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div(phi,U) GammaV ?

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Old   March 16, 2011, 08:49
Default div(phi,U) GammaV ?
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Hello,

i read some parts about the Gamma Scheme in Jasak's Thesis (pages 107-110) and wanted to try it now for my openFOAM simulations. My question is now, what the Greek_Gamma value should be if i define for example:
div (phi,U) GammaV [Greek_Gamma]

In the Documentation there is a recommendation for Greek_Gamma = 1 ( i think for maximal stability).
But where is the Greek_beta_m value of the chapter in the thesis? Or is this Greek_Gamma this Greek_beta_m? Or is it not possible to define this Greek_beta_m?

What are the best values for this factor in your simulations to get max accuracy (in the best case 2nd order) and still a good convergence rate???

Thanks a lot,

Rupert
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Old   March 16, 2011, 09:19
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What you call Greek_Gamma is beta_m / 2.0. There is no general rule what value to pick, you'll have to play around and find what works best for you. You should not specify a value smaller 0.2 though.
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Old   March 16, 2011, 10:31
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Thanks for your reply.

Jasak is writing in his thesis that beta should be between 0.1 and 0.5.
So do you mean that the Greek_Psi (sorry for the Gamma mistake) is two times beta? this would fit then with the bounds to Jasaks description ( beta [0.1;0.5] would lead to Psi [0.2;1]).

Or is it really 1/2* beta???

Thanks
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Old   March 16, 2011, 11:23
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Oh yes, sorry about that! I did mean to say that the value you specify in the fvSchemes file will be divided by 2, which gives you the proper beta_m for the limiter (see also Gamma.H in the C++ documentation).
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Old   March 17, 2011, 02:47
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thank you very much
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Old   August 16, 2013, 15:13
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Quote:
Originally Posted by akidess View Post
What you call Greek_Gamma is beta_m / 2.0. There is no general rule what value to pick, you'll have to play around and find what works best for you. You should not specify a value smaller 0.2 though.
Dear anton
we set the the grad, div, and laplacian schemes in this way:
"gradSchemes : default cellMDLimited Gauss linear 0.5; "

"divSchemes : div(phi,U) bounded Gauss GammaV 1.0;"

"laplacianSchemes : default Gauss linear limited 0.5; "

my Question is : when we want play around to found that what value is a good limiter for GammaV , e.g we decrease the limiter of GammaV tp 0.5, we also should decrease the limiters for grad, and laplacian scheme?
or they have no relate to each other?

Thank you
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