Numerical simulation of air ventilation and its suppression on inclined surface-piercing hydrofoils

Abstract

Hydrofoils with significant camber and thickness can be hydrodynamically advantageous over thin low-camber hydrofoils commonly used on boats with surface-piercing hydrofoil systems, especially at lower speeds when a pronounced drag hump is usually present and cavitation is not yet an issue. The main drawback of such high-lift hydrofoils is a danger of being ventilated with air that can easily propagate from the atmosphere along the foil suction side resulting in a drop of the foil lift-drag ratio. The air ventilation is a complex physical process, modeling of which remains a challenging task. In this study, a computational fluid dynamics solver STAR-CCM+ is applied for simulating air ventilation phenomena on surface-piercing hydrofoils. A good agreement is obtained with available test data for relevant configurations. It is also shown that small fences appropriately placed on the inclined surface-piercing hydrofoil can suppress both downward air ventilation and upward water spray, resulting in greater performance of high-lift hydrofoils at moderate Froude numbers.