Hi Philipp,

interesting project :). From my point of view, the subroutine you implemented in Matlab should be easily transferred into a UDF, especially if you use the third option given in the attached pseudo UDF. My advice would be to go through the examples in the manual. There is a special chapter for programming UDFs. You should hereby also consider the parallelization of your UDF, which could make things very complicated in case you need a lot of communication or synchronization of the computational nodes. However, the task is surely doable.

Since you didn't use the Solidification and Melting option, I am wondering if you considered the amount of latent heat of fusion. Depending on the material this will be not negligible. One way to do that would be to use the apparent heat capacity approach.

Best of luck!

Antoni Artinov

Hi there,

thank you very much for your response Antoni Artinov , you certainly motivated me to try implementing the udf!!

So first i´d like to point out that i followed given examples from the udf-manual and cfd-related forums. I came past the compilation of my code. Now scince youve already mentioned the parallelization complications i wonder if you can help me at my current state.

I will briefly explain the way i implemented my idea:

1. Im working with a simple model to test udfs consisting of two rows of pipes with a cutting plane in between - to measure flow temperature coming at the top pipe row. (reminder: i have a function fit for the pipe surface temperature, dependent on gas temperature and percentage of hardened pcm (PHI))

2. the first udf uses the execute_at_end macro to calculate the current PHI-Values and print it to a txt file as memory.

3. the second udf (used twice with a different name) uses a define_profile macro to set the boundary temperature of the pipe-rows. It reads the corresponding Phi.txt file and gets the gas-temperature by calculating the average temperature at the corresponding cutting plane.

So i have a working model wich i tested in a transient simulation using constant boundary conditions. (btw: ive done this twice- for parallel + double precision; and serial + No dp)

After compiling, i can hook the first udf as execute_at_end. As soon as i set the second udf as boundary condition for one of the pipe-rows i get error messages in the TUI, aswell as graphical bugs in the initialization and run-calculation windows. I will attach the fully commented code.

The error i´m getting reads (latest run in serial) :

1. Node 0: Process 9896: Received signal SIGSEGV.

2. Error: Cortex received a fatal signal (SEGMENTATION VIOLATION). Error Object: ()

3. 999999: mpt_accept: error: accept failed: No such file or directory

4. The fl process could not be started.

There is also a .txt file appearing stating most notably:

5.Node 0 Fatal signal raised sig = Segmentation fault

Do you know hot to resolve this problem? I started fluent2020 via the VS2019 command prompt -> loaded the mesh data via file->read->mesh -> did the setup and tested it -> compilled my source files -> hooked 1.st udf -> set 2.nd as bounday condition -> error.

Thank you again Antoni for the motivation now i really want so see if my udfs work. I would appreciate your help verry much!!

P.S. as you mentioned the latent heat : it yould be possible to adjust the total energy reservoir after succesful implementation.

Greetings from Wuppertal :)

Check the tutorial and udf examples.

Regards