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Old   January 11, 2022, 14:43
Default Uds boundary flux
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Hello! I have to define the boundary condition of my UDS (Φ) as Specified Flux at the pipe wall.

The flux is -f(T)*Φ*∂T/∂r where f is just a function dependent on temperature.

To retrieve the temperature gradient at the face boundary, I have used the following approximation:
(∂^2T/∂r^2)_cell = ( (∂T/∂r)_face - (∂T/∂r)_cell ) / (r_face - r_cell )

this corresponds to :
(∂T/∂r)_face = C_UDSI(c0,t0,3)+dr0[1]*C_UDSI_G(c0,t0,3)[1]

Bcs my C_UDSI(c0,t0,3) stored the temperature gradient.

But this code gives fatal error. Could you please help me? Where am I doing wrong?

#include "udf.h"

DEFINE_PROFILE(my_wall_flux, thread, position)
face_t f;

Thread *t0;
cell_t c0;

real dr0[ND_ND];

real T, alpha, beta, k_w, mu_w, k_p, Dt;

begin_f_loop (f,thread)
c0 = F_C0(f,thread);
t0 = THREAD_T0(thread);

C_UDSI(c0,t0,3) = C_T_G(c0,t0)[1];

T = F_T(f,thread);

alpha = 1e-9;

beta = -6.3516e-5 + 1.6839e-5*(T-273.15) - 1.9824e-7*(T-273.15)*(T-273.15) + 1.6867e-9*(T-273.15)*(T-273.15)*(T-273.15) - 5.7744e-12*(T-273.15)*(T-273.15)*(T-273.15)*(T-273.15);

k_w = 0.5609 - 1.9488e-3*(T-273.15) - 1.0133e-6*(T-273.15)*(T-273.15) - 1.2840e-7*(T-273.15)*(T-273.15)*(T-273.15) + 6.2118e-10*(T-273.15)*(T-273.15)*(T-273.15)*(T-273.15);

mu_w = 1.7825e-3 - 5.8439e-5*(T-273.15) + 1.2592e-6*(T-273.15)*(T-273.15) - 1.6986e-8*(T-273.15)*(T-273.15)*(T-273.15) + 1.2480e-10*(T-273.15)*(T-273.15)*(T-273.15)*(T-273.15) - 3.7458e-13*(T-273.15)*(T-273.15)*(T-273.15)*(T-273.15)*(T-273.15);

k_p = 5.5 + 34.5*exp(-0.0033*T);

Dt = alpha*beta*k_w/(mu_w*(2*k_w+k_p));

F_PROFILE(f,thread,position) = -Dt*F_UDSI(f,thread,0)*(C_UDSI(c0,t0,3)+dr0[1]*C_UDSI_G(c0,t0,3)[1]);

end_f_loop (f,t)
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boundary, define_profile, flux, specified flux, uds

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