Here is a sample UDF code for the k-e-v2-f turbulence model in ANSYS Fluent:

This code defines a UDF for the k-e-v2-f turbulence model in ANSYS Fluent. The UDF computes the turbulent kinetic energy (k), the turbulent dissipation rate (eps), and the second moment of the velocity fluctuations (v2). It also computes the turbulent viscosity (mu_t) and the constants C1, C2, and C3, which are used to compute the wall function values of epsilon and f. The UDF then sets the values of k, epsilon, and f in the turbulent and laminar regions of the flow, and updates these values in the solver.

#include "udf.h"

/* User-defined function to define the k-e-v2-f turbulence model */

DEFINE_K_EPSILON(k_e_v2_f, c, t, dS, eqn) { real k, eps, f; real v2, S; real mu; real rho; real Cmu, C1, C2, C3; real sigma_k, sigma_e, sigma_f; real f_wall, eps_wall;

/* Compute the turbulent kinetic energy (k) and the turbulent dissipation rate (eps) */

k = C_K(c, t); eps = C_EPSILON(c, t);

/* Compute the second moment of the velocity fluctuations (v2) and the turbulent strain rate (S) */

v2 = 2.0k/3.0; S = sqrt(2.0k)/C_MU(c, t);

/* Compute the turbulent viscosity (mu_t) */

mu = C_MU(c, t); rho = C_R(c, t); Cmu = 0.09; mu_t = rhoCmukeps/(muS);

/* Compute the constants C1, C2, and C3 */

C1 = 1.44; C2 = 1.92; C3 = 1.0;

/* Compute the wall function values of epsilon and f */

eps_wall = C2sqrt(k)pow(C_DIST(c, t), 2.0/3.0); f_wall = C3(1.0 - exp(-C1pow(C_DIST(c, t), 1.5)));

/* Compute the constants sigma_k, sigma_e, and sigma_f */

sigma_k = 1.0; sigma_e = 1.3; sigma_f = 1.0;

/* Set the values of epsilon and f at the wall */

if (C_DIST(c, t) < 1.0e-10) { eps = eps_wall; f = f_wall; }

/* Set the values of k and epsilon in the turbulent region */

else { k = sigma_kmu_tfv2/(epsC_MU(c, t)); eps = sigma_emu_tfv2/(kC_MU(c, t)); }

/* Set the value of f in the turbulent region */

f = sigma_fmu_tfv2/(kC_MU(c, t));

/* Set the values of k and epsilon in the laminar region */

if (S < 1.0e-10) { k = 0.0; eps = 0.0; }

/* Update the values of k and epsilon in the solver */

dS[eqn] = 1.0; C_K(c, t) = k; C_EPSILON(c, t) = eps; }