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Bug fix: improve the logic of sorting singular values in SIGMA sgs model. #574

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Merged
TimoLin merged 1 commit into from
Jan 5, 2026
Merged

Bug fix: improve the logic of sorting singular values in SIGMA sgs model. #574

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23 changes: 8 additions & 15 deletions src/TurbulenceModels/turbulenceModels/Sigma/Sigma.C
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Original file line number Diff line number Diff line change
Expand Up @@ -57,21 +57,14 @@ void Sigma<BasicTurbulenceModel>::correctNut()
}

DiagonalMatrix<scalar> sigmas(SVD(gradUMatrix).S());
scalar sigma_1(max(sigmas));
scalar sigma_2(sigma_1);
scalar sigma_3(min(sigmas));

for (label ii = 0; ii<3; ii++)
{
if(sigmas[ii]>=sigma_3 && sigmas[ii]<=sigma_1) sigma_2 = sigmas[ii];

if(sigmas[ii]<0)
{
WarningInFunction
<< "Negative sigular values!!! sigmas = \n"
<< sigmas <<endl;
}
}

scalar s_a = sigmas[0];
scalar s_b = sigmas[1];
scalar s_c = sigmas[2];

scalar sigma_1 = max(max(s_a, s_b), s_c);
scalar sigma_3 = min(min(s_a, s_b), s_c);
scalar sigma_2 = s_a + s_b + s_c - sigma_1 - sigma_3;

if(abs(sigma_1)<ROOTVSMALL && !zeroSigma) zeroSigma = true;

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