Ignazio Maria Viola

Hydrodynamics of Hydrofoils

Understanding and controlling the hydrodynamics of hydrofoils plays a central role in the development of high-performance vessels and, more broadly, in the transition toward more efficient and sustainable maritime transport systems. In the context of elite sailing competitions such as the America’s Cup [chatgpt://generic-entity?number=0], the ability to generate lift in a stable manner and with minimal drag is essential to achieve speeds several times greater than the wind speed and to maintain control during aggressive manoeuvres. At the same time, the adoption of hydrofoils in recreational craft and small commercial vessels enables a significant reduction in energy consumption and emissions, due to the decrease in wetted surface and displacement volume. In military applications, the use of such technologies can contribute to reducing the operational footprint, both in terms of surface signature and acoustic emissions, while improving propulsive efficiency.

A fundamental limitation to hydrofoil performance is represented by ventilation phenomena, namely the ingress of air from the free surface along the lifting surface or through tip vortices. This phenomenon substantially alters the pressure distribution, compromising lift generation and inducing instability conditions that may lead to a sudden loss of performance. Ventilation is strongly coupled with free-surface dynamics and depends sensitively on foil geometry, vessel attitude, and operating conditions such as speed and acceleration. Despite its importance, the predictive modelling of ventilation remains an open challenge due to the stochastic and nonlinear nature of the phenomenon.

The thesis project aims to address this problem through an integrated approach combining low-fidelity modelling and high-fidelity numerical simulations. In particular, low-order models based on potential flow formulations will be developed and appropriately extended to account for free-surface and ventilation effects through physically grounded corrections. These models will enable efficient identification of the onset conditions of the phenomenon and exploration of its dependence on key geometric and operational parameters.

In parallel, CFD simulations based on RANS approaches will be carried out with the objective of accurately describing the interaction between liquid and gaseous phases, as well as the formation and evolution of ventilated cavities along the foil. Validation of the results will be performed through systematic comparison with experimental data available in the literature, in order to ensure the reliability of the predictions and to identify the limits of applicability of the different modelling approaches.

The ultimate goal is to develop a comprehensive physical understanding of the mechanisms governing ventilation on hydrofoils and to provide predictive tools for design. This will enable the identification of effective mitigation strategies, through modifications of foil geometry or operating conditions, thereby contributing to the development of more performant, robust, and efficient systems across a wide range of marine and naval applications.