[saha.vedabit]

Hello. I am trying to use a UDF to model a step function for mass flow rate at inlet of my simulation.

It is a simple case of: If the x-coordinate of the face is less than 'certain value', mass flow rate = A, otherwise, mass flow rate = B.

I am using the following UDF, but when I initialize and check my case, the entire inlet is initialized with the 94.0 Kg/s. I checked the coordinates and it seems fine. (I can initialize a velocity step function using the same coordinates without any issues, using the same code below (changing inlet_mf to inlet_z_velocity)).

I know I can simply divide the face into multiple faces for a step function inlet like this, and specify the mass flow rates separately, but I am practising writing UDFs, so I was hoping if someone would kindly guide me with what I am doing wrong? Thank you.

UDF:

#include "udf.h"
DEFINE_PROFILE(inlet_mf, thread, position)
{
real x[ND_ND];
real x0;
face_t f;
begin_f_loop(f, thread)
{
F_CENTROID(x,f,thread);
x0 = x[0];
if (x0 < 27.65)
F_PROFILE(f, thread, position) = 212.0;
else
F_PROFILE(f, thread, position) = 94.0;
}
end_f_loop(f, thread)
}

[AlexanderZ]

code seems to be correct,
by default fluent uses SI
so meters for x[0]
are you sure 27.65 is correct value?

[saha.vedabit]

Originally Posted by AlexanderZ

code seems to be correct,
by default fluent uses SI
so meters for x[0]
are you sure 27.65 is correct value?

Thank you for your reply. Yes, I tried initializing a velocity field at inlet with the same code just by changing inlet_mf to inlet_z_velocity and speicifying the cartesian velocity at inlet using udf. It is working fine in that case.

I wonder why mass flow rate can't be initialized. Does it have a different associated macro or variable that I am supposed to use?