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Velocity profile with cylindrical components

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Old   June 7, 2015, 15:31
Default Velocity profile with cylindrical components
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Shobhan Roy
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I am writing a UDF for velocity profile at inlet of a draft tube. The inlet is in cylindrical (radial, azimuthal, axial) components. In this case, particularly azimuthal component. I need it to vary with inlet radius. The code is as follows:

#include "udf.h"

real a[ND_ND]; /* this will hold the position vector */
real r, R=0.123, E=2.71828;
face_t f;

r = a[1];
if (r<=R)
F_PROFILE(f,thread,position) = ((100*R)/(r/R))*(1-pow(E,-(r/R)*(r/R));

The error is shown as on line 15: parse error;
I suspect some changes are to be made since the face is 2d but then the equation is to vary with radius only.
Please help.
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Old   June 7, 2015, 16:31
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There is a mismatch between the number of opening and closing parentheses in F_PROFILE(f,thread,position) = ((100*R)/(r/R))*(1-pow(E,-(r/R)*(r/R));

Aditionally, it is always a good idea to write real values instead of integer values to avoid integer arithmetic if you dont want it. Change 100 to 100.0 and so on

And the last line in your loop does not seem to make any sense to me.
The value of r is fetched at the beginning of the loop from the face centroid position. This will overwrite any changes you made at the end of the loop anyway.

Be sure that a[1] is in fact the radial coordinate you need. I am not 100% sure about the convention in fluent, consult the UDF manual.
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cylindrical coordinates, udf, velocity profile

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