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Porblem getting resonable results using KomegaSST for an airfoil case

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Old   May 21, 2015, 13:40
Default Porblem getting resonable results using KomegaSST for an airfoil case
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Khamlaj
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Hello All,

I have been using OpenFoam for about four months so far. I’ve learned the basics through some tutorials and I’ve been recently trying to obtain some good results for a 2D airfoil case.

I’m using simpleFoam with both Spalart-Almaras and kOmegaSST turbulence models to simulate the flow around a NACA 0015 airfoil (Reynolds number approximately 2.575*10^6 and 0 degrees angle of attack). After finishing the grid convergence study, which gave a value of Cd = 0.016 at zero mesh spacing, I have obtained values of Cl and Cd 1.042858e-03 and 1.675878e-02 respectively. The experimental result, especially for Cd shows a value of 1.4e-02. However, after finishing the validation using Spalart-Almaras, I am unable to get reasonable results when I switch to KomegaSST turbulence model.


I’m really asking for some help.


MESH:
Using Gmsh

This is how the mesh looks like in Paraview:


Mesh.jpg
Zoom.jpg


BOUNDARY CONDITIONS:
I’m using freestream BC for U both at inlet and outlet, and obviously zero velocity condition on airfoil patch.
For p, freestreampressure at inlet/outlet and zerogradient on airfoil.
For k, freestream BC at inlet/outlet and fixedValue on airfoil.
For omega, freestream BC at inlet/outlet and fixedValue on airfoil.
For nut, calculated BC at inlet/outlet and fixedValue on airfoil.




Down here you’ll find the complete case directory with all the files


http://www.mediafire.com/download/zk...-Komega.tar.gz
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Old   May 22, 2015, 06:16
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Hasan K.J.
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Hello there,

What is your Y+ value and did you try your cases with and without wallfunctions ?, In my experience this factor is one of the most important for validation Please have a look here NACA0012 Validation Accuracy Improvement

What is the final validation you are trying to acheive ? just Cl/Cd or Cp and boundary layer growth aswell ?

If you want Cp and boundary data aswell did you consider them during mesh independency study

Regards,
Hasan K.J
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