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leastSquares vs. Gauss linear

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Old   January 11, 2019, 10:10
Default leastSquares vs. Gauss linear
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Hi all,


Quick question: is there any general rule about when to pick leastSquares vs. Gauss linear for Grad(U)? From what I've read, it seems like leastSquares is more accurate when you have skewness in the mesh.


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Old   January 11, 2019, 10:42
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Quick answer: Always use LSQ unless you run into troubles.
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Old   January 11, 2019, 10:43
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Great, thanks so much!
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Old   January 11, 2019, 13:59
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Hi, sorry one more question, does that also apply to Grad(p)?
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Old   January 12, 2019, 08:24
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I've seen it recommend to use LSQ unless you're on a tet mesh because of osciillitatory behaviour. I've also seen it recommend to never apply limiters on p field and that p should use Gauss linear as it is not a convective term.
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Old   January 14, 2019, 07:51
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Why would it matter if the gradient you are evaluating is part of the convective term or not?
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Old   January 14, 2019, 08:20
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@akidess: So do you always use leastSquares for both grad(U) and grad(P)? I had one experience recently where a low-Reynolds number solution converged with grad(p) Gauss linear but diverged with grad(p) leastSquares. I guess this is probably due to a poorly designed mesh?


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Old   January 14, 2019, 08:54
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Quote:
Originally Posted by akidess View Post
Why would it matter if the gradient you are evaluating is part of the convective term or not?
Not actually sure see:
gradient schemes
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