About Stopping Criteria

You can define stopping criteria for the solver equations in a steady-state flow step. Two types of metrics are available as criteria for stopping: relative estimated error-based metrics and normalized residual-based metrics. You can specify these metrics for individual solver equations in the steady-state flow step.

Calculating Relative Error and Normalized Residuals

The following examples illustrate how to calculate relative error and normalized residuals for a particular value:

If $e_{T}$ is the estimated error in the temperature field at a certain iteration, ${| {Δ e}_{T} |}_{V}$ is the volume weighted norm of the estimated error in the temperature solution at that iteration. In this case, the relative estimated error in energy is given by $\frac{{| {Δ e}_{T} |}_{V}}{{| T |}_{V}},$ where ${| T |}_{V}$ is the volume weighted norm of the temperature field at the current iteration.
The app calculates the normalized residual by normalizing the L-2 norm of the current iteration’s residual by the L-2 norm of the residual obtained at the first iteration.

Available Stopping Criteria for Each Solver Equation

The table below shows the available relative estimated error and normalized residuals stopping criteria for each solver equation in steady-state flow steps:


Solver Equation	Relative Estimated Error Stopping Criteria	Normalized Residuals Stopping Criteria
Momentum	Root mean square (RMS) of V_x, V_y, and V_z error	RMS of V_x, V_y, and V_z residual
Energy	Energy error	Temperature residual
Species	Maximum error for all species	Maximum residual for all species
Turbulence	Error value dependent on the selected turbulence model. This criterion could represent any of the following turbulence values: turbulence kinetic energy (TKE), k-epsilon (EPS), k-omega (OMEGA), or turbulence eddy viscosity (TURBNU).	Residual value dependent on the selected turbulence model. This criterion could represent any of the following turbulence values: turbulence kinetic energy (TKE), k-epsilon (EPS), k-omega (OMEGA), or turbulence eddy viscosity (TURBNU).
Electromagnetic potential (EPS)	Electric potential error	Electric potential residual

How Stopping Criteria Terminate the Simulation

Stopping criteria are additive: the app ends the analysis only when all of the active stopping criterion satisfy the specified thresholds for a specified number of consecutive sampled iterations. You can adjust the number of consecutive sampled iterations.