A problem in using a FENE-P Case

[Joe199999]

Dear Professor Pimenta,

I studied the FENE models section in the user guide and recall your note about their divergent simulation results. I’m attempting to replicate findings from the paper ( doi:10.1017/S0022112009994083 ) on FENE-P fluid flow around a cylinder at Re=100, Wi=10, η_s/η₀=0.9, and L²=10000.

While I achieved good agreement with the author’s L²=100 results, significant deviations persist for FENE-PLog at L²=10000 despite using a refined mesh, low time steps (Co=0.1), and other adjustments. The FENE-P model diverges even at Co=0.1.

I’ve attached my case setup and results for your reference.
I’d sincerely appreciate your insights on resolving this discrepancy.

Thank you for your time.

03.2-case.zip

[Joe199999]

I thought about this issue a lot, and I found that the only difference is in the numerical methods: Log-conformation in rheoTool and Artificial diffusion in the reference paper.
Has anyone found any limitations or defects in the Log-conformation approach?
Is it reasonable that we get different results between these two methods? Or get the correct results from Artificial diffusion and wrong results from Log-conformation method?