Add an internal fan with linked boundaries

Use linked fan boundaries when the intake and exhaust of a fan are both inside the simulation domain.

Place the boundaries

1. Put linked_fan_intake where fluid leaves the surrounding fluid region and enters the fan.
2. Put linked_fan_exhaust where fluid leaves the fan and returns to the surrounding fluid region.
3. Give the two boundaries the same unique fan tag.

For a fan represented by an insulating cuboid, add the following object to cuboid_components and adjust its bounding box and face directions:

{
  "tag": "fan_unit",
  "bbox": {
    "origin": [0.04, 0.01, 0.01],
    "size": [0.01, 0.04, 0.04]
  },
  "thermal_model": "insulating",
  "boundary_conditions": [
    {
      "boundary": { "full": { "side": "x_min" } },
      "condition": {
        "linked_fan_intake": { "tag": "internal_fan" }
      }
    },
    {
      "boundary": { "full": { "side": "x_max" } },
      "condition": {
        "linked_fan_exhaust": {
          "tag": "internal_fan",
          "flow_rates": [0.0, 0.01, 0.02],
          "static_pressures": [100.0, 50.0, 0.0]
        }
      }
    }
  ]
}

The fan tag internal_fan links the boundaries; it does not need to match the component tag fan_unit. Each fan tag must identify exactly one intake and one exhaust.

If the opening covers only part of a face, replace full with a circle, rectangle, or annulus boundary.

Set the fan curve

Follow Prepare the fan curve to convert and validate the manufacturer’s static-pressure data. Put the resulting flow_rates and static_pressures arrays on linked_fan_exhaust; the intake carries only the shared fan tag.

Stabilize the operating point

If the fan pressure oscillates, add a smaller relaxation_factor to linked_fan_exhaust:

"relaxation_factor": 0.05

Smaller values damp changes more strongly.

See also

• Drive airflow from a fan curve configures a fan mounted on the exterior domain.
• Fan and linked-fan boundaries explains the pressure, flow, and temperature coupling.
• API reference lists fields and limits.