NPSS 3.0: Handling Newton Solver Tolerance Changes for Legacy Models

With the release of NPSS 3.0, the default Newton solver tolerance was reduced from 1e-4 to 1e-6 to improve accuracy in high-fidelity cycle simulations. While this change benefits newer models, it may cause convergence issues for legacy turbine and compressor models that previously relied on the looser tolerance. These models may now exceed the maximum iteration count or fail to converge, particularly when using map-based components with extrapolated speed lines.

The unresolved question is whether existing input decks should automatically inherit the new tolerance or require an explicit user-specified tolerance flag to maintain backward compatibility. The decision impacts how legacy models are handled in updated simulations.

• What is the recommended approach for adjusting Newton solver tolerance in NPSS 3.0 to ensure convergence for legacy models without sacrificing solution accuracy?
• Are there specific model components or configurations that are more susceptible to convergence failures with the new tolerance, and how can they be identified?
• Should users manually specify the tolerance in input decks, or is there a configuration option to revert to the pre-3.0 default globally?