Research on ventilation and supercavitation mechanism of high-speed surface-piercing hydrofoil

Abstract

Flow structures and hydrodynamic performance of high-speed surface-piercing hydrofoils were studied by numerical simulation, with an emphasis on the interaction mechanism between supercavitation and natural ventilation. Compared with the available experimental data, the numerical method could predict the cavitation and ventilation well. The numerical simulation results show that the flow over hydrofoil with blunt trailing edge is more conducive to separating. The semi-ogive hydrofoil was used to explore the influence of angles of attack on ventilation and cavitation. The ventilation rate increases with the increase in the angles of attack. At small attack angles (α = 0° and 2°), the regional ventilated flow is found in supercavitation. The vortex street structures and twin vortices closure mode are formed in the closure region of the supercavity. At moderate attack angles (α = 6° and 10°), the thickness of the undisturbed liquid sheet (δ) becomes thinner and the natural supercavitation transits to fully ventilated supercavitation through the cavitation-induced ventilation, but the ventilation position is different because of Taylor instability. The hydrodynamic coefficients remain relatively stable in natural supercavitation and the lift coefficient reduce to half of the original value when the supercavitation is fully ventilated, which are caused by the pressure changes on the suction and pressure surfaces.