[hiaselhans]

Hi Foamers!


I need to make a good c-mesh simpleFoam case for airfoil drag validation.


After quite some time of parameter optimization, i think i need some help to get a decent solution. Most of the time i have around 100% overprediction on Cd.


My mesh consists of several boundary layers with grading (~1.05) and farfield layers with a different grading (~1.1). the mesh is also graded so that on the transition from airfoil trailing edge to the wake mesh there is no jump in cell-width.


I tried several approaches for the mesh (pictures attached)

1. straight wake, boundary layer straight to the end
2. straight wake but the boundary layer fades out towards a linear distribution at the end
3. same as (1) but aligned with the flow (angle of attack)
4. same as (2) but aligned with the flow

option 1 had the least overprediction after a lot of parameter-finding but that was not very reproducible. Varying the stream angle changed the result A LOT.

• start_thickness: 0.0018
• num_boundary': 10
• num_farfield': 55
• numpoints': 300
• growth_rate': 1.14
• growth_rate_boundary': 1.05
• wake_length': 30
• wake_num': 150
• domain_height': 25.0
• yplus_min: 11.0289
• yplus_max: 62.8056
• yplus_avg: 26.8322

From digging this forum i found some answers using an y+ ~ 1.
Is it really necessary to have such a dense mesh with the k-omega-sst (or spallart-almarras) turbulence model?


I'd really appreciate your opinions on the mesh types and parameters


Thanks!
Simon

[random_ran]

The meshes you show in Figs. 1~4 have very large aspect ratio.

You may try to increase the number of the mesh cells and keep the mesh more "square".