RAREFACTION SHOCK POSSIBILITY IN A VANDERWAALS-MAXWELL FLUID

The rarefaction shock is found to be impossible practically in an equilibrium van der Waals-Maxwell fluid, in and across all phase regions, although numerical tables seem to indicate the opposite result. The existence of this type of shock depends explicitly on the constant-volume specific heat, as well as the pressure equation of state. The form of specific heat assumed here includes contributions from translation, rotation, and vibration energies of the molecule; Einstein functions are used to represent the latter. In particular, the vaporizing expansion wave in the saturated liquid phase cannot be discontinuous. Metastable states of supersaturation are not considered. Despite the results for this theoretical model, the necessary conditions for the rarefaction shock are found to be satisfied, in principle, for a small region near the critical point of a real two-phase fluid (steam).