Robbie Crosby

Hi Rob, I completely understand that. Thank you for all your help so far. Would you be able to help with my code for an individual UDF for this energy source above. I have been stuck on this for the past week, and tried multiple methods but to no avail, with ANSYS crashing each time I run this as an energy source term in the porous material. 

I have attached the equation I am modelling for reference.


#include "udf.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_EXECUTE_ON_LOADING(init_values, udf_name)


    Thread *t;

    cell_t c;

    Domain *d = Get_Domain(1); // Get domain using Fluent API, assuming single-phase flow


    /* Loop over all cells to initialize UDM values */

    thread_loop_c(t, d)


        begin_c_loop_all(c, t)


            C_UDMI(c,t,UDM_RHO_F_PREV) = 1000.0;  //initializing previous rho_f

            C_UDMI(c,t,UDM_LAMBDA_PREV) = 0.0;  //initializing previous lambda


        end_c_loop_all(c, t)




DEFINE_SOURCE(energy_sourceN, c, t, dS, eqn)


  real lambda, lambda_prev, V[ND_ND], rho_f, Sl, d_lambda_dt, grad_lambda_dot_V, T, rho_f_prev;


  T = C_T(c, t);

  rho_f = C_R(c, t);

  C_CENTROID(V, c, t);


  rho_f_prev = C_UDMI(c, t, UDM_RHO_F_PREV);  // Fetch the previous value of rho_f from UDM

  lambda_prev = C_UDMI(c, t, UDM_LAMBDA_PREV);  // Fetch the previous value of lambda from UDM


  // Calculate lambda

  if (T < Tsolidus)

    lambda = 0.0;

  else if (T > Tliquidus)

    lambda = 1.0;


    lambda = (T - Tsolidus) / (Tliquidus - Tsolidus);


  // Calculate d(lambda*rho_f*L_f)/dt

  d_lambda_dt = ((rho_f * lambda * L_f * 0.85) - (rho_f_prev * lambda_prev * L_f * 0.85)) / CURRENT_TIMESTEP;


  // The gradient calculation requires more attention. Below is just a placeholder, and you need to implement the correct gradient calculation.

  grad_lambda_dot_V = (C_R_G(c,t)[0] * V[0] + C_R_G(c,t)[1] * V[1]) * lambda * L_f;


  Sl = d_lambda_dt + grad_lambda_dot_V;


  dS[eqn] = 0; // Adjust the source term linearization if necessary


  // Store the current time step values of rho_f and lambda to UDM

  C_UDMI(c, t, UDM_RHO_F_PREV) = rho_f;

  C_UDMI(c, t, UDM_LAMBDA_PREV) = lambda;


  return Sl;