which behaves as a perfect gas for a gas and an offset perfect gas for a liquid

using point values to construct the in-plane face-gradient

        Hellsten, A.
        "Some Improvements in Menter’s k-omega-SST turbulence model"
        29th AIAA Fluid Dynamics Conference,
        AIAA-98-2554,
        June 1998.

CoBlended: New surfaceInterpolation scheme which blends any two schemes based on the local Courant number