An All-Round Design-to-Simulation Approach of a New Z-Drive Escort Tug Class

An industrial-academic collaboration between Rosetti Marino shipyard and University of Genoa presided over a deep theoretical and experimental insight into the maneuvering performances of a new escort tug family. The presented z-drive azimuthal stern drive class is characterized by high intact/damage stability margins, good maneuvering capability, and stable behavior during escort indirect assistance. The project addresses three main research areas: hydrodynamic design of the hull with escort capability, simulation of the escort capabilities in different operational scenario, and development of control logics that will allow autonomous or unmanned operations. The tug design concept is supported by a customized simulation tool that enables the evaluation of the free-sailing and towing maneuvering characteristics for Azimuth Stern Drive (ASD) tugs at high-speed (Escort) and low speed (Harbor Assistance) in a real-time environment. The paper describes the methodological approach adopted for the design and maneuvering characterization of such a class, across some preliminary results. Computational fluid dynamics (CFD) calculations and towing tank tests have been performed onto a prototype tug hull in order to assess the hull design and to infer simulation models able to describe the behavior of a family of vessels. In particular, the propulsion and maneuverability aspects in escort operations are deeply investigated.