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I've applied this same setup with k-epsilon Realizable model to the 3D flat plate case with 70º angle of attack I've been dealing with. It's working too! I think the key is the courant number modification.
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It is cournt number for pressure-based coupled solver which couples continuity and momentum equation only. So the definition is not same as the cournt number we study in CFD course.
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How does it afect to increase it from default 200 to 20,000?
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Fluent guide says, you can increase it to 200,000 and it worked for me for transition modelling of low pressure turbine. In fact this model was used first time for the the low pressure turbine case (i can give you that paper which made use of Fluent's pressure based coupled solver) due to fact that there is strong coupling of continuty and momentum equation. And when Simple type algorithms are used (which couples pressure - velocity fields loosely) they introduce errors for this class of problems and make the convergence difficult.
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What is the different between slip zero shear stress wall and symmetry BC?
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Both are same except that you need plane surface aligned with any plane for symmetry condition while slip condition can be applied to any surface. In fact I use slip condition due to my past practice. Some friends here always use symmetry condition. But in my point of view results should be same.
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I'm using default k and epsilon at the inlet but I'm gonna need to modifiy them. Would this make me change the mesh or reducing even more under-relax factors?
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Why you want to change them? Do you want to match some test conditions for which you have specific values of turbulence parameters. Any how , you dont need to change any thing.
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For how long should I maintain the reduced under-relax factors? It's making my simulations pretty slow..
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For pressure based coupled solver, we don't have option for URF!
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