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Old   June 6, 2003, 07:05
Default UDF to read and write data
  #1
Mcgregor
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Hi,

Does anyone know how i should go about including a section in a UDF that reads an entire data file once certain conditions are reached.

I monitor the temperature at a point throughout a simulation and once that temperature reaches a certain value, i want to read in another data file without having to be at my computer to reinitialise.

Any ideas? All help will be gratefully received

Andy
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Old   June 6, 2003, 14:14
Default Re: UDF to write data
  #2
Alex Munoz
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Hi

Follow this pice of code that I wrote for this purposes. Keep in mind that fluent does not allow you to write the filename on your screen therefore you must to change the filename on this C-code, also you have to store that information on a UDM or UDS

Do not forget to request in fluent one or more than one UDM memory. (I don't know how may data do you have). In addition I paste the basic comand that you need to made this task. Hoever, you can made your code much more complex. (I left this part to you..)

/************************************************** ********************/ /* UDF to read a scalar from an external file and stored in UDM Memory*/ /************************************************** ********************/

#include "udf.h" #include "sg.h" #include "dpm.h"

#define UDM_RH 0 #define N_REQ_UDM 1

DEFINE_ON_DEMAND(add_data) { extern Domain* domain; cell_t cell; Thread *thread; real x[ND_ND]; real a[4]; int i; char filename[]="myfilename.txt"; FILE *sfp; /*destination file pointer*/

Message("\n FILENAME:%s\n",filename);

sfp = fopen(filename, "r"); if(sfp == NULL) { Message("\n Warning: unable to open %s for reading\n", filename);

}

thread_loop_c(thread,domain)

{

begin_c_loop(cell,thread)

{

fscanf(sfp, "%g", &a[0]);

C_UDMI(cell,thread,UDM_RH) = a[0];

}

end_c_loop(cell,thread)

} fclose(sfp); }
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Old   June 6, 2003, 14:18
Default Re: UDF to read and write data
  #3
Alex Munoz
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Hi

Sorry I misunderstood your question you can use several functions such us define macro under comands or read and write under define UDF functions

Best regards

Alex Munoz
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Old   June 9, 2003, 07:52
Default Re: UDF to read and write data
  #4
Mcgregor
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Hi Alex,

How do i use read or write under define UDF functions?

What line do i include in my UDF?

Is it a simple as:

read-file ("path/filename")

Regards

Mc
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Old   June 9, 2003, 13:21
Default Re: UDF to read and write data
  #5
Alex Munoz
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Hi

I gave a code then compiled it, then under UDF load the library.

Then under execute on demand browse the name of the code (i.e., add_data) and excecuted.

However, what you want to do is totally diferent, Fluent allow you to import an external file that could contained a scalar field, boundary condition etc.

If I understood you problem you want to read a data file after a certain number of iteration. Therefoer, you must to search how to create a macro. I have never made this type of work so you have to find the information by yourself.

Regards

Alex Munoz
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