Supercritical density relaxation as a new approach of droplet vaporization

Abstract

The isobaric density relaxation of a cold, slightly supercritical, fluid package in a hotter atmosphere of this same fluid at a near critical pressure is studied in this paper. We solve the Navier–Stokes equations describing the evolution of an initial density inhomogeneity in a supercritical van der Waals fluid. These numerical simulations allow exploring the whole range of surrounding conditions, including the slightly supercritical ones. Strong discrepancies are found from the classical decay of the squared diameter of the droplet observed in clearly subcritical conditions. We present a quasisteady analysis that allows neglecting unsteady terms in the equations that describe the problem, provided that the moving reference frame is well defined. The strong density gradient that follows the “droplet” as well as the time dependant mass flow rate location are considered with a particular attention. The obtained solutions of the equations match with the numerical results and generalize to near critical conditions the classical subcritical quasisteady analysis of droplet vaporization performed in the combustion science field.