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Turbulent Separation problem

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Old   September 5, 2015, 07:19
Default Turbulent Separation problem
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Dear all

I am modeling laminar separation bubble over NACA0012 at Re=1.35E5. The airfoil experiences different A.O.A in a 2D problem (It is a static run). Yplus is round 1 and 4Eq. kwSST transition modeling ( Gamma and Theta) is used. I can capture separation bubble and reattachment and transition to turbulent flow. I have some questions which have confused me:

1- Why is it possible to capture separation bubble with steady solver, while as we know separation is a time dependent phenomenon?

2- What might be the reason that I can not capture trailing edge turbulent separation with both steady and unsteady solvers at AOA 6, 8 and 10 degree while experiments report turbulent separation point at x/c = 0.9, 0.8, 0.6!!!

I have also tried some fully turbulent flows using K-w SST with yplus=1, but no turbulent separation is observed in rather high A.O.A (X-wall shear flux does not vanish)!!

Experiment results are based on " An Experimental Investigation of Flow Over an Oscillating Airfoil" a MSC thesis 2004 at McGill University, Montreal, Quebec, Canada.

I have attached some contour and plots. Any comment or tutorial on how to capture separation point? Any idea?!

Attached Images
File Type: jpg BL MESH.jpg (167.9 KB, 11 views)
File Type: jpg MESH-AOA 8 deg.jpg (166.5 KB, 11 views)
File Type: jpg yplus.jpg (51.1 KB, 15 views)
File Type: jpg StreamLine3.jpg (55.5 KB, 17 views)
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Old   September 7, 2015, 13:59
Default Any idea about separation
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Any Idea of CFD experts about my separation problem recently posted?

Trivial ,but strange!!!!!!!!!!!!:
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