Characteristics of non-equilibrium condensing flow in three-dimensional supersonic rectangular nozzles

Abstract

Abstract Fluid flow inside a supersonic nozzle with a rectangular cross-section induces secondary flow due to the shape of the upper wall curvature. The secondary flow forms longitudinal vortices near the wall of the nozzle corner which destabilizes the nozzle outlet flow due to the early transition of the flow from laminar to turbulent. It is known that non-equilibrium homogeneous condensation occurs in a supersonic rectangular nozzle due to the rapid expansion of the condensable fluid with large latent heat such as water vapor. Homogeneous condensation takes place through the formation of water nuclei from its vapor when foreign nuclei are absent in the flow. The irreversibility of the non-equilibrium condensation process causes loss in flow transportation energy in the form of total pressure loss. Although numerous researches have been conducted about the effect of non-equilibrium condensation process in supersonic nozzles, however, the interactions between nozzle shape, non-equilibrium condensation, and longitudinal vortices have not been studied convincingly. Therefore, numerical simulations have been carried out for two supersonic three-dimensional rectangular nozzles in order to understand the effect of nozzle shape and non-equilibrium condensation on the longitudinal vortices at the nozzle corner. Furthermore, total pressure distribution in the nozzle was analysed to understand the effect of degree of supersaturation and expansion rate on the total pressure loss. In this research, characteristics of simulated flow fields including total pressure loss were in good agreement with the published literature.