# cylindrical coordinate vs cartesian coordinate

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 November 29, 2003, 17:28 cylindrical coordinate vs cartesian coordinate #1 Lam Guest   Posts: n/a 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 thomas Guest   Posts: n/a 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 New Member   Hadi kafil Join Date: Apr 2013 Location: Istanbul Posts: 8 Rep Power: 11 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???

May 10, 2013, 05:56
#4
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Mukesh
Join Date: Sep 2012
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Quote:
 Originally Posted by grayeagle 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

 May 10, 2013, 10:24 cylinderical coordinate in Fluent #5 New Member   Hadi kafil Join Date: Apr 2013 Location: Istanbul Posts: 8 Rep Power: 11 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"

May 10, 2013, 14:01
#6
New Member

Mukesh
Join Date: Sep 2012
Posts: 28
Rep Power: 12
Quote:
 Originally Posted by grayeagle 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

 May 10, 2013, 19:49 #7 New Member   Hadi kafil Join Date: Apr 2013 Location: Istanbul Posts: 8 Rep Power: 11 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 " !

May 10, 2013, 22:22
#8
New Member

Mukesh
Join Date: Sep 2012
Posts: 28
Rep Power: 12
Quote:
 Originally Posted by grayeagle 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.

 May 11, 2013, 10:53 #9 Senior Member   OJ Join Date: Apr 2012 Location: United Kindom Posts: 473 Rep Power: 18 Can you post BCs please? OJ

 May 11, 2013, 13:39 #10 New Member   Hadi kafil Join Date: Apr 2013 Location: Istanbul Posts: 8 Rep Power: 11 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 New Member   Hadi kafil Join Date: Apr 2013 Location: Istanbul Posts: 8 Rep Power: 11 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 11:02.