[Roh]

Guys,
Sometimes after initializing the problem in Fluent and triggering the calculate button, a residual/residuals start from a big non-zero magnitude. For instance, to me, it in many cases happens for some covection-deffusion equation when I'm simulating combustion. Interesting point is that the results looks ok and have good agreement with experimental results. In this page:


Judging Convergence



It's said that:

For most problems, the default convergence criterion in ANSYS FLUENT is sufficient. This criterion requires that the scaled residuals defined by Equation 26.13-4 or 26.13-9 decrease to for all equations except the energy and P-1 equations, for which the criterion is .

As it is said, the residuals need DECREASE TO 10^-3. Then it means that it doesn't matter from where the residual starts, it should finally decrease to 10^-3. Am I right? What's your opinion?


Another question:
Why does it happans? (I mean why does the residual start from a non-zero magnitude?)


I've attached a screenshot of the residual of a project for instance.

[Roh]

Another interesting case is attached. What's wrong with this solution?