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Old   May 4, 2000, 16:32
Default Cell Mass flux
Sandeep Abhyankar
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In a 2d problem with quad cells, I want to be able to calculate what is the mass flux of fluid flowing across a particular edge of the 2d cell. Is there a way to get this value by UDF's or by anything ?
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Old   May 5, 2000, 04:11
Default Re: Cell Mass flux
Alfonso Ferrandez
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Hi Sandeep,

the following UDF allows you to calculate the flux across any thread in a 2D domain. If you want to calculate it for a single edge of a 2D Cell, I would recommend creating it as an independent 1D INTERIOR boundary condition. Then you can apply the algorithm below. Perhaps a check for the nodal coordinates of the given cell would also allow for a modification of the function below (Jonas! Another one for the repository!

/************************************************** ****************/ /* This function calculates the flux across the given boundary. */

/* We make use of Fluent Macros for this. */

/* Note that the THREAD_ID parameter is the integer value shown as ID by the Boundary Conditions... Menu. */

/* Also, you must have defined domain as a global variable:


/* extern Domain *domain; */

/************************************************** ****************/

real flow_rate(int thread_id)


real flowrate = 0.0;

face_t face;

Thread *face_thread;

face_thread = Lookup_Thread(domain,thread_id);

begin_f_loop(face, face_thread)


flowrate = flowrate + F_FLUX(face, face_thread);


end_f_loop(face, face_thread)

return flowrate;


Hope it helps! AL
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Old   May 5, 2000, 08:51
Default Re: Cell Mass flux
Jonas Larsson
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I've added this UDF to the temporary UDF library at:

I named the file "flux_calculation.c"

As before anyone can contribute other UDF's by uploading them to:
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Old   May 5, 2000, 08:56
Default Re: Cell Mass flux
Sandeep Abhyankar
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Thanks a lot AL.
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