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Old   March 14, 2005, 15:50
Default UDF interpretation trough TUI
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Hi everybody, I am working on a pulsatile flow simulation. I use a UDF to define a parabolic velocity profile at inlet of my model with a time-dependent centerline velocity.

My problem is that I cannot "interpret" the UDF through text commands but it seems that I cannot link the interpreted UDF to the appropriate boundary condition (in my case the UDF is used for the x-velocity component). Fluent prompts for file name and file data. I tried entering my UDF source code file without success.

I would be grateful for any advice anyone might have on this.

Best Regards David
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Old   March 15, 2005, 02:55
Default Re: UDF interpretation trough TUI
Melaku Habte
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You would get much more help if you put the error that fluent gave you up here, also your UDF...if there are some bugs ppl can see it.


Melaku Habte
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Old   March 18, 2005, 14:26
Default Re: UDF interpretation trough TUI
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Hi Melaku,

I am still struggling with this so I would appreciate your help. As mentionned previously, I need a certain UDF for inlet velocity. When using text commands, I am having problem "hooking" the UDF at velocity inlet once it has been interpreted succesfully. Also I cannot use an boundary profile file because the inlet condition has a time and space dependency. (See UDF)

Below I have copied part of the transcript file. Look closely to the definition of the velocity inlet condition. More precisely:

profile name [""] "square_wave" data name [""] "square_wave"

where square_wave is the name of my UDF. Am I doing somethig wrong? (See below Transcript File)

Also, bear in mind that I do not get an error message as you might have tought from my previous message. Nevertheless when I verify, with GUI, the x-velocity component for the velocity inlet has not been updated has I would like.

/*Partial Transcript File*/

> /define/user-defined/interpreted-functions UDF Source File Name [""] "c:libudfsquare_wave0.c" CPP Command Name ["cpp"] "cpp" virtual machine stack size [10000] 10000 display assembly code listing? [no] no

cpp -IC:\FLUENT.INC\fluent6.1.22/src -IC:\FLUENT.INC\fluent6.1.22/cortex/src -IC:\FLUENT.INC\fluent6.1.22/client/src -IC:\FLUENT.INC\fluent6.1.22/multiport/src -I. -DUDFCONFIG_H="<udfconfig.h>" c:\libudf\square_wave0.c

> /define/boundary-conditions/velocity-inlet (velocity_inlet.11) zone id/name [velocity_inlet.11] 3 Velocity Specification Method: Magnitude and Direction [no] no Velocity Specification Method: Components [no] yes Reference Frame: Absolute [yes] yes Use Profile for X-Velocity? [no] yes profile name [""] "square_wave" data name [""] "square_wave" Use Profile for Y-Velocity? [no] "no 0

The UDF that I would like to use is as follows. But again I do not think the problem lies there has Fluent interprets it succcesfully:

#include "udf.h" DEFINE_PROFILE (square_wave,thread,position) {

#define PI 3.14159

real x[ND_ND];

face_t f;

real z,y,test;


if (z<0.30)

test =0;

else if (z<0.70)


else if (z<1.3)


else if (z<1.7)


else if (z<2.3)


else if (z<2.7)


else if (z<3.3)


else if (z<3.7)


else if (z<4.3)




begin_f_loop(f, thread)




y = x[1];

F_PROFILE(f,thread,position) = test - y*y/(.0065*.0065)*test;


end_f_loop(f, thread)


Any comments or observations would be of great help.

Regards, David

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