Hi I am doing a practice of cl&cd prediction using NACA 0012 with Fluent. I have always obtained overprediction on both cl and cd continuously, and run out of ideas on where the problems are. cl exceeds by 20% and cd is over by 70% (at AOA 4, 5 degs)!!

I have run my cases in the following conditions:

steady-state

M=0.6 (tried 0.2 also)

Re = 2M

Fully turbulent flow (with S-A model, various viscosity ratio from 0.001 ~ 10 but no help)

unstructured mesh, but structured BL mesh

y+ on order of unity

2D mesh size 30k ~ 60k points

computation domain 100c uniformly in all directions

A continuity convergence criterion of 1e-9 cannot be reached, as the residual always hangs around on order of -6

Any comment/suggestion on improving the solution is appreciated!

At M_infty=0.6 and AOA=4.5 deg, the flow is highly sensitive to turbulence models. Did you try SST-k-omega?

yes. both S-A and SST models were attempted. Results did not differ much though...