Novel CFD-Based Methods for the Characterization of Ventilated Planing Hulls and Analysis of Air Layer Distribution

Planing hulls are widely used in high-speed marine vessels due to their ability to reduce hydrodynamic resistance by lifting the hull partially out of the water at high speeds. This phenomenon minimizes the wetted surface area, allowing for greater speeds and fuel efficiency. A key technique employed to further reduce drag is the use of air cavity lubrication, where air is introduced beneath the hull to create a cushion between the hull surface and the water. This air cushion decreases friction, enhancing overall performance and lowering energy consumption. The aim of the thesis is to explore the field of Air Cavity Ships by providing new tools for the assessment of the air cushion and for understanding its distribution under the hull in various operating conditions, addressing also the scale influence. Two different hull designs were analysed. The first hull (hull A) served to validate a computational fluid dynamics (CFD) model using experimental data, providing a basis for examining how the air distribution beneath the hull varies with changes in scale. Once the CFD model was validated, the study shifted to a second hull (hull B). Through these analyses, a novel method for visualizing the air distribution beneath the hull was developed, incorporating the local thickness of the air cushion. Two new parameters were introduced to characterize hull ventilation more effectively: the Air Direction Ratio and the Spray Rails Airflow Fraction. In the final phase of the study, a propeller was placed behind the hull to evaluate the impact of its presence on hull ventilation. This analysis led to the calculation of the wake volumetric fraction, further refining the understanding of the interaction between hull ventilation and propulsion.