Description
    Langtry-Menter 4-equation transitional SST model
    based on the k-omega-SST RAS model.

    References:
        Langtry, R. B., & Menter, F. R. (2009).
        Correlation-based transition modeling for unstructured parallelized
        computational fluid dynamics codes.
        AIAA journal, 47(12), 2894-2906.

        Menter, F. R., Langtry, R., & Volker, S. (2006).
        Transition modelling for general purpose CFD codes.
        Flow, turbulence and combustion, 77(1-4), 277-303.

        Langtry, R. B. (2006).
        A correlation-based transition model using local variables for
        unstructured parallelized CFD codes.
        Phd. Thesis, Universität Stuttgart.

Implemented by Henry G. Weller, CFD Direct in collaboration with Florian
Schwertfirm, Kreuzinger und Manhart Turbulenz GmbH.