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 convection-diffusion equation when I'm simulating combustion. Interesting point is that the results looks ok and have good agreement with experimental results. In this page:

http://www.afs.enea.it/project/neptunius/docs/fluent/html/ug/node833.htm

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 10-3 for all equations except the energy and P-1 equations, for which the criterion is 10-6."

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:

    3. Why does it happans? (I mean why does the residual start from a non-zero magnitude?) and How to figure it out?

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

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