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cylindrical coordinate vs cartesian coordinate 

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November 29, 2003, 17:28 
cylindrical coordinate vs cartesian coordinate

#1 
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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?


December 1, 2003, 04:52 
Re: cylindrical coordinate vs cartesian coordinate

#2 
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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 

May 1, 2013, 19:33 

#3 
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Hadi kafil
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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 2d. I assume (r=x, z=y, theta=0).
How can I change my coordinate from Cartesian to cylindrical??? 

May 10, 2013, 05:56 

#4  
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Mukesh
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Quote:
change your problem from 2D to aisymmetric. That's it. Best Wishes, Mukesh 

May 10, 2013, 10:24 
cylinderical coordinate in Fluent

#5 
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Hadi kafil
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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 definesolver, but there is an error : "Divergence detected in AMG solver: xmomentum"


May 10, 2013, 14:01 

#6  
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Mukesh
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Quote:
for UNSTAEDY PROBLEM: reduce the size of time step 

May 10, 2013, 19:49 

#7 
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Hadi kafil
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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 controlequation) but this time the error was " Divergence detected in AMG solver: temperature " ! 

May 10, 2013, 22:22 

#8  
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Mukesh
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Quote:
Else there is some problem with BC. BTW what is problem you are trying to solve. 

May 11, 2013, 10:53 

#9 
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OJ
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Can you post BCs please?
OJ 

May 11, 2013, 13:39 

#10 
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Hadi kafil
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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) } 

May 11, 2013, 14:05 

#11 
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Hadi kafil
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I solved this problem in Planer (2d space) without any problem.
I reduce the Underrelaxation 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: xmomentum " for ener Last edited by grayeagle; May 14, 2013 at 11:02. 

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