Learning Forum

[designteam2]

I am trying to do a 2D axisymmetric simulation in ANSYS Fluent. In the geometry cell I deselected solid bodies and line bodies so that only the surface is imported and changed the analysis type to 2D. In the mesh cell I changed the geometry 2D behavior to axisymmetric. I also created a named section for the centerline which will be the axis. Finally, in the setup cell, under boundary condition tab, I made the centerline type axis. I also went to the general tab to change the setting from planar to axisymmetric. 

Despite all the changes I made, the simulation doesn't work when I run a calculation. I keep getting floating point errors. Note that the simulation works for a full 2D model when I don't make the axisymmetric changes. 

 

 

[peteroznewman]

• Start over with a fresh Fluent analysis block.
• Pick the Geometry tab and set the Analysis Type to 2D before you start.
• Create a surface on the XY plane and the axis must be the X-axis and the surface must be on the +Y side of the X-axis.
• In Meshing, add the named selections and set the 2D behavior to Axisymmetric under the Geometry Details window.
• In Workbench, Update the Mesh cell to get a green check, then Refresh the Setup cell then double click to start Fluent
• In Fluent, you will be able to set the model to Axisymmetric.

 

[designteam2]

I think this worked! Before I had a fluid going from the inlet to the outlet (origin centered at 0,0 and then fluid goes positive y-direction with gravity going down y-direction), now the fluid velocity would be dependent on the x-direction correct?

[peteroznewman]

If it's a vertical pipe in the real world, you still have to draw it on the X-axis for it to be Axisymmetric, that's just the way the software was written. You can turn on Gravity, it just has the acceleration component in the X direction so X is up and down, while Y is the radial dimension and the software is computing a full 360 degrees of volume of fluid by analyzing that radial slice.

If this post answers your question, please mark Is Solution to show that the discussion is Solved, or ask a follow-up question.

Note that if you want to do a Structural Axisymmetric model, the axis must be the Y-axis. That's just the way the software was written. But that was back when Fluent was a separate company from ANSYS.

[sinasalahshour74]

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Hello peteroznewman,

I want to compute the area in 2D axisymmetric that fluent use for computational , Does it obtain from pi*r^2?

Best Regards,

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[Rob]

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Do you mean the end of the pipe? This might help https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v221/en/flu_ug/flu_ug_sec_report_conventions.html

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