[msd]

Hello!

I am trying to write 2 UDFs in a single simulation:
1. Unsteady velocity profile at the inlet.
2. Calculation of flow rate at the outlet and further calculation of pressure from this by a relation.

The UDF goes as follows:
#include "udf.h"

#define R 12000 /*Value taken from literature*/

DEFINE_PROFILE (unsteady_velocity, thread, position)
{
face_t f;
real t = CURRENT_TIME;
begin_f_loop (f, thread)
{
F_PROFILE (f, thread, position) = -0.086*(sin(7.54*t + 0.609)) + 0.0075;
}
end_f_loop (f, thread)
}


#include "mem.h"
#include "metric.h"
DEFINE_PROFILE(outlet_pressure, thread, position)
{
real A[ND_ND];
face_t f;
Thread *t;
real At, Vx;

begin_f_loop(f, thread)
{
F_AREA(A, f, thread);
At = NV_MAG(A); /* Used for the computation of the magnitude of the area vector */
Vx = F_U(f, thread);
F_PROFILE(f, thread, position) = R*Vx*At;
}
end_f_loop(f, thread)
}

The UDF is getting interpreted correctly but solution initialization gives me the following message:
Error:
C:\PROGRA~1\ANSYSI~1\v145\fluent\fluent14.5.0\win6 4\3ddp\fl1450s.exe received fatal signal (ACCESS_VIOLATION)
1. Note exact events leading to error.
2. Save case/data under new name.
3. Exit program and restart to continue.
4. Report error to your distributor.
Error Object: #f

I am not able to figure out the error. Can someone please help with this?

TIA!

[pakk]

Locate the problem. It is in one of your UDFs. Which one? Just try! Disable one, see if the problem is still there.

Once you know which UDF is the problem, try a similar approach to find which part of the UDF is the problem.

I don't see real problems in your code.

[msd]

Thank you for your reply.

Actually, I tried figuring out the problem and I came to know that the problem lies in the second UDF. Because if I am disabling the second UDF, the solution is getting initialized. But I am not able to figure out what is the exact error in that. Can you please tell what can be the possible errors, as I am quite new to coding and writing UDFs.

Thanks in advance!

[pakk]

You read the velocity, which is not at set yet.

Solution: initialize without UDFs, then apply UDFs and run.

[msd]

Thank you so much for your help. It's working now!

[msd]

Can you please help me with this?

I am attaching the pressure and volumetric flow rate waveforms along. I am not able to understand why pressure is getting zero when the flow rate is negative. Ideally, according to the relation pressure should not be zero when flow rate is negative. Can you please tell is there some logical error in the code?

Thanks in advance!

[msd]

Sorry, by mistake I attached pressure waveform twice.

[pakk]

Nevermind...

[pakk]

I can't find an explanation for this, I'm sorry.

[msd]

Okay, thanks for your time!