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-   -   [ICEM] what's the different between SYMMETRY and AXIS (http://www.cfd-online.com/Forums/ansys-meshing/99957-whats-different-between-symmetry-axis.html)

 realstoneman April 17, 2012 00:06

what's the different between SYMMETRY and AXIS

what's the different between SYMMETRY and AXIS
I calculated a simulation model by Fluent,but when I used symmetry(boundary condition) it turn out ERROR:divergence AMG solver! I decreased the presure relaxation factor ,but failed again.So I converted the boundary condition into AXIS,the problem solved,I confused.
thanks a lot~

 Far April 17, 2012 04:29

Symmetry : It is used to reduce the computational model in 3D. For example if you have rectangular box then you can model 1/2 or 1/4 by using the one or two symmetry planes respectively.

Axis: It is used to model the 3D problem by just taking the one plane and then solving it in the cylindrical coordinates. So for x and y, you solve the problem in r coordinates (r 2 = x2 + y2) and for Z you use the axial coordinates. This is only valid for domain with circular periphery.

 realstoneman April 17, 2012 06:00

My simulation model is a ejector(2D),which contains a main inlet,an second inlet and an outlet,I set up the boundary condition as Symmetry at first,it turned out wrong,and Axis is right.as you said above,it's OK for both,why shouldn't I choose Symmetry?

 realstoneman April 17, 2012 06:11

1 Attachment(s)
here is the model

 realstoneman April 17, 2012 06:21

http://www.cfd-online.com/Forums/C:\...op\ejector.jpg

 Far April 17, 2012 06:36

Symmetry is used for the 3D model to reduce the mesh size and model still remains 3D.

Axis condition tells the solver that now activate the axisymmetric model and it is 2d model and uses 2d solver. Axis is always defined at axis of geometry.

 Far April 17, 2012 06:38

Quote:
 Originally Posted by realstoneman (Post 355104) here is the model
This is 2d planner section of 3d and therefore is candidate of axis condition.

 realstoneman April 17, 2012 06:41

It's kind of you.
thanks very much~

 soufy1990 February 14, 2013 13:10

Quote:
 Originally Posted by realstoneman (Post 355027) what's the different between SYMMETRY and AXIS I calculated a simulation model by Fluent,but when I used symmetry(boundary condition) it turn out ERROR:divergence AMG solver! I decreased the presure relaxation factor ,but failed again.So I converted the boundary condition into AXIS,the problem solved,I confused. thanks a lot~
yes ,I have the same probleme with fluent when I set the solver

it must to turn the symmetry condition to axis

but I dont solved it because ,I have a divergence solution

can you hep me what's the solver must used, and can you send me your file ejector.cas