regionCoupledHeatFlux

Overview

regionCoupledHeatFlux is the flux side (Neumann side) of the temperature coupling used with heatTransferInterface for conjugate heat transfer and thermo-FSI. It derives from genericRegionCoupledFlux<scalar> (and so from fixedGradient). It fixes the normal temperature gradient so that the local conductive heat flux is equal and opposite to the heat flux of the value-side partner on the neighbour region, without an interfacial source. The partner must be a genericRegionCoupledJump<scalar>-derived BC, in practice regionCoupledTemperatureJump. Unlike its partner, this BC does not check the interface type (see Implementation).

Mathematical Formulation

Let $B$ be this patch and $A$ the neighbour (jump-side) patch:

imposed as the gradient

followed by relaxation with the acceleration model. fluxJump() returns zero.

Implementation

Run-time work is inherited from genericRegionCoupledFlux<scalar> (see there). The class adds:

• fluxJump(): returns a zero field.
• diffusivityName(): the diffusivity keyword if set, otherwise kappa. diffCoeff() uses a volScalarField with that name on the local region if one is registered, otherwise a uniform dimensionedScalar from the region’s transportProperties.
• heatTransInterface(): a type check plus cast to heatTransferInterface, as in regionCoupledTemperatureJump. It is declared and defined but never called, so the BC accepts any interface type listed first in interfaceType.

Per DNA iteration of T, updateCoeffs() updates the interface, refCasts the neighbour T patch field to genericRegionCoupledJumpFvPatchField<scalar>, interpolates and negates its flux(), divides by the local $\kappa$, relaxes the gradient and fixes it. evaluate() sets the patch temperature from the gradient (with the optional non-orthogonal and second-order corrections). The flux residual $|\kappa_B g_B + \mathcal{I}(q_A)|$ is checked against maxFluxRes.

Dictionary Entries

Usage

From tutorials/fluidStructureInteraction/heatedBeamInCrossFlow/0/solid/orig/partitioned/T:

interface
{
    type                    regionCoupledHeatFlux;
    interfaceType           (heatTransferInterface);
    diffusivity             "kappa";
    secondOrder             false;
    nonOrthCorr             false;
    value                   $internalField;
}

Partner in 0/fluid/orig/partitioned/T:

interfaceShadow
{
    type                    regionCoupledTemperatureJump;
    interfaceType           (heatTransferInterface);
    diffusivity             "kappa";
    accType                 aitken;
    relax                   0.75;
    secondOrder             false;
    nonOrthCorr             false;
    value                   $internalField;
}

Interface in constant/regionInterfaceProperties (heat transfer stacked on FSI):

fluidsolid
{
    interfaceType (fsiInterface heatTransferInterface);
    coupledPatchPair
    (
        (fluid interfaceShadow)
        (solid interface)
    );
    coupledFields
    (
        D
        T
    );
    coupled             yes;
    fsiInterfaceCoeffs
    {}
    heatTransferInterfaceCoeffs
    {
        jumpCoefficient               jumpCoefficient [ 0 0 0 0 0 0 0 ] 1;
    }
}

Known Limitations

• No interface-type check. heatTransInterface() is never called, so a wrong first interfaceType entry is not caught here. It is usually caught by the partner regionCoupledTemperatureJump, which does check.
• Partner must be a jump BC of T (bad-cast error otherwise).
• No interfacial heat source or contact resistance: fluxJump() is zero. For phase change use regionCoupledPhaseChangeHeatFlux.
• No unit check on kappa across the two regions.
• value is ignored on input and gradient is not written (restart starts from a zero gradient).
• First relaxation uses the patch values as reference (inherited; the tutorials use the default fixed/relax 1 on this side, where it has no effect).
• Inherited from genericRegionCoupledFlux: neighbourFieldName unused, corrections only in the evaluated value, IQNILS not parallel-consistent, partitioned only.

Tutorials

References

• Alkfri, A., Habes, C., Marschall, H., multiRegionFoam: A Unified Multiphysics Framework for Multi-Region Coupled Continuum-Physical Problems, Engineering with Computers, 2023. DOI: 10.1007/s00366-024-01974-4