[thedal]

I have written this code to get the Density gradient in a pressure-based solver by switching ON UDS for density. But it gives SIGSEGV error.

This is based on the UDF Example available in Fluent Manual for getting Temperature gradient. I changed it to Density. Since face values are not available for density, I interpolated and calculated it.

# include "udf.h"

DEFINE_ADJUST(adjust_gradient, domain)
{
    Thread* t;
    cell_t c;
    face_t f;

    /* Fill UDS with the variable. */
    thread_loop_c(t, domain)
    {
        begin_c_loop(c, t)
        {
            C_UDSI(c, t, 0) = C_R(c, t);
        }
        end_c_loop(c, t)
    }

    thread_loop_f(t, domain)
    {
        if (THREAD_STORAGE(t, SV_UDS_I(0)) != NULL)
            begin_f_loop(f, t)
        {
            
            F_UDSI(f, t, 0) = (C_R(F_C0(f, t), THREAD_T0(t)) + C_R(F_C1(f, t), THREAD_T1(t))) / 2;
        }
        end_f_loop(f, t)
    }
}

DEFINE_SOURCE(gradient_source, c, t, dS, eqn)
{
    real source;

    source = C_UDSI_G(c, t, 0)[1];

    dS[eqn] = 0;
    return source;
}