[Peter023]

Hello all FLUENT fellows,

recently I encountered a problem with periodic boundaries in fluent (Ansys 13, Workbench+FLUENT) for my rotationally symmetric model, especially how to create them. After some research on this web I found only small pieces of know-how. I figured out the rest myself by experimenting. Here I share the knowledge I've got. I will show how to effectively create a rotational periodic boundary in a short tutorial. Here it comes:

1) Assuming a rotationally symmetric geometry, create a part of your desired model in the Design Modeler. The sketch can be revolved, for example, 30 degrees about any chosen axis, leaving a model of only 1/12th of the full-model volume. This model consists of 2 periodic boundaries. Nothing else needs to be done in DM.

2) a) Go to the Meshing utility. Find the "Model" folder at the top of the tree structure and hit the "Symmetry" button to create a Symmetry folder lower in the tree structure.

b) Expand the "Coordinate systems" and choose your coordinate system. In its properties, change the type to "Cylindrical". Chose the proper value for "Principal axis" and "Orientation about Principal Axis" to get the right direction of rotation indicated by a bent axis arrow.

3) Right click on the "Symmetry" folder created in step 2a and add "Cyclic Region". Go to the settings and complete the required parameters. Choose your cylindrical coordinate system. This row should not light yellow.

Right click on "mesh" and insert "Match Control". Choose the same boundaries as in the "Cyclic Region" keeping the proper order of High and Low... Transformation: cyclic, Coordinate syst.: Global.

Other functions (size fcn, etc.) can be used as well for your mesh.

Generate your mesh by "Update". No error should appear.

4) FLUENT: a) Load your mesh, run "Check". Go to "Cell Zone Conditions -> Edit". Set the proper "Rotation-Axis Direction", If the axis of rotation along the model is X, then set 1 in X direction, leaving 0 in Y and Z.

b) use TUI: mesh/modify-zones/make-periodic choose your periodic boundary IDs as the input. Everything should go well and complete cells match on both sides should be found.

c) run "Mesh -> Check" again. Run "Mesh -> Reorder -> Domain" to reduce the memory bandwidth.

Enjoy your periodic boundaries. :-)

Cheers,
Peter