[dagang]

Hi friends,
I am trying to writing a udf for time-dependent slurries, for which a structural index were proposed. However, this index doesn't exist in fluent. How can i define and use it?

[AlexanderZ]

you may use User Defined Scalars to solve new equations
material property there is UDS diffusivity
read ansys fluent customization manual

[dagang]

Originally Posted by AlexanderZ

you may use User Defined Scalars to solve new equations
material property there is UDS diffusivity
read ansys fluent customization manual

#include "udf.h"
#include "mem.h"
DEFINE_PROFILE(inlet_uds,t,p)
{
float uds;
face_t f;
begin_f_loop(f,t)
{
uds=1e-20;
F_PROFILE(f,t,p)=uds;
}
end_f_loop(f,loop)
}
DEFINE_PROFILE(outlet_uds,t,p)
{
face_t f;
float K=0.239;
float rate=(C_STRAIN_RATE_MAG(f,t));
begin_f_loop(f,t)
{
F_PROFILE(f,t,p)=exp(-K*rate);
}
end_f_loop(f,loop)
}

DEFINE_PROFILE(Adjust_uds,t,p)
{
cell_t c;
thread_loop_c(c,t)
{
begin_c_loop(c,t)
{
real rate;
real Namoda;
real K=0.239;
real Nnnn;
real Constant_a;
real Deta_Namoda;
real RealTime=CURRENT_TIME;
real TimeStep=CURRENT_TIMESTEP;
rate=(C_STRAIN_RATE_MAG(c,t));
Nnnn=0.7032*exp(-7.249*rate);
Constant_a=0.04199/pow(0.6,Nnnn);
Deta_Namoda=Constant_a*pow(rate,Nnnn)*exp(-K*rate)-Constant_a*pow(rate,Nnnn)*C_UDSI(c,t,0);
C_UDSI(c,t,0)=C_UDSI(c,t,0)-Deta_Namoda*TimeStep;
C_PROFILE(c,t,p)=C_UDSI(c,t,0);
}
end_c_loop(c,loop)
}
}

DEFINE_PROPERTY(Thixotropy_viscosity, c, t)
{
real visco;
real rate;
real BinghamVisco=0.172;
real Constant_C=28.52;
rate=(C_STRAIN_RATE_MAG(c,t));
if (rate>0.00001)
visco=(40+BinghamVisco*rate-Constant_C*C_UDSI(c,t,0))/rate;
else
visco=(40+BinghamVisco*0.00001-Constant_C*C_UDSI(c,t,0))/0.00001;
return visco;
}


Hi AlexanderZ,
Here is a udf code i wrote to represent the thixotropy of fluids. A structural parameter was proposed to characterize the degree of structure under shear. I use UDS to represent the structural parameter. However, this code doesnt work. Can you help me modify it? Or do you know any available code for thixotropic fluids. Many researcheres published papers about thixotropy and structural parameter, unfortunately i cant find even one code of thixotropic fluids. Thanks.