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Convergence check on forces

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

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