Water Vapor Compression in the Regime with Dissociation

We consider strong compression of water vapor with the transition from molecular to dissociated (atomic) state within known wide-range equations of state by Nigmatulin and Bolotnova (EOS NB). The cases of quasi-static isentropic compression, shock compression and isentropic compression with the collapse rate of a vapor cavity with constant internal pressure in an inviscid incompressible liquid (Rayleigh problem) are analyzed. Such compression scenarios can be realized, for example, during cavitation bubble collapse in water. In particular, in the course of most part of collapse, the vapor in the central region of the bubble is compressed with the rate of cavity collapse in the Rayleigh problem. Under some conditions, shock waves radially convergent to the bubble center may arise inside the collapsing bubble. Their intensity can grow up to the dissociation processes after their fronts. In EOS NB, the process of dissociation is described by a linear kinetics model with two parameters: characteristic dissociation temperature and relaxation time. In all problems considered, the areas with partial dissociation of the vapor are revealed. The influence of dissociation on the vapor pressure and temperature on the degree of their overestimation/underestimation in simulation without allowing for the dissociation processes is demonsrated. The dependencies of the compression features on the characteristic dissociation temperature and relaxation time are illustrated.