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Old   January 13, 2005, 04:27
Default question about writing an udf
Denitiu Marian
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I'm trying to write an udf, to simulate a periodic flow through a geometry composed of a center cilinder, and three pipes which all comunicate with the central cilinder. They are placed at 120 degrees apart from each other. At a certain time, through one of the pipes, I have fluid coming inside the geometry, and through the other two, the fluid is coming out. I'm not really interested about the time variation, but I want the principle of the thing explained to me.

Here is what I wrote. It is based ont the oscilating pressure udf, found on the Fluent documentation disk. /

#include "udf.h"

DEFINE_PROFILE(unsteady_pressure, thread, position) {

float t, pressure; face_t f; float x,M;

begin_f_loop(f, thread) {

t = RP_Get_Real("flow-time");



if ((M>0) && (M<0.5)) {

pressure = (0.12*sin(1748.8*t)+0.737)*101325.0;


else M=0;

if ((M>0.5) && (M<1) {

pressure = (0.12*sin(1748.8*t)+0.737)*101325.0;


else M=0;

if ((M>1) && (M<1.5)) {

pressure = (0.12*sin(1748.8*t)+0.737)*101325.0;


else M=0; F_PROFILE(f, thread, position) = pressure; } end_f_loop(f, thread)


When I try to compile it, I receive: Error: c:\\pexit1.c: line 36: parse error. Error: c:\\pexit1.c: line 39: parse error. Error: c:\\pexit1.c: line 49: parse error.

Any ideas?
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Old   January 13, 2005, 06:19
Default Re: question about writing an udf
Andrew Garrard
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You will never get to the second two if ... else statements. When M is assigned a value in then enters the first if else. if it is between 0 and 0.5 it changes pressure. if not M becomes 0. This means that it won't enterd the remaining two if else statements.

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Old   January 14, 2005, 07:28
Default Re: question about writing an udf
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try to put your udf on your computer table,perhaps "parse error" will not appear again.
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