Reply To: Ansys Fluent UDF: DEFINE_DPM_BC

[kiran.purushothamakeshavan]

Thanks for your reply.

The issue was that I did not build the udf from x86_x64 VS prompt. After opening fluent from Visual Studio prompt UDF seems to be loading without issues.

However, I have an issue where the particles in my model seem to not stick to the boundary. below I’ve copied the UDF for your reference.


I expected to see certain particles bounce while the rest of them to stick to the surface, here I do not see the particles bounce or stick.

 

#include “udf.h”

#include “dpm.h”

#include “math.h”

#define Rho_air 1.225  /* Air density in kg/m^3 */

#define Cd 0.47        /* Drag coefficient for a sphere */

#define mu 0.5         /* Coefficient of friction */

/* Define your boundary condition function */

DEFINE_DPM_BC(particle_bc, p, t, f, normal, dim)

{

    real V = sqrt(P_VEL(p)[0] * P_VEL(p)[0] + P_VEL(p)[1] * P_VEL(p)[1] + P_VEL(p)[2] * P_VEL(p)[2]);  /* Velocity magnitude in m/s */

    real radius = P_DIAM(p) / 2.0;

    real A = M_PI * radius * radius;  /* M_PI is a constant for π */

    /* Get the thread and cell pointers */

    Thread *t0 = P_CELL_THREAD(p);

    cell_t c0 = P_CELL(p);

    /* Get local pressure at the particle’s location */

    real P_local = C_P(c0, t0);

    /* Calculate aerodynamic force Fa */

    real Fa = 0.5 * Rho_air * A * Cd * V * V;

    /* Calculate normal force Fn */

    real Fn = P_local * A;

    /* Calculate frictional force Ff */

    real Ff = mu * Fn;

    /* Coefficient of restitution */

    real e;

    if (Fa > Ff)

    {

        /* Particle needs to bounce with a coefficient of restitution of 1 */

        e = 1.0;

        /* Update the particle velocity to simulate the bounce */

        for (int i = 0; i < dim; i++)

        {

            P_VEL(p)[i] = -e * P_VEL(p)[i];

        }

        return PATH_ACTIVE; /* No adhesion */

    }

    else

    {

        /* Particle sticks to the boundary with a coefficient of restitution of 0 */

        // e = 0.0;

        /* Update the particle velocity to simulate sticking */

        for (int i = 0; i < dim; i++)

        {

            P_VEL(p)[i] = 0;

        }

        P_USER_REAL(p, 0) = 1.;

        return PATH_ACTIVE; /* Adhesion */

    }

}

Can you please comment on the code?