We have an exciting announcement about badges coming in May 2025. Until then, we will temporarily stop issuing new badges for course completions and certifications. However, all completions will be recorded and fulfilled after May 2025.

Ansys Learning Forum › Forums › Discuss Simulation › Fluids › Initialization Error – Droplet Evaporation › Reply To: Initialization Error – Droplet Evaporation

February 28, 2023 at 11:56 am
Sidharth_Raut
Subscriber

Hello Rob,

I'm having UDM in my UDF but it doesn't give me any value since the case is not even getting initialized. Can you have a good look at my UDF and let me know where I'm wrong? Also, I'm trying to run this in parallel with 4 processors. I'm sharing my actual code here.

Also, is there a way that my udf is causing a cell or value or something similar that doesn't exist is getting written to and Fluent then crashes??  

/********************************************************
 DEFINITION OF MASS SOURCE TERM FOR LIQUID PHASE
 *******************************************************/

DEFINE_SOURCE(liq_src, c, t, ds, eqn)
{
   #if !RP_Host
   
   real m_dot_l, T_sat;
   real vol = C_VOLUME(c, t);                                                                           //SIGNIFIES THE CELL VOLUME FOR A CELL AND THREAD
   Thread *pt = THREAD_SUB_THREAD(t, 0);                                                                //PRIMARY PHASE THREAD
   Thread *st = THREAD_SUB_THREAD(t, 1);                                                                //SECONDARY PHASE THREAD

   if (C_VOF(c, t) < 0.99 && C_VOF(c, t) > 0.01)
   {
    if (C_T(c,pt) >= T_sat)
    {
        m_dot_l = -0.1 * C_VOF(c,t) * C_R(c,t) * fabs(C_T(c,t) - T_sat) / T_sat;                      //LEE EVAPORATION MODEL
        ds[eqn] = -0.1 * C_R(c,t) * fabs(C_T(c,t) - T_sat) / T_sat;
    }
    else
    {
        m_dot_l = 0.1 * C_VOF(c,st) * C_R(c,st) * fabs(T_sat - C_T(c,pt)) / T_sat;                    //LEE CONDENSATION MODEL
        ds[eqn] = 0;
    }
   }
   else
   {
    m_dot_l = 0;
    ds[eqn] = 0;
   }

   C_UDMI(c, t, 9) = m_dot_l;
   return m_dot_l;
   
    #endif
}

/********************************************************
 DEFINITION OF MASS SOURCE TERM FOR VAPOR PHASE
 *******************************************************/

DEFINE_SOURCE(vap_src, c, t, ds,eqn)
{
    #if !RP_Host
       
   real m_dot_v, T_sat;
   real vol = C_VOLUME(c, t);                                                                           //SIGNIFIES THE CELL VOLUME FOR A CELL AND THREAD
   Thread *pt = THREAD_SUB_THREAD(t, 0);                                                                //PRIMARY PHASE THREAD
   Thread *st = THREAD_SUB_THREAD(t, 1);                                                                //SECONDARY PHASE THREAD

   if (C_VOF(c,t) < 0.99 && C_VOF(c,t) > 0.01)
   {
    if (C_T(c,pt) >= T_sat)
    {
        m_dot_v = 0.1 * C_VOF(c,t) * C_R(c,t) * fabs(T_sat - C_T(c,pt)) / T_sat;                       //LEE CONDENSATION MODEL
        ds[eqn] = 0;
    }
    else
    {
        m_dot_v = -0.1 * C_VOF(c,t) * C_R(c,t) * fabs(T_sat - C_T(c,pt)) / T_sat;                      //LEE CONDENSATION MODEL
        ds[eqn] = -0.1 * C_R(c,t) * fabs(T_sat - C_T(c,t)) / T_sat;
    }
   }
   else
   {
    m_dot_v = 0;
    ds[eqn] = 0;
   }

   C_UDMI(c, t, 10) = m_dot_v;
   return m_dot_v;
   
    #endif
}

/********************************************************
 DEFINITION OF ENERGY SOURCE TERM FOR BOTH PHASES
 *******************************************************/

DEFINE_SOURCE(enrg_src, c, mix_th, ds, eqn)
{
    #if !RP_Host
   
    real m_dot, T_sat, hfg;
    Thread *pt, *st;
    pt = THREAD_SUB_THREAD(mix_th, 0);
    st = THREAD_SUB_THREAD(mix_th, 1);

    if (C_VOF(c, pt) < 0.99 && C_VOF(c, pt) > 0.01)
    {
        if (C_T(c, mix_th) >= T_sat)
        {
            m_dot = -0.1 * C_VOF(c,pt) * C_R(c,pt) * fabs(C_T(c,pt) - T_sat) / T_sat;                      //LEE EVAPORATION MODEL
            ds[eqn] = -0.1 * C_VOF(c,pt) * C_R(c,pt) / T_sat;
        }
    }
    else
    {
        m_dot = 0.1 * C_VOF(c,st) * C_R(c,st) * fabs(T_sat - C_T(c,mix_th)) / T_sat;                      //LEE CONDENSATION MODEL
        ds[eqn] = -0.1 * C_VOF(c,st) * C_R(c,st) / T_sat;
    }
    else
    {
        m_dot = 0;
        ds[eqn] = 0;
    }
   
    C_UDMI(c, t, 11) = m_dot;
    return hfg * m_dot;
   
    #endif
}

Â