# OpenFOAM® v3.0+: New Boundary Conditions Functionality

13/01/2016

## Periodic Arbitrary Mesh Interface

A new type of cyclic matching patch, cyclicPeriodicAMI enables conformal mapping of periodic geometries, e.g. wedge geometries.

It uses the transformation provided by the periodic patches to also transform the matching surface which is then handled by the standard cyclicAMI functionality.

A cyclicPeriodicAMI patch relaxes the matching requirement of standard AMI patches. The code will firstly calculate the AMI overlap as normal. If there are non-overlapping regions remaining, the patches will be moved according to the transformation of another pair of (probably cyclic) coupled patches. This will continue until the overlap is complete, or a pre-set number of iterations is reached. If the overlap is not complete, an error is generated, and the program exits.

The algorithm allows for one patch to be an integer multiple of the other. A 20 deg sector could be coupled to a 60deg sector, for example, but not to a 50 deg sector. If the multiple is not an integer, the program will exit with an error.

Example
Combustor: $FOAM_TUTORIALS/combustion/XiDyMFoam/annularCombustorTurbine Source code$FOAM_SRC/meshTools/AMIInterpolation/patches/cyclicPeriodicAMI/cyclicPeriodicAMIPolyPatch/
Related files
$FOAM_SRC/meshTools/AMIInterpolation/AMIInterpolation/AMIInterpolation.[CH]$FOAM_SRC/meshTools/AMIInterpolation/patches/cyclicAMI/cyclicAMIPointPatch/cyclicAMIPointPatch.C

## Humidity

A new boundary condition for temperature has been implemented to thermally couple flow and solid regions when condensation/evaporation is expected on the interface.

The boundary condition is named humidityTemperatureCoupledMixed, and can operate in four modes:

1. inert : thermal inertia is important and no condensation/evaporation takes place;
2. condensation : condensation only;
3. vaporization : evaporation only;
4. condensationAndEvaporation : both condensation and evaporation take place.

The boundary condition assumes no mass flow on the wall i.e. the mass condensed on a patch face remains on that face, and uses a lumped mass model to include thermal inertia effects. The correlation used to calculate the dew temperature based on water vapour.

A scalar transport equation for the carrier specie must be specified via a function object or in the main solver. This transports the vapour phase in the main region. The boundary condition applied to this specie on the coupled wall should be fixedGradient in order to allow condensation or evaporation of the vapour in or out of wall.

Example
Windshield: $FOAM_TUTORIALS/heatTransfer/chtMultiRegionFoam/windshieldCondensation Source code$FOAM_SRC/TurbulenceModels/compressible/turbulentFluidThermoModels/derivedFvPatchFields/humidityTemperatureCoupledMixed