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March 18, 2015, 12:57 
About equation relaxation

#1 
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I'm currently looking into equation relaxation as I'm having some equations which converge very badly.
Some observations:


May 2, 2017, 20:52 

#2  
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Yuehan
Join Date: Nov 2012
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Quote:
As far as I understand the book, the field relaxation is the 'explicit relaxation', whereas the equation relaxation is 'impliciat' relaxation. The book says that for SIMPLE algorithm in steady state simulation, pressure field is underrelaxed by explicit relaxation (field relaxation), and implicit underrelaxation helps increase the diagonal dominance and therefore promote stability. But I am also confused that fvMatrix.C seems to do some manipulation on the diagonal matrix D to ensure diagonal dominance. Code:
// Ensure the matrix is diagonally dominant... // Assumes that the central coefficient is positive and ensures it is forAll(D, celli) { D[celli] = max(mag(D[celli]), sumOff[celli]); } If these lines do not change D, then Eqn.relax(1) will not do relaxation, since D is equal to D0. 

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