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[solids4Foam] problem in Aitken and IQILNS algorithm

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Old   January 10, 2020, 00:55
Default problem in Aitken and IQILNS algorithm
  #1
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Hojatollah Gholami
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Dear Foamer
In solids4Foam, in Aitken and IQILNS algorithm, after three iteration, we have
Quote:
forAll(fluid().globalPatches(), i)
{
aitkenRelaxationFactors_[i] =
-aitkenRelaxationFactors_[i]
*(
sum
(
residualsPrev()[i]
& (residuals()[i] - residualsPrev()[i])
)
/(
sum
(
(residuals()[i] - residualsPrev()[i])
& (residuals()[i] - residualsPrev()[i])
)
)
);
In multi Interfaces case, I have problem after three iteration. the solver give floating point that seen due to above part of code. As the solver try to divide to
Quote:
sum
(
(residuals()[i] - residualsPrev()[i])
& (residuals()[i] - residualsPrev()[i])
)
the floating point occurs. Why we sure this part is always nonZero?
may need to add "VSmall" to this part to avoid floating point?
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Old   January 12, 2020, 09:17
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  #2
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Hojatollah Gholami
Join Date: Jan 2019
Posts: 140
Rep Power: 4
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I add VSMALL in AitkenCouplingInterface as:
Quote:
forAll(fluid().globalPatches(), i)
{
aitkenRelaxationFactors_[i] =
-aitkenRelaxationFactors_[i]
*(
sum
(
residualsPrev()[i]
& (residuals()[i] - residualsPrev()[i])
)
/( VSMALL +
sum
(
(residuals()[i] - residualsPrev()[i])
& (residuals()[i] - residualsPrev()[i])
)
)
);
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