Patch to patch interpolators

Electrochemistry is assumed to occur within the electrolyte. Mole fraction patch fields of oxidants on the air side (cathode) interface and of hydrogen and water on the fuel side (anode) must be therefore interpolated to fields in the electrolyte. The resulting current density is calculated on the fuel side of the anode interface and must be interpolated to the electrolyte side in order to calculate the electrolyte’s volumetric heat source terms. These interpolations are carried out by OpenFOAM patchToPatchInterpolation objects, created in appSrc file createPatchToPatchInterpolation.H.