Flow around cylinder gives poor results on unstructured meshes in Code_Saturne 9.1

We are testing the standard flow around cylinder case with Code_Saturne 9.1.

For structured meshes, the case works correctly in Code_Saturne 9.1.

However, with unstructured meshes, we could not obtain reasonable results. We tested both 2D/quasi-2D and 3D unstructured meshes, and also tested Reynolds numbers Re=200 and Re≈3900.

Observed behavior in Code_Saturne:

- No clear vortex shedding / Karman vortex street
- Poor wake field
- Abnormal velocity or pressure distribution near the outlet
- Outlet backflow messages such as `Incoming flow detained ... outlet faces`

For comparison, we ran the same meshes and the same Reynolds numbers in OpenFOAM, and the results were normal, with the expected wake/vortex behavior.

So the issue seems specific to Code_Saturne with unstructured meshes for the cylinder wake case.

Could you please advise whether this is a known limitation, a recommended setup issue, or a possible bug? Are there recommended settings for unstructured meshes in this case, especially for outlet boundary conditions, gradient reconstruction, or turbulence modeling?

まず、報告されている Re=200 および Re≈3900 における 2D/準2D と 3D の非構造格子を使って、標準的な円柱周り流れのケースを再現します。出口境界条件、勾配再構築、および乱流モデルの設定を、構造格子を使った計算および OpenFOAM の計算と比較します。挙動が設定の問題、既知の制限、または Code_Saturne のバグのいずれによるものかを特定し、裏付けのある推奨事項または再現可能な不具合を示せれば完了です。

索引モデルが issue の本文から書いたものです。