For cases that use the density-based implicit solver, you can improve the solver robustness on meshes of poor quality by issuing the following poor mesh numerics text command:

solve/set/poor-mesh-numerics/enhanced-pmn? yes

This option allows you to obtain a solution otherwise not possible in some cases by applying local corrections and adding numerical stability measures on the poor-quality cells. Note, however, that if the mesh quality did not hinder the stability of the density-based solver, using this text command option will not affect the solution convergence.

By default, the orthogonality-quality threshold below which a cell is considered ill-shaped is set to 0.2, the CFL limit is set to 1, and a 1^st order scheme is selected. You can adjust the cell quality threshold by using the solve/set/poor-mesh-numerics/set-quality-threshold text command. The order of the poor-mesh-numerics scheme should not be changed.