Hydrodynamic Design of Fixed Hydrofoils for Planing Craft

The employment of fixed hydrofoils on existing planing craft is becoming a widely investigated topic, thanks to the opportunity of reducing the total drag forces and the consumptions of main engines, with a positive impact also in terms of air pollutant emissions in the atmosphere. The design of fixed hydrofoils for planing craft is investigated after developing the wing hydrodynamic model, capable of capturing the main forces acting on the craft longitudinal plane. An iterative procedure is developed to solve the nonlinear equilibrium equations and detect the minimum thrust configuration of the fixed hydrofoils at the cruise speed. The new iterative procedure allows investigating the entire design space of fixed hydrofoils and detecting the best configuration for both new and existing craft, with a positive impact in terms of time effort amount and design efficiency. A simplified seakeeping model is also developed to evaluate the impact of fixed hydrofoils on the craft hydrodynamics in a seaway. The USV01 planing craft is assumed as reference for the case study. The wing optimization procedure is employed and the seakeeping analysis in the foil-borne mode is subsequently performed by a set of dedicated codes developed in Matlab. The obtained results are discussed and some suggestions for the reliable design of fixed hydrofoils are provided.