# Convergence check on forces

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March 13, 2011, 17:43
Convergence check on forces
#1
Senior Member

Andrea Pasquali
Join Date: Sep 2009
Location: Germany
Posts: 142
Rep Power: 7
Hi,
I'm trying to add the convergence check on forces function following the residuals convergence check in simpleFoam.
For example, for the forces pressure, I added those lines:
Quote:
 scalar eqnResidualFF = 1, maxResidualFF = 0; eqnResidualFF = solve ( fm.first().first() += sum(fN) ).initialResidual(); maxResidualFF = max(eqnResidualFF, maxResidualFF);
After compilation I got the error:
Quote:
 error: invalid use of void expression
What I'm wronging? I think it does not like the expression:
Quote:
 +=
Could anyone help me to go ahead?

Thanks

Andrea
__________________
Andrea Pasquali

March 16, 2011, 06:24
#2
Senior Member

Andrea Pasquali
Join Date: Sep 2009
Location: Germany
Posts: 142
Rep Power: 7
Hi,
I solved my problems and I did the new lib to check the error on the forces / moments.
At now I calculate the increment between it i and it i-1:

err = || (force)[i] - (forces)[i-1] ||

I attached the plots for increment, residuals and force.

I'd like to stop the calculation when the force becomes more or less constant (2000-3000 its) without waiting for residuals convergence check (because it is possible my Ux Uy Uz residuals don't decrease under the convergence declared in fvSolution).

I hoped to do that checking the increment but as you can see it is very dispersive.
Is it possible to do what I want to do?

Thanks in advance for any help and suggestion

Andrea
Attached Images
 increment.png (19.0 KB, 16 views) residulas.png (8.3 KB, 16 views) force.png (5.5 KB, 15 views)
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Andrea Pasquali

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