[Sarah_Fluent]

Hello everybody,

I'm quite new to parallel processing.
I am considering a coil that is heated and flowed through by water. The heat sources are transfered by UDF's.

In the past, I always used serial processing to compute my model, so in batch mode, my command line was:

fluent 3ddp -gu -i modell.txt

In this serial modelling process, the model and the results are fine. Now, I tried to calculate in parallel processing by using the following batch command line:

fluent 3ddp -gu -t8 -i modell.txt


The results by doing parallel processing are completely wrong. The heat sources are spreaded and not where they actually are.

Does someone have an idea what's wrong here?


Best regards
Sarah

[LuckyTran]

Most likely it has everything to do with your UDF.

also try
fluent 3ddp -gu -t1 -i modell.txt

which is parallel with 1 process and see if this gives results similar to your serial run or if everything is still broken. What version of Fluent are you using? In the newest (and some next-to-newest) versions there is no longer a serial mode.

[Sarah_Fluent]

Hello LuckyTran,

thank you for your reply. I have tried

fluent 3ddp -gu -t1 -i modell.txt

but the results are still wrong.
I am running Fluent version 15.0.

Attached is a screenshot of the starting process where it is stated, that a password is not set.
Does this maybe have something to do with this behaviour?

You explained that a UDF might be the problem. So I am thinking about how this can be the case, so there must be some different processing approach in serial and parallel processing.


Best regards
Sarah

[LuckyTran]

The cache password is because you are using platform MPI and this is normal to see this message if you do not have a password cached.

So you have confirmed more-or-less that it is a parallel environment error.

UDF's are either interpreted or compiled at runtime and lots of things can go wrong. What does your UDF do exactly?

[Sarah_Fluent]

Thank you for your explanation.

My UDF's are all interpreted.

I have a couple of UDF's in my program which I use for transfering the heat sources of my electromagnetical model and for exporting the temperatures back.

I made some simulation tests and found out, that some of my UDF's are responsible for this strange behaviour, not only one. But I guess if I understand it for one UDF, I can solve this problem also for the other UDF's.


I made now a simulation where everything is 20 °C so there is only the heat_sources_udf active, which is stated below:


#define lines3 651296
float array3[lines3];

DEFINE_SOURCE(heat_source_coil,cell,thread,dS,eqn)
{
real x[ND_ND];
real source = 0.;

C_CENTROID(x,cell,thread);
dS[eqn] = 0;

source=array3[cell];

return source;
}

With this UDF, I import the heat sources of my electromagnetical model to my Fluent model.
This UDF works fine with serial processing but not with parallel processing.

Do you know what might be wrong there?

Best regards
Sarah

[Sarah_Fluent]

I forgot to mention my initialization file which imports my electromagnetical results from the file elmat.text:



DEFINE_INIT(init_inductor,domain)
{
FILE *hs3;
int n;
real x[ND_ND];
real source = 0.;

hs3=fopen("elmat.txt","r");

for (n=0;n<lines3;n++)
{
fscanf(hs3,"%g",&array3[n]);
}
fclose(hs3);
}



Best regards
Sarah