  A framework for numerical evaluation of entropy-conservative volume fluxes in
gas flows with internal energies is developed, for use with high-order
discretization methods. The novelty of the approach lies in the ability to use
arbitrary expressions for the internal degrees of freedom of the constituent
gas species. The developed approach is implemented in an open-source
discontinuous Galerkin code for solving hyperbolic equations. Numerical
simulations are carried out for several model 2-D flows and the results are
compared to those obtained with the finite volume-based solver DLR TAU.
