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Underprediction of Lift Coefficient-NACA0012

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Old   September 13, 2019, 00:35
Default Underprediction of Lift Coefficient-NACA0012
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Hello,

1. I have been trying to estimate CL and CD of NACA0012 airfoil. I am constantly getting an underprediction of CL by around 19%. The Reynolds number I am working on is 4.0E5. Details of the setup are as follows:-
(a) 3D Steady in water
(b) Polyhderal and Prismlayer mesher
(c) SST-menter K-w turbulence model. Wall Y+ after simulation is attached.

2. I am unable to understand what I am missing. Is it the mesh? The number of cells is around 1.4 million.

3. Convergence happens without any issues. Further, in SST Menter-K-w model, do we need to activate the low Re damping factor for this case? The starccm manual says only for transitional flows that action needs to be undertakenPrism Layer.jpg

Prism Layer.jpg

Wing_AOA4_Mesh Scene 1.jpg

Wing_AOA4_Mesh Scene 2.jpg

Wing_AOA4_XY Plot 1.jpg
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Old   September 13, 2019, 09:26
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your mesh is definitely not appropriate. look into wake refinement and conduct a mesh dependency study before determining that your converged result is the best you can do.
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Old   September 14, 2019, 05:07
Default Wake Refinement
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Hello Matt,

1. Thank you very much for your suggestion.
2. Since the polyhedral meshing model doesn't have a wake refinement option, I incorporated a volumetric control. However, the drag result looks nice but CL is still being underpredicted.
3. I have set the extents of volumetric control based on the scalar view of velocity. Is there anything else I should incorporate in such cases?
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Old   September 16, 2019, 09:03
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The polyhedral mesher absolutely does have wake refinement options. A volumetric control is probably not the best way to approach that. Refer to the Star-CCM help files:

Pre-Processing > Meshing > Custom Mesh Controls > Mesh Refinement in a Wake

After that, make sure to do a mesh dependency study. Once you are confident that your result is independent of the spatial discritezation (i.e. your mesh), then you can assess whether your values are 'correct'.
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Old   September 16, 2019, 14:52
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You also can a Table-based Mesh Refinement.
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