[Pyrokrates]

Hey,


maybe a simple question but I didn´t find a answer yet.


I would like to use some global variables for which I need to loop. What I basically wanna do is this (just an simple example):

#include "udf.h"
#include <math.h>
#include <stdio.h>


const int N = 5;
 
real A[N] = {1,5,9,13,17};
real B[N];


for(int i = 0; i < N; i++)
{
    B[i] = pow(A[i],2) + i * A[i];

}

Using the line with the for loop results in following error;

error: expected identifier or '('

Question is: How can I use loops outside any function of my UDF?
Or do I need to define it with DEFINE_INIT(name,d)? If I do so (and use my initial solution for another simulation with another UDF), does Fluent keep my B[N] variables for the second simulation? Because as far as I know, the initialization is only called once for the first simulation (when klicking initialization button in GUI).


Thanks in advance


Pyro

[AlexanderZ]

code which you are going to execute should be inside fluent build in macros.
depends on when you want code to be executed you are choosing the macro:
could be DEFINE_INIT in case you want code to be executed once when you click initialize button
could be DEFINE_ADJUST in case you want code to be executed before each iteration(time step for transient)
and so on
list of macros you may find in table of contents of Fluent customization manual

for your case B[i] will be updated each time you click initialize.

[Pyrokrates]

Thank you for the answer.


I have already tied out DEFINE_INIT in past but the problem I figured out was, that If I try to use it with UDM than the initialization destroys my program...


I tried following:


1) DEFINE_INIT to set my C_UDMI(c,t,0) values
2) Using some DEFINE_PROFILE where I want to set C_PROFILE(c,t,i) = C_UDMI(c,t,0)


Problem here is like mentioned above that the initialization (standard) sets my UDM values and resets them also meaning the input for 2) is 0 everywhere...


Why I´m trying to do this is because I would like to pre define a profile for my mesh and do not update it over time... If I just set the profile inside DEFINE_PROFILE, the program recalculates the same field again and again which is a waste of time.


Any suggestions?


Thanks in advance


Pyro

[AlexanderZ]

actually you did it correct with DEFINE_INIT
most likely you forgot to allocate the memory for udm in fluent GUI

if that's not the case:
show your code, explain settings, describe errors, compile code and show log

[Pyrokrates]

Hi and thanks for your answer.


It is working now...
I didn´t see, that the DEFINE_INIT step is called after the DEFINE_PROFILE while initialization... So the init first set my UDM to zero and than at the end of init I get my values set. So the profile is zero until the first real simulation step starts.


Thanks,


Pyro