Learning Forum

[Robbie Crosby]

Hello, I am trying to create a UDF to fit a numerical model which must be applied as UDFs in ANSYS Fluent to model a phase change material in a porous medium. I have attached the mathematical model I am trying to follow as well as my current code. I am currently stuck on getting the interstitial heat transfer coefficient to come up as a UDF, that can be selected in ANSYS Fluent, for the non-equilibrium model of porous medium. Any help would be greatly appreciated. Should it be define_profile or define_property

#include "udf.h"

#include "mem.h"

#define Tsolidus 300.0

#define Tliquidus 304.0

#define L_f 250 //Latent heat of fusion

 

#define UDM_RHO_F_PREV 0  // UDM index for storing previous rho_f

#define UDM_LAMBDA_PREV 1  // UDM index for storing previous lambda

 

DEFINE_PROFILE(h_sfq, c, t)

{

    real dl, epsilon, mu, nu, pr, rho_pcm, u, v, mu_pcm, k_pcm, Re_d, h_sfq, local_h_sfq;

    cell_t cell;

 

    dl = 0.0194; //Diameter Matlab

    epsilon = 0.85; //Porosity Matlab

    mu = C_MU_L(c, t);        // Laminar viscosity

    rho_pcm = C_R(c, t);          // Density

    nu = mu/rho_pcm;             // Kinematic Viscosity

    pr = nu/rng_alpha(1., mu, mu); // Prandtl Number

 

    u = C_U(c, t);

    v = C_V(c, t);

    mu_pcm = C_MU_L(c ,t);

    k_pcm = C_K_L(c, t);

 

    Re_d = (rho_pcm * sqrt(u*u + v*v) *dl) / (epsilon * mu_pcm);

 

    if (Re_d > 0 && Re_d <= 40)

        local_h_sfq = (0.76 * pow(Re_d, 0.4) * pow(pr, 0.37) * k_pcm)/dl;

    else if (Re_d > 40 && Re_d <= 1000)

        local_h_sfq = (0.52 * pow(Re_d, 0.5) * pow(pr, 0.37) * k_pcm)/dl;

    else if (Re_d > 1000 && Re_d <= 20000)

        local_h_sfq = (0.26 * pow(Re_d, 0.6) * pow(pr, 0.37) * k_pcm)/dl;

    else

   

    return local_h_sfq;

}

[Atharva Nagarkar]

Hello,

The DEFINE_PROFILE macro is used to define a custom boundary profile or cell zone condition that varies as a function of spatial coordinates or time while you can use the DEFINE_PROPERTY to specify a custom material property in Ansys Fluent for single-phase and multiphase flows. Based on this, the DEFINE_PROPERTY macro would be more suited for your use.

Please find the links from the Ansys UDF Manual related to both these macros. Check sections 2.3.29 and 2.3.30. I would also request you to have a look at the examples given below these sections to understand the use of these DEFINE macros.

2.3. Model-Specific DEFINE Macros (ansys.com)

If you are not able to access the link, please refer to this forum discussion: Using Help with links (ansys.com)

Thanks!