chtMultiRegionFoam looses heat due to explicit coupling

Functionality to add/problem to solve

chtMultiRegionFoam looses heat when evaluating 'mapped' type bcs (e.g. compressible::turbulentTemperatureRadCoupledMixed). This is because the owner side evaluates with 'old' neighbour side values but the neighbour side evaluates with the 'new' owner side values.

This should instead use a scheme where the owner side also updates the neighbour side patch.

Target audience

cht on closed domains. See e.g. https://develop.openfoam.com/Development/openfoam/-/blob/develop/applications/test/multiWorld/solidFoam/solid1_solid2 testcase.

Switch off the kappaLayers, switch to transient, switch on the debug flag for the BC so it prints the heat flux for both sides.

added feature label

Maybe cache the old time values such that the second solid evaluates using exactly the same inputs as the first solid? Would make it even less implicit so would have to be an option. (Note that multi-world mode should be ok - each evaluates at same time)

        if (owner())
        {
            valueFraction() = KDeltaNbr/(KDeltaNbr + KDelta);
            refValue() = TcNbr;
            refGrad() = (qr + qrNbr)/kappa(Tp);
        }
        else
        {
            valueFraction() = KDeltaNbr_0/(KDeltaNbr_0 + KDelta);
            refValue() = TcNbr_0;
            refGrad() = (qr + qrNbr_0)/kappa(Tp);

            KDeltaNbr_0 = KDeltaNbr;
            TcNbr_0 = TcNbr;
            qrNbr_0 = qrNbr;
        }

@Prashant @Sergio

mentioned in issue #2213 (closed)