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July 3, 2009, 08:33 |
convergence of the solution
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#1 |
Member
amar
Join Date: Mar 2009
Posts: 31
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Dear all
I'd like to know what is the criteria to be sure that my solution is really converged. thanks a lot |
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July 3, 2009, 08:45 |
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#2 |
Super Moderator
Maxime Perelli
Join Date: Mar 2009
Location: Switzerland
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If you have a goal, then monitor it (force, pressure at inlet , massflow rate, etc..).
You achieve convergence if the monitoring doesn't fluctuate anymore with iterations
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In memory of my friend Hervé: CFD engineer & freerider |
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July 5, 2009, 09:08 |
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#3 |
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Convergence criteria are very problem dependent. My usual approach is to monitor a variety of variables (e.g. velocity at several points, forces on the body, mass flow rates) - the more the better really. As -mAx- says, once the values of these have stabilised then you have a converged solution. BUT only IF your residuals have fallen by a suitable amount from their initial values (don't rely on Fluent's default 10e-3 convergence criteria). What is a suitable amount? Again, very problem dependent, but for a steady-state external aerodynamics type problem I would expect the continuity residual to drop below 10e-6 and the velocity (momentum) residuals to drop much lower than that. The Fluent user guide has some helpful guidance on this too.
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