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Old   November 29, 2003, 17:28
Default cylindrical coordinate vs cartesian coordinate
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Lam
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I face a problem in comparing my CFD results (Fluent) with my LDA measures(Dantec) because they use cylindrical coordinate and cartesian coordinate respectively. Can I change the Fluent from a cylindrical coordinate to a cartesian coordinate?
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Old   December 1, 2003, 04:52
Default Re: cylindrical coordinate vs cartesian coordinate
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thomas
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Hi, I dunno if it is what you are looking for but here is the linked between the cartesian and cylindrical coord. in fluent Z -> X r -> Y theta -> Z

You can certainly find more informations on the fluent user web site (online documentation). Cheers, thomas
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Old   May 1, 2013, 18:33
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Hi, I'm solving a natural convection problem in Fluent 13, but I want to model a 3D symetric cylindrical shape in 2-d. I assume (r=x, z=y, theta=0).

How can I change my coordinate from Cartesian to cylindrical???
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Old   May 10, 2013, 04:56
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Quote:
Originally Posted by grayeagle View Post
Hi, I'm solving a natural convection problem in Fluent 13, but I want to model a 3D symetric cylindrical shape in 2-d. I assume (r=x, z=y, theta=0).

How can I change my coordinate from Cartesian to cylindrical???
Go to define/solver...
change your problem from 2D to aisymmetric. That's it.

Best Wishes,
Mukesh
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Old   May 10, 2013, 09:24
Default cylinderical coordinate in Fluent
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I have done it. Draw my half shape, and define the symmetry axis as "axis" in Boundary condition, and select 'Axisymmetry' in define-solver, but there is an error : "Divergence detected in AMG solver: x-momentum"
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Old   May 10, 2013, 13:01
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Quote:
Originally Posted by grayeagle View Post
I have done it. Draw my half shape, and define the symmetry axis as "axis" in Boundary condition, and select 'Axisymmetry' in define-solver, but there is an error : "Divergence detected in AMG solver: x-momentum"
for STEADY PROBLEM: you can try reducing relaxation factor of momentum equation from 0.7 to some lower value i.e, 0.4, 0.5, 0.6 [solve/controls...]

for UNSTAEDY PROBLEM: reduce the size of time step
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Old   May 10, 2013, 18:49
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I have reduced relaxation factor of momentum equation from 0.7 to 0.3, 0.4, 0.5, 0.6, ... but there is still that error.
I even close the momentum equation (Solution control-equation) but this time the error was " Divergence detected in AMG solver: temperature " !
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Old   May 10, 2013, 21:22
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Quote:
Originally Posted by grayeagle View Post
I have reduced relaxation factor of momentum equation from 0.7 to 0.3, 0.4, 0.5, 0.6, ... but there is still that error.
I even close the momentum equation (Solution control-equation) but this time the error was " Divergence detected in AMG solver: temperature " !
Try reducing RF for energy term from 1 to 0.7,0.8.
Else there is some problem with BC.
BTW what is problem you are trying to solve.
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Old   May 11, 2013, 09:53
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Can you post BCs please?

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Old   May 11, 2013, 12:39
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I have a rectangle ( a cross section of cylinder) I wanna solve Natural convection (and then solidification) problem.
I have a temperature gradient in right and left wall (my rectangle is 40x100). and this UDF is my boundary condition in left and right wall...
I solve it in cartesian coordinate, but in Cylindrical, I have problem.
#include "udf.h"

DEFINE_PROFILE(temperature_profile, thread, index)
{
real x[ND_ND]; /* this will hold the position vector */
real y;
face_t f;

begin_f_loop(f,thread)
{
F_CENTROID(x,f,thread);
y = x[1];
F_PROFILE(f, thread, index) =((1000*y)/2)+1223;
}
end_f_loop(f,thread)
}
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Old   May 11, 2013, 13:05
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I solved this problem in Planer (2d space) without any problem.
I reduce the Under-relaxation factor for energy and momentum.
I aslo try to solve it Transient.
But there is still this error.
for momentum equation: " Divergence detected in AMG solver: x-momentum "
for ener

Last edited by grayeagle; May 14, 2013 at 10:02.
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