[sahoo]

hello everyone,
Actually I am trying to code the following equation :-
[∇α(T)]TJ=-∇UDS2 T/ρ(T) ∇UDS0
So, I need to use UDS0 & UDS2 in third UDS, for which I made the following code :-

#include "udf.h"
#include "math.h"

enum
{
teg4,
N_REQUIRED_UDS
};

real k_function(real T)
{
return -1.097 + 1.234e-2*T - 3.736e-5*pow(T,2.) + 3.75e-8*pow(T,3.);
}
real rho_function(real T)
{
return -3.982e-5 + 2.98e-7*T - 4.685*e-10*pow(T,2.) + 2.51e-12*pow(T,3.)
}

DEFINE_DIFFUSIVITY(teg4_diffusivity, cell, thread, i)
{
C_UDSI(c,t,teg4) = k_function(C_T(c,t));
return C_UDSI(c,t,teg4);
}

DEFINE_SOURCE(energy_source, c, t, dS, eqn)
{
dS[eqn] = C_UDSI(c,t,teg2)*(T/rho_function(C_T(c,t)))*C_UDSI(c,t,teg);
return C_UDSI_G(c,t,teg2)*(T/rho_function(C_T(c,t)))*C_UDSI_G(c,t,teg);
}

I am getting errors like teg, teg2 not declared.
Can anyone suggest whether the code is wrong or there is some other way to do it?

[`e`]

Originally Posted by sahoo

I am getting errors like teg, teg2 not declared.

Because you have not declared these variables. Add these entries to the enum:

enum
{
	teg,
	teg1,
	teg4,
	N_REQUIRED_UDS
};

Note that this replaces "teg" with "0", "teg1" with "1" and "teg4" with "2", such that C_UDSI(c,t,teg4) calls the cell value of the third UDS defined.

Originally Posted by sahoo

Can anyone suggest whether the code is wrong or there is some other way to do it?

As previously suggested, perhaps write out the equations you are trying to solve in full and compare these with the UDS transport equations in Fluent. Explicitly, start with writing out the equations you are solving for in each spatial direction (considering the variables are vectors with gradients). Next, find the transport equations used by Fluent for the UDS in the theory guide (note: they are scalars, not vectors). Lastly, match these two sets of equations and determine which scalar terms are appropriate for allocating to UDS.

[sahoo]

Thanks for your advice, I am going to follow the procedure as described by you.