[TheOneBird]

Hello Everyone,
I have a mixture with a number of fluids in it. I am confused about how I would write a UDF such as to vary these mass fractions of individual fluids across the inlet [edit: with position from the axis, I am running axi-symmetric].

Thanks!

[Bruno Machado]

Originally Posted by TheOneBird

Hello Everyone,
I have a mixture with a number of fluids in it. I am confused about how I would write a UDF such as to vary these mass fractions of individual fluids across the inlet.

Thanks!

you gotta be more specific about what you want to do, otherwise we can not help. vary it based on what? time? temperature? pressure? position?

In a inlet boundary you can define the mass fraction of your species as a constant or depending on what you other variables you want to consider through UDF.

[TheOneBird]

Thank you for your answer Bruno,

Sorry my bad - must be my super lack of sleep.

Varied based on position from the axis. I am running axi-symmetric. It is a steady state,S-A model.

So all of my species are calculate through CEA. At the moment I am just trying for a simple step function.

massFraction(O2) = 0.1 for 0<= y <0.2,
massFraction(O2) = 0.4 for 0.2<= y <end

Thank you so much!

[Bruno Machado]

Originally Posted by TheOneBird

Thank you for your answer Bruno,

Sorry my bad - must be my super lack of sleep.

Varied based on position from the axis. I am running axi-symmetric. It is a steady state,S-A model.

So all of my species are calculate through CEA. At the moment I am just trying for a simple step function.

massFraction(O2) = 0.1 for 0<= y <0.2,
massFraction(O2) = 0.4 for 0.2<= y <end

Thank you so much!

This is an example of profile for mass fraction. You can add the macro F_CENTROID(x,f,t) for the position and create your if conditions.

DEFINE_PROFILE(mass_fraction,t,i)
{
face_t f;
double Y_O2;

Y_O2 = 1.0;

begin_f_loop(f,t)
{
F_PROFILE(f,t,i) = Y_O2;
}
end_f_loop(f,t)
}

[TheOneBird]

That looks good! Thank you Bruno Machado!