UDF for defining granular viscosity in mixture model
 

Hello all,

I am new to fluent and I want to use a UDF for defining the granualar viscosity of the secondary phase in the mixture model :
mu= -0.188 + 537.42*Volume fraction.

I had written the follwoing UDF.

#include "udf.h"
DEFINE_PROPERTY(solid_viscosity,cell, thread)
{
real mu;
real vf=C_T(cell,thread);
mu=-0.188+537.42*vf;
return mu;
}

This is correct? And how can I use this in my case. Can anyone help?

Thanks

I think you need to use DEFINE_ADJUST macros to modify the volume fraction using C_VOF(cell,thread)*constant; save this in user defined memory then use this User defined memory in DEFINE_PROPERTY macro like mu=C_UDMI(cell,thread,i).

secondary phase thermal conductivity
 

Hello,

I'm new with Fluent and with UDF, and in my case, I have to modify my secondary thermal conductivity with the formula:

k = (-0.76 + 0.0063*T)*alfa

with:

T = secondary phase temperature
alfa = secondary phase volume fraction

Is this UDF written properly?

#include "udf.h"

DEFINE_PROPERTY(k_coke, c, t)
{
real k_c;
real temp = C_T(c, t);
real vf_c = C_VOF(c, t);

k_c = (-0.76 + 0.0063*temp)*vf_c;

return k_c;
}

My doubt is if I'm taking the secondary variables (volume fraction and temperature) correctly. Can anyone help me?

Can you help me with the granular viscosity, how did you find granular viscosity and solid pressure and other properties?

Granular Vicosity and granular solids pressure Macro = DEFINE_PROPERTY

I don't know any equation to calculate granular viscosity. Is there some empirical relation that I can use?

Have you take a look at the theory guide? There you can find the equation for each model that Fluent provides.

Yes, I have. I have come across two equations, one for collisional viscosity and other one is for kinetic viscosity.