[shiju7279]

I am trying to implement the following udf for a simple straight tube model that has laminar flow within it. The desired objective here is to have a flow within the pipe, that is dependent on the downstream resistance. This resistance affects the outlet pressure (P2=resistance*outlet flow). The udf is expected to do this job. However, I am not achieving what I should get.
The inlet pressure is set at 95 mm Hg while the outlet pressure is dependent on this downstream resistance and so this udf is prescribed at the outlet.

I am not sure where I am going wrong. Firstly I get a segmentation error during initialization. To avoid that I do initialization without the udf and while running it I reattach it. I know it is not a brilliant way but just want to see it working. Secondly, my outlet pressure and the mass flow rate always remains zero. I tried implementing lot of modifications on it but all seems to fail. Can you kindly help me with this.

#include "udf.h"

DEFINE_INIT(my_init_func)
{
Domain *domain = Get_Domain(1);
Thread *thread = Lookup_Thread(domain,11);
face_t f;
begin_f_loop(f, thread)
{
F_UDMI(f,thread,0) = 0;
}
end_f_loop(f, thread)
printf("Step Pressure Initialized!");
}

DEFINE_PROFILE(transient_pressure, thread, position)
{
real Res = 7.0e+08; /* Resistance m^-4 s^-1 kg^1 */
face_t f;
float flow, pout, pprev;
real dens = 1050; /* kg m^-3 */


begin_f_loop(f, thread)
{
flow = F_FLUX(f,thread)/dens;
pout = Res*flow;
F_PROFILE(f, thread, position) = pout;
}
end_f_loop(f, thread)

}


DEFINE_EXECUTE_AT_END(pressure_save)
{
Domain *domain = Get_Domain(1);
Thread *thread = Lookup_Thread(domain,11);
face_t f;
begin_f_loop(f, thread)
{
F_UDMI(f,thread,0) = F_P(f,thread);
}
end_f_loop(f, thread)
printf("Step Pressure Recorded!");
}

[AlexanderZ]

Originally Posted by shiju7279

I am trying to implement the following udf for a simple straight tube model that has laminar flow within it. The desired objective here is to have a flow within the pipe, that is dependent on the downstream resistance. This resistance affects the outlet pressure (P2=resistance*outlet flow). The udf is expected to do this job. However, I am not achieving what I should get.
The inlet pressure is set at 95 mm Hg while the outlet pressure is dependent on this downstream resistance and so this udf is prescribed at the outlet.

I am not sure where I am going wrong. Firstly I get a segmentation error during initialization. To avoid that I do initialization without the udf and while running it I reattach it. I know it is not a brilliant way but just want to see it working. Secondly, my outlet pressure and the mass flow rate always remains zero. I tried implementing lot of modifications on it but all seems to fail. Can you kindly help me with this.

#include "udf.h"

DEFINE_INIT(my_init_func)
{
Domain *domain = Get_Domain(1);
Thread *thread = Lookup_Thread(domain,11);
face_t f;
begin_f_loop(f, thread)
{
F_UDMI(f,thread,0) = 0;
}
end_f_loop(f, thread)
printf("Step Pressure Initialized!");
}

DEFINE_PROFILE(transient_pressure, thread, position)
{
real Res = 7.0e+08; /* Resistance m^-4 s^-1 kg^1 */
face_t f;
float flow, pout, pprev;
real dens = 1050; /* kg m^-3 */


begin_f_loop(f, thread)
{
flow = F_FLUX(f,thread)/dens;
pout = Res*flow;
F_PROFILE(f, thread, position) = pout;
}
end_f_loop(f, thread)

}


DEFINE_EXECUTE_AT_END(pressure_save)
{
Domain *domain = Get_Domain(1);
Thread *thread = Lookup_Thread(domain,11);
face_t f;
begin_f_loop(f, thread)
{
F_UDMI(f,thread,0) = F_P(f,thread);
}
end_f_loop(f, thread)
printf("Step Pressure Recorded!");
}

Hello

you may try to use this code for initialization part:

DEFINE_INIT(my_init_func)
{
Thread *t;
face_t f;
Domain *d;
d = Get_Domain(1);
t = Lookup_Thread(domain,11);
thread_loop_f(t, domain)
{
begin_f_loop(f,t)
{
F_UDMI(f,thread,0) = 0;
}
end_f_loop(f, t)
}
printf("Step Pressure Initialized!");
}

Also I'm suggesting you to add UDMs to control your profile input, for instance add F_UDMI(f,thread,1) = pout; before F_PROFILE(f, thread, position) = pout;

In this way you may see your input data using contours.

Best regards