Physical and Theoretical Modeling of Surface-Piercing Hydrofoils for a High-Speed Unmanned Surface Vessel

The objective of this work is to investigate the performance of two pairs of negative dihedral surface-piercing (SP) hydrofoils designed especially for an unmanned surface vessel with a top speed of 120 knots in sea state two. Physical modeling of a 1/6-scaled model of the SP hydrofoil was conducted at the free-surface cavitation tunnel at the Technical University of Berlin (TUB). The SP hydrofoil feature a new type of super-cavitating profile with an annex tapered trailing edge to achieve good efficiencies in foil born conditions (60–120 knots, super-cavitating/ super-ventilated regimes), as well as at take-off speeds (25–40 knots, wetted and/or partial-cavitating regimes). Preliminary results showed interesting anomalies in the trends of the measured forces with respect to the cavitation number and angle of attack for a wide range of inflow speeds. Details of the experimental study are presented along with numerical predictions obtained using finite volume RANSE solver with a volume of fluid technique to allow for a mixture flow with air/vapor and water phases. Explanation of the anomalies in the hydrodynamic performance is given.