[borhan_sd@yahoo.com]

Hi all ,I’m new in fluent and particularly UDF, I want to model a system that a gas is inlet and it flows for 3s and doesn’t flow for 3s alternatively and continuously. In fact it’s our respiration flow and the model is a respiratory mask.
How should I write UDF file? Probably CURRENT_TIMESTEP Macro should be used, Is it right?
Would you tell me please how should I write the UDF? This is very important for me.
Thank you very very much in advance.

[blackmask]

Something looks like

#include "udf.h"

DEFINE_PROFILE(vel_in, thread, i)  {
    real y;
    face_t f;
    real t = CURRENT_TIME;
    int off = (int) (t/0.03+0.5) %2;
    
    begin_f_loop(f,thread)
    {
        if (!off)
            F_PROFILE(f,thread,i) = 1.0;
    }
    end_f_loop(f,thread)
}

Modify it to suit your needs.

[borhan_sd@yahoo.com]

thank you very much for your quick reply

regards