Numerical simulation of cavitating flow in liquid Nitrogen through a convergent nozzle

Abstract

This research has dealt with the simulation of liquid nitrogen cavitation inside a convergent nozzle. This is important in cryogenic industrial applications. So in this study, computational fluid dynamics methods have been used for simulating the cavitation phenomenon. The Two-phase model in this research has been a hybrid/mixed model. Also, k- ε turbulence model has been employed in realizable state. For meshing the nozzle geometry, Gambit software has been used, while for numerical simulation, Ansys Fluent software has been employed. For simulation of cavitation, Schnerr and Sauer cavitation model has been utilized. This research has also examined the effect of changing the nozzle outlet diameter and the impact of changing the pressure difference in the inlet and outlet of the nozzle on the cavitation. As a novelty and unlike what would have been expected based on the Bernoulli effect, the results obtained from the simulation showed that the increase/decrease in the nozzle's outlet diameter resulted in an enhanced/diminished extent of cavitation in the nozzle's outlet region. Also, the increase/decrease of the pressure difference in the input and output of the nozzle would lead to a higher/lower extent of cavitation. This research also found that the effect of altering the nozzle's outlet diameter on the extent of cavitation has been far higher than the effect of changing pressure difference in its inlet and outlet. The results also indicated that upon reduction of the nozzle's outlet diameter from the base state (1.02 mm) by 10, 20, 30, 40, and 50 %, the volume fraction of the vapor diminished by 22.23, 43.029, 60.66, 74.73, and 87.16 % respectively. Finally, with the increase in the nozzle's outlet diameter from the base state (1.02 mm) by 10, 20, 30, 40, and 50 %, the volume fraction of the vapor increased by 26.83, 55.27, 84.47, 117.12, and 149.31 % respectively.