Numerical study of the evolution of unsteady cavitation flow around hydrofoils with leading-edge tubercles

Humpback leading-edge (LE) tubercles are applied to the cavitation control of hydrofoils, and the effect of LE tubercles on hydrofoil cavitation characteristics under different cavitation numbers (sigma) is discussed. The results show that LE tubercles can promote hydrofoil initial cavitation, with cavitation appearing first in the groove. This is because the separation effect of LE tubercles induces flow from peak to trough, resulting in an accelerated flow rate and a local low-pressure area. The quasiperiodic properties of the cloud-cavitation stage are not improved, but LE tubercles considerably reduced hydrofoil cavitation, resulting in a cavitation volume reduction of roughly 16.5%-20.4% and maximum cavitation volume reduction of roughly 10.5%-21.8%. The flow field at the tubercle was analyzed, and it was found that vortex cavitation was induced by the spiral vortex. The pressure pulsation on the hydrofoil is highly related to the cavitating evolution. The dominant frequency of the pressure pulsation increases with the decrease of sigma and is not affected by the LE tubercles. Finally, LE tubercles are observed to facilitate the transformation of laminar flow to turbulent flow, hence increasing wake disturbance and facilitating the disintegration of the wake vortex structure.