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Fluent transient solver keeps iterating, although residual is reached on first iter

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Old   February 10, 2014, 03:24
Default Fluent transient solver keeps iterating, although residual is reached on first iter
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Hi everybody,

I have some difficulties understanding the convergence behavior of a transient fluent run. At each timestep, before iterations even start, I get the message that the solution is converged. Indeed, the residuals displayed after this message are smaller then the convergence criteria I set. However, the solver doesn't stop at this point but continues for another ten or so iterations. In the second iteration the residuals jump back up and are then decreased back to convergence bound (see attached file).

I don't really know what to make of this behavior. If the solution is converged on the first iteration, shouldn't the solver stop and move to the next timestep? In that case, I'd say that the timestep is too small. But why does the solver keep iterating?

I'd be happy to hear any thoughts any of you might have!
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