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Non-eq. porous model

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Old   August 10, 2020, 13:41
Default Non-eq. porous model
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Franz Roman
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Hello,
I have a problem with the non-eq. porous medium. To calculate the heat transfer coefficient between the solid material in the porous zone and the air I want to use a user defined profile. I want to access the air properties like density, specific heat, thermal conductivity and viscosity, and also the velocity magnitude in each element of the porous zone, from within the UDF. I included some UDMs to store the values of these variables and check that they are correct, and I saw that the density and the viscosity of the fluid agree with the set up in the Materials Panel, but for specific heat and thermal conductivity the UDMs have values of almost zero (i.e. -1.42e37), although in the Materials Panel they have correct constant values. Also, the velocity is displayed as uniform at 1.0 m/s in a plane through the porous media, although the contours of velocity magnitude show a variable velocity, which had been calculated previously. The UDF is below, it seems ok to me. Or is accessing some variables not allowed from withing a DEFINE_PROFILE?
Another issue is that, when Fluent created the solid porous zone, the two open faces of the porous zone (though which air could go in and out) were converted to walls, and it is not possible to convert them to interior. I would appreciate some assistance.


#include "udf.h"
/* Heat and moisture transfer in tomato cooling */
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
#define dp 0.07
#define porosity 0.44
DEFINE_PROFILE(heat_transf_coeff,t,i)
{
real rho_air, mu, k_air, cp_air, va, Re, Pr, Nu, ht;
cell_t c;


begin_c_loop(c,t)
{
rho_air = C_R(c,t);
mu = C_MU_L(c,t);
k_air = C_K_L(c,t);
cp_air = C_CP(c,t);
va = pow(pow(C_U(c,t),2) + pow(C_V(c,t),2) + pow(C_W(c,t),2),(1/2)); /* velocity magnitude at cell */


Re = (va/porosity)*dp/(mu/rho_air);
Pr = mu*cp_air/k_air;
Nu = 2.0 + 0.552*pow(Re, 0.53)*pow(Pr, 0.33);
ht = Nu*k_air/dp;


C_UDMI(c,t,0) = rho_air;
C_UDMI(c,t,1) = mu;
C_UDMI(c,t,2) = k_air;
C_UDMI(c,t,3) = cp_air;
C_UDMI(c,t,4) = va;

F_PROFILE(c,t,i) = ht;
}
end_c_loop(c,t)
}
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non-equilibrium thermal, porous medium, udf

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