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droberts June 29, 2010 08:05

Transient pressure UDF for parallel fluent
1 Attachment(s)

I am trying to model resonance of a pipe using Fluent. In order to do this I am driving the flow with a transient pressure on one boundary using a UDF. I have managed to get this to work as a serial process, however I am now scaling up the grid and require this to run on a parallel system. Please can some one let me know how I can adapt the UDF below to run in parallel?

I have included the output from fluent in the attachment to show the error messages.

************************************************** ********
#include "udf.h" /* must be at the beginning of every UDF you write */

DEFINE_PROFILE(unsteady_pressure, thread, position)
face_t f;
real t = CURRENT_TIME;

begin_f_loop(f, thread)
F_PROFILE(f, thread, position) = 3362*cos(6.28318531*1000*t); /*P=Acos(2pi*f*t)*/
end_f_loop(f, thread)
************************************************** ********

Thanks for any help.

dmoroian June 29, 2010 11:17

You seem to use an interpreted udf.
There are few limitations when running interpreted udf's, so I suggest to compile it first.
By the way, I suspect that line 1 in your source is not "**************", because that would always result in a syntax error.

Shamoon Jamshed October 10, 2010 09:05

UDF pressure
Hi, I also want to use the udf for pressure but the problem is that i dont have formula for it rather i have data at different time steps. How can I manage this data of pressure in the UDF? I have data of pressure like that

080000 and so on

dmoroian October 10, 2010 10:39

I think the simplest way would be to use a linear interpolation between your data and the CURRENT_TIME.

Shamoon Jamshed October 10, 2010 12:13

I didn't get your point, how come we can do this in UDF. Doesn't it require formula?

dmoroian October 11, 2010 04:13

Yes, you are right, you will need a formula.
An interpolation will give you that formula, for any set of discrete data.
I suggested a linear interpolation (spline linear interpolation - just to keep it simple).
Put that interpolation inside DEFINE_PROFILE, and you're done!

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