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SpectraSim Documentation
Parameter · 07 Run Settings

Turbulent kinetic energy tolerance

simulation_control.residual_targets.k Step 07 · Run Settings

The absolute tolerance of the initial residual of the transport equation of the turbulent kinetic energy, used by quality gate 2 when per-field tolerances are switched on. Auto follows the single residual target.

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Theory

With Per-field residual tolerances on, gate 2 judges the turbulent kinetic energy kk. The test is the one of Residual target: the largest initial residual over the last 50 iterations must be below this tolerance, or the residual must have fallen by the residual drop (Residual drop) from the start of the run, equation (1).

The turbulence equations usually fall further than velocity and pressure; a tighter tolerance here is possible without holding up the verdict.

The residual is OpenFOAM's normalised initial residual (OpenFOAM user guide, 2026): dimensionless, whatever the unit of the field. The tolerance never stops the solver itself (its own residualControl stays at 10−510^{-5}); it decides whether gate 2 reports the residuals as converged.

Equations

max⁡i∈last 50rϕ,i<rk  ∨  log⁡10max⁡i≤10rϕ,imax⁡i∈last 50rϕ,i≥D,ϕ∈{k}\max_{i \in \text{last 50}} r_{\phi,i} < r_{k} \ \ \lor\ \ \log_{10}\frac{\max_{i \le 10} r_{\phi,i}}{\max_{i \in \text{last 50}} r_{\phi,i}} \ge D, \qquad \phi \in \{k\}
(1)
wheremeaningunit
rϕ,ir_{\phi,i}Initial residual of field ϕ\phi at iteration ii-
rkr_{k}Tolerance of this equation (this setting)-
DDResidual drop, when setdecades

Default and rule

Default
auto (= the residual target: 1e-3 steady)Computed by the program
Rule

Auto: the single residual target (10−310^{-3} for a steady run). A typed value is used only while per-field tolerances are on.

Source

No separate default per equation has been measured; the auto value is the single target, whose basis is the program's residual-sensitivity study (see Residual target).

Valid range 0 < r < 1

Values

Between 0 and 1 (exclusive), or auto.

References 1

  1. OpenCFD Ltd. (2026). OpenFOAM user guide. openfoam.com. Web page