Monitor a result and stop when it settles

Monitor the quantities used to make the engineering decision, then allow a stable quantity to stop the run when further iterations no longer change it materially.

Choose result quantities

Add a mean, minimum, maximum, or point probe for the temperature, pressure, or velocity that matters. Add mass or energy balance separately so conservation remains visible.

{
  "convergence_window": 100,
  "monitors": [
    {
      "mean": {
        "name": "mean_temperature",
        "field": "temperature",
        "exit_tolerance": 0.01
      }
    },
    {
      "maximum": {
        "name": "peak_temperature",
        "field": "temperature"
      }
    },
    {
      "mass_balance": {
        "relative": true
      }
    }
  ]
}

The example stops when mean temperature changes by less than 0.01 °C over the convergence window. It records peak temperature and relative mass balance without using either as a stopping condition.

Use a probe when a result is required at a known position:

{
  "probe": {
    "name": "outlet_temperature",
    "field": "temperature",
    "position": [0.1, 0.01, 0.01],
    "exit_tolerance": 0.02
  }
}

Probe positions are [x, y, z] in meters and must lie in the region where the chosen field is meaningful. Point probes explains cell selection at faces and why a probe is not spatially interpolated.

Stop on CTM junction temperature

Add exit_tolerance to a compact thermal model when its junction temperature should be allowed to stop the run:

"two_resistor_ctm": {
  "case_side": "y_max",
  "power": 5.0,
  "resistance_jb": 8.0,
  "resistance_jc": 0.35,
  "exit_tolerance": 0.01
}

Use the request’s shared comparison window:

"convergence_window": 100

Choose the tolerance from the engineering decision and inspect the complete junction-temperature history afterward. A short plateau can satisfy an overly loose tolerance before other quantities settle.

Set the stopping condition

Give an exit_tolerance only to a quantity that should be allowed to stop the run. Set convergence_window greater than 1 and no greater than max_iterations; progress updates are recorded automatically.

Choose a tolerance small enough for the engineering decision, not merely small enough to finish quickly. Increase the window when a quantity crosses the tolerance during short-lived plateaus.

Check the final value

An exit tolerance measures change, not acceptable magnitude. A stable mass imbalance can still be too large, and a stable temperature can still be physically wrong. Inspect the final monitor_* values in iteration_info.csv and use residual, conservation, mesh-sensitivity, and physical checks together.

See also

• Monitors and derived quantities explains reduction domains, probes, balances, and CTM junction temperatures.
• How simulations stop explains how monitor criteria interact with other terminal conditions.
• API reference lists the available monitor types and fields.