### 9.17.3. Tips for Improving Convergence

It is often useful to apply a larger timestep to temperature and species than the remaining equations. Try starting with a relatively large timestep to let the material sweep through the domain. You can reduce the timestep later to achieve better resolution of the simulation conditions and, therefore, convergence.

When using the Finite Rate Chemistry model, using a timestep that is too large at the beginning may cause the solver to fail due to reaction rates not converging. Under these circumstances, the timestep must be reduced.

Selecting the expert parameter `monitor ranges` enables you to monitor species mass fractions and temperature. This is useful to check that the reaction has started, in particular when using Finite Rate Chemistry of the combined EDM/Finite Rate Chemistry model.

Additional information on expert parameters is available. For details, see CFX-Solver Expert Control Parameters.

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