initializing it shows fatal error segmentation fault. Please help me by guiding me in the right direction.

#include "udf.h"
DEFINE_PROPERTY(cell_density,c,t)
{
real zeta =C_YI_M1(c,t,1);
real theta = zeta/(1-zeta);
C_R(c,t)= 997*( 1 + (.540966*theta) - (.303792*theta*theta) + (.100791*pow(theta,3)));
return C_R(c,t);
}

[AlexanderZ]

Initialize first, than load UDF.

Same problem had been discussed on forum not long ago. Use search

Best regards

[Hirakjyoti]

Thanks AlexanderZ. But after calculating 2 iterations it is showing
# Divergence detected in AMG for x-momentum: protective actions enabled!
# Divergence detected in AMG for x-momentum, temporarily solve with BCGSTAB!
i am facing big trouble with this model. plz help

[jaguar3096]

Do you want to return a function C_R (c,t) which is defined by you?

[Hirakjyoti]

Originally Posted by jaguar3096

Do you want to return a function C_R (c,t) which is defined by you?

Hi jaguar3096. In my problem LiCl concentration in the solution is changing with time by taking moisture from air, so the density will change. So, my UDF needs to return the density value to the solver.

[AlexanderZ]

Did you try to look at manual?
C_YI_M1 macros returns species mass fraction, previous time step

Try this code. I did not test it

#include "udf.h"
DEFINE_PROPERTY(cell_density,c,t)
{
real udf_density;
real zeta =C_YI(c,t,1);
real theta = zeta/(1-zeta);
udf_density= 997*( 1 + (.540966*theta) - (.303792*theta*theta) + (.100791*pow(theta,3)));
return udf_density;
}

Best regards

[Hirakjyoti]

Thanks AlexanderZ for your guidance. But it is showing the same error. I have also checked the under relaxation factors but nothing is changing . Again i am looking for an UDF for mass diffusivity of LiCl in the solution in terms of concentration and temperature. But i am not getting any information.If possible plz provide some information.