I studied a paper about simulation of turbines using Fluent that included the following sentence, which I don't understand:

All converged solutions had a mass imbalance of less than 0.3%

What does the mass imbalance of converged solutions refer to?

How can I ensure this condition is met in Fluent?


Mass imbalance is a measure of the error in the solution. You would typically set the limit for this in the "Solution Controls" section of the inputs (if using the GUI). For mass imbalance, set the tolerance for residuals on the continuity equation. The solver will keep iterating until it finds a solution that satisfies all your residual tolerances, or until it reaches the limit of iterations that you set.

  • $\begingroup$ Thanks. I didn't understood your following sentences: "For mass imbalance, set the tolerance for residuals on the continuity equation." According your above statement, How i must set this in Fluent? Please give me trajectory in Fluent. $\endgroup$ – user19061 Nov 1 '15 at 18:04
  • $\begingroup$ In the GUI, click on "Solution Controls", then look for the continuity equation box. The default tolerance is usually 0.001 I think. $\endgroup$ – Carlton Nov 1 '15 at 18:12
  • $\begingroup$ Thanks. In Fluent, there is Solution Controls option but i don't see this tolerance part in that!!! $\endgroup$ – user19061 Nov 1 '15 at 21:09
  • $\begingroup$ Depending on whether you're doing a pressure-based solution or a density-based one, the option may be for density residual tolerance. Do you at least see tolerance settings for various residuals? I.e. energy, momentum, etc.? $\endgroup$ – Carlton Nov 1 '15 at 21:18
  • $\begingroup$ I see as follows: upsara.com/images/eljd_capture33.jpg there is not any tolerance settings. $\endgroup$ – user19061 Nov 1 '15 at 21:29

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