[eldhosek1987@gmail.com]

I want to give variable mass flow inlet conditions for two components-Hydrogen and Helium in a mixture with respect to time. Initially, ONLY Hydrogen at a constant mass flow rate enters through the inlet for some specific time and after that ONLY Helium at a different constant mass flow rate enters. I have written a UDF for this condition. Though I am able to hook the UDF to the mass flow inlet boundary condition, the mass flow rates are not captured properly at the mass flow inlet. Only the initial mass flow rate is showing at the inlet and it is not changing thereafter. Mass flow rates are not changing accordingly with the given mass fraction conditions.

Expecting somebody's help on this.

The UDF goes like this...


#include "udf.h"
DEFINE_PROFILE(mixture_inlet_mass_flow_rate, t, nv)
{
face_t f ;
real flow_time = RP_Get_Real("flow-time");
if (flow_time < 0.005)
{
printf("Time = %f sec. \n",flow_time);
printf("Targeted mass-flow rate set at 0.001 kg/s \n");
begin_f_loop(f,t)
{
F_PROFILE(f,t,nv) = 0.001 ;
}
end_f_loop(f,t)
}
else
{
printf("Time = %f sec. \n",flow_time);
printf("Targeted mass-flow rate set at 0.002 kg/s \n") ;

begin_f_loop(f,t)
{
F_PROFILE(f,t,nv) = 0.002 ;
}
end_f_loop(f,t)
}

}

DEFINE_PROFILE(mixture_inlet_profile, t)
{
real time = CURRENT_TIME;
real X_H2, X_He;

if (time<0.005)
{
X_H2 = 1 ;
X_He = 0 ;

}

else if (t>0.005)
{
X_H2 = 0 ;
X_He = 1 ;

}

if (i == 0)
{
F_PROFILE(f, t, i) = X_H2;
}
else if (i == 1)
{
F_PROFILE(f, t, i) = X_He;
}

}

[eldhosek1987@gmail.com]

Originally Posted by eldhosek1987@gmail.com

I want to give variable mass flow inlet conditions for two components-Hydrogen and Helium in a mixture with respect to time. Initially, ONLY Hydrogen at a constant mass flow rate enters through the inlet for some specific time and after that ONLY Helium at a different constant mass flow rate enters. I have written a UDF for this condition. Though I am able to hook the UDF to the mass flow inlet boundary condition, the mass flow rates are not captured properly at the mass flow inlet. Only the initial mass flow rate is showing at the inlet and it is not changing thereafter. Mass flow rates are not changing accordingly with the given mass fraction conditions.

Expecting somebody's help on this.

The UDF goes like this...


#include "udf.h"
DEFINE_PROFILE(mixture_inlet_mass_flow_rate, t, nv)
{
face_t f ;
real flow_time = RP_Get_Real("flow-time");
if (flow_time < 0.005)
{
printf("Time = %f sec. \n",flow_time);
printf("Targeted mass-flow rate set at 0.001 kg/s \n");
begin_f_loop(f,t)
{
F_PROFILE(f,t,nv) = 0.001 ;
}
end_f_loop(f,t)
}
else
{
printf("Time = %f sec. \n",flow_time);
printf("Targeted mass-flow rate set at 0.002 kg/s \n") ;

begin_f_loop(f,t)
{
F_PROFILE(f,t,nv) = 0.002 ;
}
end_f_loop(f,t)
}

}

DEFINE_PROFILE(mixture_inlet_profile, t)
{
real time = CURRENT_TIME;
real X_H2, X_He;

if (time<0.005)
{
X_H2 = 1 ;
X_He = 0 ;

}

else if (t>0.005)
{
X_H2 = 0 ;
X_He = 1 ;

}

if (i == 0)
{
F_PROFILE(f, t, i) = X_H2;
}
else if (i == 1)
{
F_PROFILE(f, t, i) = X_He;
}

}

hey guys,
I have got the correct udf for this condition. I have defined two profiles separately for Hydrogen and Helium and applied the boundary condition separately in the mass flow inlet. When you are defining different profiles with specific names under the same"udf.h", that profiles appear separately with those names in the boundary conditions upon interpreting. Then we can hook it to the corresponding species in the mixture.

The udf goes like this.....


#include "udf.h"

DEFINE_PROFILE(mixture_inlet_profile_Hydrogen, thread, position)
{
face_t f;
real time = CURRENT_TIME; // Get the current simulation time

real mass_flow_rate_H2 = 0.001; // Constant mass flow rate for Hydrogen (kg/s)

begin_f_loop(f, thread)
{
if (time < 0.005)
{
// Hydrogen enters with a specified mass flow rate
F_PROFILE(f, thread, position) = mass_flow_rate_H2;

}
else
{
F_PROFILE(f, thread, position) = 0;

}
}
end_f_loop(f, thread)

}

DEFINE_PROFILE(mixture_inlet_profile_Helium, thread, position)
{
face_t f;
real time = CURRENT_TIME; // Get the current simulation time

real mass_flow_rate_He = 0.002; // Constant mass flow rate for Helium (kg/s)

begin_f_loop(f, thread)
{
if (time < 0.005)
{

F_PROFILE(f, thread, position) = 0;

}
else
{
// Helium enters with a specified mass flow rate
F_PROFILE(f, thread, position) = mass_flow_rate_He;

}
}
end_f_loop(f, thread)

}


Hope it helps someone.....