Nonequilibrium thermodynamics of surfaces captures the energy conversions in a shockwave

Abstract

The local entropy production in a shock wave was analysed in the framework of non-equilibrium thermodynamics (NET) of surfaces. We show that the thermodynamic state variables in the shock front are equal to their equilibrium values, despite lack of global equilibrium in the dense gas. This observation was used to develop a theory for the entropy production in a shock wave using Gibbs' surface excess properties. The theoretical results were compared with a numerical evaluation of the entropy balance for the shock front and confirmed by non-equilibrium molecular dynamics (NEMD) simulations. The NET analysis shows that the dominant contribution to the entropy production is the dissipation of kinetic and compression energy. This opens the door to accurate representations of energy conversions in shock waves.