Why does the FLOW5 free version not generate drag and moment polars for inviscid analysis?

[AadarshGejage]

I previously used FLOW5 with a student/research license (pre-2026).

In that version, running inviscid analysis produced all polar plots (CL–α, CD–α, Cm–α, CL–CD).

From 1 Jan 2026, using the free/open FLOW5 version, I observe a change:

Inviscid analysis now generates only the lift polar (CL vs α).

Drag and moment polars (CD, Cm, CL–CD) are not shown.

This happens even when:

Opening and re-running my old .fl5 files.

However, FLOW5 example models still show all polars when run.

My question:

Is this behavior intentional in the free version?

Are CD and Cm intentionally disabled for pure inviscid analysis, requiring viscous analysis ?

[techwinder]

Nothing has changed. In the inviscid case, flow5 calculates the polar to the exception of the viscous quantities.
Make sure that you have selected the polar graph variable "Drag" and not "Viscous drag".

[AadarshGejage]

Dear, team I have selected a proper total drag(N) Polar in graphs vs alpha (AOA) graph I have confirming I have not selected any kind of Viscous or another drag but still it is showing me this problem, is that can b a bug? or or any other problem, for reference I have added the image of the same. I am eagerly waiting for response

[techwinder]

Please share the project file and I'll have a look.

[techwinder]

There is a numerical error when computing the induced drag. Use "polar/edit data points" and values will show up as NaN (Not a Number).

There are several potential reasons:

• flow5 is not designed to handle side beams; at the very least do no connect the elevator to the beams and leave a gap in-between.
• the left elevator is constructed upside down; this can be seen as the red trailing edge panels are on the bottom surface instead of the top surface; construct preferably the elevator as a single wing
• the wake panels shed by the main wing intersect both the fuselage and the elevator; please watch the videos on recommended practices for plane construction

[AadarshGejage]

Dear flow5 team,

1. Thank you for your explanation regarding the wake–surface interaction.
2. I checked the same model geometry in different FLOW5 versions.
   3.With v51 and v53 version, the complete polar data is generated for this configuration.
3. In the open-source V54 version release, the polars are not shown for the same model.
4. I am not sure why this difference occurs between versions.
5. I will follow the recommended geometry practices to avoid wake intersections.