[hbilal1076]

I am working on a Flame Combustor, I want to add "radiation" to my model. my supervisor suggested me to use P1 radiation modeling using User Define Scalars (UDS) from fluent manual under three different conditions i.e.
(1) Optical Thin Assumption Model (OTA) (gray gas model) (2) Narrow Band Correlated K- Distribution Model (NBCK) and (3) Full Spectrum Correlated K- Distribution Model (FSCK).
Although I have fluent manual but as I don't have any programing knowledge/skill to edit and use the below "User Define Function (UDF)" for above three condition.
In summary, how radiative source term can be added into energy equation for above model using macro define source?

Below is the example (P1 radiation model using UDS) from the fluent manual.


#include "udf.h"
#include "sg.h"

/* Define which user-defined scalars to use. */
enum
{
P1,
N_REQUIRED_UDS
};

static real abs_coeff = 0.2; /* absorption coefficient */
static real scat_coeff = 0.0; /* scattering coefficient */
static real las_coeff = 0.0; /* linear-anisotropic */
/* scattering coefficient */

static real epsilon_w = 1.0; /* wall emissivity */

DEFINE_ADJUST(p1_adjust, domain)
{
/* Make sure there are enough user defined-scalars. */
if (n_uds < N_REQUIRED_UDS)
Internal_Error("not enough user-defined scalars allocated");
}

DEFINE_SOURCE(energy_source, c, t, dS, eqn)
{
dS[eqn] = -16.*abs_coeff*SIGMA_SBC*pow(C_T(c, t), 3.);
return -abs_coeff * (4.*SIGMA_SBC*pow(C_T(c, t), 4.) - C_UDSI(c, t, P1));
}

DEFINE_SOURCE(p1_source, c, t, dS, eqn)
{
dS[eqn] = -abs_coeff;
return abs_coeff * (4.*SIGMA_SBC*pow(C_T(c, t), 4.) - C_UDSI(c, t, P1));
}

DEFINE_DIFFUSIVITY(p1_diffusivity, c, t, i)
{
return 1. / (3.*abs_coeff + (3. - las_coeff)*scat_coeff);
}

DEFINE_PROFILE(p1_bc, thread, position)
{
face_t f;
real A[ND_ND], At;
real dG[ND_ND], dr0[ND_ND], es[ND_ND], ds, A_by_es;
real aterm, alpha0, beta0, gamma0, Gsource, Ibw;
real Ew = epsilon_w / (2.*(2. - epsilon_w));
Thread *t0 = thread->t0;
/* Do nothing if areas are not computed yet or not next to fluid. */
if (!Data_Valid_P() || !FLUID_THREAD_P(t0)) return;
begin_f_loop(f, thread)
{
cell_t c0 = F_C0(f, thread);
BOUNDARY_FACE_GEOMETRY(f, thread, A, ds, es, A_by_es, dr0);
At = NV_MAG(A);
if (NULLP(T_STORAGE_R_NV(t0, SV_UDSI_G(P1))))
Gsource = 0.; /* if gradient not stored yet */
else
BOUNDARY_SECONDARY_GRADIENT_SOURCE(Gsource, SV_UDSI_G(P1), dG, es, A_by_es, 1.);
gamma0 = C_UDSI_DIFF(c0, t0, P1);
alpha0 = A_by_es / ds;
beta0 = Gsource / alpha0;
aterm = alpha0 * gamma0 / At;
Ibw = SIGMA_SBC * pow(WALL_TEMP_OUTER(f, thread), 4.) / M_PI;

/* Specify the radiative heat flux. */
F_PROFILE(f, thread, position) = aterm * Ew / (Ew + aterm)*(4.*M_PI*Ibw - C_UDSI(c0, t0, P1) + beta0);
}
end_f_loop(f, thread)
}

DEFINE_HEAT_FLUX(heat_flux, f, t, c0, t0, cid, cir)
{
real Ew = epsilon_w / (2.*(2. - epsilon_w));
cir[0] = Ew * F_UDSI(f, t, P1);
cir[3] = 4.0 * Ew * SIGMA_SBC;
}