Preventing Premature Convergence in Ansys Fluent Adjoint Optimizer

Why does the Ansys Fluent adjoint gradient-based optimizer report all calculations to be converged, but checking the flow residuals of the optimal design shows that only one iteration is calculated for each design point?

It is possible that after a design change, the flow results don't change much. The residuals may need more than one iteration to rise above the convergence criteria. Therefore, Fluent software detects the solution to be converged immediately. This triggers the optimizer to continue with the next adjoint calculation prematurely. The only way to detect this behavior is to check the transcript very carefully or look at a .cas/.dat pair that is either saved as an optimal solution or by the autosave feature of the optimizer.

To avoid this behavior, increase the reporting interval on the 'run calculation' task page to a value larger than 1 — e.g., 5. This not only reduces the residual output to the console and transcripts for the flow calculation, but also limits the convergence check to the specified interval.