Convective instability of fluid interfaces

The linear instability of fluid interfaces in two different physical situations has been analyzed. First, the instability of gravitationally unstable layers has been studied to assess the influence of a variety of environmental and physical property effects on expected growth rates. Secondly, the instability of a rapidly-evaporating interface has been studied to assess the role of the 'vapor recoil' mechanism and to identify its regime of applicability.; The linear Rayleigh-Taylor instability analysis for several different models has been performed. The effect due to an upper boundary adjacent to and above a heavier upper layer of varying thickness has been determined for either stress free or no slip boundary conditions. The effect of the thickness of the heavier upper layer on the growth rate has been evaluated and the advantage of using intrinsic scales has been clarified. A three-layer system of a stabilizing, lighter-density layer above a heavy core layer, both overlaying an unbounded medium density layer has assessed the effect of a stable upper surface interface. In addition, the stabilizing effect of a stable, density stratification in the fluid layer underneath a heavier upper layer, interfacial surface tension, and viscosity ratio has been analyzed. The effect of using a creeping flow assumption in the stability formulation reveals that the neglect of the inertial terms can lead to substantial errors in predicting the growth rate. A model was also developed to assess the effect of a continuous, time dependent density distribution. Distributed density profiles yield significantly reduced growth rates compared to sharp interfaces.; Linear hydrodynamic stability analysis was performed for a liquid undergoing steady evaporation at very low pressures. Specific models of interest included configurations where cryogenic liquids could undergo an evaporative process or a propellant densification process. Results were developed for liquids undergoing the 'vapor recoil' effect and applied to the configurations of interest. The results indicated that the configurations of interest were not in the regime for 'vapor recoil' to be operative, and that 'vapor recoil' phase out had occurred prior to nearing the regime of interest.