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[Salil P]

Hello,

 

I am trying to simulate the Selective Laser Melting process at the mesoscale using Ansys Fluent. When writing the source term, I need to multiply it by the magnitude of the volume fraction gradient at the interface. For this, I have written the UDF given below where I store the magnitude of the volume fraction gradient in a C_UDMI using DEFINE_ADJUST and then call it in the DEFINE_SOURCE macros and assign it to the variable vf_g. If I don't call the C_UDMI in the DEFINE_SOURCE term the simulation runs without any issue and I can also visualize the C_UDMI in the contour plots, however, when I call it in DEFINE_SOURCE to multiply it with the source term, fluent simply crashes. Any errors that can be seen here? I have had the same issue regardless of the thread C_UDMI(c,t,0) wherein both the mixture domain thread and the phase thread result in fluent crashing

 

#include

#include

#include

#include

//#include

#include

#include

#include

 

#define PI 3.1415926535

#define domain_ID 3

DEFINE_ADJUST(adjust_gradient, domain)

{

    Thread *t;

    cell_t c;

    face_t f;

    domain = Get_Domain(domain_ID);

    /* Fill UDS with the variable. */

    thread_loop_c (t,domain)

    {

        begin_c_loop (c,t)

        {

            C_UDSI(c,t,0) = C_VOF(c,t);

        }

        end_c_loop (c,t)

    }

    thread_loop_f (t,domain)

    {

        if (THREAD_STORAGE(t,SV_UDS_I(0))!=NULL)

        begin_f_loop (f,t)

        {

            F_UDSI(f,t,0) = F_VOF(f,t);

        }

        end_f_loop (f,t)

    }

    domain=Get_Domain(1);

    /* Fill the UDM with magnitude of gradient. */

    thread_loop_c (t,domain)

    {

        begin_c_loop (c,t)

        {

            C_UDMI(c,t,0) = NV_MAG(C_UDSI_G(c,t,0));

        }

        end_c_loop (c,t)

    }

}

 

 

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

{

 

real current_time=CURRENT_TIME;

Thread *tp;

//parameters

real r=35e-6; // 100 micron

real P=50.0; //Power

 

Domain *subdomain;

 

    int phase_domain_index;

real v_d=0.12; 

real source;

real eta=0.5;

 

//start pos

real xs=1.5e-5+current_time*v_d;

real ys=6e-5;

// cell paramters

real x[ND_ND];

real T;

real Q;

 

real Sb;

real x1;

real y1;

    real z1;

    real vf;

real I_z;

real H_s; //

real gamma; // liq fraction 

real h; // HT coef

real T_a;

real n_fact; // normalizing factor

real Cpg;

real Cpl;

real Cpm;

real Cps;

real Cp;  // avg cell specific heat

real rho; // avg cell density

real rhog; // density of argon gas

 

real rhos; // solid density

real rhol; // liquid density

real rhom; // mixture density

 

real vf_g; //magnitude of volume fraction gradient

 

 

real s=15e-6;

 

Sb=5.67e-8;

h=25;

T_a=298;

C_CENTROID(x,c,t);

 

 

 

x1=x[0];

y1=x[1];

    z1=x[2]-5e-5+1.25e-6;

    tp = THREAD_SUB_THREAD(t,1);

    vf=C_VOF(c,tp); // get cell volume fraction

    T = C_T(c,tp); // get cell temperature

    gamma = C_LIQF(c,tp);// cell liquid fraction

    

    //Get the volume fraction gradient magnitude

    vf_g=C_UDMI(c,tp,0);

    

    //calculate mixture specific heat

    Cpg=520.64;

    Cps=462.656+0.1338*T;

    Cpl=790;

    Cpm=Cpl*gamma+Cps*(1-gamma);

    Cp=Cpm*vf+Cpg*(1-vf);

    

 

    // calculate mixture density

    rhog=1.6228;

    rhos=8000.0-800.0/1385.0*(T-273);

    rhol=6900.0-900.0/1277.0*(T-1723);

    rhom=rhol*gamma+rhos*(1-gamma);

    rho = vf*rhom + rhog*(1-vf);

 

    // calculate stabilizing factor

    n_fact=(2*rho*Cp)/(rhom*Cpm + rhog*Cpg);

 

    Q=0.23*P/(PI*r*r) * exp(-2*(pow(x1-xs,2)+pow(y1-ys,2))/pow(r,2));

 

    

    

    source=0;

    dS[eqn]=0;

if(vf>0.05 && vf<1){

        source= (Q-h*(T-T_a)-Sb*0.5*(pow(T,4)-pow(T_a,4)))*n_fact*vf_g;

    dS[eqn]=(-h-Sb*2*pow(C_T(c,tp),3))*n_fact*vf_g;

}

return source;

 

}

[Keyur Kanade]

As support we do not debug UDFs. But can provide help on particular syntex. Please check following link for details of UDF. Also if you have any subsequent questions, please post it on Ansys Forum Ansys Learning Forum under specific category.  

Chapter 1: Overview of User-Defined Functions (UDFs) (ansys.com)

Regards,

Keyur

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