Suppression of unsteady cavitation around hydrofoils by interaction between passive and re-entry jets

Abstract

Unsteady periodic evolution of cavitation is a common phase transition phenomenon in the field of hydraulic machinery, which easily induces blade surface erosion, deformation, and noise. In this study, a passive jet control method is proposed based on the Clark-Y hydrofoil to suppress the suction surface cavitation without reducing the hydraulic performance. The unsteady cavitation flows around the hydrofoil are numerically investigated using the large eddy simulation and volume of fluid model, and the results are compared with high-speed photography experiments. Introducing the passive jet alters the detailed evolution of cavitation on the suction surface. Accordingly, the sheet cavitation changes from linear growth to three-stage growth, weakening the intensity of cloud cavitation and reducing the time-average cavitation by 37.5%. The passive jet effectively prevents or even eliminates the further development of the re-entrant jet. Moreover, the interaction between the passive and the re-entrant jets causes the rapid collapse of the cavitation. The passive jet accelerated the transition from the sheet vortex to the hairpin vortex, delayed the separation position and time of the boundary layer at the leading edge of the hydrofoil, and enhanced the ability of the hydrofoil to resist velocity separation. The maximum flow resistance coefficient is reduced by 5.80%, maintaining the lift–drag ratio of the hydrofoil.