Coupling
Where it is
Section titled “Where it is”Setup tree: Coupling
Controls
Section titled “Controls”EXCHANGE
Section titled “EXCHANGE”Physics
Section titled “Physics”- Control: choice (
ComboRow)
FLUID PROPERTIES
Section titled “FLUID PROPERTIES”The flow study is incompressible
Section titled “The flow study is incompressible”- Control: on/off (
ToggleRow)
An incompressible solver works in kinematic pressure and carries no density or heat capacity of its own, so they have to be stated here. A compressible one has a thermophysical model and the adapter reads them from it.
Fluid density
Section titled “Fluid density”- Control: value (
ValueField) - Unit: kg/m³
- Value modes: none (plain entry)
- Shown when:
CouplingState.incompressibleFlow
Water is about 1000, seawater 1025, air 1.2. The same number the one-way flow load asks for, and for the same reason: it is the factor between p/rho and a pressure.
Specific heat
Section titled “Specific heat”- Control: value (
ValueField) - Unit: J/(kg·K)
- Value modes: none (plain entry)
- Shown when:
CouplingState.incompressibleFlow && !root.fsi
Cp. Water is about 4180, air 1005.
Prandtl number
Section titled “Prandtl number”- Control: value (
ValueField) - Value modes: none (plain entry)
- Shown when:
CouplingState.incompressibleFlow && !root.fsi
How the adapter turns the turbulent diffusivity into a wall conductivity. Water is about 7 at room temperature, air 0.71.
PARTICIPANTS
Section titled “PARTICIPANTS”Flow study
Section titled “Flow study”- Control: choice (
ComboRow) - Options: ``
Its patch
Section titled “Its patch”- Control: choice (
ComboRow) - Shown when:
CouplingState.fluidSimulation !== ""
Solid study
Section titled “Solid study”- Control: choice (
ComboRow) - Options: ``
Its face group
Section titled “Its face group”- Control: value (
ValueField) - Value modes: none (plain entry)
- Shown when:
CouplingState.solidSimulation !== ""
The in-app guidance depends on the case:
- That study already names: …
- The named face on the solid mesh that touches the flow. The run lists every group the mesh has if this one is not on it.
MORE PARTICIPANTS
Section titled “MORE PARTICIPANTS”+ Add a participant
Section titled “+ Add a participant”- Control: action (
ToolButton2)
COUPLING SCHEME
Section titled “COUPLING SCHEME”Scheme
Section titled “Scheme”- Control: choice (
ComboRow)
Time window
Section titled “Time window”- Control: value (
ValueField) - Unit: s
- Value modes: none (plain entry)
The interval the two solvers agree on, not either one’s own time step. Each may sub-step inside it.
Windows
Section titled “Windows”- Control: value (
ValueField) - Value modes: none (plain entry)
How many windows to run. Zero means use the finish time instead.
Finish time
Section titled “Finish time”- Control: value (
ValueField) - Unit: s
- Value modes: none (plain entry)
An alternative end for the run. Zero means use the window count. One of the two has to be set, or the run has no end at all.
Max iterations
Section titled “Max iterations”- Control: value (
ValueField) - Value modes: none (plain entry)
- Shown when:
root.implicit
Per window. Reaching this without converging does not stop the run — preCICE moves on, and the window is simply not converged.
Convergence
Section titled “Convergence”- Control: value (
ValueField) - Value modes: none (plain entry)
- Shown when:
root.implicit
Relative change in the exchanged data below which the window is settled. 1e-3 is the usual starting point for FSI.
Acceleration
Section titled “Acceleration”- Control: choice (
ComboRow) - Shown when:
root.implicit
Initial relaxation
Section titled “Initial relaxation”- Control: value (
ValueField) - Value modes: none (plain entry)
- Shown when:
root.implicit && CouplingState.acceleration !== "None"
How much of the first iteration’s change to take. Between 0 and 1.
Windows reused
Section titled “Windows reused”- Control: value (
ValueField) - Value modes: none (plain entry)
- Shown when:
root.implicit && CouplingState.acceleration === "Quasi-Newton (IQN-ILS)"
How many past windows the quasi-Newton history keeps. More is usually faster and can become ill-conditioned.
INTERFACE MAPPING
Section titled “INTERFACE MAPPING”Mapping
Section titled “Mapping”- Control: choice (
ComboRow)
Support radius
Section titled “Support radius”- Control: value (
ValueField) - Unit: m
- Value modes: none (plain entry)
- Shown when:
CouplingState.mapping === "Radial basis functions"
A length, so there is no sensible default: about the size of the interface, or a few times the mesh spacing on it. Too small is nearest-neighbour at RBF prices; too large is slow and then ill-conditioned.
Dimensions
Section titled “Dimensions”- Control: value (
ValueField) - Value modes: none (plain entry)
2 or 3. Stated rather than derived, because the coupling is written before either mesh necessarily exists.
OUTPUT
Section titled “OUTPUT”Export the interface
Section titled “Export the interface”- Control: on/off (
ToggleRow)
Writes what preCICE actually carried across, per window, into precice-exports. When a coupling is wrong both solvers’ own results look plausible and this is the only place it shows.
Timing breakdown
Section titled “Timing breakdown”- Control: on/off (
ToggleRow)
preCICE’s own profile of where the time went — mapping, communication, or waiting for the other participant.
GENERATED CONFIGURATION
Section titled “GENERATED CONFIGURATION”Label changes with the case; the source gives these forms: Hide, Show.
- Control: action (
ToolButton2)
Conditional and repeated groups
Section titled “Conditional and repeated groups”Per item in CouplingState.extraLinks
Section titled “Per item in CouplingState.extraLinks”repeated once for every entry in CouplingState.extraLinks
Remove
Section titled “Remove”- Control: action (
ToolButton2)
Exchange
Section titled “Exchange”- Control: choice (
ComboRow)
Solid study
Section titled “Solid study”- Control: choice (
ComboRow) - Options: ``
Its face group
Section titled “Its face group”- Control: value (
ValueField) - Value modes: none (plain entry)
The named face on this solid’s mesh that touches the flow - its own interface, not the first link’s.
Fluid patch
Section titled “Fluid patch”- Control: choice (
ComboRow)
Problems reported against this step
Section titled “Problems reported against this step”The application checks these before a run and reports them in the Problems tab against this step.
| Severity | Message |
|---|---|
| error | … |
| error | … |
… marks a value the application computes at run time, so the source carries no fixed text for it.